首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4247篇
  免费   835篇
  国内免费   882篇
电工技术   296篇
综合类   381篇
化学工业   87篇
金属工艺   61篇
机械仪表   497篇
建筑科学   193篇
矿业工程   54篇
能源动力   26篇
轻工业   101篇
水利工程   39篇
石油天然气   15篇
武器工业   49篇
无线电   361篇
一般工业技术   306篇
冶金工业   84篇
原子能技术   3篇
自动化技术   3411篇
  2024年   85篇
  2023年   195篇
  2022年   263篇
  2021年   339篇
  2020年   339篇
  2019年   269篇
  2018年   274篇
  2017年   282篇
  2016年   307篇
  2015年   280篇
  2014年   379篇
  2013年   470篇
  2012年   318篇
  2011年   319篇
  2010年   261篇
  2009年   227篇
  2008年   203篇
  2007年   261篇
  2006年   175篇
  2005年   183篇
  2004年   135篇
  2003年   123篇
  2002年   76篇
  2001年   49篇
  2000年   32篇
  1999年   21篇
  1998年   10篇
  1997年   13篇
  1996年   14篇
  1995年   12篇
  1994年   9篇
  1993年   7篇
  1992年   6篇
  1991年   3篇
  1990年   5篇
  1989年   4篇
  1988年   3篇
  1987年   3篇
  1986年   3篇
  1985年   2篇
  1980年   1篇
  1977年   1篇
  1974年   1篇
  1957年   1篇
  1955年   1篇
排序方式: 共有5964条查询结果,搜索用时 15 毫秒
101.
There are many factors that influence distance learning especially in higher education where collaborative and communicative discourse is necessary for pursuing knowledge. Social presence, among other factors, is an important concept to be facilitated, developed and sustained in distance higher education as it promotes and supports discourse based learning. This study examines the relationship among demographic and other variables, social presence and learning satisfaction. Results showed demographic variables, such as gender, online learning experience and work status were not significant factors in terms of influencing on either social presence or learning satisfaction. While media integration and instructor’s quality teaching were significant predictors of both social presence and learning satisfaction, interactivity among participants was a predictor of social presence but not of learning satisfaction. Along with the study findings, some implications were discussed for online learning practitioners in higher education setting.  相似文献   
102.
This study examined the effect of using a group awareness tool on online collaboration. Furthermore, we examined whether the effect of using a group awareness tool on online collaboration is mediated by group awareness (i.e., students’ awareness of their group members’ levels of participation). To answer these questions, we determined how often and how long 107 secondary education students used the Participation-tool (PT), a group awareness tool designed to visualize group members’ relative contribution to the online collaborative process. Our analyses show that duration of PT use (how long students displayed the tool on their screens) significantly predicted group members’ participation in the online dialogue, their participation when writing collaborative texts, equality of participation within the group, and coordination and regulation of activities in the relational space (i.e., discussing the collaboration process with group members). No effect of using the PT on group performance was found. Mediation analyses showed that the effect of using the PT is only partially mediated by group awareness: an indirect effect of using the PT, via enhanced awareness of participation, on student participation during chat discussions and the collaborative writing process was found.  相似文献   
103.
多星系统相对轨道的自适应协同控制   总被引:1,自引:0,他引:1  
基于一致性理论,在无向拓扑结构上对多星系统相对轨道的协同控制问题进行了研究.本文考虑近地卫星相对轨道的非线性方程,首先设计控制律使得多星系统形成目标队形,并给出了速度阻尼和通信拓扑(相对速度间的拓扑关系)连通性之间的关系;其次,针对卫星质量具有不确定性的情形,设计了新的辅助变量,提出了自适应的协同控制律,这里要求传感(相对位置间的拓扑关系)和通信具有相同的拓扑结构.最后对4颗卫星的编队飞行进行了仿真分析,仿真结果表明本文设计的协同控制律是有效可行的.  相似文献   
104.
Collaboration becomes an essential competency in the current knowledge society. In this study, a collaborative learning environment was designed to facilitate students in group collaboration. Instructional support strategies of friendship and meaningful learning tasks were applied to promote collaboration. Scaffolding strategies such as writing progress reports and developing product versions were used to coordinate and monitor the collaborative learning environment. In addition, the online file sharing tool DriveHQ was used to facilitate collaboration. Four classes of students used the learning environment to complete their final project in pairs. Results showed friendship and meaningful learning tasks helped to promote individual accountability and positive interdependence, and the use of progress reports and product versions was useful for coordinating and monitoring the learning process. However, additional strategies might be needed for more effective collaboration to take place. Issues involved in this study are discussed.  相似文献   
105.
