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   820748篇
  免费   88687篇
  国内免费   508篇
  2018年   7685篇
  2016年   10249篇
  2015年   14549篇
  2014年   16416篇
  2013年   23733篇
  2012年   26833篇
  2011年   26668篇
  2010年   17621篇
  2009年   15903篇
  2008年   23580篇
  2007年   24146篇
  2006年   22803篇
  2005年   21871篇
  2004年   21394篇
  2003年   20527篇
  2002年   19866篇
  2001年   34680篇
  2000年   35166篇
  1999年   28412篇
  1998年   10005篇
  1997年   10363篇
  1996年   9760篇
  1995年   9185篇
  1994年   9194篇
  1993年   9046篇
  1992年   23320篇
  1991年   22416篇
  1990年   22061篇
  1989年   21648篇
  1988年   20157篇
  1987年   19135篇
  1986年   17962篇
  1985年   18153篇
  1984年   14919篇
  1983年   12958篇
  1982年   10071篇
  1981年   9210篇
  1980年   8656篇
  1979年   14505篇
  1978年   11458篇
  1977年   10405篇
  1976年   9947篇
  1975年   10974篇
  1974年   11763篇
  1973年   11691篇
  1972年   10678篇
  1971年   9667篇
  1970年   8403篇
  1969年   8132篇
  1968年   7409篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
A patient with chronic anemia is presented who radiologically showed prominent rugae of the stomach. Angiography demonstrated an arteriovenous malformation with a large feeding artery and prominent draining veins.  相似文献   
2.
3.
4.
5.
6.
7.
The discovery that the single p53 gene encodes several different p53 protein isoforms has initiated a flurry of research into the function and regulation of these novel p53 proteins. Full-length p53 protein level is primarily regulated by the E3-ligase Mdm2, which promotes p53 ubiquitination and degradation. Here, we report that all of the novel p53 isoforms are ubiquitinated and degraded to varying degrees in an Mdm2-dependent and -independent manner, and that high-risk human papillomavirus can degrade some but not all of the novel isoforms, demonstrating that full-length p53 and the p53 isoforms are differentially regulated. In addition, we provide the first evidence that Mdm2 promotes the NEDDylation of p53β. Altogether, our data indicates that Mdm2 can distinguish between the p53 isoforms and modify them differently.  相似文献   
8.
Comparison of bone marrow extracellular matrices.   总被引:1,自引:0,他引:1  
We have compared the structure and composition of adult and fetal bovine bone marrow extracellular matrices. In contrast to fetal bone marrow, adult bone marrow has more oval fenestration and accumulation of adipocytes as well as lower protein content. These differences could be due to remodeling of bone marrow tissue as it develops. Zymogram analysis of matrix metalloproteinase (MMP) and tissue inhibitor of MMP (TIMP) activities showed that fetal, but not adult bone marrow extract contained a 96-kDa MMP and TIMP-1 and -2. These activities may contribute to the structural differences between adult and fetal bone marrow tissues.  相似文献   
9.
Random amplified polymorphic DNA (RAPD) analysis was used tostudy variation among and within selectedIxora (Rubiaceae) populationsand mutants. Six populations of I. congesta yielded identicalbanding patterns suggesting genetic uniformity of this species.However, six populations of I. coccinea varieties (three red-flowered,two yellow-flowered and one red-flowered wild-type) exhibitedinfraspecific differences in RAPD profiles. Small and largeleaves of an atavistic mutant cultivar of I. coccinea were alsosubjected to RAPD analysis. An extra band was amplified in thelarge leaves that was absent in small leaves, suggesting thatthe phenotypic alteration in this taxon is due to genetic mutationrather than epigenetic changes. Similarly, an extra band wasdetected in the white sectors of I. Variegated compared to thegreen sectors, suggesting that the shoot apical meristems ofthis cultivar exist as a genetic chimera. DNA gel blot hybridizationwas performed to confirm the specificities of selected bands.Our study indicates that differences among individuals of variouspopulations and mutants may be detected using RAPD markers.Copyright 1999 Annals of Botany Company Ixora L., variegated variety, RAPD fingerprinting, DNA gel blot, intraspecific genetic similarity, atavistic mutant.  相似文献   
10.
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