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51.
A comparison of chemical pretreatment methods for improving saccharification of cotton stalks 总被引:19,自引:0,他引:19
Silverstein RA Chen Y Sharma-Shivappa RR Boyette MD Osborne J 《Bioresource technology》2007,98(16):3000-3011
The effectiveness of sulfuric acid (H(2)SO(4)), sodium hydroxide (NaOH), hydrogen peroxide (H(2)O(2)), and ozone pretreatments for conversion of cotton stalks to ethanol was investigated. Ground cotton stalks at a solid loading of 10% (w/v) were pretreated with H(2)SO(4), NaOH, and H(2)O(2) at concentrations of 0.5%, 1%, and 2% (w/v). Treatment temperatures of 90 degrees C and 121 degrees C at 15 psi were investigated for residence times of 30, 60, and 90 min. Ozone pretreatment was performed at 4 degrees C with constant sparging of stalks in water. Solids from H(2)SO(4), NaOH, and H(2)O(2) pretreatments (at 2%, 60 min, 121 degrees C/15 psi) showed significant lignin degradation and/or high sugar availability and hence were hydrolyzed by Celluclast 1.5L and Novozym 188 at 50 degrees C. Sulfuric acid pretreatment resulted in the highest xylan reduction (95.23% for 2% acid, 90 min, 121 degrees C/15 psi) but the lowest cellulose to glucose conversion during hydrolysis (23.85%). Sodium hydroxide pretreatment resulted in the highest level of delignification (65.63% for 2% NaOH, 90 min, 121 degrees C/15 psi) and cellulose conversion (60.8%). Hydrogen peroxide pretreatment resulted in significantly lower (p相似文献
52.
Kelly A. Speer Brandi Jo Petronio Nancy B. Simmons Rebecca Richey Kristin Magrini J. Angel Soto‐Centeno David L. Reed 《Ecology and evolution》2017,7(19):7585-7598
Dispersal is a driving factor in the creation and maintenance of biodiversity, yet little is known about the effects of habitat variation and geography on dispersal and population connectivity in most mammalian groups. Bats of the family Molossidae are fast‐flying mammals thought to have potentially high dispersal ability, and recent studies have indicated gene flow across hundreds of kilometers in continental North American populations of the Brazilian free‐tailed bat, Tadarida brasiliensis. We examined the population genetics, phylogeography, and morphology of this species in Florida and across islands of The Bahamas, which are part of an island archipelago in the West Indies. Previous studies indicate that bats in the family Phyllostomidae, which are possibly less mobile than members of the family Molossidae, exhibit population structuring across The Bahamas. We hypothesized that T. brasiliensis would show high population connectivity throughout the islands and that T. brasiliensis would show higher connectivity than two species of phyllostomid bats that have been previously examined in The Bahamas. Contrary to our predictions, T. brasiliensis shows high population structure between two groups of islands in The Bahamas, similar to the structure exhibited by one species of phyllostomid bat. Phylogenetic and morphological analyses suggest that this structure may be the result of ancient divergence between two populations of T. brasiliensis that subsequently came into contact in The Bahamas. Our findings additionally suggest that there may be cryptic species within T. brasiliensis in The Bahamas and the West Indies more broadly. 相似文献
53.
Lightbody KL Renshaw PS Collins ML Wright RL Hunt DM Gordon SV Hewinson RG Buxton RS Williamson RA Carr MD 《FEMS microbiology letters》2004,238(1):255-262
We have previously shown that the secreted M. tuberculosis complex proteins CFP-10 and ESAT-6 form a tight, 1:1 complex, which may represent their functional form. In the work reported here a combination of yeast two-hybrid and biochemical analysis has been used to characterise complex formation between two other pairs of CFP-10/ESAT-6 family proteins (Rv0287/Rv0288 and Rv3019c/Rv3020c) and to determine whether complexes can be formed between non-genome paired members of the family. The results clearly demonstrate that Rv0287/Rv0288 and Rv3019c/3020c form tight complexes, as initially observed for CFP-10/ESAT-6. The closely related Rv0287/Rv0288 and Rv3019c/Rv3020c proteins are also able to form non-genome paired complexes (Rv0287/Rv3019c and Rv0288/Rv3020c), but are not capable of binding to the more distantly related CFP-10/ESAT-6 proteins. 相似文献
54.
