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   356367篇
  免费   3779篇
  国内免费   873篇
电工技术   6526篇
综合类   244篇
化学工业   54108篇
金属工艺   17971篇
机械仪表   13564篇
建筑科学   8123篇
矿业工程   2508篇
能源动力   7599篇
轻工业   27116篇
水利工程   4166篇
石油天然气   8209篇
武器工业   16篇
无线电   38061篇
一般工业技术   75034篇
冶金工业   56741篇
原子能技术   8415篇
自动化技术   32618篇
  2021年   2194篇
  2018年   11471篇
  2017年   11919篇
  2016年   8312篇
  2015年   3010篇
  2014年   4404篇
  2013年   12245篇
  2012年   9341篇
  2011年   16916篇
  2010年   14901篇
  2009年   14844篇
  2008年   14960篇
  2007年   16696篇
  2006年   7955篇
  2005年   10571篇
  2004年   8692篇
  2003年   8160篇
  2002年   7274篇
  2001年   6594篇
  2000年   6338篇
  1999年   6302篇
  1998年   14890篇
  1997年   11116篇
  1996年   8657篇
  1995年   6574篇
  1994年   5983篇
  1993年   5855篇
  1992年   4521篇
  1991年   4487篇
  1990年   4316篇
  1989年   4327篇
  1988年   4285篇
  1987年   3626篇
  1986年   3625篇
  1985年   4185篇
  1984年   3995篇
  1983年   3654篇
  1982年   3441篇
  1981年   3573篇
  1980年   3442篇
  1979年   3395篇
  1978年   3465篇
  1977年   3937篇
  1976年   5056篇
  1975年   3167篇
  1974年   3014篇
  1973年   3031篇
  1972年   2656篇
  1971年   2475篇
  1970年   2107篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
62.
63.
64.
Microbial fuel cell (MFC) is a promising technology for simultaneous wastewater treatment and energy harvesting. The properties of the anode material play a critical role in the performance of the MFC. In this study, graphene oxide was prepared by a modified hummer's method. A thin layer of graphene oxide was incorporated on the carbon brush using an electrophoretic technique. The deoxygenated graphene oxide formed on the surface of the carbon brush (RGO-CB) was investigated as a bio-anode in MFC operated with real wastewater. The performance of the MFC using the RGO-CB was compared with that using plain carbon brush anode (PCB). Results showed that electrophoretic deposition of graphene oxide on the surface of carbon brush significantly enhanced the performance of the MFC, where the power density increased more than 10 times (from 33 mWm?2 to 381 mWm?2). Although the COD removal was nearly similar for the two MFCs, i.e., with PCB and RGO-CB; the columbic efficiency significantly increased in the case of RGO-CB anode. The improved performance in the case of the modified electrode was related to the role of the graphene in improving the electron transfer from the microorganism to the anode surface, as confirmed from the electrochemical impedance spectroscopy measurements.  相似文献   
65.
Wireless Personal Communications - In this article compact multiple input multiple output (MIMO) antenna with triple notch at the ultra-wideband application having two identical monopole antennas...  相似文献   
66.
Russian Journal of Non-Ferrous Metals - The synthesis and sintering of the (AlN)x(SiC)1 – x solid solution have been studied under conditions of self-propagating high-temperature synthesis...  相似文献   
67.
N. Boukortt  S. Patan&#;  G. Crupi 《SILICON》2020,12(7):1585-1591
The miniaturization has become a key word for advanced integrated circuits over the last few years. It is within this context that the fin field effect tra  相似文献   
68.
An alternative Equivalent Electrical Circuit for Proton Exchange Membrane Fuel Cells is modelled in this study. Both I–V characteristics and H2 consumptions corresponding to generated power under load and no-load conditions are investigated. For this purpose, H2 consumptions and I–V characteristics of three different sized PEMFCs are tested. There is a very good harmony between the model results and measured values (relative error %0.7, %6.4 and %2.5 for FC-A, FC-B and FC-C respectively). In the proposed model current passes only on parallel resistance and not on serial resistance at no-load condition. Thus, a FC with higher parallel resistance should be preferred. Another key output of this study is that based on the proposed model, performance comparison of FCs can be performed with the parameters defined in this work. Proposals made in this study can easily be used for performance analysis of FCs under for both steady state and transient analysis.  相似文献   
69.
70.
An automated system for integrated electrophysical and optical studies of semiconductor nanoheterostructures, which operates in a wide temperature range from 15 to 475 K, is designed. The setup is intended to measure the temperature and frequency admittance and electroluminescence spectra of light-emitting diode and laser chips formed on substrates of diameter up to 50.2 mm, and the distribution of parameters over the wafer. The setup includes the closed-cycle helium cryogenic station, LCR meter, and temperature controller. The characterization results of nanoheterostructures with InGaN/GaN multiple quantum wells, which are used for creating highly efficient white and blue light-emitting diodes, are presented.  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