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   1293553篇
  免费   152019篇
  国内免费   821篇
  2018年   10791篇
  2016年   15300篇
  2015年   22407篇
  2014年   25753篇
  2013年   36729篇
  2012年   41137篇
  2011年   41472篇
  2010年   28263篇
  2009年   26321篇
  2008年   37266篇
  2007年   38369篇
  2006年   35680篇
  2005年   34414篇
  2004年   33582篇
  2003年   32503篇
  2002年   31445篇
  2001年   53514篇
  2000年   54083篇
  1999年   43610篇
  1998年   17231篇
  1997年   17891篇
  1996年   17141篇
  1995年   16042篇
  1994年   15838篇
  1993年   15785篇
  1992年   36977篇
  1991年   35795篇
  1990年   35065篇
  1989年   34343篇
  1988年   31641篇
  1987年   30824篇
  1986年   28608篇
  1985年   28861篇
  1984年   24211篇
  1983年   21124篇
  1982年   16888篇
  1981年   15238篇
  1980年   14496篇
  1979年   23560篇
  1978年   18821篇
  1977年   17217篇
  1976年   16363篇
  1975年   17703篇
  1974年   18950篇
  1973年   18592篇
  1972年   16862篇
  1971年   15639篇
  1970年   13355篇
  1969年   12844篇
  1968年   11514篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
162.
163.
With DNA sequencing now getting cheaper more quickly than data storage or computation, the time may have come for genome informatics to migrate to the cloud.  相似文献   
164.
OBJECTIVE--To test the hypothesis that farmers are at high risk of hip osteoarthritis and to investigate possible causes for such a hazard. DESIGN--Cross sectional survey. SETTING--Five rural general practices. SUBJECTS--167 male farmers aged 60-76 and 83 controls from mainly sedentary jobs. All those without previous hip replacement underwent radiography of the hip. MAIN OUTCOME MEASURES--Hip replacement for osteoarthritis or radiological evidence of hip osteoarthritis. RESULTS--Prevalence of hip osteoarthritis was higher in farmers than controls and especially in those who had farmed for over 10 years (odds ratio 9.3, 95% confidence interval 1.9 to 44.5). The excess could not be attributed to any one type of farming, and heavy lifting seems the likely explanation. CONCLUSIONS--Manual handling in agriculture should be limited where possible. Consideration should be given to making hip osteoarthritis a prescribed industrial disease in farmers. There may be wider implications for the prevention of hip osteoarthritis in the general population.  相似文献   
165.
166.
Synthesis of prenylquinones in chloroplasts   总被引:3,自引:0,他引:3  
  相似文献   
167.
168.
169.
An earlier report (1) of an adverse effect of high doses of oxytocin on human memory included results of studies on women receiving oxytocin as part of the treatment to induce 2nd trimester therapeutic abortion. These women served as their own controls. We have now been able to study a group of women who have been treated in all ways like the original group, with the exception that they did not receive oxytocin. The results from this external control corroborate the finding that oxytocin affected memory.  相似文献   
170.
A protein kinase was isolated from spinach thylakoid membranes by solubilization with octyl glucoside and cholate. The enzyme was purified to apparent homogeneity by ammonium sulfate precipitation, gel filtration, and sucrose density centrifugation, followed by affinity chromatography on either Affi-Gel blue (yielding denatured enzyme) or on histone cross-linked to Sepharose (yielding active enzyme). Electrophoresis on denaturing polyacrylamide gels, followed by staining with silver, revealed the kinase as a single band corresponding to an apparent molecular mass of 64 kDa. The active enzyme underwent autophosphorylation and could be detected by autoradiography following incubation with [gamma-32P]ATP and Mg2+ ion. The specific phosphotransferase activity of purified kinase was approximately 30 nmol of phosphate min-1 (mg protein)-1 with lysine-rich histone (III-S or V-S) as substrate; casein was phosphorylated at approximately 30% of this rate. The physiological substrate for the kinase is presumed to be light-harvesting chlorophyll a/b protein complex. In solubilized form, this was phosphorylated at approximately 10% of the rate observed with histone III-S as substrate, or 10-100 times slower than the estimated rate of phosphorylation of the light-harvesting complex in situ. Possible reasons for this shortfall are considered. The kinase is proposed as the principal effector of thylakoid protein phosphorylation and associated State transition phenomena.  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