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161.
Ruimy R Maiga A Armand-Lefevre L Maiga I Diallo A Koumaré AK Ouattara K Soumaré S Gaillard K Lucet JC Andremont A Feil EJ 《Journal of bacteriology》2008,190(11):3962-3968
Staphylococcus aureus is an important human pathogen, but it appears more commonly in asymptomatic colonization of the nasopharynx than in cases of invasive disease. Evidence concerning the global population structure of S. aureus is limited by the overrepresentation in the multilocus sequence testing database of disease isolates recovered from Western Europe, the Americas, Australia, and Japan. We address this by presenting data from the S. aureus carriage population in Mali, the first detailed characterization of asymptomatic carriage from an African population. These data confirm the pandemic spread of many of the common S. aureus clones in the carriage population. We also note the high frequency (approximately 24%) of a single divergent genotype, sequence type 152 (ST152), which has not previously been recovered from nasal carriage isolates but corresponds to a sporadic Panton-Valentine leukocidin (PVL)-positive, community-acquired methicillin-resistant S. aureus clone noted mostly in Central Europe. We show that 100% of the ST152 isolates recovered from nasal carriage samples in Mali are PVL positive and discuss implications relating to the emergence and spread of this virulent genotype. 相似文献
162.
Kinetics of drought-induced pathogenesis-related proteins and its physiological significance in white clover leaves 总被引:2,自引:0,他引:2
To investigate the responses of pathogenesis-related (PR) proteins to the intensity of drought stress and their physiological significance in white clover ( Trifolium repens L.), the change of enzyme activity and its relationship with some physiological parameters were assessed for 28 days under well-watered (control) and water-deficit conditions. Water-deficit treatment gradually decreased leaf water potential (Ψw ) to −2.33 MPa at day 28. Dry matter significantly decreased from 21 days of water-deficit treatment, while proline and ammonia concentration increased within 7 days. The increase in PR-protein activity was closely related with the decrease in Ψw . The β-1,3-glucanase (EC 3.2.1.39) activity in water-deficit leaves rapidly increased for the first 14 days (Ψw ≥ −1.67) and then slightly decreased, while the chitinase (EC 3.2.1.14) and cellulase (EC 3.2.1.4) activity continued to increase throughout the experimental period. The enhanced activation of β-1,3-glucanase, chitinase and cellulase for the period of days 0–14 was significantly ( P ≤ 0.01) related to the increase of proline and ammonia concentrations. The results indicate that the enhanced activity of β-1,3-glucanase, cellulase and chitinase for the early period might be an act of transient tolerance to drought stress, but the activation of these enzymes during terminal stress might be a drought-stress-induced injurious symptom. 相似文献
163.
Ing-Marie Viklund Pontus Aspenström Vannary Meas-Yedid Jolanta Kopec Daniel Ågren Gunter Schneider Mauro D'Amato Jean-Christophe Olivo-Marin Guy Tran Van Nhieu Sven Pettersson 《Experimental cell research》2009,315(6):1040-220
We have previously identified a new gene with sequence homology to the WASP-family of actin regulators denoted WAFL (WASP and FKBP-like). Here we report a possible biological function for WAFL, by demonstrating an association to early endosomes via its central coiled-coil domain. Further we show by functional and structural studies that WAFL is associated with both microtubules and the actin filament system, the two means of transport of early endosomes. In addition, WAFL interacts with WASP-interacting protein (WIP) and actin, thus linking WAFL to actin dynamics. The use of RNAi depletion of WAFL shows that WAFL-deficient cells display delayed transport of endosomal cargo. Our findings are compatible with a model whereby WAFL is involved in the transport of early endosomes at the level of transition between microfilament-based and microtubule-based movement. 相似文献
164.
165.
