全文获取类型
收费全文 | 17599篇 |
免费 | 258篇 |
国内免费 | 54篇 |
专业分类
教育 | 13081篇 |
科学研究 | 1181篇 |
各国文化 | 174篇 |
体育 | 1294篇 |
综合类 | 44篇 |
文化理论 | 93篇 |
信息传播 | 2044篇 |
出版年
2022年 | 103篇 |
2021年 | 199篇 |
2020年 | 260篇 |
2019年 | 398篇 |
2018年 | 583篇 |
2017年 | 601篇 |
2016年 | 553篇 |
2015年 | 352篇 |
2014年 | 510篇 |
2013年 | 3526篇 |
2012年 | 467篇 |
2011年 | 477篇 |
2010年 | 445篇 |
2009年 | 424篇 |
2008年 | 443篇 |
2007年 | 410篇 |
2006年 | 428篇 |
2005年 | 372篇 |
2004年 | 272篇 |
2003年 | 253篇 |
2002年 | 231篇 |
2001年 | 378篇 |
2000年 | 303篇 |
1999年 | 262篇 |
1998年 | 161篇 |
1997年 | 159篇 |
1996年 | 171篇 |
1995年 | 145篇 |
1994年 | 154篇 |
1993年 | 139篇 |
1992年 | 214篇 |
1991年 | 212篇 |
1990年 | 235篇 |
1989年 | 216篇 |
1988年 | 177篇 |
1987年 | 184篇 |
1986年 | 189篇 |
1985年 | 178篇 |
1984年 | 179篇 |
1983年 | 169篇 |
1982年 | 137篇 |
1981年 | 140篇 |
1980年 | 133篇 |
1979年 | 193篇 |
1978年 | 164篇 |
1977年 | 114篇 |
1976年 | 121篇 |
1975年 | 117篇 |
1973年 | 106篇 |
1971年 | 116篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
71.
介绍国外权威文献传递服务机构 总被引:4,自引:0,他引:4
目前网上文献传递服务在各大图书馆和情报机构都有一定的发展。本文主要从文献传递的特点、文献收藏、服务情况、服务周期、服务对象和服务费用等方面对国外几家较著名的网上文献情报机构进行介绍,以期对我们的文献传递服务工作提供帮助和参考。 相似文献
72.
Jennifer R. Warren Michael L. Hecht David A. Wagstaff Elvira Elek Khadidiatou Ndiaye Patricia Dustman Flavio F. Marsiglia 《Journal of Applied Communication Research》2006,34(2):209-227
This study sought to determine if exposure to two communication-oriented activities, videotapes and public service announcements, accounts for changes in substance use among adolescents participating in the Drug Resistance Strategies Project's keepin' it REAL adolescent substance use prevention curriculum. Middle-school students (4,734, 72% Latino) responded to questionnaires related to these analyses. An analysis of covariance (ANCOVA) model was fit separately to six substance use outcomes. The results suggested that intervention students who saw four or five videos engaged in less substance use in the past month than did students who saw fewer videos. Having seen the PSAs one or more times did not predict the reported change in substance use. 相似文献
73.
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
74.
75.
Sandra L De Groote Marceline Doranski 《Journal of the Medical Library Association》2004,92(3):341-348
OBJECTIVES: The purpose of this study is to determine how personal digital assistants (PDAs) are used on an academic health sciences campus to define the level of training and support the library can provide to the students and faculty. METHOD: A Web-based questionnaire was developed. A total of 1,538 health sciences faculty and residents were sent an email message requesting participation. Data from the returned surveys were analyzed with SPSS. RESULTS: Sixty-one percent of survey respondents used PDAs. The address book, date book, and calculator were the most common uses reported for PDAs. Residents also reported a high use of drug databases on their PDAs. Most survey respondents indicated they would like to learn more about clinical resources for PDAs. CONCLUSIONS: Many opportunities exist for librarians to provide training and support for PDAs, in addition to evaluation and promotion of clinical software for PDAs. 相似文献
76.
77.
Barbara L. Craig 《Archival Science》2005,5(2-4):391-402
The author, a professor at the University of Toronto, touches briefly on the extensive and rich archival literature that supports
the teaching of macroappraisal, but notes that this is not the only educational material she offers her students when teaching
appraisal theory. She discusses the usefulness to archivists of literature from the fields of ethnography, organizational
knowing, records in history, personal documentary behaviour, memory, and communications, noting that the use of texts from
these fields can encourage students to reflect on their own presumptions and to develop a taste for the wide reading and research
that must support appraisal. 相似文献
78.
Sandra L De Groote Mary Shultz Marceline Doranski 《Journal of the Medical Library Association》2005,93(2):223-228
PURPOSE: The purpose was to determine the impact of online journals on the citation patterns of medical faculty. This study looked at whether researchers were more likely to limit the resources they consulted and cited to those journals available online rather than those only in print. SETTING: Faculty publications from the college of medicine at a large urban university were examined for this study. The faculty publications from a regional medical college of the same university were also examined in the study. The number of online journals available for faculty, staff, and students at this institution has increased from an initial core of 15 online journals in 1998 to over 11,000 online journals in 2004. METHODOLOGY: Searches by author affiliation were performed in the Web of Science to find all articles written by faculty members in the college of medicine at the selected institution. Searches were conducted for the following years: 1993, 1996, 1999, and 2002. Cited references from each faculty-authored article were recorded, and the corresponding cited journals were coded into four categories based on their availability at the institution in this study: print only, print and online, online only, and not owned. Results were analyzed using SPSS. RESULTS: The number of journals cited per year continued to increase from 1993 to 2002. The results did not indicate that researchers were more likely to cite online journals or were less likely to cite journals only in print. At the regional location where the number of print-only journals was minimal, use of the print-only journals did decrease in 2002, although not significantly. CONCLUSION/DISCUSSION: It is possible that electronic access to information (i.e., online databases) has had a positive impact on the number of articles faculty will cite. Results of this study suggest, at this point, that faculty are still accessing the print-only collection, at least for research purposes, and are therefore not sacrificing quality for convenience. 相似文献
79.
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
80.
Previous studies have shown that weeding a library collection benefits patrons and increases circulation rates. However, the time required to review the collection and make weeding decisions presents a formidable obstacle. This study empirically evaluated methods for automatically classifying weeding candidates. A data set containing 80,346 items from a large-scale weeding project running from 2011 to 2014 at Wesleyan University was used to train six machine learning classifiers to predict a weeding decision of either ‘Keep’ or ‘Weed’ for each candidate. The study found statistically significant agreement (p?=?0.001) between classifier predictions and librarian judgments for all classifier types. The naive Bayes and linear support vector machine classifiers had the highest recall (fraction of items weeded by librarians that were identified by the algorithm), while the k-nearest-neighbor classifier had the highest precision (fraction of recommended candidates that librarians had chosen to weed). The variables found to be most relevant were: librarian and faculty votes for retention, item age, and the presence of copies in other libraries. 相似文献