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   3568篇
  免费   35篇
  国内免费   6篇
教育   2217篇
科学研究   497篇
各国文化   24篇
体育   279篇
综合类   8篇
文化理论   45篇
信息传播   539篇
  2022年   24篇
  2021年   25篇
  2020年   44篇
  2019年   58篇
  2018年   113篇
  2017年   163篇
  2016年   140篇
  2015年   89篇
  2014年   109篇
  2013年   539篇
  2012年   123篇
  2011年   143篇
  2010年   117篇
  2009年   86篇
  2008年   79篇
  2007年   114篇
  2006年   62篇
  2005年   77篇
  2004年   65篇
  2003年   61篇
  2002年   53篇
  2001年   87篇
  2000年   70篇
  1999年   61篇
  1998年   56篇
  1997年   47篇
  1996年   51篇
  1995年   25篇
  1994年   33篇
  1993年   20篇
  1992年   46篇
  1991年   44篇
  1990年   30篇
  1989年   38篇
  1988年   34篇
  1987年   31篇
  1986年   35篇
  1985年   39篇
  1984年   38篇
  1983年   22篇
  1982年   33篇
  1981年   24篇
  1980年   16篇
  1979年   35篇
  1978年   30篇
  1977年   21篇
  1976年   16篇
  1974年   21篇
  1972年   25篇
  1971年   19篇
排序方式: 共有3609条查询结果,搜索用时 15 毫秒
151.
The aim of this study was to investigate, for typical shoes and surfaces used in tennis, the relative role of the shoe and surface in providing cushioning during running. Five test surfaces ranging from concrete to artificial turf were selected, together with two shoe models. Impact absorbing ability was assessed mechanically using drop test procedures and biomechanically using peak magnitude and rate of loading of impact force and peak in-shoe pressure data at the lateral heel. Differences in biomechanical variables between shoe-surface combinations were identified using a two-way ANOVA (p < 0.05). Mechanical test results were found to rank the surfaces in the same order regardless of the shoe model, suggesting that the surface is influential in providing cushioning. However, for all mechanical and biomechanical (p < 0.05) variables representing impact absorbing ability, it was found that the difference between shoes was markedly greater than the differences between surfaces. The peak heel pressure data were found to rank the surfaces in the same order as the mechanical tests, while impact force data were not as sensitive to the changes in surface. Correlations between mechanical and biomechanical impact absorption highlighted the importance of testing the shoe-surface combination in mechanical tests, rather than the surface alone. In conclusion, mechanical testing of the shoe-surface combination was found to provide a strong predictor of the impact absorbing ability during running if pressure data were used. In addition, for typical shoe-surface combinations in tennis, the shoe was found to have more potential than the surface to influence impact loading during running. Finally, in-shoe pressure data were found to be more sensitive than force plate data to changes in material cushioning.  相似文献   
152.
Mick E  Biederman J  Faraone SV 《Journal of learning disabilities》2000,33(4):314; author reply 314-314; author reply 316
  相似文献   
153.
Abstract

