全文获取类型
收费全文 | 132篇 |
免费 | 24篇 |
国内免费 | 5篇 |
专业分类
化学 | 34篇 |
力学 | 29篇 |
综合类 | 4篇 |
数学 | 5篇 |
物理学 | 7篇 |
无线电 | 82篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 18篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 6篇 |
2016年 | 7篇 |
2015年 | 11篇 |
2014年 | 12篇 |
2013年 | 8篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 12篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 3篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 1篇 |
2001年 | 3篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
排序方式: 共有161条查询结果,搜索用时 0 毫秒
21.
22.
Shamanth Nagaraju Sreejith V Lucy J. Gudino Bhushan V. Kadam Ramesha C. K. Joseph Rodrigues 《International Journal of Communication Systems》2020,33(4)
In common practice, sensor nodes are randomly deployed in wireless sensor network (WSN); hence, location information of sensor node is crucial in WSN applications. Localization of sensor nodes performed using a fast area exploration mechanism facilitates precise location‐based sensing and communication. In the proposed localization scheme, the mobile anchor (MA) nodes integrated with localization and directional antenna modules are employed to assist in localizing the static nodes. The use of directional antennas evades trilateration or multilateration techniques for localizing static nodes thereby resulting in lower communication and computational overhead. To facilitate faster area coverage, in this paper, we propose a hybrid of max‐gain and cost‐utility–based frontier (HMF) area exploration method for MA node's mobility. The simulations for the proposed HMF area exploration–based localization scheme are carried out in the Cooja simulator. The paper also proposes additional enhancements to the Cooja simulator to provide directional and sectored antenna support. This additional support allows the user with the flexibility to feed radiation pattern of any antenna obtained either from simulated data of the antenna design simulator, ie, high frequency structure simulator (HFSS) or measured data of the vector network analyzer (VNA). The simulation results show that the proposed localization scheme exhibits minimal delay, energy consumption, and communication overhead compared with other area exploration–based localization schemes. The proof of concept for the proposed localization scheme is implemented using Berkeley motes and customized MA nodes mounted with indigenously designed radio frequency (RF) switch feed network and sectored antenna. 相似文献
23.
With location-based services worldwide used,private location data appealed easily in query process which caused serious security problems.So the introduction of SpaceTwist incremental nearest neighbor query algorithm,proposes protection of privacy method combined with improved SpaceTwist location optimization algorithm.The anchor point authentication server added to distributed system structure,user generate a k anonymous area according to their privacy preference and actual environment,using optimization algorithm to generate the anchor point.Forwarding users use the incremental nearest neighbor query throught the anchor point and accurate.Experiments in road network environment with different data sets show that the privacy protection works well in the algorithm,and own high work efficiency. 相似文献
24.
Paul A. Rejto Djamal Bouzida Gennady M. Verkhivker 《Theoretical chemistry accounts》1999,101(1-3):138-142
Binding-energy landscapes are used to investigate the thermodynamics of molecular recognition for the pteridine ring, a recognition
anchor in binding with dihydrofolate reductase, and two molecules with the same shape but different heteroatom substitutions.
The relative importance of hydrogen bonding and hydrophobic interactions in this system is analyzed by comparing these three
different decorations of the pteridine scaffold.
Received: 5 May 1998 / Accepted: 3 September 1998 / Published online: 17 December 1998 相似文献
25.
26.
This paper deals with the problem of sensor node localization in the presence of uncertainty in anchor node location. Aqueous environments are prone to adverse effects of underwater currents. This adversity causes non‐negligible mobility to the anchor nodes deployed under water. Localization in the presence of uncertainty in the anchor node location is quite challenging. Also, the authors consider the ray‐bending property of underwater medium due to depth dependent sound speed, to furnish the accurate position estimate of the target node. Standard ray equations are used to model the path followed by acoustic rays in water. Maximum likelihood estimation is proposed to estimate the location of target node with uncertainty in anchor node positions and is compared with the scheme with exact knowledge of anchor node positions, and the results are reported. Monte Carlo simulation is used to assess the performance of the proposed method. Also, the Cramer‐Rao lower bound with uncertainty in anchor nodes is derived and described. Simulation results of the proposed algorithm outperform the existing algorithm with known anchor location by up to 49.4%, and hence, accuracy is improved in the proposed method. 相似文献
27.
28.
为使随机部署的三维无线传感器网络中锚节点的分布更加合理,提高未知节点定位精度,针对锚节点部署进行优化。通过构建弹簧系统模型,将锚节点抽象为通过弹簧相连接的点,使部分锚节点在合力作用下进行伸缩运动,达到提高网络性能的目的。当锚节点部署优化完成后,应用近似三角形内点测试( APIT)和DV-HOP( Distance Vector-hop)算法测试优化前后的节点定位精度。仿真结果表明,三维空间下的锚节点经过弹簧系统模型的部署优化后,锚节点网络覆盖率和定位覆盖率均得到了提高,网络平均连通度有所提升,且定位精度显著提高。 相似文献
29.
在当前5G非独立组网(NSA)及4/5G异厂家组网条件下,5G NSA用户出现无法快速驻留5G网络的情况,同时,5G手机图标显示与5G体验速率的关键也取决于此。为提升5G用户感知,本文旨在研究NSA网络场景下,利用锚点移频及SPID功能,实现4G/5G用户的有效解耦以及5G用户的稳定驻留。 相似文献
30.
航天器海上测量船是搭载着船载测控系统的海上平台,主要完成对目标的海上测控任务。测量船在新建之时或大修之后均要对搭载的测控系统进行标校,主要是进行海上合作目标校飞。海上校飞过程中锚泊状态下天线对塔相位标校必不可少,对此进行研究有助于提高锚泊状态下对塔相位标校过程的认识,提升船载测控系统的标校精度。研究过程首先分析了我国测量船所采用的差模双通道单脉冲雷达的跟踪原理和天线对塔校相原理,然后再结合锚泊状态下大型海上测量船的运动规律,建立了船体运动对锚泊状态下对塔校相精度影响的数学模型,最后在远场条件下对数学模型进行了的仿真,分析了测量船锚泊时不同运动模式对相位标校的影响,并进一步给出了锚泊状态下船载测控天线对塔校相的建议。 相似文献