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   111178篇
  免费   6593篇
  国内免费   15篇
  2023年   621篇
  2021年   1243篇
  2020年   1155篇
  2019年   1129篇
  2018年   3017篇
  2017年   2648篇
  2016年   3610篇
  2015年   4833篇
  2014年   4947篇
  2013年   6611篇
  2012年   7696篇
  2011年   6828篇
  2010年   4501篇
  2009年   3312篇
  2008年   5423篇
  2007年   5184篇
  2006年   5161篇
  2005年   4331篇
  2004年   4287篇
  2003年   3869篇
  2002年   3544篇
  2001年   2716篇
  2000年   2601篇
  1999年   2001篇
  1998年   873篇
  1997年   625篇
  1996年   661篇
  1995年   610篇
  1992年   1254篇
  1991年   1141篇
  1990年   1087篇
  1989年   1145篇
  1988年   985篇
  1987年   983篇
  1986年   907篇
  1985年   957篇
  1984年   797篇
  1983年   692篇
  1982年   577篇
  1979年   857篇
  1978年   610篇
  1977年   598篇
  1975年   698篇
  1974年   762篇
  1973年   733篇
  1972年   671篇
  1971年   608篇
  1970年   657篇
  1969年   728篇
  1968年   684篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Analogs of deamino-oxytocin and deamino-oxypressin containing a CH2-NH group instead of an amide bond between positions 8 and 9 were synthesized. All tested compounds exhibit significantly lowered biological activities.  相似文献   
72.
73.
74.
75.
Hepatitis E virus (HEV) is a single-strand positive-sense RNA virus in the family Hepeviridae. The disease caused by HEV, hepatitis E, is an important public health problem in developing countries of Asia and Africa and is also endemic in many industrialized countries, including the United States. HEV has been identified from several other animal species in addition to humans, including the pig, chicken, mongoose, deer, rabbit, ferret, bat, and fish. Here we report the complete genome sequence of the first strain of HEV from rabbits in the United States. Sequence and phylogenetic analyses revealed that the U.S. rabbit HEV is a distant member of the zoonotic genotype 3 HEV, thus raising a concern for potential zoonotic human infection. A unique 90-nucleotide insertion within the X domain of the ORF1 was identified in the rabbit HEV, and this insertion may play a role in the species tropism of HEV.  相似文献   
76.
The in vitro determination of the effects of some pharmacological agents on the outer diameter and axial tension of human Fallopian tube ampullar segments showed that some drugs may act on the circular and longitudinal smooth muscle layers relatively separately. PGF2 alpha elicited an excitatory response in both muscle layers while norepinephrine and isoproterenol decreased the activity. Oxytocin and indomethacin had relatively limited effects on the spontaneous motility of the ampullar segments. The calcium antagonist verapamil inhibited the spontaneous periodic activity.  相似文献   
77.
78.
79.
A strain of 1,507 typised donors enables 15.97 average donors to be selected for a thrombocyte transfusion in one of 75 patients selected at random with HLA antibodies being previously determined (1 to 66 donors per patient). HLA compatible donors were found for 72 patients (97.33 per cent). More than 5 HLA compatible donors could be found for 58 patients. The high number of compatible donors is based on the fact that among 1,507 donors there were 156 HLA homozygotes and 556 donors with 3 HLA-A or B-antigens respectively. Compatibility in the ABO-system was not taken into account.  相似文献   
80.
Lateral membrane heterogeneity, in the form of lipid rafts and microdomains, is currently implicated in cell processes including signal transduction, endocytosis, and cholesterol trafficking. Various biophysical techniques have been used to detect and characterize lateral membrane domains. Among these, Förster resonance energy transfer (FRET) has the crucial advantage of being sensitive to domain sizes smaller than 50-100 nm, below the resolution of optical microscopy but, apparently, similar to those of rafts in cell membranes. In the last decade, several formalisms for the analysis of FRET in heterogeneous membrane systems have been derived and applied to the study of microdomains. They are critically described and illustrated here.  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