全文获取类型
收费全文 | 15814篇 |
免费 | 57篇 |
国内免费 | 10篇 |
专业分类
教育 | 12127篇 |
科学研究 | 1434篇 |
各国文化 | 43篇 |
体育 | 729篇 |
综合类 | 3篇 |
文化理论 | 431篇 |
信息传播 | 1114篇 |
出版年
2022年 | 23篇 |
2021年 | 43篇 |
2020年 | 59篇 |
2019年 | 114篇 |
2018年 | 2288篇 |
2017年 | 2201篇 |
2016年 | 1690篇 |
2015年 | 201篇 |
2014年 | 227篇 |
2013年 | 1002篇 |
2012年 | 339篇 |
2011年 | 806篇 |
2010年 | 962篇 |
2009年 | 550篇 |
2008年 | 769篇 |
2007年 | 1270篇 |
2006年 | 173篇 |
2005年 | 480篇 |
2004年 | 534篇 |
2003年 | 433篇 |
2002年 | 220篇 |
2001年 | 70篇 |
2000年 | 126篇 |
1999年 | 74篇 |
1998年 | 74篇 |
1997年 | 77篇 |
1996年 | 73篇 |
1995年 | 57篇 |
1994年 | 67篇 |
1993年 | 63篇 |
1992年 | 49篇 |
1991年 | 75篇 |
1990年 | 51篇 |
1989年 | 44篇 |
1988年 | 36篇 |
1987年 | 45篇 |
1986年 | 44篇 |
1985年 | 42篇 |
1984年 | 47篇 |
1983年 | 37篇 |
1982年 | 31篇 |
1981年 | 33篇 |
1980年 | 29篇 |
1979年 | 22篇 |
1978年 | 29篇 |
1977年 | 36篇 |
1976年 | 28篇 |
1975年 | 20篇 |
1974年 | 22篇 |
1971年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
1.
David Kaldewey 《Minerva》2018,56(2):161-182
This article analyzes the concept of “grand challenges” as part of a shift in how scientists and policymakers frame and communicate their respective agendas. The history of the grand challenges discourse helps to understand how identity work in science and science policy has been transformed in recent decades. Furthermore, the question is raised whether this discourse is only an indicator, or also a factor in this transformation. Building on conceptual history and historical semantics, the two parts of the article reconstruct two discursive shifts. First, the observation that in scientific communication references to “problems” are increasingly substituted by references to “challenges” indicates a broader cultural trend of how attitudes towards what is problematic have shifted in the last decades. Second, as the grand challenges discourse is rooted in the sphere of sports and competition, it introduces a specific new set of societal values and practices into the spheres of science and technology. The article concludes that this process can be characterized as the sportification of science, which contributes to self-mobilization and, ultimately, to self-optimization of the participating scientists, engineers, and policymakers. 相似文献
2.
3.
4.
5.
6.
7.
Anthony J. Sadar 《Science & Education》2018,27(1-2):233-235
8.
9.
Measuring Search Engine Quality 总被引:12,自引:3,他引:9
The effectiveness of twenty public search engines is evaluated using TREC-inspired methods and a set of 54 queries taken from real Web search logs. The World Wide Web is taken as the test collection and a combination of crawler and text retrieval system is evaluated. The engines are compared on a range of measures derivable from binary relevance judgments of the first seven live results returned. Statistical testing reveals a significant difference between engines and high intercorrelations between measures. Surprisingly, given the dynamic nature of the Web and the time elapsed, there is also a high correlation between results of this study and a previous study by Gordon and Pathak. For nearly all engines, there is a gradual decline in precision at increasing cutoff after some initial fluctuation. Performance of the engines as a group is found to be inferior to the group of participants in the TREC-8 Large Web task, although the best engines approach the median of those systems. Shortcomings of current Web search evaluation methodology are identified and recommendations are made for future improvements. In particular, the present study and its predecessors deal with queries which are assumed to derive from a need to find a selection of documents relevant to a topic. By contrast, real Web search reflects a range of other information need types which require different judging and different measures. 相似文献
10.