全文获取类型
收费全文 | 103903篇 |
免费 | 5052篇 |
国内免费 | 3212篇 |
专业分类
化学 | 41662篇 |
晶体学 | 1034篇 |
力学 | 8494篇 |
综合类 | 217篇 |
数学 | 35032篇 |
物理学 | 25728篇 |
出版年
2024年 | 106篇 |
2023年 | 592篇 |
2022年 | 1068篇 |
2021年 | 1054篇 |
2020年 | 1103篇 |
2019年 | 1045篇 |
2018年 | 11161篇 |
2017年 | 10903篇 |
2016年 | 7275篇 |
2015年 | 2115篇 |
2014年 | 1818篇 |
2013年 | 2351篇 |
2012年 | 6127篇 |
2011年 | 12766篇 |
2010年 | 7158篇 |
2009年 | 7511篇 |
2008年 | 8224篇 |
2007年 | 10113篇 |
2006年 | 1566篇 |
2005年 | 2427篇 |
2004年 | 2354篇 |
2003年 | 2617篇 |
2002年 | 1610篇 |
2001年 | 756篇 |
2000年 | 801篇 |
1999年 | 778篇 |
1998年 | 716篇 |
1997年 | 666篇 |
1996年 | 681篇 |
1995年 | 579篇 |
1994年 | 459篇 |
1993年 | 437篇 |
1992年 | 337篇 |
1991年 | 313篇 |
1990年 | 287篇 |
1989年 | 244篇 |
1988年 | 203篇 |
1987年 | 181篇 |
1986年 | 150篇 |
1985年 | 140篇 |
1984年 | 105篇 |
1983年 | 86篇 |
1982年 | 93篇 |
1981年 | 60篇 |
1980年 | 58篇 |
1979年 | 48篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
In this note we show how 1-factors in the middle two layers of the discrete cube can be used to construct 2-factors in the
Odd graph (the Kneser graph of (k − 1)-sets from a (2k − 1)-set). In particular, we use the lexical matchings of Kierstead and Trotter, and the modular matchings of Duffus, Kierstead
and Snevily, to give explicit constructions of two different 2-factorisations of the Odd graph.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
192.
Siaw-Lynn Ng 《Order》2004,21(1):1-5
We present a characterisation of posets of size n with linear discrepancy n − 2. These are the posets that are “furthest” from a linear order without being an antichain.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
193.
In this paper, a unified approach for analysing finite dimensional approximations to a class of partial differential equations boundary value problems (second‐kind Fredholm differential equations) is introduced. The approach is shown to be general despite of its extremely simple form. In particular, it is expected to be useful in the convergence analysis of finite element methods for solving PDE problems. Three specific examples are presented to illustrate the broad applicability of the approach. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
194.
Curtis T. Mcmullen 《Acta Mathematica》2003,191(2):191-223
195.
We will prove a result concerning the inclusion of non-trivial invariant ideals inside non-trivial ideals of a twisted crossed
product. We will also give results concerning the primeness and simplicity of crossed products of twisted actions of locally
compact groups on -algebras.
Received: 25 January 2002; in final form: 22 May 2002/Published online: 2 December 2002
This work is partially supported by Hong Kong RGC Direct Grant. 相似文献
196.
Abstract. We prove that a set of n disjoint unit balls in R
d
admits at most four distinct geometric permutations, or line transversals, thus settling a long-standing conjecture in combinatorial geometry.
The constant bound significantly improves upon the Θ (n
d-1
) bound for disjoint balls of unrestricted radii. 相似文献
197.
本文给出了 n阶 r-不可分矩阵的本原指数的上界 ,即任 n阶 r—不可分矩阵 A的本原指数 (A)≤n+(r- ) 2r (1≤ r相似文献
198.
Wang Renhong Zhou Heng 《分析论及其应用》2003,19(3)
1 IntroductionLet Sd- 1 bethe unitsphere of Rd,Πdthe space of allpolynomialsofd variables,and x(i)= (x1 ,… ,xi) (i=1 ,… ,d) .In this paper,we are concerned with the homogeneous polyno-mials orthogonal with the weightfunction h(x(d) ) =x2 k11 …x2 kdd on Sd- 1 ,where ki≥ 0 (i=1 ,… ,d) .Connected with the weightfunction h(x(d) ) are the following differential-differenceoperators introduced by Charles F. Dunkl in [3 ] ,Dip(x(d) ) = p(x(d) ) xi+ di=1kip(x(d) ) -p(x1 ,… ,-xi,… ,xd)xi,Δ… 相似文献
199.
200.
The influence of the sample orientation on the effective value of the hydrostatic piezoelectric coefficients d
h
(i)
of Sn2P2S6 crystals has been studied. The hydrostatic piezoelectric coefficients d
h
(1)
and d′
h
(3)
, were measured, d
h
(1)
=(244±3) pC/N and d′
h
(3)
=(92±1) pC/N. The hydrostatic piezoelectric coefficient d
h
(3)
for orthogonal axis system was calculated to be d
h
(3)
=(87±2) pC/N. The, optimal orientation of the sample has been found as (Xy l)−20°-cut. Maximal value of the effective hydrostatic piezoelectric coefficient d
h
(1)
equals 260 pC/N. Double rotated samples were also studied. The orientation of the samples insensitive to the pressure has
been found. The theoretical mean value of hydrostatic piezoelectric coefficient (d
h
)
mean
corresponding to randomly oriented Sn2P2S6 grains in a poled composite has been calculated to be (d
h
)
mean
=136 pC/N. 相似文献