全文获取类型
收费全文 | 19920篇 |
免费 | 2688篇 |
国内免费 | 9401篇 |
专业分类
化学 | 19547篇 |
晶体学 | 338篇 |
力学 | 949篇 |
综合类 | 782篇 |
数学 | 3152篇 |
物理学 | 7241篇 |
出版年
2024年 | 75篇 |
2023年 | 225篇 |
2022年 | 318篇 |
2021年 | 276篇 |
2020年 | 245篇 |
2019年 | 280篇 |
2018年 | 201篇 |
2017年 | 277篇 |
2016年 | 279篇 |
2015年 | 329篇 |
2014年 | 547篇 |
2013年 | 678篇 |
2012年 | 503篇 |
2011年 | 514篇 |
2010年 | 548篇 |
2009年 | 638篇 |
2008年 | 676篇 |
2007年 | 647篇 |
2006年 | 738篇 |
2005年 | 767篇 |
2004年 | 757篇 |
2003年 | 1820篇 |
2002年 | 2546篇 |
2001年 | 2344篇 |
2000年 | 1703篇 |
1999年 | 1320篇 |
1998年 | 1545篇 |
1997年 | 1440篇 |
1996年 | 1787篇 |
1995年 | 1709篇 |
1994年 | 1470篇 |
1993年 | 798篇 |
1992年 | 1073篇 |
1991年 | 972篇 |
1990年 | 904篇 |
1989年 | 790篇 |
1988年 | 82篇 |
1987年 | 58篇 |
1986年 | 44篇 |
1985年 | 43篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
81.
本文给出了 n阶 r-不可分矩阵的本原指数的上界 ,即任 n阶 r—不可分矩阵 A的本原指数 (A)≤n+(r- ) 2r (1≤ r相似文献
82.
晶体微观结构是晶体材料在特定物理条件下其多个能量极小平衔态在空间形成的某种微尺度的规则分布.几何非线性的连续介质力学理论可以用能量极小化原理来解释晶体微观结构的形成,并用Young测度来刻画平衡态各变体在空间的概率分布.定性的理解与定量地分析和计算晶体材料的微观结构对于发展和改进高级晶体功能材料,如形状记忆合金、铁电体、磁至伸缩材料等,有重要的意义.本文回顾了近年来晶体微观结构数值计算方面的最新进展.介绍了计算晶体微观结构的几种数值方法及有关的数值分析结果。 相似文献
83.
利用内部爆炸加载方法对U-Nb合金进行爆破试验,对爆破试验产生的破片进行回收,并对U-Nb合金破片进行一些微观检测分析,从而初步研究在爆炸加载下U-Nb合金的微观断裂机制。 相似文献
84.
85.
The compression behaviour of Ni77P23 amorphous alloy is investigated at room temperature in a diamond-anvil cell instrument using in-situ high pressure energy dispersive x-ray diffraction with a synchrotron radiation source. The equation of state is determined by fitting the experimental data according to the Birch-Murnaghan equation. It is found that the structure of Ni77P23 amorphous alloy is stable under pressures up to 30.5 GPa. Within the pressure range from zero to the experimental one, the pressure-induced structural relaxation is reversible. 相似文献
86.
87.
We investigate magnetic and crystalline microstructures of melt-spun (Fe0.675Pt0.325)100-xBx (x=12, 14, 16, 18,20) nanocomposite ribbons after optimal thermal treatment using a magnetic force microscope. The magnetic microstructures are characterized by darker spots adjacent to brighter ones in a sub-micro scale and in random distribution. It is found that the strength of the exchange coupling interaction between the crystals in the 10-100 nm scale, implied by the maximum value (δM)max of the Henkel plot, could be roughly described by the ratio of the average width of the magnetic spots w^- to the average crystal size D^- for the ribbons. Moreover, we find that the intrinsic coercivity jHc of the ribbons is sensitive to their crystal sizes, and the smaller D^-, the higher jHc. Finally, by using roughness analysis, the curve of the root mean square values (δФ)rms of the phase shift of the magnetic force images versus the boron content x is obtained, which is qualitatively consistent with that of the magnetization σ12 kOe of the ribbons versus x. 相似文献
88.
Electron Spin Resonance Studies of Mn^2+ in Freshwater Snail Shells: Pomacea Canaliculata Lamarck and Fossilized Snail Shell
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)
N.Udomkan S.Meejoo P.Limsuwan P.Winotai Y.Chaimanee 《中国物理快报》2005,22(7):1780-1783
We study paramagnetic Mn^2 ions present in the nowadays shells of univalve freshwater snails of Pomacea canaliculata lamarck (PCL) and the fossilized freshwater snail (FFS), Viviparus. All these shells are abundant in Thailand. The PCL shells were ground into fine powder. A set of seven samples were then separately annealed for 2 h in air atmosphere at different annealing temperatures while the FFS powder was characterized as-received. The PCL shells mainly consist of aragonite and a fraction of calcite. The heat treatments of the PCL powder samples at temperature higher than 450℃ resulted in an irreversible phase transformation from aragonite to calcite. However, it is found that the FFS shell is mainly made of calcite, with a minor fraction of aragonite. The crystal structure of the high-temperature-annealed PCL samples are quite similar to that of FFS, which indicates that the metamorphosis (aragonite→calcite) in the FFS shell had occurred but was not yet completed, although it had remained under the pressure and temperature of the Earth‘s crusts over millions of years. Our detailed ESR spectral analyses of PCL and FFS show that Mn^2 ions enter the Ca^2 sites during a biomineralization process. Simulated ESR parameters of PCL-500 of Mn^2 at a uniaxial site of calcite are reported. It is surprising to And that the ratio of Mn^2 concentration present in FFS to those in PCL shells evaluated from ESR spectra is as much as 10:1. 相似文献
89.
90.
周春琴 《数学物理学报(A辑)》1998,18(1):33-40
研究了与p-Laplace算子对映的铁磁甸系统的Landau-Lifshitz方程,证明了该方程的从m(m≥3)维紧流形M(不带边界)映射到R^3中的单位球面S^2上的整体弱解的存性;建立了p调和映射理论与该方程的联系。 相似文献