全文获取类型
收费全文 | 2562篇 |
免费 | 299篇 |
国内免费 | 843篇 |
专业分类
化学 | 6篇 |
力学 | 94篇 |
综合类 | 6篇 |
数学 | 3500篇 |
物理学 | 98篇 |
出版年
2018年 | 10篇 |
2017年 | 21篇 |
2016年 | 17篇 |
2015年 | 26篇 |
2014年 | 48篇 |
2013年 | 81篇 |
2012年 | 99篇 |
2011年 | 154篇 |
2010年 | 122篇 |
2009年 | 83篇 |
2008年 | 82篇 |
2007年 | 222篇 |
2006年 | 282篇 |
2005年 | 248篇 |
2004年 | 190篇 |
2003年 | 189篇 |
2002年 | 165篇 |
2001年 | 137篇 |
2000年 | 162篇 |
1999年 | 138篇 |
1998年 | 92篇 |
1997年 | 98篇 |
1996年 | 97篇 |
1995年 | 114篇 |
1994年 | 83篇 |
1993年 | 90篇 |
1992年 | 68篇 |
1991年 | 65篇 |
1990年 | 40篇 |
1989年 | 28篇 |
1988年 | 17篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1978年 | 17篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 12篇 |
1972年 | 9篇 |
1967年 | 32篇 |
1966年 | 16篇 |
1965年 | 30篇 |
1964年 | 29篇 |
1963年 | 13篇 |
1962年 | 30篇 |
1961年 | 15篇 |
1960年 | 17篇 |
1959年 | 19篇 |
1958年 | 15篇 |
1957年 | 10篇 |
排序方式: 共有3704条查询结果,搜索用时 15 毫秒
141.
R. N. Ball 《Algebra Universalis》1996,35(1):85-112
Any lattice-ordered group (l-group for short) is essentially extended by its lexicographic product with a totally ordered group. That is, anl-homomorphism (i.e., a group and lattice homomorphism) on the extension which is injective on thel-group must be injective on the extension as well. Thus nol-group has a maximal essential extension in the categoryIGp ofl-groups withl-homomorphisms. However, anl-group is a distributive lattice, and so has a maximal essential extension in the categoryD of distributive lattices with lattice homomorphisms. Adistinguished extension of onel-group by another is one which is essential inD. We characterize such extensions, and show that everyl-groupG has a maximal distinguished extensionE(G) which is unique up to anl-isomorphism overG.E(G) contains most other known completions in whichG is order dense, and has mostl-group completeness properties as a result. Finally, we show that ifG is projectable then E(G) is the -completion of the projectable hull ofG.Presented by M. Henriksen. 相似文献
142.
In this paper, we discuss the representation-finite selfinjective artin algebras of classB
n andC
n and obtain the following main results:
For any fieldk, let Λ be a representation-finite selfinjective artin algebras of classB
n orC
n overk.
相似文献
(a) | We give the configuration ofZB n andZC n. |
(b) | We show that Λ is standard. |
(c) | Under the condition ofk being a perfect field, we describe Λ by boundenk-species and show that Λ is a finite covering of the trivial extension of some tilted algebra of typeB n orC n. |
143.
R. A. English S. G. Davidson Z. L. Miskovic F. O. Goodman A. T. Amos B. L. Burrows 《Progress in Surface Science》1996,53(2-4):323-330
A recursive Green-function (RGF) technique is used to study the surface states of an electrified solid. The concatenating nature of the method leads to a continued-fraction form of the RGF, which can be expressed as a ratio of Bessel functions. The surface density of states (SDOS), derived from the RGF, reveals a quasi-Stark-ladder distribution of the energy levels at the surface atom. The dependence of the SDOS on the applied field and surface perturbation parameters is discussed. 相似文献
144.
Todor Gramchev 《Monatshefte für Mathematik》1991,112(2):99-113
We study the weak limits
(t, .)of solutions to semilinear strictly hyperbolic systems and wave equations with initial datau
(0, .) approximating a distribution, 0 <
1. We propose an optimal link between the singularity of and the growth of the nonlinear term in order that
exists. In this way we extend some of the results in [3], [10], [13]. 相似文献
145.
In this paper we consider families of distinct ovals in the plane, with the property that certain subfamilies have stabbing lines (transversals). Our main result says that if any k member of the family can be stabbed by a line avoiding all the other ovals and k is large enough, then the family consists of at most k+1 ovals. For any n4 we show a family of n ovals, whose n–2 element subfamilies have, but the n–1 element subfamilies do not have, transversals. 相似文献
146.
LOCALIZED PATTERNS OF THE CUBIC-QUINTIC SWIFT-HOHENBERG EQUATIONS WITH TWO SYMMETRY-BREAKING TERMS 下载免费PDF全文
Homoclinic snake always refers to the branches of homoclinic orbits \mbox{near} a heteroclinic cycle connecting a hyperbolic or non-hyperbolic equilibrium and a periodic
orbit in a reversible variational system. In this paper, the normal form of a Swift-Hohenberg equation with two different symmetry-breaking terms (non-reversible term and non-k-symmetry term) are investigated by using multiple scale method, and their bifurcation diagrams are initially studied by numerical simulations. Typically, we predict numerically the existence of so-called round-snakes and round-isolas upon particular two symmetric-breaking perturbations. 相似文献
147.
B. Levit 《Mathematical Methods of Statistics》2016,25(4):235-261
Within the framework of Optimal Recovery, optimal methods of interpolation, based on the Abel–Jacobi elliptic functions, have been found for some Hardy classes of analytic functions [9]. It will be shown that these methods are also optimal according to criteria of Optimal Design and Nonparametric Regression.For all noise levels away from 0, the mean squared error of the optimal interpolant is evaluated explicitly, in a non-asymptotic setting. In this result, a pivotal role is played by an interference effect in which both stochastic and deterministic parts of the interpolant exhibit an oscillating behavior, with the two oscillating functions canceling each other. 相似文献
148.
149.
We investigate the generalized polynomial Linard differential equations. Using the averaging theory of first and second order, we obtain the maximum number of limit cycles of the system. 相似文献
150.
In this paper we compare the sample mean and the sample median of independent and identically distributed data that come from a symmetric stable distribution using Banks’ (1997) criterion, which is an alternative to Pitman’s (1937) criterion for comparing estimators of a parameter of interest. For data from a symmetric stable distribution with index of stability between one half and one and odd sample size, we show that Banks’ criterion choses the sample median as an estimator of the location parameter of the distribution. For data from a normal distribution with even sample size, we show that Banks’ criterion favours the sample mean (thus “complementing” a similar result about odd sample sizes in Karunaratne and Hadjicostas (2009)). In the process, we prove some trigonometric inequalities, which are interesting in their own right. 相似文献