全文获取类型
收费全文 | 1176篇 |
免费 | 47篇 |
国内免费 | 12篇 |
专业分类
化学 | 26篇 |
晶体学 | 4篇 |
力学 | 6篇 |
综合类 | 5篇 |
数学 | 16篇 |
物理学 | 69篇 |
无线电 | 1109篇 |
出版年
2024年 | 4篇 |
2023年 | 24篇 |
2022年 | 16篇 |
2021年 | 15篇 |
2020年 | 9篇 |
2019年 | 20篇 |
2018年 | 13篇 |
2017年 | 23篇 |
2016年 | 26篇 |
2015年 | 29篇 |
2014年 | 80篇 |
2013年 | 68篇 |
2012年 | 81篇 |
2011年 | 76篇 |
2010年 | 81篇 |
2009年 | 97篇 |
2008年 | 118篇 |
2007年 | 88篇 |
2006年 | 76篇 |
2005年 | 80篇 |
2004年 | 53篇 |
2003年 | 48篇 |
2002年 | 16篇 |
2001年 | 18篇 |
2000年 | 14篇 |
1999年 | 15篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
排序方式: 共有1235条查询结果,搜索用时 312 毫秒
111.
目前,世界上广泛应用的卫星数字广播的制式可大致分为两种:一种是欧洲广播联盟的数字视频广播方式,通常称为DVB-S方式;另一种是美国通用仪器公司开发的方式,称为DIGICIPHER方式。两种方式互不相容。它们之间的区别主要在于数字 相似文献
112.
当前,由于广大教师从互联网上可以轻易获得大量中考试题,课本习题往往闲置,特别是单元复习中的有关习题则更是“门前冷落鞍马稀”,大量习题俨然“英雄无用武之地”,一学期下来,课本基本不用,导致教学资源极大浪费,教学效率低下. 相似文献
113.
114.
以网络极限承载能力为突破口,对两种无线资源利用率算法进行浅析,研究在网络极限能力下的实际运行效率,并将两种算法联合分析,通过两种建模,给出判定高效小区的初步方法。 相似文献
115.
提出了一种基于动态优先权的LTE无线参数下发算法,该算法综合考虑多网共存网络优化的优先级要求以及异系统无线参数调整方案的相关性,通过预测指令下发时间,根据动态优先权和分组的应对复杂的无线指令调整需求。该方法可以提高网络优化的效率,降低优化工作对操作人员专业程度和优化经验的依赖性。 相似文献
116.
TD-SCDMA小区承载能力研究 总被引:1,自引:1,他引:0
TD-SCDMA小区承载能力是评估TD-SCDMA网络容量的基础,本文从上行、下行两个维度计算TDSCDMA小区承载能力,结合现网业务流量上下行配比,提出上行受限是目前影响TD-SCDMA网络容量的主要瓶颈。并通过分析造成上行受限的原因,提出增强TD-SCDMA小区上行承载能力的可选方案。 相似文献
117.
118.
Device-to-Device (D2D) com- munication has been proposed as a promising implementation of green communication to benefit the existed cellular network. In order to limit cross-tier interference while explore the gain of short-range communication, we devise a series of distributed power control (DPC) schemes for energy conservation (EC) and enhancement of radio resource utilization in the hybrid system. Firstly, a constrained opportunistic power control model is built up to take advantage of the interference avoidance methodology in the presence of service requirement and power constraint. Then, biasing scheme and admission control are added to evade ineffective power consumption and maintain the feasibility of the system. Upon feasibility, a non-cooperative game is further formulated to exploit the profit in EC with minor influence on spectral efficiency (SE). The convergence of the DPC schemes is validated and their performance is confirmed via simulation results. 相似文献
119.
M. Luglio C. Roseti F. Zampognaro 《中国通信》2014,(12):105-119
Cloud computing can significantly improve efficiency in Internet utilization and data management.Several cloud applications(file sharing,backup,data up/download etc.) imply transfers of large amount of data without real-time requirements.In several use-cases cloud-computing solutions reduce operational costs and guarantee target QoS.These solutions become critical when satellite systems are utilized,since resources are limited,network latency is huge and bandwidth costs are high.Using satellite capacity for cloud-computing bulk traffic,keeping acceptable performance of interactive applications,is very important and can limit the connectivity costs.This goal can be achieved installing in the Set Top Box(STB) a proxy agent,to differentiate traffic and assign bandwidth according to priority,leaving spare capacity to bulk cloud computing traffic.This aim is typically reached using a specific QoS architecture,adding functional blocks at network or lower layers.We propose to manage such a process at transport layer only.The endpoint proxy implements a new transport protocol called TCP Noordwijk+,introducing a flow control differentiation capability.The proxy includes TPCN+ which efficiently transfers low-priority bulk data and handles interactive data,keeping a high degree of friendliness.The outcomes of Ns-2simulations confirm applicability and good performance of the proposed solution. 相似文献
120.
Recently, content-centric networking (CCN) has become a hot research topic for the diffusion of contents over the Internet. Most existing works on CCN focus on the improvement of network resource utilization. Consequently, the energy consumption aspect of CCN is largely ignored. In this paper, we propose a distributed energyefficient in-network caching scheme for CCN, where each content router only needs locally available information to make caching decisions considering both caching energy consumption and transport energy consumption. We formulate the in-network caching problem as a non-cooperative game. Through rigorous mathematical analysis, we prove that pure strategy Nash equilibria exist in the proposed scheme, and it always has a strategy profile that implements the socially optimal configuration, even if the touters are self-interested in nature. Simulation results are presented to show that the distributed solution is competitive to the centralized scheme, and has superior performance compared to other popular caching schemes in CCN. Besides, it exhibits a fast convergence speed when the capacity of content routers varies. 相似文献