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   13425篇
  免费   810篇
  国内免费   7篇
  2023年   116篇
  2022年   134篇
  2021年   225篇
  2020年   206篇
  2019年   217篇
  2018年   325篇
  2017年   331篇
  2016年   474篇
  2015年   554篇
  2014年   630篇
  2013年   874篇
  2012年   984篇
  2011年   933篇
  2010年   578篇
  2009年   515篇
  2008年   696篇
  2007年   650篇
  2006年   650篇
  2005年   561篇
  2004年   550篇
  2003年   484篇
  2002年   460篇
  2001年   237篇
  2000年   184篇
  1999年   164篇
  1998年   95篇
  1997年   88篇
  1996年   66篇
  1995年   71篇
  1994年   63篇
  1993年   62篇
  1992年   109篇
  1991年   85篇
  1990年   103篇
  1989年   114篇
  1988年   96篇
  1987年   65篇
  1986年   88篇
  1985年   103篇
  1983年   63篇
  1982年   61篇
  1979年   92篇
  1978年   64篇
  1977年   59篇
  1974年   83篇
  1973年   78篇
  1970年   69篇
  1969年   65篇
  1968年   61篇
  1967年   57篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Studies on actin-actin and actin-myosin interaction   总被引:4,自引:0,他引:4  
  相似文献   
113.
114.
115.
Penetration of thymocytes into the blood circulation   总被引:2,自引:0,他引:2  
  相似文献   
116.
Mycelium of white-rot fungi secretes laccase into the medium. It was found by cultivation on malt-agar plates that the mycelium does not produce laccase equally in all its parts. The youngest hyphae at the margins of the colony represent usually the maximum producers, whereas older hyphae produce less or none at all. An exception here isCollybia velutipes which is the weakest producer of laccase of all the fungi studied and where only the older hyphae begin to secrete it. Manometric estimation of laccase showed that maximum specific activity of laccase is achieved at the boundary between the phases of initial and linear growth and i11 some cases during the first half of linear growth. Ageing of the mycelium characterized by certain changes in its metabolism is reflected in changes of enzyme production by fungal hypha of different age.  相似文献   
117.
The existence of six amylase heterogeneity variants in serum and urine has been discovered in a group of 111 families with twins, and the frequence of each variant was determined. It had been shown that each of these amylase heterogeneity variants is inherited codominantly, and the mode of inheritance is demonstrated schematically.These amylase heterogeneity variants may be used as an aid to twin zygosity determination and also in paternity problems.  相似文献   
118.
T. Zsotér  R. F. P. Cronin 《CMAJ》1966,94(25):1293-1297
Forearm veins were studied to determine whether patients with primary varicosity of the saphenous veins had a generalized abnormality of the venous system. Distensibility of the superficial forearm and hand veins was measured in 25 patients with varicosity of the saphenous veins, and in 25 control subjects. Patients with saphenous varicosity had a significantly greater distensibility of the undistorted forearm veins than control subjects. Hysteresis of distensibility curves was more prnounced in patients with varicosity than in control subjects; mean hysteresis index was 0.65 ± 0.06 versus 0.28 ± 0.02 in controls. These investigations suggest that an increased distensibility of the venous system is the predisposing factor in the development of varicose veins.  相似文献   
119.
The work is concerned with the question of the effect of humic acids on the biological action of agropyrene, the effective substance from the rootstock of Agropyron repens (L.) P. BEAUV. The test organism was the alga Scenedesmus obliquus (TURP.) KRÜGER, cultivated in mineral solution. The basic biological test was the determination of the number and size of the cells of this alga. It was found that the way in which agropyrene acts on combined application with humus acids depends on which humus fraction is used. It can display a synergic action if humic acid is used, since this substance probably facilitates the penetration of agropyrene into the cells. On the other hand, fulvic acid counteracts the activity of agropyrene and this most probably by mutual binding and blocking of active groups and links.  相似文献   
120.
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