全文获取类型
收费全文 | 1187篇 |
免费 | 16篇 |
国内免费 | 1篇 |
专业分类
教育 | 888篇 |
科学研究 | 55篇 |
各国文化 | 12篇 |
体育 | 137篇 |
文化理论 | 11篇 |
信息传播 | 101篇 |
出版年
2021年 | 10篇 |
2020年 | 15篇 |
2019年 | 32篇 |
2018年 | 47篇 |
2017年 | 51篇 |
2016年 | 39篇 |
2015年 | 26篇 |
2014年 | 33篇 |
2013年 | 272篇 |
2012年 | 28篇 |
2011年 | 37篇 |
2010年 | 24篇 |
2009年 | 25篇 |
2008年 | 30篇 |
2007年 | 25篇 |
2006年 | 24篇 |
2005年 | 21篇 |
2004年 | 24篇 |
2003年 | 22篇 |
2002年 | 10篇 |
2001年 | 14篇 |
2000年 | 13篇 |
1999年 | 16篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 15篇 |
1992年 | 21篇 |
1991年 | 17篇 |
1990年 | 13篇 |
1989年 | 19篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 21篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1974年 | 5篇 |
1972年 | 8篇 |
1971年 | 10篇 |
1968年 | 5篇 |
排序方式: 共有1204条查询结果,搜索用时 31 毫秒
961.
Nick R. Konkol Christopher J. McNamara Ethel Hellman Ralph Mitchell 《Journal of Cultural Heritage》2012,13(2):115-119
Library materials are susceptible to fungal deterioration. The paper constituents of archival materials are subjected to harmful physical and chemical processes as they are slowly consumed by fungi. Remediation of fungal contamination can be costly and risk further damage to fragile or previously degraded materials. Early detection of fungal growth would permit the use of relatively noninvasive treatments to remediate fungal contamination of artifacts before visible or lasting damage has occurred. Current methods used for the detection of microbial biomass, such as colony counts, microscopic biovolume estimation, and ergosterol analysis are expensive, time consuming, or are inappropriate for use with fungi. Beta-N-acetylhexosaminidase (EC 3.2.1.52) activity provides a rapid and reliable means of fungal detection on a variety of cultural heritage materials. Adapted for use on archival materials, fluorogenic 4-Methylumbelliferyl (MUF) labeled substrate N-acetyl-Beta-D-glucosamine (NAG) was used to detect fungal beta-N-acetylhexosaminidase activity. The fluorescence generated by minute quantities of fungi was quickly detected at an early stage of growth. The sensitivity of the assay was comparable to other biochemical techniques. The fluorometric assay was well-suited for early detection of fungal biomass on paper and assessment of the effectiveness of common remediation practices. 相似文献
962.
963.
964.
965.
Few studies have examined the student learning effects of integrating science with mathematics and technology. We compared a school that integrated mathematics, science and technology in grade 9 to a school in the same district that taught the three courses separately. The distinguishing feature of the integrating school was the reorganization of instruction in the three subjects to prepare students for seven group projects (involving a total of 25 h) that required the application of knowledge and skill that were shared by the three subjects, as well as learning outcomes that were unique to each. The study detected benefits for students in the integrated setting in terms of their ability to apply shared learning outcomes, student motivation, ability to work together and attitudes to appraisal of group work. Female students in the integrated school had a better understanding of selected science learning outcomes. Attitudes toward mid‐term exams were higher in the control school. 相似文献
966.
967.
968.
A forward dynamics computer simulation for replicating tennis racket/ball impacts is described consisting of two rigid segments
coupled with two degrees of rotational freedom for the racket frame, nine equally spaced point masses connected by 24 visco-elastic
springs for the string-bed and a point mass visco-elastic ball model. The first and second modal responses both in and perpendicular
to the racket string-bed plane have been reproduced for two contrasting racket frames, each strung at a high and a low tension.
Ball/string-bed normal impact simulations of real impacts at nine locations on each string-bed and six different initial ball
velocities resulted in <3% RMS error in rebound velocity (over the 16–27 m/s range observed). The RMS difference between simulated
and measured oblique impact rebound angles across nine impact locations was 1°. Thus, careful measurement of ball and racket
characteristics to configure the model parameters enables researchers to accurately introduce ball impact at different locations
and subsequent modal response of the tennis racket to rigid body simulations of tennis strokes without punitive computational
cost. 相似文献
969.
970.
Karen Anderson Jeannette Bastian Ross Harvey Terry Plum G?ran Samuelsson 《Archival Science》2011,11(3-4):349-372
Building virtual archives and preservation curriculum laboratories centered around born-digital and digitized records is a collaborative project currently underway between Simmons College (US) and Mid-Sweden University. In this virtual environment, issues of trust are central to the process, in terms of the both archival curriculum and the collaborative education process itself. The article describes the project, the collaboration, and offers a range of scenarios that demonstrate how the laboratories work within curriculum. 相似文献