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   1705篇
  免费   31篇
教育   1396篇
科学研究   29篇
各国文化   37篇
体育   63篇
综合类   1篇
文化理论   7篇
信息传播   203篇
  2022年   8篇
  2021年   18篇
  2020年   25篇
  2019年   56篇
  2018年   66篇
  2017年   78篇
  2016年   61篇
  2015年   37篇
  2014年   55篇
  2013年   443篇
  2012年   45篇
  2011年   36篇
  2010年   48篇
  2009年   45篇
  2008年   49篇
  2007年   41篇
  2006年   31篇
  2005年   38篇
  2004年   40篇
  2003年   29篇
  2002年   26篇
  2001年   25篇
  2000年   19篇
  1999年   19篇
  1998年   12篇
  1997年   25篇
  1996年   17篇
  1995年   22篇
  1994年   19篇
  1993年   21篇
  1992年   13篇
  1991年   21篇
  1990年   18篇
  1989年   12篇
  1988年   10篇
  1987年   7篇
  1986年   14篇
  1985年   16篇
  1984年   21篇
  1983年   13篇
  1982年   16篇
  1981年   14篇
  1980年   14篇
  1979年   11篇
  1978年   7篇
  1977年   11篇
  1976年   11篇
  1975年   9篇
  1974年   13篇
  1973年   7篇
排序方式: 共有1736条查询结果,搜索用时 0 毫秒
91.
92.
93.
In laboratory medicine, several studies have described the most frequent errors in the different phases of the total testing process, and a large proportion of these errors occur in the pre-analytical phase. Schemes for registration of errors and subsequent feedback to the participants have been conducted for decades concerning the analytical phase by External Quality Assessment (EQA) organizations operating in most countries. The aim of the paper is to present an overview of different types of EQA schemes for the pre-analytical phase, and give examples of some existing schemes. So far, very few EQA organizations have focused on the pre-analytical phase, and most EQA organizations do not offer pre-analytical EQA schemes (EQAS). It is more difficult to perform and standardize pre-analytical EQAS and also, accreditation bodies do not ask the laboratories for results from such schemes. However, some ongoing EQA programs for the pre-analytical phase do exist, and some examples are given in this paper. The methods used can be divided into three different types; collecting information about pre-analytical laboratory procedures, circulating real samples to collect information about interferences that might affect the measurement procedure, or register actual laboratory errors and relate these to quality indicators. These three types have different focus and different challenges regarding implementation, and a combination of the three is probably necessary to be able to detect and monitor the wide range of errors occurring in the pre-analytical phase.  相似文献   
94.
95.
96.
Education and Information Technologies - 3D printing is an emerging educational technology that is said to prepare learners for a more technologically designed world. In this review, 3D printing...  相似文献   
97.
ABSTRACT

Professional American football games are recorded in digital video with multiple cameras, often at high resolution and high frame rates. The purpose of this study was to evaluate the accuracy of a videogrammetry technique to calculate translational and rotational helmet velocity before, during and after a helmet impact. In total, 10 football impacts were staged in a National Football League (NFL) stadium by propelling helmeted 50th percentile male crash test dummies into each other or the ground at speeds and orientations representative of concussive impacts for NFL players. The tests were recorded by experienced sports film crews to obtain video coverage and quality typically available for NFL games. A videogrammetry procedure was used to track the position and rotation of the helmet throughout the relevant time interval of the head impact. Compared with rigidly mounted retroreflective marker three dimensional (3-D) motion tracking that was concurrently collected in the experiments, videogrammetry accurately calculated changes in translational and rotational velocity of the helmet using high frame rate (two cameras at 240 Hz) video (7% and 15% error, respectively). Low frame rate (2 cameras at 60 Hz) video was adequate for calculating pre-impact translational velocity but not for calculating the translational or rotational velocity change of the helmet during impact.  相似文献   
98.
99.
你是爱,是暖,是希望,你是人间四月天 那些隐匿在黑暗中的云朵瞬间把太阳遮蔽,阳光从云朵里投射出来,映出云朵的轮廓,像一个模糊的幻境。云朵蘸满了墨水一样沉甸甸地粘在暗色的苍穹,欲来的雨云塞满了曾经湛蓝的天空。然后,雨水铺天盖地而来。  相似文献   
100.
The Gulliford Lecture 2003 was given by Professor Ann Lewis of the School of Education at the University of Birmingham. Professor Lewis's lecture, on which this article is based, focused on the process of listening to the views of children and, in particular, children with learning difficulties. Following the near-universal ratification of the United Nations (UN) Convention on the Rights of the Child, a plethora of recent initiatives, both in the UK and internationally, has encouraged professionals to access children's views about provision (educational, health-related, social and legal). A range of materials has been developed to support this process, often by, or in liaison with, children's charities. At the same time, research provides valuable insights into effective practice in exploring the views of children with learning difficulties. In this article, Ann Lewis reviews ten strategies for gathering the views of children and raises four challenges for the further development of policy and practice. She closes her argument with a call for greater rigour and critical evaluation in this crucial and demanding area.  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