全文获取类型
收费全文 | 513312篇 |
免费 | 5672篇 |
国内免费 | 1988篇 |
专业分类
电工技术 | 8899篇 |
综合类 | 671篇 |
化学工业 | 77920篇 |
金属工艺 | 20773篇 |
机械仪表 | 15329篇 |
建筑科学 | 12245篇 |
矿业工程 | 3099篇 |
能源动力 | 12531篇 |
轻工业 | 43824篇 |
水利工程 | 5661篇 |
石油天然气 | 11453篇 |
武器工业 | 56篇 |
无线电 | 58492篇 |
一般工业技术 | 102321篇 |
冶金工业 | 93295篇 |
原子能技术 | 12998篇 |
自动化技术 | 41405篇 |
出版年
2021年 | 3878篇 |
2019年 | 3665篇 |
2018年 | 6530篇 |
2017年 | 6557篇 |
2016年 | 7047篇 |
2015年 | 4550篇 |
2014年 | 7720篇 |
2013年 | 21930篇 |
2012年 | 12539篇 |
2011年 | 17180篇 |
2010年 | 13740篇 |
2009年 | 15797篇 |
2008年 | 16286篇 |
2007年 | 16152篇 |
2006年 | 14156篇 |
2005年 | 13222篇 |
2004年 | 12739篇 |
2003年 | 12261篇 |
2002年 | 12182篇 |
2001年 | 12049篇 |
2000年 | 11450篇 |
1999年 | 11773篇 |
1998年 | 28131篇 |
1997年 | 20510篇 |
1996年 | 15889篇 |
1995年 | 12147篇 |
1994年 | 10819篇 |
1993年 | 10714篇 |
1992年 | 8040篇 |
1991年 | 7908篇 |
1990年 | 7610篇 |
1989年 | 7568篇 |
1988年 | 7257篇 |
1987年 | 6375篇 |
1986年 | 6345篇 |
1985年 | 7212篇 |
1984年 | 6759篇 |
1983年 | 6231篇 |
1982年 | 5856篇 |
1981年 | 5970篇 |
1980年 | 5849篇 |
1979年 | 5636篇 |
1978年 | 5668篇 |
1977年 | 6417篇 |
1976年 | 8401篇 |
1975年 | 5076篇 |
1974年 | 4868篇 |
1973年 | 4874篇 |
1972年 | 4201篇 |
1971年 | 3829篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Consideration was given to the decision making procedures based on the fuzzy messages of experts whose preferences on the set of collective decisions can also be fuzzy. 相似文献
102.
I. N. Polandov V. K. Novik O. K. Gulish B. P. Bogomolov V. B. Morozov 《Measurement Techniques》1989,32(9):888-890
Translated from Izmeritel'naya Tekhnika, No. 9, pp. 34–35, September, 1989. 相似文献
103.
M. Polák M. Majoro F. Hanic J. Pitel M. Kedrová P. Kottman J. Talapa L. Vencel 《Journal of Superconductivity》1989,2(2):219-233
A method for contactless measurement of the shielding critical current density and its dependence on the external magnetic field is described and analyzed. The obtained values are compared with those measured resistively on two different samples. It is shown that the shielding critical current densityJ
cs
and the intergranular transport current densityJ
cr
are identical if the measurement conditions are similar. A degradation ofJ
cs
measured in the external field with AC ripple has been observed. 相似文献
104.
105.
A new method is described for transferring phase contrast in electron microscopy without artefacts due to oscillations of the phase contrast transfer function (PCTF). This is carried out by in situ image synthesis of two or three exposures transferred with complementary PCTF. The essence of the technique is to use optimized transfer attenuation functions to cut off the negative parts of PCTF. 相似文献
106.
P.W. Hawkes 《Ultramicroscopy》1985,17(2):151-156
Modifications of solid water and their transitions are described as they relate to cryo electron microscopy. In particular, the various amorphous states (amorphous polymorphs) as they exist below 100 K are extensively investigated. The “high-density” midification exhibits a lower viscosity than the “low-density” form. Differences are also observed in the mechanism of void formation due to electron irradiation: in the high-density form, voids are formed — not, however, in the low-density form. Together with the reaction to radiation damage, the physical properties of amorphous solid water are discussed with respect to embedding of organic specimens. Finally, the conditions and pitfalls associated with preparation of thin and entirely vitrified ice layers by shock-freezing are described. 相似文献
107.
Fuzzy logic was first suggested as the mechanism by which humans drive cars. This paper addresses the use of fuzzy logic and algorithms towards the intelligent autonomous motion control of land vehicles. To cope with vehicle complexities, internal parametric changes, and with unpredictable environmental effects, the controllers that are presented, whilst heuristic in nature, are self-organizing or self-learning in that they generate automatically by observation an experiential rule base that models the vehicle, and via an appropriate performance index an optimal control rule base that is robust to large parametric changes. The methodology presented is applicable to any complex process which is too difficult to model or control using conventional methods, or which has relied on the experience of a human operator. An overview of fuzzy logic and static fuzzy logic control (akin to expert systems) is provided, together with illustrative examples. 相似文献
108.
Translated from Atomnaya Énergiya, Vol. 67, No. 2, pp. 97–100, August, 1989. 相似文献
109.
Francois P.-L. Monerie M. Vassallo C. Durteste Y. Alard F.R. 《Lightwave Technology, Journal of》1989,7(3):500-513
Depending on the spectal width of the source illuminating an interferometer, measurement procedures can utilize either the whole interferogram, or only the fringe envelope, or only the fringe quick oscillations. With an ultraband spectrum source, a simplified adaptation of the methods of Fourier transform spectroscopy yields the variations of the test-fiber propagation constant over the whole wavelength-interval of the source. Chromatic dispersion can then be computed from a single interferogram. With narrower spectrum sources, only the fringe envelopes are utilized and yield measurements of mode delay, with application to chromatic and polarization mode dispersion. In this case, however, interferograms at several wavelengths are necessary. With even narrower spectrum sources, the fringe quick oscillations provide measurements of phase shifts, related to changes in the mode propagation constant, when outside perturbations are applied to the test fiber. A direct method for measuring the third-order nonlinear susceptibilities is discussed. In this case the outside perturbation is an intense pump laser field 相似文献
110.
The brushless doubly fed induction machine (BDFIM) has been extensively researched for approximately 30 years, but a related machine [the brushless doubly fed reluctance machine (BDFRM)], has not. This was mainly due to the fact that reluctance rotor designs were not capable of generating saliency ratios large enough to make the BDFRM competitive with other machines. However, recent developments in reluctance rotors, spurred on by research into synchronous reluctance machines, has resulted in high saliency ratio rotors that are economic to build. This, together with the promise of higher efficiency and simpler control compared to the BDFIM, means that further investigation of the BDFRM is warranted. A relatively limited amount of work to date has been published on the BDFRM. This paper attempts to fill this void by presenting a theoretical analysis of some of the important control properties of the ideal BDFRM. 相似文献