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   321篇
  免费   2篇
教育   207篇
科学研究   19篇
各国文化   10篇
体育   58篇
文化理论   4篇
信息传播   25篇
  2023年   3篇
  2022年   2篇
  2021年   4篇
  2020年   3篇
  2019年   8篇
  2018年   19篇
  2017年   11篇
  2016年   12篇
  2015年   9篇
  2014年   9篇
  2013年   76篇
  2012年   4篇
  2011年   12篇
  2010年   12篇
  2009年   12篇
  2008年   8篇
  2007年   10篇
  2006年   5篇
  2005年   12篇
  2004年   8篇
  2003年   4篇
  2002年   9篇
  2001年   2篇
  2000年   7篇
  1999年   2篇
  1998年   5篇
  1997年   3篇
  1995年   3篇
  1994年   3篇
  1993年   3篇
  1992年   3篇
  1991年   7篇
  1990年   3篇
  1989年   3篇
  1988年   3篇
  1987年   3篇
  1986年   3篇
  1985年   4篇
  1983年   2篇
  1982年   3篇
  1980年   2篇
  1979年   2篇
  1978年   1篇
  1976年   1篇
  1973年   1篇
  1970年   1篇
  1965年   1篇
排序方式: 共有323条查询结果,搜索用时 296 毫秒
1.
2.
3.
The cadence that maximises power output developed at the crank by an individual cyclist is conventionally determined using a laboratory test. The purpose of this study was two-fold: (i) to show that such a cadence, which we call the optimal cadence, can be determined using power output, heart-rate, and cadence measured in the field and (ii) to describe methodology to do so. For an individual cyclist's sessions, power output is related to cadence and the elicited heart-rate using a non-linear regression model. Optimal cadences are found for two riders (83 and 70 revolutions per minute, respectively); these cadences are similar to the riders’ preferred cadences (82–92?rpm and 65–75?rpm). Power output reduces by approximately 6% for cadences 20?rpm above or below optimum. Our methodology can be used by a rider to determine an optimal cadence without laboratory testing intervention: the rider will need to collect power output, heart-rate, and cadence measurements from training and racing sessions over an extended period (>6 months); ride at a range of cadences within those sessions; and calculate his/her optimal cadence using the methodology described or a software tool that implements it.  相似文献   
4.
5.

Purpose

Metalloproteinases are a key component of the pathogenesis of abdominal hernias. Obesity is considered a risk factor in herniogenesis and hernia recurrence. The aim of this study was to evaluate the serum concentrations of metalloproteinase-2 (MMP-2), MMP-9, MMP-13, and adiponectin in morbidly obese and nonoverweight controls.

Materials and methods

The participants were recruited from among patients undergoing bariatric and non-bariatric surgery and divided into two groups: I (body mass index (BMI)≥35 kg/m2, n=40) and II (BMI<25 kg/m2, n=30). Serum concentrations of MMP-2, MMP-9, MMP-13, and adiponectin were measured using enzyme-linked immunosorbent assay (ELISA).

Results

A statistically significant difference between groups was observed for MMP-2 concentration. The median MMP-9 concentration was higher in the obese group, but the difference was not statistically significant. Median MMP-13 concentrations did not differ between groups. Serum adiponectin concentration was insignificantly higher in the non-obese group.

Conclusions

The elevated serum MMP-2 and MMP-9 concentrations in obese individuals may be related to the higher incidence of incisional hernias in this population.
  相似文献   
6.
This study evaluates the use of an open‐ended question to determine students' knowledge structure on the topic of galvanic cells. The open‐ended question was developed and administered to 163 Grade 10 students who had earlier completed a course on electrochemistry. Students' responses were marked as well as coded on the basis of the fields identified from their responses. This was then evaluated statistically to determine the collective knowledge structure of the sample of students. The knowledge structure thus mapped contains both canonical concepts and alternative conceptions (ACs). An important finding emerging from this study is that instructors need to focus student's attention on the dynamic processes involving electrons and ions during the operation of galvanic cells. In order for students to fully understand how a galvanic cell operates, they need to see the whole picture. There are three critical components that lead to students' understanding of how an oxidation–reduction reaction can generate energy and how a circuit is complete: transfer of electrons during oxidation–reduction half‐reactions, flow of electrons within metals, and migration of ions in solution. Also, we found that it is possible for students to use correct chemistry concepts in an incorrect way by establishing linkages among these in an inappropriate manner. We reiterate that apart from evaluating students' ACs, it is also important to evaluate the links between the concepts and conceptions present in students' knowledge structure so that teaching can be made more effective.  相似文献   
7.
8.
In November 2006, a focus group of researchers was assembled at a conference hosted by the Society of Scholarly Publishers in Washington, DC. The panel addressed a series of prepared questions regarding current research practices, perceptions, and preferences, particularly as they applied to scientific and medical publications, in corporate, academic, and medical environments. This article highlights issues and views the panel discussed, with the aim of narrowing the gap of understanding between researchers and publishers. This information will help publishers to develop content and delivery methods that are closely aligned with the needs of researchers.  相似文献   
9.
10.
Two studies are reported that used multiple measures of creativity to investigate creativity differences and correlates in arts and science students. The first study examined Divergent Thinking fluency, Self-Rated Creativity and Creative Achievement in matched groups of Art and Science students. Arts students scored higher than Science students on two of the three measures. Regression analysis indicated that the educational domain demographic variable was the most consistent predictor of all three measures of creativity. The second study compared natural science, social science and arts students on two performance and two preference measures of creativity, whilst controlling for the effects of general intelligence. Results indicated only Self-Rated Creativity displayed significant group differences, with the regression analysis suggesting a stronger role of personality variables. The differences between the groups and implications for the measurement of creativity are considered.  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