全文获取类型
收费全文 | 233篇 |
免费 | 29篇 |
国内免费 | 37篇 |
专业分类
化学 | 26篇 |
力学 | 9篇 |
综合类 | 2篇 |
数学 | 125篇 |
物理学 | 137篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2017年 | 12篇 |
2016年 | 6篇 |
2015年 | 2篇 |
2014年 | 11篇 |
2013年 | 18篇 |
2012年 | 2篇 |
2011年 | 17篇 |
2010年 | 5篇 |
2009年 | 12篇 |
2008年 | 23篇 |
2007年 | 24篇 |
2006年 | 18篇 |
2005年 | 13篇 |
2004年 | 16篇 |
2003年 | 13篇 |
2002年 | 10篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 5篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有299条查询结果,搜索用时 31 毫秒
121.
John D. Morgan III 《Theoretical chemistry accounts》1986,69(3):181-223
It is proved by functional analytic methods that for S-state solutions of Schrödinger's equation for the helium atom, Fock's expansion in powers of R
1/2 and R ln R, where R is the hyperspherical radius r
1
2
+r
2
2
, converges pointwise for all R, thereby generalising a result of Macek that the expansion converges in the mean for all R<1/2. It is shown that for any value (even complex) of the energy E, Schrödinger's equation, considered as a partial differential equation with no boundary condition at R=, has infinitely many solutions representable by an expansion of the type proposed by Fock. Some of the open problems are discussed in determining whether for E in the point spectrum of the atomic Hamiltonian the physical eigenfunction E, which has exponential decay as R , is representable by Fock's expansion. 相似文献
122.
N. Aquino G. Campoy A. Flores‐Riveros 《International journal of quantum chemistry》2005,103(3):267-277
A study of the two‐dimensional hydrogen atom confined within a circle of impenetrable walls is presented. The potential inside the box is Coulomb type, whereas outside it is infinite. The energy eigenvalues and some radial wave function properties are computed with high accuracy for different box sizes. We derive the polarizability in the Kirkwood approximation, calculate the Fermi contact term as a function of the confinement radius, and investigate the filling order of the one‐electron states. When the electronic configuration of many electrons is constructed by means of the Aufbau principle, the model predicts the inversion 2s–3d levels in the N atom. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
123.
Two very hard particle models are solved and the nonuniqueness of the initial value problem for these (model) kinetic equations is explicitly demonstrated, when distribution functions decaying sufficiently slowly are permitted. The intimate connection between nonuniqueness and violation of conservation laws is made evident. The associated eigenvalue problems are solved. Finally, the general implications of these results for kinetic equations with transition rates that are increasing functions of the state variable, are stated in the form of a number of conjectures. They affect the solution of the Boltzmann equation for realistic intermolecular interactions when the collision rategI(g, ) is an increasing function of the relative velocityg. 相似文献
124.
On the uniform convergence of the Fourier series for one spectral problem with a spectral parameter in a boundary condition
下载免费PDF全文
![点击此处可从《Mathematical Methods in the Applied Sciences》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this paper, we investigate the uniform convergence of the Fourier series expansions in terms of eigenfunctions for the spectral problem where λ is a spectral parameter, q(x) is a real‐valued continuous function on the interval [0,1], and a1,b0,b1,c1,d0, and d1 are real constants that satisfy the conditions Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
125.
We propose a new method to analyze and efficiently represent data recorded on a domain of general shape in by computing the eigenfunctions of Laplacian defined over there and expanding the data into these eigenfunctions. Instead of directly solving the eigenvalue problem on such a domain via the Helmholtz equation (which can be quite complicated and costly), we find the integral operator commuting with the Laplacian and diagonalize that operator. Although our eigenfunctions satisfy neither the Dirichlet nor the Neumann boundary condition, computing our eigenfunctions via the integral operator is simple and has a potential to utilize modern fast algorithms to accelerate the computation. We also show that our method is better suited for small sample data than the Karhunen–Loève transform/principal component analysis. In fact, our eigenfunctions depend only on the shape of the domain, not the statistics of the data. As a further application, we demonstrate the use of our Laplacian eigenfunctions for solving the heat equation on a complicated domain. 相似文献
126.
Michel Marias 《Transactions of the American Mathematical Society》1998,350(11):4367-4375
Eigenfunctions of the Laplacian on a negatively curved, rotationally symmetric manifold are constructed explicitly under the assumption that an integral of converges. This integral is the same one which gives the existence of nonconstant harmonic functions on
127.
Xiao Huang Yanxiang Bao Jiaying Qin Xingshi Zheng Xizhang Luo 《International Journal of Infrared and Millimeter Waves》1998,19(12):1711-1720
Using the CH3OH molecular energy levels data base management program, we deduced that when a CH3OH laser pumped by CO2-9P(16) line, there should be a FIR laser line of 918m wavelength, which corresponding to a transition in ground-state reversed three-level energy system. For the first time, the spectra of ground-state reversed three-level system transitions were calculated by solving the density matrix equations, and the spectrum characteristics of 918m line were studied. Experimentally, the CH3OH FIR laser line of 918m wavelength was obtained by pumping with a TEA-CO2 laser. The experimental results were in good agreement with the theoretical calculations. 相似文献
128.
J. Bendisch 《Journal of statistical physics》1992,67(5-6):1209-1217
For square, triangular, and for hexagonal lattices there is numerical and theoretical support that the ground-state thresholdp
c
between ferro- and paramagnetism in random 2D Ising ±J models, withp as the concentration of antiferromagnetic bonds, is identical top
*which is characterized by minimal matching properties of frustrated plaquettes. From square lattices of size 100×100 we have got pc,sq<0.117 by simulations which produced average groundstate magnetizations per spin by means of exact minimal matchings. Moreover, from the squareL×L-lattices treated (L = 10, 20, 50, 100) we obtained the estimatep
c,sq
0.1 which is in agreement with the Grinstein estimatep
c,sq
0.099 andp
c,sq
0.105 by Freund and Grassberger. 相似文献
129.
计算双电子原子基态能量的坐标张弛变分法 总被引:3,自引:0,他引:3
给出了一种计算双电子原子基态能量和波函数的坐标张弛的变分方法.同时,利用Matlab语言开发了一个软件程序,对He原子和类He离子的基态能量进行了变分计算. 相似文献
130.
RUANYong-Hong CHENQing-Hu JIAOZheng-Kuan 《理论物理通讯》2004,42(5):785-788
We apply a Feynman path-integral variational approach combining with the average for the relative motion to study the stability of bipolaron in a quantum dot. The binding energy is calculated in different parameters. We find that an optimum quantum potential favors the formation of bipolaron. Compared with other methods in literature, the present approach is better than Laudau Pekar one in all coupling regime and full path-integral one in the strong coupling regime. 相似文献