全文获取类型
收费全文 | 96篇 |
免费 | 0篇 |
专业分类
教育 | 41篇 |
科学研究 | 29篇 |
各国文化 | 1篇 |
体育 | 8篇 |
综合类 | 1篇 |
文化理论 | 11篇 |
信息传播 | 5篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 12篇 |
2012年 | 7篇 |
2011年 | 5篇 |
2010年 | 8篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
排序方式: 共有96条查询结果,搜索用时 78 毫秒
91.
A barrier in scaling laboratory processes into automated microfluidic devices has been the transfer of laboratory based assays: Where engineering meets biological protocol. One basic requirement is to reliably and accurately know the distribution and number of biological cells being dispensed. In this study, a novel optical counting technique to efficiently quantify the number of cells flowing into a microtube is presented. REH, B-lymphoid precursor leukemia, are stained with a fluorescent dye and frames of moving cells are recorded using a charge coupled device (CCD) camera. The basic principle is to calculate the total fluorescence intensity of the image and to divide it by the average intensity of a single cell. This method allows counting the number of cells with an uncertainty ±5%, which compares favorably to the standard biological methodology, based on the manual Trypan Blue assay, which is destructive to the cells and presents an uncertainty in the order of 20%. The use of a microdevice for vertical hydrodynamic focusing, which can reduce the background noise of out of focus cells by concentrating the cells in a thin layer, has further improved the technique. Computational fluid dynamics (CFD) simulation and confocal laser scanning microscopy images have shown an 82% reduction in the vertical displacement of the cells. For the flow rates imposed during this study, a throughput of 100–200 cells∕s is achieved. 相似文献
92.
93.
Tracing the links between science and technology: An exploratory analysis of scientists’ and inventors’ networks 总被引:1,自引:0,他引:1
The paper provides an exploratory analysis of the research networks linking scientists working in an open science environment, and researchers involved in the private technology domain. The study combines data on scientific co-authorship with data on patent co-invention, at the level of individual researchers, for three science-intensive technology fields, i.e. lasers, semiconductors and biotechnology, in order to assess the extent of the overlap between the two communities and to identify the role of key individuals in the process of knowledge transfer. Our findings reveal that the extent of the connectedness among scientists and inventors is rather large, and that particular individuals, i.e. authors-inventors, who act as gatekeepers and bridge the boundaries between the two domains, are fundamental to ensuring this connectivity. These individuals tend to occupy prominent positions in the scientific and the technological networks. However, our results also show maintaining a very central position in the scientific network may come at the expense of being able to fill a similarly central position in a technological network (and vice versa). Finally, preliminary analysis of the institutional origins of authors-inventors shows that one characteristic, distinctive of Europe compared to the United States, is associated with the relatively lower involvement of corporate scientists at the intersection between the two worlds of science and technology. 相似文献
94.
Yuxin Chen Yang Shen Pei Lin Ding Tong Yixin Zhao Stefano Allesina Xu Shen Chung-I Wu 《国家科学评论(英文版)》2019,6(6):1176
Food web and gene regulatory networks (GRNs) are large biological networks, both of which can be analyzed using the May–Wigner theory. According to the theory, networks as large as mammalian GRNs would require dedicated gene products for stabilization. We propose that microRNAs (miRNAs) are those products. More than 30% of genes are repressed by miRNAs, but most repressions are too weak to have a phenotypic consequence. The theory shows that (i) weak repressions cumulatively enhance the stability of GRNs, and (ii) broad and weak repressions confer greater stability than a few strong ones. Hence, the diffuse actions of miRNAs in mammalian cells appear to function mainly in stabilizing GRNs. The postulated link between mRNA repression and GRN stability can be seen in a different light in yeast, which do not have miRNAs. Yeast cells rely on non-specific RNA nucleases to strongly degrade mRNAs for GRN stability. The strategy is suited to GRNs of small and rapidly dividing yeast cells, but not the larger mammalian cells. In conclusion, the May–Wigner theory, supplanting the analysis of small motifs, provides a mathematical solution to GRN stability, thus linking miRNAs explicitly to ‘developmental canalization’. 相似文献
95.
Stefano Cacciamani Daniela Villani Andrea Bonanomi Claudia Carissoli Maria Giulia Olivari Laura Morganti 《Journal of Research on Technology in Education》2018,50(2):120-133
To maximize the advantages of the tablet personal computer (TPC) at school, this technology needs to be accepted by students as new tool for learning. With reference to the Technology Acceptance Model and the Unified Theory of Acceptance and Use of Technology, the aims of this study were (a) to analyze factors influencing high school students' acceptance of TPCs and (b) to detect any difference in this influence considering the frequency of TPC use, students' gender, and school grade. Two hundred and ninety-six students from six high schools in the Milan area participated in the study. Data were collected using an online survey. The results showed that empowerment in learning, perceived usefulness, and support conditions affect learning use, and empowerment in learning and affect influence communicative use of TPCs. The implications of these results are discussed. (Keywords: tablets, acceptance, digital technologies, high school, path analysis) 相似文献
96.
Domenica Paoletti Dario Ambrosini Stefano Sfarra Fabio Bisegna 《Journal of Cultural Heritage》2013,14(2):116-121
Conserving architectural heritage usually requires a multidisciplinary approach involving a variety of professionals and organizations. Since the evaluation of the state of conservation of historical buildings using destructive techniques should be avoided to prevent the integrity of the cultural heritage, the development of non-destructive and non-contact techniques is very important. InfraRed (IR) thermography is a non-destructive powerful tool for fast and accurate building diagnostics. In the investigation of historical structures, where a restoration or conservation treatment can cause irreversible damage to the structure, it is considered to be of most importance. A campaign of thermographic surveys were conducted on a large part of the historical cultural heritage of L’Aquila and its surroundings. In this paper we present the results of the study for the Church of Santa Maria ad Cryptas (XIII century), one of the most ancient buildings in the surroundings of L’Aquila and one of the best examples of Gothic art in Abruzzo, with the aim to evaluate the correspondence between the damage induced by the earthquake and the previous thermographic results, in order to validate the effectiveness of thermography and its role in preventive diagnosis. 相似文献