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41.
42.
Stream substratum restoration is a widely applied tool to improve spawning habitat quality for salmonid fishes. However, there is a lack of studies which comprehensively assess effects of the restoration on site, as well as on downstream habitats. Our study addressed effects at both locations and compared abiotic (analyses of texture, penetration resistance, oxygen concentration, redox, nitrite, nitrate, ammonium, pH, electric conductivity, temperature) with biotic (depth-specific macroinvertrebrate abundance and diversity, brown trout hatching success) indicators before and after excavation of the substratum in a highly colmated brown trout spawning site. Strong improvements of hyporheic water conditions (increased oxygen supply and redox potential, reduced concentrations of nitrite and ammonium) as well as ~50 % reductions of substratum compaction and fine sediment content were observed 1 day after the restoration measure. Improvements of habitat quality were still detectable 3 months after treatment. Consequently, the hatching success of Salmo trutta eggs increased from 0 % to 77 % after the restoration. Short-term decrease of macroinvertebrate abundance (from 13.1 to 3.9 macroinvertebrates/kg substratum) was observed within the hyporheic zone of the restoration site, but after 3 months, the number of taxa increased from 13 to 22 taxa and abundance reached 17.9 macroinvertebrates/kg. Significantly increased fine sediment deposition was detected within 1 km downstream of the restoration site and may negatively affect these habitats. Trade-offs between positive effects at restored sites and negative effects in downstream habitats need to be considered for a comprehensive evaluation of stream substratum restoration.  相似文献   
43.
The effect of nitrogen (N) stress on the pool system supplying currently assimilated and (re)mobilized N for leaf growth of a grass was explored by dynamic 15N labeling, assessment of total and labeled N import into leaf growth zones, and compartmental analysis of the label import data. Perennial ryegrass (Lolium perenne) plants, grown with low or high levels of N fertilization, were labeled with 15NO3/14NO3 from 2 h to more than 20 d. In both treatments, the tracer time course in N imported into the growth zones fitted a two-pool model (r2 > 0.99). This consisted of a “substrate pool,” which received N from current uptake and supplied the growth zone, and a recycling/mobilizing “store,” which exchanged with the substrate pool. N deficiency halved the leaf elongation rate, decreased N import into the growth zone, lengthened the delay between tracer uptake and its arrival in the growth zone (2.2 h versus 0.9 h), slowed the turnover of the substrate pool (half-life of 3.2 h versus 0.6 h), and increased its size (12.4 μg versus 5.9 μg). The store contained the equivalent of approximately 10 times (low N) and approximately five times (high N) the total daily N import into the growth zone. Its turnover agreed with that of protein turnover. Remarkably, the relative contribution of mobilization to leaf growth was large and similar (approximately 45%) in both treatments. We conclude that turnover and size of the substrate pool are related to the sink strength of the growth zone, whereas the contribution of the store is influenced by partitioning between sinks.This article examines the nitrogen (N) supply system of growing grass leaves, and it investigates how functional and kinetic properties of this system are affected by N stress. The N supply of growing leaves is a dominant target of whole-plant N metabolism. This is primarily related to the high N demand of the photosynthetic apparatus and the related metabolic machinery of new leaves (Evans, 1989; Makino and Osmond, 1991; Grindlay, 1997; Lemaire, 1997; Wright et al., 2004; Johnson et al., 2010; Maire et al., 2012). The N supply system, as defined here, is an integral part of the whole plant: it includes all N compounds that supply leaf growth. Hence, it integrates all events between the uptake of N from the environment (source), intermediate uses in other processes of plant N metabolism, and the eventual delivery to the leaf growth zone (sink; Fig. 1). N that does not ultimately serve leaf growth is not included in this system; all N that serves leaf growth is included, irrespective of its localization in the plant. Conceptually, two distinct sources supply N for leaf