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   770814篇
  免费   8470篇
  国内免费   1645篇
电工技术   13155篇
综合类   2898篇
化学工业   120089篇
金属工艺   35134篇
机械仪表   25551篇
建筑科学   17402篇
矿业工程   6605篇
能源动力   18015篇
轻工业   55297篇
水利工程   10248篇
石油天然气   20521篇
武器工业   59篇
无线电   79106篇
一般工业技术   161827篇
冶金工业   115009篇
原子能技术   19154篇
自动化技术   80859篇
  2021年   6820篇
  2019年   6448篇
  2018年   24815篇
  2017年   23896篇
  2016年   21502篇
  2015年   8139篇
  2014年   12989篇
  2013年   31813篇
  2012年   22235篇
  2011年   34035篇
  2010年   28072篇
  2009年   28055篇
  2008年   29365篇
  2007年   29796篇
  2006年   19642篇
  2005年   18648篇
  2004年   17824篇
  2003年   17516篇
  2002年   16415篇
  2001年   15489篇
  2000年   15027篇
  1999年   14429篇
  1998年   32193篇
  1997年   23591篇
  1996年   18353篇
  1995年   14164篇
  1994年   12974篇
  1993年   12699篇
  1992年   10009篇
  1991年   9845篇
  1990年   9699篇
  1989年   9383篇
  1988年   9042篇
  1987年   8338篇
  1986年   8070篇
  1985年   9036篇
  1984年   8304篇
  1983年   8037篇
  1982年   7290篇
  1981年   7443篇
  1980年   7196篇
  1979年   7415篇
  1978年   7392篇
  1977年   8048篇
  1976年   9723篇
  1975年   6671篇
  1974年   6582篇
  1973年   6650篇
  1972年   5825篇
  1971年   5404篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
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   
82.
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   
83.
84.
Implementing a neural network on a digital or mixed analog and digital chip yields the quantization of the synaptic weights dynamics. This paper addresses this topic in the case of Kohonen's self-organizing maps. We first study qualitatively how the quantization affects the convergence and the properties, and deduce from this analysis the way to choose the parameters of the network (adaptation gain and neighborhood). We show that a spatially decreasing neighborhood function is far more preferable than the usually rectangular neighborhood function, because of the weight quantization. Based on these results, an analog nonlinear network, integrated in a standard CMOS technology, and implementing this spatially decreasing neighborhood function is then presented. It can be used in a mixed analog and digital circuit implementation.  相似文献   
85.
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   
86.
Genetic evolution of the topology and weight distribution of neuralnetworks   总被引:52,自引:0,他引:52  
This paper proposes a system based on a parallel genetic algorithm with enhanced encoding and operational abilities. The system, used to evolve feedforward artificial neural networks, has been applied to two widely different problem areas: Boolean function learning and robot control. It is shown that the good results obtained in both cases are due to two factors: first, the enhanced exploration abilities provided by the search-space reducing evolution of both coding granularity and network topology, and, second, the enhanced exploitational abilities due to a recently proposed cooperative local optimizing genetic operator.  相似文献   
87.
88.
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 95–112, March–April, 1994.  相似文献   
89.
90.
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