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   2030篇
  免费   28篇
  国内免费   1篇
教育   1499篇
科学研究   102篇
各国文化   32篇
体育   263篇
综合类   1篇
文化理论   48篇
信息传播   114篇
  2023年   22篇
  2022年   33篇
  2021年   57篇
  2020年   94篇
  2019年   145篇
  2018年   184篇
  2017年   170篇
  2016年   157篇
  2015年   96篇
  2014年   107篇
  2013年   467篇
  2012年   78篇
  2011年   56篇
  2010年   48篇
  2009年   42篇
  2008年   33篇
  2007年   30篇
  2006年   31篇
  2005年   20篇
  2004年   20篇
  2003年   14篇
  2002年   22篇
  2001年   12篇
  2000年   11篇
  1999年   9篇
  1998年   10篇
  1997年   5篇
  1996年   11篇
  1995年   7篇
  1994年   6篇
  1993年   6篇
  1992年   6篇
  1991年   7篇
  1990年   9篇
  1989年   5篇
  1988年   4篇
  1983年   2篇
  1979年   1篇
  1977年   2篇
  1976年   1篇
  1975年   2篇
  1973年   1篇
  1970年   1篇
  1969年   1篇
  1966年   1篇
  1964年   1篇
  1963年   2篇
  1962年   1篇
  1960年   2篇
  1959年   1篇
排序方式: 共有2059条查询结果,搜索用时 15 毫秒
991.
The susceptibility to weathering of eleven carbonate and evaporitic Spanish building rocks was studied by means of dissolution experiments. Mineralogy, petrology, geochemistry and porosity of the rocks were also characterized in order to determine the potential relationships between these properties of the rocks and their dissolution rates. Rock slabs were submerged in a 0.1 M HCl acid solution for 72 h and the amounts of Ca, Mg and S released were measured, as well as the weight loss of the samples during the acid attack. Alabasters, which presented very low porosity, were dissolved to a lesser extent than limestones and dolostones in the time of the experiment. A significant positive correlation was found for connected with the weight loss of the rocks during dissolution and with the kinetic rate of Ca dissolution. Overall, the results highlight the influence of the porous network in the degradability of building stones by controlling their rate of dissolution. There is a positive correlation for all the rocks between weight loss along acidic attack and connected porosity, but no relationship between mineralogical and petrographical composition and susceptibility to dissolution.  相似文献   
992.
In the double rank analysis of research publications, the local rank position of a country or institution publication is expressed as a function of the world rank position. Excluding some highly or lowly cited publications, the double rank plot fits well with a power law, which can be explained because citations for local and world publications follow lognormal distributions. We report here that the distribution of the number of country or institution publications in world percentiles is a double rank distribution that can be fitted to a power law. Only the data points in high percentiles deviate from it when the local and world μ parameters of the lognormal distributions are very different. The likelihood of publishing very highly cited papers can be calculated from the power law that can be fitted either to the upper tail of the citation distribution or to the percentile-based double rank distribution. The great advantage of the latter method is that it has universal application, because it is based on all publications and not just on highly cited publications. Furthermore, this method extends the application of the well-established percentile approach to very low percentiles where breakthroughs are reported but paper counts cannot be performed.  相似文献   
993.
Rather than the simple adaptation of a story across different media, cross-media narrative should be defined as that which is transformed by virtue of use a medium and its different languages (film, comics, video games, etc.). This article extends and updates the dimensions of previous cross-media analysis models by underlining narrative aspects of the different products discussed and examining the influence of generic conventions along the way. To test this methodology, the article focuses on a product from the “adventure” genre— the Indiana Jones franchise—which it argues should be seen as a benchmark in the history of this kind of narrative. Special attention is given to the treatment of the character of Indiana Jones, who is the true focal point of the narrative, and to other underlying thematic features.  相似文献   
994.
Sedentary behaviour (SB) is an independent health risk-factor and interrupting SB seems to be beneficial. SB is both defined by posture and intensity, thus objective measurement of postures remains a priority. The ActivPAL inclinometer (AP) has been used as a reference for postural estimation, but information on the validity of the Actigraph inclinometer (AGincl) is scarce. We compared postural estimation from waist-worn AGincl against thigh-worn AP, under free-living. Data from 10 participants (50.4 ± 11.4 years) were used and each 15s-block from 60-valid days was matched for the devices’ comparison. At group level, no differences were found for SB and standing-time between inclinometers (p ≥ 0.05). AGincl underestimated stepping-time by 26.3 min and overestimated SB-to-upright transitions by 200.7 occasions (p < 0.05). Inter-individual variability was higher for SB and standing-time, and AGincl was in better agreement with AP for the stepping-time (area under the ROC curve = 0.98, with 100% sensitivity and 94% specificity; CCC = 0.44). These results highlight potential error in estimating individual postures using AGincl in overweight/obese adults and provide insights on the differences of using specific criteria on data-analysis. Our findings suggest that at the group level, AGincl provides similar estimates compared to AP for SB and standing-time, but not for SB-to-upright transitions or stepping-time. (ClinicalTrials.govID:NCT02007681)  相似文献   
995.
Different methods have been developed to quantify trunk muscle strength and endurance. However, some important protocol characteristics are still unclear, hindering the selection of the most suitable tests in each specific situation. The aim of this study was to examine the reliability and the relationship between 3 representative tests of the most common type of protocols used to assess trunk muscle strength and endurance. Twenty-seven healthy men performed each test twice spaced 1 month apart.Trunk strength and endurance were evaluated with an isokinetic dynamometer and 2 field tests including Biering-Sørensen test and Flexion–rotation trunk test.

