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   199911篇
  免费   2659篇
  国内免费   612篇
电工技术   3473篇
综合类   149篇
化学工业   29117篇
金属工艺   8061篇
机械仪表   6079篇
建筑科学   4819篇
矿业工程   1303篇
能源动力   5155篇
轻工业   17186篇
水利工程   2300篇
石油天然气   4040篇
武器工业   8篇
无线电   23144篇
一般工业技术   40108篇
冶金工业   37298篇
原子能技术   5093篇
自动化技术   15849篇
  2021年   1632篇
  2019年   1588篇
  2018年   2616篇
  2017年   2673篇
  2016年   2794篇
  2015年   1805篇
  2014年   3098篇
  2013年   8996篇
  2012年   5070篇
  2011年   7050篇
  2010年   5616篇
  2009年   6375篇
  2008年   6473篇
  2007年   6526篇
  2006年   5597篇
  2005年   5236篇
  2004年   5016篇
  2003年   4892篇
  2002年   4535篇
  2001年   4661篇
  2000年   4580篇
  1999年   4730篇
  1998年   11396篇
  1997年   8144篇
  1996年   6416篇
  1995年   4681篇
  1994年   4273篇
  1993年   4077篇
  1992年   3225篇
  1991年   3080篇
  1990年   2873篇
  1989年   2955篇
  1988年   2828篇
  1987年   2400篇
  1986年   2310篇
  1985年   2718篇
  1984年   2507篇
  1983年   2347篇
  1982年   2090篇
  1981年   2205篇
  1980年   2030篇
  1979年   2124篇
  1978年   2120篇
  1977年   2367篇
  1976年   3190篇
  1975年   1834篇
  1974年   1761篇
  1973年   1772篇
  1972年   1443篇
  1971年   1339篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Fefelov  S. A.  Kazakova  L. P.  Bogoslovskiy  N. A.  Bylev  A. B.  Yakubov  A. O. 《Semiconductors》2020,54(4):450-453
Semiconductors - The current–voltage characteristics measured on Ge2Sb2Te5 thin films in the current mode are studied. The effect of multilevel recording is established when applying...  相似文献   
22.
23.

To increase the efficiency of designing systems intended for monitoring surface cracks in aluminum structures during their working life, we have analyzed a two-dimensional symmetric problem on uniaxial extension of an Al-polyimide-Cu layered structure with ideal adhesion between layers and a model crack in the aluminum base. The problem has been first solved for a sample with the crack modeled by a zero-thickness notch using the ANSYS engineering simulation program package. It is shown that this setting of the problem can lead to inadequate results as manifested, in particular, by significantly overstated mechanical stresses in aluminum in the region of crack emergence on the surface. In order to eliminate this difficulty, we propose to use the structure with a model defect in the form of a notch of nonzero thickness in the initial unstressed state of the structure. Recommendations for selecting the thickness of a notch used in the model structure are given.

  相似文献   
24.
25.
26.
27.
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   
28.
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   
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