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   301865篇
  免费   4175篇
  国内免费   829篇
电工技术   5113篇
综合类   173篇
化学工业   48335篇
金属工艺   12141篇
机械仪表   8879篇
建筑科学   7288篇
矿业工程   1872篇
能源动力   7010篇
轻工业   28652篇
水利工程   3341篇
石油天然气   7146篇
武器工业   18篇
无线电   32097篇
一般工业技术   59168篇
冶金工业   54531篇
原子能技术   7584篇
自动化技术   23521篇
  2021年   2479篇
  2019年   2332篇
  2018年   4273篇
  2017年   4211篇
  2016年   4503篇
  2015年   2925篇
  2014年   4840篇
  2013年   13187篇
  2012年   7744篇
  2011年   9999篇
  2010年   8213篇
  2009年   9284篇
  2008年   9547篇
  2007年   9400篇
  2006年   8197篇
  2005年   7613篇
  2004年   7105篇
  2003年   6839篇
  2002年   6877篇
  2001年   6669篇
  2000年   6330篇
  1999年   6435篇
  1998年   15792篇
  1997年   11677篇
  1996年   8979篇
  1995年   6741篇
  1994年   6099篇
  1993年   5990篇
  1992年   4537篇
  1991年   4508篇
  1990年   4346篇
  1989年   4357篇
  1988年   4314篇
  1987年   3648篇
  1986年   3644篇
  1985年   4218篇
  1984年   4005篇
  1983年   3646篇
  1982年   3467篇
  1981年   3610篇
  1980年   3464篇
  1979年   3386篇
  1978年   3467篇
  1977年   3999篇
  1976年   5181篇
  1975年   3167篇
  1974年   3020篇
  1973年   3033篇
  1972年   2656篇
  1971年   2474篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
This paper presents a scheme for the efficient implementation of a low supply voltage continuous-time high-performance CMOS current mirror with low input and output voltage requirements. This circuit combines a shunt input feedback and a regulated cascode output stage to achieve low input resistance and very high output resistance. It can be used as a high-precision current mirror in analog and mixed signal circuits with a power supply close to a transistor's threshold voltage. The proposed current mirror has been simulated and a bandwidth of 40 MHz has been obtained. An experimental chip prototype has been sent for fabrication and has been experimentally verified, obtaining 0.15-V input-output voltage requirements, 100-/spl Omega/ input resistance, and more than 200-M/spl Omega/ (G/spl Omega/ ideally) output resistance with a 1.2-V supply in a standard CMOS technology.  相似文献   
172.
Managing sewerage systems is a highly complex task due to the dynamic nature of the facilities. Their performance strongly depends on the know-how applied by the operators. In order to define optimal operational settings, two decision support tools based on mathematical models have been developed. Moreover, easy-to-use interfaces have been created as well, aiding operators who presumably do not have the necessary skills to use modelling software. The two developed programs simulate the behaviour of both wastewater treatment plants (WWTP) and sewer network systems, respectively. They have essentially the same structure, including raw data management and statistical analysis, a simulation layer using the application programming interface of the applied software and a layer responsible for the representation of the obtained results. Four user modes are provided in the two software including the simulation of historical data using the applied and novel operational settings, as well as modes concerning prediction of possible operation periods and updates. Concerning the WWTP software, it was successfully installed in Nantes (France) in June 2004. Moreover, the one managing sewer networks has been deployed in Saint-Malo (France) in January 2005. This paper presents the structure of the developed software and the first results obtained during the commissioning phase.  相似文献   
173.
Brambilla  G. 《Electronics letters》2002,38(17):954-956
The use of gratings written in tin-doped silica fibres as a thermometer for high-temperature applications is described. Measurements up to ~800°C show a significant advantage over conventional fibre gratings. A considerable blue-shift has been observed at high temperatures. If corrections for blue-shift are taken into account, the errors are smaller than ~2°C  相似文献   
174.
Exact pairwise error probability of space-time codes   总被引:9,自引:0,他引:9  
We describe a simple technique for the numerical calculation, within any desired degree of accuracy, of the pairwise error probability (PEP) of space-time codes over fading channels. This method applies also to the calculation of E[Q(√ξ)] for any nonnegative random variable ξ whose moment-generating function Φξ(s)=E[exp(-sξ)] is known. Its application to the multiple antenna independent Rayleigh-fading channel and to the Rayleigh block fading channel is discussed, and illustrated by two simple examples  相似文献   
175.
176.
177.
A method is given for calculating the monitoring reliability parameters (MRP) for an engineering system with allowance for the drift in the measurement error of the means of measurement (MM). The approach is based on introducing a biased MM error distribution into the traditional formulas for the conditional probabilities of spurious and unobserved failure. The bias at the center of the distribution is determined by the systematic error at the given instant. An example is given to illustrate the performance in MRP calculation.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 12–13, January, 1994.  相似文献   
178.
179.
This paper presents a high-speed, small-area circuit specifically designed to identify the levels in the read out operation of a flash multilevel memory. The circuit is based on the analog computation of the Euclidean distance between the current read out from a memory cell and the reference currents that represent the different logic levels. An experimental version of the circuit has been integrated in a standard double-metal 0.7-μm CMOS process with a die area of only 140×100 μm2. Operating under a 5-V power supply, this circuit identifies the read-out current of a memory cell, and associates it with the appropriate logic level in 9 ns  相似文献   
180.
A modification to the `shape-invariant' sinusoidal speech model is proposed, whereby the phases of the component sinewaves used for the excitation are made to add coherently at each glottal closure. Applied to pitch and time-scale modification, higher quality synthetic speech is produced when large changes are required  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