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   407593篇
  免费   5738篇
  国内免费   1358篇
电工技术   7659篇
综合类   317篇
化学工业   60722篇
金属工艺   16544篇
机械仪表   13666篇
建筑科学   8489篇
矿业工程   2165篇
能源动力   11750篇
轻工业   29424篇
水利工程   4308篇
石油天然气   7946篇
武器工业   17篇
无线电   49499篇
一般工业技术   83734篇
冶金工业   75507篇
原子能技术   9221篇
自动化技术   33721篇
  2022年   2438篇
  2021年   4137篇
  2020年   3116篇
  2019年   4020篇
  2018年   6705篇
  2017年   6727篇
  2016年   7128篇
  2015年   4466篇
  2014年   7361篇
  2013年   20427篇
  2012年   11687篇
  2011年   15587篇
  2010年   12373篇
  2009年   13972篇
  2008年   14264篇
  2007年   13989篇
  2006年   12563篇
  2005年   11214篇
  2004年   10604篇
  2003年   10517篇
  2002年   9908篇
  2001年   9795篇
  2000年   9192篇
  1999年   9584篇
  1998年   24489篇
  1997年   16827篇
  1996年   12905篇
  1995年   9571篇
  1994年   8403篇
  1993年   8419篇
  1992年   6073篇
  1991年   5707篇
  1990年   5704篇
  1989年   5334篇
  1988年   5068篇
  1987年   4429篇
  1986年   4310篇
  1985年   4824篇
  1984年   4428篇
  1983年   3998篇
  1982年   3660篇
  1981年   3737篇
  1980年   3434篇
  1979年   3329篇
  1978年   3339篇
  1977年   3756篇
  1976年   4864篇
  1975年   2857篇
  1974年   2669篇
  1973年   2736篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
Fefelov  S. A.  Kazakova  L. P.  Bogoslovskiy  N. A.  Bylev  A. B.  Yakubov  A. O. 《Semiconductors》2020,54(4):450-453
Semiconductors - The current–voltage characteristics measured on Ge2Sb2Te5 thin films in the current mode are studied. The effect of multilevel recording is established when applying...  相似文献   
65.
Hussien  O. S.  Elamy  M. I. 《Strength of Materials》2020,52(3):470-479
Strength of Materials - The use of a damping system is one of the seismic protection systems that improve the seismic response of structures. The proposed methodology estimates the location (which...  相似文献   
66.
Powder Metallurgy and Metal Ceramics - The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was...  相似文献   
67.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided.  相似文献   
68.
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   
69.
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   
70.
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