全文获取类型
收费全文 | 556528篇 |
免费 | 5953篇 |
国内免费 | 2012篇 |
专业分类
化学 | 285901篇 |
晶体学 | 7811篇 |
力学 | 26370篇 |
综合类 | 12篇 |
数学 | 86568篇 |
物理学 | 157831篇 |
出版年
2020年 | 3734篇 |
2019年 | 4007篇 |
2018年 | 14760篇 |
2017年 | 14479篇 |
2016年 | 13334篇 |
2015年 | 6010篇 |
2014年 | 7968篇 |
2013年 | 21871篇 |
2012年 | 19665篇 |
2011年 | 29558篇 |
2010年 | 18503篇 |
2009年 | 18710篇 |
2008年 | 24678篇 |
2007年 | 26935篇 |
2006年 | 18227篇 |
2005年 | 17521篇 |
2004年 | 16091篇 |
2003年 | 15036篇 |
2002年 | 13895篇 |
2001年 | 14563篇 |
2000年 | 11377篇 |
1999年 | 8778篇 |
1998年 | 7356篇 |
1997年 | 7206篇 |
1996年 | 7118篇 |
1995年 | 6270篇 |
1994年 | 6063篇 |
1993年 | 5924篇 |
1992年 | 6425篇 |
1991年 | 6392篇 |
1990年 | 6061篇 |
1989年 | 5838篇 |
1988年 | 6065篇 |
1987年 | 5756篇 |
1986年 | 5512篇 |
1985年 | 7663篇 |
1984年 | 7867篇 |
1983年 | 6414篇 |
1982年 | 6973篇 |
1981年 | 6911篇 |
1980年 | 6547篇 |
1979年 | 6810篇 |
1978年 | 6928篇 |
1977年 | 6892篇 |
1976年 | 6860篇 |
1975年 | 6603篇 |
1974年 | 6470篇 |
1973年 | 6770篇 |
1972年 | 4151篇 |
1971年 | 3340篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
Growth of thin Ti films on (100)W and the kinetics of their oxidation are studied using thermal-desorption spectroscopy and Auger electron spectroscopy. Titanium films grow nearly layer by layer on the (100)W face at room temperature. The activation energy for desorption of Ti atoms decreases from 5.2 eV for coverage θ=0.1 to 4.9 eV in a multilayer film. Oxidation of a thin (θ=6) titanium film starts with dissolution of oxygen atoms in its bulk to the limiting concentration for a given temperature, after which the film oxidizes to TiO, with the TiO2 oxide starting to grow when exposure of the film to oxygen is prolonged. The thermal desorption of oxides follows zero-order kinetics and is characterized by desorption activation energies of 5.1 (TiO) and 5.9 eV (TiO2). 相似文献
912.
The integral characteristics of magnetization switching in amorphous gadolinium-cobalt films with perpendicular anisotropy
are studied by visualizing the domain structure and measuring magnetooptic hysteresis loops. The films have a radial gradient
of magnetic properties that is due to a spatially nonuniform thermal field. Magnetization switching in those film areas where
the domain wall motion depends only on the coercive force is simulated in simple terms. In a first approximation, local events
of magnetization switching are shown to take place independently of each other and the net hysteresis loop can be represented
as a sum of the local loops. 相似文献
913.
E. L. Pankratov 《Technical Physics》2004,49(1):114-118
The establishment of the steady-state dopant profile in a medium with a time-variable diffusion coefficient is considered
within the approach proposed previously for estimating mass-and heat-transfer time characteristics. It is shown that the time
it takes for the equilibrium concentration to set in may be increased or decreased by appropriately choosing the law of variation
of the diffusion coefficient. 相似文献
914.
Dineykhan M. Zhaugasheva S. A. Kozhamkulov T. A. Petrov E. V. 《Russian Physics Journal》2004,47(12):1250-1260
The mass spectrum of a coupled state is analytically determined. The mechanism of production of a constituent mass of particles forming a coupled state is explained. The change of the coupled state and constituent particle component masses attendant to changes of the coupling constant is analyzed. The mass spectrum of a two-gluon glueball is determined with allowance for spin-orbital and spin-spin interactions.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 33–41, December, 2004. 相似文献
915.
