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51.
The effect of a high temperature AlN buffer layer grown by the initially alternating supply of ammonia (IASA) method on AlGaN/GaN heterostructures was studied. The use of AlN by the IASA method can effectively increase the crystalline quality and surface morphology of GaN. The mobility and concentration of 2DEG of AlGaN/GaN heterostuctures was also ameliorated. 相似文献
52.
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
53.
Nonpolar (1120) a-plane GaN films have been grown by low-pressure metal-organic vapor deposition on r-plane (1102) sapphire substrate. The structural and electrical properties of the a-plane GaN films are investigated by high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and van der Pauw Hall measurement. It is found that the Hall voltage shows more anisotropy than that of the c-plane samples; furthermore, the mobility changes with the degree of the van der Pauw square diagonal to the c direction, which shows significant electrical anisotropy. Further research indicates that electron mobility is strongly influenced by edge dislocations. 相似文献
54.
Nonpolar a-plane [110] GaN has been grown on r-plane [1■02] sapphire by MOCVD, and investigated by high resolution X-ray diffraction and atomic force microscopy. As opposed to the c-direction, this particular orientation is non-polar, and it avoids polarization charge, the associated screening charge and the consequent band bending. Both low-temperature GaN buffer and high-temperature AlN buffer are used for a-plane GaN growth on r-plane sapphire, and the triangular pits and pleat morphology come forth with different buffers, the possible reasons for which are discussed. The triangular and pleat direction are also investigated. A novel modulate buffer is used for a-plane GaN growth on r-plane sapphire, and with this technique, the crystal quality has been greatly improved. 相似文献
55.
采用1.25Mev 60Co γ射线辐射源对钝化前后的AlGaN/GaN HEMT器件进行了1Mrad(Si)的总剂量辐射,实验发现:1Mrad总剂量辐射后未钝化器件的饱和漏电流和最大跨导分别下降了15%和9.1%,而且正向和反向栅电流明显增加,但是阈值电压几乎没有发生变化。相反的,同样的累积剂量下,钝化器件的饱和漏电流和最大跨导却基本没变。通过对钝化前后器件的不同辐射反应以及C-V测试的分析表明,栅-源和栅-漏间隔区辐射感生表面态负电荷的产生是低剂量下AlGaN/GaN HEMT器件电特性退化的主要原因,同时也说明钝化可以有效地抑制60Co γ辐射感生表面态电荷,它是一种有效的加固手段。 相似文献
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现有成品率及关键面积估计模型中。假定缺陷轮廓为圆。而70%的实际缺陷轮廓接近于椭圆.提出了椭圆缺陷轮廓的成品率模型,该模型与圆模型相比更具有一般性.而圆模型轮廓的成品率模型仅为新模型的特例.比较了新模型与真实缺陷及其圆模型引起的成品率损失。表明新模型在成品率估计方面更加精确. 相似文献
59.
通过N2气氛中对蓝宝石衬底AlGaN/GaN HEMT在200~600℃退火1min和5min的多批实验,研究了在不同温度和时间退火冷却后器件直流参数的变化.对器件欧姆接触和肖特基接触在高温退火前后的特性进行了对比分析.确定出了最有利于高电子迁移率晶体管特性提高的退火温度为500℃.退火时间为5min.该条件退火后高电子迁移率晶体管最大跨导提高8.9%.肖特基栅反向漏电流减小2个数量级.阈值电压绝对值减小.退火后肖特基势垒高度提高.在减小栅泄漏电流的同时对沟道电子也有耗尽作用.这是饱和电流和阈值电压变化的主要原因.采用扫描电子显微镜观察肖特基退火后的形貌,500℃未发现明显变化.600℃有起泡现象. 相似文献
60.