全文获取类型
收费全文 | 8366篇 |
免费 | 1243篇 |
国内免费 | 577篇 |
专业分类
化学 | 3436篇 |
晶体学 | 122篇 |
力学 | 462篇 |
综合类 | 39篇 |
数学 | 1314篇 |
物理学 | 4813篇 |
出版年
2024年 | 19篇 |
2023年 | 79篇 |
2022年 | 173篇 |
2021年 | 183篇 |
2020年 | 244篇 |
2019年 | 232篇 |
2018年 | 196篇 |
2017年 | 195篇 |
2016年 | 291篇 |
2015年 | 243篇 |
2014年 | 333篇 |
2013年 | 692篇 |
2012年 | 416篇 |
2011年 | 471篇 |
2010年 | 382篇 |
2009年 | 515篇 |
2008年 | 448篇 |
2007年 | 550篇 |
2006年 | 482篇 |
2005年 | 380篇 |
2004年 | 377篇 |
2003年 | 344篇 |
2002年 | 386篇 |
2001年 | 300篇 |
2000年 | 336篇 |
1999年 | 260篇 |
1998年 | 254篇 |
1997年 | 166篇 |
1996年 | 152篇 |
1995年 | 138篇 |
1994年 | 133篇 |
1993年 | 100篇 |
1992年 | 105篇 |
1991年 | 67篇 |
1990年 | 48篇 |
1989年 | 43篇 |
1988年 | 53篇 |
1987年 | 38篇 |
1986年 | 54篇 |
1985年 | 49篇 |
1984年 | 52篇 |
1983年 | 13篇 |
1982年 | 24篇 |
1981年 | 32篇 |
1980年 | 22篇 |
1979年 | 16篇 |
1978年 | 28篇 |
1977年 | 24篇 |
1976年 | 17篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Finite chains of a two-state random Potts spin model with periodic boundary conditions are studied within Glauber dynamics. The spin exchange is assumed random with frustration between ferro and antiferromagnetic values (±J). Time-dependent fluctuations are induced by periodic temperature oscillations. Master type differential equations for spin correlation functions are solved within linear response theory. The spectrum of relaxation times are calculated at different temperatures. The ±J Potts glass chains undergo a zero temperature phase transition. The barriers against inversion of the spin chain take only two values; 0 and 2|J|. The temperature behaviour of specific heat is characterized by rounded peaks. The frequency dependence displays two plateaus for the real part of specific heat and two corresponding peaks for the imaginary part. The dynamic specific heat is not affected by the longest relaxing mode like susceptibility. The time separation of the modes is demonstrated by the Cole-Cole plots. 相似文献
92.
狄拉克方程的单旋量解法以及由此引起的认识上的差异 总被引:2,自引:0,他引:2
把狄拉克方程分解成了两个单旋量的联立方程组.指出现行的自旋理论仅考虑了其中的一个方程,是以一个单旋量代替双旋量来描述状态而建立起来的.笔者在认同现行自旋理论可以作为狄拉克方程的一种求解方法,因而同意其中的某些提法外,对于其主要的物理观念:微观粒子存在着独立于现实的位形空间之外的一个自旋空间,在这个自旋空间内禀着角动量S和磁矩μ;这个自旋理论是相对论性量子力学导出的必然结论等等看法予以否定.笔者认为,只有同时考虑两个单旋量的方程,同时计及两个单旋量,才能准确地描述状态,从而正确地描述客观规律. 相似文献
93.
Vincenzo Recupero 《Journal of Mathematical Analysis and Applications》2004,300(2):387-407
In this paper we study a model of phase relaxation for the Stefan problem with the Cattaneo–Maxwell heat flux law. We prove an existence and uniqueness result for the resulting problem and we show that its solution converges to the solution of the Stefan problem as the two relaxation parameters go to zero, provided a relation between these parameters holds. 相似文献
94.
