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   526149篇
  免费   7099篇
  国内免费   1470篇
电工技术   9564篇
综合类   527篇
化学工业   78876篇
金属工艺   19971篇
机械仪表   15212篇
建筑科学   12691篇
矿业工程   2269篇
能源动力   14531篇
轻工业   47099篇
水利工程   5223篇
石油天然气   9334篇
武器工业   37篇
无线电   59973篇
一般工业技术   101820篇
冶金工业   103828篇
原子能技术   10564篇
自动化技术   43199篇
  2022年   3162篇
  2021年   4899篇
  2020年   3483篇
  2019年   4555篇
  2018年   7811篇
  2017年   7616篇
  2016年   7938篇
  2015年   5563篇
  2014年   9247篇
  2013年   24094篇
  2012年   14636篇
  2011年   20159篇
  2010年   15812篇
  2009年   17714篇
  2008年   18117篇
  2007年   17805篇
  2006年   15535篇
  2005年   14249篇
  2004年   13628篇
  2003年   13413篇
  2002年   12649篇
  2001年   12844篇
  2000年   11887篇
  1999年   12613篇
  1998年   32883篇
  1997年   22947篇
  1996年   17484篇
  1995年   13058篇
  1994年   11301篇
  1993年   10988篇
  1992年   7923篇
  1991年   7419篇
  1990年   7271篇
  1989年   7021篇
  1988年   6481篇
  1987年   5773篇
  1986年   5663篇
  1985年   6279篇
  1984年   5917篇
  1983年   5187篇
  1982年   4911篇
  1981年   4991篇
  1980年   4729篇
  1979年   4627篇
  1978年   4413篇
  1977年   5341篇
  1976年   6982篇
  1975年   3805篇
  1974年   3554篇
  1973年   3675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