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   785052篇
  免费   92778篇
  国内免费   566篇
  2016年   8612篇
  2015年   12835篇
  2014年   14644篇
  2013年   20839篇
  2012年   23582篇
  2011年   23716篇
  2010年   15733篇
  2009年   14703篇
  2008年   20954篇
  2007年   21727篇
  2006年   20136篇
  2005年   19695篇
  2004年   19385篇
  2003年   18567篇
  2002年   18079篇
  2001年   35383篇
  2000年   36091篇
  1999年   28839篇
  1998年   10378篇
  1997年   10704篇
  1996年   10218篇
  1995年   9473篇
  1994年   9460篇
  1993年   9329篇
  1992年   23287篇
  1991年   22396篇
  1990年   21846篇
  1989年   21386篇
  1988年   19627篇
  1987年   18933篇
  1986年   17666篇
  1985年   17573篇
  1984年   14776篇
  1983年   12728篇
  1982年   10211篇
  1981年   9308篇
  1980年   8586篇
  1979年   14289篇
  1978年   11260篇
  1977年   10359篇
  1976年   9684篇
  1975年   10627篇
  1974年   11623篇
  1973年   11440篇
  1972年   10488篇
  1971年   9618篇
  1970年   8218篇
  1969年   8094篇
  1968年   7303篇
  1967年   6286篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
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   
105.
106.
107.
108.
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   
109.
The linear sweep voltammetric method is used as a new approach for kinetic determination with enzymes accepting reversible redox couples as cosubstrate. A monolayer of hydrogenase molecules is grafted onto a glassy carbon electrode which is both the support of the enzyme and the detector of the activity. Reduced viologen concentration in the enzyme microenvironment is controlled by the electrode potential. The catalytic current produced by the enzyme allows an easy kinetic constant determination without the classical constraints found in hydrogenase kinetic measurements.  相似文献   
110.
The absence of centromeric bands in the karyotype of Felis catus is confirmed. It is also confirmed that no satellite band is visible in CsCl density gradients. However, a satellite is observed both by recentrifuging the fraction of the DNA that bands at high density in CsCl and by using netropsin to enhance the resolution of a CsCl gradient containing total F. catus DNA. The satellite, about 0.5% of total DNA, was isolated by repeated centrifugation in CsCl alone and in CsCl with netropsin. Netropsin was removed and a pure satellite DNA obtained. The reassociation kinetics (C0t1/2 less than 10(-3) M . s) show that the satellite is of the simple sequence type and hence a candidate for centromeric heterochromatin. Its cytological localisation awaits in situ hybridisation experiments.  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