全文获取类型
收费全文 | 14844篇 |
免费 | 719篇 |
国内免费 | 54篇 |
专业分类
化学 | 11101篇 |
晶体学 | 83篇 |
力学 | 209篇 |
数学 | 2276篇 |
物理学 | 1948篇 |
出版年
2023年 | 94篇 |
2022年 | 114篇 |
2021年 | 201篇 |
2020年 | 282篇 |
2019年 | 253篇 |
2018年 | 177篇 |
2017年 | 158篇 |
2016年 | 513篇 |
2015年 | 483篇 |
2014年 | 518篇 |
2013年 | 670篇 |
2012年 | 900篇 |
2011年 | 967篇 |
2010年 | 682篇 |
2009年 | 586篇 |
2008年 | 923篇 |
2007年 | 785篇 |
2006年 | 782篇 |
2005年 | 758篇 |
2004年 | 689篇 |
2003年 | 506篇 |
2002年 | 466篇 |
2001年 | 241篇 |
2000年 | 207篇 |
1999年 | 225篇 |
1998年 | 184篇 |
1997年 | 230篇 |
1996年 | 192篇 |
1995年 | 180篇 |
1994年 | 178篇 |
1993年 | 153篇 |
1992年 | 152篇 |
1991年 | 130篇 |
1990年 | 96篇 |
1989年 | 125篇 |
1988年 | 110篇 |
1987年 | 83篇 |
1986年 | 95篇 |
1985年 | 128篇 |
1984年 | 130篇 |
1983年 | 74篇 |
1982年 | 117篇 |
1981年 | 117篇 |
1980年 | 98篇 |
1979年 | 89篇 |
1978年 | 97篇 |
1977年 | 64篇 |
1976年 | 80篇 |
1975年 | 75篇 |
1973年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
21.
22.
Arno Jüschke Johannes Jahn Andreas Kirsch 《Computational Optimization and Applications》1997,7(3):261-276
In this paper we consider a special optimization problem withtwo objectives which arises in antenna theory. It is shown that thisabstract bicriterial optimization problem has at least one solution.Discretized versions of this problem are also discussed, and therelationships between these finite dimensional problems and the infinitedimensional problem are investigated. Moreover, we presentnumerical results for special parameters using a multiobjectiveoptimization method. 相似文献
23.
24.
25.
26.
Summary We study a countable system of interacting diffusions on the interval [0,1], indexed by a hierarchical group. A particular choice of the interaction guaranties, we are in the diffusive clustering regime. This means clusters of components with values either close to 0 or close to 1 grow on various different scales. However, single components oscillate infinitely often between values close to 0 and close to 1 in such a way that they spend fraction one of their time together and close to the boundary. The processes in the whole class considered and starting with a shift-ergodic initial law have the same qualitative properties (universality). 相似文献
27.
28.
Summary In the present paper we study truncated projections for the fanbeam geometry in computerized tomography. First we derive consistency conditions for the divergent beam transform. Then we study a singular value decomposition for the case where only the interior rays in the fan are provided, as for example in region-of-interest tomography. We show that the high angular frequency components of the searched-for densities are well determined and we present reconstructions from real data where the missing information is approximated based on the singular value decomposition.The work of the authors was supported by the Deutsche Forschungsgemeinschaft under grant Lo 310/2-4 相似文献
29.
This work is aimed at the optimization of the yield and purity of non-symmetrical trialkyl sulfonium halide salts. The effects of parameters such as solvent, temperature and concentration were studied. The products were carefully analyzed and the crystal structure of [{n-CH3(CH2)15}(CH3)2S]Br determined. The overall aim of the present study is future syntheses of low-dimensional magnetic materials. 相似文献
30.
Andreas Lüttge 《Journal of Electron Spectroscopy and Related Phenomena》2006,150(2-3):248-259
The dependence of dissolution rates on the difference of Gibbs free energy is of critical importance for our understanding of crystal dissolution, reactive flow models and their applications to a variety of environmentally related problems. Here, we review experimental data generated with mineral powders and single crystals to develop a better understanding of apparent inconsistencies between otherwise internally consistent data sets. Additional information from direct surface observations and measurements with vertical scanning interferometry (VSI) and atomic force microscopy (AFM) of albite dissolution at 25, 150 and 185 °C may shed new light on this old but unsolved question. Our discussion is based on the importance of etch pit development, its ΔG dependence, and the pits’ role as a source for steps and step movement in the dissolution process. Results indicate that reaction history may be of critical importance in determining the overall reaction mechanism and its rate. Different rates are observed for systems having otherwise identical ΔGr acquired from increasing versus decreasing disequilibrium positions.
In this context, we finally discuss the validity of the common application of transition state theory (TST) to elementary and overall reactions governing the dissolution process. In this discussion of crystal dissolution, we contrast TST applications with a stochastic, many-body treatment that has led to the development of a stepwave model. This discussion also focuses on the controversy caused by the rivalry between surface adsorption models and a probabilistic model that seeks to incorporate the full three-dimensional crystal structure. 相似文献