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991.
Heather Z Holden MT Steward KF Parkhill J Song L Challis GL Robinson C Davis-Poynter N Waller AS 《Molecular microbiology》2008,70(5):1274-1292
In this study, we determined the function of a novel non-ribosomal peptide synthetase (NRPS) system carried by a streptococcal integrative conjugative element (ICE), ICESe2. The NRPS shares similarity with the yersiniabactin system found in the high-pathogenicity island of Yersinia sp. and is the first of its kind to be identified in streptococci. We named the NRPS product 'equibactin' and genes of this locus eqbA-N. ICESe2, although absolutely conserved in Streptococcus equi, the causative agent of equine strangles, was absent from all strains of the closely related opportunistic pathogen Streptococcus zooepidemicus. Binding of EqbA, a DtxR-like regulator, to the eqbB promoter was increased in the presence of cations. Deletion of eqbA resulted in a small-colony phenotype. Further deletion of the irp2 homologue eqbE, or the genes eqbH, eqbI and eqbJ encoding a putative ABC transporter, or addition of the iron chelator nitrilotriacetate, reversed this phenotype, implicating iron toxicity. Quantification of (55)Fe accumulation and sensitivity to streptonigrin suggested that equibactin is secreted by S. equi and that the eqbH, eqbI and eqbJ genes are required for its associated iron import. In agreement with a structure-based model of equibactin synthesis, supplementation of chemically defined media with salicylate was required for equibactin production. 相似文献
992.
In recent years, the antibody microarray technology has made significant progress, going from proof-of-concept designs to established high-performing technology platforms capable of targeting non-fractionated complex proteomes. In these cross-disciplinary efforts, a particular focus has lately been placed on two key technological issues: the sample and data handling. To this end, robust protocols have been designed for direct labelling of whole proteomes compatible with a sensitive fluorescent-based sensing. Tagging of the proteins with biotin in a single-colour approach has, in many cases, proven to be the preferred approach. Furthermore, based on modified approaches, adopted from the DNA microarray field, the first bioinformatic standards for performing the antibody microarray data analysis have emerged, though general standard operating procedure(s) remains to be implemented. 相似文献
993.
Brian M. Leckie Roberto M. Pereira William E. Klingeman Carl J. Jones Kimberly D. Gwinn 《Biocontrol Science and Technology》2008,18(7):697-710
Beauveria bassiana endophytically colonises corn (Zea mays) reducing tunneling from European corn borer (Ostrinia nubilalis). Endophytic colonisation of other plants by B. bassiana has been reported, and potentially, may reduce insect feeding on these plants. We evaluated the effects on larval growth and development, and mortality of different rates of dried, ground mycelia and water-soluble metabolites from fermentation broth culture of different isolates of B. bassiana incorporated into a synthetic diet and fed to neonate bollworm, Helicoverpa zea larvae. Development was delayed, weights of larvae were lower, and mortality was high for larvae fed the highest rates (1.0 and 5.0%, w/v) of mycelia incorporated diet compared to control. Insects fed diets containing mycelia of B. bassiana isolate 11-98 had the greatest mortality. Mortality was 100% for larvae fed 5% (w/v) mycelia incorporated diet of isolate 11-98, and 61% for isolate 3-00. For insects fed low rates (0.1 to 0.5%, w/v) of mycelia incorporated diet, mortality was lower, approximately 5% for isolate 11-98, and 5 to 14% for isolate 3-00. At the 0.1% (w/v) rate of mycelia incorporated diet, development occurred at an accelerated rate, compared to fungus-free controls, indicating increased nutrition in the lowest rate fungal diet. Mortality was low for all larvae fed diets containing spent fermentation broth of B. bassiana; however, development was delayed. Insects fed the highest rate (0.5%, v/v) of spent fermentation broth-amended diet had lower pupal weights, and a greater number of days to pupation than insects fed the lowest (0.1%, v/v) rate. Insects fed the 5% (v/v) rate of spent fermentation broth of isolates 11-98 and 3-00 had the longest days to pupation. 相似文献
994.
The Caribbean Islands are one of the world’s 34 biodiversity hotspots, remarkable for its biological richness and the high
level of threat to its flora and fauna. The palms (family Arecaceae) are well represented in the West Indies, with 21 genera
(three endemic) and 135 species (121 endemic). We provide an overview of phylogenetic knowledge of West Indian Palms, including
their relationships within a plastid DNA-based phylogeny of the Arecaceae. We present new data used to reconstruct the phylogeny
of tribe Cryosophileae, including four genera found in the West Indies, based on partial sequences of the low-copy nuclear
genes encoding phosphoribulokinase (PRK) and subunit 2 of RNA polymerase II (RPB2). Recently published phylogenetic studies
of tribe Cocoseae, based on PRK sequences, and tribes Cyclospatheae and Geonomateae, based on PRK and RPB2 sequences, also
provide information on the phylogenetic relationships of West Indian palms. Results of these analyses show many independent
origins of the West Indian Palm flora. These phylogenetic studies reflect the complex envolutionary history of the West Indies
and no single biogeographical pattern emerges for these palms. The present day distributions of West Indian palms suggest
complicated evolutionary interchange among islands, as well as between the West Indies and surrounding continents. We identified
six palm lineages that deserve conservation priority. Species-level phylogenies are needed for Copernicia, Sabal, and Roystonea before we can build a more complete understanding of the origin and diversification of West Indian palms.