growth: N from current uptake and assimilation that is directly transferred to the growing leaf (“directly transferred N”) and N from turnover/redistribution of organic compounds (“mobilized N”).Open in a separate windowFigure 1.Schematic representation of N fluxes in the leaf growth zone and in the N supply system of leaf growth in a grass plant. A, Scheme of a growing leaf, with its growth zone (including zones of cell division, expansion, and maturation) and recently produced tissue (RPT). N import (I; μg h−1) into the growth zone is mostly in the form of amino acids. Inside the growth zone, the nitrogenous substrate is used in new tissue construction. Then, N export (E; μg h−1) is in the form of newly formed, fully expanded nitrogenous tissue (tissue-bound export with RPT) and is calculated as leaf elongation rate (LER; mm h−1) times the lineal density of N in RPT (ρ; μg mm−1): E = LER × ρ (Lattanzi et al., 2004). In a physiological steady state, import equals export (I = E) and the N content of the growth zone (G; μg [not shown]) is constant. Labeled N import into the growth zone (Ilab) commences shortly after labeling of the nutrient solution with 15N. The labeled N content of the growth zone (Glab; μg) increases over time (dGlab/dt) until it eventually reaches isotopic saturation (Fig. 2B). Similarly, the lineal density of labeled N in RPTlab) increases until it approaches ρ. At any time, the export of labeled N in RPT (Elab) equals the concurrent ρlab × LER. The import of labeled N is obtained as Ilab = Elab + dGlab/dt (Lattanzi et al., 2005) and considers the increasing label content in the growth zone during labeling. The fraction of labeled N in the import flux (flab I) is calculated as flab I = Ilab/I. The time course of flab I (Fig. 3) reflects the kinetic properties of the N supply system of leaf growth (C). B, Scheme of a vegetative grass plant (reduced to a rooted tiller with three leaves) with leaf growth zone. N import into the growth zone (I) originates from (1) N taken up from the nutrient solution that is transferred directly to the growth zone following assimilation (directly transferred N) and (2) N derived from turnover/redistribution of stores (mobilized N). The store potentially includes proteins in all mature and senescing tissue in the shoot and root of the entire plant. As xylem, phloem, and associated transfer cells/tissue provide for a vascular network that connects all parts of the plant, the mobilized N may principally originate from any plant tissue that exhibits N turnover/mobilization. The fraction of total N uptake that is allocated to the N supply system of the growth zone equals U (see model in C). The fraction of total mobilized N allocated to the growth zone equals M (see model in C). C, Compartmental model of the source-sink system supplying N to the leaf growth zone, as shown by Lattanzi et al. (2005) and used here. Newly absorbed N (U; μg h−1) enters a substrate pool (Q1); from there, the N is either imported directly into the growth zone (I) or exchanged with a store (Q2). Q1 integrates the steps of transport and assimilation that precede the translocation to the growth zone. Q2 includes all proteins that supply N for leaf growth during their turnover and mobilization. The parameters of the model, including the (relative) size and turnover of pools Q1 and Q2, the deposition into the store (D; μg h−1), and the mobilization from the store (M; μg h−1), and the contribution of direct transfer relative to mobilization to the N supply of the growth zone are obtained by fitting the compartmental model to the flab I data (A) obtained in dynamic 15N labeling experiments (for details, see “Materials and Methods”). During physiological steady state, the sizes of Q1 and Q2 are constant, I = U, and M = D. [See online article for color version of this figure.]Amino acids are the predominant form in which N is supplied for leaf growth in grasses, and incorporation in new leaf tissue occurs mainly in the leaf growth zone (Gastal and Nelson, 1994; Amiard et al., 2004). This is a heterotrophic piece of tissue that includes the zones of cell division and elongation, is located at the base of the leaf, and is encircled by the sheath of the next older leaf (Volenec and Nelson, 1981; MacAdam et al., 1989; Schnyder et al., 1990; Kavanová et al., 2008). As most N is taken up in the form of nitrate but supplied to the growth zone in the form of amino acids, the path of directly transferred