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   719036篇
  免费   11294篇
  国内免费   2209篇
电工技术   13288篇
综合类   875篇
化学工业   108311篇
金属工艺   27173篇
机械仪表   20830篇
建筑科学   17905篇
矿业工程   3059篇
能源动力   20099篇
轻工业   63418篇
水利工程   6940篇
石油天然气   11529篇
武器工业   55篇
无线电   84337篇
一般工业技术   140064篇
冶金工业   139532篇
原子能技术   13961篇
自动化技术   61163篇
  2022年   4360篇
  2021年   6823篇
  2020年   5031篇
  2019年   6197篇
  2018年   10631篇
  2017年   10359篇
  2016年   10957篇
  2015年   7644篇
  2014年   12533篇
  2013年   33714篇
  2012年   19678篇
  2011年   26866篇
  2010年   21351篇
  2009年   23980篇
  2008年   24690篇
  2007年   24230篇
  2006年   21190篇
  2005年   18996篇
  2004年   18269篇
  2003年   18097篇
  2002年   17150篇
  2001年   17433篇
  2000年   16183篇
  1999年   17175篇
  1998年   44241篇
  1997年   30944篇
  1996年   23718篇
  1995年   17820篇
  1994年   15556篇
  1993年   15342篇
  1992年   10990篇
  1991年   10428篇
  1990年   10171篇
  1989年   9747篇
  1988年   9178篇
  1987年   8093篇
  1986年   7938篇
  1985年   8827篇
  1984年   8249篇
  1983年   7480篇
  1982年   6982篇
  1981年   6979篇
  1980年   6716篇
  1979年   6438篇
  1978年   6094篇
  1977年   7449篇
  1976年   9999篇
  1975年   5192篇
  1974年   4945篇
  1973年   5007篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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   
102.
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   
103.
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   
104.
105.
106.
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   
107.
108.
109.
110.
Diffusional limitations (the gel, glass, and cage effects) are manifested in several bulk free radical homopolymerizations as well as in random copolymerizations. These are associated with decreases of several orders of magnitude of the rate constants of termination, propagation, and initiation (the initiator efficiency), respectively. These phenomena have been modeled earlier using the free volume theory for the diffusivities of primary radicals, macro‐radicals, and monomer molecules, and have been applied to homopolymerizations. In this study, a similar model is developed for random bulk copolymerizations. The parameters of the model are fitted using isothermal data on styrene acrylonitrile random copolymerization carried out in small ampoules. Thereafter, best‐fit global correlations have been developed for this system. This enables the model to be used for studying non‐isothermal copolymerizations, as well as for carrying out optimization of industrial reactors, where non‐isothermal conditions are a norm. POLYM. ENG. SCI., 55:2098–2110, 2015. © 2014 Society of Plastics Engineers  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