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91.
This paper investigates subset antenna transmission (SAT) for multiple-input multiple-output (MIMO) systems in the presence
of strong dominant co-channel interferer. The capacity gain from SAT is investigated in the context of optimal antenna subset
selection and power allocation. The SAT does not require channel state information of the co-channel interference, and achieves
capacity gains by distributing the transmit power equally over a selected subset of the transmit antennas. The capacity gain
of the SAT method is analyzed in terms of transmit power and eigenvalues of channel matrix, and its performance in V-BLAST
MIMO systems with various signal constellations is evaluated by computer simulation. 相似文献
92.
Jae-Hoon Kim 《Wireless Personal Communications》2007,41(4):527-538
We address the problem of dynamically allocating radio resource to various call types over the single CDMA common trunk. Based
on the estimation of queue waiting time (QWT) of non-realtime (NRT) calls, we decide the appropriate allocation method to
each call between Time Divisional (TD) and Code Divisional (CD) type resource allocation. We perform queuing analysis to derive
closed-form expressions for QWT, which enables the delay-guarantee of access control scheme easy to solve in realtime (RT)
fashion. This quickness and simplicity of the proposed method to any traffic environment well manifests its potential to real-world
implementations. Computational experience also reveals its effectiveness in utilizing resource over the static radio resource
allocation schemes, implemented in the presently operative 3G CDMA systems. 相似文献
93.
Design of an enhanced access point to optimize TCP performance in Wi-Fi hotspot networks 总被引:1,自引:0,他引:1
In the last years, the number of Wi-Fi hotspots at public venues has undergone a substantial growth, promoting the WLAN technologies
as the ubiquitous solution to provide high-speed wireless connectivity in public areas. However, the adoption of a random
access CSMA-based paradigm for the 802.11 MAC protocol makes difficult to ensure high throughput and a fair allocation of
radio resources in 802.11-based WLANs. In this paper we evaluate extensively via simulations the interaction between the flow
control mechanisms implemented at the TCP layer and the contention avoidance techniques used at the 802.11 MAC layer. We conducted
our study considering initially M wireless stations performing downloads from the Internet. From our results, we observed that the TCP downlink throughput
is not limited by the collision events, but by the inability of the MAC protocol to assign a higher chance of accessing the
channel to the base station. We propose a simple and easy to implement modification of the base station’s behavior with the
purpose of increasing the TCP throughput reducing useless MAC protocol overheads. With our scheme, the base station is allowed
to transmit periodically bursts of data frames towards the mobile hosts. We design a resource allocation protocol aimed at
maximizing the success probability of the uplink transmissions by dynamically adapting the burst length to the collision probability
estimated by the base station. By its design, our scheme is also beneficial to achieve a fairer allocation of the channel
bandwidth among the downlink and uplink flows, and among TCP and UDP flows. Simulation results confirm both the improvement
in the TCP downlink throughput and the reduction of system unfairness. 相似文献
94.
G. Malescio 《Physica A》2007,383(2):643-650
We present a model describing a generic process in which a finite resource is partitioned and distributed among agents. Through numerical simulation we show that the model considered is able to originate, within a unifying approach, a variety of broad distributions and provides an interpretation of empirical properties of distributions observed in the real world. In particular it allows to relate the exponent of the power-law part of the distributions to resource abundance and accessibility, while the left-end exponential behavior, observed in many distributions, is related to the presence of dissipative effects. 相似文献
95.
Dimitris Katsianis Dimitris Varoutas Vassiliki Apostolopoulou 《International Journal of Satellite Communications and Networking》2007,25(3):237-250
This paper presents the technoeconomic aspects of network solutions based on integration of satellite and terrestrial, based on ADSL, WLAN and DVB‐T technologies, architectures. Following a discussion of the general deployment context, the business case framework is described in terms of areas served, services offered, tariffs, demand assumptions, as well as network architecture and dimensioning rules. The key cost items are presented and economic estimations are provided in the case of telecom operators, which integrate satellite bandwidth with terrestrial technologies in different area types. The evaluated business cases have shown that the satellite rental cost (airtime cost) level is one of the most critical parameter for the economic indicator of present value. Therefore, agreements with satellite operators for spectrum usage will give operators space for business opportunities and acceptable profit margins. In addition, dynamic bandwidth allocation schemes can exploit the aggregated traffic within satellite transmission, which can benefit satellite, telecom and cable operators offering entertainment on broadband business as well as new entrants in broadband business, equipment vendors, broadcasters and TV companies. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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本文研究了在发送端已知信道均值或协方差信息情况下单用户多输入多输出(MIMO)系统的功率分配问题.发送端已知信道均值信息时,信道建模为非相关莱斯信道;发送端已知协方差信息时,信道建模为相关瑞利信道.通过最大化遍历(ergodic)信道容量的一个较紧的下界,针对发送端已知信道均值或协方差信息的情况分别提出了新的功率分配的方案.仿真结果验证了该功率分配方法的有效性。 相似文献