全文获取类型
收费全文 | 873篇 |
免费 | 161篇 |
国内免费 | 108篇 |
专业分类
电工技术 | 20篇 |
综合类 | 154篇 |
化学工业 | 1篇 |
金属工艺 | 1篇 |
机械仪表 | 10篇 |
建筑科学 | 38篇 |
矿业工程 | 5篇 |
能源动力 | 1篇 |
水利工程 | 8篇 |
石油天然气 | 1篇 |
无线电 | 311篇 |
一般工业技术 | 41篇 |
冶金工业 | 80篇 |
原子能技术 | 1篇 |
自动化技术 | 470篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 17篇 |
2021年 | 22篇 |
2020年 | 29篇 |
2019年 | 21篇 |
2018年 | 25篇 |
2017年 | 28篇 |
2016年 | 35篇 |
2015年 | 54篇 |
2014年 | 57篇 |
2013年 | 56篇 |
2012年 | 71篇 |
2011年 | 77篇 |
2010年 | 88篇 |
2009年 | 68篇 |
2008年 | 99篇 |
2007年 | 80篇 |
2006年 | 55篇 |
2005年 | 67篇 |
2004年 | 45篇 |
2003年 | 26篇 |
2002年 | 35篇 |
2001年 | 23篇 |
2000年 | 17篇 |
1999年 | 8篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有1142条查询结果,搜索用时 140 毫秒
11.
文章研究了感知无线电网络中联合频谱分配和调度的问题,给出了基于物理干扰模型的频谱分配算法。调度算法是对由频谱分配算法得到的一系列传输模式进行调度,从而实现频谱共享。本文基于提出的频谱分配算法通过仿真比较了三种调度算法,结果表明考虑了公平性的调度算法的网络吞吐量有稍微的降低(可达到最大吞吐量的96%),但感知用户的整体需求满足度却得到了很大的提高,即达到了很好的公平性。 相似文献
12.
13.
Jin Ye Jian‐Xin Wang Jia‐Wei Huang 《International Journal of Communication Systems》2011,24(12):1611-1626
The fair allocation of resources among different nodes is one of the critical problems in wireless mesh networks. Existing solutions mainly focus on rate‐limitation policies or distributed fair MAC schemes at the potential expense of total network utilization. This paper investigates a special starvation problem among TCP flows that are different hops away from the BS, as well as its recently proposed solution, the ‘Minimum Content Window’ policy based on IEEE 802.11e. It is found that the aggregate throughput degrades sharply because the effect of this policy on the TCP congestion mechanism has been overlooked. This paper proposes a priority‐based congestion control by using ‘Cross‐Layer Explicit Congestion Notification’. Analysis and simulation results demonstrate that our scheme can improve the fairness of TCP flows while the aggregate throughput is at least 20% higher than the ‘Minimum Content Window’ policy. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
14.
为使含有家庭基站和宏基站的异构网络(HetNet)中各用户的服务质量需求都能满足并达到用户间的公平性,在功率限制条件下对宏用户中最小的用户数据速率最大化,将此最小用户速率提供给家庭基站用户,获得各家庭基站用户的目标信干噪比(SINR),再利用对分法调整家庭基站的发射功率.仿真结果表明,该方法能够保证最小的宏用户数据速率且提高异构网络用户间的公平性. 相似文献
15.
中继系统下的众多资源分配策略很少同时考虑多用户情形下的子载波配对和不同用户需求。针对这一问题,提出了一种基于QoS(服务质量)保证和比例公平的多用户子载波配对和功率分配算法,该算法既能保证QoS用户的最小速率要求,又能满足BE(尽力而为)用户之间速率比例公平的准则。该算法首先根据不同用户需求分配第二跳的子载波,然后利用匈牙利配对算法得到两跳子载波的最佳配对,最后用类似注水算法进行功率分配。仿真结果表明,所提算法在满足用户QoS保证和比例公平准则的同时有效提升了系统的吞吐量。 相似文献
16.
17.
