全文获取类型
收费全文 | 18785篇 |
免费 | 251篇 |
国内免费 | 7篇 |
专业分类
教育 | 13786篇 |
科学研究 | 1748篇 |
各国文化 | 125篇 |
体育 | 1278篇 |
综合类 | 15篇 |
文化理论 | 154篇 |
信息传播 | 1937篇 |
出版年
2021年 | 145篇 |
2020年 | 218篇 |
2019年 | 365篇 |
2018年 | 528篇 |
2017年 | 613篇 |
2016年 | 620篇 |
2015年 | 394篇 |
2014年 | 430篇 |
2013年 | 3117篇 |
2012年 | 517篇 |
2011年 | 602篇 |
2010年 | 361篇 |
2009年 | 306篇 |
2008年 | 447篇 |
2007年 | 339篇 |
2006年 | 388篇 |
2005年 | 887篇 |
2004年 | 684篇 |
2003年 | 506篇 |
2002年 | 377篇 |
2001年 | 399篇 |
2000年 | 354篇 |
1999年 | 302篇 |
1998年 | 147篇 |
1997年 | 174篇 |
1996年 | 194篇 |
1995年 | 191篇 |
1994年 | 154篇 |
1993年 | 167篇 |
1992年 | 242篇 |
1991年 | 218篇 |
1990年 | 212篇 |
1989年 | 248篇 |
1988年 | 246篇 |
1987年 | 211篇 |
1986年 | 204篇 |
1985年 | 221篇 |
1984年 | 191篇 |
1983年 | 230篇 |
1982年 | 172篇 |
1981年 | 162篇 |
1980年 | 159篇 |
1979年 | 229篇 |
1978年 | 183篇 |
1977年 | 165篇 |
1976年 | 151篇 |
1975年 | 128篇 |
1974年 | 119篇 |
1973年 | 126篇 |
1971年 | 106篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Cerebral activity, as reflected by power in the alpha waveband (8-13 Hz), was examined prior to the performance of three tasks with different effort and accuracy requirements. The study aimed to further investigate changes in activity observed in an earlier study in which expert karate performers exhibited significant increases in alpha band power during preparation for a training task. In contrast to the earlier research, the high effort task produced a significant decrease in 'alpha' power prior to performance. 'Alpha' power prior to the high accuracy task showed significant differences mediated by the outcome. Successful performance was preceded by higher levels of 'alpha' power than unsuccessful attempts. The reported use of a cognitive strategy on the first task produced a significant difference in activity, lower alpha power being associated with the use of such a technique. 相似文献
32.
D A Sedlock 《Research quarterly for exercise and sport》1991,62(2):213-216
This study was designed to examine the magnitude and duration of excess postexercise oxygen consumption (EPOC) following upper body exercise, using lower body exercise for comparison. On separate days and in a counterbalanced order, eight subjects (four male and four female) performed a 20-min exercise at 60% of mode-specific peak oxygen uptake (VO2) using an arm crank and cycle ergometer. Prior to each exercise, baseline VO2 and heart rate (HR) were measured during the final 15 min of a 45-min seated rest. VO2 and HR were measured continuously during the postexercise period until baseline VO2 was reestablished. No significant difference between the two experimental conditions was found for magnitude of EPOC (t [7] = 0.69, p greater than .05). Mean (+/- SD) values were 9.2 +/- 3.3 and 10.4 +/- 5.8 kcal for the arm crank and cycle ergometer exercises, respectively. Duration of EPOC was relatively short and not significantly different (t [7] = 0.24, p greater than .05) between the upper body (22.9 +/- 13.7 min) and lower body (24.2 +/- 19.4 min) exercises. Within the framework of the chosen exercise conditions, these results suggest EPOC may be related primarily to the relative metabolic rate of the active musculature, as opposed to the absolute exercise VO2 or quantity of active muscle mass associated with these two types of exercise. 相似文献
33.
Data from the International Social Survey Program indicate considerablevariation in the desire of respondents for increased spendingon the environment in Australia, Austria, Great Britain, theUnited States, and West Germany. This paper explores this variationwith the following objectives: (1) to determine the extent towhich the social bases of environmental concern are consistentacross nations; (2) to determine how the issue of the environmenthas been politicized in the five industrialized nations, focusingon the association of Old Leftist concerns and environmentalconcern; and (3) to determine the extent to which the socialbases of environmental concern can explain the cross-nationalvariation. The study usesa regression analysis, testing variablesrepresenting the social bases of environmental concern frompast research in the United States, a scale representing commitmentto the platform of the Old Left, and dummy variables for eachcountry. The results show that the social bases of environmentalconcern are the same in the five countries studied, includinga consistent positive association of Old Leftism with environmentalconcern. However, substantial variation between countries inthe overall level of concern remains. Potential sources of theremaining variation are examined. 相似文献
34.
