全文获取类型
收费全文 | 476560篇 |
免费 | 3725篇 |
国内免费 | 1449篇 |
专业分类
化学 | 234143篇 |
晶体学 | 7257篇 |
力学 | 24510篇 |
综合类 | 12篇 |
数学 | 77486篇 |
物理学 | 138326篇 |
出版年
2020年 | 3206篇 |
2019年 | 3576篇 |
2018年 | 14627篇 |
2017年 | 14514篇 |
2016年 | 12844篇 |
2015年 | 5006篇 |
2014年 | 7081篇 |
2013年 | 17360篇 |
2012年 | 16169篇 |
2011年 | 25096篇 |
2010年 | 16375篇 |
2009年 | 16547篇 |
2008年 | 20580篇 |
2007年 | 22704篇 |
2006年 | 13884篇 |
2005年 | 13512篇 |
2004年 | 12829篇 |
2003年 | 12208篇 |
2002年 | 11087篇 |
2001年 | 11558篇 |
2000年 | 8961篇 |
1999年 | 6850篇 |
1998年 | 5965篇 |
1997年 | 5823篇 |
1996年 | 5547篇 |
1995年 | 5150篇 |
1994年 | 5209篇 |
1993年 | 4907篇 |
1992年 | 5520篇 |
1991年 | 5506篇 |
1990年 | 5365篇 |
1989年 | 5212篇 |
1988年 | 5262篇 |
1987年 | 5154篇 |
1986年 | 4925篇 |
1985年 | 6458篇 |
1984年 | 6744篇 |
1983年 | 5817篇 |
1982年 | 5965篇 |
1981年 | 5776篇 |
1980年 | 5716篇 |
1979年 | 5816篇 |
1978年 | 6147篇 |
1977年 | 6002篇 |
1976年 | 6104篇 |
1975年 | 5723篇 |
1974年 | 5744篇 |
1973年 | 6028篇 |
1972年 | 4184篇 |
1971年 | 3441篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
L. Resse L.G.S. Oliveira C.I.L. de Araujo A.R. Pereira R.L. Silva 《Physics letters. A》2019,383(14):1655-1659
In this work, we have used the MuMax3 software to simulate devices consisting of a ferromagnetic thin film placed over a heavy metal thin film. The devices are two interconnected partial-disks where a Néel domain wall is formed in the disks junction. In our simulations we investigate devices with disk radius nm and different distance d between the disks centers (from nm to nm). By applying strong sinusoidal external magnetic fields, we find a mechanism able to create, annihilate and even manipulate a skyrmion in each side of the device. This mechanism is discussed in terms of interactions between skyrmion and domain wall. The Néel domain wall formed in the center of the device interacts with the Néel skyrmion, leading to a process of transporting a skyrmion from one disk to the other periodically. Our results have relevance for potential applications in spintronics such as logical devices. 相似文献
3.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films
were investigated using a number of techniques. A high saturation magnetic induction up to B
s
= 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed,
which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of
the composition.
The text was submitted by the authors in English. 相似文献
4.
The lidar equation for the vibrational backscattering of neodymium laser radiation and its harmonics by hydrogen molecules
is solved numerically. Inclined paths in the atmosphere are investigated with the aim of selecting the transmitter wavelength
for detecting the lowest concentrations of hydrogen.
Zh. Tekh. Fiz. 68, 20–22 (January 1998) 相似文献
5.
G. Ch. Shushkevich 《Technical Physics》1998,43(7):743-748
The electrostatic problem for a thin, unclosed spherical shell and a torus is reduced to paired summation equations in the
Legendre polynomials by means of formulas relating the spherical and toroidal harmonic functions. The paired equations are
transformed to a Fredholm integral equation of the second kind. Formulas are obtained for computing the charges of the conductors
in the form of a series in a small parameter. The capacitance is computed for certain geometrical parameters of the conductors.
Zh. Tekh. Fiz. 68, 1–6 (July 1998) 相似文献
6.
7.
C. Waldtmann H.-U. Everts B. Bernu C. Lhuillier P. Sindzingre P. Lecheminant L. Pierre 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(4):501-507
We study the exact low energy spectra of the spin 1/2 Heisenberg antiferromagnet on small samples of the kagomé lattice of up to N=36 sites. In agreement with the conclusions of previous authors, we find that these low energy spectra contradict the hypothesis
of Néel type long range order. Certainly, the ground state of this system is a spin liquid, but its properties are rather
unusual. The magnetic () excitations are separated from the ground state by a gap. However, this gap is filled with nonmagnetic () excitations. In the thermodynamic limit the spectrum of these nonmagnetic excitations will presumably develop into a gapless
continuum adjacent to the ground state. Surprisingly, the eigenstates of samples with an odd number of sites, i.e. samples with an unsaturated spin, exhibit symmetries which could support long range chiral order. We do not know if these
states will be true thermodynamic states or only metastable ones. In any case, the low energy properties of the spin 1/2 Heisenberg
antiferromagnet on the kagomé lattice clearly distinguish this system from either a short range RVB spin liquid or a standard chiral spin liquid. Presumably
they are facets of a generically new state of frustrated two-dimensional quantum antiferromagnets.
Received: 27 November 1997 / Accepted: 29 January 1998 相似文献
8.
C. Fallnich B. Ruffing Th. Herrmann A. Nebel R. Beigang R. Wallenstein 《Applied physics. B, Lasers and optics》1995,60(5):427-436
We report on a cw mode-locked non-critically phase matched KTP optical parametric oscillator synchronously pumped by a picosecond Ti:Sapphire laser. High average signal output power of up to 950 mW over a large tuning range has been achieved. For this OPO the influence of resonator-length detuning on the output power, pulse duration and spectral bandwidth has been investigated. The measured data are in good agreement with the results of a numerical simulation using a split-step Fourier method which considers the group-velocity mismatch, the group-velocity dispersion and the self-phase modulation. The numerical simulation also describes the measured strong pump depletion and its influence on the OPO output and efficiency. 相似文献
9.
We report on the first observation and studies of a weak delocalizing logarithmic temperature dependence of the conductivity,
which causes the conductivity of the 2D metal to increase as T decreases down to 16 mK. The prefactor of the logarithmic dependence is found to decrease gradually with density, to vanish
at a critical density n
c
, 2∼2×1012 cm−2, and then to have the opposite sign at n>n
c
,2. The second critical density sets the upper limit on the existence region of the 2D metal, whereas the conductivity at the
critical point, G
c
,2∼120e
2/h, sets an upper (low-temperature) limit on its conductivity.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 6, 497–501 (25 September 1998)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
10.
S. A. Gurevich T. A. Zaraiskaya S. G. Konnikov V. M. Mikushkin S. Yu. Nikonov A. A. Sitnikova S. E. Sysoev V. V. Khorenko V. V. Shnitov Yu. S. Gordeev 《Physics of the Solid State》1997,39(10):1691-1695
The concentration and chemical state of copper in the subsurface region of Cu/SiO2 composite films obtained by simultaneous magnetron sputtering from two sources (Cu and SiO2) are determined by x-ray photoelectron spectroscopy (XPS). It is established that copper in the as-grown film is primarily in the form of unoxidized atoms dispersed in a SiO2 matrix. Annealing of the film results in practically no oxidation, but about 70% of the copper atoms condense into metallic clusters with sizes below 10 Å in the subsurface region and about 50 Å in the bulk of the film. The changes in the binding energy of core electrons, and especially in the energies of Auger electrons, are so large in this situation that photoelectron and Auger spectroscopy are efficient methods for monitoring the chemical state of this composite material. 相似文献