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   648505篇
  免费   7321篇
  国内免费   2121篇
电工技术   11996篇
综合类   585篇
化学工业   98083篇
金属工艺   27902篇
机械仪表   21034篇
建筑科学   14157篇
矿业工程   4427篇
能源动力   16828篇
轻工业   50227篇
水利工程   7506篇
石油天然气   15497篇
武器工业   54篇
无线电   72724篇
一般工业技术   133760篇
冶金工业   115897篇
原子能技术   15695篇
自动化技术   51575篇
  2021年   6006篇
  2020年   4434篇
  2019年   5779篇
  2018年   10052篇
  2017年   10241篇
  2016年   10748篇
  2015年   6773篇
  2014年   11432篇
  2013年   29851篇
  2012年   17761篇
  2011年   24113篇
  2010年   19433篇
  2009年   21804篇
  2008年   22148篇
  2007年   22011篇
  2006年   19215篇
  2005年   17363篇
  2004年   16507篇
  2003年   16091篇
  2002年   15365篇
  2001年   15157篇
  2000年   14486篇
  1999年   14509篇
  1998年   35049篇
  1997年   24926篇
  1996年   19437篇
  1995年   14533篇
  1994年   13129篇
  1993年   12788篇
  1992年   9616篇
  1991年   9382篇
  1990年   9236篇
  1989年   8828篇
  1988年   8431篇
  1987年   7438篇
  1986年   7264篇
  1985年   8132篇
  1984年   7353篇
  1983年   7012篇
  1982年   6358篇
  1981年   6464篇
  1980年   6084篇
  1979年   6124篇
  1978年   5999篇
  1977年   6628篇
  1976年   8512篇
  1975年   5347篇
  1974年   5140篇
  1973年   5196篇
  1972年   4440篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Two novel configurations for digitally tunable optical filters based on arrayed-waveguide grating (AWG) multiplexers are described in detail with emphasis on the connection of the AWG multiplexer and optical switches. Performance comparisons show that conventional configurations are disadvantaged by the switch size required and loss imbalance among the optical frequency-division-multiplexed (FDM) channels; the proposed configurations require only O(√(N)) switch elements to select one of N FDM channels, and the loss imbalance is lower by up to 75% in decibel  相似文献   
72.
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   
73.
A new commercially available diode model is described. This unified model is capable of simulating the widest range of diode technologies of any presently available. The emphasis of this paper is on describing the model's extensive features and flexibility in the different domains of operation and is of particular interest in power applications  相似文献   
74.
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   
75.
The capacitive idling converters derived from the Cuk, SEPIC, Zeta, and flyback topologies allow soft commutation of power switches without the need for additional circuitry, making it possible to increase the switching frequency while maintaining high efficiency  相似文献   
76.
Pipelining and bypassing in a VLIW processor   总被引:1,自引:0,他引:1  
This short note describes issues involved in the bypassing mechanism for a very long instruction word (VLIW) processor and its relation to the pipeline structure of the processor. The authors first describe the pipeline structure of their processor and analyze its performance and compare it to typical RISC-style pipeline structures given the context of a processor with multiple functional units. Next they study the performance effects of various bypassing schemes in terms of their effectiveness in resolving pipeline data hazards and their effect on the processor cycle time  相似文献   
77.
78.
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 95–112, March–April, 1994.  相似文献   
79.
80.
The process of combustion of homogeneous and heterogeneous nongasifying and slightly gasifying systems over the range of a number of parameters characterizing the reactive composition and the conditions for the arrangement of the combustion process is studied by using thermocouple and optical methods. The regions of the implementation of different combustion regimes, namely, steady, pulsating, multiple-point, and spin, are determined experimentally.Institute of Structural Macrokinetics, Russian Academy of Sciences, Chernogolovka. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 65, No. 4, pp. 407–411, October, 1993.  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