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   411091篇
  免费   14427篇
  国内免费   6584篇
电工技术   13050篇
技术理论   9篇
综合类   8882篇
化学工业   62466篇
金属工艺   24430篇
机械仪表   20032篇
建筑科学   14570篇
矿业工程   6341篇
能源动力   8696篇
轻工业   22845篇
水利工程   6634篇
石油天然气   16556篇
武器工业   1067篇
无线电   42770篇
一般工业技术   82655篇
冶金工业   47365篇
原子能技术   10794篇
自动化技术   42940篇
  2023年   2556篇
  2022年   5037篇
  2021年   7813篇
  2020年   5919篇
  2019年   5642篇
  2018年   14717篇
  2017年   15523篇
  2016年   12345篇
  2015年   7923篇
  2014年   10610篇
  2013年   16964篇
  2012年   16686篇
  2011年   23341篇
  2010年   20372篇
  2009年   19699篇
  2008年   19796篇
  2007年   20774篇
  2006年   12533篇
  2005年   13712篇
  2004年   10684篇
  2003年   10345篇
  2002年   9389篇
  2001年   8545篇
  2000年   7719篇
  1999年   7293篇
  1998年   12551篇
  1997年   9163篇
  1996年   7274篇
  1995年   5701篇
  1994年   4918篇
  1993年   4914篇
  1992年   3983篇
  1991年   3857篇
  1990年   3719篇
  1989年   3582篇
  1988年   3468篇
  1987年   3048篇
  1986年   3039篇
  1985年   3291篇
  1984年   3138篇
  1983年   2965篇
  1982年   2729篇
  1981年   2691篇
  1980年   2744篇
  1979年   2834篇
  1978年   2864篇
  1977年   2957篇
  1976年   3374篇
  1975年   2652篇
  1973年   2634篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
81.
Theoretical Foundations of Chemical Engineering - The development of a thermostable hydrophobic platinum catalyst is an important scientific and practical problem. The purpose of this work is to...  相似文献   
82.
The basic stages in the life cycle of a batch of complex engineering products are considered: design, production, operation, and disposal. A priori cost assessment for each stage is discussed. The cost aggregation in the consideration of multiple stages is analyzed. Requirements on the assessment are formulated. Methodological and implementation aspects of the assessment tools are outlined. The conclusion is that it is expedient to predict the costs on the basis of mathematical models of the product batch in an operational environment. The integration of multiple cost estimates is addressed.  相似文献   
83.
Fang  Zhiwei  Xing  Qiyu  Fernandez  Desiree  Zhang  Xiao  Yu  Guihua 《Nano Research》2020,13(5):1179-1190

Two-dimensional (2D) nanomaterials have attracted a great deal of attention since the discovery of graphene in 2004, due to their intriguing physicochemical properties and wide-ranging applications in catalysis, energy-related devices, electronics and optoelectronics. To maximize the potential of 2D nanomaterials for their technological applications, controlled assembly of 2D nanobulding blocks into integrated systems is critically needed. This mini review summarizes the reported strategies of 2D materials-based assembly into integrated functional nanostructures, from in-situ assembly method to post-synthesis assembly. The applications of 2D assembled integrated structures are also covered, especially in the areas of energy, electronics and sensing, and we conclude with discussion on the remaining challenges and potential directions in this emerging field.

  相似文献   
84.
ABSTRACT

In the lower chamber of pressurized water reactor (PWR), the flow distribution device is the core module to distribute coolant into the core. It has complex structure and numerous design parameters. Therefore, it has important theoretical and practical significance to optimize the device. The mesh independence verification, turbulence model selection, and data processing all can influence the numerical simulation results of the lower chamber, in order to research the influence, a numerical simulation method based on the original model of CNP1000 reactor lower chamber is proposed in this paper. In the method, an optimization design method of flow distribution device is established based on surrogate model. The main design variables and optimization objectives are determined based on the device’s structure and function characteristics. And then it respectively adopts Kriging algorithm and multi-objective genetic algorithm to establish a surrogate model of flow distribution device and optimize it globally. Finally, the optimal design variables are obtained. Compared with the device’s performance before optimization, the after optimization has smaller total pressure loss and more uniform flow. The effectiveness and practicability of proposed optimization design method can be verified.  相似文献   
85.
Russian Journal of Non-Ferrous Metals - Rolling bearing rings comprise a large reserve for expanding powder metallurgy production. This reserve is being incompletely implemented. The hot forging of...  相似文献   
86.
Chen  Meng  Yu  Xiaohui  Liu  Yang 《World Wide Web》2019,22(6):2901-2920
World Wide Web - The wide spread use of positioning and photographing devices gives rise to a deluge of traffic trajectory data (e.g., vehicle passage records and taxi trajectory data), with each...  相似文献   
87.
88.
89.
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