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   237篇
  免费   2篇
教育   135篇
科学研究   26篇
各国文化   2篇
体育   39篇
文化理论   3篇
信息传播   34篇
  2023年   1篇
  2022年   4篇
  2021年   6篇
  2020年   3篇
  2019年   13篇
  2018年   22篇
  2017年   13篇
  2016年   18篇
  2015年   8篇
  2014年   11篇
  2013年   35篇
  2012年   14篇
  2011年   5篇
  2010年   7篇
  2009年   5篇
  2008年   8篇
  2007年   4篇
  2006年   3篇
  2005年   7篇
  2004年   6篇
  2003年   3篇
  2002年   4篇
  2001年   2篇
  2000年   4篇
  1999年   3篇
  1998年   2篇
  1997年   1篇
  1996年   1篇
  1993年   1篇
  1986年   1篇
  1983年   1篇
  1981年   1篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1976年   2篇
  1975年   5篇
  1974年   1篇
  1973年   2篇
  1971年   1篇
  1969年   1篇
  1964年   1篇
  1956年   1篇
  1872年   1篇
  1871年   1篇
  1828年   1篇
排序方式: 共有239条查询结果,搜索用时 372 毫秒
1.
2.
ABSTRACT

Moving beyond the dominant bag-of-words approach to sentiment analysis we introduce an alternative procedure based on distributed word embeddings. The strength of word embeddings is the ability to capture similarities in word meaning. We use word embeddings as part of a supervised machine learning procedure which estimates levels of negativity in parliamentary speeches. The procedure’s accuracy is evaluated with crowdcoded training sentences; its external validity through a study of patterns of negativity in Austrian parliamentary speeches. The results show the potential of the word embeddings approach for sentiment analysis in the social sciences.  相似文献   
3.
Background: University physics students were engaged in open-ended thermodynamics laboratory activities with a focus on understanding a chosen phenomenon or the principle of laboratory apparatus, such as thermal radiation and a heat pump. Students had access to handheld infrared (IR) cameras for their investigations.

Purpose: The purpose of the research was to explore students’ interactions with reformed thermodynamics laboratory activities. It was guided by the research question: How do university physics students make use of IR cameras in open-ended investigation of thermal radiation as a phenomenon?

Sample: The study was conducted with a class of first-year university physics students in Sweden. The interaction with the activities of four of the students was selected for analysis. The four students are males.

Design and methods: We used a qualitative, interpretive approach to the study of students’ interaction. The primary means of data collection was video recording of students’ work with the laboratory activities and their subsequent presentations. The analysis focused on how IR cameras helped students notice phenomena relating to thermal radiation, with comparison to previous research on students’ conceptions of thermal radiation.

Results: When using the IR camera, students attended to the reflection of thermal radiation on shiny surfaces, such as polished metals, windows or a whiteboard and emissive properties of surfaces of different types. In this way, they went beyond using the technology as a temperature probe. Students were able to discuss merits and shortcomings of IR cameras in comparison with digital thermometers.

Conclusions: With the help of IR cameras, university physics students attend to thermal phenomena that would otherwise easily go unnoticed.  相似文献   
4.
This article was motivated by the inquiry of the National Heritage Committee of the British House of Commons into the price of compact discs in 1993. Its general thrust is to foster the dialogue between sociological approaches to the study of innovation and microeconomic theory. To do this, it presents a comprehensive case study of technological innovation in the market for recorded music in Britain. The material is analysed with the aid of the ‘sociotechnical constituencies’ approach recently proposed in this journal by Alfonso Molina, followed by a game theoretical analysis of competitive alignment between the dominant constituents. Using this interdisciplinary approach, the article argues that technological innovation may induce price rigidities by allowing the establishment of focal points for tacit collusion. The innovation of compact discs enabled the major record companies to redefine the overall price level to their advantage, after the industry had undergone a period of profit-squeezing price-competition. This has the important policy implication that radical product innovation may call for regulative changes in the techno-institutional structure of the market.  相似文献   
5.
Stability in cardiac indicators before birth and their utility in predicting variation in postnatal development were examined. Fetal heart rate and variability were measured longitudinally from 20 through 38 weeks gestation (n = 137) and again at age 2 (n = 79). Significant within-individual stability during the prenatal period and into childhood was demonstrated. Fetal heart rate variability at or after 28 weeks gestation and steeper developmental trajectories were significantly associated with mental and psychomotor development at 2 years (n = 82) and language ability at 2.5 years (n = 61). These data suggest that the foundations of individual differences in autonomic control originate during gestation and the developmental momentum of the fetal period continues after birth.  相似文献   
6.
The reverse k-nearest neighbor (RkNN) problem, i.e. finding all objects in a data set the k-nearest neighbors of which include a specified query object, has received increasing attention recently. Many industrial and scientific applications call for solutions of the RkNN problem in arbitrary metric spaces where the data objects are not Euclidean and only a metric distance function is given for specifying object similarity. Usually, these applications need a solution for the generalized problem where the value of k is not known in advance and may change from query to query. In addition, many applications require a fast approximate answer of RkNN-queries. For these scenarios, it is important to generate a fast answer with high recall. In this paper, we propose the first approach for efficient approximative RkNN search in arbitrary metric spaces where the value of k is specified at query time. Our approach uses the advantages of existing metric index structures but proposes to use an approximation of the nearest-neighbor-distances in order to prune the search space. We show that our method scales significantly better than existing non-approximative approaches while producing an approximation of the true query result with a high recall.  相似文献   
7.
A few years ago, publishing companies started to sell digital copies of their magazines. This study investigates a consequence of this change: the increasing online trade with illegal copies. We collected data on almost 10,000 issues of German magazines that are illegally offered online. The files are distributed in a three-sided market, in which a small number of platforms bring suppliers of illegal copies, consumers, and advertisers together. The market has been growing rapidly—between 2009 and 2012 by a factor of 10. In contrast to the legal magazine market, the illegal trade mostly concerns IT and consumer electronics magazines.  相似文献   
8.
Using a membrane emulsification method based on porous hollow-fiber membranes in combination with an aqueous two-phase system (ATPS), we are able to produce “water-in-water” droplets with narrow-dispersed size distributions. The equilibrium phases of the aqueous two-phase system polyethylene glycol-dipotassium hydrogen phosphate are used for this purpose. The droplet diameter of a given fluid system is determined by the flow rates of the continuous and disperse phase as well as the hollow fiber dimensions. When diluting the disperse phase and thus moving the ATPS system out of equilibrium, the droplet size can be further reduced in comparison to the equilibrium case. Generally, droplets formed with this method have diameters 20%–60% larger than the inner hollow fiber diameter. The new strategy of diluting the disperse phase allows the production of droplet diameter below the inner diameter of the membrane.  相似文献   
9.
In the international debate surrounding transitions from school to employment, Japan and Germany are regularly cited as examples of success. This article draws on the Japanese concepts represented by two problematic groups – freeters and NEETs – to demonstrate that over recent years, young people in both countries have also been facing serious problems with the transition process. Interpretation of empirical data also, however, reveals a number of contrasts between them. We focus here on differences in their educational systems and on the role each system plays within its own society. The article also uses divergent recruitment practices and employment structures as vehicles for comparison and interpretation.  相似文献   
10.
Instructional Science - Extensive research has established that successful learning from an example is conditional on an important learning activity: self-explanation. Moreover, a model for...  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