Within the framework of research that describes the processes of collaborative knowledge construction in computer-supported collaborative learning (CSCL) environments, the present work has three objectives: (i) the identification of the strategies of six small groups of university students for the elaboration of written products in a CSCL environment; (ii) seek relations between the identified writing strategies and the processes and phases of collaborative knowledge construction in the groups; and (iii) relate these strategies and phases with the learning results obtained by the groups. We carried out a multiple-case study, with the analysis of four different didactic sequences, in two different virtual learning and teaching settings. In each setting, three student groups were studied, where each had to collaboratively develop between four and eight written products. For all the studied groups, the analysis enabled the identification of five types of strategies in the preparation of the elaboration of written products, and four types of phases of collaborative knowledge construction, which are interrelated and also connected with the grades that the groups obtained in each case.  相似文献   
106.
This study examines an alternative function of information sharing – social construction of meaning. Drawing on social construction, social interaction, and task closure theories, we explored the influence of both the media environment in which students are situated and the medium that group members choose to communicate with one another on the intricate relationships among breadth of information sharing, depth of information sharing, and performance of computer-supported collaborative learning (CSCL). A total of 126 students participated in the experiment – including 63 students (15 groups of four students and one group of three students) in the control and experimental groups respectively. Our findings show that most of the proposed hypotheses are supported. Intersubjective interpretation underlies groups information sharing and plays a key role in student learning performance. Evidence shows that when facing a relatively complex task in multimedia environments, students who choose to utilize a medium lower in social presence (i.e., electronic information sharing) are more likely to achieve task closure than a medium higher in social presence (i.e., verbal information sharing). This in turn leads to higher learning performance. The implications for both theory and pedagogy are also discussed.  相似文献   
107.
Although many children are technically skilled in using the Web, their competences to use it in a critical and meaningful way are usually less well developed. In this article, we report on a multiple case study focusing on the possibilities and limitations of collaborative inquiry activities as an appropriate context to acquire Web literacy skills in primary education. Four 5th grade school teachers and their students worked with collaborative inquiry activities on the subject of ‘healthy food’. The project was aimed at both the development of Web literacy skills and content knowledge building. Data from a variety of sources were collected: videotaped and written lesson observations, interviews with teachers and students, teacher diaries, student questionnaires, and student assignments. The teachers appeared to be able to carry out the program to varying degrees. Contextual factors that influenced the realization of the project’s goals and results were the adequacy of the research questions formulated by students, students’ inquiry skills, and the teachers’ teaching styles. Students’ learning results show that it is possible to teach Web literacy skills in the context of collaborative inquiry activities. All classes show knowledge gain with regard to the subject healthy food and all classes but one show knowledge gain with regard to Web literacy skills. Although many students show adequate use of particular Web searching, reading and evaluating skills after the project, inconsistency, impulsiveness and impatience are also typical of their Web behaviour. In the context of collaborative inquiry activities teachers are challenged to deal with the paradox that they want their students to be active knowledge builders with help of the Web, whereas the Web seems to invite students to be more or less passive searchers.  相似文献   
108.
This case study illustrates the sequential process of the joint and individual knowledge elaboration in a computer-supported collaborative learning (CSCL) environment. The case comprised an Internet-based physics problem-solving platform. Six Dutch secondary school students (three males, three females) participated in the three-week experiment. They were paired based on self-selection. Each dyad was asked to collaborate on eight moderately structured problems concerning Newtonian mechanics. Their online interactions, including their textual and pictorial messages, were categorized and sequentially plotted. The three dyads showed three different collaboration patterns in terms of joint and individual knowledge elaboration.  相似文献   
109.
A desirable characteristic for an e-learning system is to provide the learner the most appropriate information based on his requirements and preferences. This can be achieved by capturing and utilizing the learner model. Learner models can be extracted based on personality factors like learning styles, behavioral factors like user’s browsing history and knowledge factors like user’s prior knowledge. In this paper, we address the problem of extracting the learner model based on Felder–Silverman learning style model. The target learners in this problem are the ones studying basic science. Using NBTree classification algorithm in conjunction with Binary Relevance classifier, the learners are classified based on their interests. Then, learners’ learning styles are detected using these classification results. Experimental results are also conducted to evaluate the performance of the proposed automated learner modeling approach. The results show that the match ratio between the obtained learner’s learning style using the proposed learner model and those obtained by the questionnaires traditionally used for learning style assessment is consistent for most of the dimensions of Felder–Silverman learning style.  相似文献   
110.
When implementing multivalued consensus using binary consensus, previous algorithms assume the availability of uniform reliable broadcast, which is not implementable in systems with fair-lossy links. In this paper, we show that with binary consensus we can implement uniform reliable broadcast directly in systems with fair-lossy links, and thus the separate assumption of the availability of uniform reliable broadcast is not necessary. We further prove that, when binary consensus instances are available only as black boxes, any implementation of uniform reliable broadcast in the fair-lossy link model requires the invocation of an infinite number of binary consensus instances even if no process ever broadcasts any messages, and this is true even when multivalued consensus is used.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号