全文获取类型
收费全文 | 2456篇 |
免费 | 171篇 |
专业分类
2627篇 |
出版年
2023年 | 23篇 |
2022年 | 37篇 |
2021年 | 68篇 |
2020年 | 54篇 |
2019年 | 64篇 |
2018年 | 77篇 |
2017年 | 86篇 |
2016年 | 115篇 |
2015年 | 146篇 |
2014年 | 154篇 |
2013年 | 178篇 |
2012年 | 188篇 |
2011年 | 195篇 |
2010年 | 110篇 |
2009年 | 97篇 |
2008年 | 114篇 |
2007年 | 115篇 |
2006年 | 110篇 |
2005年 | 83篇 |
2004年 | 86篇 |
2003年 | 75篇 |
2002年 | 60篇 |
2001年 | 52篇 |
2000年 | 69篇 |
1999年 | 45篇 |
1998年 | 15篇 |
1997年 | 15篇 |
1996年 | 10篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1974年 | 7篇 |
1973年 | 12篇 |
1972年 | 3篇 |
1970年 | 4篇 |
排序方式: 共有2627条查询结果,搜索用时 15 毫秒
51.
Cyril Ribeyre Judith Lopes Jean-Baptiste Boul Aurle Piazza Aurore Gudin Virginia A. Zakian Jean-Louis Mergny Alain Nicolas 《PLoS genetics》2009,5(5)
In budding yeast, the Pif1 DNA helicase is involved in the maintenance of both nuclear and mitochondrial genomes, but its role in these processes is still poorly understood. Here, we provide evidence for a new Pif1 function by demonstrating that its absence promotes genetic instability of alleles of the G-rich human minisatellite CEB1 inserted in the Saccharomyces cerevisiae genome, but not of other tandem repeats. Inactivation of other DNA helicases, including Sgs1, had no effect on CEB1 stability. In vitro, we show that CEB1 repeats formed stable G-quadruplex (G4) secondary structures and the Pif1 protein unwinds these structures more efficiently than regular B-DNA. Finally, synthetic CEB1 arrays in which we mutated the potential G4-forming sequences were no longer destabilized in pif1Δ cells. Hence, we conclude that CEB1 instability in pif1Δ cells depends on the potential to form G-quadruplex structures, suggesting that Pif1 could play a role in the metabolism of G4-forming sequences. 相似文献
52.
The ecology of mosquito species (Diptera: Culicidae) was studied in areas of the Serra do Mar State Park, State of S?o Paulo, Brazil. The influence of the lunar cycle and the daily biting rhythms of mosquito populations were analyzed. Systematized biweekly human bait collections were made in a silvatic environment for 24 consecutive months (January 1991 to December 1992). A total of 20,591 specimens of adult mosquitoes belonging to 55 species were collected from 545 catches. Sabethini species were captured exclusively during daylight periods, with the exception of Trichoprosopon digitatum, while members of Anophelinae predominated during nocturnal hours. Members of the subfamily Culicinae that were collected primary during nocturnal periods included Culex nigripalpus, Coquillettidia chrysonotum and Cq. venezuelensis while daytime catches included Psorophora ferox and Ps. albipes. Others members of culicines mosquitoes that were collected during both day and night included: Aedes serratus, Ae. scapularis and Ae. fulvus. Lunar cycles did not appear to influence the daily biting rhythms of most mosquito species in the area, but larger numbers of mosquitoes were collected during the new moon. Ae. scapularis were captured mainly during the full moon. 相似文献
53.
Maternal protein restriction during gestation and lactation in the rat results in increased brain levels of kynurenine and kynurenic acid in their adult offspring 下载免费PDF全文
54.
L. S. Lima K. P. Gramacho A. S. Gesteira U. V. Lopes F. A. Gaiotto H. A. Zaidan J. L. Pires J. C. M. Cascardo F. Micheli 《Molecular breeding : new strategies in plant improvement》2008,22(2):315-318
Theobroma cacao L.–Moniliophthora perniciosa expressed sequence tags (ESTs) were converted into useful satellite markers for population analysis and genetic mapping.
Forty-nine flanking primer pairs from TSH1188 (a resistant genotype) and Catongo (a susceptible genotype) ESTs were designed
and screened for polymorphism analysis. Eleven were polymorphic, with an average of 3.81 alleles per locus and a total of
42 alleles. The satellite markers were tested on 21 cacao accessions and two bulked DNAs generated from 6 resistant and 6
susceptible plants from a segregating F2 (SCA6 × ICS1) population for witches’ broom resistance. These results show that EST-derived microsatellites (short sequence
repeats, SSRs) in Theobroma cacao have many potential applications in linkage mapping and the planning of crosses. 相似文献
55.
