全文获取类型
收费全文 | 143篇 |
免费 | 16篇 |
国内免费 | 6篇 |
专业分类
化学 | 4篇 |
力学 | 5篇 |
综合类 | 1篇 |
数学 | 6篇 |
物理学 | 8篇 |
无线电 | 141篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 10篇 |
2012年 | 7篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 7篇 |
2008年 | 13篇 |
2007年 | 16篇 |
2006年 | 12篇 |
2005年 | 14篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
排序方式: 共有165条查询结果,搜索用时 15 毫秒
41.
当前的Intemet体系结构和其中许多协议无法很好的适用存在高延迟和频繁割裂的网络.当端节点具有严格的能量和存储限制时,这一问题将更加恶化.由于移动性和特殊应用需求,使得像陆地移动网络、军事无线自组织网络、星际网络及无线传感器网络等这样的受限网络缺乏“保持连接”的基础结构.这些受限网络有它们自己的专有协议而不采用TCP/IP协议.为了实现这些网络之间的互联,国际上提出了在端到端连接和节点资源都受限时的一种新型网络体系结构和应用接口,称为延迟容忍网络(简称容迟网络,DIN,Delay-Tolerant Networks).DTN作为网络互联时传输层上的覆盖网可用来满足随意的异步消息可靠转发.本文研究分析了容迟网络的应用背景、体系结构、关键技术和一些开放问题,并给出了未来的发展方向和应用前景. 相似文献
42.
A physical model for simulating overlay metrology employing diffraction based overlay (DBO) principles is built. It can help to optimize the metrology wavelength selection in DBO. Simulation result of DBO metrology with a model based on the finite-difference time-domain (FDTD) method is presented. A common case (bottom mark asymmetry) in which error signals are always induced in DBO measurement due to the process imperfection were discussed. The overlay sensitivity of the DBO measurement across the visible illumination spectrum has been performed and compared. After adjusting the model parameters compatible with the actual measurement conditions, the metrology wavelengths which provide the accuracy and robustness of DBO measurement can be optimized. 相似文献
43.
For thick resist implant layers, such as a high voltage P well and a deep N well, systematic and uncorrectable overlay residues brought about by the tapered resist profiles were found. It was found that the tapered profile is closely related to the pattern density. Potential solutions of the manufacturing problem include hardening the film solidness or balancing the exposure density. In this paper, instead of focusing on the process change methodology,we intend to solve the issue of the overlay metrology error from the perspective of the overlay mark design. Based on the comparison of the overlay performances between the proposed overlay mark and the original design, it is shown that the optimized overlay mark target achieves better performance in terms of profiles, dynamic precision,tool induced shift (TIS), and residues. Furthermore, five types of overlay marks with dummy bars are studied, and a recommendation for the overlay marks is given. 相似文献
44.
45.
将对等覆盖网技术引入到应用层路由方案中,利用寻找中继结点的方法,在应用层选取合适的结点对语音数据包进行中继转发,充分利用了网络上结点的差异性和多样性,形成延迟约束的中继转发策略.在NS2网络模拟器中对动态路标机制方案进行了模拟,得到保持在70%以上的中继结点命中率,证实了算法的可行性. 相似文献
46.
Yunchong Guan Weimin Lei Wei Zhang Hao Li Songyang Zhang 《International Journal of Communication Systems》2019,32(5)
Multipath transmission (MT) promotes transmission quality effectively. Path diversity (PD) impacts MT quality by aggregating capabilities of paths with little correlation. Enough PD contributes to improving concurrent link utilization and weakening negative impacts from a single path so that abilities of congestion and failure tolerance are enhanced. However, PD is hard to guarantee on overlay networks due to little awareness of underlay networks and few evaluation methods. In this paper, we propose the spatial geometry–based multipath routing (SGMR) method to improve PD for MT on overlay networks. Considering that paths are composed of overlay nodes and network coordinates effectively characterize node diversity (ND), we employ some geometric mechanisms on the spatial coordinate–based view to convert ND to PD. Firstly, coordinates are generated to match the overlay and underlay networks and meanwhile to characterize ND. Then, for generating multiple paths, transmission direction facilitates the path convergence, transmission surface constrains intermediate nodes, and deviation angle guarantees link diversity. Simulation and real‐world evaluations demonstrate that SGMR guarantees PD better, and the multipath transmission quality is improved thanks to enough PD. 相似文献
47.
In this paper, we investigate the physical layer security of a hybrid cognitive relay network using an energy harvesting relay in presence of an eavesdropper. In the hybrid scheme, a secondary user (SU) as well as a cognitive relay works either in underlay or in overlay mode. In underlay, the transmit power of the SU as well as the relay is limited by the maximum acceptable interference at primary user (PU) receiver as required by an outage constraint of PU, a quality of service for PU. The secondary network consists of a decode and forward relay that harvests energy from radio frequency signal of secondary transmitter as well as PU transmitter to assist the SU in forwarding the information signal to the destination. A time switching relaying protocol is used at the relay. We evaluate the secrecy outage probability of secondary relay network assuming that channel state information of the interfering links from both the SU and relay transmitter to PU receiver is imperfect. Our results reveal the impact of imperfect channel state information, energy harvesting time, tolerable interference threshold, and PU outage constraint on the secrecy outage probability of SU. 相似文献
48.
就 S1 2 40维护过程中的计费文件丢失情况 ,通过分析其相关原理及数据结构 ,总结出尽可能恢复计费记录的一套方法。 相似文献
49.
50.
基于镜像焦面检测对准标记的套刻性能原位测量技术 总被引:7,自引:2,他引:5
套刻性能是现代高精度步进扫描投影光刻机的重要性能指标之一。提出了一种基于镜像焦面检测对准标记(简称“镜像焦面检测对准标记”)的光刻机套刻性能原位测量技术。该技术通过对曝光在硅片上的镜像焦面检测对准标记图形进行光学对准,利用标记图形对准位置与理想位置偏差实现套刻性能的原位检测。实验结果表明该技术在进行套刻误差的精确测量的同时还可以全面、定量地计算影响光刻机单机套刻误差的场内参量及场间参量。与目前套刻性能原位测量技术相比,该技术有效地避免了测量精度对轴向像质限制的依赖,简化了光刻机整机性能检测的过程。 相似文献