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   3188篇
  免费   81篇
  国内免费   46篇
电工技术   22篇
综合类   1453篇
化学工业   140篇
金属工艺   43篇
机械仪表   70篇
建筑科学   329篇
矿业工程   14篇
能源动力   15篇
轻工业   78篇
水利工程   27篇
石油天然气   13篇
武器工业   2篇
无线电   140篇
一般工业技术   100篇
冶金工业   310篇
原子能技术   1篇
自动化技术   558篇
  2024年   4篇
  2023年   20篇
  2022年   36篇
  2021年   41篇
  2020年   51篇
  2019年   60篇
  2018年   25篇
  2017年   29篇
  2016年   68篇
  2015年   87篇
  2014年   217篇
  2013年   192篇
  2012年   238篇
  2011年   265篇
  2010年   228篇
  2009年   232篇
  2008年   234篇
  2007年   231篇
  2006年   190篇
  2005年   166篇
  2004年   131篇
  2003年   128篇
  2002年   125篇
  2001年   59篇
  2000年   49篇
  1999年   35篇
  1998年   16篇
  1997年   13篇
  1996年   10篇
  1995年   6篇
  1994年   13篇
  1993年   5篇
  1991年   4篇
  1990年   6篇
  1985年   4篇
  1983年   5篇
  1982年   3篇
  1981年   8篇
  1980年   4篇
  1975年   4篇
  1965年   5篇
  1964年   5篇
  1963年   4篇
  1961年   3篇
  1959年   3篇
  1958年   3篇
  1957年   8篇
  1956年   5篇
  1955年   5篇
  1954年   6篇
排序方式: 共有3315条查询结果,搜索用时 15 毫秒
1.
2.
媒体融合发展是高校开展新闻宣传工作的必然要求,针对高校学生记者队伍建设中存在的问题,提出要以“选修课+线上学习资源+校内培训”为抓手,学习相关专业学科知识;以学校融媒体中心为基础,为学生记者提供实践平台;深化学生记者对媒体融合传播理念的认识,不断提升互联网思维和创新能力。  相似文献   
3.
4.
The primary goal of this study is to create and test a lecture‐capture system that can rearrange visual elements while recording is still taking place, in such a way that student performance can be positively influenced. The system we have devised is capable of integrating and rearranging multimedia sources, including learning content, the instructor and students' images, into lecture videos that are embedded in a website for students to review after school. The present study employed a two‐group experimental design, with 153 participants (145 females and 8 males) making up an experimental group in which lecture courses were recorded using the new lecture‐capture system, and 149 participants (140 females and 9 males) forming a control group whose lectures were recorded by traditional means. All participants were in the freshman college and studying Introduction to Computer and Information Science in one of six classes, and were randomly assigned to one of the two groups. The participants' midterm examination and final examination scores were collected as indicators of their academic performance, with their mathematics entrance scores used as a pre‐test. The findings obtained from analysis of covariance (ANCOVA) suggest that appropriate rearrangement of visual elements in lecture videos can significantly impact students' learning performance.  相似文献   
5.
Although previous research has investigated widespread use of social media, especially Facebook, by youth attending college, the conditions under which these media foster adjustment to college remain unclear. This study tested a model illuminating pathways linking social competence to college adjustment via students’ perceptions about the usefulness of Facebook and ways in which they used the medium. Self-report survey data from 321 college students (M age = 20.09; 58% female; 84% Caucasian) attending a major Midwestern university supported the proposed model, indicating that higher social competence could foster or impede college adjustment, depending upon how it was related to beliefs about the usefulness of different Facebook functions and how these perceptions, in turn, were associated with patterns of Facebook use. Findings underscore the importance of considering connections among personal attributes, perception of media effectiveness, and media behaviors in assessing the implications of social media for users’ psychosocial well-being.  相似文献   
6.
