全文获取类型
收费全文 | 4494篇 |
免费 | 358篇 |
国内免费 | 233篇 |
专业分类
电工技术 | 42篇 |
综合类 | 218篇 |
化学工业 | 2363篇 |
金属工艺 | 545篇 |
机械仪表 | 83篇 |
建筑科学 | 50篇 |
矿业工程 | 130篇 |
能源动力 | 92篇 |
轻工业 | 27篇 |
水利工程 | 1篇 |
石油天然气 | 229篇 |
武器工业 | 22篇 |
无线电 | 111篇 |
一般工业技术 | 658篇 |
冶金工业 | 455篇 |
原子能技术 | 24篇 |
自动化技术 | 35篇 |
出版年
2024年 | 10篇 |
2023年 | 68篇 |
2022年 | 108篇 |
2021年 | 102篇 |
2020年 | 135篇 |
2019年 | 102篇 |
2018年 | 115篇 |
2017年 | 120篇 |
2016年 | 111篇 |
2015年 | 99篇 |
2014年 | 168篇 |
2013年 | 213篇 |
2012年 | 216篇 |
2011年 | 282篇 |
2010年 | 195篇 |
2009年 | 217篇 |
2008年 | 199篇 |
2007年 | 281篇 |
2006年 | 264篇 |
2005年 | 217篇 |
2004年 | 200篇 |
2003年 | 221篇 |
2002年 | 203篇 |
2001年 | 192篇 |
2000年 | 181篇 |
1999年 | 128篇 |
1998年 | 88篇 |
1997年 | 65篇 |
1996年 | 43篇 |
1995年 | 55篇 |
1994年 | 65篇 |
1993年 | 53篇 |
1992年 | 79篇 |
1991年 | 90篇 |
1990年 | 92篇 |
1989年 | 73篇 |
1988年 | 10篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1951年 | 2篇 |
排序方式: 共有5085条查询结果,搜索用时 4 毫秒
61.
62.
David B. Marshall Joseph J. Ratto Fred F. Lange 《Journal of the American Ceramic Society》1991,74(12):2979-2987
Laminar composites, containing layers of Ce-ZrO2 and either Al2 O3 or a mixture of Al2 O3 and Ce-ZrO2 , have been fabricated using a colloidal method that allowed formation of layers with thicknesses as small as 10 μm. Strong interactions between these layers and the martensitic transformation zones surrounding cracks and indentations have been observed. In both cases, the transformation zones spread along the region adjacent to the layer, resulting in an increased fracture toughness. The enhanced fracture toughness was observed for cracks growing parallel to the layers as well as for those that were oriented normal to the layers. 相似文献
63.
David A. Woodford Donald R. VanSteele Mohammed J. Hyder 《Journal of the American Ceramic Society》1991,74(12):3142-3144
The development of a tensile testing methodology for ceramics which enables a stress vs strain-rate response to be measured at high temperature is described. The test involves a carefully controled stress relaxation test at constant total strain using an experimental procedure and phenomenological analysis previously developed for metallic materials. It is demonstrated here with preliminary tests on alumina at 1050° and 1150°C. This offers, with further development, the possibility of establishing design stresses associated with low strain-rate behavior for structural applications. The results demonstrate that data covering four decades of strain rate may be generated in tests lasting a few hours. The inelastic strain consists of substantial anelastic recoverable strain in addition to a permanent creep strain. 相似文献
64.
65.
电泳沉积法γ-Al2O3微孔膜的制备与表征 总被引:5,自引:1,他引:5
采用电泳沉积法制备γ-Al2O3微孔膜,考察了干燥及烧成制度对膜形成的影响,并用IR,XRD,SEM,N2吸附-脱附等测试手段对γ-Al2O3微孔膜进行了表征。结果表明:采用电泳沉积法可成功地制备均匀的γ-Al2O3保护膜;实验中采用室温慢速干燥法,制得了完整的凝胶膜,经过焙烧可获得与基片结合良好的γ-Al2O3多孔膜,在焙烧过程中,γ-AlOOH发生如下的晶型转变:γ-AlOOH→345℃γ-Al2O3,并且随着焙烧温度的升高,γ-Al2O3膜的结晶性得到改善。此外,γ-Al2O3膜的断面结构较疏松,膜厚度大面均匀:一次成膜厚度达十几μm,γ-Al2O3微孔膜的孔径尺寸为纳米级。 相似文献
66.
研究了锌铝基Al2O3陶瓷层激光重熔区内陶瓷相的转变。采用METCO 4MP等离子喷涂机对基体材料表面喷涂氧化铝(Al2O3的质量分数为99%)陶瓷层。采用上海光学精密机械研究所HJ-4工业用横流CO2激光器进行激光重熔。通过X射线衍射分析和透射电镜对Al2O3陶瓷的微观结构、成分和分布的研究,得到以下结论:在等离子喷涂过程中,喷涂层中陶瓷相发生。α-Al2O3→γ-Al2O3 α-Al2O3的转变。激光重熔后,试样表层的原α-Al2O3陶瓷相、γ-Al2O3陶瓷相均转变为δ-Al2O3陶瓷相,为体心四方结构.熔池区陶瓷相主要分布在表层,次表层和过渡区。 相似文献
67.
介绍了以烧结刚玉和板状刚玉为原料试制再结合刚玉砖的生产工艺。同时,研究了不同原料、氧化铝微粉、外加物及工艺条件对制品性能的影响。 相似文献
68.
A new approach for preparing of microcellular ceramic materials is the reproduction of wood morphologies by biotemplating, where the structural features of the native wood are maintained in the ceramic product. Biomorphic Al2O3-ceramics were manufactured via the sol-gel route by repeated infiltration of low viscous alumina sols into wood preforms and subsequently sintered in air at 1550°C. The microstructure and phase formation during processing were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), density and porosimetry measurements. In contrast to conventional processed, highly-porous Al2O3-ceramics, the microstructure of the biomorphic Al2O3-ceramics is characterized by an uniaxial pore morphology with pore diameters in the micrometer range, depending on the initially used wood template. 相似文献
69.
Earlier studies have shown that sulfur dioxide and metal-support interaction can strongly influence propane oxidation over platinum. In particular, oxidation activity is enhanced when platinum is supported on sulfated -alumina or zirconia compared to -alumina. Therefore, it is of interest to compare the performance of palladium under the same experimental conditions. Four model catalysts were examined: Pt/-alumina, Pt/zirconia, Pd/-alumina and Pd/zirconia. The metal loading was kept at or below 0.05 wt% to emphasize changes in activity attributable to metal-support interaction. Reaction rates were measured with and without sulfur dioxide. Surface sulfation was analyzed by measuring acid strength and evaluating spectra obtained by Fourier-transform infrared spectroscopy. In contrast to platinum, sulfation does not promote propane oxidation on Pd/-alumina, and Pd/zirconia is less active than Pd/-alumina. 相似文献
70.
Eric Jorge Thierry Chartier Phillippe Boch 《Journal of the American Ceramic Society》1990,73(8):2552-2554
Ultrasonication is very effective in dispersing alumina and barium titanate slurries. When optimum conditions are used, very short durations (2 to 3 min) are enough to achieve well-dispersed, stable suspensions. 相似文献