全文获取类型
收费全文 | 12286篇 |
免费 | 363篇 |
国内免费 | 24篇 |
专业分类
化学 | 8056篇 |
晶体学 | 59篇 |
力学 | 168篇 |
数学 | 1682篇 |
物理学 | 2708篇 |
出版年
2020年 | 119篇 |
2019年 | 109篇 |
2016年 | 272篇 |
2015年 | 229篇 |
2014年 | 219篇 |
2013年 | 459篇 |
2012年 | 447篇 |
2011年 | 569篇 |
2010年 | 301篇 |
2009年 | 284篇 |
2008年 | 481篇 |
2007年 | 484篇 |
2006年 | 430篇 |
2005年 | 472篇 |
2004年 | 401篇 |
2003年 | 338篇 |
2002年 | 277篇 |
2001年 | 199篇 |
2000年 | 178篇 |
1999年 | 176篇 |
1998年 | 154篇 |
1997年 | 189篇 |
1996年 | 192篇 |
1995年 | 194篇 |
1994年 | 165篇 |
1993年 | 192篇 |
1992年 | 184篇 |
1991年 | 162篇 |
1990年 | 137篇 |
1989年 | 155篇 |
1988年 | 168篇 |
1987年 | 154篇 |
1986年 | 159篇 |
1985年 | 189篇 |
1984年 | 162篇 |
1983年 | 156篇 |
1982年 | 169篇 |
1981年 | 155篇 |
1980年 | 147篇 |
1979年 | 142篇 |
1978年 | 137篇 |
1977年 | 128篇 |
1976年 | 132篇 |
1975年 | 116篇 |
1974年 | 131篇 |
1973年 | 129篇 |
1961年 | 160篇 |
1960年 | 211篇 |
1959年 | 117篇 |
1958年 | 131篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Ledzewicz U. Nowakowski A. Schättler H. 《Journal of Optimization Theory and Applications》2004,122(2):345-370
It is shown that, if a parametrized fämily of extremals F can be stratified in a way compatible with the flow map generated by F, then those trajectories of the family which realize the minimal values of the cost in F are indeed optimal in comparison with all trajectories which lie in the region R covered by the trajectories of F. It is not assumed that F is a field covering the state space injectively. As illustration, an optimal synthesis is constructed for a system where the flow of extremals exhibits a simple cusp singularity. 相似文献
32.
Klaus Thomsen 《Transactions of the American Mathematical Society》2004,356(9):3557-3619
The structure of a sofic shift space is investigated, and Krieger's embedding theorem and Boyle's factor theorem are generalized to a large class of sofic shifts.
33.
Andrzej Dabrowski Erich Robens Peter Klobes Klaus Meyer Przemyslaw Podkocielny 《Particle & Particle Systems Characterization》2003,20(5):311-322
Since a comprehensive survey published in 1999 [1] much work was done in standardizing measuring methods to characterize the surface geometry of dispersed and/or porous solids and to certify reference materials. The present paper is an extension of a short communication [2]. It gives a survey on existing standards and reports on new drafts and proposals. 相似文献
34.
35.
36.
37.
38.
39.
40.
D. Hugh Powell Andr E. Merbach Gabriel Gonzlez Ern Brücher Kroly Micskei M. Francesca Ottaviani Klaus Khler Alex Von Zelewsky Oleg Ya. Grinberg Yakob S. Lebedev 《Helvetica chimica acta》1993,76(5):2129-2146
EPR Spectra have been measured for aqueous solutions of a series of Gd3+ complexes at variable temperature and a range of magnetic fields; S-band (0.14 T), X-band (0.34 T), Q-band (1.2 T), and 2-mm-band (5.0 T). The major contribution to the observed line widths is magnetic-field-dependent and is interpreted as being due to the modulation of the zero-field splitting produced by distortion of the complexes from perfect symmetry. The transverse and longitudinal relaxation matrices for an 8S ion with such an interaction have been calculated using Redfield theory with vector-coupling methods, and diagonalised numerically to obtain relaxation rates and intensities for the degenerate transitions which contribute to the multiplet. The observed line width, which is inversely proportional to the magnetic field at low temperatures, is best described by the intensity-weighted mean transverse relaxation time for the four transitions with non-zero intensity. A least-squares fit of the data yields the square of the zero-field splitting tensor, Δ2, and a correlation time, τv, with activation energy, Ev. The physical significance of these parameters and the extent of validity of the theoretical approach are considered. The parameters are used to predict the magnetic-field dependence of the longitudinal and transverse electronic relaxation times, which are discussed in the context of their relevance to 1H-NMR relaxivity. 相似文献