全文获取类型
收费全文 | 40279篇 |
免费 | 3030篇 |
国内免费 | 1750篇 |
专业分类
电工技术 | 713篇 |
技术理论 | 1篇 |
综合类 | 1718篇 |
化学工业 | 11756篇 |
金属工艺 | 9477篇 |
机械仪表 | 2472篇 |
建筑科学 | 1491篇 |
矿业工程 | 699篇 |
能源动力 | 1772篇 |
轻工业 | 1879篇 |
水利工程 | 91篇 |
石油天然气 | 648篇 |
武器工业 | 376篇 |
无线电 | 2160篇 |
一般工业技术 | 7348篇 |
冶金工业 | 1796篇 |
原子能技术 | 281篇 |
自动化技术 | 381篇 |
出版年
2025年 | 278篇 |
2024年 | 938篇 |
2023年 | 1006篇 |
2022年 | 1269篇 |
2021年 | 1397篇 |
2020年 | 1418篇 |
2019年 | 1247篇 |
2018年 | 1171篇 |
2017年 | 1356篇 |
2016年 | 1149篇 |
2015年 | 1179篇 |
2014年 | 1839篇 |
2013年 | 1983篇 |
2012年 | 2388篇 |
2011年 | 2829篇 |
2010年 | 2145篇 |
2009年 | 2238篇 |
2008年 | 1903篇 |
2007年 | 2392篇 |
2006年 | 2321篇 |
2005年 | 1955篇 |
2004年 | 1751篇 |
2003年 | 1472篇 |
2002年 | 1237篇 |
2001年 | 1090篇 |
2000年 | 965篇 |
1999年 | 789篇 |
1998年 | 701篇 |
1997年 | 511篇 |
1996年 | 534篇 |
1995年 | 411篇 |
1994年 | 330篇 |
1993年 | 256篇 |
1992年 | 204篇 |
1991年 | 116篇 |
1990年 | 83篇 |
1989年 | 83篇 |
1988年 | 34篇 |
1987年 | 16篇 |
1986年 | 26篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1975年 | 1篇 |
1959年 | 3篇 |
1953年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Supported metal catalysts, particularly noble metals supported on SiO2, have attracted considerable attention due to the importance of the silica–metal interface in heterogeneous catalysis and in electronic device fabrication. Several important issues, e.g., the stability of the metal–oxide interface at working temperatures and pressures, are not well-understood. In this review, the present status of our understanding of the metal–silica interface is reviewed. Recent results of model studies in our laboratories on Pd/SiO2/Mo(1 1 2) using LEED, AES and STM are reported. In this work, epitaxial, ultrathin, well-ordered SiO2 films were grown on a Mo(1 1 2) substrate to circumvent complications that frequently arise from the silica–silicon interface present in silica thin films grown on silicon. 相似文献
2.
本文运用一典型的人工神经网络模型─“反向传播”模型,对高氧化态(Ⅱ─Ⅳ)三核金属簇合物的构型分布进行了分析,得到了较好的分类、预报结果为化合物结构分析提供了新的工具。 相似文献
3.
4.
It is shown that steady-state kinetic data do not allow the discrimination between the redox and associated mechanisms of the partial oxidation reactions. A discrimination between these mechanisms was performed using transient experiments. The obtained rate expressions are in agreement with experimental kinetic data for catalytic partial oxidation of o-xylene.
An influence of the conjugate oxidation of a catalyst surface on dynamics and kinetics of the heterogeneous catalytic oxidative reactions is considered. Computing simulation of methane oxidative coupling of methane reaction at lowered temperature and elevated pressure has been performed. It showed that the reaction order with respect to oxygen exceeding unity is consistent with the chain branching mechanism of the reaction in the presence of TiSi2 and TiB2 and showed the important role of the branching chain cycles in the low-temperature OCM reaction at elevated pressure. 相似文献
5.
6.
Because of its high–temperature chemical stability, SiC ceramic is a promising material for high-temperature device applications such as thermoelectric energy converters. However, the electrical conductivity of SiC ceramic is too low for it to be used as a thermoelectric energy converter at the cold junction. Therefore, we propose a SiC-Si functionally gradient material (FGM) in order to improve the electrical conductivity of the SiC ceramic at the cold junction. An SiC rod was fired in a temperature gradient furnace. One end of the SiC rod was maintained at 2473 K and the other end was maintained at 1973 K for 30 min. After firing, the porous SiC edge fired at 1973 K was dipped into molten Si in order to infiltrate molten Si into the porous SiC. The microstructure of the FGM is classified into three regions: the SiC-Si composite material; the porous SiC ceramic; and the densified SiC ceramic. The electrical conductivity, the Seebeck coefficient and the thermal conductivity for each region of SiC-Si FGM was measured at 300 K; a figure of merit was calculated. The figure of merit of the SiC-Si FGM at the cold junction, at room temperature, was 108 times higher than that of a nongradient SiC ceramic. 相似文献
7.
Asbestos fibres, of the chrysotile variety, and chopped carbon fibres were pretreated by an in-situ polycondensation technique eventually resulting in a polyamide coating on the fibre surface. Ionomer based composites containing either carbon or asbestos fibres in random in plane fibre orientation were prepared, and the influence of this coating process on the tensile properties was investigated. It was found that for the asbestos-filled composites the presence of the nylon 6,6 interlayer improves the tensile performance, especially at moderate polyamide depositions. This is not the case with the pretreated carbon-filled composites for which carbon fibres with higher polyamide contents are preferred. Combinations of the treated asbestos fibres with carbon and/or aramid fibres may be used to reduce the asbestos content in asbestos-only based engineering plastics. 相似文献
8.
Bilayered palladium (30 nm thick)–magnesium (350 nm thick) thin films were prepared using the pulsed laser deposition technique in the presence of various background gases (Ar, He and a mixture He + H2) under different partial pressures (47 and 27 Pa). According to the deposition atmosphere, the Pd/Mg interface shows either a sharp or an extended transition. The electrochemical hydriding properties and the mechanical stability upon cycling of the Pd/Mg film are greatly improved when an extended «intermixing» zone between the Pd and Mg layers is present. The Pd–Mg films prepared under pure helium fulfill these conditions. 相似文献
9.
Giampiero Sacchetti Paola Pittia Manuela Biserni Gian G. Pinnavaia & Marco D. Rosa 《International Journal of Food Science & Technology》2003,38(2):135-143
Summary Ready‐to‐eat breakfast cereals immersed in milk undergo undesirable changes in texture because of sudden moisture uptake. The textural changes are ascribable to a plasticizing effect of water, which modifies the mechanical strength of products by softening the starch/protein matrix. In this work, some textural parameters of different cereal flakes were derived from the force–displacement curves monitored during 300 s of immersion in milk. Hardness loss, deformability increment and changes in the force–displacement curve profile were calculated and plotted against soaking time. The application of a sugar coating process to a model cereal flake increased the initial product hardness and improved the preservation of the textural parameters during immersion. The Peleg model closely fitted the experimental data, with regression coefficients from 0.967 to 0.999. 相似文献
10.
研究了Al2O3-TiB2陶瓷刀具材料在1000℃下的氧化行为,用XRD、SEM分析了氧化后的相组成及显微结构。结果表明:Al2O3-TiB2陶瓷材料在1000℃空气中氧化增重符合抛物线规律;随TiB2含量的增加,该材料的抗氧化能力下降。 相似文献