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   276篇
  免费   0篇
  国内免费   3篇
系统科学   3篇
教育与普及   1篇
理论与方法论   3篇
现状及发展   58篇
研究方法   32篇
综合类   172篇
自然研究   10篇
  2018年   3篇
  2017年   2篇
  2016年   1篇
  2015年   1篇
  2014年   2篇
  2013年   1篇
  2012年   23篇
  2011年   24篇
  2010年   4篇
  2009年   1篇
  2008年   18篇
  2007年   12篇
  2006年   22篇
  2005年   16篇
  2004年   14篇
  2003年   10篇
  2002年   8篇
  2001年   9篇
  2000年   7篇
  1999年   5篇
  1993年   1篇
  1992年   3篇
  1991年   1篇
  1990年   6篇
  1989年   2篇
  1988年   5篇
  1986年   1篇
  1985年   4篇
  1984年   4篇
  1983年   2篇
  1982年   2篇
  1981年   4篇
  1979年   1篇
  1978年   3篇
  1977年   3篇
  1976年   3篇
  1975年   4篇
  1974年   2篇
  1973年   1篇
  1972年   2篇
  1971年   7篇
  1970年   8篇
  1969年   6篇
  1968年   3篇
  1967年   3篇
  1966年   8篇
  1965年   3篇
  1963年   1篇
  1958年   1篇
  1956年   1篇
排序方式: 共有279条查询结果,搜索用时 62 毫秒
61.
We have found that almost all paper documents, plastic cards and product packaging contain a unique physical identity code formed from microscopic imperfections in the surface. This covert 'fingerprint' is intrinsic and virtually impossible to modify controllably. It can be rapidly read using a low-cost portable laser scanner. Most forms of document and branded-product fraud could be rendered obsolete by use of this code.  相似文献   
62.
Obesity is the driving force behind the worldwide increase in the prevalence of type 2 diabetes mellitus. Hyperglycaemia is a hallmark of diabetes and is largely due to increased hepatic gluconeogenesis. The medial hypothalamus is a major integrator of nutritional and hormonal signals, which play pivotal roles not only in the regulation of energy balance but also in the modulation of liver glucose output. Bidirectional changes in hypothalamic insulin signalling therefore result in parallel changes in both energy balance and glucose metabolism. Here we show that activation of ATP-sensitive potassium (K(ATP)) channels in the mediobasal hypothalamus is sufficient to lower blood glucose levels through inhibition of hepatic gluconeogenesis. Finally, the infusion of a K(ATP) blocker within the mediobasal hypothalamus, or the surgical resection of the hepatic branch of the vagus nerve, negates the effects of central insulin and halves the effects of systemic insulin on hepatic glucose production. Consistent with these results, mice lacking the SUR1 subunit of the K(ATP) channel are resistant to the inhibitory action of insulin on gluconeogenesis. These findings suggest that activation of hypothalamic K(ATP) channels normally restrains hepatic gluconeogenesis, and that any alteration within this central nervous system/liver circuit can contribute to diabetic hyperglycaemia.  相似文献   
63.
64.
Ellis-van Creveld syndrome (EvC, MIM 225500) is an autosomal recessive skeletal dysplasia characterized by short limbs, short ribs, postaxial polydactyly and dysplastic nails and teeth. Congenital cardiac defects, most commonly a defect of primary atrial septation producing a common atrium, occur in 60% of affected individuals. The disease was mapped to chromosome 4p16 in nine Amish subpedigrees and single pedigrees from Mexico, Ecuador and Brazil. Weyers acrodental dysostosis (MIM 193530), an autosomal dominant disorder with a similar but milder phenotype, has been mapped in a single pedigree to an area including the EvC critical region. We have identified a new gene (EVC), encoding a 992-amino-acid protein, that is mutated in individuals with EvC. We identified a splice-donor change in an Amish pedigree and six truncating mutations and a single amino acid deletion in seven pedigrees. The heterozygous carriers of these mutations did not manifest features of EvC. We found two heterozygous missense mutations associated with a phenotype, one in a man with Weyers acrodental dysostosis and another in a father and his daughter, who both have the heart defect characteristic of EvC and polydactyly, but not short stature. We suggest that EvC and Weyers acrodental dysostosis are allelic conditions.  相似文献   
65.
66.
67.
H F Dylla  J H Abrams  C T Hovland  J G King 《Nature》1981,291(5814):401-404
  相似文献   
68.
69.
70.
Turnover of basic protein of rat brain   总被引:7,自引:0,他引:7  
J G Wood  N King 《Nature》1971,229(5279):56-58
  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