首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   645052篇
  免费   60360篇
  国内免费   256篇
  2018年   6775篇
  2017年   6342篇
  2016年   8620篇
  2015年   10634篇
  2014年   12935篇
  2013年   18475篇
  2012年   21063篇
  2011年   21802篇
  2010年   14847篇
  2009年   13411篇
  2008年   19244篇
  2007年   20184篇
  2006年   19131篇
  2005年   18145篇
  2004年   18251篇
  2003年   17506篇
  2002年   17234篇
  2001年   25012篇
  2000年   24641篇
  1999年   19895篇
  1998年   7408篇
  1997年   7327篇
  1996年   6908篇
  1995年   6423篇
  1994年   6378篇
  1993年   6304篇
  1992年   16982篇
  1991年   16807篇
  1990年   16637篇
  1989年   16476篇
  1988年   15480篇
  1987年   14478篇
  1986年   13538篇
  1985年   14043篇
  1984年   11567篇
  1983年   9894篇
  1982年   7551篇
  1981年   6665篇
  1980年   6395篇
  1979年   10942篇
  1978年   8574篇
  1977年   7976篇
  1976年   7694篇
  1975年   8501篇
  1974年   9378篇
  1973年   9147篇
  1972年   8372篇
  1971年   7735篇
  1970年   6650篇
  1969年   6595篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
991.
992.
993.
994.
995.
We have reported previously on use of a web‐based application, Supramap ( http://supramap.org ) for the study of biogeographic, genotypic, and phenotypic evolution. Using Supramap we have developed maps of the spread of drug‐resistant influenza and host shifts in H1N1 and H5N1 influenza and coronaviruses such as SARS. Here we report on another zoonotic pathogen, H7 influenza, and provide an update on the implementation of Supramap as a web service. We find that the emergence of pathogenic strains of H7 is labile with many transitions from high to low pathogenicity, and from low to high pathogenicity. We use Supramap to put these events in a temporal and geospatial context. We identify several lineages of H7 influenza with biomarkers of high pathogenicity in regions that have not been reported in the scientific literature. The original implementation of Supramap was built with tightly coupled client and server software. Now we have decoupled the components to provide a modular web service for POY ( http://poyws.org ) that can be consumed by a data provider to create a novel application. To demonstrate the web service, we have produced an application, Geogenes ( http://geogenes.org ). Unlike in Supramap, in which the user is required to create and upload data files, in Geogenes the user works from a graphical interface to query an underlying dataset. Geogenes demonstrates how the web service can provide underlying processing for any sequence and metadata database. © The Willi Hennig Society 2012.  相似文献   
996.
U Brandt  G von Jagow 《FEBS letters》1991,287(1-2):215-218
Cytochrome c reductase is inhibited by p-chlorophenyl-methoxybenzyl-ketoxime (CPMB-oxime). CPMB-oxime induces a red-shift of the reduced spectrum of cytochrome b. The inhibitor blocks the oxidation of ubihydroquinone at the QP center of this enzyme in a non-competitive way. The binding stoichiometry equals one inhibitor molecule per Qp center. The apparent Kd in a red-shift assay was 6.9 +/- 0.6 microM. All binding characteristics analysed in this study were very similar to those of the E-beta-methoxyacrylate inhibitors, although the chemical structure is different from these inhibitors. This result is interpreted as a support for the inhibitory mechanism based on the model of a 'catalytic switch' proposed recently for the E-beta-methoxyacrylate inhibitors (MOA-inhibitors (Brandt and von Jagow, Eur. J. Biochem.  相似文献   
997.
Mutagenesis of Nitrosomonas europaea was achieved by electroporation and recombination. To demonstrate this, an aminoglycoside 3'-phosphotransferase (kan) gene was specifically inserted into each of the three gene copies of hao individually. Southern hybridizations and PCR analysis showed the incorporation of the kan gene at the chosen genetic loci. The isolation of mutant strains was achieved in 7 to 14 days when the strains were grown on solid medium. The induced mutations were stable even in the absence of kanamycin-selective pressure for periods of up to 45 days in culture. The mutant strains did not show an observable phenotype different from that of the wild type when grown under the same conditions.  相似文献   
998.
The moving parts of voltage-gated ion channels.   总被引:32,自引:0,他引:32  
  相似文献   
999.
1000.
The study was designed to test the hypothesis that, during strength training, a restricted blood supply to the working muscles stimulates the secretion of anabolic hormones and an increase in the muscle mass and strength can be achieved with significantly lower training loads. During eight weeks, three times a week, 18 young, physically active males trained their leg extensor muscles. Nine subjects (group I) worked at 80% of the maximal voluntary contraction (MVC), whereas the rest (group II) performed their exercise without relaxation and at a lower load (50% MVC). The total training load in group II was significantly lower than in group I (77 ± 5 vs. 157 ± 7 kJ, respectively). The eight-week training of both groups significantly increased the mean maximum strength (by 35 and 21% in groups I and II, respectively) and volume (by 17 and 9%, respectively) of the muscles trained (however, the differences between the groups with respect to these changes were nonsignificant). Group I displayed a higher increase in the blood level of creatine phosphokinase than group II, while group II showed a greater increase in the blood concentration of lactate. In contrast to group I, group II displayed a significant increase in the blood concentrations of growth hormone, insulin-like growth factor 1 (IGF-1), and cortisol. Hence, the suggestion that the secretion of metabolic hormones is triggered by a metabolic, rather than mechanical, stimulus from working muscles seems plausible.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号