全文获取类型
收费全文 | 16527篇 |
免费 | 1584篇 |
国内免费 | 2196篇 |
专业分类
化学 | 3460篇 |
晶体学 | 88篇 |
力学 | 887篇 |
综合类 | 400篇 |
数学 | 11593篇 |
物理学 | 3879篇 |
出版年
2024年 | 15篇 |
2023年 | 177篇 |
2022年 | 180篇 |
2021年 | 287篇 |
2020年 | 356篇 |
2019年 | 402篇 |
2018年 | 375篇 |
2017年 | 440篇 |
2016年 | 490篇 |
2015年 | 380篇 |
2014年 | 731篇 |
2013年 | 1089篇 |
2012年 | 745篇 |
2011年 | 945篇 |
2010年 | 861篇 |
2009年 | 1127篇 |
2008年 | 1226篇 |
2007年 | 1334篇 |
2006年 | 1057篇 |
2005年 | 999篇 |
2004年 | 787篇 |
2003年 | 848篇 |
2002年 | 715篇 |
2001年 | 602篇 |
2000年 | 632篇 |
1999年 | 584篇 |
1998年 | 530篇 |
1997年 | 449篇 |
1996年 | 340篇 |
1995年 | 233篇 |
1994年 | 237篇 |
1993年 | 141篇 |
1992年 | 141篇 |
1991年 | 126篇 |
1990年 | 97篇 |
1989年 | 82篇 |
1988年 | 75篇 |
1987年 | 50篇 |
1986年 | 51篇 |
1985年 | 59篇 |
1984年 | 52篇 |
1983年 | 24篇 |
1982年 | 47篇 |
1981年 | 33篇 |
1980年 | 31篇 |
1979年 | 30篇 |
1978年 | 19篇 |
1977年 | 19篇 |
1976年 | 17篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
111.
Some curvature conditions about the geodesics emanating from a submanifold are obtained. These conditions are used to to study the topological and geometric properties of the ambient spaces which admit some minimal submanifolds. 相似文献
112.
113.
We prove equivalence of the definitions by the author and by Korevaar and Schoen of the Sobolev classes of mappings of a domain of an arithmetic n-dimensional space to a metric space. 相似文献
114.
Pedro Ontaneda 《Geometriae Dedicata》2004,104(1):25-35
We study the following question: does a compact nonpositively curved space have a totally geodesic core? 相似文献
115.
T. Domínguez Benavides 《Journal of Mathematical Analysis and Applications》2004,291(1):100-108
Let X be a Banach space whose characteristic of noncompact convexity is less than 1 and satisfies the nonstrict Opial condition. Let C be a bounded closed convex subset of X, KC(X) the family of all compact convex subsets of X and T a nonexpansive mapping from C into KC(X) with bounded range. We prove that T has a fixed point. The nonstrict Opial condition can be removed if, in addition, T is an 1-χ-contractive mapping. 相似文献
116.
活动标形法的论述首推苏步青译,佐佐木重夫著《微分几何学》,还有的著作从外微分形式引入活动标形,本文论证取曲面的正交曲率网为参数网时,曲面论的基本公式就是活动标形的微分形式,并用其分析了点啮合齿轮传动误差. 相似文献
117.
On Covariant Phase Space and the Variational Bicomplex 总被引:1,自引:0,他引:1
Enrique G. Reyes 《International Journal of Theoretical Physics》2004,43(5):1267-1286
The notion of a phase space in classical mechanics is well known. The extension of this concept to field theory however, is a challenging endeavor, and over the years numerous proposals for such a generalization have appeared in the literature. In this paper We review a Hamiltonian formulation of Lagrangian field theory based on an extension to infinite dimensions of J.-M. Souriau's symplectic approach to mechanics. Following G. Zuckerman, we state our results in terms of the modern geometric theory of differential equations and the variational bicomplex. As an elementary example, we construct a phase space for the Monge–Ampere equation. 相似文献
118.
The authors give the necessary and sufficient conditions for a generalized circle in a Weyl hypersurface to be generalized circle in the enveloping Weyl space. They then obtain the neccessary and sufficient conditions under which a generalized concircular transformation of one Weyl space onto another induces a generalized transformation oil its subspaces. Finally, it is shown that any totally geodesic or totally umbilical hypersurface of a generalized concircularly flat Weyl space is also generalized concircularly flat. 相似文献
119.
Ghulam Mustafa 《数学研究及应用》2003,23(3):413-421
本文引入了一种满足更一般的收缩不等式的多重函数类,并证明了属于该类的可测多重函数对的一些随机重合点定理。 相似文献
120.
Preconditioners based on various multilevel extensions of two‐level finite element methods (FEM) lead to iterative methods which have an optimal order computational complexity with respect to the size of the system. Such methods were first presented in Axelsson and Padiy (SIAM. J. Sci. Stat. Comp. 1990; 20 :1807) and Axelsson and Vassilevski (Numer. Math. 1989; 56 :157), and are based on (recursive) two‐level splittings of the finite element space. The key role in the derivation of optimal convergence rate estimates is played by the constant γ in the so‐called Cauchy–Bunyakowski–Schwarz (CBS) inequality, associated with the angle between the two subspaces of the splitting. It turns out that only existence of uniform estimates for this constant is not enough but accurate quantitative bounds for γ have to be found as well. More precisely, the value of the upper bound for γ∈(0,1) is part of the construction of various multilevel extensions of the related two‐level methods. In this paper, an algebraic two‐level preconditioning algorithm for second‐order elliptic boundary value problems is constructed, where the discretization is done using Crouzeix–Raviart non‐conforming linear finite elements on triangles. An important point to make is that in this case the finite element spaces corresponding to two successive levels of mesh refinements are not nested. To handle this, a proper two‐level basis is considered, which enables us to fit the general framework for the construction of two‐level preconditioners for conforming finite elements and to generalize the method to the multilevel case. The major contribution of this paper is the derived estimates of the related constant γ in the strengthened CBS inequality. These estimates are uniform with respect to both coefficient and mesh anisotropy. To our knowledge, the results presented in the paper are the first such estimates for non‐conforming FEM systems. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献