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   513676篇
  免费   5119篇
  国内免费   1090篇
电工技术   9171篇
综合类   497篇
化学工业   76794篇
金属工艺   27577篇
机械仪表   19016篇
建筑科学   10683篇
矿业工程   4809篇
能源动力   10217篇
轻工业   31905篇
水利工程   6821篇
石油天然气   15398篇
武器工业   91篇
无线电   54531篇
一般工业技术   115025篇
冶金工业   76437篇
原子能技术   15106篇
自动化技术   45807篇
  2021年   4198篇
  2019年   4171篇
  2018年   12720篇
  2017年   13174篇
  2016年   11661篇
  2015年   5113篇
  2014年   8407篇
  2013年   19679篇
  2012年   14066篇
  2011年   21193篇
  2010年   17862篇
  2009年   18352篇
  2008年   19442篇
  2007年   20372篇
  2006年   13084篇
  2005年   13615篇
  2004年   12627篇
  2003年   12360篇
  2002年   11217篇
  2001年   10673篇
  2000年   10458篇
  1999年   9870篇
  1998年   20253篇
  1997年   15235篇
  1996年   11938篇
  1995年   9551篇
  1994年   8685篇
  1993年   8738篇
  1992年   7286篇
  1991年   7095篇
  1990年   7036篇
  1989年   6714篇
  1988年   6449篇
  1987年   6027篇
  1986年   5878篇
  1985年   6485篇
  1984年   6218篇
  1983年   5753篇
  1982年   5453篇
  1981年   5566篇
  1980年   5403篇
  1979年   5485篇
  1978年   5542篇
  1977年   5910篇
  1976年   6958篇
  1975年   5105篇
  1974年   5146篇
  1973年   5228篇
  1972年   4467篇
  1971年   4108篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
Physicotechnical properties are provided for concretes based on mechanically-activated phosphate suspensions previously modified with magnesium and aluminum hydroxides and silicic acid. The results obtained demonstrate the efficiency of using modifying additions in order to increase the strength and heat resistance of corundum concretes. Translated from Novye Ogneupory, No. 5, pp. 32–35, May 2008.  相似文献   
892.
Symmetric interference in two-dimensional multimode silicon waveguides is experimentally investigated. For a 100/spl times/100 /spl mu/m/sup 2/ cross section, 2700-/spl mu/m-long waveguide fabricated on silicon-on-insulator substrate, an 8/spl times/8 matrix of replicated images with high contrast ratio is demonstrated for 1530-1570 nm wavelength range. Symmetric interference results in reduced device length, and the actual device length is consistent with the theoretical expectation. The device also exhibits stable imaging in terms of good loss uniformity, and low wavelength and polarization dependencies among the replicated images.  相似文献   
893.
The recent researches and technological developments of middle and long wavelength infrared HgCdTe photovoltaic detectors are presented. Structure, topology, design and performance of HgCdTe photodiodes, silicon readout electronics, Focal Plane Arrays both staring and time delay and integration types, thermal imagers are discussed. Negative differential conductance, bistability and high frequency oscillations under background infrared radiation in HgCdTe photodiodes are reported.  相似文献   
894.
A method is considered to solve a conditional optimization problem with a linear-fractional objective function over permutations. The performance of sub algorithms to solve this problem is evaluated. The practical efficiency of the algorithm is analyzed by conducting numerical experiments. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 133–146, July–August 2007.  相似文献   
895.
Cloning of observables, unlike standard cloning of states, aims at copying the information encoded in the statistics of a class of observables rather then on quantum states themselves. In such a process the emphasis is on the quantum operation (evolution plus measurement) necessary to retrieve the original information. We analyze, for qubit systems, the cloning of a class generated by two noncommuting observables, elucidating the relationship between such a process and joint measurements. This helps in establishing an optimality criterion for cloning of observables. We see that, even if the cloning machine is designed to act on the whole class generated by two noncommuting observables, the same optimal performances of a joint measurement can be attained. Finally, the connection with state dependent cloning is enlightened.  相似文献   
896.
The problem of synthesizing trajectories, planning and implementing the motion of a mobile robot is investigated. The statement of the problem is motivated by the need for designing an optimal control of robots with two wheels controlled independently. Mobile robots with this kinematic scheme are called robots with “differential drive.”  相似文献   
897.
898.
The task of ascertaining minimal semantic-syntactic text units within the framework of the task of the semantic analysis of texts in the Russian language is considered. The use of the DSM-method for producing rules for ascertaining the meanings of syntaxemes is described, the setting of the goal of producing rules in DSM-method terminology is presented. The analysis of the results of computer experiments and the causes of the presence of contradictory rules are given.  相似文献   
899.
This article is devoted to work done in 2002–2006 as part of the unified project Reabilitatsiya to rehabilitate radiation hazardous objects and sections of the radioactively contaminated territory of the Russian Science Center Kurchatov Institute. The main objects of the rehabilitation work were old storage sites built for radioactive wastes on the territory of the Institute when military and civilian nuclear technologies were under development. The structural features of the storage sites, including the volumes and characteristics of the wastes stored, are presented. The salient aspects of the disposal sites, taken into account during the rehabilitation work, are discussed. The organization of the rehabilitation operations and the sequence in which they are performed, the special features of the technical design solutions used, the technological methods, and ways for conducting the work are described. __________ Translated from Atomnaya énergiya, Vol. 102, No. 5, pp. 300–306, May, 2007.  相似文献   
900.
The effect of tempering temperature on the structure, wear resistance, and corrosive properties of steel 08Kh14AN4MDB is studied. The results of mechanical and corrosion tests are used for constructing an optimization matrix for determining the optimum tempering temperature. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 29–32, February, 2007.  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