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   49122篇
  免费   2755篇
  国内免费   154篇
电工技术   708篇
综合类   65篇
化学工业   10372篇
金属工艺   2135篇
机械仪表   3241篇
建筑科学   1097篇
矿业工程   25篇
能源动力   2111篇
轻工业   3886篇
水利工程   271篇
石油天然气   88篇
武器工业   2篇
无线电   7810篇
一般工业技术   10660篇
冶金工业   3880篇
原子能技术   658篇
自动化技术   5022篇
  2024年   24篇
  2023年   537篇
  2022年   680篇
  2021年   1480篇
  2020年   1069篇
  2019年   1175篇
  2018年   1429篇
  2017年   1411篇
  2016年   1750篇
  2015年   1293篇
  2014年   2088篇
  2013年   3006篇
  2012年   3265篇
  2011年   3889篇
  2010年   2814篇
  2009年   2921篇
  2008年   2811篇
  2007年   2185篇
  2006年   2031篇
  2005年   1723篇
  2004年   1571篇
  2003年   1513篇
  2002年   1329篇
  2001年   1134篇
  2000年   996篇
  1999年   928篇
  1998年   1557篇
  1997年   991篇
  1996年   803篇
  1995年   557篇
  1994年   460篇
  1993年   406篇
  1992年   290篇
  1991年   274篇
  1990年   258篇
  1989年   241篇
  1988年   205篇
  1987年   168篇
  1986年   119篇
  1985年   115篇
  1984年   92篇
  1983年   63篇
  1982年   38篇
  1981年   39篇
  1980年   30篇
  1979年   31篇
  1978年   30篇
  1977年   38篇
  1976年   61篇
  1973年   20篇
排序方式: 共有10000条查询结果,搜索用时 1 毫秒
901.
The 3D Morphable Model (3DMM) and the Structure from Motion (SfM) methods are widely used for 3D facial reconstruction from 2D single-view or multiple-view images. However, model-based methods suffer from disadvantages such as high computational costs and vulnerability to local minima and head pose variations. The SfM-based methods require multiple facial images in various poses. To overcome these disadvantages, we propose a single-view-based 3D facial reconstruction method that is person-specific and robust to pose variations. Our proposed method combines the simplified 3DMM and the SfM methods. First, 2D initial frontal Facial Feature Points (FFPs) are estimated from a preliminary 3D facial image that is reconstructed by the simplified 3DMM. Second, a bilateral symmetric facial image and its corresponding FFPs are obtained from the original side-view image and corresponding FFPs by using the mirroring technique. Finally, a more accurate the 3D facial shape is reconstructed by the SfM using the frontal, original, and bilateral symmetric FFPs. We evaluated the proposed method using facial images in 35 different poses. The reconstructed facial images and the ground-truth 3D facial shapes obtained from the scanner were compared. The proposed method proved more robust to pose variations than 3DMM. The average 3D Root Mean Square Error (RMSE) between the reconstructed and ground-truth 3D faces was less than 2.6 mm when 2D FFPs were manually annotated, and less than 3.5 mm when automatically annotated.  相似文献   
902.
This paper presents a visual object tracking system which is tolerant to external imaging factors such as illumination, scale, rotation, occlusion and background changes. Specifically, an integration of an online version of total-error-rate minimization based projection network with an observation model of particle filter is proposed to effectively distinguish between the target object and the background. A re-weighting technique is proposed to stabilize the sampling of particle filter for stochastic propagation. For self-adaptation, an automatic updating scheme and extraction of training samples are proposed to adjust to system changes online. Our qualitative and quantitative experiments on 16 public video sequences show convincing performances in terms of tracking accuracy and computational efficiency over competing state-of-the-art algorithms.  相似文献   
903.
904.
905.
906.
Recently, Kim and Bell ( 2011 ) developed a revenue managemnent pricing model with price‐driven substitution. The authors considered production decisions under unlimited production capacity and investigated the impact of price‐driven substitution on a firm's pricing and production decisions. The authors modeled the consumer demands for each market segment as linear additive demand function based on exogenous variables, where demand substitution occurred as a function of price differences between the two products. In this article, we extend this work to examine the impact of a production capacity constraint on the firm's joint pricing and inventory decisions. Based on this extended model, we investigate the impact of price‐driven substitution on a firm's pricing and production decisions where there is a limit on total capacity. We show how revenue managers should adjust prices and production levels to take into account price‐driven substitution under a capacity constraint setting. Both deterministic and stochastic models are developed, and the impact of price‐driven substitution and a capacity constraint on the optimal prices, production levels, and revenues is illustrated.  相似文献   
907.
908.
909.
As smartphones are now widely used, new types of mobile donation applications have emerged. These new types of mobile donation applications transform giving into easy and convenient activities without interfering in users’ daily schedules, and they enable users to keep donating. However, there is still a lack of research on these new types of mobile donation applications as a new venue of technology-mediated civic engagement. The purpose of this article is to investigate the important factors that affect people’s continuance intention to use mobile donation applications. Based on previous studies of cause-related marketing, this study identifies four attributes—type-cause fit, name-cause fit, cause involvement, and perceived effectiveness—that play an important role in mobile donation applications. Our survey results show that all four attributes have significant positive impacts on users’ willingness to use mobile donation applications. The results of this study contribute to mobile application and donation research and provide guidelines for practitioners on the design and creation of mobile donation applications.  相似文献   
910.
This study investigates the theoretical mechanisms by which the variations in source attribution (multiple sources vs. single source) and specialization (multifunctionality vs. single functionality) of Internet of Things (IoT) devices influence the quality of human–IoT interaction. Results from a between‐subjects experiment (N = 100) indicate that IoT devices that elicit the sense of multiple agencies and are specialized in a single function induce greater social presence and perceived expertise, which, in turn, lead individuals to show a more positive attitude toward the devices and to ascribe greater quality to the information transmitted by them. The results also reveal that the effect of multiple source attribution is more pronounced for individuals for whom the content of the information has low personal relevance.  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