全文获取类型
收费全文 | 6094篇 |
免费 | 600篇 |
国内免费 | 257篇 |
专业分类
化学 | 773篇 |
晶体学 | 24篇 |
力学 | 110篇 |
综合类 | 31篇 |
数学 | 4157篇 |
物理学 | 1856篇 |
出版年
2023年 | 27篇 |
2022年 | 40篇 |
2021年 | 71篇 |
2020年 | 94篇 |
2019年 | 170篇 |
2018年 | 175篇 |
2017年 | 112篇 |
2016年 | 101篇 |
2015年 | 96篇 |
2014年 | 228篇 |
2013年 | 425篇 |
2012年 | 293篇 |
2011年 | 402篇 |
2010年 | 376篇 |
2009年 | 484篇 |
2008年 | 509篇 |
2007年 | 423篇 |
2006年 | 373篇 |
2005年 | 254篇 |
2004年 | 230篇 |
2003年 | 204篇 |
2002年 | 217篇 |
2001年 | 197篇 |
2000年 | 134篇 |
1999年 | 190篇 |
1998年 | 149篇 |
1997年 | 109篇 |
1996年 | 118篇 |
1995年 | 109篇 |
1994年 | 118篇 |
1993年 | 81篇 |
1992年 | 59篇 |
1991年 | 41篇 |
1990年 | 37篇 |
1989年 | 38篇 |
1988年 | 24篇 |
1987年 | 22篇 |
1986年 | 17篇 |
1985年 | 25篇 |
1984年 | 29篇 |
1983年 | 9篇 |
1982年 | 20篇 |
1981年 | 34篇 |
1980年 | 21篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1974年 | 9篇 |
1973年 | 7篇 |
排序方式: 共有6951条查询结果,搜索用时 265 毫秒
31.
锰结核中硅,铝,铁,镁,磷,钾,锰,钛的XRFA 总被引:1,自引:0,他引:1
本文叙述了用XRF分析锰结核中Si、Al、Fe、Mg、P、K、Mn和Ti的方法。按照通常锰结核的主次成分制备6个人工合成标准,根据Sherman方程计算了已知成分(二元系统)的相对强度。用L-T方求得了互致元素校正的理论α系数(基本的、混合的、修正的),用DATAFLEX151B计算机以BASIC语言汇了“PRA,APU”计算机程序。然后进行非线性回归分析了锰结核样品得到了满意的结果。 相似文献
32.
Pascal Cherrier 《Bulletin des Sciences Mathématiques》2007,131(4):375-396
We study a parabolic version of a system of Von Karman type on a compact Kähler manifold of arbitrary dimension. We provide local in time regular solutions, which can be extended to global bounded ones if the data of the problem are small. 相似文献
33.
34.
The equivalence of three (2 1)-dimensional soliton equations is proved, and the quite generalsolutionswitha some arbitrary functions of x, t and y respectively are obtained. By selecting the arbitrary functions, many specialtypes of the localized excitations like the solitoff solitons, multi-dromion solutions, lump, and multi-ring soliton solutionsare obtained. 相似文献
35.
Effect of Weakly Transverse Perturbations on Dust Acoustic Solitary Waves with Adiabatic Variation of Dust Charge 总被引:1,自引:0,他引:1
DUAN Wen-Shan 《理论物理通讯》2002,38(12)
By employing the reductive perturbation technique we derived a Kadomtsev-Petviashvili equation forunmagnetized dusty plasmas. It suggests that the nonlinear dust acoustic solitary waves with adiabatic variation of dustcharge are stable even there are some higher order transverse perturbatoins. There are only rarefactive solitary wavesfor this system which has been verified analytically in this paper. 相似文献
36.
LI Cun YANG Bai-Feng CAI Hao HUANG Nian-Ning 《理论物理通讯》2006,46(2):244-248
One of the basic problems about the inverse scattering transform for solving a completely integrable nonlinear evolutions equation is to demonstrate that the Jost solutions obtained from the inverse scattering equations of Cauchy integral satisfy the Lax equations. Such a basic problem still exists in the procedure of deriving the dark soliton solutions of the NLS equation in normal dispersion with non-vanishing boundary conditions through the inverse scattering transform. In this paper, a pair of Jost solutions with same analytic properties are composed to be a 2 × 2 matrix and then another pair are introduced to be its right inverse confirmed by the Liouville theorem. As they are both 2 × 2 matrices, the right inverse should be the left inverse too, based upon which it is not difficult to show that these Jost solutions satisfy both the first and second Lax equations. As a result of compatibility condition, the dark soliton solutions definitely satisfy the NLS equation in normal dispersion with non-vanishing boundary conditions. 相似文献
37.
38.
S. P. Popov 《Computational Mathematics and Mathematical Physics》2006,46(6):983-994
Numerical solutions to three systems of integrable evolutionary equations from the Toda lattice hierarchy are analyzed. These are the classical Toda lattice, the second local dispersive flow, and the second extended dispersive flow. Special attention is given to the properties of soliton solutions. For the equations of the second local flow, two types of solitons interacting in a special manner are found. Solutions corresponding to various initial data are qualitatively outlined. 相似文献
39.
Robert Hochberg 《Combinatorica》2006,26(1):47-64
We prove that the class of homogeneous quasi-arithmetic progressions has unbounded discrepancy. That is, we show that given any 2-coloring of the natural numbers and any positive integer D, one can find a real number α≥1 and a set of natural numbers of the form {0, [α], [2α], [3α], . . . , [kα]} so that one color appears at least D times more than the other color. This was already proved by Beck in 1983, but the proof given here is somewhat simpler and
gives a better bound on the discrepancy. 相似文献
40.
The paper is concerned with a two-delay singular differential system with a twin parameter. Applying fixed-point index theory, we show the relationship between the asymptotic behaviors of nonlinearities (at zero and infinity) and the open regions (eigenvalue regions) of parameters, which are correlated with delays, such that the system has zero, one and two positive solution(s). 相似文献