全文获取类型
收费全文 | 24834篇 |
免费 | 310篇 |
国内免费 | 14篇 |
专业分类
教育 | 17743篇 |
科学研究 | 1963篇 |
各国文化 | 254篇 |
体育 | 2453篇 |
综合类 | 7篇 |
文化理论 | 246篇 |
信息传播 | 2492篇 |
出版年
2021年 | 264篇 |
2020年 | 397篇 |
2019年 | 631篇 |
2018年 | 836篇 |
2017年 | 776篇 |
2016年 | 774篇 |
2015年 | 451篇 |
2014年 | 598篇 |
2013年 | 4484篇 |
2012年 | 513篇 |
2011年 | 562篇 |
2010年 | 437篇 |
2009年 | 465篇 |
2008年 | 497篇 |
2007年 | 460篇 |
2006年 | 436篇 |
2005年 | 364篇 |
2004年 | 402篇 |
2003年 | 320篇 |
2002年 | 336篇 |
2001年 | 471篇 |
2000年 | 517篇 |
1999年 | 440篇 |
1998年 | 264篇 |
1997年 | 258篇 |
1996年 | 314篇 |
1995年 | 255篇 |
1994年 | 268篇 |
1993年 | 228篇 |
1992年 | 357篇 |
1991年 | 373篇 |
1990年 | 345篇 |
1989年 | 370篇 |
1988年 | 340篇 |
1987年 | 331篇 |
1986年 | 328篇 |
1985年 | 382篇 |
1984年 | 304篇 |
1983年 | 305篇 |
1982年 | 247篇 |
1981年 | 249篇 |
1980年 | 264篇 |
1979年 | 356篇 |
1978年 | 262篇 |
1977年 | 239篇 |
1976年 | 200篇 |
1975年 | 183篇 |
1974年 | 186篇 |
1973年 | 185篇 |
1971年 | 175篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Lotta Haglund Annikki Roos Petra Wallgren‐Björk 《Health information and libraries journal》2018,35(3):251-255
Librarians in Sweden are facing huge challenges in meeting the demands of their organisations and users. This article looks at four key areas: coping with open science/open access initiatives; increasing demands from researchers for support doing systematic reviews; understanding user experiences in Swedish health science libraries; and the consequences of expanding roles for recruitment and continuing professional development. With regard to changing roles, there is an increasing shift from the generalist towards the expert role. The authors raise the issue as to how to prepare those new to the profession to the changing environment of health science libraries. 相似文献
82.
Around 1960, the politics of the emerging media society in Sweden tended to fixate the formative functions of mass communication. The monopoly of public service broadcast media, press subsidies and new tendencies in film policy were some of the issues around which uncertainty prevailed. New methods to provide reliable data were sought by politicians, since empirical facts were required as arguments for an updated media policy. This article examines the different ways that the field of media studies was introduced in Sweden between 1960 and 1980. We argue that Swedish academic media studies departed from, and emerged within, a rather diffuse borderland between industry, politics and academia. The formation of national media research in Sweden can partly be seen as an effect of politicians and the media industry wanting to be better informed on issues such as media influence, media ownership and the habits and composition of the media audience. 相似文献
83.
The purpose of this study is to find a theoretically grounded, practically applicable and useful granularity level of an algorithmically constructed publication-level classification of research publications (ACPLC). The level addressed is the level of research topics. The methodology we propose uses synthesis papers and their reference articles to construct a baseline classification. A dataset of about 31 million publications, and their mutual citations relations, is used to obtain several ACPLCs of different granularity. Each ACPLC is compared to the baseline classification and the best performing ACPLC is identified. The results of two case studies show that the topics of the cases are closely associated with different classes of the identified ACPLC, and that these classes tend to treat only one topic. Further, the class size variation is moderate, and only a small proportion of the publications belong to very small classes. For these reasons, we conclude that the proposed methodology is suitable to determine the topic granularity level of an ACPLC and that the ACPLC identified by this methodology is useful for bibliometric analyses. 相似文献
84.
85.
86.
87.
Eric R. Muoz Jaclyn B. Caccese Brittany E. Wilson Kyle T. Shuler Fernando V. Santos Carolina T. Cabn John J. Jeka Dianne Langford Matthew B. Hudson 《运动与健康科学(英文)》2021,10(2):122-130
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
88.
89.
90.
Based on ideas from subjective uncertainty reduction theory, we examined the extent to which individuals hold similar sport team preferences to their family and friends. We also assessed the extent to which perceived sport importance and personal need for structure are influential in the development of team identification. Australian high school students aged 15.5+/-1.0 years (mean+/-s) completed questionnaires containing the Personal Need for Structure Scale, the Relational-Interdependent Self-Construal scale, a Team Identification Scale, and items assessing perceptions of sport importance and team preferences. As expected, correlations indicated that preferences for sport teams were significantly related to the preferences of family and friends. Separate analyses of variance confirmed the remaining hypotheses. More specifically, individuals who perceived that sport was important identified with the team more than individuals who perceived sport to be less important. Also, individuals high in personal need for structure scored higher in cognitive/affective team identification than those low in this need. Individuals with differing needs for structure did not differ in their scores on other dimensions of team identification. The results support the notion that cognitive/emotional attachments to sport teams are influenced by perceptions of the importance of sport and by needs for subjective structure. It is possible that other psychological motives, such as the desire for self-esteem, facilitate the development of evaluative dimensions of team identification. 相似文献