全文获取类型
收费全文 | 469篇 |
免费 | 101篇 |
国内免费 | 10篇 |
专业分类
化学 | 6篇 |
力学 | 2篇 |
综合类 | 5篇 |
数学 | 57篇 |
物理学 | 38篇 |
无线电 | 472篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 11篇 |
2019年 | 15篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 20篇 |
2015年 | 15篇 |
2014年 | 54篇 |
2013年 | 35篇 |
2012年 | 27篇 |
2011年 | 44篇 |
2010年 | 19篇 |
2009年 | 37篇 |
2008年 | 20篇 |
2007年 | 27篇 |
2006年 | 28篇 |
2005年 | 29篇 |
2004年 | 32篇 |
2003年 | 37篇 |
2002年 | 28篇 |
2001年 | 18篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 4篇 |
1995年 | 10篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
排序方式: 共有580条查询结果,搜索用时 31 毫秒
121.
A non-linear congestion network model is developed for the Hajj case. The Hajj is one of the World's largest mass movements, according to religious rituals. Every year about two and a half million people gather to perform religious rituals. The objective of the model is to minimize traffic congestion and overcrowding of holy sites. The constraints of the model are religious, spatial and time constraints. The model developed and applied for this case assisted in easing overcrowding and planning for expansions in routes and holy sites. The model is effective in providing quantitative background for general policy decision on the Hajj transportation. 相似文献
122.
We develop deterministic fluid approximations to describe the recovery from rare congestion events in a large multi-server
system in which customer holding times have a general distribution. There are two cases, depending on whether or not we exploit
the age distribution (the distribution of elapsed holding times of customers in service). If we do not exploit the age distribution,
then the rare congestion event is a large number of customers present. If we do exploit the age distribution, then the rare
event is an unusual age distribution, possibly accompanied by a large number of customers present. As an approximation, we
represent the large multi-server system as an M/G/∞ model. We prove that, under regularity conditions, the fluid approximations are asymptotically correct as the arrival rate
increases. The fluid approximations show the impact upon the recovery time of the holding-time distribution beyond its mean.
The recovery time may or not be affected by the holding-time distribution having a long tail, depending on the precise definition
of recovery. The fluid approximations can be used to analyze various overload control schemes, such as reducing the arrival
rate or interrupting services in progress. We also establish large deviations principles to show that the two kinds of rare
events have the same exponentially small order. We give numerical examples showing the effect of the holding-time distribution
and the age distribution, focusing especially on the consequences of long-tail distributions.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
123.
124.
125.
126.
The extensions, new developments and new interpretations for DEA covered in this paper include: (1) new measures of efficiency, (2) new models and (3) new ways of implementing established models with new results and interpretations presented that include treatments of congestion, returns-to-scale and mix and technical inefficiencies and measures of efficiency that can be used to reflect all pertinent properties. Previously used models, such as those used to identify allocative inefficiencies, are extended by means of assurance region approaches which are less demanding in their information requirements and underlying assumptions. New opportunities for research are identified in each section of this chapter. Sources of further developments and possible sources for further help are also suggested with references supplied to other papers that appear in this volume and which are summarily described in this introductory chapter. 相似文献
127.
Varun Kumar Sharma 《International Journal of Electronics》2019,106(1):48-68
The ‘load distribution’ proposition in mobile ad-hoc networks (MANETs) is accomplishing great stimulation. This is because of the phenomenal facets it possesses including advanced network resilience, reliability and performance. Though there are other leading network layer routing protocols, but they radically utilise single-path communication paradigm, which is why they fail in achieving efficient load distribution in a network. Via this paper, we propose an efficient cross-layer adaptive load distribution approach to capitalise network’s channel utilisation and to rapidly adapt to dynamic wireless channel characteristic changes. The proposed method modifies the load balanced congestion adaptive routing (LBCAR) protocol and is developed using dynamic load distribution technique, by pioneering (i) novel parameters, which report for the availability of route pertaining to minimum traffic load and better link lifetime and also adapt according to varying available network resources; (ii) an absolute dynamic method to lessen the redundant route oscillations which further reduces the routing instabilities. The simulation results demonstrate the usefulness of the proposed method and yields better results in comparison to LBCAR and standard instead of dynamic ource outing, it is dynamic source routing (DSR) protocol. 相似文献
128.
The communication mechanism of wireless sensor and actor network (WSAN) was studied.Firstly,a proactive location management mechanism based on the update messages sent by mobile actors to sensors and the actors’ scope limited by Voronoi diagram was proposed.Thus,sensors predicted the movement of actors using Kalman filtering of the previously received updates.Then,an optimal energy-aware forwarding rule based on geographical routing was presented for sensor-actor communication,and the delay of the data delivery process was controlled using the power control and the network congestion was dealed with by forcing multiple actors to share the traffic generated in the event area.Finally,based on the characteristics of multiple concurrent events,a model for actor-actor coordination was proposed to coordinate their movements in order to optimally accomplish the tasks.Performance simulation results show that the proposed cooperative communication mechanism for WSAN can effectively reduce end-to-end delays,energy consumption and percentage of packet drops. 相似文献
129.
减少长短信寻呼量研究 总被引:1,自引:0,他引:1
本文对手机在接收长短信的时候需要多次寻呼响应才能完成长短信接收的情况进行了深入的研究,提出了优化短信中心的MT流程的方案.该方案可以很好的解决长短信多次寻呼问题,能有效降低寻呼总量,既不影响用户感受,也不影响设备性能,是值得采用的低成本高回报优化方式. 相似文献
130.