全文获取类型
收费全文 | 1211篇 |
免费 | 145篇 |
国内免费 | 131篇 |
专业分类
化学 | 159篇 |
力学 | 81篇 |
综合类 | 31篇 |
数学 | 781篇 |
物理学 | 435篇 |
出版年
2023年 | 14篇 |
2022年 | 34篇 |
2021年 | 35篇 |
2020年 | 37篇 |
2019年 | 34篇 |
2018年 | 49篇 |
2017年 | 40篇 |
2016年 | 34篇 |
2015年 | 26篇 |
2014年 | 43篇 |
2013年 | 119篇 |
2012年 | 45篇 |
2011年 | 73篇 |
2010年 | 50篇 |
2009年 | 71篇 |
2008年 | 63篇 |
2007年 | 65篇 |
2006年 | 77篇 |
2005年 | 54篇 |
2004年 | 61篇 |
2003年 | 68篇 |
2002年 | 50篇 |
2001年 | 52篇 |
2000年 | 43篇 |
1999年 | 46篇 |
1998年 | 45篇 |
1997年 | 27篇 |
1996年 | 23篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 17篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1982年 | 5篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有1487条查询结果,搜索用时 31 毫秒
101.
We generalize the basic quasifibration theorem of Dold and Thom (1958), replacing quasifibrations by weak equivalences. 相似文献
102.
Hyun Ho Lee 《Journal of Functional Analysis》2011,260(1):135-145
In this paper we generalize the notion of essential codimension of Brown, Douglas, and Fillmore using KK-theory and prove a result which asserts that there is a unitary of the form ‘identity + compact’ which gives the unitary equivalence of two projections if the ‘essential codimension’ of two projections vanishes for certain C∗-algebras employing the proper asymptotic unitary equivalence of KK-theory found by M. Dadarlat and S. Eilers. We also apply our result to study the projections in the corona algebra of C(X)⊗B where X is [0,1], (−∞,∞), [0,∞), and [0,1]/{0,1}. 相似文献
103.
We introduce the notion of sofic measurable equivalence relations. Using them we prove that Connes' Embedding Conjecture as well as the Measurable Determinant Conjecture of Lück, Sauer and Wegner hold for treeable equivalence relations. 相似文献
104.
The Kuramoto–Sivashinsky equation plays an important role as a low‐dimensional prototype for complicated fluid dynamics systems having been studied due to its chaotic pattern forming behavior. Up to now, efforts to carry out data assimilation with this 1‐D model were restricted to variational adjoint methods domain and only Chorin and Krause (Proc. Natl. Acad. Sci. 2004; 101 (42):15013–15017) tested it using a sequential Bayesian filter approach. In this work we compare three sequential data assimilation methods namely the Kalman filter approach, the sequential Monte Carlo particle filter approach and the maximum likelihood ensemble filter methods. This comparison is to the best of our knowledge novel. We compare in detail their relative performance for both linear and nonlinear observation operators. The results of these sequential data assimilation tests are discussed and conclusions are drawn as to the suitability of these data assimilation methods in the presence of linear and nonlinear observation operators. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
105.
Under weak constraints on the positive functions to be compared, we derive their asymptotic equivalence at infinity as a consequence of the asymptotic equivalence of their Stieltjes transforms at infinity. 相似文献
106.
M. Ledoux 《Journal of statistical physics》2000,100(5-6):871-892
This paper describes some of the analytic tools developed recently by Ghirlanda and Guerra in the investigation of the distribution of overlaps in the Sherrington–Kirkpatrick spin glass model and of Parisi's ultrametricity. In particular, we introduce to this task a simplified (but also generalized) model on which the Gaussian analysis is made easier. Moments of the Hamiltonian and derivatives of the free energy are expressed as polynomials of the overlaps. Under the essential tool of self-averaging, we describe with full rigour, various overlap identities and replica independence that actually hold in a rather large generality. The results are presented in a language accessible to probabilists and analysts. 相似文献
107.
M. E. Fels 《Transactions of the American Mathematical Society》1996,348(12):5007-5029
A simple invariant characterization of the scalar fourth-order ordinary differential equations which admit a variational multiplier is given. The necessary and sufficient conditions for the existence of a multiplier are expressed in terms of the vanishing of two relative invariants which can be associated with any fourth-order equation through the application of Cartan's equivalence method. The solution to the inverse problem for fourth-order scalar equations provides the solution to an equivalence problem for second-order Lagrangians, as well as the precise relationship between the symmetry algebra of a variational equation and the divergence symmetry algebra of the associated Lagrangian.
108.
Martin Raussen 《Applied Categorical Structures》2007,15(4):355-386
Directed spaces are the objects of study within directed algebraic topology. They are characterised by spaces of directed
paths associated to a source and a target, both elements of an underlying topological space. The algebraic topology of these
path spaces and their connections are studied from a categorical perspective. In particular, we study the preorder category
associated to a directed space and various “quotient” categories arising from algebraic topological functors. Furthermore,
we propose and study a new notion of directed homotopy equivalence between directed spaces.
相似文献
109.
Sergio Benenti 《Acta Appl Math》2005,87(1-3):33-91
A general analysis of special classes of symmetric two-tensor on Riemannian manifolds is provided. These tensors arise in connection with special topics in differential geometry and analytical mechanics: geodesic equivalence and separation of variables. It is shown that they play an important role in the theory of correspondent (or equivalent) dynamical systems of Levi-Civita. By applying some new developments of this theory, it is shown that the recent notions of cofactor and cofactor-pair systems arise in a natural way, as non-Lagrangian systems having a Lagrangian equivalent. This circumstance extends the Hamiltonian methods, including the separation of variables of the Hamilton–Jacobi equation, to a special class of nonconservative systems. In this extension the case of indefinite metrics, may occur. Hence, it is shown that also pseudo-Riemannian geometry plays an important role also in classical mechanics.Research sponsored by the Dept. of Mathematics, University of Turin, and by INDAM-GNFM. 相似文献
110.
F. Fang 《Commentarii Mathematici Helvetici》1997,72(3):466-480
Let X
n
(d) and X
n
(d') be two n-dimensional complete intersections with the same total degree d. In this paper we prove that, if n is even and d has no prime factors less than , then X
n
(d) and X
n
(d') are homotopy equivalent if and only if they have the same Euler characteristics and signatures. This confirms a conjecture
of Libgober and Wood [16]. Furthermore, we prove that, if d has no prime factors less than , then X
n
(d) and X
n
(d') are homeomorphic if and only if their Pontryagin classes and Euler characteristics agree.
Received: September 6, 1996 相似文献