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   117201篇
  免费   1859篇
  国内免费   233篇
教育   80673篇
科学研究   13342篇
各国文化   1980篇
体育   9430篇
综合类   171篇
文化理论   1056篇
信息传播   12641篇
  2021年   905篇
  2020年   1644篇
  2019年   2556篇
  2018年   3060篇
  2017年   3299篇
  2016年   3361篇
  2015年   2295篇
  2014年   3173篇
  2013年   27241篇
  2012年   2347篇
  2011年   2701篇
  2010年   2310篇
  2009年   2601篇
  2008年   2353篇
  2007年   2092篇
  2006年   2341篇
  2005年   2339篇
  2004年   2981篇
  2003年   2267篇
  2002年   2067篇
  2001年   1909篇
  2000年   1503篇
  1999年   1384篇
  1998年   1267篇
  1997年   1341篇
  1996年   1556篇
  1995年   1352篇
  1994年   1349篇
  1993年   1342篇
  1992年   1365篇
  1991年   1277篇
  1990年   1307篇
  1989年   1208篇
  1988年   1048篇
  1987年   1008篇
  1986年   1035篇
  1985年   1260篇
  1984年   1152篇
  1983年   1099篇
  1982年   1091篇
  1981年   1011篇
  1980年   964篇
  1979年   1111篇
  1978年   1050篇
  1977年   957篇
  1976年   867篇
  1975年   716篇
  1974年   709篇
  1973年   679篇
  1972年   524篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
51.
Four experiments show that 4- and 5-year-olds (total N = 112) can identify the referent of underdetermined utterances through their Naïve Utility Calculus—an intuitive theory of people’s behavior structured around an assumption that agents maximize utilities. In Experiments 1–2, a puppet asked for help without specifying to whom she was talking (“Can you help me?”). In Experiments 3–4, a puppet asked the child to pass an object without specifying what she wanted (“Can you pass me that one?”). Children’s responses suggest that they considered cost trade-offs between the members in the interaction. These findings add to a body of work showing that reference resolution is informed by commonsense psychology from early in childhood.  相似文献   
52.
In typical development, gestures precede and predict language development. This study examines the developmental sequence of expressive communication and relations between specific gestural and language milestones in toddlers with autism spectrum disorder (ASD), who demonstrate marked difficulty with gesture production and language. Communication skills across five stages (gestures, word approximations, first words, gesture-word combinations, and two-word combinations) were assessed monthly by blind raters for toddlers with ASD participating in an randomized control trial of parent-mediated treatment (N = 42, 12–30 months). Findings revealed that toddlers acquired skills following a reliable (vs. idiosyncratic) sequence and the majority of toddlers combined gestures with words before combining words in speech, but in contrast to the pattern observed in typical development, a significant subset acquired pointing after first words.  相似文献   
53.
Reading and Writing - Reading and writing are distinct skill areas that influence each other across development. Children with autism spectrum disorder (ASD) are noted to exhibit challenges in both...  相似文献   
54.
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   
55.
Genetic variation in the angiotensin II type 1 receptor (AT1R) has an important effect on the outcome of acute coronary syndrome (ACS) initiated treatment with captopril. This study aims to investigate the impact of genetic polymorphism of AT1R (rs5186 and rs275651) on the ACS outcome in Iraqi patients treated with captopril. A total of 250 Iraqi individuals with ACS were included in this case—control study and they were divided into two study groups; Study group 1 included 125 participants who were prescribed captopril, 25 mg twice daily and study group 2 included 125 participants who received no captopril as part of their ACS treatment (control study). The AT1R gene (rs5186) CC genotype was found to be associated with ST-elevation myocardial infarction (STEMI) (Odd’s ratio (O.R) = 1.2, P = 0.7), while AC was associated with Non-ST-elevation myocardial infarction (NSTEMI) and unstable angina (UA) (O.R = 1.2, P = 0.8). AC genotype is more prone to have Percutaneous coronary intervention (PCI) after ACS attack (O.R = 1.2, P = 0.6). CC genotype had a risk to get less improvement (O.R = 1.6, P = 0.5), so might require higher doses of captopril during acute coronary insult. The AT1R gene (rs275651) AA genotype was associated with UA (O.R = 1.3, P = 0.9). AA and AT genotypes were more prone to have PCI after ACS attack (O.R = 3.9 P = 0.2, O.R = 3.5, P = 0.3 respectively) and thus requiring higher doses of captopril. We conclude that the AT1R rs5186, rs275651 genetic polymorphisms might partially affect the clinical outcome of ACS patients treated with captopril and might have captopril resistance which requires higher doses.  相似文献   
56.
