全文获取类型
收费全文 | 275478篇 |
免费 | 5848篇 |
国内免费 | 1990篇 |
专业分类
电工技术 | 5506篇 |
综合类 | 1807篇 |
化学工业 | 41520篇 |
金属工艺 | 9256篇 |
机械仪表 | 8318篇 |
建筑科学 | 8160篇 |
矿业工程 | 970篇 |
能源动力 | 7801篇 |
轻工业 | 32158篇 |
水利工程 | 2622篇 |
石油天然气 | 2582篇 |
武器工业 | 141篇 |
无线电 | 35481篇 |
一般工业技术 | 48782篇 |
冶金工业 | 47481篇 |
原子能技术 | 3580篇 |
自动化技术 | 27151篇 |
出版年
2022年 | 1875篇 |
2021年 | 2819篇 |
2020年 | 2167篇 |
2019年 | 2329篇 |
2018年 | 3303篇 |
2017年 | 3418篇 |
2016年 | 3620篇 |
2015年 | 3258篇 |
2014年 | 5107篇 |
2013年 | 13691篇 |
2012年 | 8747篇 |
2011年 | 11812篇 |
2010年 | 9270篇 |
2009年 | 10156篇 |
2008年 | 10526篇 |
2007年 | 10469篇 |
2006年 | 9482篇 |
2005年 | 8387篇 |
2004年 | 7812篇 |
2003年 | 7516篇 |
2002年 | 6945篇 |
2001年 | 7270篇 |
2000年 | 6528篇 |
1999年 | 6988篇 |
1998年 | 16591篇 |
1997年 | 11532篇 |
1996年 | 8696篇 |
1995年 | 6627篇 |
1994年 | 5775篇 |
1993年 | 5635篇 |
1992年 | 4050篇 |
1991年 | 3812篇 |
1990年 | 3582篇 |
1989年 | 3395篇 |
1988年 | 3306篇 |
1987年 | 2626篇 |
1986年 | 2507篇 |
1985年 | 3178篇 |
1984年 | 2812篇 |
1983年 | 2572篇 |
1982年 | 2354篇 |
1981年 | 2408篇 |
1980年 | 2217篇 |
1979年 | 2055篇 |
1978年 | 1887篇 |
1977年 | 2184篇 |
1976年 | 2747篇 |
1975年 | 1587篇 |
1974年 | 1492篇 |
1973年 | 1560篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Trapping of net positive charge at low gate stress voltage, and of net negative charge at high gate stress voltage, is observed through changes in the gate-to-drain capacitance of the stressed junction. These observations can be explained in terms of electron trapping, hole trapping, and generation of acceptor-like interface states located in the upper half of the bandgap. Channel shortening is also observed and found to exhibit a logarithmic time dependence 相似文献
993.
994.
995.
This paper presents two independent dynamic models of a nuclear gas turbine power plant. Both the high temperature nuclear reactor (HTR) and its energy conversion system (ECS) based on a direct Brayton cycle have been modelled. One model utilises RELAP5 for the ECS, the other Aspen Custom Modeler (ACM). The reactor model used in both models is a point kinetic model derived from a detailed reactor model. The ECS model is described and compared componentwise, with an emphasis on the turbomachinery. The total plant models are compared with each other by calculating two representative transients: one load rejection transient and one transient with the system at part load. 相似文献
996.
1 诚信对兖矿资本运营的贡献1.1 在兖矿股票发行方面 1988年4月兖矿煤业在纽约、香港打响了上市的第一炮,这次兖州煤业全球发行8.2亿股,发行总收入折合人民币2.58亿元。可是当时的背景是亚洲金融危机爆发所带来的负面影响尚未完全消除,世界各地失信现象屡屡发生。活力28集团股份有限公司股票上市申报时虚增利润1667.7万元,上市后三年虚增利润21124.3万元,1998年公司在配股时公开披露国家股股东荆州市国资局以现金2320万元认购 相似文献
997.
The design of an adaptive nonlinear controller for the control of a fluidized bed reactor is derived by using exact linearization techniques. Reset action and parameter adaptation are used to make more robust the precise compensation of nonlinear terms, which is called for in the linearization technique. A nonlinear antiwindup mechanism is introduced to handle reset windup problem and to provide fast response without large overshoot. Simulation results show that the proposed adaptive controller guarantees good setpoint tracking. The developed estimation algorithm allows accurate estimation of the parameters for which the regressor component is not zero. 相似文献
998.
A highly linear electrooptic modulator has been designed, fabricated, and evaluated. The design of this modulator consists of only a simple modification to the directional coupler. Two-tone testing has demonstrated that, for an optical modulation depth of 30% per channel, the third-order intermodulation distortion is more than 30 dB lower than that of the conventional directional coupler or Mach-Zehnder modulators. This improvement was not observed to be accompanied by any increase in second harmonic distortion. Also included are results of two-tone computer simulations which predict the improvement in linearity of this device for a range of modulation depths.<> 相似文献
999.
1000.
The pattern synthesis techinque described allows the power pattern to be optimized in a very useful sense over the desired operating band of the antenna array. This is an improvement over previous techniques involving constraints on such artificial parameters as source norm and superdirectivity ratio, which do not, in fact, ensure a useful pattern bandwidth. The procedure described provides minimum mean square error over an arbitrary number of discrete frequencies 相似文献