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101.
Roque d’orbcastel Emmanuelle Bettarel Yvan Dellinger Marion Sadoul Bastien Bouvier Thierry Amandé Justin Monin Dagorn Laurent Geffroy Benjamin 《Environmental Biology of Fishes》2021,104(6):725-732
Environmental Biology of Fishes - Cortisol is recognized as a physiological indicator of stress in fish. However, this hormone is typically measured in plasma samples. In this study, cortisol... 相似文献
102.
Jacques Simard Rocio Sanchez Francine Durocher Eric Rhaume Carl Turgeon Yvan Labrie Van Luu-The Farida Mebarki Yves Morel Yvan de Launoit Fernand Labrie 《The Journal of steroid biochemistry and molecular biology》1995,55(5-6):489-505
The isoenzymes of the 3β-hydroxysteroid dehydrogenase/5-ene-4-ene-isomerase (3β-HSD) gene family catalyse the transformation of all 5-ene-3β-hydroxysteroids into the corresponding 4-ene-3-keto-steroids and are responsible for the interconversion of 3β-hydroxy- and 3-keto-5-androstane steroids. The two human 3β-HSD genes and the three related pseudogenes are located on the chromosome 1p13.1 region, close to the centromeric marker D1Z5. The 3β-HSD isoenzymes prefer NAD+ to NADP+ as cofactor with the exception of the rat liver type III and mouse kidney type IV, which both prefer NADPH as cofactor for their specific 3-ketosteroid reductase activity due to the presence of Tyr36 in the rat type III and of Phe36 in mouse type IV enzymes instead of Asp36 found in other 3β-HSD isoenzymes. The rat types I and IV, bovine and guinea pig 3β-HSD proteins possess an intrinsic 17β-HSD activity psecific to 5-androstane 17β-ol steroids, thus suggesting that such “secondary” activity is specifically responsible for controlling the bioavailability of the active androgen DHT. To elucidate the molecular basis of classical form of 3β-HSD deficiency, the structures of the types I and II 3β-HSD genes in 12 male pseudohermaphrodite 3β-HSD deficient patients as well as in four female patients were analyzed. The 14 different point mutations characterized were all detected in the type II 3β-HSD gene, which is the gene predominantly expressed in the adrenals and gonads, while no mutation was detected in the type I 3β-HSD gene predominantly expressed in the placenta and peripheral tissues. The mutant type II 3β-HSD enzymes carrying mutations detected in patients affected by the salt-losing form exhibit no detectable activity in intact transfected cells, at the exception of L108W and P186L proteins, which have some residual activity (1%). Mutations found in nonsalt-loser patients have some residual activity ranging from 1 to 10% compared to the wild-type enzyme. Characterization of mutant proteins provides unique information on the structure-function relationships of the 3β-HSD superfamily. 相似文献
103.
Aurélie Thébault Jean‐Christophe Clément Sébastien Ibanez Julien Roy Roberto A. Geremia Cecilia A. Pérez Alexandre Buttler Yvan Estienne Sandra Lavorel 《Oikos》2014,123(6):729-740
Tree growth limitation at treeline has mainly been studied in terms of carbon limitation while effects and mechanisms of potential nitrogen (N) limitation are barely known, especially in the southern hemisphere. We investigated how soil abiotic properties and microbial community structure and composition change from lower to upper sites within three vegetation belts (Nothofagus betuloides and N. pumilio forests, and alpine vegetation) across an elevation gradient (from 0 to 650 m a.s.l.) in Cordillera Darwin, southern Patagonia. Increasing elevation was associated with a decrease in soil N‐NH4+ availability within the N. pumilio and the alpine vegetation belt. Within the alpine vegetation belt, a concurrent increase in the soil C:N ratio was associated with a shift from bacterial‐dominated in lower alpine sites to fungal‐dominated microbial communities in upper alpine sites. Lower forested belts (N. betuloides, N. pumilio) exhibited more complex patterns both in terms of soil properties and microbial communities. Overall, our results concur with recent findings from high‐latitude and altitude ecosystems showing decreased nutrient availability with elevation, leading to fungal‐dominated microbial communities. We suggest that growth limitation at treeline may result, in addition to proximal climatic parameters, from a competition between trees and soil microbial communities for limited soil inorganic N. At higher elevation, soil microbial communities could have comparably greater capacities to uptake soil N than trees, and the shift towards a fungal‐dominated community would favour N immobilization over N mineralization. Though evidences of altered nutrient dynamics in tree and alpine plant tissue with increasing altitude remain needed, we contend that the measured residual low amount of inorganic N available for trees in the soil could participate to the establishment limitation. Finally, our results suggest that responses of soil microbial communities to elevation could be influenced by functional properties of forest communities for instance through variations in litter quality. 相似文献
104.
