全文获取类型
收费全文 | 4194篇 |
免费 | 119篇 |
国内免费 | 19篇 |
专业分类
化学 | 2660篇 |
晶体学 | 20篇 |
力学 | 142篇 |
数学 | 754篇 |
物理学 | 756篇 |
出版年
2023年 | 28篇 |
2022年 | 23篇 |
2021年 | 80篇 |
2020年 | 80篇 |
2019年 | 83篇 |
2018年 | 72篇 |
2017年 | 48篇 |
2016年 | 114篇 |
2015年 | 98篇 |
2014年 | 111篇 |
2013年 | 172篇 |
2012年 | 216篇 |
2011年 | 312篇 |
2010年 | 179篇 |
2009年 | 178篇 |
2008年 | 226篇 |
2007年 | 223篇 |
2006年 | 225篇 |
2005年 | 175篇 |
2004年 | 154篇 |
2003年 | 135篇 |
2002年 | 140篇 |
2001年 | 59篇 |
2000年 | 45篇 |
1999年 | 41篇 |
1998年 | 28篇 |
1997年 | 39篇 |
1996年 | 65篇 |
1995年 | 38篇 |
1994年 | 52篇 |
1993年 | 38篇 |
1992年 | 37篇 |
1991年 | 32篇 |
1990年 | 28篇 |
1989年 | 24篇 |
1988年 | 28篇 |
1987年 | 22篇 |
1986年 | 26篇 |
1985年 | 53篇 |
1984年 | 56篇 |
1983年 | 39篇 |
1982年 | 36篇 |
1981年 | 38篇 |
1980年 | 44篇 |
1979年 | 50篇 |
1978年 | 26篇 |
1977年 | 21篇 |
1976年 | 24篇 |
1974年 | 22篇 |
1970年 | 15篇 |
排序方式: 共有4332条查询结果,搜索用时 15 毫秒
21.
22.
B. Blank J. -J. Gaimard H. Geissel K. -H. Schmidt H. Stelzer K. Sümmerer D. Bazin R. Del Moral J. P. Dufour A. Fleury F. Hubert H. -G. Clerc M. Steiner 《Zeitschrift für Physik A Hadrons and Nuclei》1992,343(4):375-379
Total charge-changing cross sections have been measured for8Li on C and Pb targets, for9Li on C, Al, Cu, Sn and Pb targets, as well as for11Li on C, Sn and Pb targets at about 80 MeV/nucleon. These data are compared to measured total reaction cross sections and Glauber-type calculations using Hartree-Fock density distributions. These comparisons allow to draw conclusions on the proton density distribution of the neutronrich lithium isotopes. The results show that even for the most exotic nucleus11Li the proton distribution is only very weakly influenced by the long tail in the neutron density distribution already established in several experiments. 相似文献
23.
Bruno Crosignani 《Fiber and Integrated Optics》1992,11(3):235-252
The basic differential equations necessary to represent nonlinear propagation of short and ultrashort optical pulses in dielectric waveguides are derived. After introducing fundamental and higher-order soliton solutions of the nonlinear Schroedinger equations, the possibilities of realizing soliton-based communication systems are discussed. Higher-order nonlinear effects associated with selj-Raman gain and optical amplification in connection with the use of active fibers are also described. 相似文献
24.
Herlin-Boime N. Vicens J. Dufour C. Ténégal F. Reynaud C. Rizk R. 《Journal of nanoparticle research》2004,6(1):63-70
Small SiC nanoparticles (10 nm diameter) have been grown in a flow reactor by CO2 laser pyrolysis from a C2H2 and SiH4 mixture. The laser radiation is strongly absorbed by SiH4 vibration. The energy is transferred to the reactive medium and leads to the dissociation of molecules and the subsequent growth of the nanoparticles. The reaction happens with a flame. The purpose of the experiments reported in this paper is to limit the size of the growing particles to the nanometric scale for which specific properties are expected to appear. Therefore the effects of experimental parameters on the structure and chemical composition of nanoparticles have been investigated. For a given reactive mixture and gas velocity, the flame temperature is governed by the laser power. In this study, the temperature was varied from 875°C to 1100°C. The chemical analysis of the products indicate that their composition is a function of the temperature. For the same C/Si atomic ratio in the gaseous phase, the C/Si ratio in the powder increases from 0.7 at 875°C up to 1.02 at 1100°C, indicating a growth mechanism limited by C2H2 dissociation. As expected, X-ray diffraction has shown an improved crystallisation with increasing temperature. Transmission electron microscopy observations have revealed the formation of 10 nm grains for all values of laser power (or flame temperature). These grains appear amorphous at low temperature, whereas they contain an increasing number of nanocrystals (2 nm diameter) when the temperature increases. These results pave the way to a better control of the structure and chemical composition of laser synthesised SiC nanoparticles in the 10 nm range. 相似文献
25.
The performances of two Laser Doppler Velocimetry (LDV) systems adapted for measuring the acoustic particle velocities are assessed in enclosed sound field. This assessment is performed by comparing the acoustic velocities measured by means of LDV to reference acoustic velocities estimated from sound pressure measurements. The two LDV systems are based on a single optical bench which delivers an optical signal called Doppler signal. The Doppler signal, which is frequency modulated, is analyzed by means of two signal processing systems, the BSA (Burst Spectrum Analyser from Dantec) on the one hand, and a system specifically developed for the estimation of the acoustic velocity on the other hand. Once the experimental setup has been optimized for minimizing the errors made on the reference velocities, the assessment is performed and shows that both systems can measure the acoustic velocity in enclosed field in two the frequency ranges [0-4 kHz] and [0-2 kHz] respectively for acoustic velocity amplitudes of 10 mm/s and 1 mm/s. 相似文献
26.
27.
28.
Bassan Bruno Gossner Olivier Scarsini Marco Zamir Shmuel 《International Journal of Game Theory》2003,32(1):17-31
We exhibit a general class of interactive decision situations in which all the agents benefit from more information. This class includes as a special case the classical comparison of statistical experiments à la Blackwell.
AMS 2000 Subject Classification:Primary 91A35.The work of Bruno Bassan and Marco Scarsini was partially supported by MIUR-COFIN. The authors express their thanks to Sylvain Sorin for enlightening comments. 相似文献
29.
30.