B. Vandekerkhove L. Parmentier G. Van Stappen S. Grenier G. Febvay M. Rey P. De Clercq 《Journal of Applied Entomology》2009,133(2):133-142
The suitability of cysts of the brine shrimp Artemia sp. as a factitious food for the predator Macrolophus pygmaeus Rambur was investigated. The influence of decapsulation time and hydration of the cysts on the performance of the predator were studied in the absence of plant material. A longer time of decapsulation had a positive influence on the development of the predator. Hydration of cysts had a significant impact on nymphal survival when cysts where non‐decapsulated or poorly decapsulated. An experiment in which nymphs were switched from a diet of hydrated cysts to non‐hydrated cysts showed that in the absence of plant material the relative importance of hydrating the cysts decreased with nymphal age. Especially, the first instar and to a lesser extent the second instar appear to be susceptible to water shortage. Effects of prolonged rearing on development and reproduction on brine shrimp cysts from different origins were tested in the presence of plant material. Rearing M. pygmaeus on Artemia sp. (Jingyu Lake) cysts yielded similar survival, development, adult weight and fecundity in the fourth as in the second generation. In contrast, for Artemia franciscana cysts, an increase in nymphal development was notable. Biochemical analyses showed that total amino acid content and the concentration of the different amino acids did not differ among diets and generations. There were, however, differences in total fatty acid content between the different diets and generations and in the concentration of certain fatty acids, indicating that insects fed brine shrimp cysts may show nutritional deficiencies compared to those reared on a diet of Ephestia kuehniella eggs. Our results indicate that decapsulated brine shrimp cysts are an economically viable alternative food source in at least part of the rearing process for M. pygmaeus. 相似文献
166.
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 |
167.
Olivier Le Bihan Pierre Bonnafous Laszlo Marak Thomas Bickel Sylvain Trpout Stphane Mornet Felix De Haas Hugues Talbot Jean-Christophe Taveau Olivier Lambert 《Journal of structural biology》2009,168(3):419-425
Nanoparticle transport across cell membrane plays a crucial role in the development of drug delivery systems as well as in the toxicity response induced by nanoparticles. As hydrophilic nanoparticles interact with lipid membranes and are able to induce membrane perturbations, hypothetic mechanisms based on membrane curvature or hole formation have been proposed for activating their transmigration. We report on the transport of hydrophilic silica nanoparticles into large unilamellar neutral DOPC liposomes via an internalization process. The strong adhesive interactions of lipid membrane onto the silica nanoparticle triggered liposome deformation until the formation of a curved neck. Then the rupture of this membrane neck led to the complete engulfment of the nanoparticle. Using cryo-electron tomography we determined 3D architectures of intermediate steps of this process unveiling internalized silica nanoparticles surrounded by a supported lipid bilayer. This engulfing process was achieved for a large range of particle size (from 30 to 200 nm in diameter). These original data provide interesting highlights for nanoparticle transmigration and could be applied to biotechnology development. 相似文献
168.
169.
170.
Richard J. Grainger J. David Barrass Alain Jacquier Jean-Christophe Rain Jean D. Beggs 《RNA (New York, N.Y.)》2009,15(12):2161-2173
In Saccharomyces cerevisiae, Cwc21p is a protein of unknown function that is associated with the NineTeen Complex (NTC), a group of proteins involved in activating the spliceosome to promote the pre-mRNA splicing reaction. Here, we show that Cwc21p binds directly to two key splicing factors—namely, Prp8p and Snu114p—and becomes the first NTC-related protein known to dock directly to U5 snRNP proteins. Using a combination of proteomic techniques we show that the N-terminus of Prp8p contains an intramolecular fold that is a Snu114p and Cwc21p interacting domain (SCwid). Cwc21p also binds directly to the C-terminus of Snu114p. Complementary chemical cross-linking experiments reveal reciprocal protein footprints between the interacting Prp8 and Cwc21 proteins, identifying the conserved cwf21 domain in Cwc21p as a Prp8p binding site. Genetic and functional interactions between Cwc21p and Isy1p indicate that they have related functions at or prior to the first catalytic step of splicing, and suggest that Cwc21p functions at the catalytic center of the spliceosome, possibly in response to environmental or metabolic changes. We demonstrate that SRm300, the only SR-related protein known to be at the core of human catalytic spliceosomes, is a functional ortholog of Cwc21p, also interacting directly with Prp8p and Snu114p. Thus, the function of Cwc21p is likely conserved from yeast to humans. 相似文献