全文获取类型
收费全文 | 2673篇 |
免费 | 1526篇 |
国内免费 | 509篇 |
专业分类
化学 | 305篇 |
晶体学 | 84篇 |
力学 | 73篇 |
综合类 | 40篇 |
数学 | 77篇 |
物理学 | 4129篇 |
出版年
2024年 | 10篇 |
2023年 | 65篇 |
2022年 | 88篇 |
2021年 | 77篇 |
2020年 | 51篇 |
2019年 | 65篇 |
2018年 | 48篇 |
2017年 | 89篇 |
2016年 | 104篇 |
2015年 | 111篇 |
2014年 | 342篇 |
2013年 | 181篇 |
2012年 | 253篇 |
2011年 | 257篇 |
2010年 | 271篇 |
2009年 | 336篇 |
2008年 | 340篇 |
2007年 | 245篇 |
2006年 | 295篇 |
2005年 | 214篇 |
2004年 | 222篇 |
2003年 | 173篇 |
2002年 | 118篇 |
2001年 | 91篇 |
2000年 | 95篇 |
1999年 | 65篇 |
1998年 | 63篇 |
1997年 | 79篇 |
1996年 | 70篇 |
1995年 | 53篇 |
1994年 | 43篇 |
1993年 | 37篇 |
1992年 | 50篇 |
1991年 | 35篇 |
1990年 | 28篇 |
1989年 | 25篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有4708条查询结果,搜索用时 15 毫秒
141.
In this paper we apply the assumption of our recent work in noncommutative scalar models to the noncommutative U(1) gauge theories. This assumption is that the noneommutative effects start to be visible continuously from a scale ANC and that below this scale the theory is a commutative one. Based on this assumption and using background field method and loop calculations, an effective action is derived for noncommutative U(1) gauge theory. It will be shown that the corresponding low energy effective theory is asymptotically free and that under this condition the noncommutative quadratic IR divergences will not appear. The effective theory contains higher dimensional terms, which become more important at high energies. These terms predict an elastic photon-photon scattering due to the noncommutativity of space. The coefficients of these higher dimensional terms also satisfy a positivity constraint indicating that in this theory the related diseases of superluminal signal propagating and bad analytic properties of S-matrix do not exist. In the last section, we will apply our method to the noncommutative extra dimension theories. 相似文献
142.
An investigation of the optical properties of a hydrogenic donor in spherical parabolic quantum dots has been performed by using the matrix diagonalization method. The optical absorption coefficient between the ground (L = 0) and the first excited state (L = 1) have been examined based on the computed energies and wave functions. The results are presented as a function of the incident photon energy for the different values of the confinement strength. These results show the effects of the quantum size and the impurity on the optical absorption coefficient of a donor impurity quantum dot. 相似文献
143.
<正>We demonstrate a photonic band gap(PBG) from one-dimensional(1D) periodic structures created by a double-layer unit cell with an air layer and an anisotropic nonmagnetic left-handed metamaterial(LHM) layer whose permittivity elements are partially negative.The requirements imposed on the materials and structures to realize a PBG are derived when the frequency is above or below the cutoff frequency,and the transmission properties of the PBG are discussed by utilizing 4×4 transfer-matrix method with dispersive semiconductor metamaterial. 相似文献
144.
Effect of the defect on the focusing in a two-dimensional photonic-crystal-based flat lens
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We have investigated in detail the influence of defect on the focusing of electromagnetic waves in a two-dimensional photonic-crystal flat lens by using the finite-difference time-domain method. The result shows that many focusings can be observed at the symmetrical positions when a defect is introduced into the lens. Furthermore, the wave-guides in the lens can confine the transmission wave effectively and improve the quality of the focusing. 相似文献
145.
146.
We propose a new type of two-dimensional (2D) photonic crystal L-shaped bent waveguides based on ring resonators with an acceptable bandwidth. The proposed structure mechanism is based on coupling between a waveguide and a ring resonator. This structure is designed and verified by finite-difference time-domain (FDTD) computation. Our simulation using this method gets over 90% output. 相似文献
147.
148.
Carrier-Envelop Phase-Dependent Effect on Photoelectron Angular Distribution in Single-Cycle Laser Pulses *
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)
Using a nonperturbative scattering theory, We study the photoelectron angular distributions (PADs) of Kr atoms irradiated by an infinite sequence of intense single-cycle pulses of circular polarization. We demonstrate the inversion asymmetry of PADs and the dependence of PADs on the carrier-envelop phase of the single-cycle pulses. The inversion asymmetry is caused by the interference between transition channels where the different channels are characterized by different combinations of absorbed-photon numbers in the ionization process. Our results provide a possible method to determine the value of carrier-envelop phase by the detected PADs. 相似文献
150.
陈宝振 《原子与分子物理学报》1991,8(3):1987-1990
本文简要地说明了矢量势平方项在经典电动力学过程和量子力学过程中的作用,特别地说明了矢量势平方项在原子多光子电离过程中的作用。 相似文献