全文获取类型
收费全文 | 21609篇 |
免费 | 1892篇 |
国内免费 | 1105篇 |
专业分类
电工技术 | 828篇 |
技术理论 | 3篇 |
综合类 | 2798篇 |
化学工业 | 1439篇 |
金属工艺 | 500篇 |
机械仪表 | 732篇 |
建筑科学 | 6015篇 |
矿业工程 | 1231篇 |
能源动力 | 580篇 |
轻工业 | 731篇 |
水利工程 | 1628篇 |
石油天然气 | 799篇 |
武器工业 | 236篇 |
无线电 | 1238篇 |
一般工业技术 | 1248篇 |
冶金工业 | 937篇 |
原子能技术 | 163篇 |
自动化技术 | 3500篇 |
出版年
2024年 | 81篇 |
2023年 | 284篇 |
2022年 | 549篇 |
2021年 | 607篇 |
2020年 | 593篇 |
2019年 | 476篇 |
2018年 | 416篇 |
2017年 | 560篇 |
2016年 | 614篇 |
2015年 | 705篇 |
2014年 | 1273篇 |
2013年 | 1124篇 |
2012年 | 1255篇 |
2011年 | 1609篇 |
2010年 | 1335篇 |
2009年 | 1457篇 |
2008年 | 1394篇 |
2007年 | 1701篇 |
2006年 | 1525篇 |
2005年 | 1273篇 |
2004年 | 1099篇 |
2003年 | 966篇 |
2002年 | 851篇 |
2001年 | 635篇 |
2000年 | 527篇 |
1999年 | 404篇 |
1998年 | 279篇 |
1997年 | 214篇 |
1996年 | 176篇 |
1995年 | 124篇 |
1994年 | 108篇 |
1993年 | 88篇 |
1992年 | 69篇 |
1991年 | 44篇 |
1990年 | 42篇 |
1989年 | 24篇 |
1988年 | 29篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1966年 | 3篇 |
1962年 | 2篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A.?Konstantinidis Th.?TsiatsosEmail author A.?Pomportsis 《Multimedia Tools and Applications》2009,44(2):279-304
E-learning systems have gone through a radical change from the initial text-based environments to more stimulating multimedia
systems. Such systems are Collaborative Virtual Environments, which could be used in order to support collaborative e-learning
scenarios. The main aim of this paper is to aid educational designers in selecting, designing and evaluating three dimensional
collaborative virtual environments in order to gain the pedagogical benefits of Computer Supported Collaborative Learning.
Therefore, this paper initially discusses the potential of three dimensional networked virtual environments for supporting
collaborative learning. Furthermore, based on a two-step platform selection process this paper (a) presents and compares three
dimensional multi-user virtual environments for supporting collaborative learning and (b) validates the most promising solution
against a set of design principles for educational virtual environments. According to these principles, an educational environment
has been implemented on top of the selected platform in order to support collaborative e-learning scenarios. The design of
this environment is also presented. In addition, this paper presents the results of three small scale studies carried out
in a tertiary education department, to assess the educational environment. This environment has been evaluated based on a
hybrid evaluation methodology for uncovering usability problems, collecting further requirements for additional functionality
to support collaborative virtual learning environments, and determining the appropriateness of different kinds of learning
scenarios.
相似文献
A. PomportsisEmail: |
92.
Namgon?Kim JongWon?KimEmail author Thomas?D.?Uram 《Multimedia Tools and Applications》2009,44(1):17-37
In multi-party collaborative environments, a group of users can share multiple media streams via IP multicasting. However,
despite of the efficiency of IP multicast, it is not widely available and alternative application-layer multicast approaches
are introduced. Application-layer multicast is advantageous, however, it incurs additional processing delays. In this paper,
we present a new hybrid-style application-layer multicast solution that satisfies both network efficiency and easy deployment.
We achieve this goal by connecting multicast islands through UDP tunnels employing UMTP (UDP multicast tunneling protocol).
We also design a MPROBE protocol to remove multicast loop among multicast island in real Internet. We verify the feasibility
of the proposed solution by implementing a prototype tool, AG Connector, that works on Access Grid multi-party collaborative
environment.
相似文献
Thomas D. UramEmail: |
93.
