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   132846篇
  免费   12954篇
  国内免费   8049篇
电工技术   9546篇
技术理论   5篇
综合类   10434篇
化学工业   19944篇
金属工艺   8447篇
机械仪表   8921篇
建筑科学   10700篇
矿业工程   4285篇
能源动力   3941篇
轻工业   8946篇
水利工程   3087篇
石油天然气   7224篇
武器工业   1506篇
无线电   16010篇
一般工业技术   14309篇
冶金工业   5383篇
原子能技术   1954篇
自动化技术   19207篇
  2024年   588篇
  2023年   1862篇
  2022年   3613篇
  2021年   5218篇
  2020年   3884篇
  2019年   3261篇
  2018年   3601篇
  2017年   4192篇
  2016年   3808篇
  2015年   5450篇
  2014年   6972篇
  2013年   8222篇
  2012年   9513篇
  2011年   10490篇
  2010年   9651篇
  2009年   9176篇
  2008年   9159篇
  2007年   8810篇
  2006年   8483篇
  2005年   6939篇
  2004年   5038篇
  2003年   4141篇
  2002年   3995篇
  2001年   3402篇
  2000年   2946篇
  1999年   2498篇
  1998年   1657篇
  1997年   1447篇
  1996年   1289篇
  1995年   1057篇
  1994年   835篇
  1993年   638篇
  1992年   462篇
  1991年   351篇
  1990年   265篇
  1989年   239篇
  1988年   175篇
  1987年   124篇
  1986年   104篇
  1985年   44篇
  1984年   38篇
  1983年   43篇
  1982年   46篇
  1981年   33篇
  1980年   25篇
  1979年   10篇
  1977年   14篇
  1976年   5篇
  1959年   17篇
  1951年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
Machine Intelligence Research - This paper proposes an image encryption algorithm LQBPNN (logistic quantum and back propagation neural network) based on chaotic sequences incorporating quantum...  相似文献   
74.
Low-loss (Zn1-xNix)ZrNbTaO8 (0.02?≤?x?≤?0.10) ceramics possessing single wolframite structure are initiatively synthesized by solid-state route. Based on the results of Rietveld refinement, complex chemical bond theory is used to establish the correlation between structural characteristics and microwave performance in this ceramic system. A small amount of Ni2+ (x?=?0.06) in A-site with the fixed substitution of Ta5+ in B-site can effectually raise the Q?×?f value of ZnZrNb2O8 ceramic, embodying a dense microstructure and high lattice energy. The dielectric constant and τf are mainly affected by bond ionicity and the average octahedral distortion. The (Zn0.94Ni0.06)ZrNbTaO8 ceramic sample sintered at 1150?°C for 3?h exhibits an outstanding combination of microwave dielectric properties: εr =?27.88, Q?×?f?=?128,951?GHz, τf =?–39.9?ppm/°C. Thus, it is considered to be a candidate material for the communication device applications at high frequency.  相似文献   
75.
76.
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   
77.
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   
78.
79.
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   
80.
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