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   541667篇
  免费   7335篇
  国内免费   1572篇
电工技术   9971篇
综合类   587篇
化学工业   80936篇
金属工艺   20628篇
机械仪表   15629篇
建筑科学   13075篇
矿业工程   2317篇
能源动力   14913篇
轻工业   48392篇
水利工程   5374篇
石油天然气   9436篇
武器工业   38篇
无线电   61715篇
一般工业技术   104483篇
冶金工业   107793篇
原子能技术   10821篇
自动化技术   44466篇
  2022年   3219篇
  2021年   5007篇
  2020年   3555篇
  2019年   4657篇
  2018年   7949篇
  2017年   7757篇
  2016年   8094篇
  2015年   5672篇
  2014年   9447篇
  2013年   24623篇
  2012年   14957篇
  2011年   20641篇
  2010年   16147篇
  2009年   18104篇
  2008年   18577篇
  2007年   18249篇
  2006年   15933篇
  2005年   14740篇
  2004年   14012篇
  2003年   13853篇
  2002年   13136篇
  2001年   13307篇
  2000年   12284篇
  1999年   13011篇
  1998年   34221篇
  1997年   23859篇
  1996年   18133篇
  1995年   13530篇
  1994年   11734篇
  1993年   11427篇
  1992年   8173篇
  1991年   7676篇
  1990年   7512篇
  1989年   7260篇
  1988年   6692篇
  1987年   5979篇
  1986年   5838篇
  1985年   6480篇
  1984年   6067篇
  1983年   5338篇
  1982年   5056篇
  1981年   5139篇
  1980年   4864篇
  1979年   4745篇
  1978年   4537篇
  1977年   5571篇
  1976年   7295篇
  1975年   3897篇
  1974年   3635篇
  1973年   3762篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Qin  Y.M. Ciric  I.R. 《Electronics letters》1994,30(24):2028-2029
The Tikhonov regularisation technique is widely used in the solution of inverse scattering problems. One of the difficulties in applying this technique is the proper selection of the associated regularisation parameter. Based on a stochastic model of the reconstruction process, a simple method is presented for selecting this parameter for an efficient implementation of various microwave imaging methods  相似文献   
992.
The effects of several modified atmospheres (100% O2, 100% N2, 100% CO2+ O2 scavenger, and 25% CO2 9% N2 66% O2) and vacuum on the color stability of turkey were studied. Microbiological examinations were performed at days 0, 7, 14 and 21. pH and pigment content measurements were performed at days l and 2, respectively. Color coordinates were determined at intervals of 2, 5, 7, 11, 14 and 21 days storage in the CIELAB system (1976). Meat kept under vacuum and 100% CO2+ O2 scavenger treatment showed the highest a* values color stability (p < 0.05) and the lowest rate of myoglobin oxidation (p < 0.05). The level of microbiological contamination of turkey breast meat stored with 100% CO2+ O2 scavenger was the lowest. Conditioning breast turkey meat with 100% CO2+ O2 scavenger or under vacuum would improve the color stability during storage.  相似文献   
993.
994.
995.
Dichotic listening procedures have been used to assess cerebral lateralization in normal Ss. One particularly useful technique is the use of stimuli that fuse into a single percept. Although this procedure has many advantages over other dichotic listening methods, it is particularly susceptible to stimulus dominance, which acts as noise in a S's response data, thus reducing the power of any statistical test of the ear advantage. It is proposed that the solution to this problem is a log-linear analysis of the response data to yield a λ-type index (λ*) that is a measure of ear dominance independent of stimulus dominance. Details of the analysis are provided, as well as a sample analysis of data collected from 104 right-handed and 30 left-handed Ss. Comparisons are drawn between the log-linear analysis and other methods that have been proposed to control for stimulus dominance in this single-response dichotic fusion procedure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
996.
An electric motor double-buffered speed measurement method for PC/AT computer application is based on 14.31818 MHz reference clock. The extremely wide frequency range of 4·109 (1.67 mHz to 7 MHz) is independent of sampling time, which can be chosen from 100 μs to 4.6 ms. Appropriate software provides real-time graphics presentation of measured speed versus time and storage for further analysis. The enclosed test diagrams cover DC motor speed reversal and an induction motor acceleration  相似文献   
997.
In this paper, the authors present a hardware implementation of a fully digital multilayer perceptron artificial neural network using Xilinx Field Programmable Gate Arrays (FPGAs). Each node is implemented with two XC3042 FPGAs and a 1 K×8 EPROM. Training is done offline on a PC. The authors have tested successfully the performance of the network  相似文献   
998.
This paper presents the state of the art in the control of robotic manipulators in constrained motion tasks. Contact control concepts are classified using different criteria, and their main characteristics are analyzed. For each of the presented contact control concepts, the essential characteristics are stated. The paper covers some early ideas and their later improvements, as well as trends in this field. The advantages and drawbacks of the various control schemes are outlined, and they are compared from the standpoint of their implementation issues. In the paper, all characteristic results in the stability analysis of robotic manipulators in the constrained motion tasks are briefly reported. A new approach to the correct solution of contact tasks control is mentioned as well  相似文献   
999.
A boost type converter is described that is suitable for low-voltage DC-supply of fluorescent lamps. It has inherent lamp current limitation (ballast action) and provides the high voltage pulses and electrode heating that are required for igniting the lamp. The proposed circuit is applicable in automotive, emergency, and portable light sources.<>  相似文献   
1000.
In this paper, we present a technique for using an additional parallel neural network to provide adaptive enhancements to a basic fixed neural network-based nonlinear control system. This proposed parallel adaptive neural network control system is applicable to nonlinear dynamical systems of the type commonly encountered in many practical position control servomechanisms. Properties of the controller are discussed, and it is shown that if Gaussian radial basis function networks are used for the additional parallel neural network, uniformly stable adaptation is assured and the approximation error converges to zero asymptotically. In the paper, the effectiveness of the proposed parallel adaptive neural network control system is demonstrated in real-time implementation experiments for position control in a servomechanism with asymmetrical loading and changes in the load  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