全文获取类型
收费全文 | 19498篇 |
免费 | 2543篇 |
国内免费 | 1517篇 |
专业分类
化学 | 7020篇 |
晶体学 | 266篇 |
力学 | 298篇 |
综合类 | 33篇 |
数学 | 544篇 |
物理学 | 11945篇 |
无线电 | 3452篇 |
出版年
2024年 | 34篇 |
2023年 | 145篇 |
2022年 | 313篇 |
2021年 | 390篇 |
2020年 | 386篇 |
2019年 | 422篇 |
2018年 | 436篇 |
2017年 | 569篇 |
2016年 | 810篇 |
2015年 | 739篇 |
2014年 | 943篇 |
2013年 | 1708篇 |
2012年 | 1139篇 |
2011年 | 1462篇 |
2010年 | 1021篇 |
2009年 | 1339篇 |
2008年 | 1246篇 |
2007年 | 1421篇 |
2006年 | 1134篇 |
2005年 | 992篇 |
2004年 | 909篇 |
2003年 | 734篇 |
2002年 | 743篇 |
2001年 | 643篇 |
2000年 | 595篇 |
1999年 | 508篇 |
1998年 | 393篇 |
1997年 | 288篇 |
1996年 | 339篇 |
1995年 | 293篇 |
1994年 | 231篇 |
1993年 | 204篇 |
1992年 | 207篇 |
1991年 | 133篇 |
1990年 | 103篇 |
1989年 | 100篇 |
1988年 | 87篇 |
1987年 | 58篇 |
1986年 | 38篇 |
1985年 | 53篇 |
1984年 | 41篇 |
1983年 | 21篇 |
1982年 | 36篇 |
1981年 | 37篇 |
1980年 | 17篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1976年 | 14篇 |
1975年 | 9篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Alloy formation at the Ni–Al interface for thin nickel films deposited on Al(110) surfaces has been studied using high-energy ion scattering/channeling (HEIS) and X-ray photoelectron spectroscopy (XPS). For nickel atoms deposited at room temperature on Al(110), a large amount of nickel–aluminum intermixing occurs at the interface. For the first two monolayers (ML) of deposited nickel, an NiAl-like compound is formed. The intermixing continues with a different rate, forming an Ni3Al-like compound for nickel coverages from 2 to 8 ML, at which point a nickel metal film begins to grow on the surface. Nickel atoms deposited at 250°C on the Al(110) surface exhibit no surface compound formation, but diffuse up to 400 Å into the aluminum substrate. Interatomic potentials based on the embedded-atom method (EAM) are used in a Monte Carlo approach to simulate the evolution of the Ni–Al(110) interface as a function of the nickel coverage. The calculated ion-scattering yields and X-ray photoelectron intensities from nickel and aluminum atoms in these simulated interfaces are in good quantitative agreement with the experimental results. The simulations show a high-density Ni–Al alloy forming at the Al(110) surface which apparently inhibits outward diffusion of aluminum, leading to the more nickel-rich alloy and finally nickel film growth. The ion-scattering simulations show an unusually large amount of backscattering occurring below the Ni–Al(110) interface, apparently associated with defocusing of the incident ion beam. 相似文献
992.
N. Bernhoeft 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(4):685-694
The heavy fermion compound UPd2Al3 has attracted much interest on account of the coexistence of antiferromagnetism and superconductivity at temperatures below
2 K. The antiferromagnetic fluctuations provide, principally via inelastic neutron scattering, a window on the low frequency dynamics in this material. By an analysis of neutron scattering
data, and taking into consideration results from other experimental probes, it is suggested which sheet(s) of the f-electron Fermi surface may play an active role in forming the superconducting state in UPd2Al3. The proposed scheme sheds new light on previously reported anomalies in this material.
Received 16 July 1999 相似文献
993.
A. Paolone P. Roy A. Pimenov A. Loidl A.A. Mukhin A.M. Balbashov 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(2):245-250
The optical conductivity of La0.85Sr0.15MnO3 single crystals was studied by means of submillimeter and infrared spectroscopy for frequencies cm-1 and temperatures 10 K <
T
<300 K. The submillimeter conductivity follows the temperature dependence of the dc-data. The phonon spectrum of La0.85Sr0.15MnO3 changes considerably below K revealing a structural phase transition induced by charge or orbital order. At T
=10 K a number of phonon modes can be identified in addition to the room-temperature spectrum. The optical conductivity () in the mid-infrared reveals the characteristics of small polaron absorption. Below the magnetic ordering temperature the
polaron binding energy is highly reduced, but the onset of charge order interrupts the formation of free charge carriers with
a Drude-like behavior. The frequency and temperature dependence of in this regime qualitatively resembles the small polaron predictions by Millis et al. (Phys. Rev. B 54, 5405 (1996)).
