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   6740篇
  免费   64篇
  国内免费   6篇
教育   5003篇
科学研究   372篇
各国文化   135篇
体育   430篇
综合类   4篇
文化理论   65篇
信息传播   801篇
  2021年   58篇
  2020年   94篇
  2019年   143篇
  2018年   169篇
  2017年   216篇
  2016年   191篇
  2015年   121篇
  2014年   163篇
  2013年   1633篇
  2012年   144篇
  2011年   132篇
  2010年   119篇
  2009年   146篇
  2008年   167篇
  2007年   152篇
  2006年   138篇
  2005年   128篇
  2004年   122篇
  2003年   125篇
  2002年   103篇
  2001年   88篇
  2000年   93篇
  1999年   67篇
  1998年   71篇
  1997年   72篇
  1996年   78篇
  1995年   74篇
  1994年   80篇
  1993年   71篇
  1992年   77篇
  1991年   80篇
  1990年   79篇
  1989年   80篇
  1988年   71篇
  1987年   68篇
  1986年   72篇
  1985年   59篇
  1984年   64篇
  1983年   86篇
  1982年   64篇
  1981年   63篇
  1980年   66篇
  1979年   64篇
  1978年   83篇
  1977年   65篇
  1976年   51篇
  1975年   52篇
  1973年   44篇
  1970年   48篇
  1966年   39篇
排序方式: 共有6810条查询结果,搜索用时 0 毫秒
51.
Purpose: The present study aimed to determine if autonomic cardiac modulation was influenced by acute exposure to normobaric hypoxia. Method: Ten healthy male lowland dwellers completed five block-randomised single-blinded, crossed-over acute exposures to a normobaric hypoxic environment, each separated by 24 hours’ recovery (20.3%, 17.4%, 14.5%, 12.0% and 9.8% FIO2). Supine recordings were made of arterial oxygen saturation and electrocardiogram (ECG). RR intervals from the ECG trace were analysed for time (SDNN, lnrMSSD), frequency (lnVLF, lnLF, lnHF, lnTP, LFnu, and HFnu), and nonlinear (DFA-α1 and SampEn) heart rate variability components. Results: A significant reduction in arterial SaO2 occurred with reduced FIO2, along with a rise in heart rate (Cohen’s d?=?1.16, 95% Confidence Interval [2.64–6.46]), significant at 9.8% FIO2. A decrease in autonomic cardiac modulation was also found as shown by a statistically significant (at 9.8% FIO2) decrease in lnTP (d?=?1.84 [1.74–1.94]), and SampEn (d?=?0.98 [0.83–1.12]) and an increase in DFA-α1 (d?=?0.72 [0.60–0.84]) from normoxia at 9.8% FIO2. Conclusion: The decrease in variability indicated a reduction in autonomic cardiac modulation. There appears to be a threshold ~9.8% FIO2 (~6000?m equiv.), below which significant alterations in autonomic control occur.  相似文献   
52.

Objective

The purpose of this study was to investigate the relative effectiveness of three web-scale discovery (WSD) tools in answering health sciences search queries.

Methods

Simple keyword searches, based on topics from six health sciences disciplines, were run at multiple real-world implementations of EBSCO Discovery Service (EDS), Ex Libris''s Primo, and ProQuest''s Summon. Each WSD tool was evaluated in its ability to retrieve relevant results and in its coverage of MEDLINE content.

Results

All WSD tools returned between 50%–60% relevant results. Primo returned a higher number of duplicate results than the other 2 WSD products. Summon results were more relevant when search terms were automatically mapped to controlled vocabulary. EDS indexed the largest number of MEDLINE citations, followed closely by Summon. Additionally, keyword searches in all 3 WSD tools retrieved relevant material that was not found with precision (Medical Subject Headings) searches in MEDLINE.

Conclusions

None of the 3 WSD products studied was overwhelmingly more effective in returning relevant results. While difficult to place the figure of 50%–60% relevance in context, it implies a strong likelihood that the average user would be able to find satisfactory sources on the first page of search results using a rudimentary keyword search. The discovery of additional relevant material beyond that retrieved from MEDLINE indicates WSD tools'' value as a supplement to traditional resources for health sciences researchers.  相似文献   
53.
The topic of childhood vaccinations has received much news media attention recently, prompting scholars to examine how the public has responded. In light of this news, and the deep divide that seems to exist between parents who support childhood vaccinations and those who do not, this study examines how and why individuals may involve themselves in communication about vaccinations, particularly on social media or in other online environments. Focusing on the concept of communicative action and drawing from spiral of silence and other research, a survey of mothers (= 455) found that those who do not support childhood vaccinations are more likely to engage in communication about the issue, including information seeking, attending, forefending, permitting, forwarding, and sharing. In addition, issue importance and affective and cognitive involvement help drive communicative action regarding childhood vaccinations, which could affect public opinion or public perceptions of the issue. Theoretical and practical implications are discussed.  相似文献   
54.
55.
Robert W. Bell 《PRIMUS》2017,27(3):406-417
Abstract

Mentoring undergraduate students in research is both rewarding and challenging. In this paper we present how we established a summer Research Experience for Undergraduates (REU) program in the mathematical sciences at Michigan State University. A goal of our REU is to include students who are at an early stage of their study of mathematics. We share our experiences in recruiting students, designing research projects, and mentoring our participants. We discuss the challenges we faced and the solutions we found while working with a diverse group of undergraduate students from across the nation.  相似文献   
56.
Business professors were surveyed to determine their attitudes towards two methods of collecting students' teaching evaluations of faculty--the traditional paper-and-pencil method conducted in class and the online method conducted via the Internet. Faculty preferred the traditional paper method, mainly because they believed it would produce a higher and more accurate response than the online method. Faculty characteristics were examined to determine whether they were related to attitudes towards the online method of collecting teaching evaluations. No characteristics were found to be significantly associated with attitudes towards the online method. Suggestions for future researchers are offered.  相似文献   
57.
This study tested preschoolers' ability to provide accurate verbal associations to alcoholic beverage odors and whether this ability was related to parental drinking patterns and motivations. Older preschoolers performed better than younger preschoolers; photographic cues improved performance; children who correctly identified a substance by smell had socially appropriate knowledge of the culturally appropriate users of the substance; children reported liking substances that are used mainly by children and adults, and generally reported disliking substances whose use is legally limited to adults only; children were better at identifying substances they commonly use, but success at recognition of alcoholic beverages was related to heavier parental drinking and use of alcohol for escape reasons. Findings have implications for theories of socialization to drug use and for models of prevention.  相似文献   
58.
This paper documents the effectiveness of a substitute activity in decreasing the frequency of eye poking in a 3‐year‐old nonretarded visually impaired child who was involved in a highly participatory, full‐day reading program with four sighted classmates. Following 49 days of training, eye poking had been eliminated, and the subject was able to read 25 word cards. Elements to consider when selecting a substitute activity to interrupt an established self‐stimulating behaviour such as eye poking are discussed.  相似文献   
59.
The matching cloze procedure, which does not require language production skills and which is simple enough for the classroom teacher to construct unaided, was originally developed to measure reading skills of elementary English‐second‐language pupils. The results of this pilot study with opportunity school children indicate the validity of the procedure as an evaluation technique for slow learning children.  相似文献   
60.
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