全文获取类型
收费全文 | 2336篇 |
免费 | 91篇 |
国内免费 | 4篇 |
学科分类
工业技术 | 2431篇 |
出版年
2023年 | 10篇 |
2022年 | 29篇 |
2021年 | 46篇 |
2020年 | 30篇 |
2019年 | 25篇 |
2018年 | 37篇 |
2017年 | 45篇 |
2016年 | 54篇 |
2015年 | 47篇 |
2014年 | 65篇 |
2013年 | 162篇 |
2012年 | 110篇 |
2011年 | 126篇 |
2010年 | 112篇 |
2009年 | 140篇 |
2008年 | 127篇 |
2007年 | 131篇 |
2006年 | 77篇 |
2005年 | 74篇 |
2004年 | 75篇 |
2003年 | 59篇 |
2002年 | 58篇 |
2001年 | 45篇 |
2000年 | 42篇 |
1999年 | 54篇 |
1998年 | 103篇 |
1997年 | 93篇 |
1996年 | 53篇 |
1995年 | 43篇 |
1994年 | 39篇 |
1993年 | 38篇 |
1992年 | 28篇 |
1991年 | 29篇 |
1990年 | 38篇 |
1989年 | 25篇 |
1988年 | 34篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 20篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 3篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1973年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有2431条查询结果,搜索用时 0 毫秒
111.
We study the problem of disseminating data of time-constrained services through multiple broadcast channels. By time-constrained services, we mean those services whose data must reach clients before a certain constrained time. Otherwise, the data would become useless or substantially less valuable to the clients. We first explore the difficulties of solving the problem and derive the theoretical minimum number of channels required for the task. Then, we propose a transformation-based data allocation (TDA) algorithm that guarantees to fulfill the task (i.e., all requested data reach the clients within the constrained time) by using the minimum number of channels. Finally, we analyze the computation complexity and prove the validity and optimality of the TDA algorithm. 相似文献
112.
Ming-Hui Chen Chien-Shun Chiou Yu-Cheng Chiang Pin-Hsin Chen Shuo-Wen Tsai Hau-Yang Tsen 《Food research international (Ottawa, Ont.)》2012,45(2):978-983
Salmonella Schwarzengrund is one of the frequent serovars isolated from chicken meat in Taiwan. This organism is also one of the invasive Salmonella serovars which may cause human salmonellosis and animal infections. In this study, a total of 466 strains of S. Schwarzengrund including 232 retail chicken meat isolates and 234 human isolates in Taiwan were analyzed for their antibiotic resistance and pulsed field gel electrophoresis (PFGE) patterns. For XbaI-digested DNA, a total of 110 PFGE patterns were obtained. When patterns from both origins were analyzed, of these patterns, 21 were shared by isolates from chicken meat samples and humans. In these 21 patterns, 153 (32.8%) isolates from both origins shared the top five patterns. Since ACSSXTT R-type strains are the major concern worldwide and they accounted for 74.5% of total strains used in this study, such R-type strains in the top five XbaI-digested patterns were then further analyzed with AvrII digestion followed by PFGE and PCR assay targeted to 10 Salmonella virulence genes, i.e., avrA, ssaQ, mgtC, siiD, sopB, gipA, sodC1, sopE1, spvC, and bcfC. When PFGE patterns and virulence gene profiles were combined for the analysis of ACSSXTT R-type strains of S. Schwarzengrund, 29 strains from both origins showed the same pattern combinations. Such results suggested the possible transmission of S. Schwarzengrund from chicken meat to humans. 相似文献
113.
Chun-Che Huang Wen-Yau Liang Tzu-Liang Tseng Hui-Yi Chiang 《Expert systems with applications》2011,38(3):1980-1992
Patent strategy is the overriding mechanism that helps direct investment, resource allocation, expectations, and policy development within an organization. Much studies of patent, for example, patent classification, patent analysis, patent management, patent strategy planning have been made. Due to the high cost of devoting to the research and development for a new patent application, it is essential for a company to develop the patent portfolio based on analyzing related information for fitting with cost constraint and maximizing the benefit. However, only few research attempts to develop new patents with the consideration of resource allocation, for example, optimizing budget utilization. In addition, the previous studies did not derive significant technologies and induct rules for resource allocation through patent analysis. In some cases, the patent analysis may process qualitative information that is difficult to analyze by standard statistical techniques. The rough set approach, which is suitable for processing qualitative information, is required to induct decision rules to derive critical technologies of patents. In this paper, a systematic approach to analyze existing patent information based on rough set theory with the consideration of resource allocation is developed. A case study is presented to demonstrate the contribution of the proposed approach which assists on decision-making in patent reform or invention with constraint resource. 相似文献
114.
