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   110757篇
  免费   11053篇
  国内免费   6779篇
电工技术   7996篇
技术理论   3篇
综合类   8294篇
化学工业   16549篇
金属工艺   6919篇
机械仪表   7566篇
建筑科学   8470篇
矿业工程   3285篇
能源动力   3463篇
轻工业   8194篇
水利工程   2610篇
石油天然气   4760篇
武器工业   1284篇
无线电   13645篇
一般工业技术   12538篇
冶金工业   5277篇
原子能技术   1660篇
自动化技术   16076篇
  2024年   447篇
  2023年   1393篇
  2022年   2838篇
  2021年   4150篇
  2020年   3087篇
  2019年   2657篇
  2018年   2886篇
  2017年   3406篇
  2016年   3267篇
  2015年   4569篇
  2014年   5893篇
  2013年   7006篇
  2012年   8089篇
  2011年   9026篇
  2010年   8293篇
  2009年   7938篇
  2008年   8017篇
  2007年   7638篇
  2006年   7083篇
  2005年   5686篇
  2004年   4282篇
  2003年   3521篇
  2002年   3400篇
  2001年   2879篇
  2000年   2281篇
  1999年   1708篇
  1998年   1358篇
  1997年   1089篇
  1996年   827篇
  1995年   668篇
  1994年   555篇
  1993年   468篇
  1992年   316篇
  1991年   255篇
  1990年   209篇
  1989年   202篇
  1988年   126篇
  1987年   108篇
  1986年   108篇
  1985年   95篇
  1984年   88篇
  1983年   70篇
  1982年   60篇
  1981年   61篇
  1980年   55篇
  1979年   46篇
  1978年   35篇
  1977年   59篇
  1976年   81篇
  1975年   41篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
43.
44.
45.
The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions.  相似文献   
46.
International Journal of Mechanics and Materials in Design - A simple iterative method is presented for cutting pattern optimization of frame-supported and pneumatic membrane structures for...  相似文献   
47.
48.
Wan  Huan  Wang  Hui  Scotney  Bryan  Liu  Jun  Ng  Wing W. Y. 《Multimedia Tools and Applications》2020,79(39-40):29327-29352
Multimedia Tools and Applications - In many real-world classification problems there exist multiple subclasses (or clusters) within a class; in other words, the underlying data distribution is...  相似文献   
49.
Here, we report a facile approach to electrostatically couple the surface charges of graphite nanoplate (GNP) fillers and poly(methyl methacrylate) (PMMA) polymer particles using ethylene maleic anhydride (EMA) copolymer as an electrostatic coupling agent. Our strategy involved switching the intrinsic repulsive electrostatic interactions between the directly exfoliated GNPs fillers and the PMMA particles to attractive electrostatic surface interactions for preparing core(PMMA)-shell (GNP) precursor in order to optimizing 3-dimensionally dispersed polymer nanocomposite. As a result, the electrical conductivity of the composites dramatically increased by a factor of 16.7 in the EMA-coupled GNP/PMMA composites compared with that of the EMA-free GNP/PMMA composites. In addition, the percolation threshold was also notably reduced from 0.32 to 0.159 vol% after electrostatic coupling of the GNPs fillers and PMMA particles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48390.  相似文献   
50.
In the past two decades, brain science and robotics have made gigantic advances in their own fields, and their interactions have generated several interdisciplinary research fields. First, in the ‘understanding the brain by creating the brain’ approach, computational neuroscience models have been applied to many robotics problems. Second, such brain-motivated fields as cognitive robotics and developmental robotics have emerged as interdisciplinary areas among robotics, neuroscience and cognitive science with special emphasis on humanoid robots. Third, in brain–machine interface research, a brain and a robot are mutually connected within a closed loop. In this paper, we review the theoretical backgrounds of these three interdisciplinary fields and their recent progress. Then, we introduce recent efforts to reintegrate these research fields into a coherent perspective and propose a new direction that integrates brain science and robotics where the decoding of information from the brain, robot control based on the decoded information and multimodal feedback to the brain from the robot are carried out in real time and in a closed loop.  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