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   22419篇
  免费   2835篇
  国内免费   11篇
  2021年   291篇
  2019年   223篇
  2018年   275篇
  2017年   241篇
  2016年   408篇
  2015年   649篇
  2014年   791篇
  2013年   1047篇
  2012年   1155篇
  2011年   1171篇
  2010年   720篇
  2009年   684篇
  2008年   978篇
  2007年   987篇
  2006年   862篇
  2005年   840篇
  2004年   860篇
  2003年   862篇
  2002年   809篇
  2001年   591篇
  2000年   559篇
  1999年   504篇
  1998年   323篇
  1997年   287篇
  1996年   269篇
  1995年   267篇
  1994年   258篇
  1993年   236篇
  1992年   411篇
  1991年   378篇
  1990年   399篇
  1989年   346篇
  1988年   328篇
  1987年   344篇
  1986年   317篇
  1985年   334篇
  1984年   277篇
  1983年   254篇
  1982年   234篇
  1981年   226篇
  1980年   190篇
  1979年   303篇
  1978年   258篇
  1977年   204篇
  1976年   191篇
  1975年   192篇
  1974年   218篇
  1973年   191篇
  1972年   202篇
  1969年   178篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
The synthesis of a 5'-O-BzH-2'-O-ACE-protected-3-methyluridine phosphoramidite is reported [BzH, benzhydryloxy-bis(trimethylsilyloxy)silyl; ACE, bis(2-acetoxyethoxy)methyl]. The phosphoramidite was employed in solid-phase RNA synthesis to generate a series of RNA hairpins containing single or multiple modifications, including the common nucleoside pseudouridine. Three 19-nucleotide hairpin RNAs that represent the 1920-loop region (G(1906)-C(1924)) of Escherichia coli 23S ribosomal RNA were generated. Modifications were present at positions 1911, 1915, and 1917. The stabilities and structures of the three RNAs were examined by using thermal melting, circular dichroism, and NMR spectroscopy  相似文献   
33.
34.
Development and Phase 3 testing of the most advanced malaria vaccine, RTS,S/AS01, indicates that malaria vaccine R&D is moving into a new phase. Field trials of several research malaria vaccines have also confirmed that it is possible to impact the host-parasite relationship through vaccine-induced immune responses to multiple antigenic targets using different platforms. Other approaches have been appropriately tested but turned out to be disappointing after clinical evaluation. As the malaria community considers the potential role of a first-generation malaria vaccine in malaria control efforts, it is an apposite time to carefully document terminated and ongoing malaria vaccine research projects so that lessons learned can be applied to increase the chances of success for second-generation malaria vaccines over the next 10 years. The most comprehensive resource of malaria vaccine projects is a spreadsheet compiled by WHO thanks to the input from funding agencies, sponsors and investigators worldwide. This spreadsheet, available from WHO's website, is known as "the rainbow table". By summarizing the published and some unpublished information available for each project on the rainbow table, the most comprehensive review of malaria vaccine projects to be published in the last several years is provided below.  相似文献   
35.
Abstract: Analysis of the cell-free translation products of polysomes isolated from fetal brain and other organs indicates that elevation of maternal body temperature induces the synthesis of a heat shock protein of molecular weight 74,000 (74K). The newborn mammal is particularly sensitive to induction of the 74K protein. As early postnatal development proceeds, higher body temperatures are required to induce synthesis of the 74K heat shock protein.  相似文献   
36.
Making the grade     
C. J. Brown 《CMAJ》1998,159(9):1078
  相似文献   
37.
38.
False Images     
  相似文献   
39.
40.
Studies in animals and tissue culture have shown the importance of prolactin and growth hormone in regulating renal 1 alpha-hydroxylase activity and plasma concentrations of 1,25-dihydroxycholecalciferol (1,25(OH)2D3). Evidence for a similar role for these hormones in man was sought by using a radioreceptor assay to measure plasma 1,25(OH)2D3 concentrations in 20 normal subjects, 12 patients receiving dialysis, 11 patients with primary hyperparathyroidism, 10 pregnant women, seven women with prolactinoma, and 14 patients with acromegaly. Circulating 1,25(OH)2D3 concentrations were appreciably raised in the patients with primary hyperparathyroidism and the pregnant women (P less than 0.001), slightly but significantly increased in the patients with prolactinoma (P less than 0.05), and greatly raised in those with acromegaly (P less than 0.001). These results suggest that prolactin and growth hormone are important regulators of renal vitamin D metabolism in the physiological conditions of pregnancy, lactation, and growth in man.  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