全文获取类型
收费全文 | 59415篇 |
免费 | 1953篇 |
国内免费 | 146篇 |
专业分类
化学 | 36493篇 |
晶体学 | 313篇 |
力学 | 1062篇 |
综合类 | 3篇 |
数学 | 11499篇 |
物理学 | 12144篇 |
出版年
2023年 | 402篇 |
2022年 | 340篇 |
2021年 | 792篇 |
2020年 | 906篇 |
2019年 | 865篇 |
2018年 | 1496篇 |
2017年 | 1230篇 |
2016年 | 2082篇 |
2015年 | 1707篇 |
2014年 | 1741篇 |
2013年 | 3705篇 |
2012年 | 3586篇 |
2011年 | 3550篇 |
2010年 | 2352篇 |
2009年 | 2021篇 |
2008年 | 3118篇 |
2007年 | 2900篇 |
2006年 | 2622篇 |
2005年 | 2618篇 |
2004年 | 2217篇 |
2003年 | 1877篇 |
2002年 | 1648篇 |
2001年 | 1174篇 |
2000年 | 1224篇 |
1999年 | 859篇 |
1998年 | 655篇 |
1997年 | 591篇 |
1996年 | 724篇 |
1995年 | 512篇 |
1994年 | 608篇 |
1993年 | 539篇 |
1992年 | 567篇 |
1991年 | 474篇 |
1990年 | 530篇 |
1989年 | 437篇 |
1988年 | 437篇 |
1987年 | 385篇 |
1986年 | 386篇 |
1985年 | 536篇 |
1984年 | 512篇 |
1983年 | 389篇 |
1982年 | 404篇 |
1981年 | 409篇 |
1980年 | 333篇 |
1979年 | 324篇 |
1978年 | 335篇 |
1977年 | 312篇 |
1976年 | 325篇 |
1974年 | 283篇 |
1973年 | 299篇 |
排序方式: 共有10000条查询结果,搜索用时 34 毫秒
101.
The exponential functional of simple, symmetric random walks with negative
drift is an infinite polynomial Y = 1 + ξ1 + ξ1ξ2 + ξ1ξ2ξ3 + ⋯ of independent
and identically distributed non-negative random variables. It has moments that are
rational functions of the variables μ
k
= E(ξ
k
) < 1 with universal coefficients. It
turns out that such a coefficient is equal to the number of permutations with descent
set defined by the multiindex of the coefficient. A recursion enumerates all numbers
of permutations with given descent sets in the form of a Pascal-type triangle.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
102.
Periodica Mathematica Hungarica - In our paper we study the usage of partially defined Boolean functions (PDBFs) for generating cryptographically strong Boolean functions. A PDBF can be considered... 相似文献
103.
A note on a generalized Douglas space 总被引:1,自引:0,他引:1
Periodica Mathematica Hungarica - 相似文献
104.
Paramagnetic pyrroline and 1,2,3,6-tetrahydropyridine derivatives of BODIPY and their diamagnetic analogs have been synthesized and characterized as novel redox double sensor and cation sensitive reagents. 相似文献
105.
We characterise the abelianisation of a group that has a presentation for which the set of relations is invariant under the full symmetric group acting on the set of generators. This improves a result of Emerson.
106.
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
107.
It is a well-known feature of odd space-time dimensions d that there exist two inequivalent fundamental representations A and B of the Dirac gamma matrices. Moreover, the parity transformation swaps the fermion fields living in A and B. As a consequence, a parity-invariant Lagrangian can only be constructed by incorporating both the representations. Based upon these ideas and contrary to long-held belief, we show that in addition to a discrete exchange symmetry for the massless case, we can also define chiral symmetry provided the Lagrangian contains fields corresponding to both the inequivalent representations. We also study the transformation properties of the corresponding chiral currents under parity and charge-conjugation operations. We work explicitly in 2 + 1 dimensions and later show how some of these ideas generalize to an arbitrary number of odd dimensions. 相似文献
108.
The function lattice, or generalized Boolean algebra, is the set of ℓ-tuples with the ith coordinate an integer between 0 and a bound ni. Two ℓ-tuples t-intersect if they have at least t common nonzero coordinates. We prove a Hilton–Milner type theorem for systems of t-intersecting ℓ-tuples.Received September 29, 2004 相似文献
109.
Sufficient conditions which guarantee that certain linear integro-differential equation cannot have a positive solution are
established. 相似文献
110.
Máté Matolcsi 《Acta Mathematica Hungarica》2005,108(1-2):129-136
Summary He present work deals with estimations of the n-th linear polarization constant c(H)n of an n-dimensional real Hilbert space H. We provide some new lower bounds on the value of sup║y║=1 │1,y> ... n,y>│, where x1, ... ,xn are unit vectors in H. In particular, the results improve an earlier estimate of Marcus. However, the intriguing conjecture c(H) n= nn/2 remains open. 相似文献