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   767345篇
  免费   8246篇
  国内免费   1569篇
电工技术   13013篇
综合类   2823篇
化学工业   119598篇
金属工艺   34945篇
机械仪表   25413篇
建筑科学   17223篇
矿业工程   6544篇
能源动力   17953篇
轻工业   54977篇
水利工程   10172篇
石油天然气   20353篇
武器工业   48篇
无线电   78814篇
一般工业技术   161199篇
冶金工业   114821篇
原子能技术   19125篇
自动化技术   80139篇
  2021年   6634篇
  2019年   6304篇
  2018年   24666篇
  2017年   23754篇
  2016年   21270篇
  2015年   7885篇
  2014年   12689篇
  2013年   31393篇
  2012年   21845篇
  2011年   33883篇
  2010年   27873篇
  2009年   27809篇
  2008年   29252篇
  2007年   29684篇
  2006年   19521篇
  2005年   18569篇
  2004年   17783篇
  2003年   17503篇
  2002年   16415篇
  2001年   15481篇
  2000年   14981篇
  1999年   14400篇
  1998年   32173篇
  1997年   23569篇
  1996年   18352篇
  1995年   14169篇
  1994年   12973篇
  1993年   12708篇
  1992年   10003篇
  1991年   9845篇
  1990年   9690篇
  1989年   9392篇
  1988年   9041篇
  1987年   8337篇
  1986年   8069篇
  1985年   9027篇
  1984年   8301篇
  1983年   8031篇
  1982年   7293篇
  1981年   7444篇
  1980年   7192篇
  1979年   7409篇
  1978年   7398篇
  1977年   8062篇
  1976年   9734篇
  1975年   6673篇
  1974年   6585篇
  1973年   6656篇
  1972年   5824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.
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   
82.
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   
83.
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   
84.
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   
85.
86.
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   
87.
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   
88.
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   
89.
90.
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 95–112, March–April, 1994.  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