全文获取类型
收费全文 | 12632篇 |
免费 | 468篇 |
国内免费 | 494篇 |
专业分类
化学 | 4834篇 |
晶体学 | 140篇 |
力学 | 225篇 |
综合类 | 52篇 |
数学 | 6385篇 |
物理学 | 1958篇 |
出版年
2023年 | 42篇 |
2022年 | 120篇 |
2021年 | 87篇 |
2020年 | 158篇 |
2019年 | 281篇 |
2018年 | 276篇 |
2017年 | 229篇 |
2016年 | 202篇 |
2015年 | 198篇 |
2014年 | 324篇 |
2013年 | 600篇 |
2012年 | 396篇 |
2011年 | 645篇 |
2010年 | 533篇 |
2009年 | 872篇 |
2008年 | 765篇 |
2007年 | 725篇 |
2006年 | 627篇 |
2005年 | 553篇 |
2004年 | 672篇 |
2003年 | 579篇 |
2002年 | 536篇 |
2001年 | 443篇 |
2000年 | 368篇 |
1999年 | 359篇 |
1998年 | 272篇 |
1997年 | 250篇 |
1996年 | 303篇 |
1995年 | 250篇 |
1994年 | 298篇 |
1993年 | 222篇 |
1992年 | 183篇 |
1991年 | 119篇 |
1990年 | 93篇 |
1989年 | 98篇 |
1988年 | 75篇 |
1987年 | 90篇 |
1986年 | 72篇 |
1985年 | 69篇 |
1984年 | 70篇 |
1983年 | 21篇 |
1982年 | 58篇 |
1981年 | 74篇 |
1980年 | 68篇 |
1979年 | 82篇 |
1978年 | 61篇 |
1977年 | 59篇 |
1976年 | 44篇 |
1974年 | 22篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
33.
34.
Linear mixed 0–1 integer programming problems may be reformulated as equivalent continuous bilevel linear programming (BLP)
problems. We exploit these equivalences to transpose the concept of mixed 0–1 Gomory cuts to BLP. The first phase of our new
algorithm generates Gomory-like cuts. The second phase consists of a branch-and-bound procedure to ensure finite termination
with a global optimal solution. Different features of the algorithm, in particular, the cut selection and branching criteria
are studied in details. We propose also a set of algorithmic tests and procedures to improve the method. Finally, we illustrate
the performance through numerical experiments. Our algorithm outperforms pure branch-and-bound when tested on a series of
randomly generated problems.
Work of the authors was partially supported by FCAR, MITACS and NSERC grants. 相似文献
35.
Clemens Amstler 《Monatshefte für Mathematik》1995,119(3):177-186
In this paper we establish an inequality of Koksma-Hlawka-type for compact groups. We first define a discrepancy for compact groups based on discrepancy operators introduced by W. Fleischer and show the relation to the classicalL
2-discrepancy. Then we prove the inequality for functions in a weightedL
2-space. 相似文献
36.
P. Danchev 《Lithuanian Mathematical Journal》2007,47(2):129-134
We prove the following theorem: Any abelian p-group is an n-Σ-group which is a strong ω-elongation of a totally projective group by a p
ω+n
-projective group precisely when it is totally projective. In particular, each p-torsion p
ω+n
-projective n-Σ-group is a direct sum of countable p-groups of length not exceeding ω + n and vice versa. These two claims generalize our recent results in [6] and [7].
Published in Lietuvos Matematikos Rinkinys, Vol. 47, No. 2, pp. 155–162, April–June, 2007. 相似文献
37.
This article introduces and analyzes a p-version FEM for variational inequalities resulting from obstacle problems for some quasi-linear elliptic partial differential
operators. We approximate the solution by controlling the obstacle condition in images of the Gauss–Lobatto points. We show
existence and uniqueness for the discrete solution u
p
from the p-version for the obstacle problem. We prove the convergence of u
p
towards the solution with respect to the energy norm, and assuming some additional regularity for the solution we derive
an a priori error estimate. In numerical experiments the p-version turns out to be superior to the h-version concerning the convergence rate and the number of unknowns needed to achieve a certain exactness of the approximation. 相似文献
38.
For a general K3 surface S of genus g, with 2 ≤ g ≤ 10, we prove that the intermediate Jacobians of the family of prime Fano threefolds of genus g containing S as a hyperplane section, form generically an algebraic completely integrable Hamiltonian system.
The first author is partially supported by grant MI1503/2005 of the Bulgarian Foundation for Scientific Research. 相似文献
39.
Tokuzo Shiga 《Probability Theory and Related Fields》1997,108(3):417-439
Summary. We study the exponential decay rate of the survival probability up to time t>0 of a random walker moving in Zopf;
d
in a temporally and spatially fluctuating random environment. When the random walker has a speed parameter κ>0, we investigate
the influence of κ on the exponential decay rate λ(d,κ). In particular we prove that for any fixed d≥1, λ(d,κ) behaves like as logκ as κ↘0.
Received: 21 May 1996 / In revised form: 2 February 1997 相似文献
40.
Let E\subset \Bbb R
s
be compact and let d
n
E
denote the dimension of the space of polynomials of degree at most n in s variables restricted to E . We introduce the notion of an asymptotic interpolation measure (AIM). Such a measure, if it exists , describes the asymptotic behavior of any scheme τ
n
={ \bf x
k,n
}
k=1
dnE
, n=1,2,\ldots , of nodes for multivariate polynomial interpolation for which the norms of the corresponding interpolation operators do
not grow geometrically large with n . We demonstrate the existence of AIMs for the finite union of compact subsets of certain algebraic curves in R
2
. It turns out that the theory of logarithmic potentials with external fields plays a useful role in the investigation. Furthermore,
for the sets mentioned above, we give a computationally simple construction for ``good' interpolation schemes.
November 9, 2000. Date revised: August 4, 2001. Date accepted: September 14, 2001. 相似文献