全文获取类型
收费全文 | 4437篇 |
免费 | 160篇 |
国内免费 | 21篇 |
专业分类
化学 | 3389篇 |
晶体学 | 49篇 |
力学 | 40篇 |
数学 | 231篇 |
物理学 | 909篇 |
出版年
2023年 | 30篇 |
2021年 | 43篇 |
2020年 | 55篇 |
2019年 | 81篇 |
2018年 | 48篇 |
2017年 | 45篇 |
2016年 | 97篇 |
2015年 | 106篇 |
2014年 | 100篇 |
2013年 | 220篇 |
2012年 | 243篇 |
2011年 | 284篇 |
2010年 | 169篇 |
2009年 | 156篇 |
2008年 | 280篇 |
2007年 | 262篇 |
2006年 | 217篇 |
2005年 | 241篇 |
2004年 | 240篇 |
2003年 | 189篇 |
2002年 | 203篇 |
2001年 | 97篇 |
2000年 | 87篇 |
1999年 | 54篇 |
1998年 | 53篇 |
1997年 | 36篇 |
1996年 | 46篇 |
1995年 | 37篇 |
1994年 | 40篇 |
1993年 | 44篇 |
1992年 | 44篇 |
1991年 | 46篇 |
1990年 | 41篇 |
1989年 | 42篇 |
1988年 | 37篇 |
1987年 | 34篇 |
1986年 | 41篇 |
1985年 | 69篇 |
1984年 | 59篇 |
1983年 | 34篇 |
1982年 | 36篇 |
1981年 | 40篇 |
1980年 | 29篇 |
1979年 | 43篇 |
1978年 | 37篇 |
1977年 | 17篇 |
1976年 | 30篇 |
1975年 | 24篇 |
1974年 | 16篇 |
1973年 | 16篇 |
排序方式: 共有4618条查询结果,搜索用时 15 毫秒
11.
A. Noda S. Nakamura Y. Iwashita S. Sakabe M. Hashida T. Shirai S. Shimizu H. Tongu H. Ito H. Souda A. Yamazaki M. Tanabe H. Daido M. Mori M. Kado A. Sagisaka K. Ogura M. Nishiuchi S. Orimo Y. Hayashi A. Yogo S. Bulanov T. Esirkepov A. Nagashima T. Kimura T. Tajima T. Takeuchi K. Matsukado A. Fukumi Z. Li 《Laser Physics》2006,16(4):647-653
In order to widely spread out particle beams utilized in cancer therapy, laser-produced ions are developed as the injection beam for an ion synchrotron dedicated for cancer therapy. Such a laser ion source is expected to contribute largely to the realization of compactness of the size and low cost of the cancer therapy accelerator. The energy spectrum of the laser-produced ions, however, has no peak, but their intensities decrease exponentially according to the increase of the energy. For the purpose of modifying such a situation, we have proposed a scheme to rotate the beam in the longitudinal phase space with the use of the RF electric field, which is phase-adjusted with the pulse laser. We aim for a reduction of the energy spread of ± 5% selected by an energy analyzer and slits to ±1% by such phase rotation. For this purpose, a quarter wavelength resonator with two gaps with the same resonant frequency as the source laser has already been fabricated, together with its RF power source. The above phase rotation system and its recent experimental realization are presented. 相似文献
12.
Adsorption process of methylchloride (CH3Cl) on the GaAs (0 0 1)-2 × 4 surface was studied by a scanning tunnelling microscopy (STM) measurement. The arsenic rich 2 × 4 surface, which was prepared by molecular beam epitaxy (MBE), was exposed to a supersonic molecular beam of CH3Cl with a kinetic energy of 0.06 eV. New bright spots appeared on the CH3Cl exposed surface. They were largely observed at the “B-type” step edge and divided into two types according to their locations. It was suggested that new spots were due to weakly adsorbed CH3Cl molecules without any dissociation. The adsorption mechanism of CH3Cl molecule was also studied by an ab initio Hartree-Fock calculation, which explained the experimental results well. 相似文献
13.
It is shown that if in a simple graph G of order n the sum of degrees of any three pairwise non-adjacent vertices is at least n, then there are two cycles (or one cycle and an edge or a vertex) of GF that contain all the vertices. © 1995 John Wiley & Sons, Inc. 相似文献
14.
15.
We calculate s-wave and p-wave absorptive pion-nucleus optical potentials assuming that a pion is absorbed by a pair of nucleons. Employing a model which takes into account both a single nucleon absorption with nucleon-nucleon correlations and rescattering, we obtain simple analytic expressions for Im B0 sid Im C0 of the pion-nucleus optical potential. The off-shell effect on the s-wave pion absorption is examined and shown to be strongly modified by short range correlations. The result for the p-wave absorptive part Im C0 clearly shows the importance of the tensor correlations. The enhanced nn emission after π? absorption is shown to be related with a large p-wave πN scattering length a33 via the tensor correlations. 相似文献
16.
Y. Masuda K. Asahi J. Kura Y. Mori H. Sato H. M. Shimizu 《Hyperfine Interactions》1992,74(1-4):149-157
An experimental scheme of the spin detailed balance in polarized neutron transmission through a polarized nuclear target is
discussed for the T-violation test. The value of the spin detailed balance is estimated by using the data of the scattering
amplitudes. The nuclear polarizations of proton,3He and139La are discussed for the T-violation experiment. 相似文献
17.
The behavior of zirconium atoms at the W(100) surface associated with oxygen adsorption at different sample temperatures has been studied by Auger electron spectroscopy (AES), ion scattering spectroscopy (ISS), and the relative change of the work function (Δф) measured by the onset of the secondary electron energy distribution. The results have revealed: (i) adsorption of zirconium onto the W(100) surface followed by the elevation of the sample temperature up to 1710 K in an oxygen partial pressure of 2.7 × 10−4 induces complete diffusion of zirconium atoms into the W(100) substrate; (ii) further exposure of oxygen induces co-existence of oxygen and tungsten on the surface at 1710 K, resulting in a work function of 4.37 eV; (iii) keeping the sample temperature at 1710 K, simple evacuation of the system has resulted in surface segregation of zirconium atoms to the surface to form a zirconium atomic layer on the top-most surface, reducing the work function to 2.7 eV. The results have revealed that this specific behavior of zirconium atoms at high temperature assures, with very good reproducibility, the highly stable performance and long service life of Zr---O/W(100)-emitters in practical use, even in a low vacuum of 10−6 Pa. 相似文献
18.
19.
20.
Various N-sulfenyl heterocycles were synthesized by transamination of sulfenamides using a chlorine gas-free method. The N-sulfenyl heterocycles behaved as sulfenylating reagents of anilines; N-sulfenylbenzimidazoles were the most effective. 相似文献