Received 5 November 1999 相似文献
994.
Using small-angle X-ray scattering, the repeat distance vs. temperature is measured for a homologous series of multilamellar vesicles of lecithins with varying acyl chain length in
excess water condition around the lipid main transition. A systematic chain length dependence is found which is in accordance
with a bending rigidity renormalization and critical unbinding of the lamellae close to the transition, as previously suggested
in H?nger et al. [Phys. Rev. Lett. 72, 3911 (1994)].
Received 13 January 1999 and Received in final form 6 September 1999 相似文献
995.
R. Röhlsberger 《Hyperfine Interactions》2000,126(1-4):425-429
A coherently excited nuclear state is carried with a rotating sample so that its radiative decay is redirected by the rotation
angle that has developed during its lifetime. As a result, the time spectrum of the nuclear decay is mapped to an angular
scale. This effect has been observed in nuclear resonant scattering of synchrotron radiation from a rotating 57Fe metal foil. Applications with respect to elastic and inelastic nuclear resonant scattering are discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
996.
Fractal Characteristics Investigation on Light Scattering from Two Dimensional Rough Surface 总被引:2,自引:0,他引:2
A normalized two dimensional band-limited Weierstrass fractal function is used for modeling the rough surface. Based on Kirchhoff theory, an analytic solution of the average scattering field and the variance of scattering intensity are derived with emphasis on examining the relation of fractal dimension with the scattering pattern. The important conclusion is obtained that the diffracted envelope slopes of scattering pattern can be approximated to a slope of linear equation. 相似文献
997.
A. Li Bassi C.E. Bottani B.K. Tanner A. Stella P. Tognini P. Cheyssac R. Kofman 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(1):31-38
The abrupt change of velocity in surface acoustic waves in thin films of amorphous SiOx containing nanometre scale -Sn crystals is shown to be directly associated with the size-dependent melting of the nanoparticles, confirming preliminary
experiments. High resolution thin film powder diffraction using synchrotron radiation shows that the abrupt redshift in the
Brillouin spectra satellites occurs at the same temperature as the melting of the nanoparticles, evident for the loss of the
Bragg peaks. Effective medium theory is used to explain the origin of the anomaly. A central peak in the Brillouin spectrum,
the intensity of which shows a maximum at the melting temperature, can be interpreted in terms of overdamped fluctuations
in the dielectric function. The melting temperature as a function of particle size is in agreement with theoretical predictions.
No evidence for strain could be found on the X-ray diffraction profiles; the a- and c-axis thermal expansion coefficients are the same as those in bulk tin.
Received 30 March 2000 and Received in final form 24 July 2000 相似文献
998.
J. Hüfner Y.B. He B.Z. Kopeliovich 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):239-244
Prompt gluons are an additional source for charmonium suppression in nuclear collisions, in particular for nucleus-nucleus
collisions. These gluons are radiated as bremsstrahlung in N-N collisions and interact inelastically with the charmonium states
while the nuclei still overlap. The spectra and mean number <n
g> of the prompt gluons are calculated perturbatively and the inelastic cross section σabs
Ψg is estimated. The integrated cross sections σ(A B →J/ψX) for p-A and A-B collisions and the dependence on transverse energy for S-U and Pb-Pb can be described quantitatively with
some adjustment of one parameter <n
g>σabs
Ψg.
Received: 20 August 1999 相似文献
999.
W. B. Dou Edward K. N. Yung 《International Journal of Infrared and Millimeter Waves》2000,21(6):1001-1017
The scattering field of a ferrite post and a cylindrical ferrite post containing conducting post illuminated by a plane wave is analyzed. The special interest is the scattering property of the ferrite posts, which is resonating at certain modes such as TM11 mode. We hope to know the speciality it shows and find its applications. It is found that the scattering field pattern of a resonating ferrite post is similar to the rotation of the scattering field pattern of a dielectric cylindrical post, which has the same dimension as ferrite. The scattering properties of the ferrite may give us some inspirations to explore its applications in microwave components. This property is utilized to explain the mechanism of the operation of the circulators. It also may be used in microstrip patch antenna, coupler and filter to control their properties. Other applications may be possible too. Some calculation results are presented. 相似文献
1000.
The effect of the pump bandwidth on the quantum statistical properties of Raman lasers is investigated. It is shown that the pump bandwidth may lead to the enhancement of output intensity noise squeezing even though it reduces the Mandel Q parameter. 相似文献