Multilevel bifactor item response theory (IRT) models are commonly used to account for features of the data that are related to the sampling and measurement processes used to gather those data. These models conventionally make assumptions about the portions of the data structure that represent these features. Unfortunately, when data violate these models' assumptions but these models are used anyway, incorrect conclusions about the cluster effects could be made and potentially relevant dimensions could go undetected. To address the limitations of these conventional models, a more flexible multilevel bifactor IRT model that does not make these assumptions is presented, and this model is based on the generalized partial credit model. Details of a simulation study demonstrating this model outperforming competing models and showing the consequences of using conventional multilevel bifactor IRT models to analyze data that violate these models' assumptions are reported. Additionally, the model's usefulness is illustrated through the analysis of the Program for International Student Assessment data related to interest in science.  相似文献   
57.
In Chapter V of his autobiography, John Stuart Mill describes the ‘crisis in my mental history’ that cast this brilliant mind into profound gloom at age 20. Mill makes clear that his plight had everything to do with the extraordinary analytical and critical education imparted to him by his father. That which prompts Mill's deep distress, as well as that which is necessary in order to escape it, are the central concern of Michael Polanyi's monumental Personal Knowledge. The thesis of this essay is that Polanyi in his book offers a penetrating analysis of the disorder from which Mill suffered and, even more significantly, Polanyi explains more perceptively than does Mill himself what is required in order to resolve the mental crisis and establish what both authors refer to as ‘balance’ of mind.  相似文献   
58.
Research in Higher Education - State financial aid grant programs are commonly categorized as either need-based, merit-based, or both, but their initial eligibility requirements include many more...  相似文献   
59.
Magnetic-inertial measurement units (MIMUs) are becoming more prevalent in sports biomechanics and may be a viable tool to evaluate kinematic parameters. This study examined the accuracy of a MIMU to estimate orientation angles under static conditions and dynamically from a squash racket during a forehand drive shot. A MIMU was mounted onto a goniometer and moved through 0–90°, with static data collected at 10° increments during 10 repetitions of all three axes. Typical error analyses showed the MIMU to be very reliable (TE ≤ 0.03°). MIMU accuracy was determined via intraclass correlation coefficients (ICC) (r > 0.999, p < 0.001). An ordinary least products regression showed no proportional bias and minimal fixed bias for all axes. Dynamic accuracy was assessed by comparing MIMU and optical motion capture data of squash racket swing kinematics. A MIMU was fixed onto a racket and 10 participants each hit 10 forehand shots. Mean orientation angle error at ball impact was <0.50° and ICC showed very high correlations (r ≥ 0.988, p < 0.001) for all orientations. Swing phase root mean squared errors were ≤2.20°. These results indicate that a MIMU could be used to accurately and reliably estimate selected racket swing kinematics.  相似文献   
60.
Abstract

This paper will entail a critical analysis of the relationship between sport science and ethics by analysing various forms of ‘fairness’ rules and policies. The relationship between science and ethics can have an impact on professional careers and competitive balance. The generation and adjudication of some of the more traditional formal rules and policies utilized to authenticate fairness, and thus support prevailing concepts of fair play, will be challenged from a philosophical and feminist perspective.  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