全文获取类型
收费全文 | 240篇 |
免费 | 12篇 |
国内免费 | 6篇 |
专业分类
化学 | 5篇 |
数学 | 221篇 |
物理学 | 10篇 |
综合类 | 22篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 8篇 |
2021年 | 4篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 3篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 13篇 |
2012年 | 4篇 |
2011年 | 9篇 |
2010年 | 14篇 |
2009年 | 13篇 |
2008年 | 21篇 |
2007年 | 11篇 |
2006年 | 20篇 |
2005年 | 6篇 |
2004年 | 9篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有258条查询结果,搜索用时 15 毫秒
251.
252.
Michael Drmota Wojciech Szpankowski 《Journal of Combinatorial Theory, Series A》2011,118(7):1939-1965
A digital search tree (DST) is a fundamental data structure on words that finds various applications from the popular Lempel-Ziv?78 data compression scheme to distributed hash tables. The profile of a DST measures the number of nodes at the same distance from the root; it depends on the number of stored strings and the distance from the root. Most parameters of DST (e.g., depth, height, fillup) can be expressed in terms of the profile. We study here asymptotics of the average profile in a DST built from sequences generated independently by a memoryless source. After representing the average profile by a recurrence, we solve it using a wide range of analytic tools. This analysis is surprisingly demanding but once it is carried out it reveals an unusually intriguing and interesting behavior. The average profile undergoes phase transitions when moving from the root to the longest path: at first it resembles a full tree until it abruptly starts growing polynomially and oscillating in this range. These results are derived by methods of analytic combinatorics such as generating functions, Mellin transform, poissonization and depoissonization, the saddle point method, singularity analysis and uniform asymptotic analysis. 相似文献
253.
List partitions generalize list colourings. Sandwich problems generalize recognition problems. The polynomial dichotomy (NP-complete versus polynomial) of list partition problems is solved for 4-dimensional partitions with the exception of one problem (the list stubborn problem) for which the complexity is known to be quasipolynomial. Every partition problem for 4 nonempty parts and only external constraints is known to be polynomial with the exception of one problem (the 2K2-partition problem) for which the complexity of the corresponding list problem is known to be NP-complete. The present paper considers external constraint 4 nonempty part sandwich problems. We extend the tools developed for polynomial solutions of recognition problems obtaining polynomial solutions for most corresponding sandwich versions. We extend the tools developed for NP-complete reductions of sandwich partition problems obtaining the classification into NP-complete for some external constraint 4 nonempty part sandwich problems. On the other hand and additionally, we propose a general strategy for defining polynomial reductions from the 2K2-partition problem to several external constraint 4 nonempty part sandwich problems, defining a class of 2K2-hard problems. Finally, we discuss the complexity of the Skew Partition Sandwich Problem. 相似文献
254.
The number of Sidon sets and the maximum size of Sidon sets contained in a sparse random set of integers
下载免费PDF全文
![点击此处可从《Random Structures and Algorithms》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yoshiharu Kohayakawa Sang June Lee Vojtěch Rödl Wojciech Samotij 《Random Structures and Algorithms》2015,46(1):1-25
A set A of non‐negative integers is called a Sidon set if all the sums , with and a1, , are distinct. A well‐known problem on Sidon sets is the determination of the maximum possible size F(n) of a Sidon subset of . Results of Chowla, Erd?s, Singer and Turán from the 1940s give that . We study Sidon subsets of sparse random sets of integers, replacing the ‘dense environment’ by a sparse, random subset R of , and ask how large a subset can be, if we require that S should be a Sidon set. Let be a random subset of of cardinality , with all the subsets of equiprobable. We investigate the random variable , where the maximum is taken over all Sidon subsets , and obtain quite precise information on for the whole range of m, as illustrated by the following abridged version of our results. Let be a fixed constant and suppose . We show that there is a constant such that, almost surely, we have . As it turns out, the function is a continuous, piecewise linear function of a that is non‐differentiable at two ‘critical’ points: a = 1/3 and a = 2/3. Somewhat surprisingly, between those two points, the function is constant. Our approach is based on estimating the number of Sidon sets of a given cardinality contained in [n]. Our estimates also directly address a problem raised by Cameron and Erd?s (On the number of sets of integers with various properties, Number theory (Banff, AB, 1988), de Gruyter, Berlin, 1990, pp. 61–79). © 2013 Wiley Periodicals, Inc. Random Struct. Alg., 46, 1–25, 2015 相似文献
255.
How many T‐tessellations on k lines? Existence of associated Gibbs measures on bounded convex domains
下载免费PDF全文
![点击此处可从《Random Structures and Algorithms》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jonas Kahn 《Random Structures and Algorithms》2015,47(3):561-587
The paper bounds the number of tessellations with T‐shaped vertices on a fixed set of k lines: tessellations are efficiently encoded, and algorithms retrieve them, proving injectivity. This yields existence of a completely random T‐tessellation, as defined by Kiêu et al. (Spat Stat 6 (2013) 118–138), and of its Gibbsian modifications. The combinatorial bound is sharp, but likely pessimistic in typical cases. © 2014 Wiley Periodicals, Inc. Random Struct. Alg., 47, 561–587, 2015 相似文献
256.
Failure probability estimation with differently sized reference products for semiconductor burn‐in studies
下载免费PDF全文
![点击此处可从《商业与工业应用随机模型》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A burn‐in study is applied to demonstrate compliance with a targeted early life failure probability of semiconductor products. This is achieved by investigating a sample of the produced chips for reliability‐relevant failures. Usually, a burn‐in study is carried out for a specific reference product with the aim to scale the reference product's failure probability to follower products with different chip sizes. It also appears, however, that there are multiple, differently sized reference products for which burn‐in studies are performed. In this paper, we present a novel model for estimating the failure probability of a chip, which is capable of handling burn‐in studies on multiple reference products. We discuss the model from a combinatorial and a Bayesian perspective; both approaches are shown to provide more accurate estimation results in comparison with a simple area‐based approach. Moreover, we discuss the required modifications of the model if the observed failures are tackled by countermeasures implemented in the chip production process. Finally, the model is applied to the problem of determining the failure probabilities of follower products on the basis of multiple reference products. 相似文献
257.
258.