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   1352949篇
  免费   123111篇
  国内免费   1897篇
  2021年   17932篇
  2019年   16228篇
  2018年   17379篇
  2017年   16104篇
  2016年   27861篇
  2015年   42407篇
  2014年   50535篇
  2013年   76750篇
  2012年   35877篇
  2011年   23698篇
  2010年   42930篇
  2009年   44490篇
  2008年   22844篇
  2007年   20439篇
  2006年   26308篇
  2005年   27321篇
  2004年   26578篇
  2003年   24464篇
  2002年   22440篇
  2001年   36162篇
  2000年   33265篇
  1999年   32866篇
  1998年   25544篇
  1997年   25463篇
  1996年   25027篇
  1995年   23035篇
  1994年   22950篇
  1993年   21971篇
  1992年   28295篇
  1991年   26533篇
  1990年   24753篇
  1989年   25770篇
  1988年   23696篇
  1987年   22422篇
  1986年   21175篇
  1985年   23032篇
  1984年   22706篇
  1983年   20189篇
  1982年   20701篇
  1981年   19887篇
  1980年   18542篇
  1979年   19122篇
  1978年   17965篇
  1977年   17195篇
  1976年   16422篇
  1975年   15856篇
  1974年   16430篇
  1973年   16696篇
  1972年   14274篇
  1971年   13067篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
55.
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   
56.
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   
57.
58.
59.
60.
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   
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