With the growth of competition between nations in our knowledge-based world economy, excellence programs are becoming a national agenda item in developing as well as developed Asian countries. The main purpose of this paper is to compare the goals, funding policies and selection criteria of excellence programs in China, Japan, Korea and Taiwan and to analyze the academic achievement of their top ranked universities in three areas: research output, internationalization, and excellence, by using data from the Shanghai Jiao Tong, QS, and HEEACT rankings. The effectiveness of Taiwan??s ??Development Plan for World Class Universities and Research Centers of Excellence?? was assessed as a case study in the paper via a survey targeting on 138 top administrators from 11 Taiwan??s universities and 30 reviewers. The study found that more funding nations had, the more outputs and outcomes they would gain, for example China. The Taiwan case demonstrates that world-class universities and research centers are needed in Asian nations despite the concerns for inequality which they raise. 相似文献
115.
Feng-Yun Wang Guo-Bin Jung Ay Su Shih-Hung Chan Xiang-Ai Li Yu-Chun Chiang 《Materials Letters》2009,63(11):952-954
A new method is studied for preparing nano-ceria by acid leaching MgO from CeO2−MgO mixed powder made by calcining a gel. The MgO in the mixed powder can be leached completely with acetic acid solution at room temperature, but the CeO2 remains unaffected. The surface area (Sg) of the resulting CeO2 increases with Mg/Ce ratio, but approaches constant after the ratio is larger than a given value which is higher for the higher gel calcining temperature. When Mg/Ce is 8 (molar ratio) and the calcining temperature is 1253 K, the Sg of the resulting ceria remains 25.1 m2/g even after annealed at 1253 K for 4 h. In comparison with the conventional methods, CeO2 from the new method shows higher surface area and higher thermal stability. 相似文献
116.
Yunqi Liu Ho Wai Lee Kin Seng Chiang Tao Zhu Yun Jiang Rao 《Lightwave Technology, Journal of》2009,27(7):857-863
We investigate in detail the process of CO2-laser writing of long-period fiber gratings (LPFGs) in unannealed and annealed boron-doped fiber samples by using repeated scanning of CO2-laser pulses. We find that the writing dynamics depends strongly on the CO2-laser energy density and the annealing temperature of the fiber. Our results from analyzing the writing dynamics reveal the relative importance of various physical effects arising from glass structure changes due to different writing conditions and thus provide a better understanding of the formation and the properties of CO2-laser written LPFGs. 相似文献
117.
长期保存(LTP)是一个极具吸引力的新研究领域,其目标是使档案的持续性能保持一段可预见的足够时间。然而这项研究一开始就遭遇了诸多挑战,比如归档时框架、正规方法和工作流模型的缺失,进一步的亏损无法保持档案间的互操作性,以及无信息衰减迹象的信息丢失等。本研究旨在探究各类文件的LTP如何不受时间演变、技术、数字环境变化的影响。基本需求源于存储管理与信息管理的整合,以及数据、元数据、索引等的安全保存。
本文介绍了政府档案管理和知识管理LTP流程有关上述需求的演变发展。资源的有效搜索、数据的有效存储/访问、一致的用户界面、共置备份的恢复图、以及认证和安全管理的动态调整构成随后的任务。接着,论文详细阐述了示范语义数据网格及其注解和服务配套机制,这当中本体起到关键作用。最后,论文总结了习得经验,以及有关LTP语义网格的未来工作。 相似文献
118.
In this paper, two mutation-based evolving artificial neural networks, which are based on the Fuzzy ARTMAP (FAM) network and
evolutionary programming, are proposed. The networks utilize the knowledge base extracted from a set of data to perform search
and adaptation. The performances of the two networks are assessed using benchmark problems, with the results analyzed and
discussed. The effects of the network parameters are evaluated through a parametric study. The applicability of the networks
is also demonstrated using a real fault detection and diagnosis task in a power generation plant. The experimental results
consistently indicate the usefulness of the proposed evolutionary FAM-based networks in yielding good classification performances
with parsimonious network structures. 相似文献
119.
Empathy is an essential part of normal social function that people with autism spectrum conditions (ASCs) lack. This study uses the intervention of enhancing empathy via 3D animated scenarios of empathy in a virtual learning environment to help those deficient in empathy. Specifically, this study explores the understanding of empathy, perspective-taking and the performance of understanding of empathy via a collaborative virtual learning environment (CVLE) - empathy system. The study, which used CVLE - 3D empathy systems and three participants diagnosed with ASCs, conducted multiple baseline research for evidence of improved understanding of empathy via system usage. This experimental study lasted 5 months and the experimental results indicate that using the CVLE 3D empathy system had significant and positive effects on participant use of empathy, both within the CVLE 3D empathy system and in terms of maintaining learning in understanding empathy. 相似文献
120.
A new framework of non-local model for the strain energy density is proposed in this paper. The global strain energy density of the representative volume element is treated as a non-local variable and can be obtained through a special integral of the local strain energy density. The local strain energy density is assumed to be dependent on both the strain and the rotation-gradient. As a result of the non-local model, a new strain gradient theory is derived directly, in which the first and second strain gradients, as well as the triadic and tetradic stress, are introduced in the context of work conjugate. For power law hardening materials, size effects in thin metallic wire torsion and ultra-thin cantilever beam bend are investigated. It is found that the result predicted by the theoretical model is well consistent with the experimental data for the thin wire torsion. On the other hand, the calculation result for the micro-cantilever beam bend clearly shows the size effect. 相似文献