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   2634篇
  免费   130篇
  国内免费   44篇
电工技术   76篇
技术理论   1篇
综合类   181篇
化学工业   328篇
金属工艺   154篇
机械仪表   311篇
建筑科学   365篇
矿业工程   86篇
能源动力   80篇
轻工业   158篇
水利工程   28篇
石油天然气   131篇
武器工业   15篇
无线电   172篇
一般工业技术   126篇
冶金工业   109篇
原子能技术   22篇
自动化技术   465篇
  2024年   2篇
  2023年   20篇
  2022年   26篇
  2021年   65篇
  2020年   58篇
  2019年   23篇
  2018年   34篇
  2017年   48篇
  2016年   76篇
  2015年   94篇
  2014年   137篇
  2013年   163篇
  2012年   149篇
  2011年   168篇
  2010年   135篇
  2009年   124篇
  2008年   103篇
  2007年   161篇
  2006年   149篇
  2005年   134篇
  2004年   123篇
  2003年   103篇
  2002年   108篇
  2001年   85篇
  2000年   62篇
  1999年   72篇
  1998年   69篇
  1997年   66篇
  1996年   42篇
  1995年   46篇
  1994年   34篇
  1993年   27篇
  1992年   20篇
  1991年   13篇
  1990年   13篇
  1989年   13篇
  1988年   8篇
  1987年   3篇
  1986年   6篇
  1985年   5篇
  1984年   7篇
  1983年   1篇
  1982年   2篇
  1981年   2篇
  1979年   3篇
  1978年   1篇
  1976年   1篇
  1975年   2篇
  1957年   1篇
  1955年   1篇
排序方式: 共有2808条查询结果,搜索用时 23 毫秒
1.
Risk allocation decisions are of critical importance in project management. The present study proposes an explanation for how risk allocation in a contract motivates a contractor to cooperate with a project owner. Theories of risk allocation and trust were used to motivate the research. Using a survey methodology, we collected data concerning 124 construction projects in China. We found that risk allocation influenced the contractor’s role behavior through the contractor’s feeling of being trusted but not the contractor’s trust in the owner. Feeling of being trusted partially mediated the effect of risk allocation on the contractor’s in-role (i.e., contractual) behavior and fully mediated the effect on extra-role behavior. The study introduces a social and psychological view of the impacts of risk allocation to the project and engineering management literature. We contribute to theory by arguing and demonstrating the mediating effect of trust on the relationship between risk allocation and contractor behavior. From a practical standpoint, we conclude that contractual risk allocation has a significant impact on building a trusting relationship between owners and contractors and that contractors who feel trusted perform both contractually mandated actions and actions external to the contract more diligently, resulting in the likelihood of improved outcomes for both parties.  相似文献   
2.
《云南化工》2018,(12):114-115
鄂尔多斯盆地白豹-南梁地区延长组长4+5油层段是重要的储集层之一,包括长4+51和长4+52。由于白豹-南梁地区长4+51油气富集规律尚未明确,亦有必要对白豹-南梁地区4+51储层开展评价。通过岩心铸体薄片、物性分析、压汞分析等资料对研究区长4+51储层特征进行了研究。结果表明,研究区岩石类型以长石砂岩和岩屑长石砂岩为主,分选性以中-好为主,磨圆度以次棱角状为主;孔隙类型主要为粒间孔、长石溶孔,孔隙空间分选性较差,喉道分布不集中;研究区整体以Ⅱ类储层分布为主。  相似文献   
3.
Although many app-based textbooks are available for students, reading have not been thoroughly outlined. This study aimed to understand how changes from paper to electronic textbooks have affected the academic reading task, investigate student users’ perceptions of in-app components and screen sizes, and identify issues affecting in-app components and task requirements. A mixed factorial design experiment was employed. Results showed that there were no significant changes in comprehension and time spent reading between print text and the iPad. Yet, student highlighting, notetaking, and reading behavior and perception significantly changed based on condition. In addition, students struggled to use in-app components and found them frustrating especially when accounting for sentence splitting. The findings presented can assist in understanding the changes in student reading behavior, which can be used to improve interface design of future e-textbooks.  相似文献   
4.
吴菁 《福建电脑》2020,(5):41-43
提升教学质量是高职院校人才培养工作的永恒主题。在信息化时代的今天,信息技术的融合为课堂教学的诊断与评估提供了新的视角。本文在弗兰德斯互动分析理论(FIAS)基础上,基于应用软件,对高校师生课堂互动行为进行研究。自动生成合理的分析报告,可为教师提升教学能力提供反思和改进的依据,帮助教师在教学过程中发现问题并及时诊改。  相似文献   
5.
