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   54077篇
  免费   4752篇
  国内免费   2460篇
电工技术   2850篇
技术理论   3篇
综合类   5629篇
化学工业   8085篇
金属工艺   2905篇
机械仪表   2922篇
建筑科学   6728篇
矿业工程   2465篇
能源动力   1419篇
轻工业   5912篇
水利工程   2064篇
石油天然气   2553篇
武器工业   322篇
无线电   3501篇
一般工业技术   5306篇
冶金工业   2855篇
原子能技术   1419篇
自动化技术   4351篇
  2024年   230篇
  2023年   782篇
  2022年   1264篇
  2021年   1576篇
  2020年   1461篇
  2019年   1307篇
  2018年   1266篇
  2017年   1513篇
  2016年   1730篇
  2015年   1807篇
  2014年   2868篇
  2013年   3064篇
  2012年   3595篇
  2011年   3969篇
  2010年   2979篇
  2009年   3112篇
  2008年   2865篇
  2007年   3708篇
  2006年   3489篇
  2005年   2974篇
  2004年   2466篇
  2003年   2329篇
  2002年   1885篇
  2001年   1576篇
  2000年   1314篇
  1999年   1071篇
  1998年   807篇
  1997年   671篇
  1996年   587篇
  1995年   558篇
  1994年   416篇
  1993年   358篇
  1992年   304篇
  1991年   186篇
  1990年   208篇
  1989年   179篇
  1988年   150篇
  1987年   111篇
  1986年   80篇
  1985年   74篇
  1984年   64篇
  1983年   29篇
  1982年   37篇
  1981年   36篇
  1980年   36篇
  1979年   31篇
  1977年   17篇
  1976年   18篇
  1975年   20篇
  1974年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Studies have demonstrated that students prefer PowerPoint and respond favorably to classes when it is used. Few studies have addressed the physical structure of PowerPoint. In this study, students enrolled in several psychology classes on two campuses completed a 36 item questionnaire regarding their preferences for the use of PowerPoint in the classroom. Students preferred the use of key phrase outlines, pictures and graphs, slides to be built line by line, sounds from popular media or that support the pictures or graphics on the slide, color backgrounds, and to have the lights dimmed. It is recommended that professors pay attention to the physical aspects of PowerPoint slides and handouts to further enhance students’ educational experience.  相似文献   
952.
Despite the assumption that the integration of ICT influences the entire school system, research focusing on ICT in schools is generally limited to the study of variables at class level. In contrast to these studies, the present research explores ICT integration from a school improvement approach. More particularly, it examines the local school policy with respect to ICT integration from both the principal’s perspective and perceptions of teachers. Furthermore, it studies the relationship between school policies and the actual use of ICT in the classroom. To answer the research questions, a representative sample of 53 primary school principals was interviewed. In addition, the interview data were supplemented with survey data of 574 teachers from the same 53 schools. What emerged from the analyses was that school-related policies, such as an ICT plan, ICT support and ICT training have a significant effect on class use of ICT. In addition, the findings from the interviews indicate that school policies are often underdeveloped and underutilised. The discussion section focuses on challenges to improve the potential of an ICT school policy.  相似文献   
953.
Given the prevalence of computers in education today, it is critical to understand teachers’ perspectives regarding computer integration in their classrooms. The current study surveyed a random sample of a heterogeneous group of 185 elementary and 204 secondary teachers in order to provide a comprehensive summary of teacher characteristics and variables that best discriminate between teachers who integrate computers and those who do not. Discriminant Function Analysis indicated seven variables for elementary teachers and six for secondary teachers (accounting for 74% and 68% of the variance, respectively) that discriminated between high and low integrators. Variables included positive teaching experiences with computers; teacher’s comfort with computers; beliefs supporting the use of computers as an instructional tool; training; motivation; support; and teaching efficacy. Implications for support of computer integration in the classroom are discussed.  相似文献   
954.
Fengfeng Ke   《Computers & Education》2008,51(4):1609-1620
Employing mixed-method approach, this case study examined the in situ use of educational computer games in a summer math program to facilitate 4th and 5th graders’ cognitive math achievement, metacognitive awareness, and positive attitudes toward math learning. The results indicated that students developed more positive attitudes toward math learning through five-week computer math gaming, but there was no significant effect of computer gaming on students’ cognitive test performance or metacognitive awareness development. The in-field observation and students’ think-aloud protocol informed that not every computer math drill game would engage children in committed learning. The study findings have highlighted the value of situating learning activities within the game story, making games pleasantly challenging, scaffolding reflections, and designing suitable off-computer activities.  相似文献   
955.
