全文获取类型
收费全文 | 289525篇 |
免费 | 21494篇 |
国内免费 | 11102篇 |
专业分类
电工技术 | 15399篇 |
技术理论 | 31篇 |
综合类 | 17440篇 |
化学工业 | 50195篇 |
金属工艺 | 16879篇 |
机械仪表 | 18430篇 |
建筑科学 | 22866篇 |
矿业工程 | 9525篇 |
能源动力 | 7954篇 |
轻工业 | 16676篇 |
水利工程 | 4778篇 |
石油天然气 | 20262篇 |
武器工业 | 2234篇 |
无线电 | 31465篇 |
一般工业技术 | 34416篇 |
冶金工业 | 15269篇 |
原子能技术 | 2863篇 |
自动化技术 | 35439篇 |
出版年
2024年 | 1218篇 |
2023年 | 4678篇 |
2022年 | 7920篇 |
2021年 | 11470篇 |
2020年 | 8533篇 |
2019年 | 7274篇 |
2018年 | 8170篇 |
2017年 | 9222篇 |
2016年 | 8029篇 |
2015年 | 11168篇 |
2014年 | 13775篇 |
2013年 | 16447篇 |
2012年 | 17757篇 |
2011年 | 19406篇 |
2010年 | 16753篇 |
2009年 | 15907篇 |
2008年 | 15446篇 |
2007年 | 15085篇 |
2006年 | 15975篇 |
2005年 | 14148篇 |
2004年 | 9045篇 |
2003年 | 7904篇 |
2002年 | 7307篇 |
2001年 | 6483篇 |
2000年 | 7097篇 |
1999年 | 8498篇 |
1998年 | 6845篇 |
1997年 | 5821篇 |
1996年 | 5451篇 |
1995年 | 4507篇 |
1994年 | 3757篇 |
1993年 | 2628篇 |
1992年 | 2137篇 |
1991年 | 1601篇 |
1990年 | 1173篇 |
1989年 | 933篇 |
1988年 | 759篇 |
1987年 | 523篇 |
1986年 | 389篇 |
1985年 | 265篇 |
1984年 | 183篇 |
1983年 | 120篇 |
1982年 | 130篇 |
1981年 | 86篇 |
1980年 | 70篇 |
1979年 | 24篇 |
1978年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
Microstructure evolution of AZ31 magnesium alloy during equal channel angular extrusion 总被引:3,自引:0,他引:3
Li Yuanyuan Zhang Datong Chen Weiping Liu Ying Guo Guowen 《Journal of Materials Science》2004,39(11):3759-3761
84.
85.
Polyurethane elastomer composites were developed using milled fiberglass and their mechanical properties were studied. In particular, the organically chemical treatment of the milled fiberglass was investigated in detail. It was demonstrated that both strength and toughness of the resulting elastomer composites were improved considerably with the addition content of fiberglass. Furthermore, it was indicated that the optimal properties can be achieved by the proper addition of milled fiberglass that was chemically treated using coupling agent. 相似文献
86.
BaMgAl10O17∶Eu2 (BAM) was prepared in the microemulsion system and its phase behavior was studied. There exists a small region in the reverse microemulsion system where the dispersed particles are of spherical form. In this way, BAM blue phosphor with good dispersion can be synthesized. The microemulsion phase diagrams of the pseudo-ternary system (Triton X-100/cosurfactant-oil-BAM brine) were first established intuitively by the dilution method. The microstructure of microemulsions was determined through eyeballing, conductance technique, and polar optical microscopy. Its phase behavior is affected by various factors, such as temperature (room temperature, 30, 40 ℃), oil, surfactants, and cosurfactants in microemulsions. According to the phase diagrams, the microemulsion system of Triton X-100/1-hexanol-hexane-BAM brine was chosen to prepare the precursor. The BAM phosphor can be obtained via sintering the precursor at a comparatively low temperature. The phosphors were characterized by XRD and vacuum ultraviolet (VUV) spectra. 相似文献
87.
Zhang Z.G. Chan S.C. Tsui K.M. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2008,55(6):576-580
This paper proposes a new Kalman-filter-based recursive frequency estimator for discrete-time multicomponent sinusoidal signals whose frequencies may be time-varying. The frequency estimator is based on the linear prediction approach and it employs the Kalman filter to track the linear prediction coefficients (LPCs) recursively. Frequencies of the sinusoids can then be computed using the estimated LPCs. Due to the coloredness of the linear prediction error, an iterative algorithm is employed to estimate the covariance matrix of the prediction error and the LPCs alternately in the Kalman filter in order to improve the tracking performance. Simulation results show that the proposed Kalman-filter-based iterative frequency estimator can achieve better tracking results than the conventional recursive least-squares-based estimators. 相似文献
88.
89.
Oxide films were deposited on different substrates by laser molecular beam epitaxy. Reflection high-energy electron diffraction was performed to in situ investigate the change of growth mode and the lattice relaxation during the growth. An asymmetrical phenomenon was found in the two kinds of strain states, compressive stress and tensile stress of heterostructures with different lattice mismatch. In the case of BaTiO3/SrTiO3 (2.2%), 2D layer-by-layer growth mode without lattice relaxation can be maintained for a longer period for BTO films on STO with compressive stress, comparing to STO films on BTO with tensile stress. When MgO films were deposited on SrTiO3 with a large mismatch of 7.8%, compressive stress leads to rapid lattice relaxation with a very thin wet layer, and 3D strained island were observed. As a comparison, SrTiO3 films on MgO with tensile stress were configured. No RHEED patterns can be observed duo to a large tensile stress. 相似文献
90.
2008年29届奥运会在北京举行,使得有关奥运的话题成为热门中的热门,与运动有关或无关的众多品牌、厂商对北京奥运年均寄予厚望,为赢取更大的收获和提升品牌知名度作最大的努力。其实早在几年前,国内外运动鞋品牌企业就已经大张旗鼓,在产品研发与广告宣传等多方面投入重金,为在这次北京奥运年带来的难得契机中处于市场制高点或明或隐地博杀着。 相似文献