全文获取类型
收费全文 | 30001篇 |
免费 | 3268篇 |
国内免费 | 1801篇 |
专业分类
化学 | 3665篇 |
晶体学 | 16篇 |
力学 | 3176篇 |
综合类 | 323篇 |
数学 | 19682篇 |
物理学 | 8208篇 |
出版年
2023年 | 292篇 |
2022年 | 332篇 |
2021年 | 431篇 |
2020年 | 849篇 |
2019年 | 849篇 |
2018年 | 798篇 |
2017年 | 717篇 |
2016年 | 811篇 |
2015年 | 684篇 |
2014年 | 1253篇 |
2013年 | 2489篇 |
2012年 | 1320篇 |
2011年 | 1683篇 |
2010年 | 1626篇 |
2009年 | 1793篇 |
2008年 | 1893篇 |
2007年 | 1851篇 |
2006年 | 1557篇 |
2005年 | 1574篇 |
2004年 | 1296篇 |
2003年 | 1238篇 |
2002年 | 1101篇 |
2001年 | 834篇 |
2000年 | 799篇 |
1999年 | 752篇 |
1998年 | 706篇 |
1997年 | 584篇 |
1996年 | 450篇 |
1995年 | 372篇 |
1994年 | 314篇 |
1993年 | 204篇 |
1992年 | 198篇 |
1991年 | 207篇 |
1990年 | 177篇 |
1989年 | 98篇 |
1988年 | 102篇 |
1987年 | 99篇 |
1986年 | 99篇 |
1985年 | 100篇 |
1984年 | 90篇 |
1982年 | 124篇 |
1981年 | 317篇 |
1980年 | 304篇 |
1979年 | 282篇 |
1978年 | 316篇 |
1977年 | 253篇 |
1976年 | 264篇 |
1974年 | 71篇 |
1973年 | 187篇 |
1972年 | 118篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
基于MATLAB的异步电动机线性化控制系统的仿真 总被引:1,自引:0,他引:1
从异步电动机在同步旋转坐标系下的状态方程出发,在一定的条件下,对其系数矩阵简化.推出异步电动机的线性化控制模型.并基于该模型得出异步电动机的线性化控制系统.以给定电机为例,对该模型的有效性、响应用MATLAB进行仿真分析.验证的结果说明上述模型具有实用价值. 相似文献
43.
Anna L. Mazzucato 《Transactions of the American Mathematical Society》2003,355(4):1297-1364
This paper is devoted to the analysis of function spaces modeled on Besov spaces and their applications to non-linear partial differential equations, with emphasis on the incompressible, isotropic Navier-Stokes system and semi-linear heat equations. Specifically, we consider the class, introduced by Hideo Kozono and Masao Yamazaki, of Besov spaces based on Morrey spaces, which we call Besov-Morrey or BM spaces. We obtain equivalent representations in terms of the Weierstrass semigroup and wavelets, and various embeddings in classical spaces. We then establish pseudo-differential and para-differential estimates. Our results cover non-regular and exotic symbols. Although the heat semigroup is not strongly continuous on Morrey spaces, we show that its action defines an equivalent norm. In particular, homogeneous BM spaces belong to a larger class constructed by Grzegorz Karch to analyze scaling in parabolic equations. We compare Karch's results with those of Kozono and Yamazaki and generalize them by obtaining short-time existence and uniqueness of solutions for arbitrary data with subcritical regularity. We exploit pseudo-differential calculus to extend the analysis to compact, smooth, boundaryless, Riemannian manifolds. BM spaces are defined by means of partitions of unity and coordinate patches, and intrinsically in terms of functions of the Laplace operator.
44.
Guy Bayada 《Journal of Mathematical Analysis and Applications》2003,282(1):212-231
The asymptotic behaviour of a Stokes flow with Tresca free boundary friction conditions when one dimension of the fluid domain tends to zero is studied. A specific Reynolds equation associated with variational inequalities is obtained and uniqueness is proved. 相似文献
45.
Karl Gustafson 《Numerical Linear Algebra with Applications》2004,11(7):649-659
Given the operator product BA in which both A and B are symmetric positive‐definite operators, for which symmetric positive‐definite operators C is BA symmetric positive‐definite in the C inner product 〈x, y〉C? This question arises naturally in preconditioned iterative solution methods, and will be answered completely here. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
46.
ZHANG LUMING 《应用数学学报》2005,(1)
本文首先分析线性Schrodinger方程一种高阶差分格式的构造方法,得到方程的耗散项.在此基础上对三次非线性Schrodinger方程,提出了一种精度为O(r2 h2)的差分格式,证明了该格式保持了连续方程的两个守恒量,且是收敛的与稳定的.并通过数值例子与已有隐格式进行了比较,结果表明,本文格式在计算量类似的情况下,提高了数值精度. 相似文献
47.
给出了Banach空间的一个增算子不动点定理,将这一定理应用到Banach空间的积分-微分方程,给出了一类积分-微分方程的连续可微最大解和连续可微最小解的存在性定理. 相似文献
48.
49.
Anatoliy Samoilenko Manuel Pinto Sergei Trofimchuk 《Proceedings of the American Mathematical Society》2005,133(1):145-154
We apply the Krylov and Bogolyubov asymptotic integration procedure to asymptotically autonomous systems. First, we consider linear systems with quasi-periodic coefficient matrix multiplied by a scalar factor vanishing at infinity. Next, we study the asymptotically autonomous Van-der-Pol oscillator.
50.
This paper presents an evaluation of the capability of turbulence models available in the commercial CFD code FLUENT 6.0 for their application to hydrofoil turbulent boundary layer separation flow at high Reynolds numbers. Four widely applied two‐equation RANS turbulence models were assessed through comparison with experimental data at Reynolds numbers of 8.284×106 and 1.657×107. They were the standard k–εmodel, the realizable k–εmodel, the standard k–ωmodel and the shear‐stress‐transport (SST) k–ωmodel. It has found that the realizable k–εturbulence model used with enhanced wall functions and near‐wall modelling techniques, consistently provides superior performance in predicting the flow characteristics around the hydrofoil. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献