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   6285篇
  免费   553篇
  国内免费   12篇
  6850篇
  2024年   7篇
  2023年   65篇
  2022年   129篇
  2021年   220篇
  2020年   99篇
  2019年   161篇
  2018年   178篇
  2017年   173篇
  2016年   224篇
  2015年   326篇
  2014年   321篇
  2013年   416篇
  2012年   504篇
  2011年   459篇
  2010年   290篇
  2009年   225篇
  2008年   321篇
  2007年   325篇
  2006年   278篇
  2005年   272篇
  2004年   205篇
  2003年   183篇
  2002年   221篇
  2001年   147篇
  2000年   190篇
  1999年   129篇
  1998年   51篇
  1997年   28篇
  1996年   33篇
  1995年   46篇
  1994年   34篇
  1993年   32篇
  1992年   68篇
  1991年   58篇
  1990年   58篇
  1989年   58篇
  1988年   44篇
  1987年   33篇
  1986年   41篇
  1985年   44篇
  1984年   25篇
  1983年   21篇
  1982年   12篇
  1981年   16篇
  1980年   8篇
  1979年   15篇
  1978年   12篇
  1977年   12篇
  1976年   7篇
  1972年   6篇
排序方式: 共有6850条查询结果,搜索用时 15 毫秒
81.
Live viruses and live virus vaccines induce cellular immunity more readily than do inactivated viruses or purified proteins, but the mechanism by which this process occurs is unknown. A trivial explanation would relate to the ability of live viruses to spread and infect more cells than can inactivated virus. We have used live but replication-defective mutants to investigate this question. Our studies indicate that the immune responses of mice to live virus differ greatly from the responses to inactivated virus even when the virus does not complete a replicative cycle. Further, these studies indicate that herpes simplex virus-specific T-cell responses can be generated by infection with replication-defective mutant viruses. These data indicate that the magnitude of the cellular immunity to herpes simplex virus may be proportional to the number or quantity of different viral gene products expressed by an immunizing virus.  相似文献   
82.
83.
Cytosolic isozymes of 6-phosphogluconate dehydrogenase were purified from roots of maize (Zea mays L.). The final preparation contained two 55-kD proteins. Affinity-purified dehydrogenases from a maize line that is null for both cytosolic 6-phosphogluconate dehydrogenase isozymes (Pgd1-null, Pgd2-null) lacked the 55-kD proteins. The substrate kinetics of the purified enzyme were determined.  相似文献   
84.
The interaction between human corticosteroid binding globulin and activated leukocytes is restricted to the granulocyte population, and is characterized by specific proteolytic cleavage of corticosteroid binding globulin which markedly reduces its steroid binding activity. A direct interaction between corticosteroid binding globulin and the activated cells appears to enhance this event, and does not involve cellular internalization of corticosteroid binding globulin or its proteolytic degradation products, which resemble those obtained after incubation of corticosteroid binding globulin with neutrophil elastase. These data suggest that corticosteroid binding globulin interacts with elastase on the surface of activated neutrophils, and may promote glucocorticoid delivery to these cells during inflammation.  相似文献   
85.
Transabdominal fine needle aspiration biopsy of a solitary space-occupying lesion in the liver produced smears containing irregular bundles of smooth muscle cells with granular or fibrillary cytoplasm and slightly pleomorphic nuclei. In a few bundles, aggregates of mature fat cells were present, which is characteristic for an angiomyolipoma. Histologic examination of the resected mass showed it to be a solitary angiomyolipoma of the liver. The diagnosis was further confirmed by immunohistochemical and electron microscopic studies.  相似文献   
86.
Twenty independent man-mouse (Cl1D,LA/TK-, HPRT-) and man-hamster (CH,HPRT-) hybrids using female human cells with balanced reciprocal translocation XX,t(X;5)(q21;q11) were analyzed for human genes localized on chromosome 5 (HEXB), on chromosome X (PGK, GALA, HPRT, G6PD) and for the different chromosomes in relation with the balanced reciprocal translocation (chr.5, chr.5q-, chr.Xq+, chr.X). The different results obtained indicate that the genes for human markers HEXB, PGK are on Xq+, and that the genes for human markers GALA, G6PD are on 5q-. These data implicate finally the following localizations: HEXB on 5q11 leads to 5qter; PGK on Xq21 leads to Xpter; GALA, HPRT, G6PD on Xq21 leads to Xqter.  相似文献   
87.
88.
In order to correlate and compare the antigenic relationships observed between nine yeast strains, we have studied their major antigenic determinant represented by the mannans. This material is a constituent of their cell.The compounds that we have isolated are, in reality, glycopeptides. All their polysaccharide fractions consist of mannose only — except for those of the compounds that we have isolated of R. glutinis and C. lipolytica. All these polysaccharides have very close ramified structures; the only one that seems to be very different is that of R. glutinis, and this is in agreement with the antigenic properties of that yeast.The peptidic fractions of these glycopeptides are rich in threonine, serine and aspartic acid and it is very likely that these amino acids make the link with the polysaccharide fraction. The quantity of these amino acids seem to be affected by the conditions of culture of the yeasts, but not their presence or absence.  相似文献   
89.
90.
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