N includes a series of metabolic and transport steps. These include transfer to and loading into the xylem, xylem transport and unloading, reduction and ammonium assimilation, cycling through photorespiratory N pools, amino acid synthesis, loading into the phloem, and transport to the growth zone (Hirel and Lea, 2001; Novitskaya et al., 2002; Stitt et al., 2002; Lalonde et al., 2003; Dechorgnat et al., 2011). The time taken to pass through this sequence is unknown at present, as is the effect of N deficiency on that time. Also, it is not known how much N is contained in, and moving through, the different compartments that supply leaf growth with currently assimilated N.At the level of mature organs, mainly leaves, there is considerable knowledge about N turnover and redistribution. Much less is known about the fate of the mobilized N and its actual use in sink tissues like the leaf growth zone. The processes in mature organs are associated with the maintenance metabolism of proteins, organ senescence, and adjustments in leaf protein levels to decreasing irradiance inside growing canopies when leaves become shaded by overtopping newer ones (Evans, 1993; Vierstra, 1993; Hikosaka et al., 1994; Anten et al., 1995; Hirel et al., 2007; Jansson and Thomas, 2008; Moreau et al., 2012). N mobilization in shaded leaves supports the optimization of photosynthetic N use efficiency at plant and canopy scale (Field, 1983; Evans, 1993; Anten et al., 1995), it reduces the respiratory burden of protein maintenance costs (Dewar et al., 1998; Amthor, 2000; Cannell and Thornley, 2000), and it provides a mechanism for the conservation of the most frequently growth-limiting nutrient (Aerts, 1996). Mobilization of N involves protein turnover and net degradation (Huffaker and Peterson, 1974), redistribution in the form of amino acids (Simpson and Dalling, 1981; Simpson et al., 1983; Hörtensteiner and Feller, 2002), and (at least) some of the mobilized N is supplied to new leaf growth (Lattanzi et al., 2005).N fertilizer supply has multiple direct and indirect effects on plant N metabolism (Stitt et al., 2002; Schlüter et al., 2012). In particular, it modifies the N content of newly produced leaves, leaf longevity/senescence, and the dynamics of light distribution inside expanding canopies (Evans, 1983, 1989; Lötscher et al., 2003; Moreau et al., 2012). Thus, N fertilization influences the availability of recyclable N. At the same time, it augments the availability of directly transferable N to leaf growth. The net effect of these factors on the importance of mobilized versus directly transferred N substrate for leaf growth is not known. Also, it is unknown how N fertilization influences the functional characteristics of the N supply system, such as the size and turnover of its component pools.The assessment of the importance of directly transferred versus mobilized N for leaf growth requires studies at the sink end of the system (i.e. investigations of the N import flux into the leaf growth zone). Directly transferred N and mobilized N can be distinguished on the basis of their residence time in the plant, the time between uptake from the environment and import into the leaf growth zone: direct transfer involves a short residence time (fast transfer), whereas mobilized N resides much longer in the plant before it is delivered to the growth zone (slow transfer; De Visser et al., 1997; Lattanzi et al., 2005). Such studies require dynamic labeling of the N taken up by the plant (Schnyder and de Visser, 1999) and monitoring of the rate and isotopic composition/label content of N import into the leaf growth zone (Lattanzi et al., 2005). For grass plants in a physiological steady state, N import and the isotopic composition of the imported N are calculated from the leaf elongation rate and the lineal density of N in newly formed tissue (Fig. 1A; Lattanzi et al., 2004) and the change of tracer content in the leaf growth zone and recently produced leaf tissue over time (Lattanzi et al., 2005). Such data reveal the temporal change of the fraction of labeled N in the N import flux (flab I), which then can be used to characterize the N supply system of leaf growth via compartmental modeling. So far, there is only one study that has partially characterized this system (Lattanzi et al., 2005): this work was conducted with a C3 grass, perennial ryegrass (Lolium perenne), and a C4 grass, Paspalum dilatatum, growing in mixed stands and