全文获取类型
收费全文 | 15798篇 |
免费 | 1882篇 |
国内免费 | 2538篇 |
专业分类
化学 | 5509篇 |
晶体学 | 231篇 |
力学 | 458篇 |
综合类 | 263篇 |
数学 | 1130篇 |
物理学 | 2947篇 |
综合类 | 9680篇 |
出版年
2024年 | 34篇 |
2023年 | 133篇 |
2022年 | 321篇 |
2021年 | 333篇 |
2020年 | 389篇 |
2019年 | 368篇 |
2018年 | 371篇 |
2017年 | 437篇 |
2016年 | 470篇 |
2015年 | 672篇 |
2014年 | 830篇 |
2013年 | 1010篇 |
2012年 | 1021篇 |
2011年 | 1167篇 |
2010年 | 1087篇 |
2009年 | 1175篇 |
2008年 | 1394篇 |
2007年 | 1328篇 |
2006年 | 1185篇 |
2005年 | 1071篇 |
2004年 | 904篇 |
2003年 | 809篇 |
2002年 | 907篇 |
2001年 | 797篇 |
2000年 | 640篇 |
1999年 | 414篇 |
1998年 | 126篇 |
1997年 | 97篇 |
1996年 | 97篇 |
1995年 | 96篇 |
1994年 | 77篇 |
1993年 | 76篇 |
1992年 | 54篇 |
1991年 | 44篇 |
1990年 | 37篇 |
1989年 | 32篇 |
1988年 | 44篇 |
1987年 | 34篇 |
1986年 | 25篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 4篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1965年 | 5篇 |
1964年 | 4篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The present paper covers a salt of 2:18 heteropoly complex of tungstotitanophosphate prepared with the method of improved sequence preparation. The title compound was characterized by elemental analysis, 31P NMR spectra, polarography, cyclic voltammetry, IR, UV, X-ray powder diffraction , X-ray photoelectron spectra and TG-DTA analysis. The results show that the complex with the formula K8[TiP2W17O62]·12H2O has Dawson structure. Its properties such as spectra, redox behavior and thermal stability are discussed. 相似文献
72.
73.
Kang Hai TAN Xiao Ping YANG 《数学学报(英文版)》2006,22(3):701-710
In this paper we give a geometric interpretation of the notion of the horizontal mean curvature which is introduced by Danielli Garofalo-Nhieu and Pauls who recently introduced sub- Riemannian minimal surfaces in Carnot groups. This will be done by introducing a natural nonholonomic connection which is the restriction (projection) of the natural Riemannian connection on the horizontal bundle. For this nonholonomic connection and (intrinsic) regular hypersurfaces we introduce the notions of the horizontal second fundamental form and the horizontal shape operator. It turns out that the horizontal mean curvature is the trace of the horizontal shape operator. 相似文献
74.
75.
Excitation Properties of the Biological Neurons with Side-Inhibition Mechanism in Small-World Networks 总被引:3,自引:0,他引:3
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 have studied the excitation properties of biophysical Hodgkin-Huxley neurons with the side-inhibition mechanism in small-world networks. The result shows that the excitation properties in the networks are preferably consistent with the characteristic properties of a brain neural system under external constant stimuli, such as fatigue effect, extreme excitation principle, and the brain neural excitation response induced by different in- tensity of noise and coupling. The results of the study might shed some light on the study of the brain nerve electrophysiology and epistemological science. 相似文献
76.
Incident intensity, defined by the amount of particles deposited per pulse, is an important parameter in the film growth process of pulsed laser deposition (PLD). Different from previous models, we investigate the irreversible and reversible growth processes by using a kinetic Monte Carlo method and find that island density and film morphology strongly depend on pulse intensity. At higher pulse intensities, lots of adatoms instantaneously diffuse on the substrate surface, and then nucleation easily occurs between the moving adatoms resulting in more smaller-size islands. In contrast, at the lower pulse intensities, nucleation event occurs preferentially between the single adatom and existing islands rather than forming new islands, and therefore the average island size becomes larger in this case. Additionally, our results show that substrate temperature plays an important role in film growth. In particular, it can determine the films shape and weaken the effect of pulse intensity on film growth at the lower temperatures by controlling the mobility rate of atoms. Our results can match the related theoretical and experimental results. 相似文献
77.
基于将Maxwell方程与四能级原子系统速率方程相结合而建立起随机激光时域理论,并利用有限时域差分法,研究了二维随机介质中激光模式的输出特性与介质尺寸、外形及抽运速率等参数的关系.结果表明,与传统激光模式相似,随机激光模式的强度随抽运速率的变化不仅具有阈值特性,而且具有饱和特性.基于模式特性对介质及抽运参数的依赖关系,提出了二维随机激光器的选模方式,在很大程度上不同于传统激光器的选模方式.
关键词:
随机激光器
模式选择
无序介质中的光学特性 相似文献
78.
79.
DING Ning FANG Jian-Hui 《理论物理通讯》2006,46(2):265-268
In this paper the Lie symmetry and conserved quantities for nonholonomic Vacco dynamical systems are studied. The determining equation of the Lie symmetry for the system is given. The general Hojman conserved quantity and the Lutzky conserved quantity deduced from the symmetry are obtained. 相似文献
80.
对短程飞行时间法(tim e-of-flight,TOF)中推算冷原子温度的理论拟合公式与近似拟合公式进行了误差分析与比较。研究表明:对于使用短程飞行吸收光谱信号推测冷原子团温度,当探测光光斑半径与冷原子团高斯半径之比k小于0.2时,理论拟合公式和近似拟合公式能很好的相符,随着探测光光斑半径与冷原子团高斯半径比值的逐渐增大,用近似拟合公式所得TOF吸收信号与用理论拟合公式所得TOF吸收信号的误差也将逐渐增大,当比值为0.5时,用近似拟合公式所得TOF吸收信号的误差将增大到20%。 相似文献