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   341489篇
  免费   37899篇
  国内免费   288篇
  379676篇
  2018年   3168篇
  2017年   2989篇
  2016年   4246篇
  2015年   5800篇
  2014年   6824篇
  2013年   9175篇
  2012年   10720篇
  2011年   10726篇
  2010年   6940篇
  2009年   6339篇
  2008年   9507篇
  2007年   9678篇
  2006年   9501篇
  2005年   9065篇
  2004年   8894篇
  2003年   8577篇
  2002年   8447篇
  2001年   18474篇
  2000年   18749篇
  1999年   14357篇
  1998年   4291篇
  1997年   4479篇
  1996年   4197篇
  1995年   3818篇
  1994年   3801篇
  1993年   3852篇
  1992年   11058篇
  1991年   10965篇
  1990年   10443篇
  1989年   10222篇
  1988年   9575篇
  1987年   8847篇
  1986年   8059篇
  1985年   7885篇
  1984年   6246篇
  1983年   5472篇
  1982年   3977篇
  1981年   3530篇
  1980年   3294篇
  1979年   5807篇
  1978年   4452篇
  1977年   4033篇
  1976年   3545篇
  1975年   4114篇
  1974年   4275篇
  1973年   4196篇
  1972年   3757篇
  1971年   3484篇
  1970年   3064篇
  1969年   3000篇
排序方式: 共有10000条查询结果,搜索用时 6 毫秒
81.
82.
83.
84.
85.
86.
The recent identification of VKORC1 has made important contributions to our understanding of the vitamin K cycle. The VKORC1 enzyme was shown to be the molecular target of coumarin drugs. Mutations and polymorphisms in coding and noncoding regions of the VKORC1 gene have been shown to cause both a partial to total coumarin resistance and coumarin sensitivity. Availability of molecular diagnostics (VKORC1, CYP2C9) and drug monitoring by HCPLC (determination of coumarin, vitamin K, and vitamin K epoxide levels) is helpful for detecting hereditary and acquired factors influencing coumarin therapy. In the future, these tools may be instrumental in designing individualized oral anticoagulation therapy regimens.  相似文献   
87.
Two new species of carcharhinid sharks from the Late Eocene deposits (Tavda Formation) of the southern Trans-Urals, Abdounia vassilyevae sp. nov., previously determined as A. aff. beaugei, and A. lata sp. nov., are described. To date, up to five Priabonian species of Abdounia have been recorded. New finds supplement the data on diversity, evolution, and paleobiogeography of Abdounia.  相似文献   
88.
89.
In this paper very simple nonparametric classification rule for mixtures of discrete and continuous random variables is described. It is based on the method of nearest neighbor proposed by Cover and Hart (1967). The bounds on the limit of the nearest neighbor rule risks are given. Both lower and upper bound depend on the Bayes risk and the loss function. Finally the method is compared with other existing methods on some practical data set.  相似文献   
90.
Increasing evidence suggests that apolipoprotein D (apoD) could play a major role in mediating neuronal degeneration and regeneration in the CNS and the PNS. To investigate further the temporal pattern of apoD expression after experimental traumatic brain injury in the rat, male Sprague-Dawley rats were subjected to unilateral cortical impact injury. The animals were killed and examined for apoD mRNA and protein expression and for immunohistological analysis at intervals from 15 min to 14 days after injury. Increased apoD mRNA and protein levels were seen in the cortex and hippocampus ipsilateral to the injury site from 48 h to 14 days after the trauma. Immunohistological investigation demonstrated a differential pattern of apoD expression in the cortex and hippocampus, respectively: Increased apoD immunoreactivity in glial cells was detected from 2 to 3 days after the injury in cortex and hippocampus. In contrast, increased expression of apoD was seen in cortical and hippocampal neurons at later time points following impact injury. Concurrent histopathological examination using hematoxylin and eosin demonstrated dark, shrunken neurons in the cortex ipsilateral to the injury site. In contrast, no evidence of cell death was observed in the hippocampus ipsilateral to the injury site up to 14 days after the trauma. No evidence of increased apoD mRNA or protein expression or neuronal pathology by hematoxylin and eosin staining was detected in the contralateral cortex and hippocampus. Our results reveal induction of apoD expression in the cortex and hippocampus following traumatic brain injury in the rat. Our data also suggest that increased apoD expression may play an important role in cortical neuronal degeneration after brain injury in vivo. However, increased expression of apoD in the hippocampus may not necessarily be indicative of neuronal death.  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