全文获取类型
收费全文 | 52982篇 |
免费 | 1826篇 |
国内免费 | 70篇 |
专业分类
化学 | 34189篇 |
晶体学 | 252篇 |
力学 | 1678篇 |
数学 | 8303篇 |
物理学 | 10456篇 |
出版年
2023年 | 418篇 |
2022年 | 385篇 |
2021年 | 615篇 |
2020年 | 779篇 |
2019年 | 710篇 |
2018年 | 1072篇 |
2017年 | 881篇 |
2016年 | 1670篇 |
2015年 | 1533篇 |
2014年 | 1580篇 |
2013年 | 3183篇 |
2012年 | 3645篇 |
2011年 | 3797篇 |
2010年 | 2303篇 |
2009年 | 1876篇 |
2008年 | 3227篇 |
2007年 | 3234篇 |
2006年 | 2818篇 |
2005年 | 2727篇 |
2004年 | 2362篇 |
2003年 | 1898篇 |
2002年 | 1671篇 |
2001年 | 973篇 |
2000年 | 800篇 |
1999年 | 589篇 |
1998年 | 434篇 |
1997年 | 402篇 |
1996年 | 507篇 |
1995年 | 325篇 |
1994年 | 371篇 |
1993年 | 374篇 |
1992年 | 398篇 |
1991年 | 333篇 |
1990年 | 322篇 |
1989年 | 317篇 |
1988年 | 256篇 |
1987年 | 263篇 |
1986年 | 233篇 |
1985年 | 398篇 |
1984年 | 368篇 |
1983年 | 255篇 |
1982年 | 341篇 |
1981年 | 323篇 |
1980年 | 276篇 |
1979年 | 279篇 |
1978年 | 259篇 |
1976年 | 268篇 |
1975年 | 246篇 |
1974年 | 253篇 |
1973年 | 248篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
M. Dubé C. Daneault V. Vuorinen M. Alava M. Rost 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(1):15-26
We investigate the structure and dynamics of the interface between
two immiscible liquids in a three-dimensional disordered porous
medium. We apply a phase-field model that includes explicitly
disorder and discuss both spontaneous and forced imbibition.
The structure of the interface is dominated by a length scale
ξ× which arises from liquid conservation. We further show
that disorder in the capillary and permeability act on different
length scales and give rise to different scalings and
structures of the interface properties. We conclude with a
range of applications. 相似文献
32.
Optimal explicit Runge–Kutta methods consider more stages in order to include a particular spectrum in their stability domain
and thus reduce time-step restrictions. This idea, so far used mostly for real-line spectra, is generalized to more general
spectra in the form of a thin region. In thin regions the eigenvalues may extend away from the real axis into the imaginary
plane. We give a direct characterization of optimal stability polynomials containing a maximal thin region and calculate these
polynomials for various cases. Semi-discretizations of hyperbolic–parabolic equations are a relevant application which exhibit
a thin region spectrum. As a model, linear, scalar advection–diffusion is investigated. The second-order-stabilized explicit
Runge–Kutta methods derived from the stability polynomials are applied to advection–diffusion and compressible, viscous fluid
dynamics in numerical experiments. Due to the stabilization the time step can be controlled solely from the hyperbolic CFL
condition even in the presence of viscous fluxes. 相似文献
33.
G. Bouwmans B. Ségard P. Glorieux P. A. Khandokhin N. D. Milovsky E. Yu. Shirokov 《Radiophysics and Quantum Electronics》2004,47(10-11):729-742
This paper is devoted to the polarization dynamics of a longitudinally monomode bipolarized Nd:YAG laser: the low-frequency polarization dynamics of a microchip laser is studied experimentally and theoretically. The intensities and the relaxation oscillation spectrum of orthogonally polarized modes versus the direction of pump polarization is observed. A phase-sensitive model of a longitudinally monomode bipolarized solid-state laser with linear polarized diode laser pump is developed to account for the experimental observations. 相似文献
34.
A palladium‐TPPTS catalyst heterogenized on KF/alumina has been shown to be effective and recyclable for the selective formation of monooctadienylxylopyranosides via the telomerization of butadiene with D ‐xylose. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
35.
A. Veiga N. Martínez P. Mendoza Zélis G. A. Pasquevich F. H. Sánchez 《Hyperfine Interactions》2006,167(1-3):905-909
A prototype of a programmable constant-velocity scaler is presented. This instrument allows the acquisition of partial Mössbauer spectra in selected energy regions using standard drivers and transducers. It can be fully operated by a remote application, thus data acquisition can be automated. The instrument consists of a programmable counter and a constant-velocity reference. The reference waveform generator is amplitude modulated with 13-bit resolution, and is programmable in a wide range of frequencies and waveforms in order to optimize the performance of the transducer. The counter is compatible with most standard SCA, and is configured as a rate-meter that provides counts per selectable time slice at the programmed velocity. As a demonstration of the instrument applications, a partial Mössbauer spectrum of a natural iron foil was taken. Only positive energies were studied in 512 channels, accumulating 20 s per channel. A line width of 0.20 mm/s was achieved, performing with an efficiency of 80%. 相似文献
36.
R. Euler B. Fricke T. Morović W. -D. Sepp A. Rosén 《Zeitschrift für Physik A Hadrons and Nuclei》1980,297(2):101-104
Total energy SCF calculations were performed for noble gas difluorides in a relativistic procedure and compared with analogous non-relativistic calculations. The discrete variational method with numerical basis functions was used. Rather smooth potential energy curves could be obtained. The theoretical Kr-F and Xe-F bond distances were calculated to be 3.5 a.u. and 3.6 a.u. which should be compared with the experimental values of 3.54 a.u. and 3.7 a.u. Although the dissociation energies are off by a factor of about five it was found that ArF2 may be a stable molecule. Theoretical ionization energies for the outer levels reproduce the experimental values for KrF2 and XeF2 to within 2 eV. 相似文献
37.
38.
39.
It is shown that the condition υ > υp (ω), which is necessary in order to trigger the Vavilov-Cherenkov effect, determines the interval of radiated frequencies
and it alone cannot establish a strong restriction to the velocity of the particle. It is exhibited that it is possible to
define a general lower bound for the velocity of the particle, which does not depend on the frequency when both, a specific
response of the medium is taken into account and the mentioned condition is considered. The minimum value of the phase velocity
of light in the medium determines the existence of such general lower bound. 相似文献
40.
It was studied the tin phase composition of the electrodeposited alloys produced at different temperatures and current densities from an acid chloride/fluoride electrolyte and an acid chloride bath. Mössbauer spectra were consistent with a Ni3Sn4 intermetallic compound, dissolved tin, and a Cu?Sn intermetallic compound formed at the interface of the copper substrate. 相似文献