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   747743篇
  免费   8953篇
  国内免费   1930篇
电工技术   13528篇
综合类   641篇
化学工业   116474篇
金属工艺   29454篇
机械仪表   23735篇
建筑科学   17552篇
矿业工程   4737篇
能源动力   19708篇
轻工业   64034篇
水利工程   8406篇
石油天然气   16560篇
武器工业   44篇
无线电   83805篇
一般工业技术   148668篇
冶金工业   130993篇
原子能技术   16878篇
自动化技术   63409篇
  2021年   6705篇
  2020年   5028篇
  2019年   6413篇
  2018年   10961篇
  2017年   11159篇
  2016年   11882篇
  2015年   7586篇
  2014年   12772篇
  2013年   34877篇
  2012年   20292篇
  2011年   27853篇
  2010年   22170篇
  2009年   24663篇
  2008年   25312篇
  2007年   25014篇
  2006年   22052篇
  2005年   20028篇
  2004年   19100篇
  2003年   18703篇
  2002年   17892篇
  2001年   17788篇
  2000年   16797篇
  1999年   16993篇
  1998年   39360篇
  1997年   28257篇
  1996年   21905篇
  1995年   16791篇
  1994年   15040篇
  1993年   14743篇
  1992年   11255篇
  1991年   10768篇
  1990年   10600篇
  1989年   10236篇
  1988年   9881篇
  1987年   8683篇
  1986年   8403篇
  1985年   9748篇
  1984年   8849篇
  1983年   8377篇
  1982年   7569篇
  1981年   7714篇
  1980年   7278篇
  1979年   7313篇
  1978年   7107篇
  1977年   7900篇
  1976年   9890篇
  1975年   6330篇
  1974年   6057篇
  1973年   6187篇
  1972年   5166篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
91.
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   
92.
Approaches to using visual language in a cultural context can be placed on a continuum, with global (universal) on one end and culture-focused on the other. Each approach reveals contrasting assumptions about three central design issues: perception, aesthetics and pragmatics. The global approach is characterized by attempts to invent an objective, universal visual language or to define such a language through perceptual principles and empirical research. The culture-focused perspective is founded on the principle that visual communication is intimately bound to experience and hence can function only within a given cultural context, to which designers must be sensitive. While the modernist, universal approach has been losing ground to the postmodern, culture-focused approach, the two complement each other in a variety of ways and, depending on the rhetorical situation, offer pragmatic benefits and drawbacks  相似文献   
93.
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   
94.
95.
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 95–112, March–April, 1994.  相似文献   
96.
97.
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   
98.
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   
99.
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   
100.
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