Lisette Van Hove Kim Lecomte Jana Roels Niels Vandamme HannaKaisa Vikkula Isabelle Hoorens Katia Ongenae Tino Hochepied Giacomo Donati Yvan Saeys Sven R Quist Fiona M Watt Geert van Loo Esther Hoste 《EMBO reports》2021,22(5)
Fibroblasts are a major component of the microenvironment of most solid tumours. Recent research elucidated a large heterogeneity and plasticity of activated fibroblasts, indicating that their role in cancer initiation, growth and metastasis is complex and context‐dependent. Here, we performed genome‐wide expression analysis comparing fibroblasts in normal, inflammatory and tumour‐associated skin. Cancer‐associated fibroblasts (CAFs) exhibit a fibrotic gene signature in wound‐induced tumours, demonstrating persistent extracellular matrix (ECM) remodelling within these tumours. A top upregulated gene in mouse CAFs encodes for PRSS35, a protease capable of collagen remodelling. In human skin, we observed PRSS35 expression uniquely in the stroma of high‐grade squamous cell carcinomas. Ablation of PRSS35 in mouse models of wound‐ or chemically‐induced tumorigenesis resulted in aberrant collagen composition in the ECM and increased tumour incidence. Our results indicate that fibrotic enzymes expressed by CAFs can regulate squamous tumour initiation by remodelling the ECM. 相似文献
105.
Nampally Sreenivasachary Heiko Kroth Pascal Benderitter Anne Hamel Yvan Varisco David T. Hickman Wolfgang Froestl Andrea Pfeifer Andreas Muhs 《Bioorganic & medicinal chemistry letters》2017,27(6):1405-1411
The aggregation of amyloid-β peptides into cytotoxic oligomeric and fibrillary aggregates is believed to be one of the major pathological events in Alzheimer disease. Here we report the design and synthesis of a novel series of indole and 7-azaindole derivatives containing, nitrile, piperidine and N-methyl-piperidine substituents at the 3-position to prevent the pathological self-assembly of amyloid-β. We have further demonstrated that substitution of the azaindole and indole derivatives at the 3 positions is required to obtain compounds with improved physicochemical properties to allow brain penetration. 相似文献
106.
Lebeau A Reverchon S Gaubert S Kraepiel Y Simond-Côte E Nasser W Van Gijsegem F 《Environmental microbiology》2008,10(3):545-559
Pathogenicity of the phytopathogenic enterobacterium Erwinia chrysanthemi , the causal agent of soft rot disease on many plants, is a complex process involving several factors whose production is regulated by a complex, intertwined regulatory network. In this work we characterized the GacA regulator, member of the GacS–GacA two-component system, as a global regulator which is required for disease expression but not for bacterial multiplication in planta during the first stages of the plant infection. GacA was shown to control the expression of plant cell wall-degrading enzymes and hrp genes in vitro . Analysis of virulence gene expression during infection of Arabidopsis thaliana revealed a coordinated expression of these virulence genes at 12 h post infection and showed that GacA is required for the appropriate production of virulence factors in planta . GacA might partly act by negatively controlling the expression of the pecT gene encoding the global repressor PecT, indicating a hierarchy in the pathways involved in the E. chrysanthemi regulatory network. 相似文献
107.
108.
