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   555581篇
  免费   8270篇
  国内免费   1512篇
电工技术   9895篇
综合类   580篇
化学工业   84913篇
金属工艺   20517篇
机械仪表   15746篇
建筑科学   14514篇
矿业工程   2353篇
能源动力   15354篇
轻工业   49420篇
水利工程   5477篇
石油天然气   9496篇
武器工业   40篇
无线电   62248篇
一般工业技术   107097篇
冶金工业   108649篇
原子能技术   10764篇
自动化技术   48300篇
  2022年   3535篇
  2021年   5514篇
  2020年   3923篇
  2019年   5083篇
  2018年   8436篇
  2017年   8227篇
  2016年   8748篇
  2015年   6284篇
  2014年   10167篇
  2013年   25901篇
  2012年   16092篇
  2011年   22040篇
  2010年   17166篇
  2009年   19048篇
  2008年   19685篇
  2007年   19235篇
  2006年   16816篇
  2005年   15341篇
  2004年   14592篇
  2003年   14276篇
  2002年   13479篇
  2001年   13340篇
  2000年   12382篇
  1999年   13115篇
  1998年   33453篇
  1997年   23412篇
  1996年   17960篇
  1995年   13479篇
  1994年   11705篇
  1993年   11415篇
  1992年   8292篇
  1991年   7652篇
  1990年   7566篇
  1989年   7321篇
  1988年   6719篇
  1987年   6070篇
  1986年   5940篇
  1985年   6584篇
  1984年   6186篇
  1983年   5422篇
  1982年   5137篇
  1981年   5177篇
  1980年   4890篇
  1979年   4779篇
  1978年   4566篇
  1977年   5482篇
  1976年   7137篇
  1975年   3930篇
  1974年   3658篇
  1973年   3770篇
排序方式: 共有10000条查询结果,搜索用时 0 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.
Midrange outsourcers offer small to midsize companies the advanced technologies employed by major corporations, with the added benefits of creative pricing strategies.  相似文献   
86.
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   
87.
88.
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   
89.
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   
90.
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