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   654407篇
  免费   7003篇
  国内免费   1115篇
电工技术   11755篇
综合类   552篇
化学工业   102971篇
金属工艺   27750篇
机械仪表   20914篇
建筑科学   14489篇
矿业工程   5158篇
能源动力   16047篇
轻工业   50902篇
水利工程   8343篇
石油天然气   18435篇
武器工业   42篇
无线电   68293篇
一般工业技术   135187篇
冶金工业   112218篇
原子能技术   17335篇
自动化技术   52134篇
  2021年   6050篇
  2019年   5823篇
  2018年   10247篇
  2017年   10427篇
  2016年   10940篇
  2015年   6735篇
  2014年   11489篇
  2013年   29339篇
  2012年   17661篇
  2011年   23658篇
  2010年   19007篇
  2009年   21217篇
  2008年   21536篇
  2007年   21190篇
  2006年   18460篇
  2005年   16779篇
  2004年   15953篇
  2003年   15568篇
  2002年   15129篇
  2001年   14742篇
  2000年   14136篇
  1999年   13863篇
  1998年   32339篇
  1997年   23355篇
  1996年   18119篇
  1995年   13877篇
  1994年   12517篇
  1993年   12335篇
  1992年   9581篇
  1991年   9364篇
  1990年   9264篇
  1989年   8934篇
  1988年   8627篇
  1987年   7881篇
  1986年   7652篇
  1985年   8555篇
  1984年   7800篇
  1983年   7534篇
  1982年   6802篇
  1981年   6989篇
  1980年   6717篇
  1979年   6912篇
  1978年   6906篇
  1977年   7522篇
  1976年   9450篇
  1975年   6289篇
  1974年   6095篇
  1973年   6203篇
  1972年   5397篇
  1971年   4978篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
71.
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   
72.
Conclusions 1. Use of dewatering systems based on voidless drainage is most effective when dewatering slightly permeable soils in regions with a deep seasonal frost. 2. Two-story drainage with the upper and lower stories spaced 30 m apart accelerates the discharge of gravitational water from the arable layer. Results of observations on two-story drainage in experimental-production sections indicated that it discharges 2 – 3.8 times more water than systematic tubular drainage with an interdrain spacing of 10 m and a 0.2-m thick three-dimensional filter of a sandy-gravelly mixture. 3. It is recommended to use crushed stone and porous-clay gravel with a fineness of 10 – 20 mm as a filler. In that case, protection of the drain filler is, as a rule, required only from the intrusion of soil from above during construction in cohesive soils with a plasticity indexW p≥7. 4. seepage rate in a voidless drain should be lower than the scouring velocity for the soil in which the voidless drainage is placed. In the opposite case, it is necessary to lower the grade of the drains or select a filler gradation such that the seepage rate in the drain be lower than the scouring velocity. Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 8, pp. 41–43, August, 1998.  相似文献   
73.
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   
74.
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   
75.
76.
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 95–112, March–April, 1994.  相似文献   
77.
78.
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   
79.
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   
80.
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