All tests showed a good relative consistency (intraclass correlation coefficient [ICC]> 0.75), except for the isokinetic endurance variables which had low–moderate reliability (0.37 < ICC > 0.65). Absolute reliability seemed slightly better in the isokinetic protocol than in the field tests, which showed about 12% of test–retest score increase. No significant correlations were found between test scores.

After a familiarisation period for the field tests, the 3 protocols can be used to obtain reliable measures of trunk muscle strength and endurance. Based on the correlation analysis, these measures are not related, which highlights the importance of selecting the most suitable trunk test for each situation.  相似文献   

996.
Few studies have evaluated resilience in an academic environment as it relates to academic success or failure. This work sought to assess resilience in regular and remedial students of gross anatomy during the first and second semesters of medical school and to correlate this personal trait with academic performance. Two groups of students were compared: the first group included first‐year medical students in the regular course, and the second group included first‐year medical students who did not pass the regular anatomy course and so were enrolled in the remedial course. Both groups completed anonymous surveys designed to gather demographic data and establish scores on the Connor‐Davidson resilience scale, which includes 25 statements rated zero to four on a Likert scale (maximum score 100). The average resilience score was the same for both groups, 80 ± 9. The average anatomy grades differed significantly between regular students (67± 15.0) and remedial students (61 ± 12.0). While there was no overall correlation between resilience score and anatomy grade, regular students with resilience scores of 75 or greater showed slightly better academic performance than their classmates. Similarly, remedial students with resilience scores of 87 or greater faired better academically. Resilience does not predict academic performance in gross anatomy, and further work is necessary to identify those intrinsic and extrinsic factors that influence students' achievements. Anat Sci Educ. © 2010 American Association of Anatomists.  相似文献   
997.
998.
We present the Aula EspaZio Gela, a facility dedicated to teaching Space Science and Technology at the master and doctorate level at the University of the Basque Country (Spain), and to promoting the development of this field in both public and private sectors. The one-year master's degree in Space Science and Technology (60 ECTS (European Credit Transfer and Accumulation System)) offers a group of compulsory courses which give way afterwards to a set of elective matters in which students choose one of two tracks: the scientific, primarily oriented to basic research at the University, or the technological, leading to the space industry and space agencies. After completion of the master thesis, our students have direct access to a PhD in both curricular lines. Here we detail the main features of the master's degree and the experience acquired in three years, including a comparative opinion survey to the students. We also describe the facilities at the Faculty of Engineering consisting of a specific classroom (Aula EspaZio Gela), an Astronomical Observatory, and different laboratories.  相似文献   
999.
Adolescents shift their time of day preferences from morning to evening during puberty when school schedule becomes earlier. Given that a better performance is obtained when individuals are tested at times that are in synchrony with their chronotype, and optimal sleep duration is positively associated with academic performance, evening-types may obtain worse school performance because of both morning school schedule and a decrease of total sleep time. A group of 1133 adolescents (aged 12–16) participated in this study. School performance was evaluated using subjective level of achievement and self-reported grades measures. Controlling for total sleep time, more evening oriented young adolescents (12–14 years) performed significantly worse in school achievement. Girls among 15–16 years performed significantly better than boys. These results have important implications for intervention and prevention programs during school years.  相似文献   
1000.
Acrobatic gymnasts need excellent balance control to execute pyramids where one gymnast is supported by another. The objectives of this study were: (1) to describe balance performance by assessing the centre of pressure displacement in a group of acrobatic gymnasts executing pyramids; (2) to determine the relationship between the parameters describing the centre of pressure oscillations and pyramid score; and (3) to examine the role of each foot in providing a solid base of support to maintain the balance of the pyramid. Sixteen acrobatic gymnasts grouped in pairs performed a Half pyramid and a Straddle pyramid held for 7 s on two force platforms. Path length, variance, range trajectory, and surface area of the centre of pressure of each foot were examined to analyse the balance of the pyramid. The path length was correlated with the pyramid score (Straddle: p = 0.692 [large]; Half: p = 0.407 [moderate]). There were differences in the functions of each leg to maintain balance, with the non-preferred leg supporting a higher weight of the pyramid while the preferred leg performed control movements to maintain balance. The results suggested that quantitative analysis of balance can provide important information on pyramid performance.  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