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   588929篇
  免费   7728篇
  国内免费   1028篇
电工技术   10645篇
综合类   476篇
化学工业   94954篇
金属工艺   23621篇
机械仪表   18956篇
建筑科学   13329篇
矿业工程   4361篇
能源动力   14920篇
轻工业   50428篇
水利工程   7178篇
石油天然气   15075篇
武器工业   40篇
无线电   61285篇
一般工业技术   119635篇
冶金工业   99078篇
原子能技术   14751篇
自动化技术   48953篇
  2021年   6197篇
  2020年   4595篇
  2019年   5889篇
  2018年   10258篇
  2017年   10427篇
  2016年   10942篇
  2015年   6891篇
  2014年   11257篇
  2013年   28079篇
  2012年   17276篇
  2011年   22430篇
  2010年   18062篇
  2009年   19796篇
  2008年   20080篇
  2007年   19668篇
  2006年   16894篇
  2005年   15253篇
  2004年   14465篇
  2003年   14142篇
  2002年   13624篇
  2001年   13080篇
  2000年   12524篇
  1999年   12248篇
  1998年   28795篇
  1997年   20796篇
  1996年   16115篇
  1995年   12304篇
  1994年   11074篇
  1993年   10838篇
  1992年   8400篇
  1991年   8161篇
  1990年   8039篇
  1989年   7815篇
  1988年   7542篇
  1987年   6805篇
  1986年   6583篇
  1985年   7436篇
  1984年   6742篇
  1983年   6469篇
  1982年   5805篇
  1981年   5946篇
  1980年   5676篇
  1979年   5753篇
  1978年   5688篇
  1977年   6259篇
  1976年   7829篇
  1975年   5137篇
  1974年   4920篇
  1973年   5009篇
  1972年   4283篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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   
62.
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   
63.
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   
64.
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   
65.
66.
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 95–112, March–April, 1994.  相似文献   
67.
68.
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   
69.
An extended logistic model with a varying asymptotic upper bound for long-range peak demand forecasting is described. The model has been applied to a typical fast growing system, the Saudi Consolidated Electric Company. The forecasts are compared with actual demands and with those obtained from classical forecasting methods. The model gave relatively accurate peak demand forecasts compared with other classical methods. The model with a single load observation is capable of producing several peak demand forecasts corresponding to different levels of maximum temperature and various levels of social activity. The forecasts produced by the model were also stable irrespective of the length of the ex-post simulation period  相似文献   
70.
An experimental and theoretical analysis of the nonlinear coupling mechanism between the two solitary pulses circulating in a two-color femtosecond laser is presented. Two operation regimes; synchronized; and nonsynchronized; and a hysteresis of the transition between the two regimes are clearly observed; while independent modelocking and tunability of the output pulse trains is found in both regimes. Pulses in the range from 15 to 100 fs are synchronized with a timing jitter below 2 fs. The combined effects of cross-phase modulation and negative group velocity dispersion are shown to be responsible for the strong pulse correlation in the synchronized regime. Our experimental observations are in agreement with numerical simulations, thus confirming the theoretical model  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