全文获取类型
收费全文 | 5119篇 |
免费 | 1727篇 |
国内免费 | 481篇 |
专业分类
化学 | 572篇 |
晶体学 | 110篇 |
力学 | 1113篇 |
综合类 | 56篇 |
数学 | 362篇 |
物理学 | 5114篇 |
出版年
2024年 | 5篇 |
2023年 | 40篇 |
2022年 | 87篇 |
2021年 | 70篇 |
2020年 | 143篇 |
2019年 | 111篇 |
2018年 | 108篇 |
2017年 | 154篇 |
2016年 | 181篇 |
2015年 | 157篇 |
2014年 | 378篇 |
2013年 | 350篇 |
2012年 | 326篇 |
2011年 | 478篇 |
2010年 | 386篇 |
2009年 | 449篇 |
2008年 | 468篇 |
2007年 | 428篇 |
2006年 | 431篇 |
2005年 | 345篇 |
2004年 | 332篇 |
2003年 | 263篇 |
2002年 | 242篇 |
2001年 | 246篇 |
2000年 | 200篇 |
1999年 | 142篇 |
1998年 | 133篇 |
1997年 | 121篇 |
1996年 | 87篇 |
1995年 | 87篇 |
1994年 | 63篇 |
1993年 | 65篇 |
1992年 | 52篇 |
1991年 | 44篇 |
1990年 | 35篇 |
1989年 | 29篇 |
1988年 | 19篇 |
1987年 | 17篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1976年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有7327条查询结果,搜索用时 15 毫秒
31.
Hechong Chen Zehong Liang Xinyue Wang Yong Zhang Lingling Shui Dongmei Deng 《Annalen der Physik》2023,535(1):2200375
By applying a virtual source method, the exact and the paraxial solutions of the Swallowtail beams (SBs) that are governed by the inhomogeneous Helmholtz equation are introduced. The paraxial SBs generated experimentally possess both self-accelerating and self-focusing features. The parameters controlling the field distributions are discussed in theory. From the spectral representation of the Swallowtail wave, in the appropriate limit, the first four terms of the nonparaxial correction series for the (1+2)-dimensional Swallowtail waves that simplify to the SBs are obtained. 相似文献
32.
Haobin Yang Ziyu Wang Zhifeng Tu Junjie Jiang Danlin Xu Zhenwu Mo Haiqi Huang Dongmei Deng 《Annalen der Physik》2023,535(9):2300167
This paper analytically and numerically proposes the propagation dynamics of the symmetric Pearcey Gaussian vortex beam (SPGVB) in the uniformly moving parabolic potential. The optical vortex located in the initial plane produces a vortex channel in the presence of the uniformly moving parabolic potential, called the vortex trajectory. The vortex trajectory can be manipulated dynamically by configuring different combinations of the parameters, and the optical intensity and the focal position can also be affected. Moreover, the spatial dynamic vortex trajectory is derived analytically, and the 2D on-axis and off-axis vortex scenarios are also presented. Our work expands the methods of the vortex trajectory manipulation and may broaden more practical potential applications in the particle manipulation. 相似文献
33.
提出了一种基于有限宽超声束反射的固-固界面退化特性评价方法,从理论和数值仿真角度进行了分析和计算。将两固体界面间的薄层简化为界面弹簧模型,以界面法向和切向劲度系数表征界面的退化程度。通过数值计算求得有限宽超声纵波束在不同入射角和界面不同退化程度下的反射横波、反射纵波的镜面反射系数。进一步地,通过建立二维有限元模型,仿真研究了有限宽超声纵波束在给定入射角及界面不同退化程度下镜面反射系数的变化规律。结果表明,反射纵波和反射横波的镜面反射系数随有限宽超声纵波束的入射角及界面劲度系数的改变而变化,且存在镜面反射系数随界面劲度系数单调且敏感变化的入射角,据此可准确评价界面的退化程度。 相似文献
34.
Satoka Aoyagi Keisuke Mizomichi Keisuke Kamochi Ako Miisho 《Surface and interface analysis : SIA》2022,54(4):356-362
Time-of-flight secondary ion mass spectrometry (TOF-SIMS), when used for the analysis of complex material samples, typically provides data that are complicated and challenging to understand. Therefore, additional data analysis techniques, such as multivariate analysis, are often required to facilitate the interpretation of TOF-SIMS data. In this study, a new method based on the information entropy (Shannon entropy) is proposed as an indicator of the outline characteristics of an unknown sample, such as changes in the material within the sample and mixing conditions. The Shannon entropy values are calculated using the relative intensity of every secondary ion normalized to the total ion count and reflect the diversity of secondary ions in the spectrum. Mixed samples containing two organic electroluminescence materials of different ratios, multilayers of Irganox 1010, and other organic materials were employed to evaluate the utility of Shannon entropy in the analysis of TOF-SIMS data. The findings demonstrate that the Shannon entropy of a spectrum indicates differences in materials and changes in the conditions of a material in a sample without the need for peak identification or the knowledge of specific peaks corresponding to the materials in the sample. 相似文献
35.
In this paper the analytical solutions of the impact of a particle on Timoshenko beams with four kinds of different boundary
conditions are obtained according to Navier's idea, which is further developed. The initial values of the impact forces are
exactly determined by the momentum conservation law. The propagation of the longitudinal and transverse waves along the beam,
especially, the effects of boundary conditions on the characteristics of the reflected waves, are investigated in detail.
Some results are compared with those by MSC/NASTRAN. 相似文献
36.
37.
一个改进的平面梁单元 总被引:8,自引:0,他引:8
根据有限单元法基本原理 ,提出了一个变截面平面梁单元 ,推导了其单元钢度矩阵。这一改进的梁单元用于分析梁高呈线性变化及二次抛物线变化的矩形截面梁 ,将得到准确解。文中给出了一个变截面悬臂梁算例 ,计算表明 ,这一改进的梁单元使变截面梁的分析大大简化 相似文献
38.
In this paper, the off-axial acoustic scattering of a high-order Bessel vortex beam by a rigid immovable (fixed) sphere is investigated. It is shown here that shifting the sphere off the axis of wave propagation induces a dependence of the scattering on the azimuthal angle. Theoretical expressions for the incident and scattered field from a rigid immovable sphere are derived. The near- and far-field acoustic scattering fields are expressed using partial wave series involving the spherical harmonics, the scattering coefficients of the sphere, the half-conical angle of the wave number components of the beam, its order and the beam-shape coefficients. The scattering coefficients of the sphere and the 3D scattering directivity plots in the near- and far-field regions are evaluated using a numerical integration procedure. The calculations indicate that the scattering directivity patterns near the sphere and in the far-field are strongly dependent upon the position of the sphere facing the incident high-order Bessel vortex beam. 相似文献
39.
40.
热/均布载荷下双材料悬臂梁的解析解 总被引:1,自引:0,他引:1
基于弹性介质的二维本构关系和热传导理论,采用逆解法,研究了双材料悬臂梁在热/机械载荷作用下的问题,通过假设双材料悬臂梁构件的应力函数,利用应力、位移边界条件和连续性条件,给出了其位移、应力分布的表达式。 相似文献