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   23180篇
  免费   332篇
  国内免费   122篇
电工技术   497篇
综合类   64篇
化学工业   3165篇
金属工艺   939篇
机械仪表   657篇
建筑科学   545篇
矿业工程   67篇
能源动力   599篇
轻工业   1832篇
水利工程   212篇
石油天然气   179篇
武器工业   1篇
无线电   2586篇
一般工业技术   4067篇
冶金工业   6129篇
原子能技术   419篇
自动化技术   1676篇
  2021年   149篇
  2020年   114篇
  2019年   157篇
  2018年   229篇
  2017年   229篇
  2016年   255篇
  2015年   177篇
  2014年   296篇
  2013年   819篇
  2012年   507篇
  2011年   774篇
  2010年   558篇
  2009年   621篇
  2008年   715篇
  2007年   745篇
  2006年   629篇
  2005年   718篇
  2004年   587篇
  2003年   634篇
  2002年   675篇
  2001年   670篇
  2000年   599篇
  1999年   614篇
  1998年   2158篇
  1997年   1402篇
  1996年   1043篇
  1995年   718篇
  1994年   618篇
  1993年   640篇
  1992年   358篇
  1991年   344篇
  1990年   341篇
  1989年   343篇
  1988年   292篇
  1987年   267篇
  1986年   245篇
  1985年   275篇
  1984年   215篇
  1983年   200篇
  1982年   185篇
  1981年   217篇
  1980年   202篇
  1979年   164篇
  1978年   152篇
  1977年   277篇
  1976年   385篇
  1975年   127篇
  1974年   109篇
  1973年   117篇
  1972年   90篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
31.
U. Schmoch 《Scientometrics》1993,26(1):193-211
The use of references of patent search reports as transfer indications needs a good theoretical understanding of the underlying examination procedures. On this background, different patent indicators based on sample patents and on respective references can be established and combined to a network which gives an interesting insight into the complex process of knowledge transfer from science to technology.  相似文献   
32.
33.
34.
Today patients want to change their Christian names not so much for social support but in order to obtain sex change operations. For this reason among others we caution against casual and careless evaluations and plead for conscientiousness and thoroughness. The spectrum of 16 evaluation cases in the year 1995 is presented. Following this and looking for guiding principles, the most important aspects are discussed: the dilatable frame of the written law, the examiner's diagnostic process, the duty of being well informed, reconstruction of development as the first goal of examination, real-life self-testing and therapy, the obligation to report one's own findings, change of Christian name and indication of operation, evaluation for gender changing, problems of the judge-expert relationship and of future development.  相似文献   
35.
The synthesis of the structure of the power system stabiliser (PSS) and its parametrization are based entirely on methods of linear system theory. Thus the desired effect of the PSS is limited to a bounded area around one system operating point. The use of a controller based on fuzzy set theory introduces an event controlled excitation of the synchronous machine taking into account the power system operation. The desired response of the fuzzy controller is given by a set of rules which are obtained from the limits of the voltage regulator and the undesired performance of the conventional excitation control. A fuzzy controller has been developed for which simulation results are provided. These results support the concept of a fuzzy controller for the purpose of excitation control. They show that a well designed fuzzy controller is superior to a fast excitation control with an additional PSS  相似文献   
36.
37.
New spectrophotometric methods for the assay of some antioxidants have been developed using potassium permanganate and metol (p-N-methyl amino phenol). Metol is oxidised at pH 3.0 with potassium permanganate and coupled with antioxidants to give λmax at 560 nm for propyl gallate and gallic acid and 510nm for butylated hydroxy anisole. The method is simple, sensitive, reproducible and accurate within ±1% and applicable to the assay of antioxidants (gallic acid, propyl gallate and butylated hydroxy anisole) in oils and fats.  相似文献   
38.
The theory of deconvolution of infra-red spectra is presented and illustrated using milk protein spectra. The advantage of this method is impressively demonstrated and its relevance for dairy farming shown using a simple example, the cooling of milk.  相似文献   
39.
40.
The Grimsel Test Site (Felslabor Grimsel — FLG) is situated at a depth of 450 m in the Juchlistock massif of the Bernese Oberland. It is managed by the National Cooperative for the Storage of Radioactive Waste (NAGRA-Switzerland).By means of a heater test, the power output of canisters filled with high-level waste is simulated. This heater test is performed by the German Gesellschaft für Strahlen- und Umweltforschung — GSF. Two electrical heaters, with a heatable length of 6 m, a diameter of 0.3 m and an available power of 4 kW/m, are installed in two vertical boreholes. One of them is located in the granite adjacent to a strongly fractured lamprophyre vein, the other one directly within this disturbed zone. They are operating since August 1986.The thermo-mechanical reaction of the rock mass is registered by a large number of measurement devices which are installed in an array of instrument boreholes around the heaters. They record the deformation and the alteration of rock stresses, the pore water pressure and the water conductivity caused by heating.  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