indicated that two interconnected N pools supplied the leaf growth zone in both species: a “substrate pool” (Q1), which provided a direct route for newly absorbed and assimilated N import into the leaf growth zone (directly transferred N), and a mobilizing “store” (Q2), which supplied N to the leaf growth zone via the substrate pool (Fig. 1C). The relative contribution of mobilization from the store was least important in the fast-growing, dominant individuals and most important in subordinate, shaded individuals. That work did not address the role of N deficiency, and the limited short-term resolution of the study (labeling intervals of 24 h or greater) precluded an analysis of the fast-moving parts of the system.Accordingly, this work addresses the following questions. How does N deficiency influence the substrate supply system of the leaf growth sink in terms of the number, size, and turnover (half-life) of its kinetically distinct pools? How does N deficiency affect the relationship between directly transferred and mobilized N for leaf growth? And what additional insight on the compartmental structure of the supply system is obtained when the short-term resolution of the analysis is increased by 1 order of magnitude? The work was performed with vegetative plants of perennial ryegrass grown in constant conditions with either a low (1.0 mm; termed low N) or high (7.5 mm; high N) nitrate concentration in the nutrient solution. In both treatments, a large number of plants were dynamically labeled with 15N over a wide range of time intervals (2 h to more than 20 d). The import of total N and 15N tracer into growth zones was estimated at the end of each labeling interval. Tracer data were analyzed with compartmental models following principles detailed by Lattanzi et al. (2005, 2012) and Lehmeier et al. (2008) to address the specific questions. Previous articles reported on root and shoot respiration (Lehmeier et al., 2010) and cell division and expansion in leaf growth zones (Kavanová et al., 2008) in the same experiment.  相似文献   
44.

Background

The incidence of several adverse pregnancy outcomes including fetal growth restriction are higher in pregnancies where the fetus is male, leading to suggestions that placental insufficiency is more common in these fetuses. Placental insufficiency associated with fetal growth restriction may be identified by multi-vessel Doppler assessment, but little evidence exists regarding sex specific differences in these Doppler indices or placental function. This study aims to investigate sex specific differences in fetal and placental perfusion and to correlate these changes with intra-partum outcome.

Methods and Findings

This is a prospective cohort study. We measured Doppler indices of 388 term pregnancies immediately prior to the onset of active labour (≤3 cm dilatation). Fetal sex was unknown at the time of the ultrasound assessment. Information from the ultrasound scan was not made available to clinical staff. Case notes and electronic records were reviewed following delivery. We report significantly lower Middle Cerebral artery pulsatility index (1.34 vs. 1.43, p = 0.004), Middle Cerebral artery peak velocity (53.47 cm/s vs. 58.10 cm/s, p = <0.001), and Umbilical venous flow/kg (56 ml/min/kg vs. 61 ml/min/kg, p = 0.02) in male fetuses. These differences however, were not associated with significant differences in intra-partum outcome.

Conclusion

Sex specific differences in feto-placental perfusion indices exist. Whilst the physiological relevance of these is currently unknown, the identification of these differences adds to our knowledge of the physiology of male and female fetuses in utero. A number of disease processes have now been shown to have an association with changes in fetal haemodynamics in-utero, as well as having a sex bias, making further investigation of the sex specific differences present during fetal life important. Whilst the clinical application of these findings is currently limited, the results from this study do provide further insight into the gender specific circulatory differences present in the fetal period.  相似文献   
45.
Grace  D. C.  Diall  O.  Saville  K.  Warboys  D.  Ward  P.  Wild  I.  Perry  B. D. 《EcoHealth》2022,19(3):342-353
EcoHealth - Small farmers produce most food in low- and middle-income countries and most small farmers rely on directly or indirectly working equids (WE). The lack of methods and metrics for...  相似文献   
46.
