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   298715篇
  免费   3951篇
  国内免费   860篇
电工技术   5258篇
综合类   176篇
化学工业   47336篇
金属工艺   12237篇
机械仪表   8947篇
建筑科学   7051篇
矿业工程   1901篇
能源动力   7368篇
轻工业   27010篇
水利工程   3373篇
石油天然气   7165篇
武器工业   16篇
无线电   32922篇
一般工业技术   59487篇
冶金工业   52776篇
原子能技术   7710篇
自动化技术   22793篇
  2021年   2581篇
  2019年   2343篇
  2018年   4205篇
  2017年   4111篇
  2016年   4359篇
  2015年   2731篇
  2014年   4648篇
  2013年   12845篇
  2012年   7302篇
  2011年   9836篇
  2010年   8070篇
  2009年   9127篇
  2008年   9359篇
  2007年   9169篇
  2006年   8128篇
  2005年   7549篇
  2004年   7026篇
  2003年   6751篇
  2002年   6790篇
  2001年   6617篇
  2000年   6300篇
  1999年   6365篇
  1998年   15072篇
  1997年   11244篇
  1996年   8790篇
  1995年   6726篇
  1994年   6079篇
  1993年   5937篇
  1992年   4606篇
  1991年   4575篇
  1990年   4389篇
  1989年   4403篇
  1988年   4376篇
  1987年   3702篇
  1986年   3679篇
  1985年   4262篇
  1984年   4048篇
  1983年   3723篇
  1982年   3509篇
  1981年   3634篇
  1980年   3490篇
  1979年   3415篇
  1978年   3485篇
  1977年   3976篇
  1976年   5106篇
  1975年   3187篇
  1974年   3032篇
  1973年   3049篇
  1972年   2669篇
  1971年   2486篇
排序方式: 共有10000条查询结果,搜索用时 890 毫秒
81.
This study deals with the utility of mini spray dryer process to improve the dispersibility, of graphene oxide(GO) and its application for high-performance supercapacitor. Initially, the neutral solution of GO was obtained using the modified Hummer's method. After this, the prepared GO solution was processed by mini spray dryer to obtain a more purified, lighter, and dispersed form of GO which is named as spray dryer processed GO (SPGO). The SPGO thus obtained showed excellent dispersibility behavior with various solvents, which is not found in case of conventional oven drying. Furthermore, utility of SPGO and its reduced form (r-SPGO) for supercapacitor applications have been investigated. Results obtained from the cyclic voltammetry(CV) analysis, impedance, and charge-discharge behavior of supercapacitor fabricated using r-SPGO shows enhanced features. Therefore, the simple spray dried GO and its reduced form, that is, r-SPGO can be utilized as a potential candidate for the supercapacitor application. Herein, as synthesized SPGO exhibited the specific capacitance of 12.07 and 37.6 F/g with PVA-H3PO4 and 1 mol/L H3PO4, respectively, at a scan rate of 5 mV/s. On the other hand, reduced form of SPGO, that is, r-SPGO showed the specific capacitance of 27.16 and 230 F/g with PVA-H3PO4 and 1 mol/L H3PO4, respectively.  相似文献   
82.
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   
83.
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   
84.
85.
Intended learning outcomes (ILOs) indicate what learners will be able to achieve after they are taught. Traditionally, ILOs are expressed as plain text or unstructured documents. What if all ILOs of a specific course of study can be conceptualized through a structured diagrammatic technique? It was hypothesized that learners can benefit from this conceptualization in learning, especially in self‐regulated learning. The aim of this study was to investigate whether the ILOs represented in unstructured or structured formats can facilitate learners to identify learning paths. The results revealed that the mean ratings of all learning paths were statistically significantly higher with structured ILOs.  相似文献   
86.
87.
88.
89.
90.
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