全文获取类型
收费全文 | 270517篇 |
免费 | 2366篇 |
国内免费 | 616篇 |
专业分类
电工技术 | 4911篇 |
综合类 | 225篇 |
化学工业 | 39825篇 |
金属工艺 | 16263篇 |
机械仪表 | 11520篇 |
建筑科学 | 5149篇 |
矿业工程 | 2767篇 |
能源动力 | 5207篇 |
轻工业 | 14021篇 |
水利工程 | 3840篇 |
石油天然气 | 8673篇 |
武器工业 | 22篇 |
无线电 | 27473篇 |
一般工业技术 | 61942篇 |
冶金工业 | 39306篇 |
原子能技术 | 7445篇 |
自动化技术 | 24910篇 |
出版年
2021年 | 2056篇 |
2019年 | 2008篇 |
2018年 | 10925篇 |
2017年 | 11414篇 |
2016年 | 8228篇 |
2015年 | 2686篇 |
2014年 | 3870篇 |
2013年 | 8801篇 |
2012年 | 7939篇 |
2011年 | 14444篇 |
2010年 | 12850篇 |
2009年 | 12332篇 |
2008年 | 12418篇 |
2007年 | 14061篇 |
2006年 | 5639篇 |
2005年 | 8141篇 |
2004年 | 6398篇 |
2003年 | 6064篇 |
2002年 | 4975篇 |
2001年 | 4540篇 |
2000年 | 4319篇 |
1999年 | 4216篇 |
1998年 | 10209篇 |
1997年 | 7197篇 |
1996年 | 5519篇 |
1995年 | 4147篇 |
1994年 | 3631篇 |
1993年 | 3872篇 |
1992年 | 3004篇 |
1991年 | 3018篇 |
1990年 | 2896篇 |
1989年 | 2860篇 |
1988年 | 2878篇 |
1987年 | 2510篇 |
1986年 | 2569篇 |
1985年 | 2859篇 |
1984年 | 2692篇 |
1983年 | 2557篇 |
1982年 | 2306篇 |
1981年 | 2273篇 |
1980年 | 2349篇 |
1979年 | 2362篇 |
1978年 | 2387篇 |
1977年 | 2498篇 |
1976年 | 2891篇 |
1975年 | 2193篇 |
1974年 | 2071篇 |
1973年 | 2170篇 |
1972年 | 1944篇 |
1971年 | 1756篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
An asymmetric line-axis compound parabolic concentrating single basin solar still of concentration 1.15, exit aperture 0.24 metres and length 0.48 metres, 30° inclination and 60° half acceptance angle has been designed fabricated and tested. 相似文献
982.
983.
A. N. Atanov 《Measurement Techniques》1994,37(11):1320-1321
Translated from Izmeritel'naya Tekhnika, No. 11, pp. 66–67, November, 1994. 相似文献
984.
X-ray phase, differential thermal, and metallographic analyses are used to study the reaction of phosphorus with Fe, Co, Ni, and Mn on heating in an inert atmosphere. It is found that low-temperature endo- and exothermic effects are related to formation of Fe3P, Co2P, Ni3P, and Mn3P. The effect of eutectic contact melting on the metal-phosphide interface is observed in all specimens. 相似文献
985.
V. I. Belousov G. G. Denisov N. Yu. Peskov 《Journal of Infrared, Millimeter and Terahertz Waves》1991,12(9):1035-1043
The article presents results of theoretical and experimental investigation of quasioptical multiplexer based on reflecting diffraction grating. Diffraction losses caused by reflection into mirror harmonic, and by angle divergence of wave beams are calculated. In an experimental multiplexer, wave beams with the frequencies 70 GHz and 79 GHz were mixed with power losses less than 1%. 相似文献
986.
An adaptive morphological filter for image processing 总被引:6,自引:0,他引:6
Novel types of opening operator (NOP) and closing operator (NCP) are proposed. An adaptive morphological filter is then constructed on the basis of the NOP and NCP. The filter can remove any details consisting of fewer pixels than a given number N, while preserving the other details. Efficient algorithms are also developed for the implementation of the NOP and NCP. 相似文献
987.
Many cognitive tasks that are easy for humans to perform are proving difficult to emulate in computer systems. Combining the disciplines of psychology and engineering may offer a solution to some of these problems. A connectionist or neural network model of face recognition by humans which incorporates aspects of a model proposed by cognitive psychologists is presented. A comparative set of experiments has been performed using this simulation and human subjects for familiar face recognition. By employing the same stimuli for both humans and the computer model, it is possible to advance not only our understanding of human cognition but also to develop improved automated systems for face recognition 相似文献
988.
For past I see ibid., vol.4, no.4, p.405 (1995). The use of the image model of Part I is investigated in the context of image compression. The model decomposes the image into a primary component that contains the strong edge information, a smooth component that represents the background slow-intensity variations, and a texture component that contains the textures. The primary component, which is known to be perceptually important, is encoded separately by encoding the intensity and geometric information of the strong edge brim contours. Two alternatives for coding the smooth and texture components are studied: entropy-coded adaptive DCT and entropy-coded subband coding. It is shown via simulations that the proposed schemes, which can be thought of as a hybrid of waveform coding and feature-based coding techniques, result in both subjective and objective performance improvements over several other image coding schemes and, in particular, over the JPEG continuous-tone image compression standard. These improvements are especially noticeable at low bit rates. Furthermore, it is shown that a perceptual tuning based on the contrast-sensitivity of the human visual system can be used in the DCT-based scheme, which in conjunction with the three-component model, leads to additional subjective performance improvements. 相似文献
989.
990.