全文获取类型
收费全文 | 2908篇 |
免费 | 51篇 |
国内免费 | 1篇 |
专业分类
教育 | 2173篇 |
科学研究 | 96篇 |
各国文化 | 27篇 |
体育 | 276篇 |
综合类 | 2篇 |
文化理论 | 22篇 |
信息传播 | 364篇 |
出版年
2023年 | 17篇 |
2022年 | 15篇 |
2021年 | 24篇 |
2020年 | 55篇 |
2019年 | 88篇 |
2018年 | 87篇 |
2017年 | 90篇 |
2016年 | 111篇 |
2015年 | 66篇 |
2014年 | 80篇 |
2013年 | 698篇 |
2012年 | 68篇 |
2011年 | 84篇 |
2010年 | 67篇 |
2009年 | 54篇 |
2008年 | 76篇 |
2007年 | 90篇 |
2006年 | 67篇 |
2005年 | 50篇 |
2004年 | 48篇 |
2003年 | 40篇 |
2002年 | 44篇 |
2001年 | 43篇 |
2000年 | 56篇 |
1999年 | 38篇 |
1998年 | 23篇 |
1997年 | 31篇 |
1996年 | 32篇 |
1995年 | 29篇 |
1994年 | 30篇 |
1993年 | 46篇 |
1992年 | 36篇 |
1991年 | 40篇 |
1990年 | 34篇 |
1989年 | 28篇 |
1988年 | 31篇 |
1987年 | 30篇 |
1986年 | 29篇 |
1985年 | 29篇 |
1984年 | 26篇 |
1983年 | 27篇 |
1982年 | 33篇 |
1981年 | 33篇 |
1980年 | 21篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1977年 | 19篇 |
1976年 | 15篇 |
1975年 | 15篇 |
1972年 | 13篇 |
排序方式: 共有2960条查询结果,搜索用时 250 毫秒
111.
Williams Nwagwu 《Learned Publishing》2005,18(3):200-211
This article maps the biomedical literature of Nigeria by source/origin of publications and authorships from 1967 to 2002. This mapping is expected to provide crucial information to both government and others taking funding and related decisions regarding biomedical research in Nigeria. Data was collected from MEDLINE. Scientists publishing on Nigerian biomedicine have written 6,820 articles in 295 journals/sources. Only eight of the 121 local journals that published biomedical research in Nigeria during the period were included in MEDLINE's listing (2.72%), while there were 32 (10.84%) regional and 255 (86.44%) external journals used. Local journals appeared to be more heavily used than regional and external ones. It was also shown that MEDLINE does not adequately represent Nigeria's biomedical literature. 相似文献
112.
Jane Fedorowicz Janis L. Gogan Christine B. Williams 《Government Information Quarterly》2007,24(4):785
It is increasingly important for government agencies to collaborate across jurisdictional and functional boundaries. Interorganizational systems supporting interagency collaboration must accommodate a wide range of factors from the external environment and participating organizations as part of their design and operation. This paper presents the findings from a case study of CapWIN, a collaborative network created to enable first responders to share information across jurisdictional and functional boundaries as they work together during emergencies and other critical events. The study examines how aspects of the external environment and the agency context impeded or facilitated the CapWIN collaborative network and the interorganizational system (IOS) that supports it. We identify factors affecting information sharing and collaborative processes, and describe how these factors interact to enable and constrain an IOS. The paper concludes with suggestions for further research on the interplay of environmental, organizational, and technical aspects of interagency collaboration networks as they evolve over time. 相似文献
113.
114.
115.
116.
The aims of this study were to examine and compare selected physiological and metabolic responses of wheelchair athletes in two paraplegic racing classes [T3: n = 8 (lesion levels T1-T7; paraplegics); T4: n = 9 (lesion levels below T7; paraplegics)] to prolonged exercise. In addition, we describe the responses of three tetraplegic athletes [T2: n = 3 (lesion levels C6/C7: tetraplegics)]. Twenty athletes completed 90 min of exercise at 75% VO2peak on a motorized treadmill adapted for wheelchairs. The mean (+/- s) heart rates of the T3 and T4 racing classes were 165 +/- 2 and 172 +/- 6 beats.min-1, respectively. For the T4 racing class, heart rate gradually increased during the test (P < 0.05), whereas for the T3 racing class, heart rate reached a plateau after an initial increase. The mean heart rate of the tetraplegics was 114 +/- 3 beats.min-1. The T3 and T4 classes exhibited similar respiratory exchange ratios, plasma lactate and glucose concentrations throughout the test. For both the T3 and T4 racing class, free fatty acid, glycerol, ammonia, urea and potassium concentrations had increased from resting values by the end of the test (P < 0.05). In conclusion, the results of this study suggest that endurance-trained wheelchair athletes are able to maintain velocities equivalent to the same relative exercise intensity (75% VO2peak) for prolonged periods irrespective of lesion level. 相似文献
117.
118.
119.
120.
The aim of this study was to determine the influence of breathing frequency and tidal volume on resting heart rate variability in children aged 9 years (n = 29) and 16 years (n = 19). Heart rate variability was measured in four conditions: (1) without the control of ventilation followed at random by (2) a fixed breathing frequency of 12 breaths x min(-1), (3) a breathing frequency of 12 breaths x min(-1) but with a fixed tidal volume of 30% vital capacity and (4) a fixed breathing frequency of 6 breaths x min(-1) and a tidal volume of 30% vital capacity. A total of 128 RR intervals (the time between two spikes in the heart rate) were detected and absolute high- and low-frequency spectral components were calculated using autoregressive modelling. The younger children were unable to control ventilation to achieve conditions 3 and 4; therefore, a 2 x 2 (group x condition) analysis of variance was used to analyse conditions 1 and 2. There were significant interactions between group and heart rate variability conditions for the low-frequency component and the ratio of low to high frequencies (P < 0.001). The main effect for condition showed that at 12 breaths x min(-1) with no fixed tidal volume there was a significantly higher standard deviation of the RR interval, total power and high-frequency (P< 0.01) and low-frequency spectral components (P < 0.05) than in the condition with no ventilatory control. Across the four breathing conditions for the older participants, the high-frequency spectral component was significantly higher in the condition at 6 breaths x min(-1) with a fixed tidal volume than in that with no ventilatory control (P < 0.005); the ratio of high to low frequencies was significantly lower for the spontaneous condition than those performed at 12 breaths x min(-1) (P < 0.001). The results provide evidence of the need for ventilatory control when assessing short-term resting heart rate variability in children. 相似文献