全文获取类型
收费全文 | 507篇 |
免费 | 28篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 8篇 |
综合类 | 9篇 |
化学工业 | 7篇 |
金属工艺 | 7篇 |
机械仪表 | 13篇 |
建筑科学 | 2篇 |
能源动力 | 2篇 |
石油天然气 | 3篇 |
武器工业 | 2篇 |
无线电 | 209篇 |
一般工业技术 | 23篇 |
原子能技术 | 2篇 |
自动化技术 | 263篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 10篇 |
2017年 | 20篇 |
2016年 | 12篇 |
2015年 | 17篇 |
2014年 | 24篇 |
2013年 | 21篇 |
2012年 | 19篇 |
2011年 | 23篇 |
2010年 | 25篇 |
2009年 | 28篇 |
2008年 | 43篇 |
2007年 | 39篇 |
2006年 | 48篇 |
2005年 | 38篇 |
2004年 | 23篇 |
2003年 | 33篇 |
2002年 | 16篇 |
2001年 | 10篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 15篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有550条查询结果,搜索用时 15 毫秒
1.
无源光网络(Passive Optical Network,PON)作为当今接入网的主要技术解决方案,具有带宽使用效率高、传输距离远、抗干扰能力强等特点.通过研究PON技术的发展动态,本文首先归纳了各种PON技术的产生背景和应用特点,整理出各技术间的连接关系及主要标准;其次介绍了PON技术的帧结构,并对带宽、波长、传输模式等PON技术的主要参数进行了汇总;然后将国内外研究热点进行划分,围绕媒体访问控制协议、帧结构、动态带宽分配算法、节能机制等关键技术,阐述了其研究现状及在PON中的重要作用;最后对PON技术的发展趋势进行了展望. 相似文献
2.
This investigation proposes a fixed collision rate (FCR) back-off algorithm for wireless networks. The proposed scheme takes advantage of the central unit (CU) in a wireless network to broadcast a common back-off window size to all the users, significantly alleviating the unfairness of bandwidth utilization in conventional binary exponential back-off (BEB) algorithms. It is shown that, when maximum throughput is achieved, collision rate is almost a constant for any traffic load. In the operation of the FCR, the CU dynamically adjusts the back-off window size to keep the collision rate at a constant level for maximum throughput. Simulation results demonstrate that the unfairness of bandwidth utilization in the BEB is significantly lessened and the throughput can be maintained at e-1≈0.368 when the number of users approaches infinity. The capture effect even further improves system performance. 相似文献
3.
随着广播电视技术的不断发展 ,模拟信号传输向数字信号传输的转换已成为必然。介绍模数转换系统中放大器的性能、关键技术 ,并就放大器的选择作详细探讨。 相似文献
4.
This paper addresses the problem of bandwidth allocation under the weighted maximum rate constrained link sharing policy and proves a key theory in the condition of allocation termination. We propose several algorithms with various worst-case and average-case time complexities, and evaluate their computation elapse times. 相似文献
5.
王宇 《计算机光盘软件与应用》2011,(13)
通畅的网络是在一个网络的负载均衡的条件下建立的,他的存在可以说是给整个网络的性能优良打下了基础,他的建立使网络的透明化、高效化、廉价化进入了一个成熟阶段,这位网络的进一步升级提供了非常方便的服务途径,网络的带宽、吞吐量都和网络的数据处理水平都能得到优化,这样便建立了一个成熟、灵活和可靠的网络。 相似文献
6.
