全文获取类型
收费全文 | 49869篇 |
免费 | 3151篇 |
国内免费 | 3750篇 |
专业分类
化学 | 21355篇 |
晶体学 | 469篇 |
力学 | 3836篇 |
综合类 | 504篇 |
数学 | 10460篇 |
物理学 | 20146篇 |
出版年
2024年 | 76篇 |
2023年 | 445篇 |
2022年 | 1091篇 |
2021年 | 1080篇 |
2020年 | 1127篇 |
2019年 | 1140篇 |
2018年 | 992篇 |
2017年 | 1165篇 |
2016年 | 1308篇 |
2015年 | 1020篇 |
2014年 | 1598篇 |
2013年 | 3133篇 |
2012年 | 1929篇 |
2011年 | 2167篇 |
2010年 | 1759篇 |
2009年 | 2835篇 |
2008年 | 3065篇 |
2007年 | 3475篇 |
2006年 | 2942篇 |
2005年 | 2303篇 |
2004年 | 1935篇 |
2003年 | 2213篇 |
2002年 | 2627篇 |
2001年 | 1982篇 |
2000年 | 1887篇 |
1999年 | 1600篇 |
1998年 | 1551篇 |
1997年 | 900篇 |
1996年 | 865篇 |
1995年 | 749篇 |
1994年 | 805篇 |
1993年 | 595篇 |
1992年 | 664篇 |
1991年 | 440篇 |
1990年 | 422篇 |
1989年 | 324篇 |
1988年 | 283篇 |
1987年 | 282篇 |
1986年 | 245篇 |
1985年 | 233篇 |
1984年 | 230篇 |
1983年 | 139篇 |
1982年 | 192篇 |
1981年 | 186篇 |
1980年 | 119篇 |
1979年 | 149篇 |
1978年 | 128篇 |
1977年 | 118篇 |
1976年 | 74篇 |
1973年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Vincent Maurice 《Surface science》2005,581(1):88-104
STM, STS, LEED and XPS data for crystalline θ-Al2O3 and non-crystalline Al2O3 ultra-thin films grown on NiAl(0 0 1) at 1025 K and exposed to water vapour at low pressure (1 × 10−7-1 × 10−5 mbar) and room temperature are reported. Water dissociation is observed at low pressure. This reactivity is assigned to the presence of a high density of coordinatively unsaturated cationic sites at the surface of the oxide film. The hydroxyl/hydroxide groups cannot be directly identify by their XPS binding energy, which is interpreted as resulting from the high BE positions of the oxide anions (O1s signal at 532.5-532.8 eV). However the XPS intensities give evidence of an uptake of oxygen accompanied by an increase of the surface coverage by Al3+ cations, and a decrease of the concentration in metallic Al at the alloy interface. A value of ∼2 for the oxygen to aluminium ions surface concentration ratio indicates the formation of an oxy-hydroxide (AlOxOHy with x + y ∼ 2) hydroxylation product. STM and LEED show the amorphisation and roughening of the oxide film. At P(H2O) = 1 × 10−7 mbar, only the surface of the oxide film is modified, with formation of nodules of ∼2 nm lateral size covering homogeneously the surface. STS shows that essentially the valence band is modified with an increase of the density of states at the band edge. With increasing pressure, hydroxylation is amplified, leading to an increased coverage of the alloy by oxy-hydroxide products and to the formation of larger nodules (∼7 nm) of amorphous oxy-hydroxide. Roughening and loss of the nanostructure indicate a propagation of the reaction that modifies the bulk structure of the oxide film. Amorphisation can be reverted to crystallization by annealing under UHV at 1025 K when the surface of the oxide film has been modified, but not when the bulk structure has been modified. 相似文献
42.
Luis L. Bonilla 《Journal of statistical physics》1987,46(3-4):659-678
A nonlinear Fokker-Planck equation is derived to describe the cooperative behavior of general stochastic systems interacting via mean-field couplings, in the limit of an infinite number of such systems. Disordered systems are also considered. In the weak-noise limit; a general result yields the possibility of having bifurcations from stationary solutions of the nonlinear Fokker-Planck equation into stable time-dependent solutions. The latter are interpreted as non-equilibrium probability distributions (states), and the bifurcations to them as nonequilibrium phase transitions. In the thermodynamic limit, results for three models are given for illustrative purposes. A model of self-synchronization of nonlinear oscillators presents a Hopf bifurcation to a time-periodic probability density, which can be analyzed for any value of the noise. The effects of disorder are illustrated by a simplified version of the Sompolinsky-Zippelius model of spin-glasses. Finally, results for the Fukuyama-Lee-Fisher model of charge-density waves are given. A singular perturbation analysis shows that the depinning transition is a bifurcation problem modified by the disorder noise due to impurities. Far from the bifurcation point, the CDW is either pinned or free, obeying (to leading order) the Grüner-Zawadowki-Chaikin equation. Near the bifurcation, the disorder noise drastically modifies the pattern, giving a quenched average of the CDW current which is constant. Critical exponents are found to depend on the noise, and they are larger than Fisher's values for the two probability distributions considered. 相似文献
43.
44.
It is shown that the potential perturbation that shifts a chosen standing wave in space is a block of potential barrier and well for every wave bump between neighbouring knots. The algorithms shifting the range of the primary localization of a chosen bound state in a potential well of finite width are as well applicable to the scattering functions if states of the continuous spectrum are considered as bound states normalized to unity but distributed on an infinite interval with vanishing density. The potential perturbations of the same type on the half-axis concentrate the scattering wave at the origin, thus creating a bound state embedded into the continuous spectrum (zero width resonance). 相似文献
45.
Yan Zhibin 《东北数学》1998,(2)
SomeNotesaboutTanaka'sEquationYanZhibin(严质彬)(DepartmentofMathematics,HarbinInstituteofTechnology,Harbin,150001)AbstractLet{Wt... 相似文献
46.
本文是[1,12]的继续,研究描述架中概念的结构;本文讨论后半部分,内容涉及概念内涵与外延的转换,清晰关系的内投影与内变换,概念的结构*以及有关问题的注记。 相似文献
47.
本文首先提出逆(反)对策这一新问题,给出了数学模型;探讨了“奇门遁甲”预测理论(术)中的数学问题;通过系统分析“专门遁甲”预测过程,可知它的预测过程隐含着一个特殊的逆(反)对策问题;最后指出逆(反)对策问题的广泛存在并给出案例分析. 相似文献
48.
Xu Tianzhou 《东北数学》1997,(1)
ModulesoverOperatorAlgebrasandItsModuleMapsXuTianzhou(许天周)(DepartmentofMathematics,NanjingUniersity,Nanjing,210093)AbstractLe... 相似文献
49.
对一类变形的变分不等式:求,使得提出了一类投影收缩算法,并得到了该算法的收敛性及相关性质. 相似文献
50.
A complete study of the spectrum of a finite-dimensional Bose operator is carried out in the paper. The cases in which the
spectrum is discrete or continuous are studied.
Translated fromMatematicheskie Zametki, Vol. 61, No. 6, pp. 835–854, June, 1997.
Translated by A. M. Chebotarev 相似文献