BackgroundWomen with obesity and infertility are counseled to lose weight prior to conception and infertility treatment to improve pregnancy rates and birth outcomes, although confirmatory evidence from randomized trials is lacking. We assessed whether a preconception intensive lifestyle intervention with acute weight loss is superior to a weight neutral intervention at achieving a healthy live birth.Methods and findingsIn this open-label, randomized controlled study (FIT-PLESE), 379 women with obesity (BMI ≥ 30 kg/m2) and unexplained infertility were randomly assigned in a 1:1 ratio to 2 preconception lifestyle modification groups lasting 16 weeks, between July 2015 and July 2018 (final follow-up September 2019) followed by infertility therapy. The primary outcome was the healthy live birth (term infant of normal weight without major anomalies) incidence. This was conducted at 9 academic health centers across the United States. The intensive group underwent increased physical activity and weight loss (target 7%) through meal replacements and medication (Orlistat) compared to a standard group with increased physical activity alone without weight loss. This was followed by standardized empiric infertility treatment consisting of 3 cycles of ovarian stimulation/intrauterine insemination. Outcomes of any resulting pregnancy were tracked. Among 191 women randomized to standard lifestyle group, 40 dropped out of the study before conception; among 188 women randomized to intensive lifestyle group, 31 dropped out of the study before conception. All the randomized women were included in the intent-to-treat analysis for primary outcome of a healthy live birth. There were no significant differences in the incidence of healthy live births [standard 29/191(15.2%), intensive 23/188(12.2%), rate ratio 0.81 (0.48 to 1.34), P = 0.40]. Intensive had significant weight loss compared to standard (−6.6 ± 5.4% versus −0.3 ± 3.2%, P < 0.001). There were improvements in metabolic health, including a marked decrease in incidence of the metabolic syndrome (baseline to 16 weeks: standard: 53.6% to 49.4%, intensive 52.8% to 32.2%, P = 0.003). Gastrointestinal side effects were significantly more common in intensive. There was a higher, but nonsignificant, first trimester pregnancy loss in the intensive group (33.3% versus 23.7% in standard, 95% rate ratio 1.40, 95% confidence interval [CI]: 0.79 to 2.50). The main limitations of the study are the limited power of the study to detect rare complications and the design difficulty in finding an adequate time matched control intervention, as the standard exercise intervention may have potentially been helpful or harmful.ConclusionsA preconception intensive lifestyle intervention for weight loss did not improve fertility or birth outcomes compared to an exercise intervention without targeted weight loss. Improvement in metabolic health may not translate into improved female fecundity.Trial registrationClinicalTrials.gov NCT02432209.

Richard Legro and colleagues investigate the impact of a preconception weight loss intervention on healthy live birth rates in women with obesity and unexplained infertility.  相似文献   
47.
The biologically active form of the human immunodeficiency virus type 1 (HIV-1) envelope (Env) glycoprotein is oligomeric. We previously described a soluble HIV-1 IIIB Env protein, gp140, with a stable oligomeric structure composed of uncleaved gp120 linked to the ectodomain of gp41 (P. L. Earl, C. C. Broder, D. Long, S. A. Lee, J. Peterson, S. Chakrabarti, R. W. Doms, and B. Moss, J. Virol. 68:3015-3026, 1994). Here we compared the antibody responses of rabbits to gp120 and gp140 that had been produced and purified in an identical manner. The gp140 antisera exhibited enhanced cross-reactivity with heterologous Env proteins as well as greater neutralization of HIV-1 compared to the gp120 antisera. To examine both immunogenicity and protective efficacy, we immunized rhesus macaques with oligomeric gp140. Strong neutralizing antibodies against a homologous virus and modest neutralization of heterologous laboratory-adapted isolates were elicited. No neutralization of primary isolates was observed. However, a substantial fraction of the neutralizing activity could not be blocked by a V3 loop peptide. After intravenous challenge with simian-HIV virus SHIV-HXB2, three of the four vaccinated macaques exhibited no evidence of virus replication.  相似文献   
48.
