全文获取类型
收费全文 | 97481篇 |
免费 | 9222篇 |
国内免费 | 4877篇 |
学科分类
工业技术 | 111580篇 |
出版年
2024年 | 318篇 |
2023年 | 1574篇 |
2022年 | 2757篇 |
2021年 | 4243篇 |
2020年 | 3101篇 |
2019年 | 2569篇 |
2018年 | 2860篇 |
2017年 | 3112篇 |
2016年 | 2931篇 |
2015年 | 4046篇 |
2014年 | 5031篇 |
2013年 | 5942篇 |
2012年 | 6536篇 |
2011年 | 7169篇 |
2010年 | 6442篇 |
2009年 | 5684篇 |
2008年 | 5832篇 |
2007年 | 5332篇 |
2006年 | 5243篇 |
2005年 | 4532篇 |
2004年 | 3203篇 |
2003年 | 2932篇 |
2002年 | 3174篇 |
2001年 | 2680篇 |
2000年 | 2298篇 |
1999年 | 2260篇 |
1998年 | 1789篇 |
1997年 | 1454篇 |
1996年 | 1338篇 |
1995年 | 1150篇 |
1994年 | 967篇 |
1993年 | 697篇 |
1992年 | 550篇 |
1991年 | 423篇 |
1990年 | 311篇 |
1989年 | 247篇 |
1988年 | 204篇 |
1987年 | 122篇 |
1986年 | 102篇 |
1985年 | 76篇 |
1984年 | 57篇 |
1983年 | 43篇 |
1982年 | 45篇 |
1981年 | 41篇 |
1980年 | 37篇 |
1979年 | 20篇 |
1978年 | 13篇 |
1976年 | 16篇 |
1975年 | 14篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
992.
Well-defined Ln2Sn2O7 powders (Ln = La, Sm and Gd) with a phase-pure pyrochlore structure were synthesized by hydrothermal reaction. The catalytic activities of Ln2Sn2O7 powders for methane combustion were measured. Methane oxidation started at 500 °C and increased with oxidation temperature. Catalytic methane combustion is strongly influenced by the presence of oxygen vacancies that form by breaking Sn–O lattice bonds as the temperature increases. Addition of manganese to the rare earth pyrochlores improved methane oxidation activity. Manganese-doped samarium stannate pyrochlore (Sm2Sn1.8Mn0.2O7) shows highest the catalytic activity. Light-off and complete oxidation temperatures were measured at about 400 and 650 °C, respectively. 相似文献
993.
注塑模具浇注系统三维参数化设计研究 总被引:3,自引:0,他引:3
注塑模的浇注系统包括主流道、分流道和浇口,运用基本特征的方法,把浇注系统作为设计特征,实现了浇注系统与成型零件的同时生成。 相似文献
994.
995.
By measuring Tg, Tm and Tc (cloud point) phase diagrams for the four miscible blends of chlorinated isotactic polypropylenes (chlorine content 39.2 (CPP-40) and 49.8 wt.-% (CP-50)) with Poly(ethylene-co-vinyl acetate)s (vinyl acetate contents 40 (EVA-40) and 45 wt.-% (EVA-45)) were investigated. The blend of CPP-50 with EVA-40 was the most compatible of the four blend pairs. 相似文献
996.
997.
Glass transition temperatures (Tg) of thin poly(styrene-co-methyl methacrylate) and poly(2-vinyl pyridine-co-styrene) films coated on a native oxide surface of Si wafer (100) were measured by ellipsometry. The thickness dependence of Tg can be properly fitted by previously suggested equation developed for homopolymers, based upon a continuous multi-layer model, although one component in thin random copolymer films demonstrates a slightly favorable interaction between a substrate and thin film, and another demonstrates a strongly favorable interaction. Surface and interface have a strong influence on Tg of thin film coated on substrate: the surface has the effect of reducing Tg, whereas the interface increases the Tg according to the degree of interaction between a substrate and thin film. This degree of interaction can be quantified as an interaction parameter (k), and is dependent on the composition of random copolymers. For the estimation of k values of thin random copolymer films, we proposed a parallel type additive function (1/kran=w1/k1+w2/k2) where w is a weight fraction of component. 相似文献
998.
999.
The steady gas-particle flow in risers under variant operating conditions was predicted based on a k-ε-kp-εp-Θ two-fluid model, which describes the dense turbulent gas-particle flow by the Eulerian method, considering the turbulence of both gas and particles as well as the particles' collisional effects. Much information on the macro flow behavior in risers, such as the profiles of local particle axial velocity, solids volume fraction, and solids mass flux in different operating regimes was obtained, and the predicted results show satisfactory agreement with experimental data. Further analysis of the predictions gives the comprehension of flow characteristics on the macro scale. 相似文献
1000.