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   680433篇
  免费   83212篇
  国内免费   443篇
  2016年   7679篇
  2015年   11454篇
  2014年   13102篇
  2013年   18485篇
  2012年   21009篇
  2011年   21180篇
  2010年   14126篇
  2009年   13174篇
  2008年   18682篇
  2007年   19374篇
  2006年   17829篇
  2005年   17568篇
  2004年   17184篇
  2003年   16796篇
  2002年   16051篇
  2001年   29295篇
  2000年   29589篇
  1999年   23884篇
  1998年   8966篇
  1997年   9398篇
  1996年   9098篇
  1995年   8316篇
  1994年   8394篇
  1993年   8261篇
  1992年   19775篇
  1991年   18950篇
  1990年   18439篇
  1989年   18269篇
  1988年   16659篇
  1987年   16366篇
  1986年   15080篇
  1985年   14977篇
  1984年   12665篇
  1983年   11190篇
  1982年   8846篇
  1981年   8241篇
  1980年   7562篇
  1979年   12424篇
  1978年   9688篇
  1977年   9100篇
  1976年   8604篇
  1975年   9240篇
  1974年   9941篇
  1973年   9816篇
  1972年   8965篇
  1971年   8237篇
  1970年   7073篇
  1969年   6943篇
  1968年   6163篇
  1967年   5471篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
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   
93.
94.
The metabolism of the cholestatic triterpene acid reduced lantadene A has been studied in susceptible and resistant rats and in sheep which are susceptible to intoxication. Sheep and susceptible female rats produced a similar major metabolite and rats produced a second metabolite which was a glucuronide. These metabolites were also observed in extracts of bile canalicular membranes prepared from intoxicated rats. Resistant male and female rats produced a similar major metabolite which was different to those synthesized by susceptible animals. It is concluded that in rats and sheep there is a correlation between the type of metabolites produced in the liver and the susceptibility to intoxication by reduced lantadene A.  相似文献   
95.
96.
97.
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   
98.
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   
99.
Pharmacology of DMSO   总被引:10,自引:0,他引:10  
A wide range of primary pharmacological actions of dimethyl sulfoxide (DMSO) has been documented in laboratory studies: membrane penetration, membrane transport, effects on connective tissue, anti-inflammation, nerve blockade (analgesia), bacteriostasis, diuresis, enhancement or reduction of the effectiveness of other drugs, cholinesterase inhibition, nonspecific enhancement of resistance to infection, vasodilation, muscle relaxation, antagonism to platelet aggregation, and influence on serum cholesterol in experimental hypercholesterolemia. This substance induces differentiation and function of leukemic and other malignant cells. DMSO also has prophylactic radioprotective properties and cryoprotective actions. It protects against ischemic injury.  相似文献   
100.
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