首页 | 官方网站   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   1001544篇
  免费   107021篇
  国内免费   425篇
生物科学   1108990篇
  2018年   9196篇
  2016年   12527篇
  2015年   16354篇
  2014年   19409篇
  2013年   28083篇
  2012年   31348篇
  2011年   32153篇
  2010年   22035篇
  2009年   20456篇
  2008年   28814篇
  2007年   29994篇
  2006年   28124篇
  2005年   27215篇
  2004年   26794篇
  2003年   26073篇
  2002年   25393篇
  2001年   41505篇
  2000年   41012篇
  1999年   33244篇
  1998年   12612篇
  1997年   12797篇
  1996年   12292篇
  1995年   11359篇
  1994年   11073篇
  1993年   11148篇
  1992年   27632篇
  1991年   27175篇
  1990年   26537篇
  1989年   26047篇
  1988年   24055篇
  1987年   23286篇
  1986年   21591篇
  1985年   21770篇
  1984年   17951篇
  1983年   15823篇
  1982年   12187篇
  1981年   11221篇
  1980年   10421篇
  1979年   17284篇
  1978年   13638篇
  1977年   12536篇
  1976年   12008篇
  1975年   13265篇
  1974年   14350篇
  1973年   14119篇
  1972年   12934篇
  1971年   11642篇
  1970年   10257篇
  1969年   10112篇
  1968年   8858篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
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   
5.
6.
7.
Conventional therapies for prostate cancer, especially in its androgen-independent form, may result in the survival of small populations of resistant cells with tumor-initiating potential. These “cancer stem cells” are believed to be responsible for cancer relapse, and therapeutic strategies targeting these cells are of great importance. Telomerase is a ribonucleoprotein enzyme responsible for telomere elongation and is activated in the majority of malignancies, including prostate cancer, but is absent in most normal cells. Putative tumor-initiating cells have significant levels of telomerase, indicating that they are an excellent target for telomerase inhibition therapy. In this review, we present some evidence for the hypothesis that conventional therapies (standard chemotherapy and/or radiation therapy) in combination with telomerase inhibitors may result in effective and more durable responses.  相似文献   
8.
9.
The alga Analipus japonicus (Harv.) Wynne displays a distinct seasonal pattern in its development in Peter the Great Bay (Sea of Japan). In winter and spring, it occurs only in the form of basal crusts, and vertical axes develop in the summer–autumn period. It reproduces mostly asexually from July to November. Algae with unilocular sporangia occur very seldom, only in June and July.  相似文献   
10.
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   
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-23

京公网安备 11010802026262号