全文获取类型
收费全文 | 97822篇 |
免费 | 10021篇 |
国内免费 | 7351篇 |
专业分类
化学 | 45335篇 |
晶体学 | 1267篇 |
力学 | 13684篇 |
综合类 | 1525篇 |
数学 | 27357篇 |
物理学 | 26026篇 |
出版年
2024年 | 142篇 |
2023年 | 854篇 |
2022年 | 1441篇 |
2021年 | 3025篇 |
2020年 | 2762篇 |
2019年 | 2371篇 |
2018年 | 2150篇 |
2017年 | 2762篇 |
2016年 | 3452篇 |
2015年 | 3044篇 |
2014年 | 4356篇 |
2013年 | 6476篇 |
2012年 | 5171篇 |
2011年 | 5623篇 |
2010年 | 4926篇 |
2009年 | 5914篇 |
2008年 | 5934篇 |
2007年 | 6138篇 |
2006年 | 5258篇 |
2005年 | 4338篇 |
2004年 | 3879篇 |
2003年 | 3663篇 |
2002年 | 5814篇 |
2001年 | 3107篇 |
2000年 | 2553篇 |
1999年 | 2286篇 |
1998年 | 2135篇 |
1997年 | 1713篇 |
1996年 | 1577篇 |
1995年 | 1408篇 |
1994年 | 1264篇 |
1993年 | 1129篇 |
1992年 | 1078篇 |
1991年 | 760篇 |
1990年 | 639篇 |
1989年 | 483篇 |
1988年 | 449篇 |
1987年 | 367篇 |
1986年 | 334篇 |
1985年 | 484篇 |
1984年 | 383篇 |
1983年 | 208篇 |
1982年 | 389篇 |
1981年 | 526篇 |
1980年 | 462篇 |
1979年 | 529篇 |
1978年 | 405篇 |
1977年 | 325篇 |
1976年 | 260篇 |
1973年 | 155篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
991.
992.
In the present paper,we investigate the well-posedness of the global solution for the Cauchy problem of generalized long-short wave equations.Applying Kato's method for abstract quasi-linear evolution equations and a priori estimates of solution,we get the existence of globally smooth solution. 相似文献
993.
Jun Hu Zhong-Ci Shi 《计算数学(英文版)》2006,24(1):1-8
We consider the quadrilateral Q1 isoparametric element and establish an optimal error estimate in H^1 norm for the interpolation operator under a weaker mesh condition which admits anisotropic quadrilaterals and allows the quadrilateral to become a regular triangle in the sense of maximum angle condition [5, 11]. 相似文献
994.
O. A. Brezhneva Yu. G. Evtushenko A. A. Tret’yakov 《Computational Mathematics and Mathematical Physics》2006,46(11):1896-1909
The theory of p-regularity is applied to optimization problems and to singular ordinary differential equations (ODE). The special variant of the method of the modified Lagrangian function proposed by Yu.G. Evtushenko for constrained optimization problems with inequality constraints is justified on the basis of the 2-factor transformation. An implicit function theorem is given for the singular case. This theorem is used to show the existence of solutions to a boundary value problem for a nonlinear differential equation in the resonance case. New numerical methods are proposed including the p-factor method for solving ODEs with a small parameter. 相似文献
995.
996.
1引言对于二阶常微分方程的初值问题y″=g(x,y),y(x_0)=y_0,y′(x_0)=y_0′,x_0(?)x(?)T(1)的数值解法的研究引起人们的广泛兴趣.对于直接积分(1),自从1976年J.D.Lambert和I.A.Waston提出二阶P-稳定方法和1978年G.Dahlquist证明P-稳定常系数线性多步方法的最高相容阶不超过2的重要结论以来,截止目前,已积累了许多高于2阶的P-稳定方法.例如,修正的Numerov方法,混合法(特殊形式RK的方法),多导法,Obrechkoff方法,显式RKN方法,单隐方法和对角隐式RKN方法等(顺便指出,文献[5,16]中所说的高阶方法的相容阶均不超过4).所有这些方法,有些相 相似文献
997.
王健 《新疆大学学报(理工版)》2002,19(1):108-109
使用计算机进行结构设计虽然能大大减轻计算工作量,但不能取代人的设计概念,只有在设计人员具备较全面的设计概念;有一定设计经验;同时深入了解程度的情况下,才能确保工程设计的质量。 相似文献
998.
A linear three‐dimensional hydrodynamical numerical model, with the application of the Galerkin Method for the vertical dependence, is here presented. The spherical coordinate system is used, in order to allow large‐scale simulations. The equations and mathematical development of the model are shown in detail, together with the boundary and initial conditions, and the sequence of equations' solution. The model is applied to the South Atlantic Ocean, for estimating typical seasonal circulations, and the results are summarized in maps of currents at surface and 1000 m depth, and in transport values of the Brazil Current between 30°S and 40°S. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
999.
Unconventional antiferromagnetic correlations of the doped Haldane gapsystem Y 2 BaNi 1 - x Zn x O 5
V. Villar R. Mélin C. Paulsen J. Souletie E. Janod C. Payen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(1):39-51
We make a new proposal to describe the very low temperature susceptibility of the doped Haldane gap compound Y2BaNi1-xZnxO5. We propose a new mean field model relevant for this compound. The ground state of this mean field model is unconventional
because antiferromagnetism coexists with random dimers. We present new susceptibility experiments at very low temperature.
We obtain a Curie-Weiss susceptibility χ(
T
) ∼
C
/(Θ +
T
) as expected for antiferromagnetic correlations but we do not obtain a direct signature of antiferromagnetic long range order.
We explain how to obtain the “impurity” susceptibility
(
T
) by subtracting the Haldane gap contribution to the total susceptibility. In the temperature range [1 K, 300 K] the experimental
data are well fitted by T
(
T
) =
C
imp
1 +
T
imp
/
T
. In the temperature range [100 mK, 1 K] the experimental data are well fitted by T
(
T
) =
A
ln(
T
/
T
c
), where T
c
increases with x. This fit suggests the existence of a finite Néel temperature which is however too small to be probed directly in our experiments.
We also obtain a maximum in the temperature dependence of the ac-susceptibility
(
T
) which suggests the existence of antiferromagnetic correlations at very low temperature.
Received 17 July 2001 相似文献
1000.
H.O.U. Fynbo Y. Prezado J. Äystö U.C. Bergmann M.J.G. Borge P. Dendooven W. Huang J. Huikari H. Jeppesen P. Jones B. Jonson M. Meister G. Nyman M. Oinonen K. Riisager O. Tengblad I.S. Vogelius Y. Wang L. Weissman K.W. Rolander 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):135-138