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   878723篇
  免费   100705篇
  国内免费   554篇
  2018年   8116篇
  2017年   7674篇
  2016年   11099篇
  2015年   15081篇
  2014年   17573篇
  2013年   25277篇
  2012年   28329篇
  2011年   28822篇
  2010年   19382篇
  2009年   17898篇
  2008年   25306篇
  2007年   26173篇
  2006年   24126篇
  2005年   23435篇
  2004年   23163篇
  2003年   22058篇
  2002年   21219篇
  2001年   42253篇
  2000年   42383篇
  1999年   33515篇
  1998年   11441篇
  1997年   12058篇
  1996年   11394篇
  1995年   10457篇
  1994年   10357篇
  1993年   10210篇
  1992年   26923篇
  1991年   25801篇
  1990年   24975篇
  1989年   24547篇
  1988年   22295篇
  1987年   21173篇
  1986年   19655篇
  1985年   19280篇
  1984年   16098篇
  1983年   13623篇
  1982年   10429篇
  1981年   9459篇
  1980年   8910篇
  1979年   15170篇
  1978年   11596篇
  1977年   10726篇
  1976年   9824篇
  1975年   10685篇
  1974年   11571篇
  1973年   11297篇
  1972年   10261篇
  1971年   9419篇
  1970年   8006篇
  1969年   7678篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
112.
113.
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   
114.
115.
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   
116.
117.
118.
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   
119.
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   
120.
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   
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