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981.
In this paper the problem of indexing heterogeneous structured documents and of retrieving semi-structured documents is considered. We propose a flexible paradigm for both indexing such documents and formulating user queries specifying soft constraints on both documents structure and content. At the indexing level we propose a model that achieves flexibility by constructing personalised document representations based on users views of the documents. This is obtained by allowing users to specify their preferences on the documents sections that they estimate to bear the most interesting information, as well as to linguistically quantify the number of sections which determine the global potential interest of the documents. At the query language level, a flexible query language for expressing soft selection conditions on both the documents structure and content is proposed. 相似文献
982.
TIJAH: Embracing IR Methods in XML Databases 总被引:1,自引:0,他引:1
Johan?ListEmail author Vojkan?Mihajlovi? Georgina?Ramírez Arjen?P.?de?Vries Djoerd?Hiemstra Henk?Ernst?Blok 《Information Retrieval》2005,8(4):547-570
This paper discusses our participation in INEX (the Initiative for the Evaluation of XML Retrieval) using the TIJAH XML-IR system. TIJAHs system design follows a standard layered database architecture, carefully separating the conceptual, logical and physical levels. At the conceptual level, we classify the INEX XPath-based query expressions into three different query patterns. For each pattern, we present its mapping into a query execution strategy. The logical layer exploits score region algebra (SRA) as the basis for query processing. We discuss the region operators used to select and manipulate XML document components. The logical algebra expressions are mapped into efficient relational algebra expressions over a physical representation of the XML document collection using the pre-post numbering scheme. The paper concludes with an analysis of experiments performed with the INEX test collection. 相似文献
983.
Learning to Rank 总被引:1,自引:0,他引:1
New general purpose ranking functions are discovered using genetic programming. The TREC WSJ collection was chosen as a training set. A baseline comparison function was chosen as the best of inner product, probability, cosine, and Okapi BM25. An elitist genetic algorithm with a population size 100 was run 13 times for 100 generations and the best performing algorithms chosen from these. The best learned functions, when evaluated against the best baseline function (BM25), demonstrate some significant performance differences, with improvements in mean average precision as high as 32% observed on one TREC collection not used in training. In no test is BM25 shown to significantly outperform the best learned function. 相似文献
984.
Query languages for XML such as XPath or XQuery support Boolean retrieval: a query result is a (possibly restructured) subset of XML elements or entire documents that satisfy the search conditions of the query. This search paradigm works for highly schematic XML data collections such as electronic catalogs. However, for searching information in open environments such as the Web or intranets of large corporations, ranked retrieval is more appropriate: a query result is a ranked list of XML elements in descending order of (estimated) relevance. Web search engines, which are based on the ranked retrieval paradigm, do, however, not consider the additional information and rich annotations provided by the structure of XML documents and their element names.This article presents the XXL search engine that supports relevance ranking on XML data. XXL is particularly geared for path queries with wildcards that can span multiple XML collections and contain both exact-match as well as semantic-similarity search conditions. In addition, ontological information and suitable index structures are used to improve the search efficiency and effectiveness. XXL is fully implemented as a suite of Java classes and servlets. Experiments in the context of the INEX benchmark demonstrate the efficiency of the XXL search engine and underline its effectiveness for ranked retrieval. 相似文献
985.
Jaap?KampsEmail author Maarten?de?Rijke B?rkur?Sigurbj?rnsson 《Information Retrieval》2005,8(4):631-654
XML retrieval is a departure from standard document retrieval in which each individual XML element, ranging from italicized words or phrases to full blown articles, is a retrievable unit. The distribution of XML element lengths is unlike what we usually observe in standard document collections, prompting us to revisit the issue of document length normalization. We perform a comparative analysis of arbitrary elements versus relevant elements, and show the importance of element length as a parameter for XML retrieval. Within the language modeling framework, we investigate a range of techniques that deal with length either directly or indirectly. We observe a length-bias introduced by the amount of smoothing, and show the importance of extreme length bias for XML retrieval. We also show that simply removing shorter elements from the index (by introducing a cut-off value) does not create an appropriate element length normalization. Even after restricting the minimal size of XML elements occurring in the index, the importance of an extreme explicit length bias remains. 相似文献
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Conclusion Publishers may wish to ignore disabilities legislation since it doesn’t apply directly to them, but their customers will not be able ignore the new laws when making purchasing decisions. Thus, as a practical
matter each publisher must develop a game plan for how it will position itself to remain competitive in a marketplace where
the timely availability of their print works in digital formats is becoming a Sine qua non on purchasing checklists.
How individual publishers choose to tackle the new challenges will be determined by a number of variables including the type
of content they publish (humanities, math, science, technical), the production systems they use, the length of their press
runs, the shelf-life of their products, the level of service they are prepared to provide, the risks they are willing to take,
and the dynamics of the markets they serve.
A publisher’s strategy will need frequent review and modification because the variables involved in the accessibility environment
are changing rapidly. New developments are occurring all the time in the legal environment, in production technologies, in
assistive technologies, in distribution technologies, in digital rights management technologies, as well as in file standards.
Solutions will need frequent tuning.
For publishers, accessibility challenges do not stop with providing alternate formats for printed works. Those delivering
their content over private networks via course management systems and over the Internet find that there are other accessibility
requirements and standards to be met. It will behoove publishers to develop and implement informed operating policies and
protocols that assure that onan ongoing basis its products and services meet applicable accessibility requirements and thus
can fully compete in an increasingly demanding marketplace. 相似文献
990.
Survival strategies for academic publishing 总被引:1,自引:0,他引:1