全文获取类型
收费全文 | 27964篇 |
免费 | 5189篇 |
国内免费 | 2659篇 |
专业分类
化学 | 7575篇 |
晶体学 | 185篇 |
力学 | 1683篇 |
综合类 | 327篇 |
数学 | 5682篇 |
物理学 | 11025篇 |
无线电 | 9335篇 |
出版年
2024年 | 48篇 |
2023年 | 302篇 |
2022年 | 508篇 |
2021年 | 714篇 |
2020年 | 849篇 |
2019年 | 739篇 |
2018年 | 729篇 |
2017年 | 964篇 |
2016年 | 1094篇 |
2015年 | 1160篇 |
2014年 | 1634篇 |
2013年 | 2229篇 |
2012年 | 1816篇 |
2011年 | 2024篇 |
2010年 | 1693篇 |
2009年 | 1740篇 |
2008年 | 1975篇 |
2007年 | 1943篇 |
2006年 | 1772篇 |
2005年 | 1560篇 |
2004年 | 1290篇 |
2003年 | 1321篇 |
2002年 | 1152篇 |
2001年 | 1007篇 |
2000年 | 883篇 |
1999年 | 782篇 |
1998年 | 585篇 |
1997年 | 556篇 |
1996年 | 461篇 |
1995年 | 362篇 |
1994年 | 315篇 |
1993年 | 240篇 |
1992年 | 207篇 |
1991年 | 187篇 |
1990年 | 124篇 |
1989年 | 138篇 |
1988年 | 88篇 |
1987年 | 84篇 |
1986年 | 55篇 |
1985年 | 104篇 |
1984年 | 62篇 |
1983年 | 34篇 |
1982年 | 65篇 |
1981年 | 46篇 |
1980年 | 20篇 |
1979年 | 37篇 |
1978年 | 18篇 |
1977年 | 20篇 |
1976年 | 21篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
161.
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
162.
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
163.
164.
Shui Cao ZHENG Huo Nan LIN Di He HU 《数学学报(英文版)》2005,21(5):1137-1148
In this paper, we investigate the Hausdorff measure for level sets of N-parameter Rd-valued stable processes, and develop a means of seeking the exact Hausdorff measure function for level sets of N-parameter Rd-valued stable processes. We show that the exact Hausdorff measure function of level sets of N-parameter Rd-valued symmetric stable processes of index α is Ф(r) = r^N-d/α (log log l/r)d/α when Nα 〉 d. In addition, we obtain a sharp lower bound for the Hausdorff measure of level sets of general (N, d, α) strictly stable processes. 相似文献
165.
In this paper, we exhibit a unified treatment of the mixed initial boundary value problem for second order (in time) parabolic linear differential equations in Banach spaces, whose boundary conditions are of a dynamical nature. Results regarding existence, uniqueness, continuous dependence (on initial data) and regularity of classical and strict solutions are established. Moreover, several examples are given as samples for possible applications.
166.
Carl M. Bender 《Czechoslovak Journal of Physics》2004,54(1):13-28
The Hamiltonian H specifies the energy levels and the time evolution of a quantum theory. It is an axiom of quantum mechanics that H be Hermitian. The Hermiticity of H guarantees that the energy spectrum is real and that the time evolution is unitary (probability preserving). In this talk we investigate an alternative formulation of quantum mechanics in which the mathematical requirement of Hermiticity is replaced by the more physically transparent condition of space-time reflection (PT) symmetry. We show that if the PT symmetry of a Hamiltonian H is not broken, then the spectrum of H is real. Examples of PT-symmetric non-Hermitian Hamiltonians are H=p
2+ix
3 and H=p
2-x
4. The crucial question is whether PT-symmetric Hamiltonians specify physically acceptable quantum theories in which the norms of states are positive and the time evolution is unitary. The answer is that a Hamiltonian that has an unbroken PT symmetry also possesses a physical symmetry that we call C. Using C, we show how to construct an inner product whose associated norm is positive definite. The result is a new class of fully consistent complex quantum theories. Observables exhibit CPT symmetry, probabilities are positive, and the dynamics is governed by unitary time evolution. 相似文献
167.
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
168.
169.
利用拉曼型的Jaynes-Cummings模型传送两比特的未知原子态 总被引:6,自引:3,他引:3
实现量子态的隐形传送、尤其是多比特量子态的隐形传送在量子信息领域中有非常重要的作用,提出了一种隐形传送两比特未知原子态的方案,在此方案中,用两个两粒子纠缠态代替一个三粒子纠缠态作为量子信道,而且此方案可推广到隐形传送N比特的未知原子态。 相似文献
170.
In this paper, we investigate the exact distribution of the waiting time for ther-th ℓ-overlapping occurrence of success-runs of a specified length in a sequence of two state Markov dependent trials. The
probability generating functions are derived explicitly, and as asymptotic results, relationships of a negative binomial distribution
of orderk and an extended Poisson distribution of orderk are discussed. We provide further insights into the run-related problems from the viewpoint of the ℓ-overlapping enumeration
scheme. We also study the exact distribution of the number of ℓ-overlapping occurrences of success-runs in a fixed number
of trials and derive the probability generating functions. The present work extends several properties of distributions of
orderk and leads us a new type of geneses of the discrete distributions. 相似文献