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   663586篇
  免费   78055篇
  国内免费   487篇
  2018年   5513篇
  2016年   7802篇
  2015年   11430篇
  2014年   12879篇
  2013年   18606篇
  2012年   20825篇
  2011年   21168篇
  2010年   14078篇
  2009年   13019篇
  2008年   18776篇
  2007年   19318篇
  2006年   17844篇
  2005年   17466篇
  2004年   17132篇
  2003年   16380篇
  2002年   15779篇
  2001年   29706篇
  2000年   29926篇
  1999年   23953篇
  1998年   8762篇
  1997年   9238篇
  1996年   8870篇
  1995年   8016篇
  1994年   8055篇
  1993年   7949篇
  1992年   19505篇
  1991年   18847篇
  1990年   18296篇
  1989年   18161篇
  1988年   16426篇
  1987年   15854篇
  1986年   14537篇
  1985年   14489篇
  1984年   12252篇
  1983年   10497篇
  1982年   8250篇
  1981年   7544篇
  1980年   7035篇
  1979年   11653篇
  1978年   9016篇
  1977年   8454篇
  1976年   7865篇
  1975年   8486篇
  1974年   9258篇
  1973年   9083篇
  1972年   8161篇
  1971年   7593篇
  1970年   6538篇
  1969年   6400篇
  1968年   5748篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Experiments were made on rabbit fed an atherogenic diet (0.5 g/kg cholesterol) singly for 15 and 24 h and repeatedly for 3, 9 and 30 days. At early stages of lipid metabolism distress the interrelationship was established between blood rheological disorders and microcirculatory abnormalities. The dependence of the initial reaction of some rheological characteristics on their initial level was marked.  相似文献   
82.
83.
84.
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   
85.
86.
87.
88.
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   
89.
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   
90.
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