全文获取类型
收费全文 | 121550篇 |
免费 | 16666篇 |
国内免费 | 154篇 |
专业分类
化学 | 101685篇 |
晶体学 | 494篇 |
力学 | 4299篇 |
数学 | 15124篇 |
物理学 | 16768篇 |
出版年
2023年 | 4390篇 |
2022年 | 1893篇 |
2021年 | 3165篇 |
2020年 | 5357篇 |
2019年 | 3192篇 |
2018年 | 3720篇 |
2017年 | 1902篇 |
2016年 | 7661篇 |
2015年 | 7206篇 |
2014年 | 6760篇 |
2013年 | 9459篇 |
2012年 | 8276篇 |
2011年 | 6589篇 |
2010年 | 6448篇 |
2009年 | 5828篇 |
2008年 | 5794篇 |
2007年 | 5554篇 |
2006年 | 4394篇 |
2005年 | 4087篇 |
2004年 | 3465篇 |
2003年 | 2738篇 |
2002年 | 2468篇 |
2001年 | 1599篇 |
2000年 | 1304篇 |
1999年 | 1005篇 |
1998年 | 769篇 |
1997年 | 715篇 |
1996年 | 910篇 |
1995年 | 680篇 |
1994年 | 694篇 |
1993年 | 840篇 |
1992年 | 734篇 |
1991年 | 567篇 |
1990年 | 552篇 |
1989年 | 537篇 |
1985年 | 672篇 |
1984年 | 644篇 |
1982年 | 596篇 |
1981年 | 590篇 |
1980年 | 574篇 |
1979年 | 565篇 |
1978年 | 543篇 |
1977年 | 609篇 |
1976年 | 707篇 |
1975年 | 768篇 |
1974年 | 781篇 |
1973年 | 611篇 |
1970年 | 659篇 |
1969年 | 539篇 |
1968年 | 579篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Giang Truong Nguyen Prof. Dr. Liviu Ungur 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202200227
Employing radical bridges between anisotropic metal ions has been a viable route to achieve high-performance single-molecule magnets (SMMs). While the bridges have been mainly considered for their ability to promote exchange interactions, the crystal-field effect arising from them has not been taken into account explicitly. This lack of consideration may distort the understanding and limit the development of the entire family. To shed light on this aspect, herein we report a theoretical investigation of a series of N -radical-bridged diterbium complexes. It is found that while promoting strong exchange coupling between the terbium ions, the N -radical induces a crystal field that interferes destructively with that of the outer ligands, and thus reduces the overall SMM behavior. Based on the theoretical results, we conclude that the SMM behavior in this series could be further maximized if the crystal field of the outer ligands is designed to be collinear with that of the radical bridge. This conclusion can be generalized to all exchange-coupled SMMs. 相似文献
2.
3.
NaY zeolite samples loaded with sodium metal by vapor phase deposition have been investigated using129Xe NMR spectroscopy. At low sodium concentration, the129Xe NMR spectrum showed three resonance lines which clearly indicate the existence of distinct domains in the zeolite sample. Such an observation suggests that the diffusion of the xenon atoms into each domain only occurs with respect to the NMR time scale (2.9 ms). As the sodium concentration increases, observation of a single broad line indicate a macroscopic homogenization of the system. The shift of this line is explained in part due to a paramagnetic interaction between the xenon atoms and the unpaired electrons of particles containing an odd number of sodium atoms. The linewidth is due to the distribution of the local magnetic fields partially averaged by the rapid motion of the xenon atoms and to the statistical distribution of the sodium particles in the supercage cavities. The paramagnetic interaction vanishes with the oxidation of the sample leading to a narrowing and a shift of the line to higher magnetic fields. 相似文献
4.
5.
6.
7.
A. I. Magunov A. Ya. Faenov I. Yu. Skobelev T. A. Pikuz E. Biémont P. Quinet F. Blasco C. Bonte F. Dorchies T. Caillaud F. Salin C. Stenz 《Journal of Experimental and Theoretical Physics》2002,95(6):998-1005
The satellite structure of 1s2p 1,3 P 1-1s 21 S 0 lines of the He-like argon ion in plasma produced by a 45-fs laser pulse in a gas-jet cluster target is measured with a high spectral resolution. Radiation transitions 2p → 1s from autoionizing states (AISs) are detected for ions ranging from Li-like to F-like. The spectrum observed is theoretically simulated with the use of the spectroscopic data for the AISs of multicharged ions obtained within the multiconfiguration relativistic Hartree-Fock method. Good agreement with experimental data is obtained when the main population channels of these states are taken into account for typical values of cluster-target plasma parameters. 相似文献
8.
Michel Hébert 《Archive for Mathematical Logic》1991,31(2):133-143
Summary We give a syntactic characterization of (finitary) theories whose categories of models are closed under the formation of connected limits (respectively the formation of pullbacks and substructures) in the category of all structures. They are also those theories whose consistent extensions by new atomic facts admit in each component an initial structure (respectively an initial term structure), and also thoseT for whichM(T) is locally finitely multi-presentable in a canonical way. We also show that these two properties of theories are nonuniform. 相似文献
9.
Lubomír Kubáček 《Applications of Mathematics》2006,51(6):565-582
Some remarks to problems of point and interval estimation, testing and problems of outliers are presented in the case of multivariate
regression model.
This work was supported by the Council of Czech Government J14/98:153100011. 相似文献
10.