首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3072篇
  免费   57篇
  国内免费   75篇
化学   27篇
力学   2篇
综合类   33篇
数学   54篇
物理学   78篇
综合类   3010篇
  2024年   1篇
  2023年   5篇
  2022年   1篇
  2021年   6篇
  2020年   8篇
  2019年   14篇
  2018年   3篇
  2017年   13篇
  2016年   14篇
  2015年   39篇
  2014年   77篇
  2013年   75篇
  2012年   142篇
  2011年   196篇
  2010年   228篇
  2009年   268篇
  2008年   274篇
  2007年   334篇
  2006年   367篇
  2005年   257篇
  2004年   246篇
  2003年   185篇
  2002年   138篇
  2001年   113篇
  2000年   77篇
  1999年   45篇
  1998年   20篇
  1997年   13篇
  1996年   5篇
  1995年   4篇
  1994年   7篇
  1993年   4篇
  1992年   2篇
  1991年   5篇
  1990年   3篇
  1989年   5篇
  1988年   2篇
  1987年   4篇
  1982年   1篇
  1981年   1篇
  1980年   2篇
排序方式: 共有3204条查询结果,搜索用时 0 毫秒
101.
基于XML的WEB数据挖掘系统框架的设计与实现   总被引:9,自引:0,他引:9  
互联网的广泛应用使Web数据挖掘成为当前数据挖掘技术研究的热点,而XML正逐渐成为新一代互联网数据组织和交换的事实标准,两者的结合-基于XML的Web数据挖掘技术成为Web数据挖掘中一个重要的研究课题。分析了Web数据挖掘技术的难点,提出了一个基于XML的Web内容数据挖掘系统框架。  相似文献   
102.
Retrieving definitional content for ontology development   总被引:1,自引:0,他引:1  
Ontology construction requires an understanding of the meaning and usage of its encoded concepts. While definitions found in dictionaries or glossaries may be adequate for many concepts, the actual usage in expert writing could be a better source of information for many others. The goal of this paper is to describe an automated procedure for finding definitional content in expert writing. The approach uses machine learning on phrasal features to learn when sentences in a book contain definitional content, as determined by their similarity to glossary definitions provided in the same book. The end result is not a concise definition of a given concept, but for each sentence, a predicted probability that it contains information relevant to a definition. The approach is evaluated automatically for terms with explicit definitions, and manually for terms with no available definition.  相似文献   
103.
SpecPad is a new device‐independent software program for the visualization and processing of one‐dimensional and two‐dimensional nuclear magnetic resonance (NMR) time domain (FID) and frequency domain (spectrum) data. It is the result of a project to investigate whether the novel programming language DART, in combination with Html5 Web technology, forms a suitable base to write an NMR data evaluation software which runs on modern computing devices such as Android, iOS, and Windows tablets as well as on Windows, Linux, and Mac OS X desktop PCs and notebooks. Another topic of interest is whether this technique also effectively supports the required sophisticated graphical and computational algorithms. SpecPad is device‐independent because DART's compiled executable code is JavaScript and can, therefore, be run by the browsers of PCs and tablets. Because of Html5 browser cache technology, SpecPad may be operated off‐line. Network access is only required during data import or export, e.g. via a Cloud service, or for software updates. A professional and easy to use graphical user interface consistent across all hardware platforms supports touch screen features on mobile devices for zooming and panning and for NMR‐related interactive operations such as phasing, integration, peak picking, or atom assignment. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   
104.
Based on high-throughput data, numerous algorithms have been designed to find functions of novel proteins. However, the effectiveness of such algorithms is currently limited by some fundamental factors, including (1) the low a-priori probability of novel proteins participating in a detailed function; (2) the huge false data present in high-throughput datasets; (3) the incomplete data coverage of functional classes; (4) the abundant but heterogeneous negative samples for training the algorithms; and (5) the lack of detailed functional knowledge for training algorithms. Here, for partially characterized proteins, we suggest an approach to finding their finer functions based on protein interaction sub-networks or gene expression patterns, defined in function-specific subspaces. The proposed approach can lessen the above-mentioned problems by properly defining the prediction range and functionally filtering the noisy data, and thus can efficiently find proteins’ novel functions. For thousands of yeast and human proteins partially characterized, it is able to reliably find their finer functions (e.g., the translational functions) with more than 90% precision. The predicted finer functions are highly valuable both for guiding the follow-up wet-lab validation and for providing the necessary data for training algorithms to learn other proteins.  相似文献   
105.
It is well known that the static caching algorithm that keeps the most frequently requested documents in the cache is optimal in case when documents are of the same size and requests are independent and identically distributed. However, it is hard to develop explicit and provably optimal caching algorithms when requests are statistically correlated. In this paper, we show that keeping the most frequently requested documents in the cache is still optimal for large cache sizes even if the requests are strongly correlated.  相似文献   
106.
107.
Web服务在远程报表打印系统中的应用   总被引:2,自引:0,他引:2  
针对目前B/S模式系统中报表开发的难点,提出一种B/S模式系统下基于Web服务的远程报表解决方案.文中给出了系统设计原理,概述了Web服务及其相关技术,最后给出基于Web服务的远程报表打印系统具体实现的关键技术.  相似文献   
108.
基于Web Services分布式原理,提出了一种新的移动通信综合网管系统的方案.该系统与目前国内传统的TMN网管系统相比,在匹配性、移植性、扩展性、安全性以及重用性等方面都具有明显的优越性.通过对Web Services体系结构分析研究,给出了Web Services到TMN网管系统的映射.并在试验环境中,实现和验证了这种基于Web Services分布式综合网管系统.最后对如何用,ETWeb服务来实现综合的网管的关键技术进行了阐述和分析。  相似文献   
109.
Peer production has played an important role in the economics of Web 2.0 related services in which user participation and contribution become the main driving dynamics. However, the quality of peer-produced services is uncertain because of inherently decentralized and heterogeneous participants. In the paper, utilizing reliability and game theoretic models, we develop a QoS measure and pricing schemes for this emerging type of service under various market structures. Our results suggest that a monopolistic platform provider has no incentive to offer multiple quality classes of service. Two competing platform providers may offer identical service contracts but still receive non-negative profit. If they offer heterogeneous service contracts, the provider with the lower quality service may provide higher quality than he advertises. This research contributes to the literature with a number of unique and interesting implications for the issues of service contract design, capacity planning, and market interactions for operations of community-based or peer-produced services.  相似文献   
110.
We describe a model for the evolution of the languages used by the agents of a society. Our main result proves convergence of these languages to a common one under certain conditions. A few special cases are elaborated in more depth.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号