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   582483篇
  免费   7763篇
  国内免费   1024篇
电工技术   10636篇
综合类   477篇
化学工业   93653篇
金属工艺   23582篇
机械仪表   18809篇
建筑科学   13017篇
矿业工程   4347篇
能源动力   14802篇
轻工业   48763篇
水利工程   7106篇
石油天然气   15037篇
武器工业   39篇
无线电   61121篇
一般工业技术   118689篇
冶金工业   98490篇
原子能技术   14747篇
自动化技术   47955篇
  2021年   5953篇
  2020年   4419篇
  2019年   5738篇
  2018年   9908篇
  2017年   10043篇
  2016年   10541篇
  2015年   6582篇
  2014年   10969篇
  2013年   27448篇
  2012年   16826篇
  2011年   22043篇
  2010年   17731篇
  2009年   19563篇
  2008年   19755篇
  2007年   19383篇
  2006年   16753篇
  2005年   15105篇
  2004年   14369篇
  2003年   14022篇
  2002年   13540篇
  2001年   13032篇
  2000年   12495篇
  1999年   12219篇
  1998年   28580篇
  1997年   20641篇
  1996年   16015篇
  1995年   12225篇
  1994年   11031篇
  1993年   10811篇
  1992年   8401篇
  1991年   8168篇
  1990年   8049篇
  1989年   7844篇
  1988年   7553篇
  1987年   6798篇
  1986年   6599篇
  1985年   7458篇
  1984年   6746篇
  1983年   6471篇
  1982年   5821篇
  1981年   5950篇
  1980年   5669篇
  1979年   5747篇
  1978年   5685篇
  1977年   6244篇
  1976年   7818篇
  1975年   5124篇
  1974年   4920篇
  1973年   4993篇
  1972年   4285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.
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   
3.
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   
4.
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   
5.
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   
6.
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   
7.
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   
8.
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   
9.
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   
10.
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   
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