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   83861篇
  免费   959篇
  国内免费   407篇
电工技术   789篇
综合类   2316篇
化学工业   11420篇
金属工艺   4788篇
机械仪表   3035篇
建筑科学   2158篇
矿业工程   562篇
能源动力   1111篇
轻工业   3614篇
水利工程   1266篇
石油天然气   342篇
无线电   9244篇
一般工业技术   16298篇
冶金工业   2709篇
原子能技术   260篇
自动化技术   25315篇
  2023年   8篇
  2022年   10篇
  2021年   13篇
  2020年   13篇
  2019年   10篇
  2018年   14457篇
  2017年   13381篇
  2016年   9960篇
  2015年   611篇
  2014年   231篇
  2013年   206篇
  2012年   3139篇
  2011年   9396篇
  2010年   8272篇
  2009年   5540篇
  2008年   6771篇
  2007年   7775篇
  2006年   116篇
  2005年   1210篇
  2004年   1126篇
  2003年   1173篇
  2002年   540篇
  2001年   97篇
  2000年   178篇
  1999年   59篇
  1998年   82篇
  1997年   50篇
  1996年   55篇
  1995年   18篇
  1994年   20篇
  1993年   14篇
  1992年   15篇
  1991年   24篇
  1988年   14篇
  1969年   24篇
  1968年   43篇
  1967年   33篇
  1966年   42篇
  1965年   44篇
  1964年   11篇
  1963年   28篇
  1962年   22篇
  1961年   18篇
  1960年   30篇
  1959年   35篇
  1958年   37篇
  1957年   36篇
  1956年   34篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
231.
232.
When deploying TTCN-3 at Nokia, we converted two TTCN-2 test systems to TTCN-3. We explain to which extend we have been able to do the conversion automatically. The conversion tool used provided a syntactically and semantically correct conversion of the TTCN-2 code. We define some improvements made on the tool to increase readability and maintainability of the resulting code. We cover aspects of converting also the non-TTCN-2 parts and describe the experiences we made as a set of lessons learnt.  相似文献   
233.
234.
Computer vision systems   总被引:1,自引:0,他引:1  
  相似文献   
235.
This paper presents the concept of a process signature for the use of online signature analysis and defect detection in the layered manufacturing (LM) of ceramic sensors and actuators. To achieve the high quality of parts built by the fused deposition of ceramics (FDC), an online process-monitoring system is implemented to detect the processing defects. Using a process signature extracted from the image of a layer captured by the monitoring system, an ideal image is created that is then compared to the original image to detect and identify the defects. Some results of signature analysis and defect detection for single-material and multi-material parts are also presented.Received: 22 July 1999, Accepted: 21 October 2001, Published online: 29 October 2003 Correspondence to: Mohsen A. JafariThis work was supported by the Office of Naval Research under grant # N-0014-96-1-1175. Ref. US Patent # S-5738817, April 14, 1998.  相似文献   
236.
237.
238.
e-Government systems differ from commercial information systems (IS) in that they frequently encompass strategic goals that go beyond efficiency, effectiveness and economy, and include political and social objectives such as trust in government, social inclusion, community regeneration, community well-being and sustainability. Designing e-Government systems that help to meet these objectives is a significant challenge for the future. This paper develops an evaluative design framework for e-Government projects that complements traditional approaches to IS evaluation. The framework is based upon Moor's concept of public value. It focuses upon citizens' and clients' experiences of service provision and service outcomes as contributors to the formation of public trust. Trust is shown to be related to the extent to which people feel that an e-Government service enhances their sense of being well-informed, gives them greater personal control, and provides them with a sense of influence or contingency. The framework's development and validation are founded upon analyses of a two live case studies in south-east England and London, U.K.  相似文献   
239.
The effect of carbon surface oxidation on platinum supported carbon particles (Pt/C) with nitric acid was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, polarization experiments and chronoamperometry. Cyclic voltammograms, polarization curves and electrochemical impedance spectra showed that the treated catalyst had much larger active surface area and higher ionic conductivity than the untreated catalyst, and provided enhanced performance for oxygen reduction. The formation of acidic groups was examined by IR spectra. The Pt/C surface oxidation had a large effect on the performance of a gas diffusion electrode for oxygen reduction reaction.  相似文献   
240.
We report on potential-dependent in situ SFG and DFG spectroscopy carried out at Au(111), Au(210), polycrystalline Au, Au–Cu and Au–Ag–Cu electrodes in contact with aqueous solutions containing CN and 4-cyanopyridine (4CP). Spectroelectrochemical work was complemented by cyclic voltammetry. The chief stress has been placed on systematising and quantifying the interaction between 4CP and CN and the attending effects on the vibrational and electronic structures of the interface. The voltammetric behaviour of the investigated electrodes, modified by the addition of 4CP to the CN electrolyte, denote changes in the CN adsorption characteristics and effects of the adsorbed CN layer on the electrodic reactivity of 4CP. The differences among the investigated electrodes can be explained in terms of their respective degrees of atomic packing or with alloying effects on the stability of adsorbed CN. The potential-dependent spectra have been analysed quantitatively with a model for the second order non linear susceptibility accounting for vibrational and electronic effects. The spectral changes induced by addition of 4CP denote interaction of the aromatic with the electrode through the CN monolayer. The non-resonant contribution yields information on the effects of 4CP on the fine structure of the bound electron density of states.  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