全文获取类型
收费全文 | 35297篇 |
免费 | 3950篇 |
国内免费 | 4302篇 |
专业分类
化学 | 11614篇 |
晶体学 | 170篇 |
力学 | 3082篇 |
综合类 | 399篇 |
数学 | 15018篇 |
物理学 | 13266篇 |
出版年
2024年 | 95篇 |
2023年 | 333篇 |
2022年 | 689篇 |
2021年 | 761篇 |
2020年 | 978篇 |
2019年 | 964篇 |
2018年 | 954篇 |
2017年 | 1135篇 |
2016年 | 1314篇 |
2015年 | 1086篇 |
2014年 | 1642篇 |
2013年 | 2904篇 |
2012年 | 1835篇 |
2011年 | 2131篇 |
2010年 | 1749篇 |
2009年 | 2339篇 |
2008年 | 2326篇 |
2007年 | 2401篇 |
2006年 | 2043篇 |
2005年 | 1740篇 |
2004年 | 1509篇 |
2003年 | 1517篇 |
2002年 | 1376篇 |
2001年 | 1071篇 |
2000年 | 1102篇 |
1999年 | 967篇 |
1998年 | 861篇 |
1997年 | 693篇 |
1996年 | 511篇 |
1995年 | 449篇 |
1994年 | 397篇 |
1993年 | 371篇 |
1992年 | 340篇 |
1991年 | 274篇 |
1990年 | 294篇 |
1989年 | 252篇 |
1988年 | 230篇 |
1987年 | 223篇 |
1986年 | 180篇 |
1985年 | 197篇 |
1984年 | 172篇 |
1983年 | 106篇 |
1982年 | 150篇 |
1981年 | 146篇 |
1980年 | 111篇 |
1979年 | 115篇 |
1978年 | 103篇 |
1977年 | 91篇 |
1976年 | 81篇 |
1973年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
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
192.
We study the elastic responses of double-(ds) and single-stranded (ss) DNA at external force fields. A double-strand-polymer
elastic model is constructed and solved by path integral methods and Monte Carlo simulations to understand the entropic elasticity,
cooperative extensibility, and supercoiling property of dsDNA. The good agreement with experiments indicates that short-ranged
base-pair stacking interaction is crucial for the stability and the high deformability of dsDNA. Hairpin-coil transition in
ssDNA is studied with generating function method. A threshold force is needed to pull the ssDNA hairpin patterns, stabilized
by base pairing and base-pair stacking, into random coils. This phase transition is predicted to be of first order for stacking
potential higher than some critical level, in accordance with experimental observations. 相似文献
193.
Jean-Pierre Dedieu Gregorio Malajovich Mike Shub 《Foundations of Computational Mathematics》2005,5(2):145-171
We prove a linear bound on the average total curvature of the
central path of linear programming theory in terms of the number
of independent variables of the primal problem, and independent of
the number of constraints. 相似文献
194.
多目标半定规划的互补弱鞍点和G-鞍点最优性条件 总被引:1,自引:0,他引:1
对于含矩阵函数半定约束和多个目标函数的多目标半定规划问题,给出Lagrange函数在弱有效意义下的互补弱鞍点和Geofrrion恰当有效意义下的G-鞍点的定义及其等价定义.然后,在较弱的凸性条件下,利用含矩阵和向量约束的择一性定理,建立多目标半定规划的互补弱鞍点和G-鞍点充分必要条件. 相似文献
195.
Alfonso Carriazo Luis M. Ferná ndez 《Proceedings of the American Mathematical Society》2004,132(11):3327-3336
In this paper we present an interesting relationship between graph theory and differential geometry by defining submanifolds of almost Hermitian manifolds associated with certain kinds of graphs. We show some results about the possibility of a graph being associated with a submanifold and we use them to characterize CR-submanifolds by means of trees. Finally, we characterize submanifolds associated with graphs in a four-dimensional almost Hermitian manifold.
196.
曾六川 《高校应用数学学报(英文版)》2003,18(3):283-286
Let(X,‖·‖ ) be a Banach space.Let K be a nonempty closed,convex subset of Xand T∶K→K.Assume that T is Lipschitzian,i.e.there exists L>0 such that‖ T(x) -T(y)‖≤ L‖ x -y‖for all x,y∈K.Withoutloss of generality,assume that L≥ 1 .Assume also that T is strictly pseudocontractive.According to[1 ] this may be statedas:there exists k∈ (0 ,1 ) such that‖ x -y‖≤‖ x -y + r[(I -T -k I) x -(I -T -k I) y]‖for all r>0 and all x,y∈ K.Throughout,let N denote the set of positive in… 相似文献
197.
Elena Castellani 《International Journal of Theoretical Physics》2004,43(6):1503-1514
We examine the relevance of Dirac's view on the use of transformation theory and invariants in modern physics to current reflections on the meaning of physical symmetries, especially gauge symmetries. 相似文献
198.
199.
We present a general risk model where the aggregate claims, as well as the premium function, evolve by jumps. This is achieved by incorporating a Lévy process into the model. This seeks to account for the discrete nature of claims and asset prices. We give several explicit examples of Lévy processes that can be used to drive a risk model. This allows us to incorporate aggregate claims and premium fluctuations in the same process. We discuss important features of such processes and their relevance to risk modeling. We also extend classical results on ruin probabilities to this model. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
200.
Myron W. Evans 《Foundations of Physics Letters》2003,16(6):513-547
A generally covariant wave equation is derived geometrically for grand unified field theory. The equation states most generally that the covariant d'Alembertian acting on the vielbein vanishes for the four fields which are thought to exist in nature: gravitation, electromagnetism, weak field and strong field. The various known field equations are derived from the wave equation when the vielbein is the eigenfunction. When the wave equation is applied to gravitation the wave equation is the eigenequation of wave mechanics corresponding to Einstein's field equation in classical mechanics, the vielbein eigenfunction playing the role of the quantized gravitational field. The three Newton laws, Newton's law of universal gravitation, and the Poisson equation are recovered in the classical and nonrelativistic, weak-field limits of the quantized gravitational field. The single particle wave-equation and Klein-Gordon equations are recovered in the relativistic, weak-field limit of the wave equation when scalar components are considered of the vielbein eigenfunction of the quantized gravitational field. The Schrödinger equation is recovered in the non-relativistec, weak-field limit of the Klein-Gordon equation). The Dirac equation is recovered in this weak-field limit of the quantized gravitational field (the nonrelativistic limit of the relativistic, quantezed gravitational field when the vielbein plays the role of the spinor. The wave and field equations of O(3) electrodynamics are recovered when the vielbein becomes the relativistic dreibein (triad) eigenfunction whose three orthonormal space indices become identified with the three complex circular indices (1), (2), (3), and whose four spacetime indices are the indices of non-Euclidean spacetime (the base manifold). This dreibein is the potential dreibein of the O(3) electromagnetic field (an electromagnetic potential four-vector for each index (1), (2), (3)). The wave equation of the parity violating weak field is recovered when the orthonormal space indices of the relativistic dreibein eigenfunction are identified with the indices of the three massive weak field bosons. The wave equation of the strong field is recovered when the orthonormal space indices of the relativistic vielbein eigenfunction become the eight indices defined by the group generators of the SU (3) group. 相似文献