Genuine moral disagreement exists and is widespread. To understand such disagreement, we must examine the basic kinds of social relationships people construct across cultures and the distinct moral obligations and prohibitions these relationships entail. We extend relational models theory (Fiske, 1991) to identify 4 fundamental and distinct moral motives. Unity is the motive to care for and support the integrity of in-groups by avoiding or eliminating threats of contamination and providing aid and protection based on need or empathic compassion. Hierarchy is the motive to respect rank in social groups where superiors are entitled to deference and respect but must also lead, guide, direct, and protect subordinates. Equality is the motive for balanced, in-kind reciprocity, equal treatment, equal say, and equal opportunity. Proportionality is the motive for rewards and punishments to be proportionate to merit, benefits to be calibrated to contributions, and judgments to be based on a utilitarian calculus of costs and benefits. The 4 moral motives are universal, but cultures, ideologies, and individuals differ in where they activate these motives and how they implement them. Unlike existing theories (Haidt, 2007; Hauser, 2006; Turiel, 1983), relationship regulation theory predicts that any action, including violence, unequal treatment, and “impure” acts, may be perceived as morally correct depending on the moral motive employed and how the relevant social relationship is construed. This approach facilitates clearer understanding of moral perspectives we disagree with and provides a template for how to influence moral motives and practices in the world. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
18.
Natalia Vassileva Yevgeni Koucheryavy 《Wireless Communications and Mobile Computing》2015,15(4):666-684
The adaptive modulation and coding (AMC) technique, which has been adopted by advanced mobile telecommunication systems, supports a flexible response to the random radio behaviour. As a result, the attained transmission rate over a wireless link is time varying. Hence, resource demands are not deterministic but fluctuating even for calls with constant bit rate service requirements. Consequently, constant bit rate calls are susceptible to a forced call termination because of insufficient resources not only in a target cell during inter‐cell handoffs but also in a serving cell during radio link deterioration. Furthermore, call blocking and dropping probabilities depend on radio propagation conditions among other factors and therefore they are dissimilar throughout a service area. The latter leads to unfairness problems. We analytically measure the impact of AMC on fixed‐rate service with hard delay constraints such as voice for different signal, mobility and traffic conditions. We consider a reference case (call requests are admitted into the system provided there are enough free resources) and two classes of admission control approaches: traditional (only inter‐cell handoffs are prioritised) and modified (all ongoing calls are prioritised). The reported results reveal conditions for which AMC affects voice call performance and can serve as guidelines on admission control design. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
19.
De Cremer David; Brockner Joel; Fishman Ariel; van Dijke Marius; van Olffen Woody; Mayer David M. 《Canadian Metallurgical Quarterly》2010,95(2):291
Prior research has shown that procedural fairness interacts with outcome fairness to influence employees’ work attitudes (e.g., organizational commitment) and behaviors (e.g., job performance, organizational citizenship behavior), such that employees’ tendencies to respond more positively to higher procedural fairness are stronger when outcome fairness is relatively low. In the present studies, we posited that people’s uncertainty about their standing as organizational members would have a moderating influence on this interactive relationship between procedural fairness and outcome fairness, in that the interactive relationship was expected to be more pronounced when uncertainty was high. Using different operationalizations of uncertainty of standing (i.e., length of tenure as a proxy, along with self-reports and coworkers’ reports), we found support for this hypothesis in 4 field studies spanning 3 different countries. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
20.
Building on fairness heuristic theory, fairness theory, and trust development models, we argue that unfairly enacted procedures decrease followers' trust in the authority particularly when authorities have high power over their followers. Moreover, we expected trust to mediate procedural fairness effects on followers' attitudes (authorities' legitimacy and charisma attributed to authorities) and organizational citizenship behavior. Procedural fairness effects on these variables, as mediated by trust, should therefore also be stronger when authority power is high. The results of a single- and multisource field study and a laboratory experiment supported these predictions. These studies support the role of authority power as a theoretically and practically relevant moderator of procedural fairness effects and show that its effectiveness is explained through trust in authorities. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献