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   526篇
  免费   15篇
  国内免费   1篇
教育   333篇
科学研究   127篇
各国文化   5篇
体育   29篇
综合类   4篇
文化理论   5篇
信息传播   39篇
  2023年   6篇
  2022年   9篇
  2021年   22篇
  2020年   12篇
  2019年   30篇
  2018年   30篇
  2017年   43篇
  2016年   23篇
  2015年   22篇
  2014年   34篇
  2013年   70篇
  2012年   37篇
  2011年   21篇
  2010年   27篇
  2009年   23篇
  2008年   26篇
  2007年   14篇
  2006年   9篇
  2005年   11篇
  2004年   10篇
  2003年   9篇
  2002年   12篇
  2001年   6篇
  2000年   7篇
  1999年   1篇
  1997年   1篇
  1996年   2篇
  1995年   1篇
  1993年   2篇
  1992年   2篇
  1991年   3篇
  1990年   3篇
  1989年   2篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1976年   1篇
  1975年   1篇
  1970年   1篇
  1967年   1篇
排序方式: 共有542条查询结果,搜索用时 15 毫秒
171.
提高能效和燃料转换效率是温室气体减排战略的一部分。过去二十年,很多研究显示这两方面带来气候变化以外的好处,多半介于这些政策方案实施成本的30%到超过100%。国际上,政策制定者对于分析能效政策和燃料转换效率政策同时纳入对温室气体和非温室气体两方面影响的探讨愈来愈感兴趣。欧盟、美国与日本已开发出一套相当成熟的方法。通常,协同效益的定量工作可分为三类:(1)协同效益模型;(2)事前的政策评估方法;(3)由学者建立的框架,意在改善这方面的研究,并将协同效益应用到更多的地区和政策方案上。 表ES-1将协同效益定量方面的几个重点模型、指南和框架做了摘要。  相似文献   
172.
Good quality deoxyribonucleic acid (DNA) is the pre-requisite for its downstream applications. The presence of high concentrations of polysaccharides, polyphenols, proteins, and other secondary me- tabolites in mango leaves poses problem in getting good quality DNA fit for polymerase chain reaction (PCR) applications. The problem is exacerbated when DNA is extracted from mature mango leaves. A reliable and modified protocol based on the cetyl- trimethylammonium bromide (CTAB) method for DNA extraction from mature mango leaves is described here. High concentrations of inert salt were used to remove polysaccharides; Polyvinylpyrrolidone (PVP) and β-mercaptoethanol were employed to manage phenolic compounds. Extended chloroform-isoamyl alcohol treatment followed by RNase treatment yielded 950?1050 μg of good quality DNA, free of protein and RNA. The problems of DNA degradation,contamination, and low yield due to irreversible binding of phenolic compounds and coprecipitation of polysaccharides with DNA were avoided by this method. The DNA isolated by the modified method showed good PCR amplification using simple se- quence repeat (SSR) primers. This modified protocol can also be used to extract DNA from other woody plants having similar problems.  相似文献   
173.
174.
Educational Research for Policy and Practice - Much has been written, published, and presented about the important role and uses of technology in English language teaching (ELT) today and the...  相似文献   
175.

The present study explored the direct and indirect (serial multiple mediation of math self-efficacy and math enjoyment) effects of perceived parental math support on middle school students’ math engagement. A total of 374 middle school students ranging the age of 11 to 15 years completed a set of questionnaires assessing perceived parental math support, math self-efficacy, math enjoyment, and math engagement. In the analysis of structural model, a multiple-step multiple mediation analysis was employed. The findings indicated that perceived parental math support was directly and positively associated with math engagement. Additionally, math self-efficacy and math enjoyment sequentially mediated the relationship between parental math support and math engagement. The limitations and implications of the results are discussed and suggestions for future research are proposed.

  相似文献   
176.
177.
178.
ABSTRACT

Contemporary anti-Islamic discourses in Australia construct Islam as an uncivilised belief system and its Muslim followers as homogenous unassimilable Others. Within these discourses, the diversity among Muslim women has been overshadowed, and they are constructed as a monolithic ‘veiled’ woman. Drawing on 20 conversational interviews with veiled and unveiled Australian Muslim women from various cultural backgrounds, this paper explores the diverse ways in which Muslim women resist and challenge anti-Islamic discourses on Islam, Muslims and Muslim women. Guided by intersectional theories on identity and resistance, our analysis show that the women drew on discursive and performative strategies to contest anti-Islamic representations that homogenise and vilify Muslims and construct Muslim women as veiled and oppressed. The findings also show that the ways in which women contested hegemonic anti-Islamic representations were diverse and informed by intersecting power and social locations, including race, ethnicity, gender and sexuality. Implications for research on resistance and identity negotiations of minority groups are discussed.  相似文献   
179.
The purpose of the current study was to investigate the effectiveness of interacting with animations using mobile devices on grade 12 students’ spatial and reasoning abilities. The study took place in a grade 12 context in Oman. A quasi-experimental design was used with an experimental group of 32 students and a control group of 28 students. The experimental group studied chemistry using mobile tablets that had a digital instructional package with different animation and simulations. There was one tablet per student. A spatial ability test and a scientific reasoning test were administered to both groups prior and after the study, which lasted for 9 weeks. The findings showed that there were significant statistical differences between the two groups in terms of spatial ability in favour of the experimental group. However, there were no differences between the two groups in terms of reasoning ability. The authors reasoned that the types of animations and simulations used in the current study featured a wide range of three-dimensional animated illustrations at the particulate level of matter. Most probably, this decreased the level of abstractness that usually accompanies chemical entities and phenomena and helped the students to visualize the interactions between submicroscopic entities spatially. Further research is needed to decide on types of scientific animations that could help students improve their scientific reasoning.  相似文献   
180.
Cells and cell-free solutions of the culture filtrate of the bacterial symbiont, Xenorhabdus nematophila taken from the entomopathogenic nematode Steinernema carpocapsae in aqueous broth suspensions were lethal to larvae of the diamondback moth Plutella xylostella. Their application on leaves of Chinese cabbage indicated that the cells can penetrate into the insects in the absence of the nematode vector. Cell-free solutions containing metabolites were also proved as effective as bacterial cells suspension. The application of aqueous suspensions of cells of X. nematophila or solutions containing its toxic metabolites to the leaves represents a possible new strategy for controlling insect pests on foliage.  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