An erratum to this article can be found at 相似文献
995.
996.
Laurent Badel Sandrine Lefort Thomas K. Berger Carl C. H. Petersen Wulfram Gerstner Magnus J. E. Richardson 《Biological cybernetics》2008,99(4-5):361-370
The dynamic I–V curve method was recently introduced for the efficient experimental generation of reduced neuron models. The method extracts the response properties of a neuron while it is subject to a naturalistic stimulus that mimics in vivo-like fluctuating synaptic drive. The resulting history-dependent, transmembrane current is then projected onto a one-dimensional current–voltage relation that provides the basis for a tractable non-linear integrate-and-fire model. An attractive feature of the method is that it can be used in spike-triggered mode to quantify the distinct patterns of post-spike refractoriness seen in different classes of cortical neuron. The method is first illustrated using a conductance-based model and is then applied experimentally to generate reduced models of cortical layer-5 pyramidal cells and interneurons, in injected-current and injected- conductance protocols. The resulting low-dimensional neuron models—of the refractory exponential integrate-and-fire type—provide highly accurate predictions for spike-times. The method therefore provides a useful tool for the construction of tractable models and rapid experimental classification of cortical neurons. 相似文献
997.
Bébarová M O'Hara T Geelen JL Jongbloed RJ Timmermans C Arens YH Rodriguez LM Rudy Y Volders PG 《American journal of physiology. Heart and circulatory physiology》2008,295(1):H48-H58
Two mechanisms are generally proposed to explain right precordial ST-segment elevation in Brugada syndrome: 1) right ventricular (RV) subepicardial action potential shortening and/or loss of dome causing transmural dispersion of repolarization; and 2) RV conduction delay. Here we report novel mechanistic insights into ST-segment elevation associated with a Na(+) current (I(Na)) loss-of-function mutation from studies in a Dutch kindred with the COOH-terminal SCN5A variant p.Phe2004Leu. The proband, a man, experienced syncope at age 22 yr and had coved-type ST-segment elevations in ECG leads V1 and V2 and negative T waves in V2. Peak and persistent mutant I(Na) were significantly decreased. I(Na) closed-state inactivation was increased, slow inactivation accelerated, and recovery from inactivation delayed. Computer-simulated I(Na)-dependent excitation was decremental from endo- to epicardium at cycle length 1,000 ms, not at cycle length 300 ms. Propagation was discontinuous across the midmyocardial to epicardial transition region, exhibiting a long local delay due to phase 0 block. Beyond this region, axial excitatory current was provided by phase 2 (dome) of the M-cell action potentials and depended on L-type Ca(2+) current ("phase 2 conduction"). These results explain right precordial ST-segment elevation on the basis of RV transmural gradients of membrane potentials during early repolarization caused by discontinuous conduction. The late slow-upstroke action potentials at the subepicardium produce T-wave inversion in the computed ECG waveform, in line with the clinical ECG. 相似文献
998.
999.
Electroacupuncture Reduces Voluntary Alcohol Intake in Alcohol-preferring Rats via an Opiate-sensitive Mechanism 总被引:1,自引:0,他引:1
Overstreet DH Cui CL Ma YY Guo CY Han JS Lukas SE Lee DY 《Neurochemical research》2008,33(10):2166-2170
Electroacupuncture (EA) has been shown to modify the effects of various drugs of abuse, including alcohol. Inbred P rats were
trained to drink alcohol voluntarily and then subjected to two periods of alcohol deprivation lasting 3 days. During the second
deprivation, the rats received either EA or sham EA. The rats were pretreated with naltrexone (5 mg/kg) or saline 30 min before
each of the EA or sham EA sessions. Approximately 6 h after the last naltrexone or saline treatment, the alcohol tubes were
returned and alcohol and water intakes were recorded later at 2, 4, 6, and 24 h. Only EA led to a decrease in alcohol intake,
which was most prominent at 6 and 24 h, and this inhibitory effect of EA was blocked by naltrexone, suggesting that activation
of the endogenous opiate system may be responsible for EA’s effects on alcohol intake in the alcohol-dependent iP rats.
Special issue article in honor of Ji-Sheng Han. 相似文献
1000.
Huang H Hutta DA Hu H DesJarlais RL Schubert C Petrounia IP Chaikin MA Manthey CL Player MR 《Bioorganic & medicinal chemistry letters》2008,18(7):2355-2361
A series of pyrimidinopyridones has been designed, synthesized and shown to be potent and selective inhibitors of the FMS tyrosine kinase. Introduction of an amide substituent at the 6-position of the pyridone core resulted in a significant potency increase. Compound 24 effectively inhibited in vivo LPS-induced TNF in mice greater than 80%. 相似文献