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   558117篇
  免费   9387篇
  国内免费   2675篇
电工技术   11059篇
综合类   2453篇
化学工业   84523篇
金属工艺   21492篇
机械仪表   17065篇
建筑科学   15675篇
矿业工程   2886篇
能源动力   15545篇
轻工业   49074篇
水利工程   5705篇
石油天然气   11173篇
武器工业   247篇
无线电   63825篇
一般工业技术   105910篇
冶金工业   105207篇
原子能技术   10985篇
自动化技术   47355篇
  2022年   3965篇
  2021年   6015篇
  2020年   4336篇
  2019年   5265篇
  2018年   8594篇
  2017年   8547篇
  2016年   8786篇
  2015年   6656篇
  2014年   10673篇
  2013年   25890篇
  2012年   16567篇
  2011年   22236篇
  2010年   17547篇
  2009年   19446篇
  2008年   19799篇
  2007年   19465篇
  2006年   17234篇
  2005年   15770篇
  2004年   14663篇
  2003年   14357篇
  2002年   13589篇
  2001年   13630篇
  2000年   12755篇
  1999年   13558篇
  1998年   33734篇
  1997年   23640篇
  1996年   18196篇
  1995年   13661篇
  1994年   11761篇
  1993年   11412篇
  1992年   8221篇
  1991年   7641篇
  1990年   7490篇
  1989年   7169篇
  1988年   6603篇
  1987年   5856篇
  1986年   5730篇
  1985年   6317篇
  1984年   5940篇
  1983年   5202篇
  1982年   4930篇
  1981年   4982篇
  1980年   4722篇
  1979年   4615篇
  1978年   4414篇
  1977年   5342篇
  1976年   6982篇
  1975年   3799篇
  1974年   3554篇
  1973年   3668篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
81.
The physical widths of reference features incorporated into electrical linewidth test structures patterned in films of monocrystalline silicon have been determined from Kelvin voltage measurements. The films in which the test structures are patterned are electrically insulated from the bulk-silicon substrate by a layer of silicon dioxide provided by SIMOX (Separation by the IMplantation of OXygen) processing. The motivation is to facilitate the development of linewidth reference materials for critical-dimension (CD) metrology-instrument calibration. The selection of the (110) orientation of the starting silicon and the orientation of the structures' features relative to the crystal lattice enable a lattice-plane-selective etch to generate reference-feature properties of rectangular cross section and atomically planar sidewalls. These properties are highly desirable for CD applications in which feature widths are certified with nanometer-level uncertainty for use by a diverse range of CD instruments. End applications include the development and calibration of new generations of CD instruments directed at controlling processes for manufacturing devices having sub-quarter-micrometer features  相似文献   
82.
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   
83.
84.
85.
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   
86.
87.
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   
88.
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   
89.
90.
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   
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