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   335165篇
  免费   3779篇
  国内免费   1023篇
电工技术   5586篇
综合类   2472篇
化学工业   46263篇
金属工艺   17609篇
机械仪表   14040篇
建筑科学   7920篇
矿业工程   2485篇
能源动力   6769篇
轻工业   21109篇
水利工程   4182篇
石油天然气   5673篇
武器工业   8篇
无线电   36928篇
一般工业技术   70304篇
冶金工业   45023篇
原子能技术   6245篇
自动化技术   47351篇
  2021年   1681篇
  2019年   1631篇
  2018年   22162篇
  2017年   21773篇
  2016年   15255篇
  2015年   2829篇
  2014年   3436篇
  2013年   9375篇
  2012年   9973篇
  2011年   22128篇
  2010年   19338篇
  2009年   17111篇
  2008年   17765篇
  2007年   20362篇
  2006年   5897篇
  2005年   9591篇
  2004年   7753篇
  2003年   7388篇
  2002年   5659篇
  2001年   4875篇
  2000年   4890篇
  1999年   4840篇
  1998年   11479篇
  1997年   8205篇
  1996年   6503篇
  1995年   4744篇
  1994年   4363篇
  1993年   4163篇
  1992年   3294篇
  1991年   3149篇
  1990年   2909篇
  1989年   2996篇
  1988年   2868篇
  1987年   2433篇
  1986年   2343篇
  1985年   2754篇
  1984年   2532篇
  1983年   2371篇
  1982年   2110篇
  1981年   2226篇
  1980年   2041篇
  1979年   2149篇
  1978年   2132篇
  1977年   2376篇
  1976年   3193篇
  1975年   1840篇
  1974年   1765篇
  1973年   1773篇
  1972年   1449篇
  1971年   1344篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
Sequencing of rice genome has facilitated the understanding of rice evolution and has been utilized extensively for mining of DNA markers to facilitate marker-assisted breeding. Simple sequence repeat (SSR) markers that are tandemly repeated nucleotide sequence motifs flanked by unique sequences are presently the maker of choice in rice improvement due to their abundance, co-dominant inheritance, high levels of allelic diversity, and simple reproducible assay. The current level of genome coverage by SSR markers in rice is sufficient to employ them for genotype identification and marker-assisted selection in breeding for mapping of genes and quantitative trait loci analysis. This review provides comprehensive information on the mapping and applications of SSR markers in investigation of rice cultivars to study their genetic divergence and marker-assisted selection of important agronomic traits.  相似文献   
33.
Ischemic and hemorrhagic strokes are associated with severe functional disability and high mortality. Except for recombinant tissue plasminogen activator, therapies targeting the underlying pathophysiology of central nervous system (CNS) ischemia and hemorrhage are strikingly lacking. Sur1-regulated channels play essential roles in necrotic cell death and cerebral edema following ischemic insults, and in neuroinflammation after hemorrhagic injuries. Inhibiting endothelial, neuronal, astrocytic and oligodendroglial sulfonylurea receptor 1–transient receptor potential melastatin 4 (Sur1–Trpm4) channels and, in some cases, microglial KATP (Sur1–Kir6.2) channels, with glibenclamide is protective in a variety of contexts. Robust preclinical studies have shown that glibenclamide and other sulfonylurea agents reduce infarct volumes, edema and hemorrhagic conversion, and improve outcomes in rodent models of ischemic stroke. Retrospective studies suggest that diabetic patients on sulfonylurea drugs at stroke presentation fare better if they continue on drug. Additional laboratory investigations have implicated Sur1 in the pathophysiology of hemorrhagic CNS insults. In clinically relevant models of subarachnoid hemorrhage, glibenclamide reduces adverse neuroinflammatory and behavioral outcomes. Here, we provide an overview of the preclinical studies of glibenclamide therapy for CNS ischemia and hemorrhage, discuss the available data from clinical investigations, and conclude with promising preclinical results that suggest glibenclamide may be an effective therapeutic option for ischemic and hemorrhagic stroke.  相似文献   
34.
35.
36.
Morozov  Yu. D.  Pemov  I. F.  Matrosov  M. Yu.  Zin’ko  B. F. 《Metallurgist》2020,63(9-10):933-950
Metallurgist - We consider domestic and foreign standards for rolled metals used in bridge building. Domestic standards contain elevated requirements to the reliability of rolled metals in terms of...  相似文献   
37.
Russian Journal of Non-Ferrous Metals - This article is devoted to the influence of sodium lignosulfonate (SL), anionic surfactants (sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate...  相似文献   
38.
39.
40.
Potential mGAT4 inhibitors derived from the lead substance (S)-SNAP-5114 have been synthesized and characterized for their inhibitory potency. Variations from the parent compound included the substitution of one of its aromatic 4-methoxy and 4-methoxyphenyl groups, respectively, with a more polar moiety, including a carboxylic acid, alcohol, nitrile, carboxamide, sulfonamide, aldehyde or ketone function, or amino acid partial structures. Furthermore, it was investigated how the substitution of more than one of the aromatic 4-methoxy groups affects the potency and selectivity of the resulting compounds. Among the synthesized test substances (S)-1-{2-[(4-formylphenyl)bis(4-methoxyphenyl)-methoxy]ethyl}piperidine-3-carboxylic acid, that features a carbaldehyde function in place of one of the aromatic 4-methoxy moieties of (S)-SNAP-5114, was found to have a pIC50 value of 5.89±0.07, hence constituting a slightly more potent mGAT4 inhibitor than the parent substance while showing comparable subtype selectivity.  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