Research concerned with predictors of talent in football has highlighted a number of potentially important and partially inherited measures such as body size, anaerobic power, aerobic capacity, agility, psychological profile, game intelligence and susceptibility to injuries. Genotyping for performance-associated DNA polymorphisms at an early age could be useful in predicting later success in football. The aim of the study was to investigate individually and in combination the association of common gene polymorphisms with football player’s status. A total of 246 Russian football players and 872 controls were genotyped for 8 gene polymorphisms, which were previously reported to be associated with athlete status. Four alleles (ACE D, ACTN3 Arg577, PPARA rs4253778 C and UCP2 55Val) were first identified, showing discrete associations with football player’s status. Next, we determined the total genotype score (TGS, from the accumulated combination of the 4 polymorphisms, with a maximum value of 100 for the theoretically optimal polygenic score) in athletes and controls. The mean TGS was significantly higher in football players (52.0 (17.6) vs. 41.3 (15.5); P < 0.0001) than in controls. These data suggest that the likelihood of becoming a football player depends on the carriage of a high number of “favourable” gene variants.  相似文献   
154.
155.
In Information Retrieval, since it is hard to identify users’ information needs, many approaches have been tried to solve this problem by expanding initial queries and reweighting the terms in the expanded queries using users’ relevance judgments. Although relevance feedback is most effective when relevance information about retrieved documents is provided by users, it is not always available. Another solution is to use correlated terms for query expansion. The main problem with this approach is how to construct the term-term correlations that can be used effectively to improve retrieval performance. In this study, we try to construct query concepts that denote users’ information needs from a document space, rather than to reformulate initial queries using the term correlations and/or users’ relevance feedback. To form query concepts, we extract features from each document, and then cluster the features into primitive concepts that are then used to form query concepts. Experiments are performed on the Associated Press (AP) dataset taken from the TREC collection. The experimental evaluation shows that our proposed framework called QCM (Query Concept Method) outperforms baseline probabilistic retrieval model on TREC retrieval.  相似文献   
156.
157.
In this paper, decomposition methods for multidimensional data hypercubes of OLAP systems are investigated. Criteria for reducing the computational complexity of the decomposition methods are presented and comparisons are made with the traditional solutions of multidimensional data analysis problems. Examples illustrating the application of these criteria to investigating the dynamics of computational complexity changes for specific types of reduction problems are considered.  相似文献   
158.
Handedness has been studied for association with language-related disorders because of its link with language hemispheric dominance. No clear pattern has emerged, possibly because of small samples, publication bias, and heterogeneous criteria across studies. Non-right-handedness (NRH) frequency was assessed in N = 2503 cases with reading and/or language impairment and N = 4316 sex-matched controls identified from 10 distinct cohorts (age range 6–19 years old; European ethnicity) using a priori set criteria. A meta-analysis (Ncases = 1994) showed elevated NRH % in individuals with language/reading impairment compared with controls (OR = 1.21, CI = 1.06–1.39, p = .01). The association between reading/language impairments and NRH could result from shared pathways underlying brain lateralization, handedness, and cognitive functions.  相似文献   
159.
Abstract

Purpose: The purpose of this study was to identify and rank the SWOT issues of India's veterinary and animal science education.

Design: The data were collected at the Indian Veterinary Research Institute (IVRI) from 168 post-graduate students. The two surveys generated 72% (N=121) and 68% (N=114) response rates, respectively. In the first stage, the vital SWOT issues were listed by respondents and in the second stage, they ranked the top eight issues on a Likert scale.

Findings: Uniform curriculum; merit-based admissions; and huge demand and employment prospects were perceived as major strengths. Gaps in curriculum revision and inadequate faculty, colleges and hands-on experience were perceived as key weaknesses. Regular curriculum revisions; novel instructional methods; and single admission tests were important opportunities perceived. Out-dated education model; urban biased admissions; and regional barriers were the major threats perceived.

Practical implication: The SWOT issues identified are similar to those faced by veterinary education programmes in many countries with minor variations.

Originality/value: The findings are of interest for veterinary faculties in developing and under-developed countries to harmonize their veterinary education systems on par with global norms. The related implications for policy and future directions are discussed.  相似文献   
160.
The purpose of this study was to determine the effects of short-term normoxic and hypoxic exercise on plasma endothelin-1 and nitric oxide levels, and the relationship of arterial compliance and pulmonary artery pressure to endothelin-1. Seven endurance-trained males completed two incremental and two steady-state exercise tests performed at ventilatory threshold in normoxia and hypoxia (fraction of inspired oxygen = 0.14). Plasma endothelin-1was measured throughout steady-state tests. Arterial compliance using applanation tonometry, plasma nitric oxide and pulmonary artery pressure using Doppler echocardiography were measured before and after exercise. Small arterial compliance and pulmonary artery pressure significantly increased following exercise. There were no main effects of condition or time for plasma endothelin-1and nitric oxide levels. There were no significant relationships between plasma endothelin-1 and arterial compliance or pulmonary artery pressure. In conclusion, mechanisms other than the endothelial system may play a role in the exercise-induced changes in small artery compliance in this study population. Moderate hypoxia and a 30-minute steady-state exercise have limited effects on plasma endothelin-1 in endurance-trained males.  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