全文获取类型
收费全文 | 1083篇 |
免费 | 81篇 |
国内免费 | 67篇 |
专业分类
化学 | 462篇 |
晶体学 | 2篇 |
力学 | 56篇 |
综合类 | 3篇 |
数学 | 269篇 |
物理学 | 439篇 |
出版年
2023年 | 14篇 |
2022年 | 10篇 |
2021年 | 25篇 |
2020年 | 29篇 |
2019年 | 25篇 |
2018年 | 30篇 |
2017年 | 22篇 |
2016年 | 22篇 |
2015年 | 34篇 |
2014年 | 37篇 |
2013年 | 82篇 |
2012年 | 43篇 |
2011年 | 42篇 |
2010年 | 31篇 |
2009年 | 65篇 |
2008年 | 82篇 |
2007年 | 78篇 |
2006年 | 62篇 |
2005年 | 41篇 |
2004年 | 52篇 |
2003年 | 51篇 |
2002年 | 47篇 |
2001年 | 33篇 |
2000年 | 38篇 |
1999年 | 33篇 |
1998年 | 24篇 |
1997年 | 23篇 |
1996年 | 15篇 |
1995年 | 10篇 |
1994年 | 15篇 |
1993年 | 8篇 |
1992年 | 17篇 |
1991年 | 5篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 3篇 |
排序方式: 共有1231条查询结果,搜索用时 31 毫秒
71.
Rafael?D.?BenguriaEmail author Semjon?A.?Vugalter 《Letters in Mathematical Physics》2004,70(3):249-257
For the Pauli–Fierz operator with a short range potential we study the binding threshold 1() as a function of the fine structure constant and show that it converges to the binding threshold for the Schrödinger operator in the limit 0.This work was supported in part by Fondecyt (Chile), Project #102-0844. Work partially supported by HPRN-CT-2002-00277, and the Volkswagen Stiftung through a cooperation grant. 相似文献
72.
On the nature of the BOLD fMRI contrast mechanism 总被引:17,自引:0,他引:17
Since its development about 15 years ago, functional magnetic resonance imaging (fMRI) has become the leading research tool for mapping brain activity. The technique works by detecting the levels of oxygen in the blood, point by point, throughout the brain. In other words, it relies on a surrogate signal, resulting from changes in oxygenation, blood volume and flow, and does not directly measure neural activity. Although a relationship between changes in brain activity and blood flow has long been speculated, indirectly examined and suggested and surely anticipated and expected, the neural basis of the fMRI signal was only recently demonstrated directly in experiments using combined imaging and intracortical recordings. In the present paper, we discuss the results obtained from such combined experiments. We also discuss our current knowledge of the extracellularly measured signals of the neural processes that they represent and of the structural and functional neurovascular coupling, which links such processes with the hemodynamic changes that offer the surrogate signal that we use to map brain activity. We conclude by considering applications of invasive MRI, including injections of paramagnetic tracers for the study of connectivity in the living animal and simultaneous imaging and electrical microstimulation. 相似文献
73.
In [9] we introduced the notion of equilibrium surface current JdSx on the closed C smooth surfaces in R
3 as a generalization of electric solenoid, and proved their existence. We here show an algorithm for JdSx starting from a given surface current J dSx on . 相似文献
74.
M. M. Cavalcanti V. N. Domingos Cavalcanti J. A. Soriano L. A. Medeiros 《Southeast Asian Bulletin of Mathematics》2000,24(2):183-199
In this paper, we study a hyperbolic model based on the equation
with nonlinear boundary conditions given by
.We prove the existence and the uniqueness of global solutions. Also, we obtain the uniform decay of the energy without control of its derivative sign.AMS Subject Classification (2000), 35L05, 35L70, 35B40 相似文献
75.
76.
We show that the exact energy eigenvalues and eigenfunctions of the Schrödinger equation for charged particles moving in certain class of non-central potentials can be easily calculated analytically in a simple and elegant manner by using Nikiforov and Uvarov (NU) method. We discuss the generalized Coulomb and harmonic oscillator systems. We study the Hartmann Coulomb and the ring-shaped and compound Coulomb plus Aharanov–Bohm potentials as special cases. The results are in exact agreement with other methods. 相似文献
77.
78.
In this paper, we propose a high order Fourier spectral-discontinuous Galerkin method for time-dependent Schrödinger–Poisson equations in 3-D spaces. The Fourier spectral Galerkin method is used for the two periodic transverse directions and a high order discontinuous Galerkin method for the longitudinal propagation direction. Such a combination results in a diagonal form for the differential operators along the transverse directions and a flexible method to handle the discontinuous potentials present in quantum heterojunction and supperlattice structures. As the derivative matrices are required for various time integration schemes such as the exponential time differencing and Crank Nicholson methods, explicit derivative matrices of the discontinuous Galerkin method of various orders are derived. Numerical results, using the proposed method with various time integration schemes, are provided to validate the method. 相似文献
79.
Alexandre Almeida Humberto Rafeiro 《Journal of Mathematical Analysis and Applications》2008,340(2):1336-1346
We study the inversion problem of the Bessel potential operator within the frameworks of the weighted Lebesgue spaces with variable exponent. The inverse operator is constructed by using approximative inverse operators. This generalizes some classical results to the variable exponent setting. 相似文献
80.
I. Chudinovich 《Journal of Mathematical Analysis and Applications》2008,339(2):1024-1043
The initial-boundary value problems with the Dirichlet and Neumann boundary conditions arising in the theory of bending of thermoelastic plates with transverse shear deformation are reduced to time-dependent boundary integral equations by means of layer potentials. The solvability of these equations is then investigated in Sobolev-type spaces. 相似文献