全文获取类型
收费全文 | 67260篇 |
免费 | 2367篇 |
国内免费 | 237篇 |
专业分类
化学 | 40984篇 |
晶体学 | 423篇 |
力学 | 1327篇 |
综合类 | 26篇 |
数学 | 12506篇 |
物理学 | 14598篇 |
出版年
2023年 | 472篇 |
2022年 | 510篇 |
2021年 | 793篇 |
2020年 | 1060篇 |
2019年 | 1001篇 |
2018年 | 1392篇 |
2017年 | 1239篇 |
2016年 | 2392篇 |
2015年 | 1969篇 |
2014年 | 1982篇 |
2013年 | 4445篇 |
2012年 | 4123篇 |
2011年 | 4000篇 |
2010年 | 2624篇 |
2009年 | 2264篇 |
2008年 | 3483篇 |
2007年 | 3275篇 |
2006年 | 3001篇 |
2005年 | 2863篇 |
2004年 | 2448篇 |
2003年 | 2064篇 |
2002年 | 1843篇 |
2001年 | 1429篇 |
2000年 | 1363篇 |
1999年 | 999篇 |
1998年 | 731篇 |
1997年 | 654篇 |
1996年 | 848篇 |
1995年 | 613篇 |
1994年 | 743篇 |
1993年 | 645篇 |
1992年 | 686篇 |
1991年 | 589篇 |
1990年 | 617篇 |
1989年 | 523篇 |
1988年 | 513篇 |
1987年 | 466篇 |
1986年 | 457篇 |
1985年 | 639篇 |
1984年 | 604篇 |
1983年 | 449篇 |
1982年 | 473篇 |
1981年 | 491篇 |
1980年 | 447篇 |
1979年 | 394篇 |
1978年 | 394篇 |
1977年 | 389篇 |
1976年 | 395篇 |
1975年 | 344篇 |
1973年 | 360篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
123.
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
124.
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
125.
A note on a generalized Douglas space 总被引:1,自引:0,他引:1
Periodica Mathematica Hungarica - 相似文献
126.
Jérôme Le NôtreAna Acosta Martinez Pierre H DixneufChristian Bruneau 《Tetrahedron》2003,59(47):9425-9432
Enyne rearrangement of silylated modified terpenoids has been used as the key step for the synthesis of new terpenes and terpenoids. The catalytic system generated in situ from [RuCl2(p-cymene]2, 1,3-bis(mesityl)imidazolinium chloride and cesium carbonate is able to perform the transformation of silylated 1,7-enynes into cyclic siloxanes. Selective cleavage of the silicon-carbon and silicon-oxygen bonds by simple reactions has been performed to afford new terpenes and terpenoids by formal addition of a C5 unit. 相似文献
127.
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
128.
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
129.
Sufficient conditions which guarantee that certain linear integro-differential equation cannot have a positive solution are
established. 相似文献
130.
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