全文获取类型
收费全文 | 880610篇 |
免费 | 12681篇 |
国内免费 | 2569篇 |
专业分类
电工技术 | 16083篇 |
综合类 | 805篇 |
化学工业 | 132748篇 |
金属工艺 | 33856篇 |
机械仪表 | 25735篇 |
建筑科学 | 21987篇 |
矿业工程 | 4253篇 |
能源动力 | 23930篇 |
轻工业 | 76699篇 |
水利工程 | 8764篇 |
石油天然气 | 15537篇 |
武器工业 | 53篇 |
无线电 | 101945篇 |
一般工业技术 | 171613篇 |
冶金工业 | 170060篇 |
原子能技术 | 18008篇 |
自动化技术 | 73784篇 |
出版年
2021年 | 7602篇 |
2020年 | 5708篇 |
2019年 | 7030篇 |
2018年 | 12088篇 |
2017年 | 11886篇 |
2016年 | 12650篇 |
2015年 | 8663篇 |
2014年 | 14377篇 |
2013年 | 40268篇 |
2012年 | 22687篇 |
2011年 | 31392篇 |
2010年 | 25169篇 |
2009年 | 28322篇 |
2008年 | 29091篇 |
2007年 | 28554篇 |
2006年 | 25201篇 |
2005年 | 22864篇 |
2004年 | 21913篇 |
2003年 | 21662篇 |
2002年 | 20820篇 |
2001年 | 21049篇 |
2000年 | 19633篇 |
1999年 | 20648篇 |
1998年 | 52320篇 |
1997年 | 37209篇 |
1996年 | 28706篇 |
1995年 | 21617篇 |
1994年 | 19028篇 |
1993年 | 18764篇 |
1992年 | 13663篇 |
1991年 | 13063篇 |
1990年 | 12730篇 |
1989年 | 12413篇 |
1988年 | 11817篇 |
1987年 | 10372篇 |
1986年 | 10247篇 |
1985年 | 11500篇 |
1984年 | 10742篇 |
1983年 | 9867篇 |
1982年 | 9206篇 |
1981年 | 9326篇 |
1980年 | 8940篇 |
1979年 | 8609篇 |
1978年 | 8378篇 |
1977年 | 10061篇 |
1976年 | 13356篇 |
1975年 | 7347篇 |
1974年 | 6953篇 |
1973年 | 6968篇 |
1972年 | 5911篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
921.
In this practical case study the method of self-organizing map (SOM) neural net is applied to analyze a CMOS process problem, where the device under study is a heartbeat rate monitor integrated circuit. The wafer yield is analyzed against the process control monitoring (PCM) parameter measurement values. The SOM efficiently reduces the parameter space dimensions and helps in visualizing the different parameter relations. This makes it possible to identify the most probable PCM parameters affecting the yield. Those were found out to be NMOS transistor drain current and aluminium sheet resistance. 相似文献
922.
923.
I. I. Abramov I. A. Goncharenko S. A. Ignatenko A. V. Korolev E. G. Novik A. I. Rogachev 《Russian Microelectronics》2003,32(2):97-104
The concept and structure of the NANODEV simulation software are described. NANODEV deals with nanoelectronic devices that exploit single-electron tunneling, resonant tunneling, or quantum interference. It can use both simplified and sophisticated models and enables one to evaluate a wide variety of devices and configurations. The capabilities of NANODEV are illustrated by examples. 相似文献
924.
It is shown that the dominant factor controlling reflectarray bandwidth is the bandwidth of the radiating element, and that the effect of non-constant path delays over the surface of the flat reflector has little significance unless the aperture is electrically very large and the f/D ratio is small. An example of a polarisation-twist reflectarray using aperture coupled elements with time delay lines is used to demonstrate this conclusion. 相似文献
925.
Rossato Janine I.; Bonini Juliana S.; Coitinho Adriana S.; Vianna Monica R. M.; Medina Jorge H.; Cammarota Martín; Izquierdo Iván 《Canadian Metallurgical Quarterly》2004,118(3):563
The gamma aminobutyric acid-A (GABAA) agonist, muscimol, the glutamate N-methyl-D-aspartate (NMDA) receptor antagonist, D-2-amino-5-phosphonopentanoic acid (AP5), and the inhibitor of the extracellularly regulated kinases (ERKs), UO 126, cause retrograde amnesia when administered to the hippocampus. In the present study, the authors found that they all cause retrograde amnesia for 1-trial inhibitory avoidance, not only when infused into the dorsal CA1 region of the hippocampus, but also when infused into the basolateral amygdala or the entorhinal, parietal, and posterior cingulate cortices. The posttraining time course of the effect of each drug was, however, quite different across brain structures. Thus, in all of them, NMDA receptors and the ERK pathway are indispensable for memory consolidation, and GABAA receptor activation inhibits memory consolidation: but in each case, their influence is interwoven differently. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
926.
Low supply voltage high-performance CMOS current mirror with low input and output voltage requirements 总被引:1,自引:0,他引:1
Ramirez-Angulo J. Carvajal R.G. Torralba A. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2004,51(3):124-129
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
927.
给出了覆盖层厚度对巷道周围应力分布的影响及巷道间相互作用的计算机仿真,用三维有限元法分析了在不同覆盖层厚度下巷道周围的应力分布和两个巷道之间不同距离下的相互作用。数值模拟表明了巷道周围应力分布和应力集中系数随覆盖层厚度增加的变化规律,找到了两巷道之间的距离的临界值,当两巷道间距离大于该临界值时,它们之间的相互作用消失。 相似文献
928.
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
929.
Demiguel S. Giraudet L. Joulaud L. Decobert J. Blache F. Coupe V. Jorge F. Pagnod-Rossiaux P. Boucherez E. Achouche M. Devaux F. 《Lightwave Technology, Journal of》2002,20(12):2004-2014
The design, fabrication, and performance of double-stage taper photodiodes (DSTPs) are reported. The objective of this work is to develop devices compatible with 40-Gb/s applications. Such devices require high efficiency, ultrawide band, high optical power handling capability, and compatibility with low-cost module fabrication. The integration of mode size converters improves both the coupling efficiency and the responsivity with a large fiber mode diameter. Responsivity of 0.6 A/W and 0.45 A/W are achieved with a 6-/spl mu/m fiber mode diameter and cleaved fiber, respectively, providing relaxed alignment tolerances (/spl plusmn/1.6 /spl mu/m and /spl plusmn/2 /spl mu/m, respectively), compatible with cost-effective packaging techniques. DSTPs also offer a wide bandwidth greater than 40 GHz and transverse-electric/transverse-magnetic polarization dependence lower than 0.2 dB. Furthermore, a DSTP saturation current as high as 11 mA results in optical power handling greater than +10 dBm and a high output voltage of 0.8 V. These capabilities allow the photodiode to drive the decision circuit without the need of a broad-band electrical amplifier. The DSTP devices presented here demonstrate higher responsivities with large fiber mode diameter and better optical power handling capabilities and are compared with classical side-illuminated photodiodes. 相似文献
930.
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