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   568288篇
  免费   7220篇
  国内免费   1025篇
电工技术   10548篇
综合类   478篇
化学工业   90560篇
金属工艺   23370篇
机械仪表   18546篇
建筑科学   12592篇
矿业工程   4315篇
能源动力   14550篇
轻工业   46019篇
水利工程   6954篇
石油天然气   15006篇
武器工业   40篇
无线电   60655篇
一般工业技术   116605篇
冶金工业   95782篇
原子能技术   14688篇
自动化技术   45825篇
  2021年   5526篇
  2019年   5315篇
  2018年   9257篇
  2017年   9531篇
  2016年   9882篇
  2015年   6079篇
  2014年   10338篇
  2013年   26281篇
  2012年   15888篇
  2011年   21260篇
  2010年   17104篇
  2009年   18946篇
  2008年   19180篇
  2007年   18848篇
  2006年   16371篇
  2005年   14857篇
  2004年   14113篇
  2003年   13763篇
  2002年   13308篇
  2001年   12904篇
  2000年   12379篇
  1999年   12056篇
  1998年   27719篇
  1997年   20079篇
  1996年   15666篇
  1995年   12034篇
  1994年   10894篇
  1993年   10655篇
  1992年   8367篇
  1991年   8120篇
  1990年   7998篇
  1989年   7789篇
  1988年   7494篇
  1987年   6761篇
  1986年   6546篇
  1985年   7402篇
  1984年   6710篇
  1983年   6446篇
  1982年   5780篇
  1981年   5905篇
  1980年   5640篇
  1979年   5740篇
  1978年   5669篇
  1977年   6186篇
  1976年   7692篇
  1975年   5114篇
  1974年   4908篇
  1973年   4983篇
  1972年   4281篇
  1971年   4042篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Water Resources Management - The water evaluation and planning (WEAP) approach and the invasive weed optimization algorithm (IWOA) are herein employed to determine the optimal operating policies in...  相似文献   
12.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  相似文献   
13.
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   
14.
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   
15.
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   
16.
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   
17.
This paper presents part of the work ComEd and Quanta Technology have performed to quantify the locational and temporal value of DER to avoid distribution grid upgrade investments. It focuses on the formulation of a robust and efficient algorithm for DER optimal dispatch on a distribution feeder to mitigate the violation of current and voltage limits using the allocated cost of capacity and locational marginal value of real and reactive DER injection/withdrawal.  相似文献   
18.
Theoretical Foundations of Chemical Engineering - Calcium formate is widely used in construction, tanning, and textile manufacture and as an E238 biological additive in cosmetology and the food...  相似文献   
19.
Russian Journal of Nondestructive Testing - The results of amplitude analysis of discrete acoustic emission signals from developing sources such as fatigue cracks are presented. The studies were...  相似文献   
20.
Russian Engineering Research - Digital tools for managing improvements in automobile production are developed. An operative tool provides warnings regarding the operational quality of the vehicles...  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