全文获取类型
收费全文 | 4409篇 |
免费 | 52篇 |
国内免费 | 6篇 |
专业分类
教育 | 2921篇 |
科学研究 | 501篇 |
各国文化 | 20篇 |
体育 | 361篇 |
综合类 | 8篇 |
文化理论 | 58篇 |
信息传播 | 598篇 |
出版年
2023年 | 24篇 |
2022年 | 30篇 |
2021年 | 39篇 |
2020年 | 77篇 |
2019年 | 107篇 |
2018年 | 202篇 |
2017年 | 223篇 |
2016年 | 198篇 |
2015年 | 124篇 |
2014年 | 161篇 |
2013年 | 729篇 |
2012年 | 140篇 |
2011年 | 157篇 |
2010年 | 154篇 |
2009年 | 107篇 |
2008年 | 99篇 |
2007年 | 130篇 |
2006年 | 80篇 |
2005年 | 85篇 |
2004年 | 81篇 |
2003年 | 69篇 |
2002年 | 56篇 |
2001年 | 99篇 |
2000年 | 88篇 |
1999年 | 73篇 |
1998年 | 57篇 |
1997年 | 46篇 |
1996年 | 55篇 |
1995年 | 29篇 |
1994年 | 36篇 |
1993年 | 24篇 |
1992年 | 49篇 |
1991年 | 48篇 |
1990年 | 29篇 |
1989年 | 40篇 |
1988年 | 35篇 |
1987年 | 32篇 |
1986年 | 36篇 |
1985年 | 42篇 |
1984年 | 37篇 |
1983年 | 23篇 |
1982年 | 35篇 |
1981年 | 24篇 |
1980年 | 17篇 |
1979年 | 35篇 |
1978年 | 29篇 |
1977年 | 23篇 |
1974年 | 24篇 |
1972年 | 26篇 |
1971年 | 18篇 |
排序方式: 共有4467条查询结果,搜索用时 46 毫秒
31.
32.
33.
In Information Retrieval, since it is hard to identify users’ information needs, many approaches have been tried to solve
this problem by expanding initial queries and reweighting the terms in the expanded queries using users’ relevance judgments.
Although relevance feedback is most effective when relevance information about retrieved documents is provided by users, it
is not always available. Another solution is to use correlated terms for query expansion. The main problem with this approach
is how to construct the term-term correlations that can be used effectively to improve retrieval performance. In this study,
we try to construct query concepts that denote users’ information needs from a document space, rather than to reformulate initial queries using the term correlations
and/or users’ relevance feedback. To form query concepts, we extract features from each document, and then cluster the features into primitive concepts that are then used to form
query concepts. Experiments are performed on the Associated Press (AP) dataset taken from the TREC collection. The experimental evaluation
shows that our proposed framework called QCM (Query Concept Method) outperforms baseline probabilistic retrieval model on
TREC retrieval. 相似文献
34.
Tuomo Korenius Jorma Laurikkala Martti Juhola Kalervo Järvelin 《Information Retrieval》2006,9(1):33-53
Search facilitated with agglomerative hierarchical clustering methods was studied in a collection of Finnish newspaper articles
(N = 53,893). To allow quick experiments, clustering was applied to a sample (N = 5,000) that was reduced with principal components analysis. The dendrograms were heuristically cut to find an optimal partition,
whose clusters were compared with each of the 30 queries to retrieve the best-matching cluster. The four-level relevance assessment
was collapsed into a binary one by (A) considering all the relevant and (B) only the highly relevant documents relevant, respectively.
Single linkage (SL) was the worst method. It created many tiny clusters, and, consequently, searches enabled with it had high
precision and low recall. The complete linkage (CL), average linkage (AL), and Ward's methods (WM) returned reasonably-sized
clusters typically of 18–32 documents. Their recall (A: 27–52%, B: 50–82%) and precision (A: 83–90%, B: 18–21%) was higher
than and comparable to those of the SL clusters, respectively. The AL and WM clustering had 1–8% better effectiveness than
nearest neighbor searching (NN), and SL and CL were 1–9% less efficient that NN. However, the differences were statistically
insignificant. When evaluated with the liberal assessment A, the results suggest that the AL and WM clustering offer better
retrieval ability than NN. Assessment B renders the AL and WM clustering better than NN, when recall is considered more important
than precision. The results imply that collections in the highly inflectional and agglutinative languages, such as Finnish,
may be clustered as the collections in English, provided that documents are appropriately preprocessed. 相似文献
35.
36.
Bast fibres have been commonly used as a textile material in Northern Europe since Neolithic times. However, the process of identifying the different species has been problematic, and many important questions related to their cultural history are still unanswered. For example, a modified Herzog test and the presence of calcium oxalate crystals have both been used in identification. In order to generate more reliable results, further research and advancement in multi-methodological methods is required. This paper introduces a combination of methods which can be used to identify and distinguish flax (Linum usitatissimum), hemp (Cannabis sativa), and stinging nettle (Urtica dioica). The research material consisted of reference fibres and 25 fibre samples obtained from 12 textiles assumed to be made of nettle. The textiles were from the Finno-Ugric and Historical Collections of The National Museum of Finland. The fibre samples were studied by observing the surface characteristics and cross sections with transmitted light microscopy, and by using a modified Herzog test with polarized light, in order to identify the distinguishable features in their morphological structures. The study showed that five out of 25 samples were cotton, 16 nettle, one flax, and one hemp. Findings from two samples were inconsistent. The results show that it is possible to distinguish common north European bast fibres from each other by using a combination of microscopic methods. Furthermore, by utilizing these combined methods, new and more reliable information could be obtained from historical ethnographic textiles, which creates new vistas for the interpretation of their cultural history. 相似文献
37.
I. V. Zibareva L. Yu. Ilina B. L. Alperin 《Scientific and Technical Information Processing》2018,45(2):106-109
The current state of the Russian Science Citation Index is analyzed. Several areas for its further development identified by long-standing active users, such as data searching, refinement, and storage; current user alerts; data input with the Science Index license; patent information; and the application programming interface (API) are investigated. 相似文献
38.
The present research investigated whether co-viewer comments in social TV interactions are able to enhance or weaken media effects. With the example of talent shows, the valence of co-viewer comments (pro/contra/none) as well as the type of content (antisocial behavior vs. conventional performance) were varied in an experiment (N = 117). Results showed that participants’ own comments and their private attitudes about the judges varied in line with comment valence. Findings suggest that social TV viewers are prone to social influence of their co-viewers, which might amplify problems regarding the portrayal of antisocial behavior in reality TV. 相似文献
39.
40.