全文获取类型
收费全文 | 25628篇 |
免费 | 5794篇 |
国内免费 | 2624篇 |
专业分类
化学 | 8433篇 |
晶体学 | 325篇 |
力学 | 1628篇 |
综合类 | 206篇 |
数学 | 2332篇 |
物理学 | 14417篇 |
无线电 | 6705篇 |
出版年
2024年 | 51篇 |
2023年 | 350篇 |
2022年 | 620篇 |
2021年 | 784篇 |
2020年 | 1011篇 |
2019年 | 854篇 |
2018年 | 830篇 |
2017年 | 1031篇 |
2016年 | 1157篇 |
2015年 | 1128篇 |
2014年 | 1566篇 |
2013年 | 1975篇 |
2012年 | 1841篇 |
2011年 | 1898篇 |
2010年 | 1648篇 |
2009年 | 1676篇 |
2008年 | 1654篇 |
2007年 | 1614篇 |
2006年 | 1584篇 |
2005年 | 1347篇 |
2004年 | 1334篇 |
2003年 | 1186篇 |
2002年 | 1156篇 |
2001年 | 882篇 |
2000年 | 798篇 |
1999年 | 625篇 |
1998年 | 566篇 |
1997年 | 427篇 |
1996年 | 391篇 |
1995年 | 314篇 |
1994年 | 294篇 |
1993年 | 208篇 |
1992年 | 195篇 |
1991年 | 160篇 |
1990年 | 141篇 |
1989年 | 141篇 |
1988年 | 106篇 |
1987年 | 63篇 |
1986年 | 72篇 |
1985年 | 69篇 |
1984年 | 55篇 |
1983年 | 28篇 |
1982年 | 43篇 |
1981年 | 32篇 |
1980年 | 23篇 |
1979年 | 16篇 |
1978年 | 26篇 |
1977年 | 13篇 |
1976年 | 15篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
181.
M. Feng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):371-377
The Raman interaction of a ultracold ion trapped with two travelling wave lasers is studied analytically with series solutions,
in the absence of the rotating wave approximation (RWA) and without restrictions of both the Lamb-Dicke limit and the weak
excitation regime. The comparison is made between our solutions and those obtained under the RWA in order to demonstrate the
validity region of the RWA. As a practical example, the preparation of Schr?dinger-cat states is proposed beyond the weak
excitation regime, using our calculations.
Received 12 March 2001 and Received in final form 16 October 2001 相似文献
182.
Deák L. Bottyán L. Major M. Nagy D. L. Spiering H. Szilágyi E. Tanczikó F. 《Hyperfine Interactions》2002,144(1-4):45-52
Hyperfine Interactions - Synchrotron Mössbauer Reflectometry (SMR), the grazing incidence nuclear resonant scattering of synchrotron radiation, can be applied to perform depth-selective phase... 相似文献
183.
Piotr Biler 《Reports on Mathematical Physics》2003,52(2):205-225
We study asymptotic properties of solutions to an extension to arbitrary dimensions of the astrophysical model proposed by Chavanis et al. to explain phenomena of gravitational collapse in clouds of self-gravitating particles. In particular, we show that in the two-dimensional case the solutions can be continued to global ones, while in three space dimensions large data of negative energy blow up in a finite time. Relations between isothermal, Streater's energy-transport and the present models are also studied. 相似文献
184.
The methods for the few-body system are introduced to investigate the states of the barrier Li quantumdots (QDs) in an arbitrary strength of magnetic field. The configuration, which consists of a positive ion located on thez-axis at a distance d from the two-dimensional QD plane (the x-y plane) and three electrons in the dot plane boundby the positive ion, is called a barrier Li center. The system, which consists of three electrons in the dot plane bound bythe ion, is called a barrier Li QD. The dependence of energy of the state of the barrier Li QD on an external magneticfield B and the distance d is obtained. The angular momentum L of the ground states is found to jump not only withthe variation of B but also with d. 相似文献
185.
We consider toy cosmological models in which a classical, homogeneous, spinor field provides a dominant or sub-dominant contribution to the energy-momentum tensor of a flat Friedmann-Robertson-Walker universe. We find that, if such a field were to exist, appropriate choices of the spinor self-interaction would generate a rich variety of behaviors, quite different from their widely studied scalar field counterparts. We first discuss solutions that incorporate a stage of cosmic inflation and estimate the primordial spectrum of density perturbations seeded during such a stage. Inflation driven by a spinor field turns out to be unappealing as it leads to a blue spectrum of perturbations and requires considerable fine-tuning of parameters. We next find that, for simple, quartic spinor self-interactions, non-singular cyclic cosmologies exist with reasonable parameter choices. These solutions might eventually be incorporated into a successful past- and future-eternal cosmological model free of singularities. In an Appendix, we discuss the classical treatment of spinors and argue that certain quantum systems might be approximated in terms of such fields. 相似文献
186.
Gerhard Starke 《Numerische Mathematik》1997,78(1):103-117
Summary. The convergence rate of Krylov subspace methods for the solution of nonsymmetric systems of linear equations, such as GMRES
or FOM, is studied. Bounds on the convergence rate are presented which are based on the smallest real part of the field of
values of the coefficient matrix and of its inverse. Estimates for these quantities are available during the iteration from
the underlying Arnoldi process. It is shown how these bounds can be used to study the convergence properties, in particular,
the dependence on the mesh-size and on the size of the skew-symmetric part, for preconditioners for finite element discretizations
of nonsymmetric elliptic boundary value problems. This is illustrated for the hierarchical basis and multilevel preconditioners
which constitute popular preconditioning strategies for such problems.
Received May 3, 1996 相似文献
187.
188.
分形方法用于有噪图像边缘检测的研究 总被引:10,自引:0,他引:10
本文研究了加性高斯白噪声对于基于离散分数布朗随机场模型图像分形维数估计的影响,并将分形方法用于图像边缘检测,指出在加性高斯白噪声的情况下,分形方法用于图像边缘检测较之经典的基于梯度运算的边缘检测方法有好的抗噪性能,同时又能检测比较丰富的图像边缘细节。 相似文献
189.
190.
双原子系统中原子非经典特性与光场非经典特性的关联 总被引:2,自引:0,他引:2
本文研究了双原子与双模光场相互作用系统中,双原子分崩离析有压缩与双模光场二阶压缩间的对称关系。揭示了原子间关系和光场模间关联的转换特性,并探讨了失谐量,耦和常数对原子非经典特性与光场非经典特性间关联的影响。 相似文献