全文获取类型
收费全文 | 10392篇 |
免费 | 0篇 |
专业分类
管理学 | 1499篇 |
民族学 | 99篇 |
人口学 | 2407篇 |
理论方法论 | 481篇 |
综合类 | 286篇 |
社会学 | 4438篇 |
统计学 | 1182篇 |
出版年
2018年 | 1657篇 |
2017年 | 1650篇 |
2016年 | 1072篇 |
2015年 | 33篇 |
2014年 | 33篇 |
2013年 | 28篇 |
2012年 | 318篇 |
2011年 | 1144篇 |
2010年 | 1043篇 |
2009年 | 781篇 |
2008年 | 817篇 |
2007年 | 995篇 |
2005年 | 224篇 |
2004年 | 250篇 |
2003年 | 210篇 |
2002年 | 81篇 |
2001年 | 5篇 |
2000年 | 10篇 |
1999年 | 5篇 |
1996年 | 28篇 |
1988年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
851.
Thomas Nittner 《Statistical Methods and Applications》2003,12(2):195-210
The additive model
is considered when some observations on x are missing at random but corresponding observations on y are available. Especially for this model, missing at random is an interesting case because the complete case analysis is expected to be no more suitable. A simulation experiment is reported and the different methods are compared based on their superiority with respect to the sample mean squared error. Some focus is also given on the sample variance and the estimated bias. In detail, the complete case analysis, a kind of stochastic mean imputation, a single imputation and the nearest neighbor imputation are discussed. 相似文献
852.
Astrid Schreyögg 《Organisationsberatung, Supervision, Coaching》2007,14(2):107-108
853.
Maria Liazi Ioannis Milis Fanny Pascual Vassilis Zissimopoulos 《Journal of Combinatorial Optimization》2007,14(4):465-474
The Densest k-Subgraph (DkS) problem asks for a k-vertex subgraph of a given graph with the maximum number of edges. The problem is strongly NP-hard, as a generalization of
the well known Clique problem and we also know that it does not admit a Polynomial Time Approximation Scheme (PTAS). In this paper we focus on
special cases of the problem, with respect to the class of the input graph. Especially, towards the elucidation of the open
questions concerning the complexity of the problem for interval graphs as well as its approximability for chordal graphs,
we consider graphs having special clique graphs. We present a PTAS for stars of cliques and a dynamic programming algorithm
for trees of cliques.
M.L. is co-financed within Op. Education by the ESF (European Social Fund) and National Resources.
V.Z. is partially supported by the Special Research Grants Account of the University of Athens under Grant 70/4/5821. 相似文献
854.
We study a variant of classical scheduling, which is called scheduling with “end of sequence” information. It is known in advance that the last job has the longest processing time. Moreover, the last job is marked, and thus it
is known for every new job whether it is the final job of the sequence. We explore this model on two uniformly related machines,
that is, two machines with possibly different speeds. Two objectives are considered, maximizing the minimum completion time
and minimizing the maximum completion time (makespan). Let s be the speed ratio between the two machines, we consider the competitive ratios which are possible to achieve for the two
problems as functions of s. We present algorithms for different values of s and lower bounds on the competitive ratio. The proposed algorithms are best possible for a wide range of values of s. For the overall competitive ratio, we show tight bounds of ϕ + 1 ≈ 2.618 for the first problem, and upper and lower bounds
of 1.5 and 1.46557 for the second problem.
The authors would like to dedicate this paper to the memory of our colleague and friend Yong He who passed away in August
2005 after struggling with illness.
D. Ye: Research was supported in part by NSFC (10601048). 相似文献
855.
We present a new biclustering algorithm to simultaneously discover tissue classes and identify a set of genes that well-characterize
these classes from DNA microarray data sets. We employ a combinatorial optimization approach where the object is to simultaneously
identify an interesting set of genes and a partition of the array samples that optimizes a certain score based on a novel
color island statistic. While this optimization problem is NP-complete in general, we are effectively able to solve problems
of interest to optimality using a branch-and-bound algorithm. We have tested the algorithm on a 30 sample Cutaneous T-cell Lymphoma data set; it was able to almost perfectly discriminate short-term survivors from long-term survivors and normal
controls. Another useful feature of our method is that can easily handle missing expression data. 相似文献
856.
In this paper, we consider the problem of enumerating all maximal motifs in an input string for the class of repeated motifs
with wild cards. A maximal motif is such a representative motif that is not properly contained in any larger motifs with the
same location lists. Although the enumeration problem for maximal motifs with wild cards has been studied in Parida et al.
(2001), Pisanti et al. (2003) and Pelfrêne et al. (2003), its output-polynomial time computability has been still open. The
main result of this paper is a polynomial space polynomial delay algorithm for the maximal motif enumeration problem for the
repeated motifs with wild cards. This algorithm enumerates all maximal motifs in an input string of length n in O(n
3) time per motif with O(n) space, in particular O(n
3) delay. The key of the algorithm is depth-first search on a tree-shaped search route over all maximal motifs based on a technique
called prefix-preserving closure extension. We also show an exponential lower bound and a succinctness result on the number
of maximal motifs, which indicate the limit of a straightforward approach. The results of the computational experiments show
that our algorithm can be applicable to huge string data such as genome data in practice, and does not take large additional
computational cost compared to usual frequent motif mining algorithms.
This work is done during the Hiroki Arimura’s visit in LIRIS, University Claude-Bernard Lyon 1, France. 相似文献
857.
858.
Vincenzo Cutello Giuseppe Nicosia Mario Pavone 《Journal of Combinatorial Optimization》2007,14(1):9-33
We present a new Immune Algorithm, IMMALG, that incorporates a Stochastic Aging operator and a simple local search procedure to improve the overall performances in
tackling the chromatic number problem (CNP) instances. We characterize the algorithm and set its parameters in terms of Kullback
Entropy. Experiments will show that the IA we propose is very competitive with the state-of-art evolutionary algorithms. 相似文献
859.
Bernard Gendron Alain Hertz Patrick St-Louis 《Journal of Combinatorial Optimization》2007,13(2):163-178
We consider the problem of orienting the edges of a graph so that the length of a longest path in the resulting digraph is
minimum. As shown by Gallai, Roy and Vitaver, this edge orienting problem is equivalent to finding the chromatic number of
a graph. We study various properties of edge orienting methods in the context of local search for graph coloring. We then
exploit these properties to derive four tabu search algorithms, each based on a different neighborhood. We compare these algorithms
numerically to determine which are the most promising and to give potential research directions. 相似文献
860.
The wireless network jamming problem 总被引:1,自引:0,他引:1
Clayton W. Commander Panos M. Pardalos Valeriy Ryabchenko Stan Uryasev Grigoriy Zrazhevsky 《Journal of Combinatorial Optimization》2007,14(4):481-498
In adversarial environments, disabling the communication capabilities of the enemy is a high priority. We introduce the problem
of determining the optimal number and locations for a set of jamming devices in order to neutralize a wireless communication
network. This problem is known as the wireless network jamming problem. We develop several mathematical programming formulations based on covering the communication nodes and limiting the connectivity
index of the nodes. Two case studies are presented comparing the formulations with the addition of various percentile constraints.
Finally, directions of further research are addressed. 相似文献