The potential health risks of radiofrequency electromagnetic fields (RF EMFs) emitted by mobile phones are currently of considerable public interest. The present study investigated the effect of exposure to 900 MHz GSM radiofrequency radiation on steroid (cortisol and testosterone) and pituitary (thyroid-stimulating hormone, growth hormone, prolactin and adrenocorticotropin) hormone levels in 20 healthy male volunteers. Each subject was exposed to RF EMFs through the use of a cellular phone for 2 h/day, 5 days/ week, for 4 weeks. Blood samples were collected hourly during the night and every 3 h during the day. Four sampling sessions were performed at 15-day intervals: before the beginning of the exposure period, at the middle and the end of the exposure period, and 15 days later. Parameters evaluated included the maximum serum concentration, the time of this maximum, and the area under the curve for hormone circadian patterns. Each individual's pre-exposure hormone concentration was used as his control. All hormone concentrations remained within normal physiological ranges. The circadian profiles of prolactin, thyroid-stimulating hormone, adrenocorticotropin and testosterone were not disrupted by RF EMFs emitted by mobile phones. For growth hormone and cortisol, there were significant decreases of about 28% and 12%, respectively, in the maximum levels when comparing the 2-week (for growth hormone and cortisol) and 4-week (for growth hormone) exposure periods to the pre-exposure period, but no difference persisted in the postexposure period. Our data show that the 900 MHz EMF exposure, at least under our experimental conditions, does not appear to affect endocrine functions in men. 相似文献
109.
Steffen Harzsch Carsten H. G. Müller Verena Rieger Yvan Perez Silvia Sintoni Christian Sardet Bill Hansson 《Zoomorphology》2009,128(1):53-73
The enigmatic arrow worms (Chaetognatha) are marine carnivores and among the most abundant planktonic organisms. Their phylogenetic
position has been heavily debated for a long time. Most recent molecular studies still provide a diverging picture and suggest
arrow worms to be some kind of basal protostomes. In an effort to understand the organization of the nervous system in this
clade for a broad comparison with other Metazoa we analysed the ultrastructure of the ventral nerve centre in Spadella cephaloptera by transmission electron microscopy. We were able to identify six different types of neurons in the bilateral somata clusters
by means of the cytoplasmic composition (regarding the structure of the neurite and soma including the shape and eu-/heterochromatin
ratio within the nucleus) as well as the size and position of these neurons. Furthermore, our study provides new insights
into the neuropil composition of the ventral nerve centre and several other fine structural features. Our second goal was
to examine if individually identifiable neurons are present in the ventral nerve centres of four chaetognath species, Sagitta setosa, Sagitta enflata, Pterosagitta draco, and Spadella cephaloptera. For that purpose, we processed whole mount specimens of these species for immunolocalization of RFamide-related neuropeptides
and analysed them with confocal laser-scanning microscopy. Our experiments provide evidence for the interspecific homology
of individual neurons in the ventral nerve centres of these four chaetognath species suggesting that the potential to generate
serially arranged neurons with individual identities is part of their ground pattern. 相似文献
110.
Manuel Porcar Anne-Marie Grenier Brian Federici Yvan Rahbé 《Applied and environmental microbiology》2009,75(14):4897-4900
Four Bacillus thuringiensis δ-endotoxins, Cry3A, Cry4Aa, Cry11Aa, and Cyt1Aa, were found to exhibit low to moderate toxicity on the pea aphid, Acyrthosiphon pisum, in terms both of mortality and growth rate. Cry1Ab was essentially nontoxic except at high rates. To demonstrate these effects, we had to use exhaustive buffer-based controls.Many species of aphids are important sucking-insect pests that feed on plant vascular fluids. Their feeding mechanism makes these insects excellent vectors for many plant pathogens, especially viruses, yet less amenable to standard, nonsystemic chemical control by insecticides. Minor effects on the survival and fecundity of aphids reared on Bacillus thuringiensis (Bt) crops have been noted in some studies but not in others (1, 3, 6). However, the