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11.
To date, a limited number of aqueous conditions have been tested experimentally as potential cleaning reagents on modern acrylic paint films. Those assessed have tended to extract measurable quantities of paint film components and distort the paint films physically. In this paper the results of a series of experiments designed to examine pH, conductivity, and specific ion effects of potential aqueous cleaning solutions on a series of commercial acrylic paints are reported. A three-dimensional microscopic technique was used to characterize the physical (volume and surface roughness) changes and liquid chromatography-tandem mass spectrometry was used to characterize the chemical (extracted surfactant) changes following paint film exposure to the aqueous solution. The tested paint films in this study clearly exhibit an isotonic point below which swelling and extraction is significant, and above which the swelling and extraction is diminished. Manipulation of conductivity and the ionic species in solution can reduce both the physical film changes and surfactant extraction from acrylic paint films; while pH appears to be of limited use in controlling aqueous cleaning effects. Moreover, there seems to be a specific ion effect for both swelling and de-swelling in acrylic paint films that can be rationalized through the Hofmeister Series. 相似文献
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环境社会学与自然资源社会学是关于社会与自然界相互关系的两个主要研究传统。目前关于这两个分支学科的讨论主要是局限在美国学术界内,而其对于其它国家环境和社会研究学科建设的借鉴作用尚未引起足够的重视,这正是本文在中国的学术背景中提出环境社会学与自然资源社会学相互融合问题的原因所在。环境社会学在中国正处于重要的学科建设阶段,垮学科的中国环境与资源社会学在投身中国"资源节约型、环境友好型"社会的建设中完全有希望实现环境社会学与自然资源社会学的实质融合。 相似文献
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CALCULUS STUDENTS’ AND INSTRUCTORS’ CONCEPTUALIZATIONS OF SLOPE: A COMPARISON ACROSS ACADEMIC LEVELS
Courtney Nagle Deborah Moore-Russo Janine Viglietti Kristi Martin 《International Journal of Science and Mathematics Education》2013,11(6):1491-1515
This study considers tertiary calculus students’ and instructors’ conceptualizations of slope. Qualitative techniques were employed to classify responses to 5 items using conceptualizations of slope identified across various research settings. Students’ responses suggest that they rely on procedurally based conceptualizations of slope, showing little evidence of covariational reasoning. In contrast, instructors’ responses demonstrated a multi-dimensional understanding of slope as a functional property, which applies to real-world situations and plays an integral role in the development of key calculus concepts. While relatively diverse, the instructors’ responses seldom reported determining increasing or decreasing trends of a line from its slope. This conceptualization was used frequently by students and could help them better understand how slope ties to positive and negative derivatives. The most frequently used conceptualizations for students in this study align with past research findings on the emphasis of the secondary mathematics curriculum, supporting the possibility of cultural influences (academic and geographic) on individuals’ conceptualizations of slope. Thus, this study provides valuable insight into conceptualizations of slope and provides direction for future research on slope and the broader topic of cultural influences on mathematical meaning. 相似文献
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Tara O’Connor Shelley Courtney A. Waid Rhonda R. Dobbs 《Journal of Criminal Justice Education》2013,24(4):526-545
Students majoring in criminology and criminal justice are assumed to have more detailed and accurate knowledge about crime, criminal justice, and punishment practices than peers majoring in other disciplines. The purpose of this study was to examine if criminology/criminal justice majors were more or less punitive than students pursuing other majors at three universities using standard predictors of punitiveness that have not been consistently examined in previous research. The results indicate that criminology and criminal justice students are more punitive in the combined three‐campus sample and in two of the three‐campus samples considered separately. 相似文献
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Austin Denise A. Pegram Nigel Hodson Courtney Hepplewhite Glenda Nelson Belinda 《Tertiary Education and Management》2021,27(3):281-296
Tertiary Education and Management - The marked increase in transnational higher education third party arrangements in recent years represents globalizing forms of education. Third party... 相似文献
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We study the effects of homeschool background and time use on academic performance among students at Patrick Henry College, a private religious institution with a 63-credit core classical liberal arts curriculum. Using ordinary least squares regression analysis, we examine four research questions: (1) Does time use influence academic performance? (2) Do homeschooled students perform differently than traditionally schooled students? (3) Does parental education moderate the impact of homeschooling on academic performance? (4) Does homeschooling moderate the impact of ACT scores on academic performance? 相似文献
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ABSTRACTThis paper draws on data collected from two of the most extensive longitudinal studies of care leavers in the US. The Midwest Study (2003–2011) included 732 youths in foster care in three Midwestern states, and the CalYOUTH Study (2012–present) includes 727 youths in California foster care. The paper has three objectives: (1) describe trends in secondary and postsecondary educational attainment at different ages; (2) summarise findings on predictors of educational attainment; and (3) summarise findings on the impact of extended foster care (EFC) on educational attainment. Results from these two studies show that by age 21, 77–85% of care leavers finish a secondary credential and 31–52% enrol in college. By age 25, about 8% have earned a college degree. Results from multivariate analyses find that youths’ educational background and parental status were consistently associated with later educational attainment. Specific aspects of social support also influenced college outcomes. Life demands after enrolling in college (e.g. employment, parenthood) played a more influential role in college degree attainment than did aspects of youths’ background. Characteristics of colleges also predicted youths’ odds of degree completion. Finally, existing evidence suggests that EFC promotes secondary credential completion and college entry, but not college persistence or degree completion. 相似文献