We define and study an optimization problem that is motivated by bandwidth allocation in radio networks. Because radio transmissions are subject to interference constraints in radio networks, physical space is a common resource that the nodes have to share in such a way, that concurrent transmissions do not interfere. The bandwidth allocation problem we study under these constraints is the following. Given bandwidth (traffic) demands between the nodes of the network, the objective is to schedule the radio transmissions in such a way that the traffic demands are satisfied. The problem is similar to a multicommodity flow problem, where the capacity constraints are replaced by the more complex notion of non-interfering transmissions. We provide a formal specification of the problem that we call round weighting . By modeling non-interfering radio transmissions as independent sets, we relate the complexity of round weighting to the complexity of various independent set problems (e.g. maximum weight independent set, vertex coloring, fractional coloring). From this relation, we deduce that in general, round weighting is hard to approximate within n1−ε (n being the size of the radio network). We also provide polynomial (exact or approximation) algorithms e.g. in the following two cases: (a) when the interference constraints are specific (for instance for a network whose vertices belong to the Euclidean space), or (b) when the traffic demands are directed towards a unique node in the network (also called gathering, analogous to single commodity flow). 相似文献
7.
This paper proposes a method to reduce the cost of a core-based group-shared multicast tree, where the cost is evaluated by the total bandwidth consumption of multicasting packets among all group members. Due to the broadcast nature of radio transmissions, we find that the challenge of determining minimum cost multicast tree can be approximated by finding the multicast tree with a minimum number of non-leaves (the minimum non-leaf multicast tree problem). However, we also find that the minimum non-leaf multicast tree problem is NP-complete. Thus, a method is proposed to dynamically reduce the number of non-leaves in an existing multicast tree. Experimental results show that our method reduces the cost of the multicast tree in both geometrically and randomly distributed network models and the random waypoint mobility model. 相似文献
8.
Ultra wideband (UWB) systems are considered as the key wireless infrastructure platforms for efficient short-range communications.
In particular, the UWB based mobile computing systems are envisioned to be attractive solutions to various ad hoc networking
applications. However, due to UWB’s unique physical characteristics, the traditional resource management schemes for ad hoc
networks cannot be applied to UWB based systems directly. In this paper, we consider the bandwidth scheduling problem in a
UWB based hierarchical wireless ad hoc network, which is typically used in an enterprise-scale mobile computing environment.
Based on the mathematical analysis and the computer simulations, it is demonstrated that our proposed scheduling scheme exhibits
close-to-optimal performance governed by the proportional fairness (PF) constraint. Moreover, a novel self-organized clustering
method is designed to improve the system throughput while meeting the PF constraint. Simulation results suggest that the proposed
clustering method is effective under various system configurations.
相似文献
Yu-Kwong KwokEmail: |
9.
This paper addresses the design of clamped circular piezoceramic composite unimorph and bimorph configurations, specifically the conflicting requirements of maximum volume displacement for a prescribed bandwidth. An optimization problem is formulated that implements analytical solutions for unimorph and bimorph configurations using laminated plate theory, including the use of oppositely polarized piezoceramic patches. A range of actuator geometric parameters are studied, and bounds for volume displacement and natural frequency of optimal designs are determined and presented via design curves. In the selected design space, Pareto optimization results for unimorph and bimorph configurations show that optimal volume displacement is related to the bandwidth by a universal power law such that the product of the square of the natural frequency and the displaced volume, a “gain-bandwidth” product, is a constant. Characteristic trends are also described that are independent of the actuator radius for the Pareto optimal piezoceramic patch thickness and radius versus normalized bandwidth. The results are relevant, for example, in the design of zero-net mass-flux or synthetic jet actuators used in flow control applications. 相似文献
10.
In the present and next generation wireless networks, cellular system remains the major method of telecommunication infrastructure. Since the characteristic of the resource constraint, call admission control is required to address the limited resource problem in wireless network. The call dropping probability and call blocking probability are the major performance metrics for quality of service (QoS) in wireless network. Many call admission control mechanisms have been proposed in the literature to decrease connection dropping probability for handoffs and new call blocking probability in cellular communications. In this paper, we proposed an adaptive call admission control and bandwidth reservation scheme using fuzzy logic control concept to reduce the forced termination probability of multimedia handoffs. Meanwhile, we adopt particle swarm optimization (PSO) technique to adjust the parameters of the membership functions in the proposed fuzzy logic systems. The simulation results show that the proposed scheme can achieve satisfactory performance when performance metrics are measured in terms of the forced termination probability for the handoffs, the call blocking probability for the new connections and bandwidth utilization. 相似文献