全文获取类型
收费全文 | 22350篇 |
免费 | 279篇 |
国内免费 | 25篇 |
专业分类
教育 | 15888篇 |
科学研究 | 2160篇 |
各国文化 | 168篇 |
体育 | 1961篇 |
综合类 | 13篇 |
文化理论 | 175篇 |
信息传播 | 2289篇 |
出版年
2021年 | 170篇 |
2020年 | 270篇 |
2019年 | 413篇 |
2018年 | 570篇 |
2017年 | 592篇 |
2016年 | 534篇 |
2015年 | 340篇 |
2014年 | 479篇 |
2013年 | 4108篇 |
2012年 | 480篇 |
2011年 | 533篇 |
2010年 | 383篇 |
2009年 | 355篇 |
2008年 | 479篇 |
2007年 | 409篇 |
2006年 | 457篇 |
2005年 | 341篇 |
2004年 | 316篇 |
2003年 | 324篇 |
2002年 | 346篇 |
2001年 | 444篇 |
2000年 | 413篇 |
1999年 | 398篇 |
1998年 | 193篇 |
1997年 | 224篇 |
1996年 | 267篇 |
1995年 | 244篇 |
1994年 | 227篇 |
1993年 | 239篇 |
1992年 | 356篇 |
1991年 | 337篇 |
1990年 | 325篇 |
1989年 | 364篇 |
1988年 | 342篇 |
1987年 | 304篇 |
1986年 | 324篇 |
1985年 | 332篇 |
1984年 | 288篇 |
1983年 | 343篇 |
1982年 | 268篇 |
1981年 | 251篇 |
1980年 | 242篇 |
1979年 | 378篇 |
1978年 | 273篇 |
1977年 | 261篇 |
1976年 | 244篇 |
1975年 | 202篇 |
1974年 | 196篇 |
1973年 | 175篇 |
1971年 | 168篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
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
993.
The power output achieved at peak oxygen consumption (VO2peak) and the time this power can be maintained (i.e., Tmax) have been used in prescribing high-intensity interval training. In this context, the present study examined temporal aspects of the VO2 response to exercise at the cycling power that output well trained cyclists achieve their VO2peak (i.e., Pmax). Following a progressive exercise test to determine VO2peak, 43 well trained male cyclists (M age = 25 years, SD = 6; M mass = 75 kg, SD = 7; M VO2peak = 64.8 ml x kg(-1) x min(-1), SD = 5.2) performed two Tmax tests 1 week apart. Values expressed for each participant are means and standard deviations of these two tests. Participants achieved a mean VO2peak during the Tmax test after 176 s (SD = 40; M = 74% of Tmax, SD = 12) and maintained it for 66 s (SD = 39; M = 26% of Tmax, SD = 12). Additionally, they obtained mean 95% of VO2peak after 147 s (SD = 31; M = 62% of Tmax, SD = 8) and maintained it for 95 s (SD = 38; M = 38% of Tmax, SD = 8). These results suggest that 60-70% of Tmax is an appropriate exercise duration for a population of well trained cyclists to attain VO2peak during exercise at Pmax. However, due to intraparticipant variability in the temporal aspects of the VO2 response to exercise at Pmax, future research is needed to examine whether individual high-intensity interval training programs for well trained endurance athletes might best be prescribed according to an athlete's individual VO2 response to exercise at Pmax. 相似文献
994.
Detlefsen EG 《Medical reference services quarterly》2004,23(4):87-94
The article describes an innovation in MLIS education for medical librarianship, with an introduction to the FastTrack, the distance education program at the University of Pittsburgh's library and information science school, together with an overview of a model program linking the biomedical library at Vanderbilt University with the School of Information Sciences in Pittsburgh. Admissions requirements and specific curriculum for the distance education master's degree are detailed in an FAQ format. 相似文献
995.
Brian S Alper Jason A Hand Susan G Elliott Scott Kinkade Michael J Hauan Daniel K Onion Bernard M Sklar 《Journal of the Medical Library Association》2004,92(4):429-437
OBJECTIVES: Medicine must keep current with the research literature, and keeping current requires continuously updating the clinical knowledge base (i.e., references that provide answers to clinical questions). The authors estimated the volume of medical literature potentially relevant to primary care published in a month and the time required for physicians trained in medical epidemiology to evaluate it for updating a clinical knowledge base. METHODS: We included journals listed in five primary care journal review services (ACP Journal Club, DynaMed, Evidence-Based Practice, Journal Watch, and QuickScan Reviews). Finding little overlap, we added the 2001 "Brandon/Hill Selected List of Print Books and Journals for the Small Medical Library." We counted articles (including letters, editorials, and other commentaries) published in March 2002, using bibliographic software where possible and hand counting when necessary. For journals not published in March 2002, we reviewed the nearest issue. Five primary care physicians independently evaluated fifty randomly selected articles and timed the process. RESULTS: The combined list contained 341 currently active journals with 8,265 articles. Adjusting for publication frequency, we estimate 7,287 articles are published monthly in this set of journals. Physicians trained in epidemiology would take an estimated 627.5 hours per month to evaluate these articles. CONCLUSIONS: To provide practicing clinicians with the best current evidence, more comprehensive and systematic literature surveillance efforts are needed. 相似文献
996.
997.
998.
999.
1000.