全文获取类型
收费全文 | 5478篇 |
免费 | 346篇 |
国内免费 | 517篇 |
专业分类
化学 | 439篇 |
晶体学 | 5篇 |
力学 | 287篇 |
综合类 | 123篇 |
数学 | 5129篇 |
物理学 | 358篇 |
出版年
2024年 | 6篇 |
2023年 | 66篇 |
2022年 | 88篇 |
2021年 | 102篇 |
2020年 | 113篇 |
2019年 | 117篇 |
2018年 | 134篇 |
2017年 | 141篇 |
2016年 | 137篇 |
2015年 | 106篇 |
2014年 | 217篇 |
2013年 | 377篇 |
2012年 | 245篇 |
2011年 | 299篇 |
2010年 | 278篇 |
2009年 | 380篇 |
2008年 | 381篇 |
2007年 | 346篇 |
2006年 | 346篇 |
2005年 | 275篇 |
2004年 | 233篇 |
2003年 | 272篇 |
2002年 | 229篇 |
2001年 | 211篇 |
2000年 | 180篇 |
1999年 | 178篇 |
1998年 | 176篇 |
1997年 | 156篇 |
1996年 | 93篇 |
1995年 | 69篇 |
1994年 | 61篇 |
1993年 | 49篇 |
1992年 | 38篇 |
1991年 | 25篇 |
1990年 | 21篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 26篇 |
1984年 | 21篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1981年 | 17篇 |
1980年 | 19篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有6341条查询结果,搜索用时 9 毫秒
81.
Zoltán Lóránt Nagy 《Journal of Graph Theory》2017,84(4):566-580
We study the existence and the number of k‐dominating independent sets in certain graph families. While the case namely the case of maximal independent sets—which is originated from Erd?s and Moser—is widely investigated, much less is known in general. In this paper we settle the question for trees and prove that the maximum number of k‐dominating independent sets in n‐vertex graphs is between and if , moreover the maximum number of 2‐dominating independent sets in n‐vertex graphs is between and . Graph constructions containing a large number of k‐dominating independent sets are coming from product graphs, complete bipartite graphs, and finite geometries. The product graph construction is associated with the number of certain Maximum Distance Separable (MDS) codes. 相似文献
82.
We introduce the concept of κ-analytic and κ-Luzin spaces as images of complete metric spaces by (disjoint) upper semi-continuous compact-valued correspondences which “preserve discreteness” in some sence (Definition in Section 3.1). The case κ = ω coincides with (Lindelöf) analytic spaces studied by Choquet, the first author and others. The main results are characterizations of uniform analytic spaces in terms of other parametrizations, complete sequences of covers, and Suslin subsets of some product of a compact and a complete metric space (Theorems in Section 3.2 and in Section 4), and characterizations of topological analytic spaces as Suslin subsets of paracompact ?ech-complete spaces (Theorem in Section 5). 相似文献
83.
P. C. Allaart 《Acta Mathematica Hungarica》2008,121(3):243-275
This paper concerns the maximum value and the set of maximum points of a random version of Takagi’s continuous, nowhere differentiable
function. Let F(x):=∑
n=1∞
ε
n
ϕ(2
n−1
x), x ∈ R, where ɛ
1, ɛ
2, ... are independent, identically distributed random variables taking values in {−1, 1}, and ϕ is the “tent map” defined by ϕ(x) = 2 dist (x, Z). Let p:= P (ɛ
1 = 1), M:= max {F(x): x ∈ R}, and := {x ∈ [0, 1): F(x) = M}. An explicit expression for M is given in terms of the sequence {ɛ
n
}, and it is shown that the probability distribution μ of M is purely atomic if p < , and is singular continuous if p ≧ . In the latter case, the Hausdorff dimension and the multifractal spectrum of μ are determined. It is shown further that the set is finite almost surely if p < , and is topologically equivalent to a Cantor set almost surely if p ≧ . The distribution of the cardinality of is determined in the first case, and the almost-sure Hausdorff dimension of is shown to be (2p − 1)/2p in the second case. The distribution of the leftmost point of is also given. Finally, some of the results are extended to the more general functions Σa
n − 1
ɛ
n
ϕ(2
n − 1
x), where 0 < a < 1.
相似文献
84.
Z. Buczolich 《Acta Mathematica Hungarica》2008,121(4):371-393
One can define in a natural way irregular 1-sets on the graphs of several fractal functions, like Takagi’s function, Weierstrass-Cellerier type functions and the typical continuous function. These irregular 1-sets can be useful during the investigation of level-sets and occupation measures of these functions. For example, we see that for Takagi’s function and for certain Weierstrass-Cellerier functions the occupation measure is singular with respect to the Lebesgue measure and for almost every level the level set is finite. 相似文献
85.
Imed Zaguia 《Discrete Mathematics》2008,308(23):5727-5734
We prove that a prime interval order, not necessarily finite, has no prime upper cover if and only if it has width two. On the other hand, we prove that every finite prime N-free order has at least one prime upper cover. 相似文献
86.
Jacek Chudziak 《Journal of Mathematical Analysis and Applications》2008,339(1):454-460
Let X be a vector space over a field K of real or complex numbers, n∈N and λ∈K?{0}. We study the stability problem for the Go?a?b-Schinzel type functional equations
f(x+fn(x)y)=λf(x)f(y) 相似文献
87.
We consider the permeability estimation problem in two-phase porous media flow. We try to identify the permeability field by utilizing both the production data from wells as well as inverted seismic data. The permeability field is assumed to be piecewise constant, or can be approximated well by a piecewise constant function. A variant of the level set method, called Piecewise Constant Level Set Method is used to represent the interfaces between the regions with different permeability levels. The inverse problem is solved by minimizing a functional, and TV norm regularization is used to deal with the ill-posedness. We also use the operator-splitting technique to decompose the constraint term from the fidelity term. This gives us more flexibility to deal with the constraint and helps to stabilize the algorithm. 相似文献
88.
We introduce the class of weak amicable T‐matrices and use it to construct a class of orthogonal designs, for p = 1 and for p a prime power ≡ 3 (mod 4), and all odd q, q ≤ 21. This class includes new Plotkin arrays of order 24, 40, 56 and for the first time, of orders 8q, q ∈ {9,11,13,15,17,19,21}. © 2006 Wiley Periodicals, Inc. J Combin Designs 16: 44–52, 2008 相似文献
89.
Let be the complement of the intersection graph G of a family of translations of a compact convex figure in Rn. When n=2, we show that , where γ(G) is the size of the minimum dominating set of G. The bound on is sharp. For higher dimension we show that , for n?3. We also study the chromatic number of the complement of the intersection graph of homothetic copies of a fixed convex body in Rn. 相似文献
90.
T. D. Narang 《分析论及其应用》2008,24(1):67-73
Some generalizations of the result proved by S.P Singh[J.Approx.Theory 25(1979),89-90]are presented in convex metric spaces.The results proved contain several known results on the subject. 相似文献