sensitivity of aphids to Bt toxins, or the lack thereof, has not been previously tested through artificial-diet bioassays with exhaustive buffer-based controls.Bt δ-endotoxins Cyt1A, Cry4A/Cry4B, and Cry11, obtained from three recombinant strains of B. thuringiensis subsp. israelensis, as well as Cry1Ab and Cry3A, obtained from recombinant Escherichia coli, were purified by ultracentrifugation in a discontinuous sucrose gradient as described previously (9). Cry proteins were solubilized in solubilization buffer (50 mM Na2CO3, 100 mM NaCl, pH 10) with dithiothreitol (10 mM) added before use. Cyt1A was first solubilized on 10 mM Na2CO3 (pH 11) buffer and then neutralized at pH 7.5 to 8 with 10 μl HCl (1 N). Both solubilized and trypsin-digested samples (1:30 over toxin weight) were used at different concentrations (32, 125, and 500 μg/ml; trypsin-activated toxin concentrations were calculated on the basis of the preactivation concentrations of the protoxins) to supplement the AP3 aphid synthetic diet (7) used to feed Acyrthosiphon pisum (LL01 green clone). Ampicillin (100 μg/ml), an ineffective antibiotic for A. pisum or its obligate symbiont Buchnera, was added to the medium to avoid bacterial growth. For each concentration, 30 nymphs (10 nymphs/box and three repetitions) were bioassayed at 20°C and under a 16:8 (light-dark) photoperiod. Survival time was calculated from aphid deposition on the test diet (day 0). Mortality was surveyed daily, and body weights of survivors were noted at day 7. ST50 (median survival time after challenge) was calculated by using an actuarial survival analysis (Statview) with censoring values of survivors at the end of the experiments. The approximate concentrations resulting in a 50% decrease in mean body weight (IC50) and killing of 50% of the insects tested (LC50) were calculated at the end of the experiments from the growth reduction and mortality data, respectively, derived with the three doses by using Statview and the censoring values of survivors.All of the Cry δ-endotoxins tested were lethal to A. pisum and retarded the growth of survivors (Fig. (Fig.11 and and2).2). Mortalities ranged from only 25% (Cry1Ab) to 100% (Cry4 and Cry11) after 3 to 6 days of exposure to 500 μg/ml of solubilized protein (Fig. (Fig.1).1). When significant mortalities were achieved (Cry3A, Cry4, and Cry11), trypsin activation enhanced toxicity. Activation of Cry4 at the intermediate concentration tested (125 μg/ml) resulted in a twofold increase in mortality (Fig. (Fig.1D).1D). ST50s were calculated for both solubilized protoxins and activated Cry3A, Cry4, and Cry11. The ST50s (at 500 μg/ml) ranged from 1.8 ± 0.14 days for solubilized Cry4 and Cry11 to 3.7 ± 1.2 days for trypsin-activated Cry3A (Table (Table1).1). Control aphids fed buffer all survived for >8 days. The LC50 of Cry1Ab was not calculated, since mortality associated with Cry1Ab reached a plateau at 500 μg/ml. The LC50 of Cry4 was estimated to be 70 to 100 μg/ml (data not shown).Open in a separate windowFIG. 1.Mortality assays over the nymphal life stage of the pea aphid, A. pisum, upon ingestion of artificial diets containing purified Bt toxins after either solubilization (open symbols) or solubilization and trypsin activation (solid symbols). The toxins used were Cry1Ab (circles), Cry3A (squares), a mixture of Cry4A and Cry4B (diamonds), and Cry11A (triangles). The soluble-toxin doses used were low at 32 μg/ml (blue), intermediate at 125 μg/ml (violet), and high at 500 μg/ml (red). Assays were carried out with 30 initial neonate insects in three batches of 10 individuals.Open in a separate windowFIG. 2.Growth inhibition assays with purified Bt toxins Cry3A, Cry4, and Cry 11 (A) and Cry1Ab and Cyt1A (B) on the pea aphid, A. pisum. Toxins were added to the diet either after solubilization (open symbols) or after solubilization and trypsin activation (solid symbols). Error bars show the standard errors (SE) of individual weights at day 7 of experiments, standardized by the control group mean weight (toxin dose, 0; initial number, 30). Color coding of toxins: Cry3A, red squares; Cry4A and Cry4B mixture, violet diamonds; Cry11A, blue triangles; Cry1Ab, green circles; Cyt1A, yellow squares. In the experiment with Cry1Ab (B), the toxin was purified by high-performance liquid chromatography and activated toxin was provided as a salt-free lyophilisate by W. Moar (Auburn University, Auburn, AL).