Many networked human-machine interface systems have a distributed structure for certain purposes such as more computational
power, tele-presence, collaboration, and portability. However, network delays are inevitable in the distributed structure,
and often make sensory information delivered behind time to the user. In the literature, the effect of network delays on the
quality of information presentation has been considered with respect to task performances in most cases. In this paper, we
pay attention to a more stringent criterion, namely whether perceptual artifacts caused by network delays are perceptible by the user. We examined minimum perceptible
visual and/or haptic rendering delays by measuring their discrimination thresholds between normal and delayed virtual environments
with and without a task, and report the results in this paper. We also provide a simple guideline for determining whether
active delay compensation algorithms are required in a networked human-machine interface system by comparing representative
network delays to the measured discrimination thresholds.
Recommended by Guest Editor Phill Kyu Rhee. This work was supported in parts by a grant R01-2006-000-10808-0 and a NRL grant
R0A-2008-000-20087-0 both from KOSEF and by a ITRC support program C1090-0804-0002 from IITA, all funded by the Korea government.
In Lee is a Ph.D student in Computer Science and Engineering at POSTECH, of Korea. He received the B.S. degree in Information and
Communication Engineering from Sungkyunkwan University in 2006. His research interests include haptics, virtual reality, and
human-computer interaction.
Seungmoon Choi is an Assistant Professor in Computer Science and engineering at POSTECH, Korea. He received the B.S. and M.S. degrees in
Control and Instrumentation Engineering from Seoul National University in 1995 and 1997, respectively, and the Ph.D. degree
in Electrical and Computer Engineering from Purdue University in 2003. His research areas include haptics, virtual reality,
data perceptualization, and applied perception. 相似文献
94.
葛红洋 《数码设计:surface》2009,(7):100-102
把建筑定义为美学带有主观随意性,局限性,除了形式美,建筑还具有实用,经济,技术等价值。本文分别从建筑的形式美,使用功能,先进技术、环境特色等方面具体阐述建筑美学,对大多数人关心的建筑美学做一个冷静而深入的思考,探究这样一种美从何而来。 相似文献
95.
金勤可 《数码设计:surface》2009,(11):143-145
居住环境的水平是一个国家经济发展、社会进步、文明与落后的重要标志。随着我国经济的快速发展和人们生活水平的不断提高,营造舒适、温馨的住居环境已经成为时代要求,本文以和谐为主题,来论述居住环境的设计思想与理论研究,从而促进我国居民居住环境空间质量的提高和发展,实现真正意义上的美化生活、美化环境。 相似文献
96.
马双 《数码设计:surface》2009,(8):124-126
建筑入口空间做为建筑与城市之间的中介空间,对建筑与城市的综合环境都有着重要的影响。本文从空间序列、形态要素以及与外部环境的协调统一等方面对建筑入口空间进行系统细致的论述和研究。 相似文献
97.
城市街区空间引导系统与人们的日常生活息息相关,为人们的出行提供了便捷的标识引导,同时它也是城市形象的重要组成部分之一。本文分析总结了该系统的设计原则,并从视觉传达学科入手分析其视觉元素的设计。为了设计无语言障碍和有个性、地域化的城市街区空间引导系统,从符号、文字、色彩三方面对其进行设计思考。 相似文献
98.
This paper aims to assess quantitatively the actual visual environment of uncontrolled urban downtown intersections in Japan in relation to frequently occurring crossing collisions and to discuss the safety countermeasures for them. In Field Study 1 dealing with direct visibility, our ultra-wide-angle photograph analysis revealed that most of the right/left-ward visible range at 11 intersections were insufficient to check safety, and the quality of direct visibility was closely associated with causing crossing collisions. The countermeasures to reduce a blind area were determined to be a top priority. In Field Study 2 dealing with indirect visibility, more than half of the 25 traffic convex mirrors had marked shortcomings for preventive safety, and ergonomics guidelines ensuring indirect visibility were proposed for installing traffic convex mirrors. Low-cost/low-technology-oriented countermeasures are highly recommended to obtain clear/sufficient images of crucial information satisfying drivers' requirements on traffic convex mirrors in accordance with those ergonomics guidelines was highly recommended. Crossing collisions could be prevented by improvement of poor direct and indirect visibility. 相似文献
99.
多媒体教学作为现代教育改革的一个重要手段,在教学中得到广泛的应用,在一定程度上提高了课堂教学的效果和教学质量。但是,随着多媒体技术的推广普及,也出现了许多亟待解决的问题。作者根据几年来的教学实践及探索,对多媒体技术谈一些粗浅的体会,供同行参考。 相似文献
100.