I Feinkohl N Sattar P Welsh RM Reynolds IJ Deary MW Strachan JF Price;on behalf of the Edinburgh Type Diabetes Study 《PloS one》2012,7(9):e44569
Background
Type 2 diabetes mellitus is associated with risk of congestive heart failure (CHF), cognitive dysfunction and depression. CHF itself is linked both to poor cognition and depression. The ventricular N-terminal pro-brain natriuretic peptide (NT-proBNP) is a marker of CHF, suggesting potential as a marker for cognitive impairment and/or depression. This was tested in the Edinburgh Type 2 Diabetes Study (ET2DS).Methodology and Principal Findings
Cross-sectional analysis of 1066 men and women aged 60–75 with type 2 diabetes. Results from seven neuropsychological tests were combined in a standardised general cognitive ability factor, ‘g’. A vocabulary-based test estimated pre-morbid cognitive ability. The Hospital Anxiety and Depression Scale (HADS) assessed possible depression. After adjustment for age and sex, raised plasma NT-proBNP was weakly associated with lower ‘g’ and higher depression scores (ß −0.09, 95% CI −0.13 to −0.03, p = 0.004 and ß 0.08, 95% CI 0.04 to 0.12, p<0.001, respectively). Comparing extreme quintiles of NT-proBNP, subjects in the highest quintile were more likely to have reduced cognitive ability (within the lowest tertile of ‘g’) and ‘possible’ depression (HADS depression ≥8) (OR 1.80; 95% CI: 1.20, 2.70; p = 0.005 and OR 2.18; 95% CI: 1.28, 3.71; p = 0.004, respectively). Associations persisted when pre-morbid ability was adjusted for, but as expected were no longer statistically significant following the adjustment for diabetes-related and vascular co-variates (β −0.02, 95% CI −0.07 to 0.03, p>0.05 for ‘g’; β 0.03, 95% CI −0.02 to 0.07, p>0.05 for depression scores).Conclusion
Raised plasma NT-proBNP was weakly but statistically significantly associated with poorer cognitive function and depression. The prospective phases of the ET2DS will help determine whether or not NT-proBNP can be considered a risk marker for subsequent cognitive impairment and incident depression and whether it provides additional information over and above traditional risk factors for these conditions. 相似文献55.
Habitat fragmentation has often been implicated in the decline of many species. For habitat specialists and/or sedentary species, loss of habitat can result in population isolation and lead to negative genetic effects. However, factors other than fragmentation can often be important and also need to be considered when assessing the genetic structure of a species. We genotyped individuals from 13 populations of the cooperatively breeding Brown‐headed Nuthatch Sitta pusilla in Florida to test three alternative hypotheses regarding the effects that habitat fragmentation might have on genetic structure. A map of potential habitat developed from recent satellite imagery suggested that Brown‐headed Nuthatch populations in southern Florida occupied smaller and more isolated habitat patches (i.e. were more fragmented) than populations in northern Florida. We also genotyped individuals from a small, isolated Brown‐headed Nuthatch population on Grand Bahama Island. We found that populations associated with more fragmented habitat in southern Florida had lower allelic richness than populations in northern Florida (P = 0.02), although there were no differences in heterozygosity. Although pairwise estimates of FST were low overall, values among southern populations were generally higher than northern populations. Population assignment tests identified K = 3 clusters corresponding to a northern cluster, a southern cluster and a unique population in southeast Florida; using sampling localities as prior information revealed K = 7 clusters, with greater structure only among southern Florida populations. The Bahamas population showed moderate to high differentiation compared with Florida populations. Overall, our results suggest that fragmentation could affect gene flow in Brown‐headed Nuthatch populations and is likely to become more pronounced over time. 相似文献
56.
57.
58.
Direct comparison of binding equilibrium, thermodynamic, and rate constants determined by surface- and solution-based biophysical methods 总被引:9,自引:0,他引:9
Day YS Baird CL Rich RL Myszka DG 《Protein science : a publication of the Protein Society》2002,11(5):1017-1025
The binding interactions of small molecules with carbonic anhydrase II were used as model systems to compare the reaction constants determined from surface- and solution-based biophysical methods. Interaction data were collected for two arylsulfonamide compounds, 4-carboxybenzenesulfonamide (CBS) and 5-dimethyl-amino-1-naphthalene-sulfonamide (DNSA), binding to the enzyme using surface plasmon resonance, isothermal titration calorimetry, and stopped-flow fluorescence. We demonstrate that when the surface plasmon resonance biosensor experiments are performed with care, the equilibrium, thermodynamic, and kinetic constants determined from this surface-based technique match those acquired in solution. These results validate the use of biosensor technology to collect reliable data on small molecules binding to immobilized macromolecular targets. Binding kinetics were shown to provide more detailed information about complex formation than equilibrium constants alone. For example, although carbonic anhydrase II bound DNSA with twofold higher affinity than CBS, kinetic analysis revealed that CBS had a fourfold slower dissociation rate. Analysis of the binding and transition state thermodynamics also revealed significant differences in the enthalpy and entropy of complex formation. The lack of labeling requirements, high information content, and high throughput of surface plasmon resonance biosensors will make this technology an important tool for characterizing the interactions of small molecules with enzymes and receptors. 相似文献
59.
Developmental programming: State‐of‐the‐science and future directions–Summary from a Pennington Biomedical symposium 下载免费PDF全文
60.
William J. Sutherland Rosalind Aveling Thomas M. Brooks Mick Clout Lynn V. Dicks Liz Fellman Erica Fleishman David W. Gibbons Brandon Keim Fiona Lickorish Kathryn A. Monk Diana Mortimer Lloyd S. Peck Jules Pretty Johan Rockström Jon Paul Rodríguez Rebecca K. Smith Mark D. Spalding Femke H. Tonneijck Andrew R. Watkinson 《Trends in ecology & evolution》2014