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   205篇
  免费   0篇
  国内免费   2篇
系统科学   1篇
丛书文集   2篇
教育与普及   1篇
理论与方法论   2篇
现状及发展   81篇
研究方法   26篇
综合类   93篇
自然研究   1篇
  2017年   1篇
  2016年   4篇
  2015年   3篇
  2014年   2篇
  2013年   2篇
  2012年   16篇
  2011年   18篇
  2010年   7篇
  2008年   16篇
  2007年   8篇
  2006年   9篇
  2005年   8篇
  2004年   10篇
  2003年   7篇
  2002年   6篇
  2001年   2篇
  2000年   2篇
  1999年   3篇
  1996年   1篇
  1994年   1篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1988年   2篇
  1985年   1篇
  1984年   1篇
  1980年   1篇
  1979年   3篇
  1978年   4篇
  1977年   6篇
  1976年   3篇
  1975年   5篇
  1974年   5篇
  1973年   2篇
  1972年   3篇
  1971年   2篇
  1970年   6篇
  1969年   2篇
  1968年   4篇
  1967年   3篇
  1966年   4篇
  1965年   5篇
  1958年   3篇
  1957年   1篇
  1956年   1篇
  1955年   2篇
  1954年   3篇
  1947年   3篇
  1946年   1篇
  1945年   1篇
排序方式: 共有207条查询结果,搜索用时 15 毫秒
11.
Ewing sarcoma, a pediatric tumor characterized by EWSR1-ETS fusions, is predominantly observed in populations of European ancestry. We performed a genome-wide association study (GWAS) of 401 French individuals with Ewing sarcoma, 684 unaffected French individuals and 3,668 unaffected individuals of European descent and living in the United States. We identified candidate risk loci at 1p36.22, 10q21 and 15q15. We replicated these loci in two independent sets of cases and controls. Joint analysis identified associations with rs9430161 (P = 1.4 × 10(-20); odds ratio (OR) = 2.2) located 25 kb upstream of TARDBP, rs224278 (P = 4.0 × 10(-17); OR = 1.7) located 5 kb upstream of EGR2 and, to a lesser extent, rs4924410 at 15q15 (P = 6.6 × 10(-9); OR = 1.5). The major risk haplotypes were less prevalent in Africans, suggesting that these loci could contribute to geographical differences in Ewing sarcoma incidence. TARDBP shares structural similarities with EWSR1 and FUS, which encode RNA binding proteins, and EGR2 is a target gene of EWSR1-ETS. Variants at these loci were associated with expression levels of TARDBP, ADO (encoding cysteamine dioxygenase) and EGR2.  相似文献   
12.
It has been four years since the original publication of the draft sequence of the rat genome. Five groups are now working together to assemble, annotate and release an updated version of the rat genome. As the prevailing model for physiology, complex disease and pharmacological studies, there is an acute need for the rat's genomic resources to keep pace with the rat's prominence in the laboratory. In this commentary, we describe the current status of the rat genome sequence and the plans for its impending 'upgrade'. We then cover the key online resources providing access to the rat genome, including the new SNP views at Ensembl, the RefSeq and Genes databases at the US National Center for Biotechnology Information, Genome Browser at the University of California Santa Cruz and the disease portals for cardiovascular disease and obesity at the Rat Genome Database.  相似文献   
13.
本文得到了拟环满足条件xy=xy ̄(n(x,y)x或xy=yx ̄(n(x,y)y的分解定理。  相似文献   
14.
15.
16.
17.
Summary The formation of the myotomes to chick embryos was studied by using experimental and scanning electron microscope techniques. With the aid of the quail-chick marker system, it was demonstrated that the dermatome gives rise to the myotome plate. SEM studies support the conclusion that the myotome cells originate only from the edges of the dermatome.Supported by the Deutsche Forschungsgemeinschaft (Ch 44/2).  相似文献   
18.
Isolation of a human teratoma cell line which expresses F9 antigen   总被引:7,自引:0,他引:7  
B Hogan  M Fellous  P Avner  F Jacob 《Nature》1977,270(5637):515-518
  相似文献   
19.
20.
The Atlantic meridional overturning circulation is widely believed to affect climate. Changes in ocean circulation have been inferred from records of the deep water chemical composition derived from sedimentary nutrient proxies, but their impact on climate is difficult to assess because such reconstructions provide insufficient constraints on the rate of overturning. Here we report measurements of 231Pa/230Th, a kinematic proxy for the meridional overturning circulation, in a sediment core from the subtropical North Atlantic Ocean. We find that the meridional overturning was nearly, or completely, eliminated during the coldest deglacial interval in the North Atlantic region, beginning with the catastrophic iceberg discharge Heinrich event H1, 17,500 yr ago, and declined sharply but briefly into the Younger Dryas cold event, about 12,700 yr ago. Following these cold events, the 231Pa/230Th record indicates that rapid accelerations of the meridional overturning circulation were concurrent with the two strongest regional warming events during deglaciation. These results confirm the significance of variations in the rate of the Atlantic meridional overturning circulation for abrupt climate changes.  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