全文获取类型
收费全文 | 7943篇 |
免费 | 317篇 |
国内免费 | 197篇 |
专业分类
化学 | 1094篇 |
晶体学 | 54篇 |
力学 | 566篇 |
综合类 | 28篇 |
数学 | 2361篇 |
物理学 | 2701篇 |
综合类 | 1653篇 |
出版年
2024年 | 10篇 |
2023年 | 43篇 |
2022年 | 95篇 |
2021年 | 133篇 |
2020年 | 132篇 |
2019年 | 101篇 |
2018年 | 99篇 |
2017年 | 150篇 |
2016年 | 180篇 |
2015年 | 181篇 |
2014年 | 271篇 |
2013年 | 498篇 |
2012年 | 282篇 |
2011年 | 358篇 |
2010年 | 283篇 |
2009年 | 464篇 |
2008年 | 433篇 |
2007年 | 505篇 |
2006年 | 472篇 |
2005年 | 359篇 |
2004年 | 289篇 |
2003年 | 341篇 |
2002年 | 317篇 |
2001年 | 285篇 |
2000年 | 341篇 |
1999年 | 244篇 |
1998年 | 285篇 |
1997年 | 157篇 |
1996年 | 136篇 |
1995年 | 133篇 |
1994年 | 97篇 |
1993年 | 106篇 |
1992年 | 104篇 |
1991年 | 63篇 |
1990年 | 63篇 |
1989年 | 56篇 |
1988年 | 68篇 |
1987年 | 67篇 |
1986年 | 42篇 |
1985年 | 61篇 |
1984年 | 43篇 |
1983年 | 17篇 |
1982年 | 23篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 14篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1973年 | 6篇 |
排序方式: 共有8457条查询结果,搜索用时 46 毫秒
911.
Alekeseev Anton Yu Recknagel Andreas Schomerus Volker 《Letters in Mathematical Physics》1997,41(2):169-180
In this Letter, we introduce a generalization of the Knizhnik–Zamolodchikov equations from affine Lie algebras to a wide class of conformal field theories (not necessarily rational). The new equations describe correlations functions of primary fields and of a finite number of their descendents. Our proposal is based on Nahm's concept of small spaces which provide adequate substitutes for the lowest energy subspaces in modules of affine Lie algebras. We explain how to construct the first order differential equations and investigate properties of the associated connections, thereby preparing the grounds for an analysis of quantum symmetries. The general considerations are illustrated in examples of Virasoro minimal models. 相似文献
912.
Funaki Y. Tohsaki A. Horiuchi H. Schuck P. Röpke G. 《The European Physical Journal A - Hadrons and Nuclei》2005,24(3):321-342
The states with Jπ = 0+, 2+, and 4+ of 12C with excitation energies less than about 15 MeV are investigated with the alpha condensate wave function with spatial deformation and by using the method of ACCC (analytic continuation in the coupling constant) which is necessary for a proper treatment of resonance states. The calculated energy and width of the recently observed 22+ state are found to be well reproduced. The obtained 22+ wave function has a large overlap with a single condensate wave function of 3α gas-like structure. The density distribution is shown to be almost the same as that of the 02+ state that is regarded as a 3α Bose-condensed state, if the energy of the 22+ state is scaled down to the same value as the one of the 02+ state. Furthermore, the kinetic energy, nuclear interaction energy, and Coulomb interaction energy of the calculated 22+ state are shown to be very similar to those of the 02+ state. We conclude that the 22+ state has a structure similar to the 02+ state of Bose-condensate character with a dilute 3α gas-like structure. In addition, the resonance states, 03+, 04+, 42+, are also discussed. 相似文献
913.
914.
Victor Tkachenko 《Journal of Mathematical Analysis and Applications》2005,303(1):173-187
We present several conditions sufficient for global stability of the zero solution of nonautonomous difference equation xn+1=qxn+fn(xn,…,xn−k), n∈Z, when the nonlinearities fn satisfy a sort of negative feedback condition. Moreover, for every k∈N, we indicate qk such that one of our stability conditions is sharp if q∈(0,qk]. We apply our results to discrete versions of Nicholson's blowflies equation, the Mackey-Glass equations, and the Wazewska and Lasota equation. 相似文献
915.
A core-envelope model for superdense matter distribution with the feature- core consisting of anisotropic fluid distribution
and envelope with isotropic fluid distribution is reported on the background of pseudospheroidal space-time. The physical
plausibility of the model is examined analytically and numerically. 相似文献
916.
Y. Nishiyama 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(3):335-340
Ground-state phase diagram of the one-dimensional bond-random S=1 Heisenberg antiferromagnet is investigated by means of the loop-cluster-update quantum Monte-Carlo method. The random couplings
are drawn from a rectangular uniform distribution. We found that even in the case of extremely broad bond distribution, the
magnetic correlation decays exponentially, and the correlation length is hardly changed; namely, the Haldane phase continues
to be realized. This result is accordant with that of the exact-diagonalization study, whereas it might contradict the conclusion
of an analytic theory founded in a power-law bond distribution instead. The latter theory predicts that a second-order phase
transition occurs at a certain critical randomness, and the correlation length diverges for sufficiently strong randomness.
Received: 31 March 1998 / Revised and Accepted: 7 July 1998 相似文献
917.
918.
919.
A frequently occurring problem is to find a probability vector,p∈D, which minimizes theI-divergence between it and a given probability vector π. This is referred to as theI-projection of π ontoD. Darroch and Ratcliff (1972,Ann. Math. Statist.,43, 1470–1480) gave an algorithm whenD is defined by some linear equalities and in this paper, for simplicity of exposition, we propose an iterative procedure whenD is defined by some linear inequalities. We also discuss the relationship betweenI-projection and the maximum likelihood estimation for multinomial distribution. All of the results can be applied to isotonic
cone. 相似文献
920.
Partial electron density plots were calculated for a model SrTiO3(100) surface with √5 × √5 ordered oxygen vacancy to examine why the bright spots of the scanning tunneling microscopy (STM) images of SrTiO3(100) observed in ultrahigh vacuum (UHV) correspond to the oxygen vacancy sites. Possible dependence of the image on the polarity and magnitude of the bias voltage was also discussed on the basis of partial electron density plot calculations. Our study strongly suggests that the UHV STM imaging involves the lowest-lying d-block level of every two Ti3+ centers adjacent to an oxygen vacancy, the tip-sample distance involved in the UHV STM experiments is substantially larger than that involved in typical ambient-condition STM imaging, and the Ti4+ and Ti3+ sites of SrTiO3(100) are reconstructed. 相似文献