全文获取类型
收费全文 | 3825篇 |
免费 | 667篇 |
国内免费 | 1605篇 |
专业分类
化学 | 2038篇 |
晶体学 | 15篇 |
力学 | 164篇 |
综合类 | 201篇 |
数学 | 2215篇 |
物理学 | 1464篇 |
出版年
2024年 | 25篇 |
2023年 | 103篇 |
2022年 | 102篇 |
2021年 | 103篇 |
2020年 | 101篇 |
2019年 | 57篇 |
2018年 | 63篇 |
2017年 | 80篇 |
2016年 | 117篇 |
2015年 | 150篇 |
2014年 | 310篇 |
2013年 | 219篇 |
2012年 | 334篇 |
2011年 | 375篇 |
2010年 | 297篇 |
2009年 | 301篇 |
2008年 | 346篇 |
2007年 | 268篇 |
2006年 | 270篇 |
2005年 | 287篇 |
2004年 | 327篇 |
2003年 | 231篇 |
2002年 | 222篇 |
2001年 | 199篇 |
2000年 | 132篇 |
1999年 | 148篇 |
1998年 | 131篇 |
1997年 | 150篇 |
1996年 | 97篇 |
1995年 | 97篇 |
1994年 | 80篇 |
1993年 | 92篇 |
1992年 | 75篇 |
1991年 | 57篇 |
1990年 | 64篇 |
1989年 | 47篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有6097条查询结果,搜索用时 15 毫秒
971.
972.
为了控制反射式旋转对称光学系统中的偏振效应,对该类系统中的偏振像差进行了分析。在偏振像差理论的基础上,通过偏振光线追迹的方法,导出反射式旋转对称光学系统的偏振像差的计算公式,提出了反射界面产生的偏振像差的影响因子,对影响其偏振像差的因素进行了分析。实例分析结果表明,对于具有宽光谱、大入射角、大视场等特点的反射式旋转对称光学系统,要想提高其光学系统的性能,必须控制光学系统的偏振像差。提出尽可能减小入射角的大小,并通过薄膜设计减小偏振分离来降低系统中的偏振效应,是控制反射式旋转对称光学系统中的偏振像差的有效措施。 相似文献
973.
MI Ai-Jun ZUO Wei LI Zeng-Hua Umberto Lombardo 《理论物理通讯》2009,51(6):1113-1116
The 3 P F2 superfluidity of neutron and proton is investigated in isospin-asymmetric nuclear matter within the Brueckner-Hartree-Fock approach and the BCS theory by adopting the Argonne V14 and the Argonne V18 nucleonnucleon interactions. We find that pairing gaps in the 3PF2 channel predicted by adopting the AV14 interaction are much larger than those by the AV18 interaction. As the isospin-asymmetry increases, the neutron 3 pF2 superfluidity is found to increase rapidly, whereas the proton one turns out to decrease and may even vanish at high enough asymmetries. As a consequence, the neutron 3pF2 superfluidity is much stronger than the proton one at high asymmetries and it predominates over the proton one in dense neutron-rich matter. 相似文献
974.
In this paper, based on the symbolic computing system Maple, the direct method for Lie symmetry groups presented by Sen-Yue Lou [J. Phys. A: Math. Gen. 38 (2005) L129] is extended from the continuous differential equations to the differential-difference equations. With the extended method, we study the well-known differential-difference KP equation, KZ equation and (2+1)-dimensional ANNV system, and both the Lie point symmetry groups and the non-Lie symmetry groups are obtained. 相似文献
975.
By means of the classical symmetry method, we investigate two types of the (2+1)-dimensional nonlinear Klein-Gorden equation. For the wave equation, we give out its symmetry group analysis in detail. For the second type of the (2+1)-dimensional nonlinear Klein-Gorden equation, an optimal system of its one-dimensional subalgebras is constructed and some corresponding two-dimensional symmetry reductions are obtained. 相似文献
976.
We analyze the left-right asymmetry in the semi-inclusive deep inelastic scattering (SIDIS) process using a method where no weighting function are used. Considering all flavor of quarks, we reanalyze the π±production and extend our calculation on the K± production. The predictions on HERMES, COMPASS and JLab kinematics with transversely polarized nucleon target are shown in this paper. 相似文献
977.
We present a preliminary analysis of the photon beam asymmetry observable (Z) from the pho- toproduction reaction channel γn → pπ in the invariant mass range 1.6--2.3 GeV. The measurement was obtained using the near-4π CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory, USA, employing a linearly polarised photon beam with an energy range 1.1 2.3 GeV, incident on a liquid deuterium target. The measurement will provide new data to address the poorly established neutron excitation spectrum and will greatly expand the sparse world data-set both in energy and angle. 相似文献
978.
Analysis of Nanostructural Waveguides Using Fourth-Order Accurate Finite Difference Methods with Nonuniform Scheme
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We successfully apply fourth-order accurate finite difference methods with nonuniform scheme to analysis the symmetric slot waveguides. The results of numerical simulations show that the present nonuniform formula offers the results more accurate than the previously presented second order schemes. 相似文献
979.
We analyze the electric field modes excited in resonant L-shaped gold nanoparticles using a finite-difference time domain method. Compared to a single gold nanorod, both the odd and even modes of the L-shaped nanoparticles can be excited due to the symmetry breaking. The nanoparticles with equal and unequal arms have different dependence of field enhancement and mode on the incident polarization. 相似文献
980.
Approximate Symmetry Reduction and Infinite Series Solutions to the Nonlinear Wave Equation with Damping
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The approximate symmetry perturbation method is applied to the nonlinear damped wave equation. The approximate symmetry reduction equations of different orders are derived and the corresponding series reduction solutions are obtained. 相似文献