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   640393篇
  免费   8666篇
  国内免费   1862篇
工业技术   650921篇
  2021年   5480篇
  2020年   4184篇
  2019年   5314篇
  2018年   9023篇
  2017年   8847篇
  2016年   9493篇
  2015年   6179篇
  2014年   10305篇
  2013年   31019篇
  2012年   16707篇
  2011年   22607篇
  2010年   18001篇
  2009年   20494篇
  2008年   21155篇
  2007年   20943篇
  2006年   18702篇
  2005年   16997篇
  2004年   16341篇
  2003年   16130篇
  2002年   15350篇
  2001年   15395篇
  2000年   14606篇
  1999年   15301篇
  1998年   38239篇
  1997年   26839篇
  1996年   20055篇
  1995年   15647篇
  1994年   13985篇
  1993年   13772篇
  1992年   10091篇
  1991年   9544篇
  1990年   9481篇
  1989年   9085篇
  1988年   8683篇
  1987年   7546篇
  1986年   7503篇
  1985年   8665篇
  1984年   7874篇
  1983年   7227篇
  1982年   6588篇
  1981年   6790篇
  1980年   6279篇
  1979年   6132篇
  1978年   5948篇
  1977年   7010篇
  1976年   9088篇
  1975年   5201篇
  1974年   4933篇
  1973年   4985篇
  1972年   4179篇
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
81.
Metallurgical and Materials Transactions A - The influence of the chemical composition on the crystallization process, amorphous phase formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y...  相似文献   
82.
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   
83.
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   
84.
ABSTRACT

This paper deals with asymptotic stabilisation of a class of nonlinear input-delayed systems via dynamic output feedback in the presence of disturbances. The proposed strategy has the structure of an observer-based control law, in which the observer estimates and predicts both the plant state and the external disturbance. A nominal delay value is assumed to be known and stability conditions in terms of linear matrix inequalities are derived for fast-varying delay uncertainties. Asymptotic stability is achieved if the disturbance or the time delay is constant. The controller design problem is also addressed and a numerical example with an unstable system is provided to illustrate the usefulness of the proposed strategy.  相似文献   
85.
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   
86.
87.
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   
88.
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   
89.
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   
90.
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