采用Gleeble-3500热模拟试验机对2024A铝合金进行等温热轧,对其高温流变行为进行了研究。通过试验获得2024A铝合金在温度为300~450℃、应变速率为0.01~10s-1时的真应力-真应变曲线。结果表明,2024A铝合金的流变应力与温度、应变速率和变形量之间呈非线性关系,流变应力随着应变速率增大而升高,随着变形温度的升高而降低。基于试验数据,分别建立考虑应变补偿的Arrhenius和修正的Johnson-Cook(M-JC)本构模型,引入统计学方法对模型精度进行量化评估:Arrhenius模型的平均相对误差和均方根误差分别为5.02%和5.88MPa,M-JC模型的平均相对误差和均方根误差分别为3.72%和5.27MPa,可见M-JC模型预测精度优于Arrhenius模型,说明M-JC模型能更为准确地描述2024A铝合金的高温轧制过程中的流变行为。  相似文献   
6.
Water culture is one of the key issues in Water Ecological Civilization. China’s traditional water cultural landscape embodies rich water cultures, and have a significance in related research and protection practice. This paper proposes the concept of “water cultural landscape,” that is, the landscape formed through humans’ environmental alteration during water activities—including how people use, transform, and manage it. The traditional water cultural landscapes in Huizhou Region have developed over hundreds of years, reflecting the locals’ wisdom in sustainable water use. The water cultural landscape in Huizhou Region should be interpreted as a systematic notion, in which all landscape elements such as ponds, weirs, and shuikous are interdependent, composing the landscape components e.g. valleys, hills, and basins, and establishing water security patterns for cities, towns, villages, and for production. The traditional water cultural landscape in Huizhou Region requires local generations’ long-term maintenance and management, and in turn it is also vital to Huizhou people's life and Huizhou culture. Today, it acts as an ecological infrastructure for sponge countryside and sponge city construction, and an important resource for heritage protection and tourism development.  相似文献   
7.
The simulation of Human Centered Systems (HCS) has attracted increasingly attention in recent research. These systems involve individuals playing key roles, such as workers in manufacturing systems, soldiers in military operations, and investors in stock markets. The complexity simulating such systems is due to the need for modeling individual and group behavior and the integration of psychological and socio-technical aspects that can affect individual and HCS global performance. Although several models have been proposed to simulate such systems, most of them suffer from limitations pertaining to the integration of some factors, an inadequacy that will be discussed and elaborated on in this paper. The current study presents a new model for HCS simulation based on recent social and psychological theories. A model implementation example involving the simulation of a manufacturing system, considered as a HCS, is presented.  相似文献   
8.
诸多的化工单元操作过程中,普遍存在着"边界层"现象。"边界层"的存在对化工单元的操作过程会产生明显的影响。本文描述和类比了多种"边界层"的特征,并在物理化学的知识层面上对其产生机理进行了阐述,最后指出通过削弱边界层可以提高动量传递、质量传递和热量传递的速率和效率。  相似文献   
9.
鉴于视觉测量过程行为的多样性与影响关系的复杂性,提出基于行为自适应的台钻主轴视觉测量新策略。采用周向分工位采集图像与轴向分段提取轮廓结合的组合采样法获取被测信息,并建立了主轴轴径视觉测量系统;设计曝光自适应图像采集、图像批处理、误差反馈闭环测量等功能集成的行为自适应视觉测量流程并开发相应软件。以某型号台钻主轴为对象,开展曝光区间自适应优选实验,多工位、多轴、多采样方案测量实验误差分析与稳定性评定。结果表明:所提出的行为自适应测量策略通过获取测量行为变化对测量误差的影响,形成闭环测量,可有效提高测量的稳定性,不仅满足台钻主轴高精度轴段测量需求,还有利于推动测量智能化发展。  相似文献   
10.
采用异丙基黄原酸钠SIP、N-乙基-N-苯基二硫代氨基甲酸PX的复合促进剂体系(用量分别为1.5phhr和0.5phhr)可使天然橡胶/顺丁橡胶并用胶(并用比为70∶30)在90℃~95℃内快速硫化,硫化特性符合缓冲胶工艺的要求,但其性能与HG/T 4124-2009《预硫化缓冲胶》存在一定的差距。  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