全文获取类型
收费全文 | 4818篇 |
免费 | 96篇 |
国内免费 | 82篇 |
专业分类
化学 | 484篇 |
晶体学 | 8篇 |
力学 | 76篇 |
数学 | 4122篇 |
物理学 | 306篇 |
出版年
2023年 | 20篇 |
2022年 | 18篇 |
2021年 | 23篇 |
2020年 | 28篇 |
2019年 | 57篇 |
2018年 | 69篇 |
2017年 | 58篇 |
2016年 | 59篇 |
2015年 | 56篇 |
2014年 | 69篇 |
2013年 | 280篇 |
2012年 | 120篇 |
2011年 | 189篇 |
2010年 | 109篇 |
2009年 | 296篇 |
2008年 | 370篇 |
2007年 | 399篇 |
2006年 | 300篇 |
2005年 | 235篇 |
2004年 | 201篇 |
2003年 | 143篇 |
2002年 | 62篇 |
2001年 | 91篇 |
2000年 | 84篇 |
1999年 | 97篇 |
1998年 | 99篇 |
1997年 | 70篇 |
1996年 | 94篇 |
1995年 | 113篇 |
1994年 | 103篇 |
1993年 | 78篇 |
1992年 | 84篇 |
1991年 | 40篇 |
1990年 | 58篇 |
1989年 | 47篇 |
1988年 | 46篇 |
1987年 | 66篇 |
1986年 | 59篇 |
1985年 | 81篇 |
1984年 | 48篇 |
1983年 | 47篇 |
1982年 | 91篇 |
1981年 | 66篇 |
1980年 | 61篇 |
1979年 | 30篇 |
1978年 | 56篇 |
1977年 | 57篇 |
1976年 | 57篇 |
1975年 | 7篇 |
1974年 | 4篇 |
排序方式: 共有4996条查询结果,搜索用时 937 毫秒
71.
72.
73.
Manfred Droste 《Order》1988,5(3):261-273
We show that any lattice-ordered group (l-group) G can be l-embedded into continuously many l-groups H
i
which are pairwise elementarily inequivalent both as groups and as lattices with constant e. Our groups H
i
can be distinguished by group-theoretical first-order properties which are induced by lattice-theoretically nice properties of their normal subgroup lattices. Moreover, they can be taken to be 2-transitive automorphism groups A(S
i
) of infinite linearly ordered sets (S
i
, ) such that each group A(S
i
) has only inner automorphisms. We also show that any countable l-group G can be l-embedded into a countable l-group H whose normal subgroup lattice is isomorphic to the lattice of all ideals of the countable dense Boolean algebra B. 相似文献
74.
75.
Summary We consider a walk from a stateA
1 to a stateA
n+1 in which the probability of remaining atA
i
isp
i
, and the probability of progressing fromA
i
toA
i+1 is 1 –p
i
. The probabilityW
nk
of reachingA
n+1 fromA
1 in exactlyn + k steps can then be expressed as a polynomial of degreen + k in then variablesp
1,,p
n
. We determine the maximum value ofW
nk
and the (unique) choice (p
1,,p
n
) for which this extremum occurs.Dedicated to Professor Otto Haupt with best wishes on his 100th birthday 相似文献
76.
B. Barabás 《Periodica Mathematica Hungarica》1987,18(2):115-122
The properties of the empirical density function,f
n(x) = k/n(
j
+
–
j-1
+
) if
j-1
+
< x + where
j-1
+
and
j
+
are sample elements and there are exactlyk – 1 sample elements between them, are studied in that practical point of view how to choose a suitablek for a good estimation. A bound is given for the expected value of the absolute value of difference between the empirical and theoretical density functions. 相似文献
77.
78.
79.
This is one in a series of papers studying measures of information in the so-called mixed theory of information (i.e. considering the events as well as their probabilities) on the open domain (i.e. without empty sets and zero probabilities). In this paper we find all-recursive, 3-semisymmetric inset entropies on the open domain. We do this by solving the fundamental equation of inset information of degree () on the open domain.Dedicated to Professor János Aczél on his 60th birthday. 相似文献
80.
David Whitley 《Acta Appl Math》1986,5(3):279-311
We study the dynamics of a two-parameter family of noninvertible maps of the plane, derived from a model in population dynamics. We prove that, as one parameter varies with the other held fixed, the nonwandering set changes from the empty set to an unstable Cantor set on which the map is topologically equivalent to the shift endomorphism on two symbols. With the help of some numerical work, we trace the genealogies of the periodic points of the family of period 5, and describe their stability types and bifurcations. Among our results we find that the family has a fixed point which undergoes fold, flip and Hopf bifurcations, and that certain families of period five points are interconnected through a codimension-two cusp bifurcation. 相似文献