全文获取类型
收费全文 | 1384710篇 |
免费 | 25921篇 |
国内免费 | 7792篇 |
专业分类
化学 | 686396篇 |
晶体学 | 21000篇 |
力学 | 76402篇 |
综合类 | 119篇 |
数学 | 248781篇 |
物理学 | 385725篇 |
出版年
2021年 | 13590篇 |
2020年 | 16034篇 |
2019年 | 16135篇 |
2018年 | 15912篇 |
2017年 | 14667篇 |
2016年 | 29472篇 |
2015年 | 21402篇 |
2014年 | 30709篇 |
2013年 | 74935篇 |
2012年 | 40100篇 |
2011年 | 39690篇 |
2010年 | 40089篇 |
2009年 | 42216篇 |
2008年 | 38379篇 |
2007年 | 35073篇 |
2006年 | 36848篇 |
2005年 | 32291篇 |
2004年 | 31927篇 |
2003年 | 29666篇 |
2002年 | 29960篇 |
2001年 | 28272篇 |
2000年 | 24787篇 |
1999年 | 22478篇 |
1998年 | 21094篇 |
1997年 | 21105篇 |
1996年 | 21191篇 |
1995年 | 19214篇 |
1994年 | 18697篇 |
1993年 | 18257篇 |
1992年 | 18101篇 |
1991年 | 18448篇 |
1990年 | 17563篇 |
1989年 | 17661篇 |
1988年 | 17209篇 |
1987年 | 17227篇 |
1986年 | 16067篇 |
1985年 | 22548篇 |
1984年 | 23829篇 |
1983年 | 19994篇 |
1982年 | 21702篇 |
1981年 | 20947篇 |
1980年 | 20299篇 |
1979年 | 20444篇 |
1978年 | 21781篇 |
1977年 | 21351篇 |
1976年 | 21072篇 |
1975年 | 19750篇 |
1974年 | 19406篇 |
1973年 | 19860篇 |
1972年 | 14341篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
F. Trani G. Cantele D. Ninno G. Iadonisi 《Physica E: Low-dimensional Systems and Nanostructures》2004,22(4):808-814
In this paper we report on tight-binding calculations of lowest unoccupied molecular orbitals states for silicon ellipsoidal nanocrystals. The electronic structure has been calculated for different nanocrystal shapes either keeping constant or varying the number of silicon atoms. We have found that changing the ellipsoid aspect ratio a non-obvious energy level structure is obtained. The implications for the infrared optical transitions and their relationship with the polarization of the radiation involved are discussed. 相似文献
992.
Relationships between the electrodynamic (wave propagation constants) and quantum-mechanical parameters (probability of induced transitions) of interaction between energy quanta and particles of the medium are derived for dipole and paramagnetic interaction types. It is demonstrated that quantum-mechanical parameters are generally complex. 相似文献
993.
The room temperature structure of perovskite CeAlO3 has been reinvestigated by X-ray powder diffraction. The Rietveld refinement has confirmed the tetragonal symmetry; but revealed a super cell, a=5.32489(6) Å and c=7.58976(10) Å, with the space group I4/mcm. In CeAlO3, the distortion from the ideal cubic perovskite is caused by the cooperative tilting of the AlO6 octahedra around the primitive cubic [001]p-axis. 相似文献
994.
R. K. Bairamov 《Russian Journal of Applied Chemistry》2003,76(10):1699-1701
Influence exerted by additives introduced into the working solution, by iron or copper formedin electric-spark dispersion of these metals and zinc, on the quality of the products obtained in electric erosionwas studied. 相似文献
995.
We establish the existence of a weak solution to the Dirichlet problem belonging to a Sobolev space for nonlinear elliptic equations of second order with right-hand sides from a wide class of functions defined in terms of the logarithmic function. 相似文献
996.
Previous studies of the initial stage of oxidation on clean single crystal of Cu(1 0 0) have been extended to the case of the Cu(1 1 0) surface. The dynamic observation of the nucleation and growth of Cu oxide by means of in situ ultra high vacuum transmission electron microscopy (UHV-TEM) shows a highly enhanced oxidation rate on Cu(1 1 0) surface as compared to Cu(1 0 0). The kinetic data on the nucleation and growth of the three-dimensional oxide islands agree well with our heteroepitaxial model of surface diffusion of oxygen. 相似文献
997.
The fine-structure parameters of a series of configurations of the first ion of indium and the gyromagnetic ratios in intermediate coupling are calculated by a semiempirical method in the single-configuration approximation. 相似文献
998.
999.
V. N. Popov 《Technical Physics》2003,48(5):541-545
The slip velocity of a rarefied gas nonuniform in temperature and mass velocity is calculated for gas slip over the surface
of a right circular cylinder. The calculation uses the two-moment boundary condition in an approximation linear in Knudsen
number. Corrections to the slip velocity that are due to the interface curvature, volume temperature stresses, and nonuniform
temperature distribution in the Knudsen layer are studied as func-tions of the accommodation coefficients in the first two
moments of the distribution function. The Bhatnagar-Gross-Krook model of the Boltzmann kinetic equation is employed as the
basic equation for the gas state. 相似文献
1000.
We study initial boundary value problems for linear scalar evolutionpartial differential equations, with spatial derivatives ofarbitrary order, posed on the domain {t > 0, 0 < x <L}. We show that the solution can be expressed as an integralin the complex k-plane. This integral is defined in terms ofan x-transform of the initial condition and a t-transform ofthe boundary conditions. The derivation of this integral representationrelies on the analysis of the global relation, which is an algebraicrelation defined in the complex k-plane coupling all boundaryvalues of the solution. For particular cases, such as the case of periodic boundaryconditions, or the case of boundary value problems for even-orderPDEs, it is possible to obtain directly from the global relationan alternative representation for the solution, in the formof an infinite series. We stress, however, that there existinitial boundary value problems for which the only representationis an integral which cannot be written as an infinite series.An example of such a problem is provided by the linearized versionof the KdV equation. Similarly, in general the solution of odd-orderlinear initial boundary value problems on a finite intervalcannot be expressed in terms of an infinite series. 相似文献