全文获取类型
收费全文 | 12651篇 |
免费 | 2282篇 |
国内免费 | 1890篇 |
专业分类
化学 | 5249篇 |
晶体学 | 100篇 |
力学 | 734篇 |
综合类 | 155篇 |
数学 | 3002篇 |
物理学 | 7583篇 |
出版年
2024年 | 17篇 |
2023年 | 110篇 |
2022年 | 235篇 |
2021年 | 290篇 |
2020年 | 361篇 |
2019年 | 278篇 |
2018年 | 295篇 |
2017年 | 337篇 |
2016年 | 401篇 |
2015年 | 455篇 |
2014年 | 671篇 |
2013年 | 1039篇 |
2012年 | 681篇 |
2011年 | 888篇 |
2010年 | 762篇 |
2009年 | 912篇 |
2008年 | 985篇 |
2007年 | 1000篇 |
2006年 | 873篇 |
2005年 | 797篇 |
2004年 | 579篇 |
2003年 | 670篇 |
2002年 | 591篇 |
2001年 | 499篇 |
2000年 | 470篇 |
1999年 | 425篇 |
1998年 | 354篇 |
1997年 | 299篇 |
1996年 | 254篇 |
1995年 | 183篇 |
1994年 | 185篇 |
1993年 | 126篇 |
1992年 | 130篇 |
1991年 | 107篇 |
1990年 | 63篇 |
1989年 | 78篇 |
1988年 | 56篇 |
1987年 | 52篇 |
1986年 | 27篇 |
1985年 | 56篇 |
1984年 | 32篇 |
1983年 | 22篇 |
1982年 | 44篇 |
1981年 | 21篇 |
1980年 | 18篇 |
1979年 | 20篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 14篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
61.
超子中子星性质的温度效应 总被引:2,自引:0,他引:2
从相对论平均场理论出发,考虑核子、超子和介子的相互作用,研究了温度对中子星组成粒子、状态方程和中子星质量等的影响.发现温度越高,超子在中子星内部出现时的重子数密度越低.当密度较高时,中子星的核心区主要由超子组成,即中子星转变成以奇异粒子为主要成分的超子星,并且这种转变受到温度的影响,温度越高,转变密度越低.由于超子的出现,中子星核心高密度区域的状态方程,对于不同温度,差别不大,所以有限温度中子星的最大质量都在1.8M⊙附近.这与观测结果相符. 相似文献
62.
构造了第孙中禹种强度不等的非对称三态叠加多模叠加态光场|ψ1(ABC)〉q.利用多模压缩态理论研究了态|ψ1(ABC)〉q第一正交分量高次和压缩.结果发现:①当构成态|ψ1(ABC)〉q的三个多模相干态光场的强度不相等时,在一定条件下,态|ψ1(ABC)〉q的第一正交分量可出现任意幂次的高次和压缩.②当上述的三个多模相干态光场强度相等时,态|ψ1(ABC)〉q的第一正交分量的高次和压缩现象消失.在这种情况下,态|ψ1(ABC)〉q的第一正交分量恒处于NH最小测不准态. 相似文献
63.
This work is concerned with the maximum principle for optimal control problem governed by magnetohydrodynamic equations, which describe the motion of a viscous incompressible conducting fluid in a magnetic field and consist of a subtle coupling of the Navier-Stokes equation of viscous incompressible fluid flow and the Maxwell equation of electromagnetic field. An integral type state constraint is considered. 相似文献
64.
Based on the newly constructed two mutually conjugate 3-mode entangled states of continuum variablesin three-mode Fock space we introduce entangled fractional Fourier transform (EFFT) for the tripartite entangled staterepresentations, which are not a direct product of three 1-dimensional FFTs. The eigenmodes of EFFT are obtained,which is different from the usual Hermite polynomials. The EFFT of the three-mode squeezed state is derived. 相似文献
65.
Rafał Bocian Thorsten Holm Andrzej Skowroński 《Central European Journal of Mathematics》2004,2(1):67-75
Auslander’s representation dimension measures how far a finite dimensional algebra is away from being of finite representation
type. In [1], M. Auslander proved that a finite dimensional algebra A is of finite representation type if and only if the representation dimension of A is at most 2. Recently, R. Rouquier proved that there are finite dimensional algebras of an arbitrarily large finite representation
dimension. One of the exciting open problems is to show that all finite dimensional algebras of tame representation type have
representation dimension at most 3. We prove that this is true for all domestic weakly symmetric algebras over algebraically
closed fields having simply connected Galois coverings. 相似文献
66.
M. B. Litvinova 《Journal of Applied Spectroscopy》2004,71(1):143-146
It has been established that undoped gallium crystals exhibit anti-Stokes radiation with energy corresponding to the interband recombination of these crystals. Its appearance is most probably determined by EL2 defects, and its intensity depends on the product of the cross sections for photoionization of electrons and the holes from these defects. 相似文献
67.
68.
We show that functions which are invariant for suitable product semigroups (one of which is a quasi-Poisson semigroup on a general state space) decompose into a singular eigen-function and a mixture of products of minimal eigen-functions. 相似文献
69.
Algorithm for Optimal Triangulations in Scattered Data Representation and Implementation 总被引:2,自引:0,他引:2
Scattered data collected at sample points may be used to determine simple functions to best fit the data. An ideal choice for these simple functions is bivariate splines. Triangulation of the sample points creates partitions over which the bivariate splines may be defined. But the optimality of the approximation is dependent on the choice of triangulation. An algorithm, referred to as an Edge Swapping Algorithm, has been developed to transform an arbitrary triangulation of the sample points into an optimal triangulation for representation of the scattered data. A Matlab package has been completed that implements this algorithm for any triangulation on a given set of sample points. 相似文献
70.
Yanghyun Byun 《Foundations of Physics》2004,34(6):987-1003
We consider a representation of the state reduction which depends neither on its reality nor on the details of when and how it emerges. Then by means of the representation we find necessary conditions, even if not the sufficient ones, for a decomposition of the state vector space to be a solution to the basis problem. The conditions are that the decomposition should be Lorentz invariant and orthogonal and that the associated projections should be continuous. They are shown to be able to determine a decomposition in each of a few examples considered if the other circumstances are taken into account together. 相似文献