This paper uses a mixed-methods approach to examine the relation between online academic disclosure and academic performance. A multi-ethnic sample of college students (N = 261; male = 66; female = 195; M age ≈ 22 years) responded to open-ended questions about their Facebook use. Thematic analysis revealed that over 14% of the Facebook wall posts/status updates (N = 714) contained academic themes; positive states were more frequent than negative and neutral states and students with lower GPAs expressed negative states more often. A path analysis suggested that academic performance may determine college students’ Facebook use, rather than the reverse. Implications for student support services are discussed.  相似文献   
7.
(0.95–x) BaTiO3–0.05 BiYbO3x BiFeO3 (x?=?0, 0.01, 0.02, and 0.04) (abbreviated as (0.95–x) BT–0.05 BY–x BFO) ceramics were fabricated by conventional sintering (CS) and microwave sintering (WS) methods. Effects of sintering method and BFO dopant on the microstructure and electric properties of (0.95–x) BT–0.05 BY–x BFO ceramics were comparatively investigated. X-ray diffraction showed that all CS and WS samples presented a single perovskite phase. It was also found that WS ceramics possessed denser microstructure and finer grains compared to CS samples as indicated by the surface morphology characterization. Dielectric measurements revealed that all samples exhibited the weak relaxation behavior; however, the degree of relaxation behavior of BT–BY based ceramic could be strengthened by addition of BFO and by WS method. Moreover, the temperature and frequency stability could be improved with doped BFO. The density of 0.93BT–0.05BY–0.02BFO ceramic was found to be the largest while that of 0.94BT–0.05BY–0.01BFO ceramic was the smallest, thus, the dielectric constant of 0.93BT–0.05BY–0.02BFO was significantly larger than that of 0.94BT–0.05BY–0.01BFO and 0.94BT–0.05BY–0.04 BFO ceramics. minimum dielectric constant of (0.95–x) BT–0.05 BY–x BFO ceramic was obtained at x?=?0.01. Ferroelectric measurements indicated that all samples showed the slim hysteresis loop. The remnant polarization (Pr) and coercive field (EC) of (0.95–x) BT–0.05 BY–x BFO ceramics first decreased and then increased with increasing x,the minimum values were obtained at x?=?0.01. Moreover, Pr and EC of WS ceramics were slightly larger than those of CS ceramics, indicating that higher density and larger grain sizes contributed to enhancing the ferroelectric characteristic. These findings indicate that addition of moderate amount of BFO and use of WS technique can strengthen the degree of relaxation behavior and improve the ferroelectric properties of BT–BY based ceramics.  相似文献   
8.
The effects of Sr2+ substitution for Ba2+ on microwave dielectric properties and crystal structure of Ba3-xSrx(VO4)2 (0 ≤ x ≤ 3, BSVO) solid solution were investigated. Such Sr2+ substitution contributes to significant reduction in sintering temperature from 1400 °C to 1150 °C. Both permittivity (r) and quality factor (Q × f) values decreased with increasing x value, which was determined to be related with the descending values of average polarizability and packing fraction, whereas the increase in τf value was explained by the decreased average VO bond length, A-site bond valence. BSVO ceramics possessed encouraging dielectric performances with r = 12.2–15.6 ± 0.1, Q × f = 44,340 - 62,000 ± 800 GHz, and τf = 24.5–64.5 ± 0.2 ppm/°C. Low-temperature sintering was manipulated by adding B2O3 as sintering additive for the representative Sr3V2O8 (SVO) ceramic and only 1 wt.% B2O3 addition successfully contributed to a 21.7% decrease in sintering temperature to 900 °C, showing good chemical compatibility with silver electrodes, which render BSVO series and SVO ceramics potential candidates in multilayer electronic devices fabrication.  相似文献   
9.
10.
面对新技术与新经济,土木专业作为传统工科专业有升级转型为新工科的必要性与迫切性。为助推新型土木工程专业个性化人才培养,河海大学土木与交通学院基于推进学科交融、跨界整合能力培养的发展主旨进行了独特的专业学生组织交流平台建设,在人的全面发展、现代认知学习、建构主义、生涯发展等理论的基础上,以国际竞赛、国际年会、讲堂制度和三高体系为载体,构建了ASCE国际学生组织河海大学分会,以激发学生主体作用,推进新工科建设。  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