全文获取类型
收费全文 | 21716篇 |
免费 | 90篇 |
国内免费 | 10篇 |
专业分类
教育 | 15725篇 |
科学研究 | 2568篇 |
各国文化 | 122篇 |
体育 | 1048篇 |
综合类 | 6篇 |
文化理论 | 476篇 |
信息传播 | 1871篇 |
出版年
2020年 | 104篇 |
2019年 | 165篇 |
2018年 | 2316篇 |
2017年 | 2248篇 |
2016年 | 1729篇 |
2015年 | 233篇 |
2014年 | 306篇 |
2013年 | 2113篇 |
2012年 | 388篇 |
2011年 | 849篇 |
2010年 | 957篇 |
2009年 | 574篇 |
2008年 | 819篇 |
2007年 | 1309篇 |
2006年 | 236篇 |
2005年 | 532篇 |
2004年 | 568篇 |
2003年 | 481篇 |
2002年 | 245篇 |
2001年 | 133篇 |
2000年 | 174篇 |
1999年 | 129篇 |
1998年 | 86篇 |
1997年 | 96篇 |
1996年 | 94篇 |
1994年 | 101篇 |
1993年 | 112篇 |
1992年 | 144篇 |
1991年 | 157篇 |
1990年 | 148篇 |
1989年 | 155篇 |
1988年 | 127篇 |
1987年 | 142篇 |
1986年 | 147篇 |
1985年 | 163篇 |
1984年 | 155篇 |
1983年 | 154篇 |
1982年 | 120篇 |
1981年 | 134篇 |
1980年 | 111篇 |
1979年 | 151篇 |
1978年 | 153篇 |
1977年 | 108篇 |
1976年 | 109篇 |
1975年 | 101篇 |
1974年 | 85篇 |
1973年 | 101篇 |
1972年 | 87篇 |
1971年 | 80篇 |
1970年 | 83篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
P. C. Deshmukh Parth Rajauria Abiya Rajans B. R. Vyshakh Sudipta Dutta 《Resonance》2017,22(9):847-866
The brachistochrone problem posed by Bernoulli and its solution highlights one of the most famous experiments in physics which illustrates the variational principle. This pedagogical study is designed to ignite a classroom discussion on the variational problem. We overview the Euler–Lagrange formalism of the variational principle and obtain the solution to the brachistochrone problem. We demonstrate the success of the variational method using brachistochrone models which were fabricated specially for this purpose. 相似文献
982.
983.
984.
A two-bottle testing method generally is regarded as a more sensitive measure of taste aversions than a one-bottle test. The current research compared the sensitivity of one-bottle and two-bottle tests in the detection of taste aversions. Specifically, the experiments were designed to detect both overshadowing (single- vs. compound-element conditioning) and retention interval (5 days vs. 1 day) effects. The groups tested with the one-bottle method evidenced both significant overshadowing and stronger aversions at 5-day retention intervals. On the other hand, the differences on these measures were not significant with the two-bottle tests. It is suggested that the efficacy of the two-bottle test be re-evaluated since it may obscure between-group differences in aversion strength. 相似文献
985.
Glenna Sloan 《Children‘s Literature in Education》2009,40(2):120-135
Northrop Frye (1912–1991) was one of the leading literary theorists of his day, and this article shows the ways in which his
theories continue to be relevant for both the field of literary criticism and elementary classroom education today. The author,
an eminent scholar in the field of children’s literature in her own right and a student of Northrop Frye, presents her interpretation
of his major theories as they relate to reading and writing pedagogy in the elementary school classroom. This article articulates
some of the key issues developed in the author's book, The Child As Critic, which has undergone a number of printings and editions, and which may well be as close as we get to a handbook for teaching
the art of literature, as Northrop Frye might have written it. 相似文献
986.
