全文获取类型
收费全文 | 21494篇 |
免费 | 3585篇 |
国内免费 | 1782篇 |
专业分类
化学 | 4498篇 |
晶体学 | 56篇 |
力学 | 2807篇 |
综合类 | 570篇 |
数学 | 10516篇 |
物理学 | 8414篇 |
出版年
2024年 | 32篇 |
2023年 | 214篇 |
2022年 | 379篇 |
2021年 | 529篇 |
2020年 | 540篇 |
2019年 | 497篇 |
2018年 | 499篇 |
2017年 | 753篇 |
2016年 | 856篇 |
2015年 | 695篇 |
2014年 | 1177篇 |
2013年 | 1485篇 |
2012年 | 1176篇 |
2011年 | 1354篇 |
2010年 | 1205篇 |
2009年 | 1369篇 |
2008年 | 1529篇 |
2007年 | 1596篇 |
2006年 | 1314篇 |
2005年 | 1194篇 |
2004年 | 1136篇 |
2003年 | 944篇 |
2002年 | 913篇 |
2001年 | 748篇 |
2000年 | 644篇 |
1999年 | 624篇 |
1998年 | 534篇 |
1997年 | 462篇 |
1996年 | 400篇 |
1995年 | 397篇 |
1994年 | 256篇 |
1993年 | 227篇 |
1992年 | 169篇 |
1991年 | 201篇 |
1990年 | 130篇 |
1989年 | 84篇 |
1988年 | 113篇 |
1987年 | 75篇 |
1986年 | 61篇 |
1985年 | 67篇 |
1984年 | 51篇 |
1983年 | 33篇 |
1982年 | 34篇 |
1981年 | 38篇 |
1980年 | 29篇 |
1979年 | 29篇 |
1978年 | 17篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
201.
研究一类脉冲时滞抛物型偏微分方程组解的振动性,利用一阶脉冲时滞微分不等式获得了该类方程组在两类不同边值条件下所有解振动的若干充分条件.所得结果充分反映了脉冲和时滞在振动中的影响作用. 相似文献
202.
Ji-pu Ma Tseng Yaun Rong Functional Analysis Research Center Harbin Normal University Harbin China 《中国科学A辑(英文版)》2007,50(9):1233-1239
Let E, F be two Banach spaces, and B(E, F), Φ(E, F), SΦ(E, F) and R(E,F) be the bounded linear, Fredholm, semi-Frdholm and finite rank operators from E into F, respectively. In this paper, using the continuity characteristics of generalized inverses of operators under small perturbations, we prove the following result Let ∑ be any one of the following sets {T ∈ Φ(E, F) IndexT =const, and dim N(T) = const.}, {T ∈ SΦ(E, F) either dim N(T) = const. < ∞ or codim R(T) = const.< ∞} and {T ∈ R(E, F) RankT =const.<∞}. Then ∑ is a smooth submanifold of B(E, F) with the tangent space TA∑ = {B ∈ B(E,F) BN(A) (∪) R(A)} for any A ∈ ∑. The result is available for the further application to Thom's famous results on the transversility and the study of the infinite dimensional geometry. 相似文献
203.
Global existence and blow-up of solutions to a parabolic system with nonlocal sources and boundaries 总被引:2,自引:0,他引:2
Ling-hua KONG~ 《中国科学A辑(英文版)》2007,50(9):1251-1266
This paper deals with a semi-linear parabolic system with nonlinear nonlocal sources and nonlocal boundaries.By using super-and sub-solution techniques,we first give the sufficient conditions that the classical solution exists globally and blows up in a finite time respectively,and then give the necessary and sufficient conditions that two components u and v blow up simultaneously.Finally,the uniform blow-up profiles in the interior are presented. 相似文献
204.
Elie Leopold 《Numerical Algorithms》2007,44(4):347-366
In this paper, we give some new explicit relations between two families of polynomials defined by recurrence relations of
all order. These relations allow us to analyze, even in the Sobolev case, how some properties of a family of orthogonal polynomials
are affected when the coefficients of the recurrence relation and the order are perturbed. In a paper we have already given
a method which allows us to study the polynomials defined by a three-term recurrence relation. Also here some generalizations
are given. 相似文献
205.
《Journal of Differential Equations》2003,190(2):663-685
The existence of global smooth solutions to the multi-dimensional hydrodynamic model for plasmas of electrons and positively charged ions is shown under the assumption that the initial densities are close to a constant. The model consists of the conservation laws for the particle densities and the current densities, coupled to the Poisson equation for the electrostatic potential. Furthermore, it is proved that the particle densities converge exponentially fast to the (constant) steady state. The proof uses a higher-order energy method inspired from extended thermodynamics. 相似文献
206.
本文研究了具有中心环域的可积多项式系统,探讨此系统在用多项式进行微扰的情况下,其所对应的Abel积分的零点个数的计算方法,给出了一个较为实用的定理,并举出了若干个应用的例子. 相似文献
207.
Hailiang Liu 《Journal of Differential Equations》2003,192(2):285-307
This paper studies the asymptotic stability of traveling relaxation shock profiles for hyperbolic systems of conservation laws. Under a stability condition of subcharacteristic type the large time relaxation dynamics on the level of shocks is shown to be determined by the equilibrium conservation laws. The proof is due to the energy principle, using the weighted norms, the interaction of waves from various modes is treated by imposing suitable weight matrix. 相似文献
208.
物理实验课程考核、评估体系初探 总被引:4,自引:0,他引:4
对物理实验课程考核、评估方法进行了探讨,提出了物理实验课程考核、评估体系及实施细则.重点介绍了体系中的核心部分——正规的物理实验课程考试. 相似文献
209.
Ding-kang WANG~ Yan ZHANG Key Laboratory of Mathematics Mechanization Academy of Mathematics Systems Science Chinese Academy of Sciences Beijing China 《中国科学A辑(英文版)》2007,50(10):1441-1450
We present an algorithm to decompose a polynomial system into a finite set of normal ascending sets such that the set of the zeros of the polynomial system is the union of the sets of the regular zeros of the normal ascending sets.If the polynomial system is zero dimensional,the set of the zeros of the polynomials is the union of the sets of the zeros of the normal ascending sets. 相似文献
210.
We propose objectives consisting of two mirrors with central holes for passage of a light beam. The optical layout ensures
multiple reflection of rays from both mirrors. We consider several approaches to calculating the design parameters for which
three and four aberrations do not occur. The objectives can be used in optical devices operating in the UV and IR regions
of the spectrum.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 267–270, March–April, 2007. 相似文献