全文获取类型
收费全文 | 1376篇 |
免费 | 234篇 |
国内免费 | 154篇 |
专业分类
化学 | 649篇 |
晶体学 | 19篇 |
力学 | 10篇 |
综合类 | 15篇 |
数学 | 21篇 |
物理学 | 1050篇 |
出版年
2023年 | 13篇 |
2022年 | 40篇 |
2021年 | 36篇 |
2020年 | 46篇 |
2019年 | 35篇 |
2018年 | 42篇 |
2017年 | 58篇 |
2016年 | 55篇 |
2015年 | 46篇 |
2014年 | 71篇 |
2013年 | 97篇 |
2012年 | 89篇 |
2011年 | 74篇 |
2010年 | 66篇 |
2009年 | 87篇 |
2008年 | 77篇 |
2007年 | 78篇 |
2006年 | 66篇 |
2005年 | 54篇 |
2004年 | 49篇 |
2003年 | 52篇 |
2002年 | 47篇 |
2001年 | 50篇 |
2000年 | 44篇 |
1999年 | 43篇 |
1998年 | 28篇 |
1997年 | 19篇 |
1996年 | 44篇 |
1995年 | 21篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 15篇 |
1991年 | 4篇 |
1990年 | 9篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 61篇 |
1985年 | 25篇 |
1984年 | 35篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有1764条查询结果,搜索用时 15 毫秒
1.
Xiaofan Zhang 《中国物理 B》2022,31(11):114209-114209
We theoretically investigate the yield enhancement of elliptical high harmonics in the interaction of molecules with bicircular laser pulses by solving the time-dependent Schrödinger equation. It is shown that by adjusting the relative intensity ratio of the two bicircular field components in specific ranges the yield of the molecular high harmonics for the plateau and cutoff regions can be respectively enhanced. To analyze this enhancement phenomenon, we calculate the weights of the electron classical trajectories. Additionally, we also study the ellipticity distribution of harmonics for different intensity ratios. We find that these enhanced harmonics are elliptically polarized, which we mainly attribute to the recombination dipole moment of the major weighted trajectories. These enhanced elliptical extreme ultraviolet and soft x-ray radiations may serve as essential tools for exploring the ultrafast dynamics in magnetic materials and chiral media. 相似文献
2.
CuPc molecules adsorbed on Au(1 1 0)-(1 × 2): growth morphology and evolution of valence band states
Fabrizio Evangelista A. RuoccoValdis Corradini M.P. DonzelloCarlo Mariani Maria Grazia Betti 《Surface science》2003,531(2):123-130
We present the growth morphology, the long-range ordering, and the evolution of the valence band electronic states of ultrathin films of copper phthalocyanine (CuPc) deposited on the Au(1 1 0)-(1 × 2) reconstructed surface, as a function of the organic molecule coverage. The low energy electron diffraction patterns present a (5 × 3) reconstruction from the early adsorption stages. High-resolution UV photoelectron spectroscopy data show the disappearance of the Au surface states related to the (1 × 2) reconstruction, and the presence of new electronic features related to the molecule-substrate interaction and to the CuPc molecular states. The CuPc highest occupied molecular orbital gradually emerges in the valence band, while the interface electronic states are quenched, upon increasing the coverage. 相似文献
3.
超软X射线流气式正比计数管 总被引:2,自引:0,他引:2
介绍了一种用于测量183~933eV超软X射线的圆柱形、侧窗式、流气式正比计数管,工作气体是0.11MPa的P-10气体或氦气-丙烷混合气体。计数管内径为φ25mm,直径为φ0.3mm的入射窗是由厚度80~90μgcm~2聚乙烯甲醛制成的。该计数管的特点:(1)薄窗,对软X射线透过率高。(2)流气式,工作寿命长。(3)能量分辨率好。(4)计数率高(1×10~(14)个/s)。(5)可测能区宽(0.183~10keV)。(6)可以方便更换窗膜材料、厚度及窗口直径。近几年来该计数管已经为高强度低能X光源提供较好监测。 相似文献
4.
M. K. Richharia 《Pramana》2007,68(6):1007-1012
The cosmic ray (CR) intensity data recorded in Deep River Neutron Monitoring Station have been investigated on quietest days
(QD) for third harmonics of daily variation during solar cycles 21 and 22. It has been observed that in spite of abrupt change
in the amplitude and phase of tri-diurnal anisotropy in CR intensity, the amplitude is quite significant throughout the period
of investigation with larger amplitude during the years 1980 and 1985. Thus, tri-diurnal anisotropy clearly shows 11-year
variation at the mid latitude neutron monitoring station.
相似文献
5.
Gamma ray bursts (GRBs) have been proposed as one possible class of sources of the ultrahigh energy cosmic ray (UHECR) events
observed up to energies ≳ 1020 eV. The synchrotron radiation of the highest energy protons accelerated within the GRB source should produce gamma rays up
to TeV energies. Here we briefly discuss the implications on the energetics of the GRB from the point of view of the detectability
of the prompt TeV γ-rays of proton-synchrotron origin in GRBs in the up-coming ICECUBE muon detector in the south pole. 相似文献
6.
Summary The hints to explain the unusual type of cosmic cluster events (called generally the ?exotic? events) in ultrahigh-energy
nuclear collisions in terms of proposed H particles have, to date, been neither substantiated nor concretised. We assort here
some crucial aspects and assemble a few supportive evidences to favour our idea that the proposed H particles might be viewed
as cosmic psionlike particles. 相似文献
7.
In this paper, we discuss the detailed optical design of a beam line that is under construction on the synchrotron radiation source, Indus-1. Toroidal mirrors are used as pre-and post- focusing elements and a toroidal grating monochromator as a dispersing element. Using three interchangeable gratings, this monochromator will give, at a moderate resolution, a good throughput on the sample in the wavelength range 40 to 1000 Å. Effect of various parameters and their optimization on the resolution and throughput characteristics have been studied by ray tracing calculations, and presented. 相似文献
8.
Eu^2+:BaFCl光激励发光过程中紫外线的激发与漂白效应 总被引:1,自引:1,他引:0
通过改变紫外线的辐射照能量范围,研究了Eu^2+:BaFCl的光激励发光性质。发现紫外线能量大于Eu^2+的最低激发态能量及紫外线的能量小于Eu^2+最低激发态的能量两种情况下,光激励发光具有明显的差异,分析了产生差异的原因,给出了紫外线的辐照能量发生转时所对应的能级位置。 相似文献
9.
10.