Open in a separate windowaNL, nonlethal; >8, survival for >8 days.Aphids that survived ingestion of the Cry and Cyt proteins in the bioassays had markedly reduced growth rates compared to those of the control group (Fig. (Fig.2).2). Growth inhibition by each Cry protein correlated with mortality. Cry4 inhibited growth the most (Fig. (Fig.2A),2A), whereas Cry1Ab inhibited growth the least (Fig. (Fig.2B).2B). The IC50 of Cry4 was calculated to be 135 μg/ml. The growth of aphids surviving Cyt1A ingestion was strongly inhibited, with an average weight at the end of the assay, for doses of 125 μg/ml or higher, corresponding to less than 40% of that of the control group (Fig. (Fig.2B).2B). This decrease in aphid weight associated with the ingestion of Cyt1A is in contrast to the low mortality (about 10%) produced by the same dose of this protein. Most of the surviving insects did not reach adulthood as a result of feeding on Cyt1A, whereas control insects completed their nymphal development by the end of the bioassay.Cofeeding experiments with a mixture of toxins (Cry and Cyt1A) currently under way suggest that there is no identifiable synergy between Cry and Cyt toxins in this model, at least in the concentration range of 32 to 500 μg/ml (A.-M. Grenier et al., unpublished data).In two previous studies (10, 11), sensitivity of another aphid, Macrosiphum euphorbiae, to suspensions of Cry2, Cry3A, and Cry4 crystals was reported but no sensitivity to solubilized endotoxins was found. This may be explained by the lack of complete solubilization of the Bt crystals (10) and by the fact that control groups were fed a water-based artificial diet instead of a diet containing the buffer used to solubilize the crystals. Our bioassays, performed with buffer-based controls, show that A. pisum is indeed sensitive to Bt δ-endotoxins, although to a low degree. In fact, the IC50s and LC50s we calculated are very high compared to those of highly susceptible targets of B. thuringiensis (http://www.glfc.forestry.ca/bacillus/) but similar to those of organisms with low sensitivity, such as nematodes. For example, in feeding bioassays in which growth inhibition was measured against Caenorhabditis elegans fed E. coli/Cry strains, IC50s ranged from 16 μg/ml for Cry14A to as high as 230 μg/ml for Cry6A (12). The low activity of Bt endotoxins against aphids suggests that these proteins have not evolved to kill aphids. In fact, the ecological niches of B. thuringiensis and these insects are very different and it is unlikely that aphids, feeding on a virtually germfree environment such as plant phloem, come in contact with bacteria living either in other susceptible insects or on the plant surface. It might be hypothesized that the sensitivity of pea aphids to these Bt endotoxins is a consequence of similarities among midgut microvillar proteins and lipids, especially the surface molecules that compose the sugar residues known to serve as the initial binding sites for Bt toxins (4), rather than a result of direct selection for aphid sensitivity.The low sensitivity of aphids to Bt toxins is not in contrast to recent reports on the lack of deleterious effects of genetically modified crops on aphid populations (5). A recent report confirms the presence of Cry1Ac in the phloem of transgenic oilseed rape and in aphids feeding on these plants (2). However, the concentration of Cry1Ac in phloem, being low, is compatible with the absence of deleterious effects of transgenic oilseed rape on aphids, as well as with previous studies reporting no detectable levels of Cry toxins in phloem translocated through sieves of commercial transgenic plants (8). Although low, the susceptibility of aphids to B. thuringiensis we report here could theoretically lead to the development of effective strategies for controlling these and other sucking insect pests with genetically modified crops expressing appropriate toxins. However, two conditions should concur. (i) Toxins must be present in the plant phloem to be accessible to these pests and vectors, and (ii) more effective toxins should be found, and thus screening programs with a range of natural and engineered toxins should be performed in order to determine their activity on sucking insects. Although a wide range of further studies are still needed to assess the potential of Bt crops for controlling aphids and other sucking insect pests, the substantial economic losses sucking insects cause to agriculture worldwide clearly merit exploration of the possibilities our results suggest. 相似文献
TABLE 1.
ST50s of pea aphids feeding on solubilized Cry toxins and solubilized Cry toxins activated with trypsinToxin | Mean ST50a ± SE (days) at dose of:
| ||
---|---|---|---|
32 mg/ml | 125 mg/ml | 500 mg/ml | |
Cry1Ab | |||
Solubilized | NL | >8 | >8 |
Trypsinized | NL | >8 | >8 |
Cry3A | |||
Solubilized | NL | >8 | >8 |
Trypsinized | NL | >8 | 3.7 ± 1.2 |
Cry4A | |||
Solubilized | NL | >8 | 1.8 ± 0.14 |
Trypsinized | >8 | 1.8 ± 0.15 | 1.9 ± 0.17 |
Cry11A | |||
Solubilized | NL | >8 | 1.8 ± 0.14 |
Trypsinized | NL | >8 | 2.5 ± 0.10 |