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   3837篇
  免费   322篇
  国内免费   317篇
电工技术   59篇
综合类   667篇
化学工业   139篇
金属工艺   37篇
机械仪表   131篇
建筑科学   1000篇
矿业工程   84篇
能源动力   65篇
轻工业   103篇
水利工程   105篇
石油天然气   58篇
武器工业   23篇
无线电   167篇
一般工业技术   289篇
冶金工业   235篇
原子能技术   28篇
自动化技术   1286篇
  2023年   29篇
  2022年   55篇
  2021年   62篇
  2020年   82篇
  2019年   63篇
  2018年   60篇
  2017年   55篇
  2016年   89篇
  2015年   113篇
  2014年   273篇
  2013年   217篇
  2012年   286篇
  2011年   304篇
  2010年   320篇
  2009年   345篇
  2008年   306篇
  2007年   336篇
  2006年   304篇
  2005年   226篇
  2004年   189篇
  2003年   129篇
  2002年   122篇
  2001年   89篇
  2000年   74篇
  1999年   65篇
  1998年   30篇
  1997年   40篇
  1996年   18篇
  1995年   21篇
  1994年   15篇
  1993年   20篇
  1992年   12篇
  1991年   12篇
  1990年   7篇
  1989年   13篇
  1988年   10篇
  1987年   4篇
  1986年   7篇
  1985年   6篇
  1975年   4篇
  1968年   3篇
  1966年   3篇
  1965年   5篇
  1964年   7篇
  1963年   4篇
  1962年   3篇
  1961年   7篇
  1960年   4篇
  1956年   5篇
  1955年   7篇
排序方式: 共有4476条查询结果,搜索用时 250 毫秒
1.
以“创新、协调、绿色、开放、共享”为内核的新发展理念,是对马克思主义发展理念的继承和发扬,极具时代精神,富含问题意识,为高校思想政治教育发展、教育教学改革实践提供了强大的理论支撑。本文以“通信原理”为例,阐述了新发展理念在课程改革中的思路和方法,实现了思想政治教育与专业基础课程有机融合,为深化高校教学改革、创新人才培养模式提供了思路。  相似文献   
2.
日益严峻的水问题使水安全成为近年来的研究热点之一,但对于目前水安全概念内涵和评价指标的认识尚不统一,给水安全评价和风险管控带来困难。在系统梳理有关研究成果的基础上,以问题为导向,基于水安全机理和"经济社会-水"复合系统视角,提出了水安全的概念内涵,构建了相应的评价指标体系,为我国水安全评估和监测预警提供了理论依据。  相似文献   
3.
尹玉  詹永照  姜震 《计算机应用》2019,39(8):2204-2209
在视频语义检测中,有标记样本不足会严重影响检测的性能,而且伪标签样本中的噪声也会导致集成学习基分类器性能提升不足。为此,提出一种伪标签置信选择的半监督集成学习算法。首先,在三个不同的特征空间上训练出三个基分类器,得到基分类器的标签矢量;然后,引入加权融合样本所属某个类别的最大概率与次大概率的误差和样本所属某个类别的最大概率与样本所属其他各类别的平均概率的误差,作为基分类器的标签置信度,并融合标签矢量和标签置信度得到样本的伪标签和集成置信度;接着,选择集成置信度高的样本加入到有标签的样本集,迭代训练基分类器;最后,采用训练好的基分类器集成协作检测视频语义概念。该算法在实验数据集UCF11上的平均准确率到达了83.48%,与Co-KNN-SVM算法相比,平均准确率提高了3.48个百分点。该算法选择的伪标签能体现样本所属类别与其他类别的总体差异性,又能体现所属类别的唯一性,可减少利用伪标签样本的风险,有效提高视频语义概念检测的准确率。  相似文献   
4.
Customer-involved design concept evaluation (DCE) allows customers to take part in evaluating the design alternatives to get more popular design concept. Traditional customer-involved DCE methods still focus on the collection of customer responses and only consider cost and benefit characteristics of design criteria in multi-criteria decision-making (MCDM) based evaluation process. Few studies have customized the decision-making algorithms specifically aimed at customers’ preferences. This paper further explores the customers’ influences in the early stages of the product design development, and proposes a new rough number based MCDM model (i.e., VIKOR) incorporating customers’ preferences for design specifications along with designers’ perceptions for the characteristics of design criteria (cost and benefit) to perform concept evaluation under subjective environment, and this proposed method is named as integrated rough VIKOR (IR-VIKOR). The objective of this study is to identify the best design concept which maximizes the satisfactions of expectations from most customers as well as conforms to the characteristics of design criteria. Firstly, Shannon entropy is used to obtain the weightings and relative importance ratings of design criteria from the customers’ preferences. Secondly, the customers’ preferences for design attribute values, the importance ratings of design criteria and the characteristics of design criteria are combined together to define the ideal solutions to calculate the rough evaluation index of each design alternative in IR-VIKOR, and finally the ranking result is provided by IR-VIKOR to determine the best design concept. A practical design example is introduced to illustrate the evaluation process of this proposed method, and the empirical comparisons are further carried out to validate its superiority for DCE. Through the sensitivity analysis experiments including i) inside IR-VIKOR, and ii) between IR-VIKOR and other classical MCDM methods, the proposed method is proved to be a reliable and feasible customer-involved DCE approach.  相似文献   
5.
