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   552388篇
  免费   7370篇
  国内免费   1753篇
电工技术   10131篇
综合类   437篇
化学工业   81166篇
金属工艺   22056篇
机械仪表   17749篇
建筑科学   12235篇
矿业工程   3178篇
能源动力   15264篇
轻工业   41626篇
水利工程   5956篇
石油天然气   10683篇
武器工业   23篇
无线电   65845篇
一般工业技术   111608篇
冶金工业   105140篇
原子能技术   12471篇
自动化技术   45943篇
  2021年   5011篇
  2020年   3784篇
  2019年   4875篇
  2018年   8229篇
  2017年   8259篇
  2016年   8766篇
  2015年   5620篇
  2014年   9292篇
  2013年   26526篇
  2012年   14928篇
  2011年   20217篇
  2010年   16122篇
  2009年   18248篇
  2008年   18679篇
  2007年   18472篇
  2006年   16395篇
  2005年   14828篇
  2004年   14096篇
  2003年   14020篇
  2002年   13115篇
  2001年   13113篇
  2000年   12478篇
  1999年   13017篇
  1998年   33252篇
  1997年   23062篇
  1996年   17788篇
  1995年   13161篇
  1994年   11730篇
  1993年   11572篇
  1992年   8508篇
  1991年   8017篇
  1990年   7841篇
  1989年   7577篇
  1988年   7223篇
  1987年   6356篇
  1986年   6135篇
  1985年   6976篇
  1984年   6379篇
  1983年   5851篇
  1982年   5303篇
  1981年   5518篇
  1980年   5029篇
  1979年   5027篇
  1978年   5011篇
  1977年   5678篇
  1976年   7530篇
  1975年   4314篇
  1974年   4074篇
  1973年   4144篇
  1972年   3435篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Combined photochemical arylation, “nuisance effect” (SNAr) reaction sequences have been employed in the design of small arrays for immediate deployment in medium-throughput X-ray protein–ligand structure determination. Reactions were deliberately allowed to run “out of control” in terms of selectivity; for example the ortho-arylation of 2-phenylpyridine gave five products resulting from mono- and bisarylations combined with SNAr processes. As a result, a number of crystallographic hits against NUDT7, a key peroxisomal CoA ester hydrolase, have been identified.  相似文献   
102.
A tensile properties testing study was conducted to understand the influence of thickness, cross-head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t-tests show the significant difference among tested data. Using interaction plots, two-way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross-head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs.  相似文献   
103.
The machining of metal surfaces and the application of functional coatings by means of a flexible tool (a rotating wire brush) is considered. Frictional cladding may be applied on metal-cutting machines by means of simple attachments or manual angle grinders.  相似文献   
104.
105.
106.
Shevkunov  S. V. 《High Temperature》2015,53(2):259-271
High Temperature - The influence of heating from 260 to 400 K on the structure and mechanism of the formation of a molecular water film adsorbed on the walls of a plane fracture with the width of...  相似文献   
107.
108.
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   
109.
110.
Bochkareva  N. I.  Ivanov  A. M.  Klochkov  A. V.  Kogotkov  V. S.  Rebane  Yu. T.  Virko  M. V.  Shreter  Y. G. 《Semiconductors》2015,49(6):827-835
Semiconductors - It is shown that the emission efficiency and the 1/f noise level in light-emitting diodes with InGaN/GaN quantum wells correlate with how the differential resistance of a diode...  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