全文获取类型
收费全文 | 4007篇 |
免费 | 524篇 |
国内免费 | 365篇 |
专业分类
化学 | 167篇 |
晶体学 | 1篇 |
力学 | 553篇 |
综合类 | 92篇 |
数学 | 3071篇 |
物理学 | 1012篇 |
出版年
2024年 | 6篇 |
2023年 | 44篇 |
2022年 | 68篇 |
2021年 | 82篇 |
2020年 | 93篇 |
2019年 | 121篇 |
2018年 | 112篇 |
2017年 | 110篇 |
2016年 | 139篇 |
2015年 | 102篇 |
2014年 | 159篇 |
2013年 | 417篇 |
2012年 | 170篇 |
2011年 | 202篇 |
2010年 | 180篇 |
2009年 | 225篇 |
2008年 | 275篇 |
2007年 | 248篇 |
2006年 | 262篇 |
2005年 | 227篇 |
2004年 | 177篇 |
2003年 | 195篇 |
2002年 | 182篇 |
2001年 | 151篇 |
2000年 | 149篇 |
1999年 | 132篇 |
1998年 | 130篇 |
1997年 | 90篇 |
1996年 | 71篇 |
1995年 | 72篇 |
1994年 | 41篇 |
1993年 | 24篇 |
1992年 | 29篇 |
1991年 | 30篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1959年 | 2篇 |
排序方式: 共有4896条查询结果,搜索用时 234 毫秒
1.
2.
In this paper, we investigate the evolution of joint invariants under invariant geometric flows using the theory of equivariant moving frames and the induced invariant discrete variational complex. For certain arc length preserving planar curve flows invariant under the special Euclidean group , the special linear group , and the semidirect group , we find that the induced evolution of the discrete curvature satisfies the differential‐difference mKdV, KdV, and Burgers' equations, respectively. These three equations are completely integrable, and we show that a recursion operator can be constructed by precomposing the characteristic operator of the curvature by a certain invariant difference operator. Finally, we derive the constraint for the integrability of the discrete curvature evolution to lift to the evolution of the discrete curve itself. 相似文献
3.
4.
5.
设R是环,M是R-拟连续左R-模.如果R关于形如l(m),m∈M的左理想满足升链条件,则M可写成一致子模的直和. 相似文献
6.
R. S. Martynov Yu. M. Nechepurenko 《Computational Mathematics and Mathematical Physics》2006,46(7):1155-1167
For a discrete linear stochastic dynamical system, computation of the response matrix to the external action from a subspace using given observational data is examined. An algorithm is proposed and substantiated that makes it possible to improve the numerical accuracy and to reduce the amount of observational data compared to the general case where an arbitrary external action is allowed. As an illustration, a discrete system arising in the analysis of a linear stochastic dynamical continuous-time system is considered more thoroughly. Some numerical results are presented. 相似文献
7.
8.
Teresa Regińska 《BIT Numerical Mathematics》2004,44(1):119-133
The paper concerns conditioning aspects of finite-dimensional problems arising when the Tikhonov regularization is applied
to discrete ill-posed problems. A relation between the regularization parameter and the sensitivity of the regularized solution
is investigated. The main conclusion is that the condition number can be decreased only to the square root of that for the
nonregularized problem. The convergence of solutions of regularized discrete problems to the exact generalized solution is
analyzed just in the case when the regularization corresponds to the minimal condition number. The convergence theorem is
proved under the assumption of the suitable relation between the discretization level and the data error. As an example the
method of truncated singular value decomposition with regularization is considered.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
10.
A theorem of Birkhoff‐Frink asserts that every algebraic closure operator on an ordinary set arises, from some algebraic structure on the set, as the corresponding generated subalgebra operator. However, for many‐sorted sets, i.e., indexed families of sets, such a theorem is not longer true without qualification. We characterize the corresponding many‐sorted closure operators as precisely the uniform algebraic operators. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献