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   1318458篇
  免费   116927篇
  国内免费   1422篇
  1436807篇
  2021年   17909篇
  2020年   12651篇
  2019年   16212篇
  2018年   17583篇
  2017年   16390篇
  2016年   28061篇
  2015年   42524篇
  2014年   50535篇
  2013年   76823篇
  2012年   36231篇
  2011年   24456篇
  2010年   43507篇
  2009年   44817篇
  2008年   23176篇
  2007年   21166篇
  2006年   26595篇
  2005年   27519篇
  2004年   27074篇
  2003年   24539篇
  2002年   22864篇
  2001年   31435篇
  2000年   28659篇
  1999年   29529篇
  1998年   25223篇
  1997年   24989篇
  1996年   24646篇
  1995年   22782篇
  1994年   22620篇
  1993年   21694篇
  1992年   26076篇
  1991年   24306篇
  1990年   22981篇
  1989年   23871篇
  1988年   21903篇
  1987年   20806篇
  1986年   19695篇
  1985年   21638篇
  1984年   21819篇
  1983年   19366篇
  1982年   20238篇
  1981年   19449篇
  1980年   18208篇
  1979年   18198篇
  1978年   17132篇
  1977年   16607篇
  1976年   15730篇
  1975年   15071篇
  1974年   15481篇
  1973年   15973篇
  1972年   13546篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
43.
44.
45.
Elevated levels of intracellular calcium are a major cause of myocardial dysfunction. To find possible mediators of the deregulated calcium we searched for EF-hand calcium-binding proteins of the S100 family. By PCR technology we identified three members of the S100 protein family (S100 alpha, CACY, and CAPL) in the human heart. We cloned the corresponding cDNAs and examined their expression levels in various human tissues by Northern blot analysis. All three proteins are expressed at high levels in the human heart. Whereas CACY and CAPL mRNAs are expressed ubiquitously, S100 alpha mRNA is restricted to heart, skeletal muscle, and brain. Interestingly, the expression pattern of S100 alpha, CACY, and CAPL in human tissues differs significantly from that in rodent tissues.  相似文献   
46.
1. Examination of the cerebrospinal fluid (CSF) of head-injured patients reveals that the concentration of intraventricular xanthine is elevated and that of uridine is decreased relative to those of adult lumbar CSF. 2. No correlations were observed between CSF lactate and CSF hypoxanthine, xanthine, or uridine, suggesting that changes in purine metabolites and the pyrimidine nucleoside do not index similar cellular events as does lactic acid production. 3. Ventricular CSF from hydrocephalic infants had uridine and hypoxanthine concentrations not significantly different from those of normal adult lumbar CSF, but xanthine was significantly elevated. 4. Since uridine has anticonvulsant properties and is a crucial substrate for cerebral metabolism, it may be useful to evaluate this pyrimidine for use in the management of patients with head injury.  相似文献   
47.
48.
49.
Studies of association between candidate genes and disease can be designed to use cases with disease, and in place of nonrelated controls, their parents. The advantage of this design is the elimination of spurious differences due to ethnic differences between cases and nonrelated controls. However, several statistical methods of analysis have been proposed in the literature, and the choice of analysis is not always clear. We review some of the statistical methods currently developed and present two new statistical methods aimed at specific genetic hypotheses of dominance and recessivity of the candidate gene. These new methods can be more powerful than other current methods, as demonstrated by simulations. The basis of these new statistical methods is a likelihood approach. The advantage of the likelihood framework is that regression models can be developed to assess genotype-environment interactions, as well as the relative contribution that alleles at the candidate-gene locus make to the relative risk (RR) of disease. This latter development allows testing of (1) whether interactions between alleles exist, on the scale of log RR, and (2) whether alleles originating from the mother or father of a case impart different risks, i.e., genomic imprinting.  相似文献   
50.
The Fis protein: it''s not just for DNA inversion anymore   总被引:36,自引:0,他引:36  
  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