全文获取类型
收费全文 | 770984篇 |
免费 | 29592篇 |
国内免费 | 18773篇 |
专业分类
化学 | 394973篇 |
晶体学 | 10937篇 |
力学 | 42575篇 |
综合类 | 53篇 |
数学 | 108870篇 |
物理学 | 261941篇 |
出版年
2021年 | 7027篇 |
2020年 | 7783篇 |
2019年 | 9296篇 |
2018年 | 12109篇 |
2017年 | 12866篇 |
2016年 | 17237篇 |
2015年 | 10478篇 |
2014年 | 15987篇 |
2013年 | 35498篇 |
2012年 | 28212篇 |
2011年 | 33766篇 |
2010年 | 27405篇 |
2009年 | 27842篇 |
2008年 | 30472篇 |
2007年 | 29594篇 |
2006年 | 27114篇 |
2005年 | 24677篇 |
2004年 | 24180篇 |
2003年 | 21447篇 |
2002年 | 21253篇 |
2001年 | 22685篇 |
2000年 | 17435篇 |
1999年 | 14143篇 |
1998年 | 12204篇 |
1997年 | 11849篇 |
1996年 | 11503篇 |
1995年 | 10681篇 |
1994年 | 10866篇 |
1993年 | 10714篇 |
1992年 | 10859篇 |
1991年 | 11033篇 |
1990年 | 10411篇 |
1989年 | 10444篇 |
1988年 | 10050篇 |
1987年 | 9225篇 |
1986年 | 8907篇 |
1985年 | 11056篇 |
1984年 | 11565篇 |
1983年 | 9475篇 |
1982年 | 10043篇 |
1981年 | 9465篇 |
1980年 | 8932篇 |
1979年 | 9477篇 |
1978年 | 9903篇 |
1977年 | 9873篇 |
1976年 | 10006篇 |
1975年 | 9226篇 |
1974年 | 9015篇 |
1973年 | 9430篇 |
1972年 | 7137篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
991.
992.
We use the adiabatic hyperspheric expansion and the Faddeev decomposition of the wave function with only s-waves. We derive for a fixed hyperradius an integro-differential equation for the angular eigenvalue and wave function. The
correlations lower the interaction energy for N = 20 by about a factor of 5.
Received October 22, 2001; accepted for publication November 5, 2001 相似文献
993.
Yu. A. Pobedin 《JETP Letters》2002,75(12):625-630
The states of a charged particle with a finite free path are determined in the field of a resonant electromagnetic wave. The exact resonance conditions, the modulation and beam instability mechanisms, the charge and current densities (Ohm's law) are obtained for the collisionless beam of resonance particles. Quantum theory of radiation is developed for the resonant adiabatic interaction between a particle and a wave taking into account the interaction with a constant magnetic field induced at the grating surface by the charge and nonresonant waves. The radiation power, the spectrum, and the range of generated frequencies are determined. The results obtained can be used in the plasma and solid-state theories and in electronics. 相似文献
994.
A. M. Zheltikov 《Optics and Spectroscopy》2002,93(2):286-290
A harmonic oscillator model is used to demonstrate the possibility of coherent control of acoustic vibrations of metal nanoparticles and thin films with sequences of femtosecond laser pulses. When the interval between the pulses in such a sequence is chosen equal to the oscillation period of the expansion mode of a nanoscale system, the relevant acoustic vibrations can be excited in a resonant and selective way. Sequences of femtosecond pulses with picosecond time intervals between the pulses are shown to be ideally suited for a resonant excitation and coherent control of acoustic modes of silver nanoparticles. 相似文献
995.
996.
本文采用椭圆偏振光谱法研究了剂量为1×1016—3×1012cm-2的As+注入硅,及其在700℃退火后的光学性质。得出:当As+注入剂量增大到某一程度后,便呈非晶特性。低于临界剂量的样品,其n-λ,ε2-λ关系曲线随剂量的增大而往下方移动,呈有规律变化;退火后,在大于4000?波段,n-λ与ε2-λ曲线基本恢复到单晶硅状态。但在小于4000?的紫外区却未完全恢复,注入剂量越大,偏离单晶硅就越大。并指出,紫外光区是离子注入硅的信息敏感区;用有效质量模型计算出注入剂量与损伤度的关系。计算结果与实验符合得较好。
关键词: 相似文献
997.
V. Bena Jothy T. Vijayakumar D. Sajan V. S. Jayakumar I. Hubert Joe 《Laser Physics》2006,16(8):1242-1252
Single crystals of sarcosinium oxalate monohydrate (SOM) are grown by the slow-evaporation technique at ambient temperature, and vibrational spectroscopic analysis is carried out using NIR-FT Raman, FT-IR, and SERS spectra. The normal mode frequencies and corresponding vibrational analysis of SOM are examined theoretically using the Gaussian’98 set of quantum chemical codes. The two bands present in the SOM ν C=O region, clearly observed in the Raman spectrum, are assigned to “free” and “bonded” carbonyl groups with the hydrogen atom. Vibrational analysis indicates the presence of C-H—O hydrogen bonding interaction producing a blueshift of the C-H stretching frequency. 相似文献
998.
999.
1000.
An implicit quasi-monotone second-order accurate method is proposed for analyzing the spiral Couette flow of a rarefied gas between coaxial cylinders. The basic advantages of the method over the conventional method of stationry iterations are that the former is conservative with respect to the collision integral, has a simple software implementation for any types of boundary conditions, and applies to a wide range of Knudsen numbers. 相似文献