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   418892篇
  免费   6072篇
  国内免费   1369篇
电工技术   7745篇
综合类   332篇
化学工业   62868篇
金属工艺   16711篇
机械仪表   13854篇
建筑科学   9299篇
矿业工程   2203篇
能源动力   11992篇
轻工业   29942篇
水利工程   4366篇
石油天然气   7967篇
武器工业   18篇
无线电   50604篇
一般工业技术   85720篇
冶金工业   77578篇
原子能技术   9347篇
自动化技术   35787篇
  2022年   2499篇
  2021年   4286篇
  2020年   3260篇
  2019年   4139篇
  2018年   6868篇
  2017年   6835篇
  2016年   7372篇
  2015年   4705篇
  2014年   7618篇
  2013年   21017篇
  2012年   12178篇
  2011年   16289篇
  2010年   12845篇
  2009年   14458篇
  2008年   14844篇
  2007年   14513篇
  2006年   13040篇
  2005年   11650篇
  2004年   10939篇
  2003年   10793篇
  2002年   10200篇
  2001年   9984篇
  2000年   9409篇
  1999年   9815篇
  1998年   24946篇
  1997年   17128篇
  1996年   13140篇
  1995年   9763篇
  1994年   8596篇
  1993年   8624篇
  1992年   6223篇
  1991年   5836篇
  1990年   5792篇
  1989年   5445篇
  1988年   5153篇
  1987年   4518篇
  1986年   4400篇
  1985年   4924篇
  1984年   4540篇
  1983年   4099篇
  1982年   3732篇
  1981年   3826篇
  1980年   3501篇
  1979年   3414篇
  1978年   3414篇
  1977年   3855篇
  1976年   4974篇
  1975年   2927篇
  1974年   2728篇
  1973年   2791篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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   
62.
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   
63.
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   
64.
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   
65.
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   
66.
67.
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   
68.
69.
70.

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