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   1486559篇
  免费   26943篇
  国内免费   7845篇
电工技术   35348篇
技术理论   5篇
综合类   7392篇
化学工业   271735篇
金属工艺   64520篇
机械仪表   42068篇
建筑科学   46353篇
矿业工程   11777篇
能源动力   50322篇
轻工业   112363篇
水利工程   14949篇
石油天然气   38328篇
武器工业   367篇
无线电   196722篇
一般工业技术   280018篇
冶金工业   146156篇
原子能技术   33926篇
自动化技术   168998篇
  2021年   16018篇
  2020年   12088篇
  2019年   14802篇
  2018年   15287篇
  2017年   14589篇
  2016年   21199篇
  2015年   17797篇
  2014年   29137篇
  2013年   88432篇
  2012年   35789篇
  2011年   47994篇
  2010年   42963篇
  2009年   51332篇
  2008年   44972篇
  2007年   42223篇
  2006年   45298篇
  2005年   39520篇
  2004年   41198篇
  2003年   41028篇
  2002年   40320篇
  2001年   36851篇
  2000年   35482篇
  1999年   34061篇
  1998年   39146篇
  1997年   35855篇
  1996年   33072篇
  1995年   29352篇
  1994年   27734篇
  1993年   27592篇
  1992年   25988篇
  1991年   22938篇
  1990年   23311篇
  1989年   22383篇
  1988年   20924篇
  1987年   19192篇
  1986年   18532篇
  1985年   21875篇
  1984年   22259篇
  1983年   20186篇
  1982年   19179篇
  1981年   19280篇
  1980年   17842篇
  1979年   18479篇
  1978年   17695篇
  1977年   17116篇
  1976年   17742篇
  1975年   15957篇
  1974年   15509篇
  1973年   15553篇
  1972年   13044篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
162.
Machine Learning - We propose a set of highly scalable algorithms for the combinatorial data analysis problem of seriating similarity matrices. Seriation consists of finding a permutation of data...  相似文献   
163.
The results of a system analysis of the efficiency of nitrous oxide(N_2O) as a propellant component for small space vehicles(SSV) were presented. A criterion for mass efficiency of the SSV propulsion system(PS) is determined. The current global state-of-the-art of SSV PSs is shown. The application field of nitrous oxide in SSV PSs is calculated and mass efficiency of N_2O application is quantitatively determined. An overview of physical and chemical as well as operational properties of nitrous oxide as a promising, non-toxic component of rocket propellant is provided. Main physical and chemical constants of gaseous and liquid nitrous oxide; chemical properties of N_2O, thermal stability of N_2O, catalytic decomposition of N_2O, a mechanism of decomposition of N_2O, catalysts for decomposition of N_2O, ballast additives to N_2O, application of nitrous oxide, nitrous oxide as a rocket propellant, production of nitrous oxide, toxicity of nitrous oxide, fire hazard of N_2O, requirements to equipment when handling N_2O; storage and transportation of N_2O are considered. It is demonstrated that nitrous oxide is a chemical compound meeting the requirements to rocket propellants, including those related to the environmental friendliness of propellants. With 75 references.  相似文献   
164.
The process of electrodeposition can be described in terms of a reaction-diffusion partial differential equation (PDE) system that models the dynamics of the morphology profile and the chemical composition. Here we fit such a model to the different patterns present in a range of electrodeposited and electrochemically modified alloys using PDE constrained optimization. Experiments with simulated data show how the parameter space of the model can be divided into zones corresponding to the different physical patterns by examining the structure of an appropriate cost function. We then use real data to demonstrate how numerical optimization of the cost function can allow the model to fit the rich variety of patterns arising in experiments. The computational technique developed provides a potential tool for tuning experimental parameters to produce desired patterns.  相似文献   
165.
Orduna-Malea  Enrique  Aytac  Selenay  Tran  Clara Y. 《Scientometrics》2019,121(1):433-450
Scientometrics - The purpose of this study is to ascertain the suitability of GS’s url-based method as a valid approximation of universities’ academic output measures, taking into...  相似文献   
166.
International Journal of Computer Vision - Anticipating future situations from streaming sensor data is a key perception challenge for mobile robotics and automated vehicles. We address the problem...  相似文献   
167.
Measurement Techniques - A comparative analysis of the results of estimation of measurement uncertainty is conducted. The results are obtained by a method described in the Handbook on the...  相似文献   
168.
Mobile Networks and Applications - Public cloud system offers Infrastructure-as-a-Service (IaaS) to deliver the computational resources on demand. Resource requirements of a cloud environment are...  相似文献   
169.
Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical...  相似文献   
170.
Strength of Materials - Creep constitutive equations have been derived for the materials that exhibit the properties of orthotropy (transversal isotropy) and transient creep under cyclic loading. A...  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