全文获取类型
收费全文 | 3186篇 |
免费 | 1487篇 |
国内免费 | 882篇 |
专业分类
化学 | 508篇 |
晶体学 | 39篇 |
力学 | 741篇 |
综合类 | 97篇 |
数学 | 392篇 |
物理学 | 3778篇 |
出版年
2024年 | 38篇 |
2023年 | 124篇 |
2022年 | 115篇 |
2021年 | 148篇 |
2020年 | 88篇 |
2019年 | 96篇 |
2018年 | 90篇 |
2017年 | 121篇 |
2016年 | 135篇 |
2015年 | 174篇 |
2014年 | 344篇 |
2013年 | 263篇 |
2012年 | 192篇 |
2011年 | 285篇 |
2010年 | 291篇 |
2009年 | 247篇 |
2008年 | 364篇 |
2007年 | 265篇 |
2006年 | 283篇 |
2005年 | 277篇 |
2004年 | 266篇 |
2003年 | 243篇 |
2002年 | 141篇 |
2001年 | 137篇 |
2000年 | 107篇 |
1999年 | 100篇 |
1998年 | 83篇 |
1997年 | 85篇 |
1996年 | 64篇 |
1995年 | 56篇 |
1994年 | 55篇 |
1993年 | 56篇 |
1992年 | 41篇 |
1991年 | 54篇 |
1990年 | 48篇 |
1989年 | 39篇 |
1988年 | 9篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 2篇 |
排序方式: 共有5555条查询结果,搜索用时 765 毫秒
871.
将五光子晶体单模波导平行、邻近放置构成定向耦合器,依据自映像原理,数值分析了输入光场对称入射时,该系统中光的传播行为.基于此结构,设计了1×3光分束器,其器件长度可短至14.26μm.仅仅通过对称地改变耦合区中两个介质柱的有效折射率,使光场在横向发生重新分布,便可实现输出能量的均分或自由分配.通过非对称地改变耦合区中的一个介质柱,可实现3个输出端的输出能量的自由分配.该光分束器具有微小尺寸和各输出端输出能量的比例可自由调制的特点,在未来集成光回路中具有广泛的应用价值. 相似文献
872.
为了保持高岛分辨率合成孔径雷达(SAR)图像中的纹理结构,提出了一种基于BivaShrink模型的Contourlet 域SAR图像相干斑噪声抑制算法.联合当前层和父层的Contourlet系数,通过计算局部方差一致性范数和区域能量比,自适应地确定方差估计区域的形状和大小.从而对原始图像方差进行最优估计.实验结果表明,算法在噪声的去除和结构信息等细节的保持上均不同程度的优于小波BivaShrink去噪算法和Contourlet 阈值去噪算法,主观效果和数值指标都有较好改进. 相似文献
873.
874.
The generalized Thirring model with impurity coupling is defined on two-dimensional noncommutative space-time, a modified propagator and free energy are derived by means of functional integrals method. Moreover, quantum fluctuations and excitation energies are calculated on two-dimensional black hole and soliton background. 相似文献
875.
The structure and working principle of Micromegas (MICRO Mesh Gaseous Structure) is discussed. Some radiation sources of α and X rays are used to test this detector. The optimized electric-field intensity of the conversion gap is obtained. The transmission of electrons and the uniformity of the amplification gap are also presented. The energy resolution of the 5.9 keV peak is better than 27%. 相似文献
876.
段书超 《核聚变与等离子体物理》2009,29(2):126-130
通过数值模拟研究了欧姆定律中的Hall效应修正对MHD湍流的能量衰减的影响。在低或没有磁螺旋性约束的情况下推导出了 t–1能量衰减律。 相似文献
877.
An Alternative Method for Calculating Bound-State of Energy Eigenvalues of Klein-Gordon for Quasi-exactly Solvable Potentials
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)
Eser Olgar 《中国物理快报》2009,26(2):13-16
We obtain the bound-state energy of the Klein-Gordon equation for some examples of quasi-exactly solvable potentials within the framework of asymptotic iteration method (AIM). The eigenvalues are calculated for type- 1 solutions. The whole quasi-exactly solvable potentials are generated from the defined relation between the vector and scalar potentials. 相似文献
878.
Radiative Energy Shifts of an Atom Coupled to the Derivative of a Scalar Field near a Reflecting Boundary
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 study the radiative energy level shifts of a two-level atom in dipole coupling to the derivative of a massless scalar quantum field in a spacetime with a perfectly reflecting boundary, and calculate the contributions of vacuum fluctuations and radiation reaction to the level shift. It is found that the energy level shift of the excited state is an oscillating function of the atom's distance from the boundary and it can either be positive or negative, while that of the ground state is always positive. The most remarkable feature is that the energy level shift of the ground state behaves like 1/z^4 when the atom's distance from the boundary, z, is very large as compared to the transition wavelength of the atom, while it behaves like 1/z^3 when z is very small 相似文献
879.
Optical properties of hexagonal and cubic ZnS nanoribbons are studied by using valence electron energy loss spectroscopy (VEELS) and ab initio band structure calculations. The peaks in VEELS are assigned to interband transitions by comparing the interband transition strengths with the calculated densities of states. The optical properties are deduced from the experimental VEELS, and the theoretical calculations give consistent results. This combination of experimental and theoretical approaches provides a comprehensive understanding of the optical properties of polytype ZnS. 相似文献
880.
Cross sections for electron impact excitation of lithium from the ground state 1s^22s to the excited states 1s2s^2, 1s2p^2, 1s2snp (n = 2-5), 1s2sns (n = 3 5), 1s2pns (n = 3-5), and 1s2pnp (n = 3-5) are calculated by using a full relativistic distorted wave method. The latest experimental electron energy loss spectra for inner-shell electron excitations of lithium at a given incident electron energy of 2500 eV [Chin. Phys. Lett. 25 (2008)3649] have been reproduced by the present theoretical investigation excellently. At the same time, the structures of electron energy loss spectra of lithium at low incident electron energy are also predicted theoretically, it is found that the electron energy loss spectra in the energy region of 55-57eV show two-peak structures. 相似文献