首页 | 官方网站   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   402370篇
  免费   5350篇
  国内免费   1348篇
工业技术   409068篇
  2021年   3863篇
  2020年   2938篇
  2019年   3797篇
  2018年   6478篇
  2017年   6474篇
  2016年   6917篇
  2015年   4318篇
  2014年   7134篇
  2013年   20030篇
  2012年   11405篇
  2011年   15264篇
  2010年   12139篇
  2009年   13712篇
  2008年   14048篇
  2007年   13816篇
  2006年   12415篇
  2005年   11115篇
  2004年   10506篇
  2003年   10423篇
  2002年   9831篇
  2001年   9736篇
  2000年   9138篇
  1999年   9528篇
  1998年   24345篇
  1997年   16725篇
  1996年   12810篇
  1995年   9527篇
  1994年   8368篇
  1993年   8383篇
  1992年   6057篇
  1991年   5695篇
  1990年   5679篇
  1989年   5318篇
  1988年   5044篇
  1987年   4420篇
  1986年   4300篇
  1985年   4817篇
  1984年   4425篇
  1983年   3999篇
  1982年   3654篇
  1981年   3731篇
  1980年   3428篇
  1979年   3329篇
  1978年   3338篇
  1977年   3723篇
  1976年   4828篇
  1975年   2836篇
  1974年   2639篇
  1973年   2705篇
  1972年   2267篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
55.
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   
56.
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   
57.
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   
58.
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   
59.
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   
60.
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   
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-23

京公网安备 11010802026262号