The explosive growth of the Internet has made the knowledge and skills for creating Web pages into general subjects that all students should learn. It is now common to teach the technical side of the production of Web pages and many teaching materials have been developed. However teaching the aesthetic side of Web page design has been neglected, and students not in art or design majors are normally confronted with difficulties when they do expressive design of Web pages.  相似文献   
956.
The widespread availability of digital learning resources in a variety of media formats offers the possibility to make a profound difference in education. This potential has not been fully realised for range of interrelated reasons. In this paper we study the key characteristics of learning resources that have proved effective in changing learning and teaching, and relate them to existing frameworks for understanding resources. We outline the relationships between resources, their users, and the way they are used, and explore issues that influence practitioners in choosing a particular resource. Our study is based on a review of resources for e-learning and chemistry in post-compulsory education, undertaken for the UK Joint Information Systems Committees (JISC), as part of a wider study examining ‘The Effectiveness of Resources, Tools and Support Services used by Tutors in Designing and Delivering E-Learning Activities’.  相似文献   
957.
One of the key requirements biomedical and pharmaceutical sensors have to satisfy is their ability to withstand sterilization cycle. In this paper, the influence of γ-sterilization on the electrical and electrochemical characterizations of pH-sensitive chemical field effect transistors (pH-ChemFET) is examined before and after γ-irradiation. It is shown that γ-irradiation is suitable for pH-ChemFETs sterilization in the field of in-vitro analysis and more precisely for single-use bioreactors.  相似文献   
958.
This paper describes the design and modelling of ultrasonic tomography for two-component high-acoustic impedance mixture such as liquid/gas and oil/gas flow which commonly found in chemical columns and industrial pipelines. The information obtained through this research has proven to be useful for further development of ultrasonic tomography. This includes acquiring and processing ultrasonic signals from the transducers to obtain the information of the spatial distributions of liquid and gas in an experimental column. Analysis on the transducers’ signals has been carried out to distinguish between the observation time and the Lamb waves. The information obtained from the observation time is useful for further development of the image reconstruction.  相似文献   
959.
So far, most of the applications of robotic technology to education have mainly focused on supporting the teaching of subjects that are closely related to the Robotics field, such as robot programming, robot construction, or mechatronics. Moreover, most of the applications have used the robot as an end or a passive tool of the learning activity, where the robot has been constructed or programmed. In this paper, we present a novel application of robotic technologies to education, where we use the real world situatedness of a robot to teach non-robotic related subjects, such as math and physics. Furthermore, we also provide the robot with a suitable degree of autonomy to actively guide and mediate in the development of the educational activity. We present our approach as an educational framework based on a collaborative and constructivist learning environment, where the robot is able to act as an interaction mediator capable of managing the interactions occurring among the working students. We illustrate the use of this framework by a 4-step methodology that is used to implement two educational activities. These activities were tested at local schools with encouraging results. Accordingly, the main contributions of this work are: i) A novel use of a mobile robot to illustrate and teach relevant concepts and properties of the real world; ii) A novel use of robots as mediators that autonomously guide an educational activity using a collaborative and constructivist learning approach; iii) The implementation and testing of these ideas in a real scenario, working with students at local schools.
Alvaro Soto (Corresponding author)Email:
  相似文献   
960.
For many years, the author has been involved in teaching and research in the use of Operations Research as a tool of analysis to study food security problems in sub‐Saharan Africa, in particular, grass root problems of poor farmers. The paper presents an introduction to the way Operations Research methods have been applied in case studies and research projects, and discusses in retrospect the author's views on the strengths and limitations of the application of Operations Research. The paper has in particular been written for people who are not familiar with applications of Operations Research in agriculture, and are interested to learn about its potential usefulness in practice. The retrospective part is largely based on food security studies in e.g. Tanzania, Burkina Faso, Bénin, Togo and Eritrea and on participation in several interdisciplinary research programmes in Africa.  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