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   695620篇
  免费   80354篇
  国内免费   2311篇
  2021年   6092篇
  2018年   6675篇
  2016年   9044篇
  2015年   13314篇
  2014年   15084篇
  2013年   20952篇
  2012年   23671篇
  2011年   23693篇
  2010年   15663篇
  2009年   14311篇
  2008年   20262篇
  2007年   20655篇
  2006年   19040篇
  2005年   18460篇
  2004年   18012篇
  2003年   17126篇
  2002年   16423篇
  2001年   30065篇
  2000年   30296篇
  1999年   24383篇
  1998年   9102篇
  1997年   9518篇
  1996年   9224篇
  1995年   8325篇
  1994年   8345篇
  1993年   8137篇
  1992年   19739篇
  1991年   19039篇
  1990年   18529篇
  1989年   18344篇
  1988年   16554篇
  1987年   15975篇
  1986年   14653篇
  1985年   14597篇
  1984年   12337篇
  1983年   10566篇
  1982年   8303篇
  1981年   7588篇
  1980年   7068篇
  1979年   11710篇
  1978年   9048篇
  1977年   8495篇
  1976年   7890篇
  1975年   8516篇
  1974年   9289篇
  1973年   9117篇
  1972年   8184篇
  1971年   7617篇
  1970年   6557篇
  1969年   6415篇
排序方式: 共有10000条查询结果,搜索用时 156 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.
90.
β-Xylosidases are hydrolytic enzymes which play an important role in xylan degradation, hydrolyzing xylobiose and xylooligosaccharides to xylose from the non-reducing end. Filamentous fungi are particularly interesting producers of this enzyme from an industrial point of view, due to the fact that they secrete β-xylosidases into the medium. Besides, fungal β-xylosidases are highly advantageous for their elevated activity levels and specificity. Interest in xylanolytic enzymes has been increasing, for their possible application in many biotechnological processes. This fact has driven the isolation, purification and characterization of several β-xylosidases. In this review, the mechanisms of action, substrate specificities, physicochemical characteristics, regulation at molecular level, molecular cloning and classification of filamentous fungal β-xylosidases are described. The potential industrial applications of fungal β-xylosidases will also be presented.  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