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   800533篇
  免费   11666篇
  国内免费   2424篇
电工技术   14667篇
综合类   745篇
化学工业   119995篇
金属工艺   30780篇
机械仪表   24293篇
建筑科学   18644篇
矿业工程   3932篇
能源动力   22247篇
轻工业   64787篇
水利工程   8165篇
石油天然气   14361篇
武器工业   48篇
无线电   93099篇
一般工业技术   157644篇
冶金工业   156331篇
原子能技术   16299篇
自动化技术   68586篇
  2022年   4815篇
  2021年   7350篇
  2020年   5513篇
  2019年   6976篇
  2018年   11894篇
  2017年   11719篇
  2016年   12413篇
  2015年   8366篇
  2014年   13806篇
  2013年   37976篇
  2012年   21833篇
  2011年   29977篇
  2010年   23754篇
  2009年   26807篇
  2008年   27285篇
  2007年   27028篇
  2006年   23806篇
  2005年   21600篇
  2004年   20643篇
  2003年   20487篇
  2002年   19318篇
  2001年   19280篇
  2000年   17985篇
  1999年   19046篇
  1998年   48977篇
  1997年   34309篇
  1996年   26331篇
  1995年   19695篇
  1994年   17140篇
  1993年   16960篇
  1992年   12225篇
  1991年   11399篇
  1990年   11319篇
  1989年   10877篇
  1988年   10063篇
  1987年   9032篇
  1986年   8828篇
  1985年   9828篇
  1984年   9086篇
  1983年   8134篇
  1982年   7571篇
  1981年   7689篇
  1980年   7230篇
  1979年   7073篇
  1978年   6878篇
  1977年   8154篇
  1976年   10691篇
  1975年   5935篇
  1974年   5553篇
  1973年   5718篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Measurement Techniques - A method is proposed for transferring the unit of mean power of laser radiation by means of measuring high-intensity power (kilowatts), with the possibility of constant...  相似文献   
112.
Wireless Personal Communications - In the fusion experiment, sensitive radio frequency signal diagnostic instruments need to be protected against high power stray radiation coming from the Electron...  相似文献   
113.
Sustainable and efficient food supply chain has become an essential component of one’s life. The model proposed in this paper is deeply linked to people's quality of life as a result of which there is a large incentive to fulfil customer demands through it. This proposed model can enhance food quality by making the best possible food quality accessible to customers, construct a sustainable logistics system considering its environmental impact and ensure the customer demand to be fulfilled as fast as possible. In this paper, an extended model is examined that builds a unified planning problem for efficient food logistics operations where four important objectives are viewed: minimising the total expense of the system, maximising the average food quality along with the minimisation of the amount of CO2 emissions in transportation along with production and total weighted delivery lead time minimisation. A four objective mixed integer linear programming model for intelligent food logistics system is developed in the paper. The optimisation of the formulated mathematical model is proposed using a modified multi-objective particle swarm optimisation algorithm with multiple social structures: MO-GLNPSO (Multi-Objective Global Local Near-Neighbour Particle Swarm Optimisation). Computational results of a case study on a given dataset as well as on multiple small, medium and large-scale datasets followed by sensitivity analysis show the potency and effectiveness of the introduced method. Lastly, there has been a scope for future study displayed which would lead to the further progress of these types of models.  相似文献   
114.
115.
Puzanov  A. S.  Obolenskiy  S. V.  Kozlov  V. A. 《Semiconductors》2020,54(8):946-950
Semiconductors - On the basis of the Monte Carlo algorithm, a method for calculating the energy spectrum of hot nonequilibrium electrons and holes in the track of a primary recoil atom after being...  相似文献   
116.
117.
118.
Programming and Computer Software - Image segmentation using a hierarchical sequence of piecewise constant approximations that minimally differ from the original image in terms of the total squared...  相似文献   
119.
120.

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   
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