Vanderlei Folmer Nuno Pedroso Sílvia C.D.N. Lopes Luísa Cyrne 《生物化学与生物物理学报:生物膜》2008,1778(4):1141-1147
In Saccharomyces cerevisiae, the diffusion rate of hydrogen peroxide (H2O2) through the plasma membrane decreases during adaptation to H2O2 by means of a mechanism that is still unknown. Here, evidence is presented that during adaptation to H2O2 the anisotropy of the plasma membrane increases. Adaptation to H2O2 was studied at several times (15min up to 90min) by applying the steady-state H2O2 delivery model. For wild-type cells, the steady-state fluorescence anisotropy increased after 30min, or 60min, when using 2-(9-anthroyloxy) stearic acid (2-AS), or diphenylhexatriene (DPH) membrane probe, respectively. Moreover, a 40% decrease in plasma membrane permeability to H2O2 was observed at 15min with a concomitant two-fold increase in catalase activity. Disruption of the ergosterol pathway, by knocking out either ERG3 or ERG6, prevents the changes in anisotropy during H2O2 adaptation. H2O2 diffusion through the plasma membrane in S. cerevisiae cells is not mediated by aquaporins since the H2O2 permeability constant is not altered in the presence of the aquaporin inhibitor mercuric chloride. Altogether, these results indicate that the regulation of the plasma membrane permeability towards H2O2 is mediated by modulation of the biophysical properties of the plasma membrane. 相似文献
56.
Wim E. J. M. Ghijsen Elly Besselsen Vincent Geukers Willem Kamphuis Fernando H. Lopes da Silva 《Journal of neurochemistry》1992,59(2):482-486
The effect of long-term potentiation (LTP) on endogenous amino acid release from rat hippocampus slices was studied. LTP was induced in vivo by application of a tetanus (200 Hz, 200 ms) to the Schaffer collateral fibers in unanesthetized rats. Endogenous release of glutamate and gamma-aminobutyric acid (GABA) was investigated 60 min after tetanization in CA1 subslices of potentiated and control rats. No significant effects of LTP were observed in basal and K(+)-induced Ca(2+)-independent release components of these amino acids. In contrast, K(+)-induced Ca(2+)-dependent release of both glutamate and GABA increased approximately 100% in slices from potentiated rats. No differences were observed in total content of glutamate and GABA between the subslices from control and LTP animals. These results suggest a persistent increase in the recruitment of the presynaptic vesicular pool of glutamate and GABA during LTP. 相似文献
57.
58.
Ouabain-insensitive Na+-ATPase of proximal tubules is an effector for urodilatin and atrial natriuretic peptide 总被引:2,自引:0,他引:2
Caruso-Neves C Vives D Dantas C Albino CM Fonseca LM Lara LS Iso M Lopes AG 《Biochimica et biophysica acta》2004,1660(1-2):93-98
In the present paper we studied the effect of urodilatin and atrial natriuretic peptide (ANP) on the proximal tubule Na+-ATPase and (Na+K+)ATPase activities. Urodilatin and ANP inhibit the Na+-ATPase activity but not the (Na+K+)ATPase activity. Maximal effect was observed at a concentration of 10(-11) M for both peptides. In this condition, the enzyme activity decreases from 10.8 +/- 1.6 (control) to 5.7 +/- 0.9 or 6.1 +/- 0.7 nmol Pi mg(-1) min(-1) in the presence of urodilatin or ANP, respectively. This effect was completely reversed by 10(-6) M LY83583, a guanylyl cyclase inhibitor, and mimicked by 10 nM cGMP. Furthermore, both ANP and urodilatin increase cGMP production by 33% and 49%, respectively. This is the first demonstration that it was shown that urodilatin and ANP directly modulate primary active sodium transport in the proximal tubule. The data obtained indicate that this effect is mediated by the activation of the NPR-A/guanylate cyclase/cGMP pathway. 相似文献
59.
60.
Bellon JR Eglinton JM Siebert TE Pollnitz AP Rose L de Barros Lopes M Chambers PJ 《Applied microbiology and biotechnology》2011,91(3):603-612
Increasingly, winemakers are looking for ways to introduce aroma and flavour diversity to their wines as a means of improving
style and increasing product differentiation. While currently available commercial yeast strains produce consistently sound
fermentations, there are indications that sensory complexity and improved palate structure are obtained when other species
of yeast are active during fermentation. In this study, we explore a strategy to increase the impact of non-Saccharomyces cerevisiae inputs without the risks associated with spontaneous fermentations, through generating interspecific hybrids between a S. cerevisiae wine strain and a second species. For our experiments, we used rare mating to produce hybrids between S. cerevisiae and other closely related yeast of the Saccharomyces sensu stricto complex. These hybrid yeast strains display desirable properties of both parents and produce wines with concentrations
of aromatic fermentation products that are different to what is found in wine made using the commercial wine yeast parent.
Our results demonstrate, for the first time, that the introduction of genetic material from a non-S. cerevisiae parent into a wine yeast background can impact favourably on the wine flavour and aroma profile of a commercial S. cerevisiae wine yeast. 相似文献