全文获取类型
收费全文 | 6886篇 |
免费 | 381篇 |
国内免费 | 403篇 |
专业分类
化学 | 1312篇 |
晶体学 | 75篇 |
力学 | 462篇 |
综合类 | 58篇 |
数学 | 3516篇 |
物理学 | 2247篇 |
出版年
2023年 | 36篇 |
2022年 | 51篇 |
2021年 | 74篇 |
2020年 | 90篇 |
2019年 | 94篇 |
2018年 | 74篇 |
2017年 | 111篇 |
2016年 | 102篇 |
2015年 | 94篇 |
2014年 | 146篇 |
2013年 | 407篇 |
2012年 | 212篇 |
2011年 | 297篇 |
2010年 | 317篇 |
2009年 | 773篇 |
2008年 | 765篇 |
2007年 | 641篇 |
2006年 | 598篇 |
2005年 | 349篇 |
2004年 | 261篇 |
2003年 | 282篇 |
2002年 | 283篇 |
2001年 | 229篇 |
2000年 | 180篇 |
1999年 | 183篇 |
1998年 | 192篇 |
1997年 | 128篇 |
1996年 | 92篇 |
1995年 | 69篇 |
1994年 | 86篇 |
1993年 | 44篇 |
1992年 | 46篇 |
1991年 | 45篇 |
1990年 | 33篇 |
1989年 | 24篇 |
1988年 | 30篇 |
1987年 | 22篇 |
1986年 | 22篇 |
1985年 | 21篇 |
1984年 | 27篇 |
1983年 | 16篇 |
1982年 | 27篇 |
1981年 | 17篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 15篇 |
1976年 | 10篇 |
1974年 | 5篇 |
1973年 | 5篇 |
排序方式: 共有7670条查询结果,搜索用时 375 毫秒
81.
教学研究:介绍量子力学几个基本概念——兼答《关于量子几何相位的评注》中的几个主要问题 总被引:4,自引:4,他引:0
介绍了量子绝热定理的物理含义及成立的条件,认为有关主要献(Aharonov-Anandan,Bohm,孙昌璞等)的表述是正确的,而《关于量子几何相位的评注》^[1](以下简称《评注》)相应的表述不完全正确。在此基础上,认为这些献和教材(R.Shankar)得出的涉及Berry绝热相位的一些论述(不含Berry绝热相因子的瞬时能量本征态不满足含时Schroedinger方程等)也是正确的,而《评注》的论述与此相反。《评注》认为只有γn(C)才是Berry相位。本作则倾向于把γn(t)叫做Berry绝热相位,而把γn(C)=γn(T)-γn(0)叫做几何相位(geometric phase)^[2]。 相似文献
82.
利用平均值不等式 ,得到关于矩阵迹的不等式 :如果 A1 ,A2 ,… ,Am 皆为 n阶 Hermite半正定矩阵 ,且乘法两两可交换 ,0 相似文献
83.
Maciej Janowicz 《Reports on Mathematical Physics》2004,54(1):57-69
Properties of a four-level atomic system interacting with one and two modes of the electromagneticfield in a “Ξ”-configuration are investigated. By linearization of the Hamiltonians we show that the corresponding mathematical models are exactly solvable. To obtain simpler effective Hamiltonians the perturbative method of multiple scales is applied. The lowest-order corrections to the resulting effective evolution operators are also calculated. 相似文献
84.
T. Butz Ch. Meinecke M. Morawski T. Reinert M. Schwertner D. Spemann J. Vogt 《Applied Surface Science》2005,252(1):43-48
This contribution deals with the morphological and elemental characterisation with high-energy (MeV) focused ion beams (in particular protons) with special emphasis on high spatial resolution in the sub-micrometer regime and very low minimum detection limits (sub-ppm) in trace element analysis. The most important methods like particle induced X-ray emission (PIXE), Rutherford backscattering spectrometry (RBS), as well as scanning transmission ion microscopy (STIM) and STIM-tomography will be illustrated by examples from material and life sciences. 相似文献
85.
The question about the definition of the “internal pressure” concept is being discussed. It is shown that the previously found differential relation between the cohesion energy density and the internal pressure is one of the examples of an absolutely general interrelation between definitely connected differential functions. It is ascertained that the ratio (the internal pressure divided by the cohesion energy density) is a structuresensitive parameter inherent to the calorific (thermal) equation of a liquid state. 相似文献
86.
The deposition of decomposed ethylene on silicon wafer at lower temperature using hot filament chemical vapor deposition (HFCVD) method was applied to compose thin film of carbon and its compounds with silicon and hydrocarbon structures. The films were analyzed using Raman spectroscopy, X-ray diffraction, and scanning electron microscopy with elemental microanalysis by energy dispersive X-ray spectrometer. The structure and morphology of the early stage of the film deposition was analyzed. The obtaining of SiC as well as diamond-like structure with this method and catalytic influence of chemical admixtures on the film structure and properties are discussed. 相似文献
87.
Michael-Addition Reaction of Malononitrile with a,β-Unsaturated Cycloketones Catalyzed by KF/Al_2O_3
The utility of fluoride salts as potential base in a va-riety of synthetic reactions has been recognized in re-cent years.1 However, low solubility of fluoride salts in ordinary solvents hampers their wide applications in organic synthesis. On the other hand, there has been increasing use of inorganic solid supports as catalysts for many years2 resulting in higher selectivity, milder reaction conditions and easier work-up. Especially po-tassium fluoride-coated alumina (KF-alumina) has been a … 相似文献
88.
We introduce a generalized notion of semiring and prove that all known properties that semirings have according to the old definition are preserved. 相似文献
89.
For the purpose of testing the spherical uniformity based on i.i.d. directional data (unit vectors) zi, i=1,…,n, Anderson and Stephens (Biometrika 59 (1972) 613–621) proposed testing procedures based on the statistics Smax=maxu S(u) and Smin=minu S(u), where u is a unit vector and nS(u) is the sum of squares of u′zi's. In this paper, we also consider another test statistic Srange=Smax−Smin. We provide formulas for the P-values of Smax, Smin, Srange by approximating tail probabilities of the limiting null distributions by means of the tube method, an integral-geometric approach for evaluating tail probability of the maximum of a Gaussian random field. Monte Carlo simulations for examining the accuracy of the approximation and for the power comparison of the statistics are given. 相似文献
90.
Mursaleen 《Journal of Mathematical Analysis and Applications》2004,293(2):523-531
The idea of almost convergence for double sequences was introduced by Moricz and Rhoades [Math. Proc. Cambridge Philos. Soc. 104 (1988) 283-294] and they also characterized the four dimensional strong regular matrices. In this paper we define and characterize the almost strongly regular matrices for double sequences and apply these matrices to establish a core theorem. 相似文献