全文获取类型
收费全文 | 23506篇 |
免费 | 281篇 |
国内免费 | 14篇 |
专业分类
教育 | 16703篇 |
科学研究 | 1920篇 |
各国文化 | 250篇 |
体育 | 2293篇 |
综合类 | 7篇 |
文化理论 | 212篇 |
信息传播 | 2416篇 |
出版年
2021年 | 235篇 |
2020年 | 359篇 |
2019年 | 537篇 |
2018年 | 728篇 |
2017年 | 665篇 |
2016年 | 663篇 |
2015年 | 402篇 |
2014年 | 533篇 |
2013年 | 4236篇 |
2012年 | 484篇 |
2011年 | 536篇 |
2010年 | 402篇 |
2009年 | 434篇 |
2008年 | 473篇 |
2007年 | 439篇 |
2006年 | 414篇 |
2005年 | 358篇 |
2004年 | 389篇 |
2003年 | 304篇 |
2002年 | 323篇 |
2001年 | 458篇 |
2000年 | 508篇 |
1999年 | 434篇 |
1998年 | 255篇 |
1997年 | 248篇 |
1996年 | 306篇 |
1995年 | 244篇 |
1994年 | 257篇 |
1993年 | 220篇 |
1992年 | 349篇 |
1991年 | 366篇 |
1990年 | 339篇 |
1989年 | 364篇 |
1988年 | 336篇 |
1987年 | 325篇 |
1986年 | 325篇 |
1985年 | 370篇 |
1984年 | 292篇 |
1983年 | 303篇 |
1982年 | 239篇 |
1981年 | 247篇 |
1980年 | 259篇 |
1979年 | 349篇 |
1978年 | 258篇 |
1977年 | 238篇 |
1976年 | 199篇 |
1975年 | 181篇 |
1974年 | 182篇 |
1973年 | 176篇 |
1971年 | 174篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Su Cai Feng-Kuang Chiang Yuchen Sun Chenglong Lin Joey J. Lee 《Interactive Learning Environments》2017,25(6):778-791
Educators must address several challenges inherent to the instruction of scientific disciplines such as physics -- expensive or insufficient laboratory equipment, equipment error, difficulty in simulating certain experimental conditions. Augmented reality (AR) can be a promising approach to address these challenges. In this paper, we discuss the design and implementation of an AR and motion-sensing learning technology that teaches magnetic fields in a junior high school physics course. The purpose of this study is to explore the effects of using natural interaction on students’ physics learning and deep understanding compared to traditional learning tools. The 38 eighth graders who participated in this study were assigned to either an experimental group or a control group. Analysis of the results shows that the AR-based motion-sensing software can improve students’ learning attitude and learning outcome. This study provides a case for the application of AR technology in secondary physics education. 相似文献
972.
Derek J. Harmon Barbie A. Klein Cecilia Im Dylan Romero 《Anatomical sciences education》2022,15(3):620-627
Three-dimensional (3D) printing technology has become more affordable, accessible, and relevant in healthcare, however, the knowledge of transforming medical images to physical prints still requires some level of training. Anatomy educators can play a pivotal role in introducing learners to 3D printing due to the spatial context inherent to learning anatomy. To bridge this knowledge gap and decrease the intimidation associated with learning 3D printing technology, an elective was developed through a collaboration between the Department of Anatomy and the Makers Lab at the University of California, San Francisco. A self-directed digital resource was created for the elective to guide learners through the 3D printing workflow, which begins with a patient's computed tomography digital imaging and communication in medicine (DICOM) file to a physical 3D printed model. In addition to practicing the 3D printing workflow during the elective, a series of guest speakers presented on 3D printing applications they utilize in their clinical practice and/or research laboratories. Student evaluations indicated that their intimidation associated with 3D printing decreased, the clinical and research topics were directly applicable to their intended careers, and they enjoyed the autonomy associated with the elective format. The elective and the associated digital resource provided students with the foundational knowledge of 3D printing, including the ability to extract, edit, manipulate, and 3D print from DICOM files, making 3D printing more accessible. The aim of disseminating this work is to help other anatomy educators adopt this curriculum at their institution. 相似文献
973.
974.
J. Bruce Francis Michalina Vaughan Colin Flood Page Sally Tomlinson R. A. Becher Margaret C. Ives John Urry K. G. Collier Meir Zadok Charles Carter Jürgen Schramm Jean Barry Graeme C. Moodie Donald Bligh R. A. King D. G. Mulcahy Peter Scott F. R. Charmer T. R. Bone John A. Hughes Roger Greenhough Alec M. Ross John Wakeford Joyce Skinner Duncan B. Nimmo Cedric Cullingford L. R. B. Elton 《Higher Education》1979,8(6):709-744
975.
976.
