全文获取类型
收费全文 | 28596篇 |
免费 | 425篇 |
国内免费 | 74篇 |
专业分类
教育 | 20624篇 |
科学研究 | 2576篇 |
各国文化 | 291篇 |
体育 | 2173篇 |
综合类 | 50篇 |
文化理论 | 174篇 |
信息传播 | 3207篇 |
出版年
2021年 | 298篇 |
2020年 | 401篇 |
2019年 | 590篇 |
2018年 | 809篇 |
2017年 | 846篇 |
2016年 | 807篇 |
2015年 | 522篇 |
2014年 | 733篇 |
2013年 | 5416篇 |
2012年 | 700篇 |
2011年 | 736篇 |
2010年 | 645篇 |
2009年 | 587篇 |
2008年 | 658篇 |
2007年 | 603篇 |
2006年 | 615篇 |
2005年 | 545篇 |
2004年 | 453篇 |
2003年 | 427篇 |
2002年 | 383篇 |
2001年 | 753篇 |
2000年 | 540篇 |
1999年 | 460篇 |
1998年 | 264篇 |
1997年 | 295篇 |
1996年 | 293篇 |
1995年 | 246篇 |
1994年 | 281篇 |
1993年 | 236篇 |
1992年 | 373篇 |
1991年 | 360篇 |
1990年 | 399篇 |
1989年 | 384篇 |
1988年 | 325篇 |
1987年 | 321篇 |
1986年 | 337篇 |
1985年 | 360篇 |
1984年 | 322篇 |
1983年 | 302篇 |
1982年 | 247篇 |
1981年 | 251篇 |
1980年 | 231篇 |
1979年 | 335篇 |
1978年 | 277篇 |
1977年 | 222篇 |
1976年 | 208篇 |
1975年 | 209篇 |
1974年 | 193篇 |
1973年 | 202篇 |
1971年 | 201篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
Two experiments were conducted to further examine the effects of reduced knowledge of results (KR) frequency on the learning of motor skills during constant practice. In Experiment 1, participants in five KR conditions (100% KR, 50% KR-fade, 50% KR-reverse fade, 50% KR-alternative, and 50% KR-random) practiced a movement timing task. In Experiment 2, participants in two KR conditions (100% KR and 50% KR-fade) practiced a waveform reproduction task. The results of both experiments failed to indicate that reduced KR frequency was more effective in promoting learning than the 100% KR conditions. The present study adds to the increasing number of experiments that do not find a benefit of reduced KR frequency on learning in constant practice. 相似文献
992.
Shams ML 《Medical reference services quarterly》1999,18(2):63-80
All living organisms are affected by natural or induced modifications of their surrounding physical environment. A distinct relationship exists between the health of the environment and the health of the individuals living in it. This paper presents a selection of resources about environmental health resources readily accessible on the Internet in October 1998. 相似文献
993.
LaBeause J Van de Water N Carey P Fielder M Sorrow B Woolbright C 《Medical reference services quarterly》1999,18(2):81-89
Health sciences librarians are being called upon to be more proactive in their institutions' continuing education efforts. In an effort to identify whether search requests indicated CE needs, a study was conducted by a group of members of GaIN (Georgia Interactive Network for Medical Information). MEDLINE requests from health care professionals for subject specific clinical topics were collected during a six-month period via a standard search request form created for the study. Copies of all completed requests were collected and broad ICD-9 codes assigned to the search topics. Institutional reports were generated for each participating library to share with hospital CE coordinators. They were also compiled for the group as a whole, and reflected the "hottest" topics requested during the study period for physicians and for non-physicians (nurses, allied health, administrators). A survey to hospital librarians and CE educators showed some value in the reports, but greater potential for further collaboration between librarians and CE coordinators. 相似文献
994.
995.
Malachy P McHugh Timothy F Tyler Scott C Greenberg Gilbert W Gleim 《Journal of sports sciences》2002,20(2):83-91
Previous studies analysing electromyograms (EMGs) from indwelling electrodes have indicated that fast-twitch motor units are selectively recruited for low-intensity eccentric contractions. The aim of this study was to compare the frequency content of surface EMGs from quadriceps muscles during eccentric and concentric contractions at various contraction intensities. Electromyograms were recorded from the rectus femoris, vastus lateralis and vastus medialis muscles of 10 men during isokinetic (1.05 rad x s(-1)) eccentric and concentric knee extension contractions at 25%, 50%, 75% and 100% of maximal voluntary contraction (MVC) for each contraction mode. Additionally, isometric contractions (70 degrees) were performed at each intensity. The mean frequency and root mean square (RMS) of the surface EMG were computed. Mean frequency was higher for eccentric than concentric contractions at 25% (P < 0.01), 50% (P < 0.01) and 75% (P < 0.05) but not at 100% MVC. It increased with increasing contraction intensity for isometric (P < 0.001) and concentric (P < 0.01) contractions but not for eccentric contractions (P = 0.27). The EMG amplitude (RMS) increased with increasing contraction intensity similarly in each contraction mode (P < 0.0001). Higher mean frequencies for eccentric than concentric contractions at submaximal contraction intensities is consistent with more fast-twitch motor units being active during eccentric contractions. 相似文献
996.
The MELVYL MEDLINE project resulted in the addition of a full five-year subset of MEDLINE to the University of California's (UC) MELVYL online union catalog. As one of the nation's largest MEDLINE end-user searching systems, MELVYL MEDLINE provides online bibliographic access to the biomedical journal literature for all UC personnel at over seventy library sites or by remote access. This paper summarizes the project's accomplishments, reports MELVYL MEDLINE use and its impact on library services, and provides insights for other end-user search systems. The project serves as a model for adding databases to the MELVYL catalog and demonstrates the potential for use by other disciplines of a specialized database when readily accessible. Evaluation results report high user satisfaction and high usage. However, many advanced searching features of the interface are little used by searchers. Effects on library services include marked increases in reference transactions and interlibrary loans, with significant declines in mediated search services. Future MELVYL MEDLINE enhancements include matching search retrievals to journal locations, linkage to an online document delivery system, and consideration of building a superset of databases by combining MELVYL MEDLINE with citations from another database in the MELVYL catalog. 相似文献
997.
998.
999.
1000.
The effects on retention of adjunct questions either placed at the end of a passage or inserted after their respective paragraphs within the passage were examined. The high school subjects were encouraged to review the materials after encountering the questions, a departure from traditional procedures in the field. Both treatments led to superior retention of the previously questioned facts when compared to a passage-only control group, but did not increase retention of previously unquestioned facts. The position of the adjunct questions did not differentially affect performance. The discrepancy of the results from those traditionally reported are interpreted in terms of the procedures employed. 相似文献