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   577023篇
  免费   6779篇
  国内免费   1190篇
电工技术   10644篇
综合类   546篇
化学工业   90339篇
金属工艺   23945篇
机械仪表   18631篇
建筑科学   12863篇
矿业工程   4352篇
能源动力   14506篇
轻工业   45803篇
水利工程   7000篇
石油天然气   15006篇
武器工业   40篇
无线电   60690篇
一般工业技术   116412篇
冶金工业   95714篇
原子能技术   14764篇
自动化技术   53737篇
  2021年   5484篇
  2019年   5282篇
  2018年   9213篇
  2017年   9412篇
  2016年   9840篇
  2015年   6033篇
  2014年   10467篇
  2013年   26339篇
  2012年   16510篇
  2011年   23938篇
  2010年   18053篇
  2009年   19766篇
  2008年   19691篇
  2007年   19322篇
  2006年   16717篇
  2005年   15312篇
  2004年   14617篇
  2003年   14344篇
  2002年   13572篇
  2001年   13167篇
  2000年   12559篇
  1999年   12080篇
  1998年   27755篇
  1997年   20100篇
  1996年   15663篇
  1995年   12075篇
  1994年   10908篇
  1993年   10621篇
  1992年   8340篇
  1991年   8108篇
  1990年   8004篇
  1989年   7793篇
  1988年   7489篇
  1987年   6754篇
  1986年   6544篇
  1985年   7397篇
  1984年   6725篇
  1983年   6451篇
  1982年   5781篇
  1981年   5902篇
  1980年   5630篇
  1979年   5735篇
  1978年   5664篇
  1977年   6178篇
  1976年   7687篇
  1975年   5108篇
  1974年   4905篇
  1973年   4980篇
  1972年   4279篇
  1971年   4038篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Koroteev  A. S. 《Atomic Energy》2021,130(4):202-208
Atomic Energy - The history and direction of further development of space nuclear energetics are examined. The functional diagram and principle of operation of a promising, powerful,...  相似文献   
2.
Journal of Computer and Systems Sciences International - It is shown that the Lyapunov theorem on the distribution properties of the sum of random variables with different distribution densities...  相似文献   
3.
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized...  相似文献   
4.
Theoretical Foundations of Chemical Engineering - On the basis of the classic concepts of the theory of solid-phase combustion, for the first time, a model with a detailed scheme of chemical...  相似文献   
5.
Multimedia Tools and Applications - The three-dimensional models of brain tumors serve as diagnostic assistance for physicians, surgeons, and radiologists. The proposed system establishes an...  相似文献   
6.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  相似文献   
7.
Glass and Ceramics - Ceramic bricks based on low-melting clay and ferro-dust from self-disintegrating, low-carbon, ferrochrome slags, graded from M100 to M175, respectively, were obtained in the...  相似文献   
8.
Automation and Remote Control - A linear-quadratic positional differential game of three persons is considered. Coefficient criteria are established under which there is no Nash equilibrium...  相似文献   
9.
Cell temperature and water content of the membrane have a significant effect on the performance of fuel cells. The current-power curve of the fuel cell has a maximum power point (MPP) that is needed to be tracked. This study presents a novel strategy based on a salp swarm algorithm (SSA) for extracting the maximum power of proton-exchange membrane fuel cell (PEMFC). At first, a new formula is derived to estimate the optimal voltage of PEMFC corresponding to MPP. Then the error between the estimated voltage at MPP and the actual terminal voltage of the fuel cell is fed to a proportional-integral-derivative controller (PID). The output of the PID controller tunes the duty cycle of a boost converter to maximize the harvested power from the PEMFC. SSA determines the optimal gains of PID. Sensitivity analysis is performed with the operating fuel cell at different cell temperature and water content of the membrane. The obtained results through the proposed strategy are compared with other programmed approaches of incremental resistance method, Fuzzy-Logic, grey antlion optimizer, wolf optimizer, and mine-blast algorithm. The obtained results demonstrated high reliability and efficiency of the proposed strategy in extracting the maximum power of the PEMFC.  相似文献   
10.
Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa.  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