全文获取类型
收费全文 | 154篇 |
免费 | 20篇 |
国内免费 | 20篇 |
专业分类
化学 | 3篇 |
晶体学 | 1篇 |
力学 | 6篇 |
综合类 | 13篇 |
数学 | 104篇 |
物理学 | 67篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 5篇 |
2016年 | 13篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 12篇 |
2012年 | 27篇 |
2011年 | 13篇 |
2010年 | 10篇 |
2009年 | 7篇 |
2008年 | 20篇 |
2007年 | 8篇 |
2006年 | 10篇 |
2005年 | 12篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
排序方式: 共有194条查询结果,搜索用时 15 毫秒
141.
YANG Wei-Hong 《理论物理通讯》2001,35(2):219-222
The simplified forms of generalized
magnetohydrodynamic equations have been derived. The K. Appert theory and Hain-Lüst equation are two special cases of our results when p→0 and
ω/ωci→0. It is shown
that the process of taking any limits (p→0 or ω/ωci→0) will result in a singularity at the Alfvén resonant layer. 相似文献
142.
40 Gb/s信号全光3R再生实验 总被引:1,自引:0,他引:1
提出一种新型40 Gb/s全光3R再生器方案。采用高精细度法布里-珀罗滤波器进行时钟提取。时钟提取前,通过高稳定光源对输入信号光波长变换实现信号光波长和法布里-珀罗滤波器梳状窗口对准;时钟提取后,接半导体光放大器(SOA)进一步消除时钟信号噪声。全光判决中,采用双半导体光放大器串联增大非线性性能,提高了判决门的响应速度。判决输出接窄带滤波器去除脉冲啁啾拖尾,减小码型效应。实验中,恶化40 Gb/s光脉冲信号通过全光3R再生器可以得到再生脉冲。输入恶化信号时间抖动大于5 ps,脉冲宽度大于16 ps,再生得到的信号时间抖动小于1.5 ps。再生信号相对于输入信噪比改善14 dB。连续稳定工作记录大于15 h。通过实验验证,这种全光3R再生器方案成功地实现了40 Gb/s信号的再生。 相似文献
143.
144.
本文研究Lienard型系统x=φ(h(y)-F(x)),y=-g(x)的全局稳定性问题.利用Filippov变换和一些新的方法建立了系统为全局稳定的系列充要条件. 相似文献
145.
Considering the effects of ion nonlinear polarization drift and
warm ions, we adopt two-fluid model to investigate the character of low-frequency Solitary Kinetic Alfvén Wave (SKAW hereafter) in a magnetic plasma. The results derived in this paper indicate that dip SKAW and hump SKAW both exist in a wide range in
magnetosphere (for the pressure parameter β~10-5~0.01, where β is the ratio of thermal pressure to magnetic pressure, i.e.
β=2μ0nT/B02). These two kinds of SKAWs propagate at either Super-Alfvénic velocity or
Sub-Alfvénic velocity. In the inertial region β<<me/mi, the Sub-Alfvénic velocity dip SKAWs and hump SKAWs both exist; in the transmittal region β~ 2me/mi, dip SKAWs and hump SKAWs propagate at Super-Alfvénic velocity or Sub-Alfvénic velocity; Super-Alfvénic velocity hump SKAWs
and Super-Alfvénic and Sub-Alfvénic velocity dip SKAWs are in the kinetic region 1>>β>> me/mi. These results are different from previous ones. That indicates that the effects of
ion nonlinear polarization drift and warm ions are important and
they cannot be neglected. The SKAW has an electric field parallel
to the ambient magnetic field, which makes the SKAW take an important role in the acceleration and energization of
field-aligned charged particles in magnetic plasmas. And the SKAW
is also important for the heating of a local plasma. So it makes a
novel physical mechanism of energy transmission possible. 相似文献
146.
本文给出Fréchet空间中集值映射的锥拉伸与锥压缩不动点定理。同时也讨论Banach空间与Hilbert空间中集值映射的相应不动点定理。并导出逼近定理作为应用。 相似文献
147.
提出了点集Bézier曲线的概念,给出了点集Bézier曲线的性质及细分算法.按照点集算术的定义,当点集是长方形闭域或圆盘时,点集Bézier曲线就是区间Bézier曲线或圆盘Bézier曲线,因此,点集Bézier曲线是对区间Bézier曲线和圆盘Bézier曲线的推广. 相似文献
148.
Kinetic Alfvén Wave (KAW) is one of the low-frequency electromagnetic
fluctuations that are identified extensively in space plasmas
by in situ observations of satellites and has been an interesting
topic for discussion widely in the fields of laboratory, space,
and astrophysical plasmas because of its potential importance in plasma particle energization. Some satellite observations show that the number density ratio of the oxygen ions
to the ambient plasma is 30%~50%,
sometimes, even as high as 80%. In this paper, effects of heavy ion species on KAWs are studied in a low-beta plasma.
The results show that heavy ions not only considerably reduce the propagation speed of KAWs, but also remarkably influence the parallel component of perturbed electric field of KAWs (to the ambient magnetic field). The ratio of parallel
to perpendicular components of perturbed field decreases
(or increases) with the heavy ion abundance for KAWs dominated by
the electron inertial length (or by ion acoustic gyroradius).
In particular, the resonant condition of KAWs with thermal electrons
is modified by the heavy ion species. 相似文献
149.
依据光学法布里珀罗(F-P)腔基本原理,分析了非本征敏感法布里珀罗腔光纤液位传感器工作原理及设计方案。实验结果表明,传感器具有良好的多周期输出特性和局部的线性特性,但法布里珀罗腔输出光强幅度随腔长增大逐渐衰减,传感器输出特性曲线中不同部分相同长度的线性工作区间却对应不同的测量量程和灵敏度。改变传感头中敏感组件的尺寸可满足对不同液位测量的需要。本传感器最大量程为20 m,精度为±0.5 mm,最小分辨力为0.3 mm。传感器特别适用于对易燃易爆液位精确测量,具有很强的实用性。 相似文献
150.
For the nonpositive Hermite-Fejér interpolation based on the Laguerre abscissas, a pointwise two-sided estimate of the degree of approximation in the aleatoric interval [0, A] is first established. 相似文献