In this paper we describe how progressive download and adaptive streaming can be combined into a simple and efficient streaming framework. Based on the MPEG-4 file format (MP4) we use HTTP for transport and argue that these two components are sufficient for specifying an open streaming architecture. The client selects appropriate chunks from the MP4 file to be transferred based on (1) the header information (i.e. the “moov” box) in the first part of the file and (2) his observation of network throughput. The framework is completely client driven which allows for better server scalability and reduces signalling overhead. We discuss architecture and implementation issues such as complexity, interoperability and scalability and compare to 3GPP PSS Rel-6 adaptive streaming when appropriate. Measurements from a simple MP4/HTTP streaming client are presented showing that appropriate chunks are selected such that increased reliability is achieved. 相似文献
987.
In Western societies scientists are increasingly expected to seek media exposure and cooperate with industry. Little attention
has been given to the way such expectations affect the role of scientific experts in society. To investigate scientists’ own
perspectives on these issues eight exploratory, in-depth interviews were conducted in Denmark with reputable nutrition scientists.
Additionally, eight interviews were held with ‘key informants’ from the field of nutrition policy. It was found that nutrition
scientists experience two dilemmas: first, between their aspiration to make a collective impact on public health and the powerful
incentives of each to appear frequently in the media with new messages; second, between their need to cooperate with the food
industry for financial reasons and their fear that this may compromise their independence and scientific integrity. It is
argued that the dilemmas identified in this study should be dealt with openly by the relevant groups of scientists. 相似文献
988.
989.
Eun-hye Park Won-young Bae Jae-yeon Kim Kee-tae Kim Hyun-dong Paik 《Journal of Zhejiang University. Science. B》2017,18(9):816-824
The inhibitory effects of Lactobacillus plantarum-fermented and non-fermented Inula britannica extracts on the tyrosinase activity were comparatively investigated to examine whether and how they improve the whitening activity, and the contents of total flavonoids and polyphenolics as bioactive compounds were determined. The skin whitening activity using in vitro or ex vivo tyrosinase and L-3,4-dihydroxyphenylalanine (L-DOPA) staining was examined. The total flavonoid content (TFC) was increased by 13.4% after 72 h-fermentation. The viabilities of the B16F10 cells treated with the fermented and non-fermented control extracts were 100.26% and 92.15% at 500 μg/ml, respectively. In addition, the inhibition of tyrosinase activity was increased by the fermented samples from 29.33% to 41.74% following fermentation for up to 72 h. The tyrosinase activity of the untreated control group was increased to 145.69% in B16F10 cells. The results showed that I. britannica fermented by L. plantarum dose-dependently inhibited tyrosinase activity, which was stimulated by α-melanocyte stimulating hormone. These results suggest that lactic fermented I. britannica extracts can be used as effective skin-whitening materials. 相似文献
990.
The main purpose of this paper is to investigate the intellectual structure of the research on educational technology in science education (ETiSE) within the most recent years (2008–2013). Based on the criteria for educational technology research and the citation threshold for educational co-citation analysis, a total of 137 relevant ETiSE papers were identified from the International Journal of Science Education, the Journal of Research in Science Teaching, Science Education, and the Journal of Science Education and Technology. Then, a series of methodologies were performed to analyze all 137 source documents, including document co-citation analysis, social network analysis, and exploratory factor analysis. As a result, 454 co-citation ties were obtained and then graphically visualized with an undirected network, presenting a global structure of the current ETiSE research network. In addition, four major underlying intellectual subfields within the main component of the ETiSE network were extracted and named as: (1) technology-enhanced science inquiry, (2) simulation and visualization for understanding, (3) technology-enhanced chemistry learning, and (4) game-based science learning. The most influential co-citation pairs and cross-boundary phenomena were then analyzed and visualized in a co-citation network. This is the very first attempt to illuminate the core ideas underlying ETiSE research by integrating the co-citation method, factor analysis, and the networking visualization technique. The findings of this study provide a platform for scholarly discussion of the dissemination and research trends within the current ETiSE literature. 相似文献