全文获取类型
收费全文 | 2451篇 |
免费 | 199篇 |
国内免费 | 181篇 |
专业分类
化学 | 65篇 |
力学 | 152篇 |
综合类 | 30篇 |
数学 | 1039篇 |
物理学 | 177篇 |
综合类 | 1368篇 |
出版年
2024年 | 6篇 |
2023年 | 20篇 |
2022年 | 31篇 |
2021年 | 50篇 |
2020年 | 62篇 |
2019年 | 62篇 |
2018年 | 43篇 |
2017年 | 75篇 |
2016年 | 82篇 |
2015年 | 60篇 |
2014年 | 152篇 |
2013年 | 141篇 |
2012年 | 139篇 |
2011年 | 146篇 |
2010年 | 135篇 |
2009年 | 138篇 |
2008年 | 143篇 |
2007年 | 171篇 |
2006年 | 157篇 |
2005年 | 131篇 |
2004年 | 99篇 |
2003年 | 124篇 |
2002年 | 88篇 |
2001年 | 89篇 |
2000年 | 64篇 |
1999年 | 50篇 |
1998年 | 56篇 |
1997年 | 44篇 |
1996年 | 45篇 |
1995年 | 42篇 |
1994年 | 38篇 |
1993年 | 27篇 |
1992年 | 21篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1955年 | 15篇 |
排序方式: 共有2831条查询结果,搜索用时 31 毫秒
121.
122.
In this paper, we take the parabolic equation with periodic boundary conditions as a model to present a spectral method with the Fourier approximation in spatial and single/multi-interval Legendre Petrov–Galerkin method in time. For the single interval spectral method in time, we obtain the optimal error estimate in L
2-norm. For the multi-interval spectral method in time, the L
2-optimal error estimate is valid in spatial. Numerical results show the efficiency of the methods. 相似文献
123.
孙方裕 《浙江大学学报(理学版)》1996,23(4):293-296
本文我们讨论求凸连续函数的零点的区间割线法 ,所构造的方法简捷、实用 ,且具有较高的收敛效率 (三次函数计值 ,为三阶收敛 ). 相似文献
124.
BIANChunhua NINGXinbao 《科学通报(英文版)》2004,49(5):530-534
A nonlinear autoregressive (NAR) model is built to model the heartbeat interval time series and the optimum model degree is proposed to be taken to evaluate the nonlinearity degree of heart rate variability (HRV). A group of healthy persons are studied and the results indicate that this method can effectively get nonlinear information from short (6—7 min) heartbeat series and consequently reflect the degree of heart rate variability, which supplies convenience in clinical application. Finally, a comparison with the traditional time domain method shows that the NAR model method can reflect the complexity of the whole signal and lessen the influence of noise and instability, in the signal. 相似文献
125.
Safe bounds in linear and mixed-integer linear programming 总被引:1,自引:0,他引:1
Current mixed-integer linear programming solvers are based on linear programming routines that use floating-point arithmetic. Occasionally, this leads to wrong solutions, even for problems where all coefficients and all solution components are small integers. An example is given where many state-of-the-art MILP solvers fail. It is then shown how, using directed rounding and interval arithmetic, cheap pre- and postprocessing of the linear programs arising in a branch-and-cut framework can guarantee that no solution is lost, at least for mixed-integer programs in which all variables can be bounded rigorously by bounds of reasonable size.
Mathematics Subject Classification (2000):primary 90C11, secondary 65G20 相似文献
126.
Continuity of Effect Algebra Operations in the Interval Topology 总被引:1,自引:0,他引:1
We study the continuity of and of effect algebras in the interval topology, and present several examples of effect algebras with interesting properties. 相似文献
127.
We consider smooth multimodal maps which have finitely many non-flat critical points. We prove the existence of real bounds. From this we obtain a new proof for the non-existence of wandering intervals, derive extremely useful improved Koebe principles, show that high iterates have `negative Schwarzian derivative' and give results on ergodic properties of the map. One of the main complications in the proofs is that we allow to have inflection points.
128.
Jacques Peyriere 《分析论及其应用》2003,19(4):332-341
There are mainly two approaches to the multifractal analysis of measures. The first one, which is used in applications and in studying problems arising from dynamical systems, uses a hierarchy of boxes. The second one, which is more satisfactory from the viewpoint of geometric measure theory, uses more intrinsicconcepts. This article is an account of a work by J. Barral, F. Ben Nasr, and J. Peyriere [3] which pro-vides a bridge between these two theories. 相似文献
129.
A poset (X,) is a split interval order (a.k.a. unit bitolerance order, proper bitolerance order) if a real interval and a distinguished point in that interval can be assigned to each xX so that xy precisely when x's distinguished point precedes y's interval, and x's interval precedes y's distinguished point. For each |X|9, we count the split interval orders and identify all posets that are minimal forbidden posets for split interval orders. The paper is a companion to Counting Split Semiorders by Fishburn and Reeds (this issue). 相似文献
130.
Differences of Convex Compact Sets in the Space of Directed Sets. Part I: The Space of Directed Sets
A normed and partially ordered vector space of so-called directed sets is constructed, in which the convex cone of all nonempty convex compact sets in R
n
is embedded by a positively linear, order preserving and isometric embedding (with respect to a new metric stronger than the Hausdorff metric and equivalent to the Demyanov one). This space is a Banach and a Riesz space for all dimensions and a Banach lattice for n=1. The directed sets in R
n
are parametrized by normal directions and defined recursively with respect to the dimension n by the help of a support function and directed supporting faces of lower dimension prescribing the boundary. The operations (addition, subtraction, scalar multiplication) are defined by acting separately on the support function and recursively on the directed supporting faces. Generalized intervals introduced by Kaucher form the basis of this recursive approach. Visualizations of directed sets will be presented in the second part of the paper. 相似文献