全文获取类型
收费全文 | 218篇 |
免费 | 28篇 |
国内免费 | 21篇 |
专业分类
化学 | 121篇 |
晶体学 | 2篇 |
力学 | 10篇 |
数学 | 6篇 |
物理学 | 43篇 |
综合类 | 85篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 2篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 8篇 |
2017年 | 2篇 |
2016年 | 12篇 |
2015年 | 12篇 |
2014年 | 11篇 |
2013年 | 12篇 |
2012年 | 18篇 |
2011年 | 14篇 |
2010年 | 4篇 |
2009年 | 17篇 |
2008年 | 10篇 |
2007年 | 15篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 1篇 |
排序方式: 共有267条查询结果,搜索用时 15 毫秒
171.
Fuyong Xu Changping Shangguan 《International Journal of Infrared and Millimeter Waves》2002,23(11):1649-1658
A characteristic equation and impedance characteristic for the dominant mode of closed elliptic-groove guide have been analyzed and discussed by using the mode-matching method. The reference size of the closed elliptic-groove guide for the good impedance matching with rectangular guide in actual application is given. The obtained conclusions are of important significance in theoretical studies and actual applications of closed elliptic-groove guide for millimeter waves. 相似文献
172.
As a new approach the heterodyne frequency offset locking system which is applicable to a broad range of pulsed lasers is described. A 100 MHz wide-band and all-digital frequency discriminating technique is presented and an offset locking loop in which the frequency discriminator works accordingly is designed. The result of the experiment on offset locking between a CW CO2 laser and an electro-optically Q-switched CO2 laser with an optical pulse width 300 ns and its repetition rate 20 kHz showed that the beat frequency stability was kept within ±2 MHz. 相似文献
173.
174.
一种新的阶跃折射率光纤本征函数表达形式 总被引:4,自引:2,他引:2
为了阐明阶跃折射率光纤的模式特性,根据电磁波辐射的能量守恒定律和经过狄拉克函数奇异性修正的亥姆霍兹方程,通过数学推导和证明得出:柱面径向行波场的本征函数是经过狄拉克函数修正的整数阶汉克尔函数,阶跃折射率光纤模式场的本征函数是零、一阶贝塞尔函数经过狄拉克函数修正的零、一阶诺埃曼函数和虚参量汉克尔函数.该结论揭示了光纤芯层和包层模式场分别是径向驻波场和倏逝波场的本质,并基此推导出新的光纤模式特征方程,模式存在条件,模式数目和符合光纤实际的基模归一化截止频率的理论值. 相似文献
175.
The effect of phase-breaking process on the ac response of a coupled double quantum dot is studied in this paper based on the nonequilibrium Green function formalism. A general expression is derived for the ac current in the presence of electron--phonon interaction. The ac conductance is numerically computed and the results are compared with those in [Anatram M P and Datta S 1995 Phys. Rev. B 51 7632]. Our results reveal that the inter-dot electron tunnelling interplays with that between dots and electron reservoirs, and contributes prominently to the ac current when inter-dot tunnelling coupling is much larger than the tunnelling coupling between dots and electron reservoirs. In addition, the phase-breaking process is found to have a significant effect on the ac transport through the coupled double dot. 相似文献
176.
Correction of temperature influence on the wind retrieval from a mobile Rayleigh Doppler lidar
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zhao Ruo-Can Xia Hai-Yun Dou Xian-Kang Sun Dong-Song Han Yu-Li Shangguan Ming-Jia Guo Jie Shu Zhi-Feng 《中国物理 B》2015,24(2):24218-024218
A mobile Rayleigh Doppler lidar based on double-edge technique is implemented for simultaneously observing wind and temperature at heights of 15 km-60 km away from ground.Before the inversion of the Doppler shift due to wind,the Rayleigh response function should be calculated,which is a convolution of the laser spectrum,Rayleigh backscattering function,and the transmission function of the Fabry-Perot interferometer used as the frequency discriminator in the lidar.An analysis of the influence of the temperature on the accuracy of the Une-of-sight winds shows that real-time temperature profiles are needed because the bandwidth of the Rayleigh backscattering function is temperature-dependent.An integration method is employed in the inversion of the temperature,where the convergence of this method and the high signal-to-noise ratio below 60 km ensure the accuracy and precision of the temperature profiles inverted.Then,real-time and on-site temperature profiles are applied to correct the wind instead of using temperature profiles from a numerical prediction system or atmosphere model.The corrected wind profiles show satisfactory agreement with the wind profiles acquired from radiosondes,proving the reliability of the method. 相似文献
177.
Comparative research on “high currents” induced by single event latch-up and transient-induced latch-up 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
By using the pulsed laser single event effect facility and electro-static discharge(ESD) test system, the characteristics of the "high current", relation with external stimulus and relevance to impacted modes of single event latch-up(SEL)and transient-induced latch-up(TLU) are studied, respectively, for a 12-bit complementary metal–oxide semiconductor(CMOS) analog-to-digital converter. Furthermore, the sameness and difference in physical mechanism between "high current" induced by SEL and that by TLU are disclosed in this paper. The results show that the minority carrier diffusion in the PNPN structure of the CMOS device which initiates the active parasitic NPN and PNP transistors is the common reason for the "high current" induced by SEL and for that by TLU. However, for SEL, the minority carrier diffusion is induced by the ionizing radiation, and an underdamped sinusoidal voltage on the supply node(the ground node) is the cause of the minority carrier diffusion for TLU. 相似文献
178.
179.
折算频率对翼型动态升力特性影响的初步研究 总被引:2,自引:0,他引:2
本文根据在西北工业大学翼型研究中心(CADR)进行的NACA0012翼型动态特性研究,着重介绍测力法研究中,滤波器截止频率和动态特性研究中最重要的相似准则折算频率影响的研究结果.结果表明,对动态特性研究而言,恰当的滤波器截止频率是获得正确结果的必要条件,在此基础上,通过改变折算频率,得出它对升力特性影响的可信结果. 相似文献
180.