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   14332篇
  免费   181篇
  国内免费   22篇
教育   10045篇
科学研究   1583篇
各国文化   134篇
体育   1199篇
综合类   7篇
文化理论   105篇
信息传播   1462篇
  2021年   141篇
  2020年   198篇
  2019年   275篇
  2018年   379篇
  2017年   360篇
  2016年   369篇
  2015年   245篇
  2014年   329篇
  2013年   2526篇
  2012年   313篇
  2011年   334篇
  2010年   299篇
  2009年   235篇
  2008年   288篇
  2007年   264篇
  2006年   241篇
  2005年   218篇
  2004年   240篇
  2003年   217篇
  2002年   194篇
  2001年   461篇
  2000年   303篇
  1999年   264篇
  1998年   129篇
  1997年   168篇
  1996年   153篇
  1995年   136篇
  1994年   159篇
  1993年   132篇
  1992年   193篇
  1991年   209篇
  1990年   203篇
  1989年   216篇
  1988年   174篇
  1987年   171篇
  1986年   172篇
  1985年   215篇
  1984年   169篇
  1983年   161篇
  1982年   144篇
  1981年   130篇
  1980年   126篇
  1979年   176篇
  1978年   143篇
  1977年   127篇
  1976年   101篇
  1975年   119篇
  1974年   111篇
  1973年   120篇
  1971年   108篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
51.
Starting from the notion of h-type indices for infinite sequences we investigate if these indices satisfy natural inequalities related to the arithmetic, the geometric and the harmonic mean. If f denotes an h-type index, such as the h- or the g-index, then we investigate inequalities such as min(f(X),f(Y)) ≤ f((X?+?Y)/2) ≤ max(f(X), f(Y)). We further investigate if: f(min(X,Y)) = min(f(X),f(Y)) and if f(max(X,Y)) = max(f(X),f(Y)). It is shown that the h-index satisfies all the equalities and inequalities we investigate but the g-index does not always, while it is always possible to find a counterexample involving the R-index. This shows that the h-index enjoys a number of interesting mathematical properties as an operator in the partially ordered positive cone (R+) of all infinite sequences with non-negative real values.In a second part we consider decreasing vectors X and Y with components at most at distance d. Denoting by D the constant sequence (d,d,d, …) and by Y-D the vector (max(yr-d), 0)r, we prove that under certain natural conditions, the double inequality h(Y-D) ≤ h(X) ≤ h(Y?+?D) holds.  相似文献   
52.
Background: Somali Bantu refugees, with unique health information needs, created challenges for health and social service providers. Objectives: A service innovation was developed (i) to raise awareness, especially among local health and social service providers, about the Bantu refugees’ presence in the community, their culture, and their information needs and (ii) to deliver needed health information, emphasizing child health, to the Bantu mothers in their homes. Methods: The project consisted of: (i) a community conference targeting local health and social service providers, describing the refugees’ presence in the community, their culture, and information needs. (ii) Focus groups conducted with members of the Bantu population elicited additional information needs. (iii) Curriculum was developed based on identified needs, and (iv) the curriculum was delivered to the refugees in their homes. A clinical informationist and MP3 technology enhanced the project. Findings: Conference attendees’ evaluation responses indicated improved understanding of Bantu culture. Focus groups’ identification of health information needs provided a framework for the health education curriculum. A project website made educational materials available to other healthcare providers. Conclusions: The project raised awareness of the Bantus’ presence, culture, and information needs. Identification of other unmet needs demonstrated that additional support for refugees is required.  相似文献   
53.
网络信息检索中,逻辑运算符AND连接检索词的顺序很大程度上会影响检索效率.论文首先分析、介绍了the Staceys测度方法在改善AND检索效率中发挥的作用,并在此基础上提出简化了的测度算法,最后通过实例说明其实现步骤.  相似文献   
54.
This study investigated whether a relationship existed between instructional style and points of emphasis in the training context of the martial art aikido and the perceptions which practitioners of aikido generated for aikido-related concepts. The findings were gathered within and compared across aikido training settings in two cultures — Japan and the United States. Analysis of the quantitative and qualitative data gathered for this investigation revealed several potent differences between the manner in which Japanese and American aikido practitioners represented their understandings of aikido-related concepts. Differences in the manner in which aikido practitioners in Japan and the United States represented their understandings of aikido reflected the teaching emphasis observed in the respective cultures. It was concluded that aikido instructors represented the values of their own culture in the context of aikido training, and thus served as important mediating forces influencing the meaning which practitioners generated for aikido. An additional finding revealed that in neither culture were participants able to accurately represent how practitioners in the “other” culture structured their understandings of aikido. It was reasoned that both cultural groups generated faulty perceptions of how the “other” group understood aikido because they utilized a similar pattern of projection, using their own meanings of aikido to represent the understandings of practitioners in the “other” cultural group.  相似文献   
55.
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   
56.
The purpose of this study was to examine if steps/day taken by middle school students varied based on aerobic fitness classification. Middle school students (N = 223; 112 girls, 111 boys) were assigned to three aerobic fitness categories (HIGH, MOD, LOW) based on results of the FlTNESSGRAM PACER test. Four weekdays of pedometer monitoring determined activity levels (steps/day). Boys accumulated significantly more steps/day than girls, 11,589 +/- 3,270 and 10,232 +/- 2,517 steps/day, respectively; F(1,219) = 16.0, p < .001, eta2 = .055. There were no differences in steps/day between grades. HIGH fit participants accumulated significantly more steps/day, F(2, 217) = 12.2, p < .101, eta2 = .101, than moderately fit and low fit participants (approximately 1,491 and ; 2,867 steps/day, respectively). Middle school students who participated in sports in addition to physical education (PE) accumulated significantly more steps/day (approximately 980 steps/day) than those participating in PE only, F(1, 219) = 10.0, p < .01, eta2 = .044. Although the relationship between physical activity and aerobic fitness was moderate (0.35; p < .01), these data demonstrated significant differences in accumulated steps/day among youth of varying aerobic fitness levels. Whether improved fitness levels were the result of additional activity or the cause of it remains to be determined. Regardless, the fittest middle school students were also the most active and accumulated a significant amount of steps/day through organized extracurricular physical activities.  相似文献   
57.
58.
This paper proposes an extended definition of reciprocity for a multiport junction structure based on the concept of essential gyrator coupling. Two theorems are given for junction structures containing gyrators and an algorithm is presented for identifying essential gyrators. The results are useful both theoretically and for designing efficient computation procedures for junction structures.  相似文献   
59.
Necessary and sufficient conditions are obtained for the realization of an m-variable positive real function (PRF) as the impedence function of a resistively-terminated ladder network of m lossless two-ports connected in cascade. Each two-port is a single-variable lossless ladder with all of its transmission zeros either at the origin or at finity. Conditions are also obtained when each of the two-ports is a Fujisawa-type lowpass ladder.  相似文献   
60.
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