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   1615951篇
  免费   28434篇
  国内免费   7061篇
电工技术   34987篇
综合类   6520篇
化学工业   276143篇
金属工艺   66073篇
机械仪表   46227篇
建筑科学   48625篇
矿业工程   11737篇
能源动力   50616篇
轻工业   126577篇
水利工程   16339篇
石油天然气   38121篇
武器工业   153篇
无线电   200073篇
一般工业技术   301619篇
冶金工业   218513篇
原子能技术   34471篇
自动化技术   174652篇
  2021年   15720篇
  2020年   12122篇
  2019年   14860篇
  2018年   18452篇
  2017年   17857篇
  2016年   22918篇
  2015年   17857篇
  2014年   29058篇
  2013年   88753篇
  2012年   38539篇
  2011年   53229篇
  2010年   45497篇
  2009年   53110篇
  2008年   49009篇
  2007年   46713篇
  2006年   47081篇
  2005年   42557篇
  2004年   43961篇
  2003年   43609篇
  2002年   42342篇
  2001年   39561篇
  2000年   37559篇
  1999年   37575篇
  1998年   61898篇
  1997年   49737篇
  1996年   42142篇
  1995年   34739篇
  1994年   31920篇
  1993年   31926篇
  1992年   27201篇
  1991年   24454篇
  1990年   24653篇
  1989年   23797篇
  1988年   22338篇
  1987年   20460篇
  1986年   19834篇
  1985年   23155篇
  1984年   22857篇
  1983年   20814篇
  1982年   19696篇
  1981年   19896篇
  1980年   18526篇
  1979年   18848篇
  1978年   18155篇
  1977年   18847篇
  1976年   21356篇
  1975年   16304篇
  1974年   15688篇
  1973年   15833篇
  1972年   13303篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
221.
Hassan  Lovelu  Khan  K. A. 《Microsystem Technologies》2020,26(3):1031-1041

The efficiency of any electric cell or battery is very important. To keep it in mind it has been studied the columbic efficiency, voltaic efficiency and energy efficiency of a PKL (Pathor Kuchi Leaf) Quasi Voltaic Cell or Modified Voltaic Cell. It was found that the columbic efficiency data illustrated that this efficiency was lower comparing to other efficiencies may be the absence of salt bridge or separator between the electrodes. Because, our designed and fabricated PKL cell does not have any salt bridge. So that the internal resistance is lower than the traditional voltaic cell and as a result more current was found. The voltage and current changes with time and I–V characteristics for PKL unit cell, module, panel and array have also been studied. It is shown that the voltaic and energy efficiency have been studied. However, the highest efficiency was obtained for 40% PKL sap with 5% secondary salt in 55% aqueous solution, which implies that the concentration of PKL juice can play an important role regarding efficiency. It was also found that the average energy efficiency was 97.43% and it was also found that the average voltaic efficiency was 57.29%. Finally, morphological study FESEM (Field Emission Scanning Electron Microscopy) has also been performed. It is seen that the results confirmed that Zn was deposited on the Cu surface during the electro deposition process in PKL solution. Using AAS, it has been measured the concentration of [Cu2+] as a reactant ion and the concentration of [Zn2+] as a product ion those have been tabulated and graphically discussed. The variation of pH has also been studied with time and which was also tabulated and graphically discussed.

  相似文献   
222.
The use of field robots can greatly decrease the amount of time, effort, and associated risk compared to if human workers were to carryout certain tasks such as disaster response. However, transportability and reliability remain two main issues for most current robot systems. To address the issue of transportability, we have developed a lightweight modularizable platform named AeroArm. To address the issue of reliability, we utilize a multimodal sensing approach, combining the use of multiple sensors and sensor types, and the use of different detection algorithms, as well as active continuous closed‐loop feedback to accurately estimate the state of the robot with respect to the environment. We used Challenge 2 of the 2017 Mohammed Bin Zayed International Robotics Competition as an example outdoor manipulation task, demonstrating the capabilities of our robot system and approach in achieving reliable performance in the fields, and ranked fifth place internationally in the competition.  相似文献   
223.
224.
225.
226.
227.
228.
229.
230.
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