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   15762篇
  免费   1269篇
  国内免费   6篇
  17037篇
  2022年   65篇
  2021年   128篇
  2020年   95篇
  2019年   109篇
  2018年   244篇
  2017年   284篇
  2016年   393篇
  2015年   552篇
  2014年   604篇
  2013年   834篇
  2012年   1134篇
  2011年   1142篇
  2010年   680篇
  2009年   575篇
  2008年   972篇
  2007年   990篇
  2006年   928篇
  2005年   914篇
  2004年   786篇
  2003年   716篇
  2002年   691篇
  2001年   295篇
  2000年   328篇
  1999年   271篇
  1998年   165篇
  1997年   115篇
  1996年   123篇
  1995年   111篇
  1994年   112篇
  1993年   106篇
  1992年   148篇
  1991年   139篇
  1990年   105篇
  1989年   140篇
  1988年   123篇
  1987年   105篇
  1986年   80篇
  1985年   113篇
  1984年   108篇
  1983年   106篇
  1982年   91篇
  1981年   100篇
  1980年   85篇
  1979年   90篇
  1978年   65篇
  1977年   64篇
  1976年   91篇
  1975年   78篇
  1974年   95篇
  1973年   61篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
Sydney Parkinson, aged 18, was Sir Joseph Banks' private assistant and artist on Captain Cook's first voyage around the world. Parkinson died on the voyage. Among his effects delivered to his brother Stanfield were drawings and notes which the latter published as a journal. Included in it is a chapter on the economic plants of Tahiti, and most of them are given scientific names, some of which were new. In 1941 Fosberg adopted two of them to form names which were new combinations under Artocarpus , and Inocarpus . The writer now indicates that Parkinson's names of 1773 were mononomials, hence invalid, but that in the German edition of 1774, edited by Herr "Z", the names are valid binomials. For the two plants mentioned, the authorship of the combinations is revised.  相似文献   
23.
Ted St. Godard 《CMAJ》2004,171(3):262-264
  相似文献   
24.
[Acyl CoA]monoacylglycerol acyltransferase 2 (MGAT2) is of interest as a target for therapeutic treatment of diabetes, obesity and other diseases which together constitute the metabolic syndrome. In this Letter we report our discovery and optimisation of a novel series of MGAT2 inhibitors. The development of the SAR of the series and a detailed discussion around some key parameters monitored and addressed during the lead generation phase will be given. The in vivo results from an oral lipid tolerance test (OLTT) using the MGAT2 inhibitor (S)-10, shows a significant reduction (68% inhibition relative to na?ve, p <0.01) in plasma triacylglycerol (TAG) concentration.  相似文献   
25.
The reptile fauna of Romania comprises 23 species, out of which 12 species reach here the limit of their geographic range. We compiled and updated a national database of the reptile species occurrences from a variety of sources including our own field surveys, personal communication from specialists, museum collections and the scientific literature. The occurrence records were georeferenced and stored in a geodatabase for additional analysis of their spatial patterns. The spatial analysis revealed a biased sampling effort concentrated in various protected areas, and deficient in the vast agricultural areas of the southern part of Romania. The patterns of species richness showed a higher number of species in the warmer and drier regions, and a relatively low number of species in the rest of the country. Our database provides a starting point for further analyses, and represents a reliable tool for drafting conservation plans.  相似文献   
26.
27.
28.
Abstract. The development of peroxisomes and expression of their enzymes were investigated in differentiating intestinal epithelial cells during their migration along the crypt-villus axis. Sequential cell populations harvested by a low-temperature method were identified by microscopy, determination of alkaline phosphatase and sucrase activities and incorporation of [3H]-thymidine into DNA. Ultrastructural cytochemistry after staining for catalase activity, revealed the presence of peroxisomes in undifferentiated stem cells located in the crypt region. Morphometry indicated that the number of these organelles increased as intestinal epithelial cells differentiate. Catalase activity was higher in the crypt cells than in the mature enterocytes harvested from villus tips. On the other hand, an increasing gradient of activity was observed from crypts to villus tips for peroxisomal oxidases, i.e. fatty acyl coA oxidase, D-amino acid oxidase and polyamine oxidase. These findings indicate that biogenesis of peroxisomes occurs during migration of intestinal epithelial cells along the crypt-villus axis and that peroxisomal oxidases contribute substantially to the biochemical maturation of enterocytes.  相似文献   
29.
30.
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