全文获取类型
收费全文 | 319篇 |
免费 | 33篇 |
国内免费 | 209篇 |
专业分类
电工技术 | 9篇 |
综合类 | 12篇 |
化学工业 | 7篇 |
金属工艺 | 2篇 |
能源动力 | 1篇 |
武器工业 | 1篇 |
无线电 | 474篇 |
一般工业技术 | 40篇 |
冶金工业 | 1篇 |
原子能技术 | 1篇 |
自动化技术 | 13篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 12篇 |
2016年 | 24篇 |
2015年 | 21篇 |
2014年 | 19篇 |
2013年 | 20篇 |
2012年 | 31篇 |
2011年 | 52篇 |
2010年 | 37篇 |
2009年 | 53篇 |
2008年 | 44篇 |
2007年 | 46篇 |
2006年 | 49篇 |
2005年 | 37篇 |
2004年 | 26篇 |
2003年 | 13篇 |
2002年 | 7篇 |
2001年 | 13篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1985年 | 1篇 |
排序方式: 共有561条查询结果,搜索用时 0 毫秒
61.
A p-i-i-n type AlGaN heterostructure avalanche photodiodes (APDs) is proposed to decrease the avalanche breakdown voltage and to realize higher gain by using high-Al-content AlGaN layer as multiplication layer and low-Al-content AlGaN layer as absorption layer. The calculated results show that the designed APD can significantly reduce the breakdown voltage by almost 30%, and about sevenfold increase of maximum gain compared to the conventional AlGaN APD. The noise in designed APD is also less than that in conventional APD due to its low dark current at the breakdown voltage point. Moreover, the one-dimensional (1D) dual-periodic photonic crystal (PC) with anti-reflection coating filter is designed to achieve the solar-blind characteristic and cutoff wavelength of 282 nm is obtained. 相似文献
62.
63.
DUAN BaoXing & YANG YinTang 《中国科学:信息科学(英文版)》2012,(2):473-479
This paper demonstrates that the depletion process for AlGaN/GaN high electron mobility tran-sistors(HEMTs)is different than that for silicon power devices by analyzing active region depletion.Based on the special breakdown principle that occurs in AlGaN/GaN HEMTs,we propose a new reduced surface field AlGaN/GaN HEMT with a double low-density drain(LDD)and a positively charged region near the drain to optimize the surface electric field and increase the breakdown voltage.In this structure,two negative charge regions with different doses are introduced into the polarization AlGaN layer to form a double LDD and decrease the high electric field near the gate by depleting two-dimensional electron gas.A positively charged region is added to the electrode near the drain to decrease the high electric field peak at the drain edge.By applying ISE(integrated systems engineering)simulation software,we verify that the virtual gate effect occurs in the AlGaN/GaN HEMTs.The breakdown voltage is improved from 257 V in the conventional structure to 550 V in the proposed structure. 相似文献
64.
65.
66.
W. S. Tan P. A. Houston G. Hill R. J. Airey P. J. Parbook 《Journal of Electronic Materials》2004,33(5):400-407
The influence of dielectric stress on the direct current (DC) electrical characteristics of AlGaN/GaN heterostructure field-effect
transistors (HFETs) has been investigated. Dual-frequency plasma deposition was used to vary the amount of stress induced
by a passivating dielectric on the surface of the devices. Initial data suggested a strong influence from the induced dielectric
stress, but the low-frequency, radio-frequency (RF) excitation of the plasma deposition process was found to induce a severe
nonreversible damage to the exposed AlGaN surface through N ion bombardment. The consequence is a drastic reduction of the
sheet carrier concentration and mobility of the two-dimensional electron gas (2DEG). Subsequently, an alternative damage-free
technique using a helium precursor was used to obtain compressive films. Based on the results, uniform dielectric stress has
a minimal impact on the polarization charges within the AlGaN barrier. 相似文献
67.
T. J. Anderson F. Ren L. Covert J. Lin S. J. Pearton T. W. Dalrymple C. Bozada R. C. Fitch N. Moser R. G. Bedford M. Schimpf 《Journal of Electronic Materials》2006,35(4):675-679
By using a frequency-tripled Nd:YVO4 laser source (355 nm) for drilling through-wafer via holes in SiC substrates, we can reduce the surface contamination and
achieve better smoothness inside the via holes compared to use of the more common 1064-nm Nd:YVO4 laser. The sheet and contact resistance of AlGaN/GaN HEMT layers grown on SiC substrates were similar after formation of
vias by 355-nm laser drilling to those of the undrilled reference sample. By sharp contrast, 1064-nm laser drilling produces
significant redeposition of ablated material around the via and degrades the electrical properties of the HEMT layers. 相似文献
68.
69.
M. Ahoujja W. C. Mitchel S. Elhamri R. S. Newrock D. B. Mast J. M. Redwing M. A. Tischler J. S. Flynn 《Journal of Electronic Materials》1998,27(4):210-214
We have experimentally determined the effective mass (m*) of GaN, the classical (τ
c), and quantum (τ
q) scattering times for a two-dimensional electron gas residing at the interface of an AlGaN/GaN heterostructure, using the
Shubnikovde Haas effect. The ratio of the two scattering times, τ
c/τ
q, suggests that, at low temperatures, the scattering mechanism limiting the mobility is due to remote ionized impurities located
in AlGaN. This study should provide sample growers with information useful for improving the quality of the nitride heterostuctures. 相似文献
70.
Unpassivated/passivated AlGaN/GaN high electron mobility transistors (HEMTs) were exposed to 1.25 MeV 60Co γ-rays at a dose of 1 Mrad(Si). The saturation drain current of the unpassivated devices decreased by 15% at 1 Mrad γ-dose, and the maximal transconductance decreased by 9.1% under the same condition; more- over, either forward or reverse gate bias current was significantly increased, while the threshold voltage is relatively unaffected. By sharp contrast, the passivated devices showed scarcely any change in saturation drain current and maximal transconductance at the same γ dose. Based on the differences between the passivated HEMTs and un- passivated HEMTs, adding the C–V measurement results, the obviously parameter degradation of the unpassivated AlGaN/GaN HEMTs is believed to be caused by the creation of electronegative surface state charges in sourcegate spacer and gate–drain spacer at the low dose (1 Mrad). These results reveal that the passivation is effective in reducing the effects of surface state charges induced by the 60Co γ-rays irradiation, so the passivation is an effective reinforced approach. 相似文献