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   26637篇
  免费   46篇
  国内免费   103篇
系统科学   152篇
丛书文集   363篇
教育与普及   66篇
理论与方法论   103篇
现状及发展   11748篇
研究方法   1202篇
综合类   12751篇
自然研究   401篇
  2013年   195篇
  2012年   420篇
  2011年   818篇
  2010年   167篇
  2009年   146篇
  2008年   453篇
  2007年   534篇
  2006年   516篇
  2005年   527篇
  2004年   521篇
  2003年   484篇
  2002年   470篇
  2001年   830篇
  2000年   783篇
  1999年   562篇
  1992年   484篇
  1991年   398篇
  1990年   430篇
  1989年   400篇
  1988年   399篇
  1987年   434篇
  1986年   400篇
  1985年   512篇
  1984年   404篇
  1983年   346篇
  1982年   316篇
  1981年   308篇
  1980年   390篇
  1979年   874篇
  1978年   669篇
  1977年   663篇
  1976年   523篇
  1975年   597篇
  1974年   770篇
  1973年   702篇
  1972年   720篇
  1971年   817篇
  1970年   1047篇
  1969年   796篇
  1968年   725篇
  1967年   785篇
  1966年   671篇
  1965年   453篇
  1959年   253篇
  1958年   450篇
  1957年   330篇
  1956年   284篇
  1955年   237篇
  1954年   219篇
  1948年   196篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Retrograde transport of endocytosed Shiga toxin to the endoplasmic reticulum.   总被引:39,自引:0,他引:39  
K Sandvig  O Garred  K Prydz  J V Kozlov  S H Hansen  B van Deurs 《Nature》1992,358(6386):510-512
Shiga toxin and some other protein toxins that act on targets in the cytosol have previously been shown to enter the trans-Golgi network. Transport by this route may be necessary for translocation of the toxin to the cytosol and for intoxication, but it is not known whether the enzymatically active part of the toxins actually enters the cytosol from the trans-Golgi network. It has been suggested that such toxins are transported in a retrograde manner to the endoplasmic reticulum and that translocation occurs in this organelle, but retrograde transport of endocytosed material beyond the trans-Golgi network has never been demonstrated. Here we show that in butyric acid-treated A431 cells endocytosed Shiga toxin is not only transported to the trans-Golgi network, but also to all Golgi stacks, to the endoplasmic reticulum and to the nuclear envelope. Furthermore, butyric acid sensitizes the cells to Shiga toxin, which is consistent with the possibility that retrograde transport is required for translocation of the toxin to the cytosol.  相似文献   
23.
S J Weintraub  C A Prater  D C Dean 《Nature》1992,358(6383):259-261
  相似文献   
24.
25.
1 Introduction   Nanoscale science and technology have attracted greatattention since the novel properties become dominant for well-known materials as their sizes reduced to some critical dimension. These properties frequently originate in lattice distortions, structure transformations etc[1]. The variations of size and structure ofnanocrystals lead to the change of their electronic structures. Very recently, nanoscale materials with different electronic structures were utilized in fabricating nanoscale junctions[2].   ……  相似文献   
26.
27.
Obese postmenopausal female volunteers were given timed daily oral dosages of bromocriptine, and tested for reduction of body fat stores. This dopamine agonist has been shown to reset circadian rhythms that are altered in obese animals and to reduce body fat levels in several animal models. The participants were instructed not to alter their existing exercise and eating behavior during treatment. Skinfold measurements were taken on 33 subjects as indices of body fat. The measurements (e.g., suprailiac) were reduced after six weeks by about 25%, which represents a reduction of 11.7% of the total body fat. These dramatic decreases in body fat, which are equivalent to that produced by severe caloric restriction, were accompanied by more modest reductions of body weight (2.5%), indicating a possible conservation of protein that is usually lost as a consequence of such caloric restriction. The effects of bromocriptine treatment on body fat and hyperglycemia were also examined in non-insulin dependent diabetics being treated with oral hypoglycemics (7 subjects) or insulin (7 subjects). Total body fat was reduced by 10.7% and 5.1% in diabetics on oral hypoglycemics and insulin, respectively, without any significant reductions in body weight. Hyperglycemia was reduced in most of the 15 diabetic subjects treated leading to euglycemia and even cessation of hypoglycemic drugs in 3 of the 7 subjects during 4-8 weeks of bromocriptine treatment. These findings support the hypothesis that obesity and type II diabetes may be treated effectively with bromocriptine when administered at the proper times and dosages.  相似文献   
28.
DNA fingerprinting transforms the art of cell authentication.   总被引:4,自引:0,他引:4  
G N Stacey  B J Bolton  A Doyle 《Nature》1992,357(6375):261-262
The increasing diversity of new cell cultures is seriously stretching the capabilities of traditional methods of identification. DNA fingerprinting is set to play an important role in increasing confidence in the authenticity of cultures in research and industry.  相似文献   
29.
We recently reported on a linkage study within a Quarter Horse lineage segregating hyperkalaemic periodic paralysis (HYPP), an autosomal dominant condition showing potassium-induced attacks of skeletal muscle paralysis. HYPP co-segregated with the equine adult skeletal muscle sodium channel alpha subunit gene, the same gene that causes human HYPP. We now describe the Phe to Leu mutation in transmembrane domain IVS3 which courses the horse disease. This represents the first application of molecular genetics to an important horse disease, and the data will provide an opportunity for control or eradication of this condition.  相似文献   
30.
本文根据浙江省教委、省基金、舟山市科委关于浙江沿海虾蛄生物学及其开发利用研究的要求,对四年多来的研究进行总结,主要包括资源与分布、生物学习性、暂养及运输技术、营养成份分析、开发利用等诸方面  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