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   417096篇
  免费   4724篇
  国内免费   1218篇
电工技术   6982篇
综合类   2483篇
化学工业   61011篇
金属工艺   21026篇
机械仪表   16082篇
建筑科学   9736篇
矿业工程   2997篇
能源动力   8394篇
轻工业   29301篇
水利工程   5019篇
石油天然气   8441篇
武器工业   17篇
无线电   45022篇
一般工业技术   86061篇
冶金工业   58931篇
原子能技术   8597篇
自动化技术   52938篇
  2021年   2139篇
  2018年   22632篇
  2017年   22163篇
  2016年   16091篇
  2015年   3490篇
  2014年   4652篇
  2013年   12499篇
  2012年   11610篇
  2011年   23857篇
  2010年   20818篇
  2009年   18956篇
  2008年   19886篇
  2007年   22171篇
  2006年   8198篇
  2005年   11399篇
  2004年   9474篇
  2003年   9033篇
  2002年   7744篇
  2001年   6739篇
  2000年   6535篇
  1999年   6374篇
  1998年   14883篇
  1997年   11136篇
  1996年   8691篇
  1995年   6604篇
  1994年   6012篇
  1993年   5808篇
  1992年   4472篇
  1991年   4473篇
  1990年   4273篇
  1989年   4274篇
  1988年   4228篇
  1987年   3568篇
  1986年   3587篇
  1985年   4132篇
  1984年   3943篇
  1983年   3584篇
  1982年   3393篇
  1981年   3532篇
  1980年   3394篇
  1979年   3327篇
  1978年   3441篇
  1977年   3886篇
  1976年   5011篇
  1975年   3127篇
  1974年   2982篇
  1973年   2993篇
  1972年   2625篇
  1971年   2435篇
  1970年   2056篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
61.
Bochkareva  N. I.  Ivanov  A. M.  Klochkov  A. V.  Kogotkov  V. S.  Rebane  Yu. T.  Virko  M. V.  Shreter  Y. G. 《Semiconductors》2015,49(6):827-835
Semiconductors - It is shown that the emission efficiency and the 1/f noise level in light-emitting diodes with InGaN/GaN quantum wells correlate with how the differential resistance of a diode...  相似文献   
62.
63.
64.
65.
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   
66.
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   
67.
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   
68.
Catalysis in Industry - The oligomerization of 1-pentene is an efficient process for producing environmentally friendly high-quality fuel components. The catalytic properties of FAU, OFF, MOR, BEA,...  相似文献   
69.
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   
70.
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   
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