6.
The goal of this study was to enhance the absorption of a new water-insoluble antitumor lead compound, T-OA (3β-hydroxyolea-12-en-28-oic acid-3, 5, 6-trimethylpyrazin-2-methyl ester). Early-stage preparation discovery concept (EPDC) was employed in this study. Based on this concept, a microemulsion system was chosen as the method of improving bioavailability. The solubility of T-OA was checked in different oils, surfactants and cosurfactants. Ternary phase diagrams were constructed to evaluate the microemulsion domain. Developed high-performance liquid chromatography method was used to determine drug content. The transparent o/w microemulsion formulation composed of oleic acid (oil), Tween 80 (surfactant), ethanol (co-surfactant) and water enhanced the solubility of T-OA up to 20?mg/mL. It was characterized in terms of appearance, content, viscosity, zeta potential, conductivity, morphology and particle size. The particle size distribution, viscosity, conductivity and zeta potential were found to be 70?nm, 15.57?MPa?s, 44.1?μS?cm?1 and ?0.174, respectively. Oral bioavailability of T-OA microemulsion and oleic acid solution were checked by using rat model. Contrast to the solid dispersion and proto drug, the area-under-the-curve (AUC) of T-OA microemulsion and oleic acid solution were significantly enhanced. The relative bioavailability of T-OA microemulsion was found to be 5654.7%, which is 57-fold higher than the pure drug. Improved T-OA solubility in microemulsion was found sustained 48?h in dilution study. While the solid dispersion may precipitate under the gastrointestinal circumstance based on dilution results. The in-vivo and in-vitro results indicated that, compare to improve the solubility, it is more important to maintain and prolong the T-OA dissolved status, for improvement of the in-vivo absorption.  相似文献   
7.
This research examined the male and female novice designers toward color associations for the concepts used for ‘warnings’, ‘action required’, and ‘signs and equipment status’ through a questionnaire‐based study. A total of 178 Hong Kong Chinese final year undergraduate design students (89 males and 89 females) participated in the study. The test used required the participants to indicate their choice of one of nine colors to associations with each of 38 concepts in a color‐concept table, so that any one color could be associated with any one of the concepts. For both male and female groups of novice designers, chi‐square tests revealed a strong color association for each concept tested in this study (< .05). The results showed males and females agreed on some color‐concept association stereotypes which were therefore gender neutral. The male and female novice designers had the same color associations and similar levels of stereotype strengths for 21 concepts. The nine strongest and therefore most useful color‐concept association stereotypes for both male and female novice designers were: red‐danger, red‐fire, red‐hot, red‐stop, red‐emergency, red‐error, blue‐cold, blue‐male, and green‐exit. However, the male and female novice designers had different color association stereotypes for the standby (green vs. yellow), emergency exit (green vs. red), and toxic (purple vs. black) concepts, and the strengths of the 14 remaining associations for both groups were not at equivalent levels. Overall, it is anticipated that the findings of this study will act as a useful reference for novice designers and other design practitioners to optimize color coding in the design of ‘warnings’, ‘action required’, and ‘signs and equipment status’ messages.  相似文献   
8.
文章将对中国皮革工业的发展历程与现在基本的环境状况作出详尽的介绍与分析,提出必须以科学发展观为指导,加大力度深入探讨皮革工业的环境建设,并且积极的树立健康良好的皮革工业环境建设观念,以此来促进皮革工业健康可持续的发展。  相似文献   
9.
时装走秀可以更好地展现服装设计理念,提升设计师情感表达的灵活性、多样性,将作品包含的情感展现给受众。在进行情感表达的过程中,需要充分考虑不同情感表现的类型、特征,有针对性地进行设计,还需要充分了解设计要点、表达特征,深入理解设计师想要表达的情感。  相似文献   
10.
The rapid growth of data and the requirement of designers to track massive data to obtain design stimuli have posed challenges to conceptual design, thereby promoting the development of data-driven design. Concept networks precisely capture design information from a large volume of unstructured and heterogeneous textual data and saliently decrease time and labor cost for designers to read texts, which creates new opportunities for developing a smart product design system. To advance data-driven design, this study proposes the novel function-structure concept network (FSCN) construction method, which combines sentence parsing and word/phrase extraction to integrate functional and structural information. Furthermore, a network analysis method is proposed to explore design information associations that contain both explicit and implicit associations together and thereby recommend them simultaneously to designers as inspirational stimuli to support design ideation. This approach can enhance designers' capabilities to build associations between design information, conceive new design ideas during conceptual design, and increase creativity for solving design problems. The proposed FSCN construction and analysis method can be used as an auxiliary tool to visualize associations among design information so as to inspire idea generation in the early stage of conceptual design. An illustrative example was used to validate the practicability of the proposed methodology. The code of the proposed method is available at https://github.com/KWflyer/FSCN.  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