Jürgen Altmann 《Ethics and Information Technology》2013,15(2):137-152
Arming uninhabited vehicles (UVs) is an increasing trend. Widespread deployment can bring dangers for arms-control agreements and international humanitarian law (IHL). Armed UVs can destabilise the situation between potential opponents. Smaller systems can be used for terrorism. Using a systematic definition existing international regulation of armed UVs in the fields of arms control, export control and transparency measures is reviewed; these partly include armed UVs, but leave large gaps. For preventive arms control a general prohibition of armed UVs would be best. If that is unattainable, several measures should be taken. An explicit prohibition of autonomous attack, that is without a human decision, should be added to IHL. Concerning armed UVs remotely controlled by a human soldier, recommendations differ according to type or mission. New kinds of uninhabited nuclear-weapon carriers should be banned. Space weapons should be prohibited in general. UVs smaller than 0.2–0.5 m should be banned. Bigger remotely controlled armed UVs not equipped with weapons of mass destruction should be subject to numerical limitations in various categories. For these the Treaty on Conventional Armed Forces in Europe is an important precedent. 相似文献
977.
This study examined whether or not activity monitor data collected as part of a typical 7-day physical activity (PA) measurement protocol can be expected to be missing at random. A total of 315 participants (9–18 years) each wore a SenseWear Armband monitor for 7 consecutive days. Participants were classified as “compliant” (86 boys and 124 girls) if they had recorded accelerometer data during 70% or more of the predefined awake time (7 AM–10 PM) on four different days; and “non-compliant” (44 boys and 51 girls) when not meeting these criteria. Linear mixed models were used to examine differences in energy expenditure (EE) levels by compliance across 10 different time periods. The results indicated that non-compliant girls were older (13.4 ± 2.9 vs. 12.2 ± 2.5) and taller (156.8 ± 10.3 vs. 152.8 ± 11.3) than their same gender compliant peers (P < .05). Comparisons of EE rates at segmented portions of the day revealed no differences between compliant and non-compliant groups (P ≥ .05). Differences in EE ranged from ?0.32 kcal · kg?1 · h?1 (before school time) to 0.62 kcal · kg?1 · h?1 (physical education class) in boys and ?0.39 kcal · kg?1 · h?1 (transportation from school) to 0.37 kcal · kg?1 · hour?1 (recess) in girls. The results showed that compliant and non-compliant individuals differed in a few demographic characteristics but exhibited similar activity patterns. This suggests that data were considered to be missing at random, but additional work is needed to confirm this observation in a representative sample of children using other types of activity monitors and protocols. 相似文献
978.
This paper has 2 goals: to review the history of the developmental study of infants and children at biological risk and to appraise the current state of the art. The scope of the review is from 1920 to the present and emphasizes the role of developmentalists. 4 research phases are identified, each reflecting aspects of the social, political, health, and psychological zeitgeist. First, from 1920 to World War II, research was primarily "catalog" and had diverse themes; however, several issues were raised that continue to have relevance. Second, during the postwar years, research often focused on the cognitive and emotional residuals of handicaps, particularly cerebral palsy and poliomyelitis. Third, the 1960s marked the funding of major seminal longitudinal investigations of perinatal risk factors, and studies of very young infants "at risk." And fourth, in the last and current period, technological advances of the 1970s first applied to research with normally developing children were then extended to at-risk groups and revolutionized the methods of studying risk. Finally, we suggest that, although a considerable amount of information has been obtained about developmental phenomena subsequent to biological risk, our research literature is fragmented and difficult to synthesize. We conclude by offering strategies to foster research and the integration of knowledge. 相似文献
979.
Tamara van Gog K. Anders Ericsson Remy M. J. P. Rikers Fred Paas 《Educational technology research and development : ETR & D》2005,53(3):73-81
Cognitive load theory (CLT) has been successful in identifying instructional formats that are more effective and efficient
than conventional problem solving in the initial, novice phase of skill acquisition. However, recent findings regarding the
“expertise reversal effect” have begun to stimulate cognitive load theorists to broaden their horizon to the question of how
instructional design should be altered as a learner's knowledge increases. To answer this question, it is important to understand
how expertise is acquired and what fosters its development. Expert performance research, and, in particular, the theoretical
framework of deliberate practice have given us a better understanding of the principles and activities that are essential
in order to excel in a domain. This article explores how these activities and principles can be used to design instructional
formats based on CLT for higher levels of skills mastery. The value of these formats for e-learning environments in which
learning tasks can be adaptively selected on the basis of online assessments of the learner's level of expertise is discussed.
In their preparation of this article, the first and last authors were supported by an Internationalization grant from the
Netherlands Organization for Scientific Research (NWO, The Hague, project number 411-01-010). 相似文献
980.