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 843 毫秒
941.
The theory of characteristic modes for aperture problems is used in this paper to solve the equivalent magnetic current and aperture fields due to a conducting cylinder with multiple slots. It is assumed that these slots are illuminated by either a transverse electric (TE) or a transverse magnetic (TM) plane wave and the media inside and outside the cylinder exhibit different electromagnetic properties. The formulation is given for the general case and numerical results for a limited number of slots are presented 相似文献
942.
Marti J. Mossi J.M. Ferrando M. 《Electromagnetic Compatibility, IEEE Transactions on》1994,36(3):242-244
A measurement campaign using live TV broadcast satellite signals and receiving commercial equipment has been carried out to study the required cross-polar protection ratio at the receiving antenna in satellite transmission planning. This experiment provides useful and realistic conclusions for the optimum spectrum allocation of TV channels in broadcasting satellite systems, as for example, the frequency offset required between cross-polar channels depending on the cross-polar rejection at the receiving antenna, for a certain grade of video signal impairment due to the cross-polar channel interference effects, and taken also into account the noise contribution on the signal 相似文献
943.
Mine K. Kubota N. Morimoto F. Sanada M. Zhang Qi 《Electromagnetic Compatibility, IEEE Transactions on》1994,36(3):253-255
This short paper discusses the method of effectively canceling equal status normal mode noise not only on a sensor line but also on a transmission line of an optical instrument using a sensor with a sensordummy resistance 相似文献
944.
Crosstalk between microstrip transmission lines 总被引:1,自引:0,他引:1
Hill D.A. Cavcey K.H. Johnk R.T. 《Electromagnetic Compatibility, IEEE Transactions on》1994,36(4):314-321
Methods for prediction of crosstalk between microstrip transmission lines are reviewed and simplified for the weak-coupling case. Classical coupled transmission line theory is used for uniform lines, and potential and induced EMF methods are used for crosstalk between nonuniform lines. It is shown that the potential method is equivalent to classical coupled transmission line theory for the case of uniform lines. An experiment was performed for uniform coupled microstrip lines for frequencies from 50 MHz to 5 GHz, and good agreement between theory and measurement was obtained for both near- and far-end crosstalk 相似文献
945.
946.
947.
948.
Results of calorimetric investigations performed on two groups of glasses, viz. As-Te-Se and Ge-As-Se, are described. The
glass transition temperatureT
g and specific heat at constant pressureC
p
of these two families of glasses have been determined using a differential scanning calorimeter. The composition dependence
of glass transition temperature and variation of heat capacity during transition are discussed. 相似文献
949.
An instrument is proposed for continuously tracking the Sun and measuring its height by the use of a laser gyrometer as measuring
converter. The accuracy in photoelectric sighting on the Sun is improved by greatly reducing the light fluxes to be compared
by screening out the central part of the Sun's image in the focal plane.
Translated from Izmeritel'naya Tekhnika, No. 3, pp. 7–9, March, 1994. 相似文献
950.
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