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   8827篇
  免费   665篇
  国内免费   460篇
  2023年   73篇
  2022年   72篇
  2021年   290篇
  2020年   230篇
  2019年   266篇
  2018年   283篇
  2017年   232篇
  2016年   322篇
  2015年   462篇
  2014年   582篇
  2013年   640篇
  2012年   740篇
  2011年   708篇
  2010年   414篇
  2009年   373篇
  2008年   424篇
  2007年   417篇
  2006年   368篇
  2005年   360篇
  2004年   292篇
  2003年   299篇
  2002年   242篇
  2001年   194篇
  2000年   193篇
  1999年   162篇
  1998年   109篇
  1997年   98篇
  1996年   103篇
  1995年   101篇
  1994年   80篇
  1993年   78篇
  1992年   127篇
  1991年   101篇
  1990年   73篇
  1989年   73篇
  1988年   67篇
  1987年   49篇
  1986年   41篇
  1985年   53篇
  1984年   33篇
  1983年   24篇
  1982年   19篇
  1981年   11篇
  1979年   10篇
  1978年   6篇
  1977年   7篇
  1971年   7篇
  1970年   7篇
  1968年   5篇
  1966年   7篇
排序方式: 共有9952条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
7.
8.
The Twin Bridges Training Area (TBTA) in the Republic of Korea consists of dirt roads, barren training areas, and forested hillsides adjacent to linear and broad expanses of tall grasses, herbaceous, and scrub vegetation. Of the six species of small mammals, the striped field mouse, Apodemus agrarius, was the most frequently captured (96.1%). Apodemus agrarius capture rates varied from 17.7 to 33.2% during three trapping periods. Gravid females were observed during November‐December 2006 (8.4%) and March 2007 (5.1%). In 2005, the overall seroprevalence of Hantaan virus (HTNV) was high (34.4%) and lower during surveys in 2006 (14.2%) and 2007 (13.8%). Seroprevalence was directly correlated with weight increase of A. agrarius.  相似文献   
9.
A genome project focusingon the nematode Caenorhabditis elegans has demonstrated thepresence of eight cDNAs belonging to the major intrinsic proteinsuperfamily. We functionally characterized one of these cDNAs namedC01G6.1. Injection of C01G6.1 cRNA increased the osmotic waterpermeability (Pf) of Xenopusoocytes 11-fold and the urea permeability 4.5-fold but failed toincrease the glycerol permeability. It has been speculated that the MIPfamily may be separated into two large subfamilies based on thepresence or absence of two segments of extra amino acid residues (~15amino acids) at the second and third extracellular loops. BecauseC01G6.1 (designated AQP-CE1), AQP3, and glycerol facilitator (GlpF) all have these two segments, we replaced the segments of AQP-CE1 with thoseof AQP3 and GlpF to identify their roles. The functional characteristics of these mutants were principally similar to that ofwild-type AQP-CE1, although the values of Pf andurea permeability were decreased by 39-74% and 28-65%,respectively. These results suggest that the two segments of extraamino acid residues may not contribute to channel selectivity orformation of the route for small solutes.

  相似文献   
10.
With recent advances in understanding of the neuroscience of risk taking, attention is now turning to genetic factors that may contribute to individual heterogeneity in risk attitudes. In this paper we test for genetic associations with risk attitude measures derived from both the psychology and economics literature. To develop a long-term prospective study, we first evaluate both types of risk attitudes and find that the economic and psychological measures are poorly correlated, suggesting that different genetic factors may underlie human response to risk faced in different behavioral domains. We then examine polymorphisms in a spectrum of candidate genes that affect neurotransmitter systems influencing dopamine regulation or are thought to be associated with risk attitudes or impulsive disorders. Analysis of the genotyping data identified two single nucleotide polymorphisms (SNPs) in the gene encoding the alpha 4 nicotine receptor (CHRNA4, rs4603829 and rs4522666) that are significantly associated with harm avoidance, a risk attitude measurement drawn from the psychology literature. Novelty seeking, another risk attitude measure from the psychology literature, is associated with several COMT (catechol-O-methyl transferase) SNPs while economic risk attitude measures are associated with several VMAT2 (vesicular monoamine transporter) SNPs, but the significance of these associations did not withstand statistical adjustment for multiple testing and requires larger cohorts. These exploratory results provide a starting point for understanding the genetic basis of risk attitudes by considering the range of methods available for measuring risk attitudes and by searching beyond the traditional direct focus on dopamine and serotonin receptor and transporter genes.  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