全文获取类型
收费全文 | 2303篇 |
免费 | 198篇 |
国内免费 | 127篇 |
专业分类
化学 | 279篇 |
晶体学 | 9篇 |
力学 | 113篇 |
综合类 | 58篇 |
数学 | 1498篇 |
物理学 | 671篇 |
出版年
2024年 | 5篇 |
2023年 | 33篇 |
2022年 | 53篇 |
2021年 | 49篇 |
2020年 | 63篇 |
2019年 | 59篇 |
2018年 | 63篇 |
2017年 | 92篇 |
2016年 | 99篇 |
2015年 | 63篇 |
2014年 | 158篇 |
2013年 | 179篇 |
2012年 | 102篇 |
2011年 | 109篇 |
2010年 | 114篇 |
2009年 | 156篇 |
2008年 | 151篇 |
2007年 | 153篇 |
2006年 | 118篇 |
2005年 | 106篇 |
2004年 | 80篇 |
2003年 | 82篇 |
2002年 | 77篇 |
2001年 | 69篇 |
2000年 | 73篇 |
1999年 | 61篇 |
1998年 | 54篇 |
1997年 | 36篇 |
1996年 | 24篇 |
1995年 | 14篇 |
1994年 | 22篇 |
1993年 | 19篇 |
1992年 | 6篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 9篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有2628条查询结果,搜索用时 0 毫秒
21.
The syntenic distance between two species is the minimum number of fusions, fissions, and translocations required to transform one genome into the other. The linear syntenic distance, a restricted form of this model, has been shown to be close to the syntenic distance. Both models are computationally difficult to compute and have resisted efficient approximation algorithms with non-trivial performance guarantees. In this paper, we prove that many useful properties of syntenic distance carry over to linear syntenic distance. We also give a reduction from the general linear synteny problem to the question of whether a given instance can be solved using the maximum possible number of translocations. Our main contribution is an algorithm exactly computing linear syntenic distance in nested instances of the problem. This is the first polynomial time algorithm exactly solving linear synteny for a non-trivial class of instances. It is based on a novel connection between the syntenic distance and a scheduling problem that has been studied in the operations research literature. 相似文献
22.
Frank N. Proske Madan L. Puri 《Proceedings of the American Mathematical Society》2003,131(9):2937-2944
In this article we prove a strong law of large numbers for Borel measurable nonseparably valued random elements in the case of generalized random sets.
23.
24.
In Homma M and Kim SJ [2], the authors considered two-point codes on a Hermitian curve defined over fields of odd characteristic.
In this paper, we study the geometry of a Hermitian curve over fields of even characteristic and classify the two-point codes
whose minimum distances agree with the designed ones. 相似文献
25.
商标数据库存储模式及其检索算法研究 总被引:6,自引:0,他引:6
依据商标专家的先验知识和基于内容的图像检索技术,提出了一种新的商标库存储结构,并依据该存储结构设计了以三级检索算法为核心的实用商标登记注册管理系统,对于检索算法,一级检索采用人工确认,二级检索采用傅立叶描述子作为边缘特征向量,三级检索采用hu不变矩组作为矩特征向量,从而达到提高商标申请注册中的检索速度和查准率。 相似文献
26.
We define a classical probability analogue of Voiculescu's free entropy dimension that we shall call the classical probability entropy dimension of a probability measure on Rn. We show that the classical probability entropy dimension of a measure is related with diverse other notions of dimension. First, it can be viewed as a kind of fractal dimension. Second, if one extends Bochner's inequalities to a measure by requiring that microstates around this measure asymptotically satisfy the classical Bochner's inequalities, then we show that the classical probability entropy dimension controls the rate of increase of optimal constants in Bochner's inequality for a measure regularized by convolution with the Gaussian law as the regularization is removed. We introduce a free analogue of the Bochner inequality and study the related free entropy dimension quantity. We show that it is greater or equal to the non-microstates free entropy dimension. 相似文献
27.
Semilinear Differential Inclusions in Separable Banach SpacesXueXingmei(薛星美)andSongGuozhu(宋国柱)(DepartmentofMathematics,Nanjin... 相似文献
28.
关于Gerber不等式的一个猜想 总被引:4,自引:1,他引:3
本文证明了陈计-单墫关于Gerber不等式的一个猜想,作为其应用,导出了单形内一点到顶点的距离与到面的距离的两个不等式. 相似文献
29.
In a general measure-theoretic context, it is proved that the action of a stochastic map on a pair of probability distributions can be characterized by the criterion of decreasing mixing distance. 相似文献
30.
Interatomic distances in the transition state were estimated for the reactions of radical abstraction: H· + H2, H· + HCl, H· + CH4, N·H2 + NH3, HO· + H2O, HO2
· + HOOH, and C·H3 + SiH4. The calculation was performed by the quantum-chemical density functional method or coupled clusters method (QCH), as well as by the methods of intersecting parabolas (IPM) and Morse curves (IMM), using experimental data (activation energies and reaction enthalpies). The results of the latter two methods are close to the quantum-chemical calculation and differ only by the increment a: r(IPM or IMM) = a + r(QCH), where a = –4.5·10–12 m for IPM and a = +1.9·10–12 m for IMM. 相似文献