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   584166篇
  免费   7141篇
  国内免费   1026篇
电工技术   10752篇
综合类   476篇
化学工业   93336篇
金属工艺   23634篇
机械仪表   18832篇
建筑科学   13591篇
矿业工程   4434篇
能源动力   14931篇
轻工业   47114篇
水利工程   7100篇
石油天然气   15121篇
武器工业   40篇
无线电   61382篇
一般工业技术   118776篇
冶金工业   99955篇
原子能技术   14850篇
自动化技术   48009篇
  2021年   5657篇
  2020年   4157篇
  2019年   5476篇
  2018年   9470篇
  2017年   9653篇
  2016年   10141篇
  2015年   6238篇
  2014年   10578篇
  2013年   27213篇
  2012年   16385篇
  2011年   21863篇
  2010年   17639篇
  2009年   19461篇
  2008年   19880篇
  2007年   19599篇
  2006年   16927篇
  2005年   15414篇
  2004年   14555篇
  2003年   14224篇
  2002年   13723篇
  2001年   13177篇
  2000年   12635篇
  1999年   12333篇
  1998年   28144篇
  1997年   20410篇
  1996年   15973篇
  1995年   12327篇
  1994年   11131篇
  1993年   10913篇
  1992年   8596篇
  1991年   8267篇
  1990年   8216篇
  1989年   8038篇
  1988年   7689篇
  1987年   6976篇
  1986年   6748篇
  1985年   7651篇
  1984年   6948篇
  1983年   6665篇
  1982年   6006篇
  1981年   6082篇
  1980年   5788篇
  1979年   5929篇
  1978年   5845篇
  1977年   6368篇
  1976年   7869篇
  1975年   5287篇
  1974年   5072篇
  1973年   5125篇
  1972年   4388篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Journal of Computer and Systems Sciences International - The problem of constructing a guaranteeing anticipating control for a shock isolator that protects an object on a movable base from impacts...  相似文献   
82.
Dreissenid mussel veligers compose a substantial component of pelagic biomass in the Great Lakes, yet their dynamics are poorly understood. To evaluate seasonal, spatial, and inter-annual variation in veliger density, we used a 64-μm mesh plankton net (2008, 2013–2016) and a 153-μm mesh plankton net (2007–2016) to collect dreissenid veligers at nearshore (15–25?m depth), transitional (45?m) and offshore (93–110?m) sites in southeast Lake Michigan during March–December. We also evaluated trends in density of recently settled mussels relative to veliger abundance and the density of the standing stock of adult mussels. Veliger density peaked during both summer and fall at all sites, but peak densities in summer were generally higher nearshore, whereas peak densities in the fall were generally higher offshore. The density of veligers in the 153-μm net was overall 28% of that in the 64-μm net, but there was high variability in this comparison among months. Smaller veligers were much more abundant in the 64-μm net, but there was little difference in the size distribution and abundance between nets for the 210–300?μm size classes. Thus, the 153-μm net could still be a useful tool for assessing density trends of larger veligers just prior to their settlement. Newly settled mussels (≤2?mm) were most abundant in summer or fall at the nearshore and offshore sites but were nearly absent at the transitional site despite the high density of veligers there. Factors other than veliger density must play an important role in mussel recruitment.  相似文献   
83.
Strength of Materials - The paper addresses the investigation of high-strain rate compressive behavior of Al foams subjected to impact at the intermediate striking velocity ranged from 40 to...  相似文献   
84.
Fedotov  A. A. 《Measurement Techniques》2019,61(12):1238-1243
Measurement Techniques - The article is devoted to the issues of conceptual development of a new generation of electrocardiogram imitators. A mathematical model is proposed for simulating ECG...  相似文献   
85.
86.
87.
Potentiometric sensors with plasticized poly(vinyl chloride) membranes based on β-lactam–tetraalkylammonium ion associates sensitive to penicillin antibiotics are proposed. The physicochemical characteristics (solubility product constants and dissociation constants) of active membrane components and the electrode, transport, and selective properties of the membranes of liquidand solid-contact sensors have been studied. The quantitative characteristics of membrane transport (penetrability, ion flux, and transport rate) have been evaluated. The main charge carriers in the membranes and at the membrane/solution interface have been determined from the membrane transport characteristics. The potentiometric sensors are shown to be applicable to the determination of penicillin antibiotics in biological fluids (blood serum and oral fluid) from patients with urinary tract infection.  相似文献   
88.
89.
The authors have developed a procedure and a test bench for studying evolution of various nature physical fields in modeling geomedium fracture by fluids. The test bench performs synchronous recording of macro- and micro-deformation, heat and acoustic emission induced in physical models of geomedium under loading to discontinuity. The experimental procedure has been trialed. The analysis of the synchronized test data allows a conclusion on the existence of time–space relationship between different nature physical fields induced during failure of solids.  相似文献   
90.
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