全文获取类型
收费全文 | 5294篇 |
免费 | 156篇 |
国内免费 | 6篇 |
专业分类
化学 | 3470篇 |
晶体学 | 17篇 |
力学 | 91篇 |
数学 | 614篇 |
物理学 | 1264篇 |
出版年
2022年 | 35篇 |
2020年 | 69篇 |
2019年 | 64篇 |
2018年 | 43篇 |
2017年 | 40篇 |
2016年 | 108篇 |
2015年 | 87篇 |
2014年 | 124篇 |
2013年 | 214篇 |
2012年 | 217篇 |
2011年 | 254篇 |
2010年 | 148篇 |
2009年 | 128篇 |
2008年 | 239篇 |
2007年 | 247篇 |
2006年 | 234篇 |
2005年 | 239篇 |
2004年 | 215篇 |
2003年 | 140篇 |
2002年 | 138篇 |
2001年 | 108篇 |
2000年 | 89篇 |
1999年 | 79篇 |
1998年 | 71篇 |
1997年 | 95篇 |
1996年 | 93篇 |
1995年 | 67篇 |
1994年 | 90篇 |
1993年 | 98篇 |
1992年 | 76篇 |
1991年 | 56篇 |
1990年 | 65篇 |
1989年 | 56篇 |
1988年 | 55篇 |
1987年 | 71篇 |
1986年 | 76篇 |
1985年 | 83篇 |
1984年 | 87篇 |
1983年 | 61篇 |
1982年 | 62篇 |
1981年 | 46篇 |
1980年 | 61篇 |
1979年 | 53篇 |
1978年 | 58篇 |
1977年 | 73篇 |
1976年 | 57篇 |
1975年 | 40篇 |
1974年 | 34篇 |
1973年 | 51篇 |
1957年 | 30篇 |
排序方式: 共有5456条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
The growth of Ge and SiGe alloy films on Si substrates has attracted considerable interest in the last years because of their importance for optoelectronic devices as well as Si-based high speed transistors. Here we give a short overview on our recent real time stress measurements of Ge and SiGe alloy films on Si(0 0 1) performed with a sensitive cantilever beam technique and accompanied by structural investigations with atomic force microscopy. Characteristic features in the stress curves provide detailed insight into the development and relief of the misfit strain. For the Stranski–Krastanow system Ge/Si(0 0 1) as well as for SiGe films with Si contents below 20%, the strain relaxation proceeds mainly into two steps: (i) by the formation of 3D islands on top of the Ge wetting layer; (ii) via misfit dislocations in larger 3D islands and upon their percolation. 相似文献
25.
26.
Mária Meiarová Katarína Hubinská tefan Toma Burkhard Koch Albrecht Berkessel 《Monatshefte für Chemie / Chemical Monthly》2007,138(11):1181-1186
Summary.
N-Toluensulfonyl-l-prolin amide was tested as catalyst in the enantioselective Michael addition of carbonyl compounds to (E)-β-nitrostyrene in nine ionic liquids under different reaction conditions. The reaction rates and enantioselectivities were
strongly dependent on the ionic liquids. Change of enantioselectivity was observed too and it is attributed to both the cation
and the anion of ionic liquid. The best yields (up to 98%) and enantioselectivity (70% ee) of product were obtained in a basic ionic liquid [bmim]BF4 at room temperature. 相似文献
27.
28.
Rainer Koch Ralf Becker 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,84(4):423-435
After reviewing the presently available quadrature schemes for the discrete ordinates method, the accuracy of different schemes is analyzed and evaluated. It is shown from a comprehensive error analysis that the moment conditions have to satisfied not only for the principal coordinates directions, as it is mostly carried out, but for any arbitrary test direction. Among the schemes with approximately 50 discrete ordinates the DCT-020-2468 quadrature was found to give the best accuracy. The highest accuracy among all schemes is achieved by the LC-11 quadrature which requires 96 discrete ordinates. This scheme is rarely used up to date and deserves more attention for high accuracy predictions. 相似文献
29.
30.