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   14883篇
  免费   203篇
  国内免费   12篇
教育   10172篇
科学研究   1329篇
各国文化   154篇
体育   1529篇
综合类   24篇
文化理论   104篇
信息传播   1786篇
  2021年   118篇
  2020年   215篇
  2019年   314篇
  2018年   358篇
  2017年   438篇
  2016年   383篇
  2015年   253篇
  2014年   330篇
  2013年   2675篇
  2012年   294篇
  2011年   335篇
  2010年   259篇
  2009年   290篇
  2008年   274篇
  2007年   270篇
  2006年   248篇
  2005年   236篇
  2004年   472篇
  2003年   360篇
  2002年   393篇
  2001年   253篇
  2000年   265篇
  1999年   203篇
  1998年   101篇
  1997年   126篇
  1996年   156篇
  1995年   142篇
  1994年   131篇
  1993年   133篇
  1992年   182篇
  1991年   184篇
  1990年   166篇
  1989年   217篇
  1988年   182篇
  1987年   210篇
  1986年   181篇
  1985年   237篇
  1984年   193篇
  1983年   175篇
  1982年   153篇
  1981年   131篇
  1980年   111篇
  1979年   175篇
  1978年   138篇
  1977年   123篇
  1976年   143篇
  1975年   105篇
  1974年   119篇
  1973年   97篇
  1971年   108篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
131.
The independence of the media under Ghana’s Fourth Republic is assessed from the perspective of standards and professionalism. Using a qualitative method, the study shows that unethical practices are evident in the print media landscape in Ghana, and argues that this can be traced to four major spheres: educational qualification, existence of several professional associations, a weak regulatory body and “money matters”. Overall, the study argues that legalities form a minimal part of the independence of the Ghanaian media but concerns about freedom seem to be self-inflicted by the very media practitioners through their actions and sometimes questionable reportage.  相似文献   
132.
This article explores the existence of a “citizen-centered journalism” that sees citizens as crucial participants in the construction of news and as co-creators of their own worlds. Through qualitative case studies of three news organizations, the article examines the motivation for using a citizen-centered approach, the news routines that are required to do so, the categories of content produced, and the perceived impact of this approach. The results suggest these news organizations are working in partnership with communities and striving to give a voice to historically marginalized communities. The journalists, however, see citizen participation as complementary to professional journalistic routines that favor verifiable information, rather than assigning inherent value to it for its own sake.  相似文献   
133.
134.
135.
136.
137.
BackgroundConsidering the potential cumulative effects of repetitive head impact (HI) exposure, we need sensitive biomarkers to track short- and long-term effects. Circulating small extracellular vesicles (sEVs) (<200 nm) traffic biological molecules throughout the body and may have diagnostic value as biomarkers for disease. The purpose of this study was to identify the microRNA (miRNA) profile in circulating sEVs derived from human plasma following repetitive HI exposure.MethodsHealthy adult (aged 18–35 years) soccer players were randomly assigned to one of 3 groups: the HI group performed 10 standing headers, the leg impact group performed 10 soccer ball trapping maneuvers over 10 min, and the control group did not participate in any soccer drills. Plasma was collected before testing and 24 h afterward, and sEVs were isolated and characterized via nanoparticle tracking analysis. Next-generation sequencing was utilized to identify candidate miRNAs isolated from sEVs, and candidate microRNAs were analyzed via quantitative polymerase chain reaction. In silico target prediction was performed using TargetScan (Version 7.0; targetscan.org) and miRWalk (http://mirwalk.umm.uni-heidelberg.de/) programs, and target validation was performed using luciferase reporter vectors with a miR-7844-5p mimic in human embryonic kidney (HEK) 293T/17 cells.ResultsPlasma sEV concentration and size were not affected across time and group following repetitive HI exposure. After 24 h, the HI read count from next-generation sequencing showed a 4-fold or greater increase in miR-92b-5p, miR-423-5p, and miR-24-3p and a 3-fold or greater decrease in miR-7844-5p, miR-144-5p, miR-221-5p, and miR-22-3p. Analysis of quantitative polymerase chain reaction revealed that leg impact did not alter the candidate miRNA levels. To our knowledge, miR-7844-5p is a previously unknown miRNA. We identified 8 miR-7844-5p mRNA targets: protein phosphatase 1 regulatory inhibitor subunit 1B (PPP1R1B), LIM and senescent cell antigen-like domains 1 (LIMS1), autophagy-related 12 (ATG12), microtubule-associated protein 1 light chain 3 beta (MAP1LC3B), integrin subunit alpha-1 (ITGA1), mitogen-activated protein kinase 1 (MAPK1), glycogen synthase kinase 3β (GSK3β), and mitogen-activated protein kinase 8 (MAPK8).ConclusionCollectively, these data indicate repetitive HI exposure alters plasma sEV miRNA content, but not sEV size or number. Furthermore, for the first time we demonstrate that previously unknown miR-7844-5p targets mRNAs known to be involved in mitochondrial apoptosis, autophagy regulation, mood disorders, and neurodegenerative disease.  相似文献   
138.
139.
We tested some of the key predictions of processing efficiency theory using a simulated rally driving task. Two groups of participants were classified as either dispositionally high or low anxious based on trait anxiety scores and trained on a simulated driving task. Participants then raced individually on two similar courses under counterbalanced experimental conditions designed to manipulate the level of anxiety experienced. The effort exerted on the driving tasks was assessed though self-report (RSME), psychophysiological measures (pupil dilation) and visual gaze data. Efficiency was measured in terms of efficiency of visual processing (search rate) and driving control (variability of wheel and accelerator pedal) indices. Driving performance was measured as the time taken to complete the course. As predicted, increased anxiety had a negative effect on processing efficiency as indexed by the self-report, pupillary response and variability of gaze data. Predicted differences due to dispositional levels of anxiety were also found in the driving control and effort data. Although both groups of drivers performed worse under the threatening condition, the performance of the high trait anxious individuals was affected to a greater extent by the anxiety manipulation than the performance of the low trait anxious drivers. The findings suggest that processing efficiency theory holds promise as a theoretical framework for examining the relationship between anxiety and performance in sport.  相似文献   
140.
This study assessed muscular torque and rate of torque development following concentric (CON) or eccentric (ECC) isokinetic training. Thirty-eight women were randomly assigned to either CON or ECC training groups. Training consisted of knee extension and flexion of the nondominant leg three times per week for 20 weeks (SD = 1). Eccentric training increased ECC knee extension and flexion peak torque more than CON training. The ECC group improved acceleration time and time to peak torque with ECC movements versus the CON group. Slow-velocity ECC isokinetic training yielded greater ECC and similar CON torque development gains versus CON training over the course of 20 weeks in young women.  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