Sebastiaan van Dijken Xavier Fain Steven M. Watts Kentaro Nakajima J. M. D. Coey 《Journal of magnetism and magnetic materials》2004,280(2-3):322-326
A detailed study of the in-plane magnetotransport properties of spin valves with one and two Fe3O4 electrodes is presented. Fe3O4/Au/Fe3O4 spin valves exhibit a clear anisotropic magnetoresistance in small magnetic fields but no giant magnetoresistance (GMR). The absence of GMR in these structures is due to simultaneous magnetization reversal in the two Fe3O4 layers. By contrast, a negative GMR effect is measured on Fe3O4/Au/Fe spin valves. The negative GMR is attributed to an electron spin scattering asymmetry at the Fe3O4/Au interface or an induced spin scattering asymmetry in the Au interfacial layers. 相似文献
95.
Periodica Mathematica Hungarica - Let X 1,X 2,... be a sequence of independent and identically distributed random variables, and put % MATHTYPE!MTEF!2!1!+-%... 相似文献
96.
Anomalously high fluorescence spectrum Stokes' shifts of 2(4-pyridyl)-5-(4-methylphenyl)oxazole, 2(4-pyridyl)-5-(4-methoxyphenyl)oxazole, 2(4-pyridyl)-5-(4-N,N-dimethylaminophenyl)oxazole have been found. The fluorescence spectra of the compounds studied are shifted to longer wavelengths as the solvent dielectric constant increases. The dipole moments of these compounds increase by 3–4 times upon excitation. The fluorescence spectra of the compounds investigated are shifted to shorter wavelengths, and the fluorescence quantum yields increase as the temperature decreases. The fluorescence rate constant of 2(4-pyridyl)-5-(4-N,N-dimethylaminophenyl)oxazole changes slightly as the temperature decreases from 293 K (relaxed state) to 114 K (mainly nonrelaxed state). It was concluded that the anomalously high fluorescence Stokes' shift of 2-pyridyl-5-aryloxazole derivatives is caused by solvent orientation relaxation. 相似文献
97.
P. Tekely V. G rardy P. Palmas D. Canet A. Retournard 《Solid state nuclear magnetic resonance》1995,4(6):361-367
A simple modification of the standard cross-polarization method designed for quenching the proton T1ρ dependence when studying polarization transfer is presented. It is demonstrated that by using this simple procedure, new and subtle details of cross-polarization dynamics, previously hidden by the T1ρ(1H) effect, can be observed in dipolar-coupled spin systems. 相似文献
98.
We estimate the concentration functions of n-fold convolutions of one-dimensional probability measures. The Kolmogorov–Rogozin inequality implies that for nondegenerate distributions these functions decrease at least as O(n
–1/2). On the other hand, Esseen(3) has shown that this rate is o(n
–1/2) iff the distribution has an infinite second moment. This statement was sharpened by Morozova.(9) Theorem 1 of this paper provides an improvement of Morozova's result. Moreover, we present more general estimates which imply the rates o(n
–1/2). 相似文献
99.
Luciano Galeone Roberto Garrappa 《Journal of Computational and Applied Mathematics》1997,80(2):377-195
We study convergence properties of time-point relaxation (TR) Runge-Kutta methods for linear systems of ordinary differential equations. TR methods are implemented by decoupling systems in Gauss-Jacobi, Gauss-Seidel and successive overrelaxation modes (continuous-time iterations) and then solving the resulting subsystems by means of continuous extensions of Runge-Kutta (CRK) methods (discretized iterations). By iterating to convergence, these methods tend to the same limit called diagonally split Runge-Kutta (DSRK) method. We prove that TR methods are equivalent to decouple in the same modes the linear algebraic system obtained by applying DSRK limit method. This issue allows us to study the convergence of TR methods by using standard principles of convergence of iterative methods for linear algebraic systems. For a particular problem regions of convergence are plotted. 相似文献
100.