全文获取类型
收费全文 | 3289篇 |
免费 | 272篇 |
国内免费 | 272篇 |
专业分类
化学 | 231篇 |
晶体学 | 7篇 |
力学 | 130篇 |
综合类 | 80篇 |
数学 | 2662篇 |
物理学 | 723篇 |
出版年
2024年 | 6篇 |
2023年 | 23篇 |
2022年 | 34篇 |
2021年 | 53篇 |
2020年 | 69篇 |
2019年 | 79篇 |
2018年 | 92篇 |
2017年 | 67篇 |
2016年 | 99篇 |
2015年 | 69篇 |
2014年 | 107篇 |
2013年 | 230篇 |
2012年 | 90篇 |
2011年 | 159篇 |
2010年 | 149篇 |
2009年 | 178篇 |
2008年 | 207篇 |
2007年 | 200篇 |
2006年 | 186篇 |
2005年 | 181篇 |
2004年 | 150篇 |
2003年 | 160篇 |
2002年 | 154篇 |
2001年 | 101篇 |
2000年 | 118篇 |
1999年 | 133篇 |
1998年 | 120篇 |
1997年 | 93篇 |
1996年 | 57篇 |
1995年 | 53篇 |
1994年 | 48篇 |
1993年 | 26篇 |
1992年 | 32篇 |
1991年 | 25篇 |
1990年 | 24篇 |
1989年 | 28篇 |
1988年 | 22篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 32篇 |
1984年 | 23篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 10篇 |
1979年 | 18篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 11篇 |
1974年 | 8篇 |
1973年 | 4篇 |
排序方式: 共有3833条查询结果,搜索用时 15 毫秒
991.
Let M be complete nonpositively curved Riemannian manifold of finite volume whose fundamental group Γ does not contain a finite
index subgroup which is a product of infinite groups. We show that the universal cover is a higher rank symmetric space iff is injective (and otherwise the kernel is infinite dimensional). This is the converse of a theorem of Burger–Monod. The proof
uses the celebrated Rank Rigidity Theorem, as well as a new construction of quasi-homomorphisms on groups that act on CAT(0)
spaces and contain rank 1 elements.
Received: September 2007, Accepted: March 2008 相似文献
992.
V. A. Kyrov 《Russian Mathematics (Iz VUZ)》2009,53(7):7-16
In this paper we define a phenomenologically symmetric local Lie group of transformations of an arbitrary-dimensional space. We take as a basis the axiom scheme of the theory of physical structures. Phenomenologically symmetric groups of transformations are nondegenerate both with respect to coordinates and to parameters. We obtain a multipoint invariant of this group of transformations and relate it with Ward quasigroups. We define a substructure of a physical structure as a certain phenomenologically symmetric subgroup of transformations. We establish a criterion for the phenomenological symmetry of the Lie group of transformations and prove the uniqueness of a structure with the minimal rank. We also introduce the notion of a phenomenologically symmetric product of physical structures. 相似文献
993.
O. V. Zakharova 《Russian Mathematics (Iz VUZ)》2009,53(6):1-6
In this paper we prove that instead of solving a class of systems of stochastic differential equations with a multidimensional Wiener process one can solve a system of total differential equations. The latter system admits an application of classical methods. This fact enables one to solve the initial system explicitly. 相似文献
994.
We prove the two existence results of the radially symmetric strong solutions to the Navier- Stokes-Poisson equations for isentropic compressible fluids. The important point in this paper is that the initial density is vacuum. It is different from weak solutions. Now we need some compatibility condition. 相似文献
995.
Maxim Finkelstein 《商业与工业应用随机模型》2009,25(6):643-663
Mixtures of distributions are usually effectively used for modelling heterogeneity. It is well known that mixtures of DFR distributions are always DFR. On the other hand, mixtures of IFR distributions can decrease, at least in some intervals of time. As IFR distributions often model lifetimes governed by ageing processes, the operation of mixing can dramatically change the pattern of ageing. Therefore, the study of the shape of the observed (mixture) failure rate in a heterogeneous setting is important in many applications. We study discrete and continuous mixtures, obtain conditions for the mixture failure rate to tend to the failure rate of the strongest populations and describe asymptotic behaviour as t→∞. Some demographic and engineering examples are considered. The corresponding inverse problem is discussed. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
996.
Bartłomiej Siudeja 《Potential Analysis》2006,25(4):371-386
Let be a symmetric -stable process in , , . We give necessary and sufficient condition under which the expectation of a very general function of the exit time from horns is finite. These domains include the symmetric domains given by increasing functions studied earlier by various authors. Our methods differ from those in earlier papers in that we obtain our results from estimates on the transition densities instead of harmonic measure. Some of this estimates are of independent interest.Supported in part by NSF grant #9700585-DMS and RTN Harmonic Analysis and Related Problems contract HPRN-CT-2001-00273-HARP. 相似文献
997.
I. M. Shchepochkina 《Theoretical and Mathematical Physics》2006,147(3):821-838
We describe an algorithm for embedding a finite-dimensional Lie algebra (superalgebra) into a Lie algebra (superalgebra) of
vector fields that is suitable for a ground field of any characteristic and also a way to select the Cartan, complete, and
partial prolongations of the Lie algebra of vector fields using differential equations. We illustrate the algorithm with the
example of Cartan’s interpretation of the exceptional simple Lie algebra
(2) as the Lie algebra preserving a certain nonintegrable distribution and also several other examples.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 147, No. 3, pp. 450–469, June, 2006. 相似文献
998.
线性流形上对称正交反对称矩阵反问题的最小二乘解 总被引:1,自引:0,他引:1
设P是n阶对称正交矩阵,如果n阶矩阵A满足AT=A和(PA)T=-PA,则称A为对称正交反对称矩阵,所有n阶对称正交反对称矩阵的全体记为SARnp.令S={A∈SARnp f(A)=‖AX-B‖=m in,X,B〗∈Rn×m本文讨论了下面两个问题问题Ⅰ给定C∈Rn×p,D∈Rp×p,求A∈S使得CTAC=D问题Ⅱ已知A~∈Rn×n,求A∧∈SE使得‖A~-A∧‖=m inA∈SE‖A~-A‖其中SE是问题Ⅰ的解集合.文中给出了问题Ⅰ有解的充要条件及其通解表达式.进而,指出了集合SE非空时,问题Ⅱ存在唯一解,并给出了解的表达式,从而得到了求解A∧的数值算法. 相似文献
999.
Mercedes H. Rosas Bruce E. Sagan 《Transactions of the American Mathematical Society》2006,358(1):215-232
Consider the algebra of formal power series in countably many noncommuting variables over the rationals. The subalgebra of symmetric functions in noncommuting variables consists of all elements invariant under permutation of the variables and of bounded degree. We develop a theory of such functions analogous to the ordinary theory of symmetric functions. In particular, we define analogs of the monomial, power sum, elementary, complete homogeneous, and Schur symmetric functions as well as investigating their properties.
1000.
Laiyi Zhu Zhaolin Dong 《分析论及其应用》2006,22(3):262-270
Recently Brutman and Passow considered Newman-type rational interpolation to |x| induced by arbitrary set of symmetric nodes in [-1,1] and gave the general estimation of the approximation error.By their methods one could establish the exact order of approximation for some special nodes. In the present paper we consider the special case where the interpolation nodes are the zeros of the Chebyshev polynomial of the second kind and prove that in this case the exact order of approximation is O(1/n|nn) 相似文献