全文获取类型
收费全文 | 98015篇 |
免费 | 11930篇 |
国内免费 | 8394篇 |
专业分类
化学 | 39377篇 |
晶体学 | 1380篇 |
力学 | 13956篇 |
综合类 | 1449篇 |
数学 | 27141篇 |
物理学 | 35036篇 |
出版年
2024年 | 135篇 |
2023年 | 883篇 |
2022年 | 1473篇 |
2021年 | 2893篇 |
2020年 | 2669篇 |
2019年 | 2492篇 |
2018年 | 2298篇 |
2017年 | 2900篇 |
2016年 | 3404篇 |
2015年 | 2952篇 |
2014年 | 4339篇 |
2013年 | 6774篇 |
2012年 | 5290篇 |
2011年 | 5954篇 |
2010年 | 5245篇 |
2009年 | 6010篇 |
2008年 | 5945篇 |
2007年 | 6063篇 |
2006年 | 5343篇 |
2005年 | 4495篇 |
2004年 | 4072篇 |
2003年 | 3800篇 |
2002年 | 6011篇 |
2001年 | 3299篇 |
2000年 | 2760篇 |
1999年 | 2381篇 |
1998年 | 2258篇 |
1997年 | 1795篇 |
1996年 | 1635篇 |
1995年 | 1374篇 |
1994年 | 1304篇 |
1993年 | 1105篇 |
1992年 | 1095篇 |
1991年 | 796篇 |
1990年 | 660篇 |
1989年 | 540篇 |
1988年 | 502篇 |
1987年 | 403篇 |
1986年 | 378篇 |
1985年 | 512篇 |
1984年 | 404篇 |
1983年 | 232篇 |
1982年 | 409篇 |
1981年 | 551篇 |
1980年 | 477篇 |
1979年 | 522篇 |
1978年 | 428篇 |
1977年 | 329篇 |
1976年 | 265篇 |
1973年 | 166篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
通过建立具有平面近横向各向异性场的非晶态合金薄带及膜的磁畴结构模型,利用线性化Maxwell方程组及Landau-Lifshitz方程,推出了在高频交变磁场及外加面内轴向直流磁场Hex作用下的铁磁材料的与取向相关的磁导率表达式,得到了对方位角平均的相对磁导率及阻抗的计算式,导出了磁导率与张量磁化率分量间的关系,对材料磁导率的实部及虚部随Hex的变化进行了计算,并给出了对应的磁谱图.建立的磁导率与外磁场的理论关系可将Panina及Kraus给出的理论结果统一起来.
关键词:
非晶态合金薄带及膜
取向相关磁导率
GMI效应理论与计算
近横向各向异性场 相似文献
92.
93.
We employ a first-principles plane wave method with the
relativistic analytic pseudopotential of Hartwigsen, Goedecker and Hutter
(HGH) scheme in the frame of DFT to calculate
the equilibrium lattice parameters and the thermodynamic properties of
AlB2 compound with hcp structure. The obtained lattice parameters are in
good agreement with the available experimental data and those calculated by
others. Through the quasi-harmonic Debye model, obtained successfully are
the dependences of the
normalized lattice parameters a/a0 and c/c0 on pressure P, the normalized
primitive cell volume V/V0 on pressure P, the variation of the thermal
expansion α with pressure P and temperature T, as well as the Debye
temperature \ThetaD and the heat capacity CV on pressure P and
temperature T. 相似文献
94.
95.
Second-order random wave solutions for interfacial internal waves in N-layer density-stratified fluid 下载免费PDF全文
This paper studies the random internal wave equations describing the density interface displacements and the velocity potentials of N-layer stratified fluid contained between two rigid walls at the top and bottom. The density interface displacements and the velocity potentials were solved to the second-order by an expansion approach used by Longuet-Higgins (1963) and Dean (1979) in the study of random surface waves and by Song (2004) in the study of second- order random wave solutions for internal waves in a two-layer fluid. The obtained results indicate that the first-order solutions are a linear superposition of many wave components with different amplitudes, wave numbers and frequencies, and that the amplitudes of first-order wave components with the same wave numbers and frequencies between the adjacent density interfaces are modulated by each other. They also show that the second-order solutions consist of two parts: the first one is the first-order solutions, and the second one is the solutions of the second-order asymptotic equations, which describe the second-order nonlinear modification and the second-order wave-wave interactions not only among the wave components on same density interfaces but also among the wave components between the adjacent density interfaces. Both the first-order and second-order solutions depend on the density and depth of each layer. It is also deduced that the results of the present work include those derived by Song (2004) for second-order random wave solutions for internal waves in a two-layer fluid as a particular case. 相似文献
96.
High index of refraction via quantum interference in a three-level system of Er^3+-doped yttrium aluminium garnet crystal 下载免费PDF全文
A simple three-level system is proposed to produce high index of refraction with zero absorption in an Er^3+-doped yttrium aluminium garnet (YAG) crystal, which is achieved for a probe field between the excited state 4I13/2 and ground state 4I15/2 by adjusting a strong coherent driving field between the upper excited state 4I11/2 and 4I15/2. It is found that the changes of the frequency of the coherent driving field and the concentration of Er^3+ ions in the YAG crystal can maximize the index of refraction accompanied by vanishing absorption. This result could be useful for the dispersion compensation in fibre communication, laser particle acceleration, high precision magnetometry and so on. 相似文献
97.
一类非线性Schr(o)dinger方程的守恒差分法与Fourier谱方法 总被引:1,自引:0,他引:1
考察了一类带导数项的非线性Schrodinger方程的周期边值问题,提出了一种守恒的差分格式,在空间方向上采用Fourier谱方法,证明了格式的稳定性和收敛性.数值试验得到了与理论分析一致的结果. 相似文献
98.
Zhong-Qing Wang 《Journal of Mathematical Analysis and Applications》2002,274(1):374-403
An orthogonal system of rational functions is discussed. Some inverse inequalities, imbedding inequalities and approximation results are obtained. Two model problems are considered. The stabilities and convergences of proposed rational spectral schemes and rational pseudospectral schemes are proved. The techniques used in this paper are also applicable to other problems on the whole line. Numerical results show the efficiency of this approach. 相似文献
99.
Dean A. Carlson 《Journal of Mathematical Analysis and Applications》2002,276(2):561-588
The method of equivalent variational methods, originally due to Carathéodory for free problems in the calculus of variations is extended to investigate feedback Nash equilibria for a class of n-person differential games. Both the finite-horizon and infinite-horizon cases are considered. Examples are given to illustrate the presented results. 相似文献
100.
Pierluigi Contucci Sandro Graffi Stefano Isola 《Journal of statistical physics》2002,106(5-6):895-914
For the long-range deterministic spin models with glassy behaviour of Marinari, Parisi and Ritort we prove weighted factorization properties of the correlation functions which represent the natural generalization of the factorization rules valid for the Curie–Weiss case. 相似文献