全文获取类型
收费全文 | 2258篇 |
免费 | 240篇 |
国内免费 | 212篇 |
专业分类
化学 | 352篇 |
晶体学 | 18篇 |
力学 | 237篇 |
综合类 | 70篇 |
数学 | 1317篇 |
物理学 | 716篇 |
出版年
2024年 | 5篇 |
2023年 | 18篇 |
2022年 | 62篇 |
2021年 | 53篇 |
2020年 | 36篇 |
2019年 | 54篇 |
2018年 | 44篇 |
2017年 | 69篇 |
2016年 | 66篇 |
2015年 | 52篇 |
2014年 | 98篇 |
2013年 | 171篇 |
2012年 | 96篇 |
2011年 | 123篇 |
2010年 | 117篇 |
2009年 | 131篇 |
2008年 | 147篇 |
2007年 | 125篇 |
2006年 | 118篇 |
2005年 | 114篇 |
2004年 | 86篇 |
2003年 | 122篇 |
2002年 | 88篇 |
2001年 | 79篇 |
2000年 | 78篇 |
1999年 | 74篇 |
1998年 | 69篇 |
1997年 | 48篇 |
1996年 | 45篇 |
1995年 | 42篇 |
1994年 | 32篇 |
1993年 | 33篇 |
1992年 | 31篇 |
1991年 | 28篇 |
1990年 | 18篇 |
1989年 | 20篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1973年 | 3篇 |
排序方式: 共有2710条查询结果,搜索用时 218 毫秒
971.
Hartmut Laue 《代数通讯》2013,41(11):4705-4710
We give a simplified proof and a module extension of Du's theorem on the upper central chains of the circle group and of the associated Lie algebra of a radical ring. 相似文献
972.
In the framework of evidence theory, one of the open and crucial issues is how to determine the basic probability assignment (BPA), which is directly related to whether the decision result is correct. This paper proposes a novel method for obtaining BPA based on Adaboost. The method uses training data to generate multiple strong classifiers for each attribute model, which is used to determine the BPA of the singleton proposition since the weights of classification provide necessary information for fundamental hypotheses. The BPA of the composite proposition is quantified by calculating the area ratio of the singleton proposition’s intersection region. The recursive formula of the area ratio of the intersection region is proposed, which is very useful for computer calculation. Finally, BPAs are combined by Dempster’s rule of combination. Using the proposed method to classify the Iris dataset, the experiment concludes that the total recognition rate is 96.53% and the classification accuracy is 90% when the training percentage is 10%. For the other datasets, the experiment results also show that the proposed method is reasonable and effective, and the proposed method performs well in the case of insufficient samples. 相似文献
973.
Sui Sun Cheng Shao Yuan Huang 《International Journal of Mathematical Education in Science & Technology》2013,44(7):950-964
Given a quadratic polynomial with complex coefficients, necessary and sufficient conditions are found in terms of the coefficients such that all its roots have absolute values <1. 相似文献
974.
Mark Pedigo 《代数通讯》2013,41(11):4462-4475
In their article, “On the derived subgroup of the free nilpotent groups of finite rank” R. D. Blyth, P. Moravec, and R. F. Morse describe the structure of the derived subgroup of a free nilpotent group of finite rank n as a direct product of a nonabelian group and a free abelian group, each with a minimal generating set of cardinality that is a given function of n. They apply this result to computing the nonabelian tensor squares of the free nilpotent groups of finite rank. We generalize their main result to investigate the structure of the other terms of the lower central series of a free nilpotent group of finite rank, each again described as a direct product of a nonabelian group and a free abelian group. In order to compute the ranks of the free abelian components and the size of minimal generating sets for the nonabelian components we introduce what we call weight partitions. 相似文献
975.
This paper is devoted to construct a family of fifth degree cubature formulae for n-cube with symmetric measure and n-dimensional spherically symmetrical region. The formula forn-cube contains at most n2+5n+3 points and for n-dimensional spherically symmetrical region contains only n2+3n+3 points. Moreover, the numbers can be reduced to n2+3n+1 and n2+n+1 if n=7 respectively, the latter of which is minimal. 相似文献
976.
In this paper, we present a new trust region algorithm for a nonlinear bilevel programming problem by solving a series of its linear or quadratic approximation subproblems. For the nonlinear bilevel programming problem in which the lower level programming problem is a strongly convex programming problem with linear constraints, we show that each accumulation point of the iterative sequence produced by this algorithm is a stationary point of the bilevel programming problem. 相似文献
977.
Let X, X1 , X2 , ··· be a sequence of nondegenerate i.i.d. random variables with zero means, which is in the domain of attraction of the normal law. Let {a ni , 1≤i≤n, n≥1} be an array of real numbers with some suitable conditions. In this paper, we show that a central limit theorem for self-normalized weighted sums holds. We also deduce a version of ASCLT for self-normalized weighted sums. 相似文献
978.
Christophe A. N. Biscio Jesper Møller 《Journal of computational and graphical statistics》2013,22(3):671-681
We start with a simple introduction to topological data analysis where the most popular tool is called a persistence diagram. Briefly, a persistence diagram is a multiset of points in the plane describing the persistence of topological features of a compact set when a scale parameter varies. Since statistical methods are difficult to apply directly on persistence diagrams, various alternative functional summary statistics have been suggested, but either they do not contain the full information of the persistence diagram or they are two-dimensional functions. We suggest a new functional summary statistic that is one-dimensional and hence easier to handle, and which under mild conditions contains the full information of the persistence diagram. Its usefulness is illustrated in statistical settings concerned with point clouds and brain artery trees. The supplementary materials include additional methods and examples, technical details, and the R code used for all examples. 相似文献
979.
980.