全文获取类型
收费全文 | 2546篇 |
免费 | 487篇 |
国内免费 | 450篇 |
专业分类
电工技术 | 76篇 |
综合类 | 380篇 |
化学工业 | 18篇 |
金属工艺 | 8篇 |
机械仪表 | 53篇 |
建筑科学 | 154篇 |
矿业工程 | 21篇 |
能源动力 | 7篇 |
轻工业 | 73篇 |
水利工程 | 20篇 |
石油天然气 | 9篇 |
武器工业 | 9篇 |
无线电 | 424篇 |
一般工业技术 | 229篇 |
冶金工业 | 282篇 |
原子能技术 | 3篇 |
自动化技术 | 1717篇 |
出版年
2023年 | 40篇 |
2022年 | 63篇 |
2021年 | 82篇 |
2020年 | 96篇 |
2019年 | 106篇 |
2018年 | 84篇 |
2017年 | 100篇 |
2016年 | 120篇 |
2015年 | 124篇 |
2014年 | 221篇 |
2013年 | 234篇 |
2012年 | 296篇 |
2011年 | 292篇 |
2010年 | 285篇 |
2009年 | 259篇 |
2008年 | 240篇 |
2007年 | 248篇 |
2006年 | 161篇 |
2005年 | 121篇 |
2004年 | 69篇 |
2003年 | 72篇 |
2002年 | 46篇 |
2001年 | 33篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1983年 | 3篇 |
1978年 | 1篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1964年 | 4篇 |
1963年 | 2篇 |
1962年 | 2篇 |
1961年 | 1篇 |
1960年 | 2篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1956年 | 4篇 |
1954年 | 1篇 |
排序方式: 共有3483条查询结果,搜索用时 33 毫秒
51.
《Behaviour & Information Technology》2012,31(2):115-126
Three studies were conducted to ascertain how quickly people form an opinion about web page visual appeal. In the first study, participants twice rated the visual appeal of web homepages presented for 500 ms each. The second study replicated the first, but participants also rated each web page on seven specific design dimensions. Visual appeal was found to be closely related to most of these. Study 3 again replicated the 500 ms condition as well as adding a 50 ms condition using the same stimuli to determine whether the first impression may be interpreted as a 'mere exposure effect' (Zajonc 1980). Throughout, visual appeal ratings were highly correlated from one phase to the next as were the correlations between the 50 ms and 500 ms conditions. Thus, visual appeal can be assessed within 50 ms, suggesting that web designers have about 50 ms to make a good first impression. 相似文献
52.
《Ergonomics》2012,55(9):1295-1319
This study examines effects of momentary changes in mental effort on cardiovascular and eye activity measures. A total of 19 male pilots performed an instrument flight task. Task load was manipulated by having the pilots perform flight manoeuvres of varying complexity. Multilevel analyses demonstrated clear effects of momentary changes in mental effort on both the cardiovascular and the eye activity measures. An increase in task load resulted in an increase of heart rate and a decrease in heart rate variability, mean dwell time and fixation duration. Heart rate differentiated between resting period and task execution. Heart rate variability from short data segments provided more insight in intermediate levels of mental effort. The eye activity measures were sensitive to intermediate levels of mental effort as well. Attitude changes resulted in an increase of mean dwell time and mean fixation duration. Task analysis is required to use eye measures as valid indices of mental effort. Having indications of the effects of changing mental demands during daily work of operators is of great importance nowadays. This paper presents an approach to estimate such effects on the basis of heart rate and eye activity measures. In particular, the use of averaged short-term heart rate variability measures is a relatively new aspect. 相似文献
53.
This paper addresses target localization problem in a cooperative 3-D wireless sensor network (WSN). We employ a hybrid system that fuses distance and angle measurements, extracted from the received signal strength (RSS) and angle-of-arrival (AoA) information, respectively. Based on range measurement model and simple geometry, we derive a novel non-convex estimator based on the least squares (LS) criterion. The derived non-convex estimator tightly approximates the maximum likelihood (ML) one for small noise levels. We show that the developed non-convex estimator is suitable for distributed implementation, and that it can be transformed into a convex one by applying a second-order cone programming (SOCP) relaxation technique. We also show that the developed non-convex estimator can be transformed into a generalized trust region sub-problem (GTRS) framework, by following the squared range (SR) approach. The proposed SOCP algorithm for known transmit powers is then generalized to the case where the transmit powers are different and not known. Furthermore, we provide a detailed analysis of the computational complexity of the proposed algorithms. Our simulation results show that the new estimators have excellent performance in terms of the estimation accuracy and convergence, and they confirm the effectiveness of combining two radio measurements. 相似文献
54.
55.
56.
57.
58.
P2P电子商务信任评估机制研究 总被引:1,自引:1,他引:0
近年电子商务发展迅猛,而点对点(P2P,Peer-to Peer)电子商务更是解决了传统电子商务的服务器瓶颈问题,但信任安全始终是无法绕过的难题。为了研究P2P电子商务中节点间的信任评估,借助模糊理论的知识,提出了一种基于模糊层次分析法的P2P电子商务信任模型。该模型考虑了影响P2P电子商务信任的几个因素,并用模糊层次分析法确定它们对信任度的影响权重,由综合决策计算得到节点的综合信任度。由仿真实例可以看出模型具有较好的抗欺骗能力。 相似文献
59.
首先提出了自动信任协商的通用形式化框架,并将典型的信任协商策略规约到上述框架内;其次,基于上述形式化框架对自动信任协商的形式化验证问题进行了定义,确定了形式化验证的目标以及一般流程;再次,研究了典型信任协商策略的形式化验证问题,讨论了相关问题的计算复杂性并得到系列结论;最后,利用逻辑编程方法和模型检测方法实现了自动信任协商的形式化验证。实验结果表明,规则数是影响形式化验证系统运行时间的关键因素,逻辑编程方法和模型检测方法在规则较少时效率较高,但逻辑编程方法的可扩展性不及模型检测方法。 相似文献
60.
近似于人际关系网络,P2P文件共享交易存在着相互信任的问题.服务请求节点和服务提供节点是参与文件共享交易的两类实体,通过分析两者的信任关系,提出一种双向并发信任机制-BPTM.该信任机制研究交易双方的相互信任问题,并在此基础上建立服务选择信任模型和服务确认信任模型,实施信任关系评估的双向化.仿真与分析表明,BPTM相比传统的单向信任机制,在交易成功率上有较大的改进,可使节点之间更有效的建立互信关系. 相似文献