BACKGROUND: The mammalian signal recognition particle (SRP) is an essential cytoplasmic ribonucleoprotein complex involved in targeting signal-peptide-containing proteins to the endoplasmic reticulum. Assembly of the SRP requires protein SRP19 to bind first to helix 6 of the SRP RNA before the signal-peptide-recognizing protein, SRP54, can bind to helix 8 of the RNA. Helix 6 is closed by a GGAG tetraloop, which has been shown to form part of the SRP19-binding site. RESULTS: The high-resolution (2.0 A) structure of a fragment of human SRP RNA comprising 29 nucleotides of helix 6 has been determined using the multiple anomalous dispersion (MAD) method and bromine-labelled RNA. In the crystal the molecule forms 28-mer duplexes rather than the native monomeric hairpin structure, although two chemically equivalent 11 base pair stretches of the duplex represent the presumed native structure. The duplex has highly distorted A-RNA geometry caused by the occurrence of several non-Watson-Crick base pairs. These include a 5'-GGAG-3'/3'-GAGG-5' purine bulge (which replaces the tetraloop) and a 5'-AC-3'/3'-CA-5' tandem mismatch that, depending on the protonation state of the adenine bases, adopts a different conformation in the two native-like parts of the structure. The structure also shows the 2'3'-cyclic phosphate reaction product of the hammerhead ribozyme cleavage reaction. CONCLUSIONS: The 29-mer RNA is the first RNA structure of the human SRP and provides some insight into the binding mode of SRP19. The observed strong irregularities of the RNA helix make the major groove wide enough and flat enough to possibly accommodate an alpha helix of SRP19. The variety of non-canonical base pairs observed enlarges the limited repertoire of irregular RNA folds known to date and the observed conformation of the 2'3'-cyclic phosphate containing Ade29 is consistent with the current understanding of the hammerhead ribozyme reaction mechanism.  相似文献   
49.
MHC-I (Ld)-restricted, S28-39-specific CTL responses are efficiently primed in H-2d BALB/c mice injected with low doses of native hepatitis B surface Ag (HBsAg) lipoprotein particles without adjuvants. Priming of this CTL response by exogenous HBsAg required CD4+ T cell "help" and IL-12: this CTL response could be neither induced in mice depleted of CD4+ T cells by in vivo Ab treatment, nor in (CD4+ T cell-competent or CD4+ T cell-depleted) IL-12-unresponsive STAT4-/- knockout BALB/c mice. Codelivery of oligonucleotides (ODN) with immunostimulating CpG sequences (ISS) with exogenous HBsAg reconstituted the CTL response to exogenous HBsAg in CD4+ T cell-depleted normal mice and in CD4+ T cell-competent and CD4+ T cell-depleted STAT4-/- BALB/c mice. Injection (by different routes) of "naked" pCI/S plasmid DNA encoding HBsAg into IL-12-responsive or -unresponsive BALB/c mice efficiently primed the MHC-I-restricted, HBsAg-specific CTL response. CTL priming was not detectable when CD4+ T cell-depleted animals were subjected to genetic immunization. In vivo priming of the well-characterized CD8+ CTL response to HBsAg in "high responder" BALB/c mice either by exogenous surface lipoprotein particles or by DNA vaccination is thus CD4+ T cell dependent. CTL priming by exogenous HBsAg, but not by genetic immunization, is IL-12 dependent. The dependence of CTL priming by exogenous HBsAg on CD4+ T cells can be overcome by codelivering ODN with ISS motifs, and this "adjuvants effect" operates efficiently in IL-12-unresponsive mice. The data characterize a feature of the adjuvant effect of ISS-containing ODN on CTL priming that may be of major interest for the design of CTL-stimulating vaccines with efficacy in immunodeficiency conditions.  相似文献   
50.
CD46 acts as a cellular receptor for vaccine strains of measles virus (MV). The MV/CD46 interaction-mediated by the MV attachment glycoprotein, the hemagglutinin (H)-not only facilitates infection but also induces CD46 downregulation. A conflict of opinion exists as to whether a single MVH binding site on CD46, or two separate sites, facilitates the two phenomena. To investigate this conundrum we first tested and compared a panel of CD46-specific monoclonal antibodies (mAbs) for their capacity to block both processes. One (mAb 13/42) abrogated both MV fusion and CD46 downregulation. Mutation of an amino acid (arg59 in the SCR1 of CD46) essential for the epitope of mAb 13/42 resulted in the abrogation of both CD46 downregulation and viral fusion. This strongly suggests that the same MV binding site on CD46 is responsible for both CD46 downregulation and MV infection.  相似文献   
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