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   546521篇
  免费   8437篇
  国内免费   1489篇
电工技术   9707篇
综合类   534篇
化学工业   83388篇
金属工艺   20314篇
机械仪表   15669篇
建筑科学   13358篇
矿业工程   2313篇
能源动力   14983篇
轻工业   51070篇
水利工程   5454篇
石油天然气   9427篇
武器工业   39篇
无线电   60790篇
一般工业技术   105069篇
冶金工业   107344篇
原子能技术   10630篇
自动化技术   46358篇
  2022年   3475篇
  2021年   5559篇
  2020年   4054篇
  2019年   5126篇
  2018年   8811篇
  2017年   8579篇
  2016年   8966篇
  2015年   6310篇
  2014年   10223篇
  2013年   25909篇
  2012年   15929篇
  2011年   21380篇
  2010年   16794篇
  2009年   18584篇
  2008年   18989篇
  2007年   18569篇
  2006年   16039篇
  2005年   14642篇
  2004年   14013篇
  2003年   13793篇
  2002年   12969篇
  2001年   13021篇
  2000年   12055篇
  1999年   12784篇
  1998年   34057篇
  1997年   23716篇
  1996年   17982篇
  1995年   13334篇
  1994年   11529篇
  1993年   11216篇
  1992年   7982篇
  1991年   7475篇
  1990年   7309篇
  1989年   7069篇
  1988年   6537篇
  1987年   5822篇
  1986年   5711篇
  1985年   6333篇
  1984年   5959篇
  1983年   5216篇
  1982年   4950篇
  1981年   5025篇
  1980年   4762篇
  1979年   4652篇
  1978年   4448篇
  1977年   5437篇
  1976年   7158篇
  1975年   3837篇
  1974年   3581篇
  1973年   3710篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Photonic networks based on the optical path concept and wavelength division multiplexing (WDM) technology require unique operation, administration, and maintenance (OAM) functions. In order to realize the required OAM functions, the optical path network must support an effective management information transfer method. The method that superimposes a pilot tone on the optical signal appears very interesting for optical path overhead transfer. The pilot tone transmission capacity is determined by the carrier to noise ratio which depends on the power spectral density of the optical signal. The pilot tone transmission capacity of an optical path network employing WDM technology is elucidated; 4.5 kb/s transmission can be realized when the pilot tone modulation index is set at 3%  相似文献   
82.
83.
84.
Carstensen and Rhodes1 have suggested that when, in stability programs, assays cannot be performed immediately after the protocol-designated storage time, then freezing them until such a time when assays can be performed would be a reasonable manner to retain the protocol schedule. They caution, however, that such a procedure may not be valid for dissolution data. The article to follow deals with real-time data showing that such a process is feasible for Nalidixic Acid tablets (and presumably for other tablets as well), and that, furthermore, the dissolution pattern would seem to be “frozen” as well.  相似文献   
85.
86.
Abstract This article presents a study of a large scale incorporation of one data acquisitionsystem into physics teaching in Israel. By 1994 about 30% of the schools throughout the country used the V-scope, a 3-D multibody motion tracing system, in their lab programme. The views and reactions of post-training teachers, experienced teachers and students on various aspects of using the system are described, analysed and compared.  相似文献   
87.
Gilbenclamide, a widely used potent hypoglycaemic agent was solubllized using β -Cyclodextrin and β -Cyclodextrin derivatives. Complexes were prepared by kneading method in a molar ratio of 1:1 of the drug and the cyclodextrlns respectively. The Glibenclamide β -Cyelocextrin complex was characterized and evaluated by I.R. studies, Differential Scanning Calorimotry 6 X-ray diffractometry. The in-vitro dissolution rates of drug from inclusion complexes of β Cyclodextrins and its derivatives were compared. A significant Improvement In dissolution lor, rates of Gllbenclamide was observed with Inclusion complexes of all the Cyclodextrins. However, the solubilizing effect was more in case of β-Cyclodextrin derivatives.  相似文献   
88.
89.
The paper presents the results of research in the convection drying of unidirectional glass fibre bobbins on the basis of which the relations are suggested required to calculate the process of drying in the design of drying equipment.  相似文献   
90.
No generally accepted principles and guidelines currently exist to help engineers design local interaction mechanisms that result in a desired global behavior. However, several communities have developed ways of approaching this problem in the context of niched application areas. Because the ideas underlying these approaches are often obscured or underemphasized in technical papers, the authors review the role of self-organization in their work. They provide a better picture of the status of the emerging field of self-organizing systems or autonomic computing.  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