全文获取类型
收费全文 | 32438篇 |
免费 | 3670篇 |
国内免费 | 2256篇 |
专业分类
化学 | 2052篇 |
晶体学 | 19篇 |
力学 | 3705篇 |
综合类 | 442篇 |
数学 | 22875篇 |
物理学 | 9271篇 |
出版年
2024年 | 77篇 |
2023年 | 344篇 |
2022年 | 388篇 |
2021年 | 510篇 |
2020年 | 968篇 |
2019年 | 939篇 |
2018年 | 879篇 |
2017年 | 844篇 |
2016年 | 932篇 |
2015年 | 780篇 |
2014年 | 1493篇 |
2013年 | 2800篇 |
2012年 | 1538篇 |
2011年 | 2052篇 |
2010年 | 1855篇 |
2009年 | 2052篇 |
2008年 | 2185篇 |
2007年 | 2096篇 |
2006年 | 1816篇 |
2005年 | 1790篇 |
2004年 | 1481篇 |
2003年 | 1463篇 |
2002年 | 1279篇 |
2001年 | 965篇 |
2000年 | 920篇 |
1999年 | 877篇 |
1998年 | 838篇 |
1997年 | 691篇 |
1996年 | 531篇 |
1995年 | 426篇 |
1994年 | 387篇 |
1993年 | 249篇 |
1992年 | 223篇 |
1991年 | 232篇 |
1990年 | 202篇 |
1989年 | 114篇 |
1988年 | 125篇 |
1987年 | 115篇 |
1986年 | 117篇 |
1985年 | 110篇 |
1984年 | 112篇 |
1983年 | 53篇 |
1982年 | 100篇 |
1981年 | 89篇 |
1980年 | 64篇 |
1979年 | 60篇 |
1978年 | 47篇 |
1977年 | 40篇 |
1976年 | 27篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
正交变换在重积分中某些应用 总被引:2,自引:0,他引:2
姚云飞 《数学的实践与认识》2003,33(9):139-144
正交变换是代数学的基本内容 ,其用途十分广泛 .重积分的计算往往存在技术性的困难 ,若利用“正交变换”的有关理论去解决某些重积分的计算问题是颇有功效的 .本文将以“正交变换”为工具 ,简洁的处理重积分的某些问题 相似文献
102.
The Hawking radiation of Dirac particles on the event horizon of a nonuniformly rectilinearly accelerating black hole is studied in this paper. First, we construct the symmetrized null tetrad from which the spin coefficients and Dirac equation are derived. Next, by proposing generalized tortoise coordinate transformation, the decoupling problem of the Dirac equation with nonzero rest mass is solved. Finally, by analytic continuation, the Hawking thermal spectrum formula of Dirac particle for nonuniformly rectilinearly accelerating black hole is obtained. 相似文献
103.
We show that functions which are invariant for suitable product semigroups (one of which is a quasi-Poisson semigroup on a general state space) decompose into a singular eigen-function and a mixture of products of minimal eigen-functions. 相似文献
104.
M. I. Gil' 《Proceedings of the American Mathematical Society》2003,131(12):3737-3746
A linear operator in a separable Hilbert space is called a quasinormal one if it is a sum of a normal operator and a compact one. In the paper, bounds for the spectrum of quasinormal operators are established. In addition, the lower estimate for the spectral radius is derived. Under some restrictions, that estimate improves the well-known results. Applications to integral operators and matrices are discussed. Our results are new even in the finite-dimensional case.
105.
本文利用比较原理以及一种特殊变换研究了一类非线性退化方程的混合问题,得到了这类复杂问题解的渐进性质。 相似文献
106.
107.
We construct a multiplicative group structure in the class of integro-differential operators specific for a polydisk which was introduced by I. I. Bavrin. We indicate two applications of these operators to solution of functional equations. 相似文献
108.
New Exact Solutions to the Combined KdV and mKdV Equation 总被引:2,自引:0,他引:2
Yan-ze Peng 《International Journal of Theoretical Physics》2003,42(4):863-868
The modified mapping method is developed to obtain new exact solutions to the combined KdV and mKdV equation. The method is applicable to a large variety of nonlinear evolution equations, as long as odd- and even-order derivative terms do not coexist in the equation under consideration. 相似文献
109.
THE COUPLING OF NATURAL BOUNDARY ELEMENT AND FINITE ELEMENT METHOD FOR 2D HYPERBOLIC EQUATIONS 总被引:2,自引:0,他引:2
De-haoYu Qi-kuiDu 《计算数学(英文版)》2003,21(5):585-594
In this paper, we investigate the coupling of natural boundary element and finite element methods of exterior initial boundary value problems for hyperbolic equations. The governing equation is first discretized in time, leading to a time-step scheme, where an exterior elliptic problem has to be solved in each time step. Second, a circular artificial boundary FR consisting of a circle of radius R is introduced, the original problem in an unbounded domain is transformed into the nonlocal boundary value problem in abounded subdomain. And the natural integral equation and the Poisson integral formula are obtained in the infinite domainΩ2 outside circle of radius R. The coupled variational formulation is given. Only the function itself, not its normal derivative at artificial boundary ΓR, appears in the variational equation, so that the unknown numbers are reducedand the boundary element stiffness matrix has a few different elements. Such a coupled method is superior to the one based on direct boundary element method. This paper discusses finite element discretization for variational problem and its corresponding numerical technique, and the convergence for the numerical solutions. Finally, the numerical example is presented to illustrate feasibility and efficiency of this method. 相似文献
110.
A pseudopotential depending on an effective core radius is proposed to study the binding energy, equation of state, ion-ion
interaction, phonon dispersion curves (q-space and r-space analysis), mode Grüneisen parameters and dynamical elastic constants
of some fcc f-shell metals La, Yb, Ce and Th. The contribution of the s-like electrons is calculated in the second-order perturbation
theory for the potential while d and f-like electron is taken into account by introducing repulsive short-range Born-Mayer
term. The parameter of the potential is evaluated by zero pressure condition. An excellent agreement between theoretical investigations
and experimental findings is achieved which confirms the present formalism 相似文献