全文获取类型
收费全文 | 1592篇 |
免费 | 130篇 |
国内免费 | 197篇 |
专业分类
化学 | 47篇 |
晶体学 | 2篇 |
力学 | 132篇 |
综合类 | 31篇 |
数学 | 851篇 |
物理学 | 856篇 |
出版年
2023年 | 9篇 |
2022年 | 21篇 |
2021年 | 19篇 |
2020年 | 29篇 |
2019年 | 31篇 |
2018年 | 36篇 |
2017年 | 35篇 |
2016年 | 32篇 |
2015年 | 30篇 |
2014年 | 56篇 |
2013年 | 119篇 |
2012年 | 61篇 |
2011年 | 95篇 |
2010年 | 66篇 |
2009年 | 92篇 |
2008年 | 100篇 |
2007年 | 94篇 |
2006年 | 99篇 |
2005年 | 88篇 |
2004年 | 106篇 |
2003年 | 99篇 |
2002年 | 86篇 |
2001年 | 70篇 |
2000年 | 55篇 |
1999年 | 60篇 |
1998年 | 57篇 |
1997年 | 43篇 |
1996年 | 30篇 |
1995年 | 20篇 |
1994年 | 26篇 |
1993年 | 19篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 6篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1987年 | 10篇 |
1986年 | 17篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1972年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有1919条查询结果,搜索用时 671 毫秒
1.
A new unified electroweak model is proposed in this paper. In this unified electroweak model, Higgsmechanism is not used, so no Higgs particle exists in the model. In order to keep the masses of intermediate gaugebosons non-zero, two sets of gauge fields will be introduced. In order to introduce symmetry breaking and to help tointroduce the masses of all fields, a vacuum potential is needed. Except for those terms concerning Higgs particle, thefundamental dynamical properties of this model are similar to those of the standard model. And in a proper limit, thismodel will approximately return to the standard model. The purpose of this paper is not to say that the Higgs particledoes not exist in Nature, it is only to prove that, without a Higgs particle, we can also set up a unified electroweak modelwhich is consistent with present experiments. 相似文献
2.
主要介绍了一个引理,这个引理奠定了K4-同胚图K4(α,1,1,δ,ε,η)色性研究的基础。 相似文献
3.
4.
用于强磁场的快响应真空规的研制进展 总被引:2,自引:2,他引:0
研制了能在强磁场、强干扰环境下工作的快响应真空电离规(快规),用于对HL 2A装置偏滤器室和等离子体附近的中性粒子密度和通量进行原位测量。介绍了快规的结构、工作原理、设计要点以及实验结果。在无磁场的情况下,快规对气体压强的测量范围为6.4×10-6~0.15Pa,在1×10-5~0.15Pa范围内,快规收集极离子流与发射电子流之比与气压保持良好线性关系;在0 15T的磁场下,快规的规管常数未发生显著变化,在规管对称轴与磁力线的夹角小于15o时,规管常数的变化小于10%。 相似文献
5.
6.
We study the geometry of determinant line bundles associated with Dirac operators on compact odd-dimensional manifolds. Physically, these arise as (local) vacuum line bundles in quantum gauge theory. We give a simplified derivation of the commutator anomaly formula using a construction based on noncyclic trace extensions and associated nonmultiplicative renormalized determinants. 相似文献
7.
WU Ke ZHAO Weizhong & GUO Hanying Department of Mathematics Capital Normal University Beijing China Institute of Theoretical Physics Chinese Academy of Sciences Beijing China 《中国科学A辑(英文版)》2006,(11)
In a way similar to the continuous case formally, we define in different but equivalent manners the difference discrete connection and curvature on discrete vector bundle over the regular lattice as base space. We deal with the difference operators as the discrete counterparts of the derivatives based upon the differential calculus on the lattice. One of the definitions can be extended to the case over the random lattice. We also discuss the relation between our approach and the lattice gauge theory and apply to the discrete integrable systems. 相似文献
8.
The values of the Higgs mass are obtained for two possibilities of extending the standard model in a way compatible with the existence of a noncommutative structure at high energies. We assume the existence of a big desert between the low energy electroweak scale and the high energy scale Λ=1.1×1017 GeV, where noncommutative features become relevant. We conclude that it is extremely difficult to depart from the Higgs mass value obtained from noncommutative geometry for the standard model with three generations only. 相似文献
9.
Weaving is a matrix construction developed in 1990 for the purpose of obtaining new weighing matrices. Hadamard matrices obtained by weaving have the same orders as those obtained using the Kronecker product, but weaving affords greater control over the internal structure of matrices constructed, leading to many new Hadamard equivalence classes among these known orders. It is known that different classes of Hadamard matrices may have different maximum excess. We explain why those classes with smaller excess may be of interest, apply the method of weaving to explore this question, and obtain constructions for new Hadamard matrices with maximum excess in their respective classes. With this method, we are also able to construct Hadamard matrices of near‐maximal excess with ease, in orders too large for other by‐hand constructions to be of much value. We obtain new lower bounds for the maximum excess among Hadamard matrices in some orders by constructing candidates for the largest excess. For example, we construct a Hadamard matrix with excess 1408 in order 128, larger than all previously known values. We obtain classes of Hadamard matrices of order 96 with maximum excess 912 and 920, which demonstrates that the maximum excess for classes of that order may assume at least three different values. Since the excess of a woven Hadamard matrix is determined by the row sums of the matrices used to weave it, we also investigate the properties of row sums of Hadamard matrices and give lists of them in small orders. © 2004 Wiley Periodicals, Inc. J Combin Designs 12: 233–255, 2004. 相似文献
10.
Elena Castellani 《International Journal of Theoretical Physics》2004,43(6):1503-1514
We examine the relevance of Dirac's view on the use of transformation theory and invariants in modern physics to current reflections on the meaning of physical symmetries, especially gauge symmetries. 相似文献