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31.
Time delay is an important parameter in the problem of internet congestion control. According to some researches, time delay is not always constant and can be viewed as a periodic function of time for some cases. In this work, an internet congestion control model is considered to study the time-varying delay induced bursting-like motion, which consists of a rapid oscillation burst and quiescent steady state. Then, for the system with periodic delay of small amplitude and low frequency, the method of multiple scales is employed to obtain the amplitude of the oscillation. Based on the expression of the asymptotic solution, it can be found that the relative length of the steady state increases with amplitude of the variation of time delay and decreases with frequency of the variation of time delay. Finally, an effective method to control the bursting-like motion is proposed by introducing a periodic gain parameter with appropriate amplitude. Theoretical results are in agreement with that from numerical method. 相似文献
32.
文章针对一种简单的拥塞控制模型,分析了拥塞控制的缓存性能,得到了精确的缓存空间B和阈值θ。指出拥塞控制运行机制缓存过大的原因,给出了合理的拥塞控制运行机制的缓存性能的分析。仿真结果验证了分析的正确性。 相似文献
33.
34.
Sunil Kumar Zhenhua Feng Fei Hu Yang Xiao 《Wireless Communications and Mobile Computing》2009,9(10):1301-1311
An event‐to‐sink reliable transport (ESRT) control scheme was recently proposed to address the event‐to‐sink reliability issues in wireless sensor network (WSN). In this paper, we study the performance of ESRT in the presence of ‘over‐demanding’ event reliability, using both the analytical and simulation approaches. We show that the ESRT protocol does not achieve optimum reliability and begins to fluctuate between two inefficient network states. With insights from update mechanism in ESRT, we propose a new algorithm, called enhanced ESRT (E2SRT), to solve the ‘over‐demanding’ event reliability problem and to stabilize the network. Simulation results show that E2SRT outperforms ESRT in terms of both reliability and energy consumption in the presence of ‘over‐demanding’ event reliability. Besides, it ensures robust convergence in the presence of dynamic network environments. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
35.
Golam Sarwar Roksana Boreli Emmanuel Lochin 《International Journal of Satellite Communications and Networking》2012,30(4):163-180
We present experimental results for the performance of selected voice codecs using Datagram Congestion Control Protocol (DCCP) with CCID4 congestion control over a satellite link. We evaluate the performance of both constant and variable data rate speech codecs for a number of simultaneous calls using the ITU E‐model. We analyse the sources of packet losses and additionally analyse the effect of jitter, which is one of the crucial parameters contributing to Voice over IP (VoIP) quality and has, to the best of our knowledge, not been considered previously in the published DCCP performance results. We propose modifications to the CCID4 algorithm and demonstrate how these improve the VoIP performance, without the need for additional link information other than what is already monitored by CCID4. We also demonstrate the fairness of the proposed modifications to other flows. Although the recently adopted changes to TCP‐Friendly Rate Control specification alleviate some of the performance issues for VoIP on satellite links, we argue that the characteristics of commercial satellite links necessitate consideration of further improvements. We identify the additional benefit of DCCP when used in VoIP admission control mechanisms and draw conclusions about the advantages and disadvantages of the proposed DCCP/CCID4 congestion control mechanism for use with VoIP applications. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
36.
Christian Lochert Bjrn Scheuermann Martin Mauve 《Wireless Communications and Mobile Computing》2007,7(5):655-676
Congestion control is a key problem in mobile ad hoc networks. The standard congestion control mechanism of the Transmission Control Protocol (TCP) is not able to handle the special properties of a shared wireless multi‐hop channel well. In particular, the frequent changes of the network topology and the shared nature of the wireless channel pose significant challenges. Many approaches have been proposed to overcome these difficulties. In this paper, we give an overview over existing proposals, explain their key ideas and show their interrelations. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
37.
This paper presents a distributed and adaptive fluctuation control scheme for many-to-one routing(FCM) in wireless sensor networks.Unlike well-known topology control schemes,the primary design objective is to reduce the fluctuation which happens due to overload of sensors in a data collection tree.More specifically,an estimation model of a sensor available capacity based on the number of its neighbors is proposed.In addition,this paper proposes a parent selection mechanism by three-way handshake.With such model and the selection mechanism,it is ensured that the load of a sensor does not exceed its available capacity.Finally,an adaptive maintenance mechanism is proposed to adjust the estimation of a sensor available capacity as the network environment changes.Simulation results demonstrate the effectiveness of the scheme. 相似文献
38.
The dynamics of information traffic over scale-free networks has been investigated systematically. A series of routing strategies
of data packets have been proposed, including the local routing strategy, the next-nearest-neighbour routing strategy, and
the mixed routing strategy based on local static and dynamic information. The capacity of the network can be quantified by
the phase transition from free flow state to congestion state. The optimal parameter values of each model leading to the highest
efficiency of scale-free networked traffic systems have been found. Moreover, we have found hysteretic loop in networked traffic
systems with finite packets delivering ability. Such hysteretic loop indicates the existence of the bi-stable state in the
traffic dynamics over scale-free networks.
相似文献
39.
We study the four-directional traffic flow on a two-dimensional lattice. In the case of discrete densities, we assume equal number of vehicles in each lane. Except for the minimum density, the gridlock emerges swiftly. Two kinds of gridlock have been observed. The global gridlock dominates the system when the density is twice the minimum value. At higher densities, the system is pervaded by local gridlocks. We also analyze the time evolution of average speed. In the case of continuous densities, the vehicle numbers vary from lane to lane. The global gridlock is then destroyed by the fluctuations; while the local gridlock can still be observed. 相似文献
40.