35.
36.
The purpose of this investigation was to describe the morphological parameters that characterize elite age group divers. Comparisons are made to normative age group data from the Coquitlam Growth Study and the constancy of important characteristics from age group to age group is examined. Data were collected on 27 male and 28 female elite divers who participated in the 1990 North American Age Group Diving Championships. Body build, body composition and skinfold corrected diameters were determined from 36 anthropometric parameters and analysed by ANOVA, t-test and Phantom z-scores procedures. All age groups except the 14- to 15-year-old males were significantly (P < or = 0.05) shorter than their norms but recorded higher androgyny index values. The estimated relative muscle mass increased significantly (P < or = 0.05) with age for males at all ages (40.8-46.3%). The 16- to 18-year-old females had a significantly (P < or = 0.05) larger relative muscle component compared to the younger age groups (40.1-38.4%). When normalized for height, active tissue development of the extremities was comparable between the sexes except in the forearm. The results indicate that at all age levels short stature is an important characteristic for divers. Analysis of regional active tissue development provides further insight into sport-specific prerequisites for success at elite levels. 相似文献
37.
38.
Zusammenfassung. Die automatische Erkennung und Lokalisation von Objekten in digitalen Bildern ist ein wesentlicher Bestandteil vieler praktisch
relevanter Anwendungen. In diesem Artikel wird ein erscheinungsbasiertes Verfahren zur Erkennung starrer zwei- oder dreidimensionaler
Objekte vorgestellt, dem eine statistische Modellierung zugrundeliegt. Im Gegensatz zu segmentierungsbasierten Verfahren,
wie sie vor allem im Bereich der 3D-Objekterkennung eingesetzt werden, erm?glicht der erscheinungsbasierte Ansatz aufgrund
der Modellierung der Intensit?tswerte oder davon abgeleiteter lokaler Merkmale eines Bildes die Erkennung komplexer Objekte.
Die statistische Formulierung der Problemstellung bildet den mathematischen Kontext zur Bestimmung optimaler L?sungen.
Die Form der Modellierung erlaubt neben der Einzelobjekterkennung auch die Berücksichtigung von heterogenem Bildhintergrund
und Mehrobjektszenen. Die dazu ben?tigten lokalen Merkmale entstehen durch r?umlich begrenzte Transformationen des Bildes,
wie beispielsweise Gabor- oder Wavelet-Transformationen. Die statistische Modellierung beschreibt die Verteilung dieser lokalen
Merkmale anhand einer Dichtefunktion, die sich bei der Hintergrund- und Mehrobjektmodellierung als Mischungsverteilung der
Einzelobjektverteilungen ergibt. Die Aufgabenstellungen des Erlernens und Erkennens von Objekten sind damit als Parametersch?tzprobleme
formal darstellbar. Dabei werden im einen Fall die Modellparameter und im anderen Fall die Lageparameter beziehungsweise die
Klassen von Objekten gesch?tzt. Die experimentelle überprüfung des Ansatzes anhand realer Objektaufnahmen durch CCD-Kameras
zeigt seine Brauchbarkeit zur Erkennung von 2D- und 3D-Objekten bei homogenem und heterogenem Hintergrund.
Eingegangen am 5. April 2000 / Angenommen am 20. Juli 2001 相似文献
39.
E. Jennifer Monaghan 《Publishing Research Quarterly》1994,10(1):28-46
Between 1880 and 1950, the role of women as authors of elementary readers flowered and faded. From 1880 to 1915, female authorship
dominated. Over the next fifteen years female authorship withstood the challenge of the scientific movement in education.
Women’s role as solo authors declined, however, during the Depression, World War II and the postwar years. These changes are
explained by the deteriorating environment for female professionalism, changes in the concept of reading expertise, the expanded
role of publishers in textbook development, and the differences between men and women in opportunities for graduate study.
E. Jennifer is Monaghan a professor in the Department of Educational Services, Brooklyn College of the City University of
New York. She is the founder of the History of Reading Special Interest Group of the International Reading Association and
author ofA Common Heritage: Noah Webster’s Blue-Back Speller. 相似文献
40.