The study of the effect of a perfectly conducting plane placed at a certain distance from the surface of a potassium niobate crystal on the characteristics of the generalized Rayleigh and Gulyaev-Bleustein surface waves is continued. In addition, the effect of an infinitely thin conducting layer applied to the surface of the piezoelectric on the characteristics of these waves is analyzed. It is found that a variation in the conductance of this layer can produce a result that completely differs from the result obtained when a perfectly conducting plane is moved toward the surface, although the extreme states of these actions (electrically open and short-circuited surfaces) are identical. A possible physical explanation of this difference is proposed. 相似文献
916.
A hydrophone calibration procedure that considerably reduces the error caused by the acoustic field distortions in a hydroacoustic tank is proposed. The procedure is based on the definition of the reduced electric transfer impedances of transducers (i.e., the electric transfer impedances reduced to the spherical wave propagation law) and consists in measuring the electric transfer impedances for different distances between hydroacoustic transducers. The sensitivity of the hydrophone under calibration is calculated from the far-field values of the reduced electric transfer impedances. The latter are determined using a mathematical model of the hydrophone in the form of a system that contains a point sensing element and a finite number of point sources of acoustic signals (point reflectors). A method of determining the number and coordinates of the point reflectors from the analysis of the acoustic “images” of the hydrophone’s reflecting surface is proposed. The measuring technique, the algorithms of mathematical processing, and the results of experimental studies are considered. A comparative analysis of the results of the hydrophone calibration with respect to the field by the reciprocity method is performed for the cases of using the conventional technique and the proposed method. 相似文献
917.
E. V. Aksenova A. Yu. Val’kov A. A. Karetnikov A. P. Kovshik V. P. Romanov E. I. Ryumtsev 《Journal of Experimental and Theoretical Physics》2004,99(5):965-977
The phenomenon of extraordinary ray refraction in a helical liquid crystal with large (compared to the light wavelength) pitch has been studied by theoretical and experimental methods. At a sufficiently large angle of incidence relative to the pitch axis, the extraordinary ray exhibits reflection (reversal) from a certain layer of the medium. The ordinary ray, for which the system is optically isotropic, exhibits no such reflection. The experimental dependences of the transmitted and reflected (reversed) rays are described using the geometrical optics approximation taking into account the optical losses for scattering inside the liquid crystal. 相似文献
918.
The magnetic absorption cross section of a small spherical particle with a dielectric core and a metallic shell is calculated. The general case is considered when the ratio of the radius of the dielectric core to the total radius of the particle may take arbitrary values. The condition of specular-diffuse reflection of conduction electrons from the surfaces of the metal layer of the particle is chosen as the boundary conditions of the problem. The limit cases are considered, and the results are discussed. 相似文献
919.
S. A. Sadovsky Yu. V. Kharlov A. L. S. Angelis E. Gładysz-Dziaduś V. L. Korotkikh G. Mavromanolakis A. D. Panagiotou 《Physics of Atomic Nuclei》2004,67(2):396-405
A phenomenological model for describing the production of Centauro events in relativistic heavy-ion collisions is discussed. The model provides quantitative predictions for kinematical variables, for the baryon number, and for the masses of a Centauro fireball and of its decay products. A Centauro fireball decays predominantly into nucleons, strange hyperons, and possibly strangelets. Centauro events in Pb + Pb collisions at the LHC energy are simulated for the CASTOR detector. The signatures of these events are discussed in detail. 相似文献
920.
E. V. McCloskey A. Dey R. M. Parr N. Aras A. Balogh J. Bostock A. Borell S. Krishnan G. Lobo L. L. Qin Y. Zhang S. Cvijetic V. Zaichick M. Lim-Abraham K. Bose S. Wynchank G. V. Iyengar 《Journal of Radioanalytical and Nuclear Chemistry》2004,259(2):341-345
In 1994, the International Atomic Energy Agency (IAEA) initiated a 5-year Co-ordinated Research Project (CRP) to determine
geographical and racial differences in peak bone mineral density (BMD) in men and women aged 15-49 years. The study demonstrates
that there are distinct global differences in BMD at the hip and spine in both men and women approximating to one population
standard deviation between populations with the highest and lowest BMD. These differences persist following adjustments for
age, sex and body size. Such information is valuable in understanding the reasons for global differences in fracture rate
and predicting future trends in fracture incidence.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献