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   310331篇
  免费   73075篇
  国内免费   2259篇
耳鼻咽喉   5228篇
儿科学   9001篇
妇产科学   6217篇
基础医学   40093篇
口腔科学   12482篇
临床医学   48436篇
内科学   71741篇
皮肤病学   13898篇
神经病学   33621篇
特种医学   12985篇
外科学   49654篇
综合类   2244篇
现状与发展   45篇
一般理论   101篇
预防医学   25193篇
眼科学   7311篇
药学   19452篇
中国医学   2427篇
肿瘤学   25536篇
  2024年   586篇
  2023年   5588篇
  2022年   3165篇
  2021年   8493篇
  2020年   12161篇
  2019年   15343篇
  2018年   18551篇
  2017年   19013篇
  2016年   20812篇
  2015年   22332篇
  2014年   25927篇
  2013年   29612篇
  2012年   19114篇
  2011年   18585篇
  2010年   20825篇
  2009年   18797篇
  2008年   13892篇
  2007年   11845篇
  2006年   12347篇
  2005年   10315篇
  2004年   8888篇
  2003年   7687篇
  2002年   6888篇
  2001年   6831篇
  2000年   5764篇
  1999年   5110篇
  1998年   3321篇
  1997年   2843篇
  1996年   2868篇
  1995年   2519篇
  1994年   1812篇
  1993年   1534篇
  1992年   2302篇
  1991年   2188篇
  1990年   1844篇
  1989年   1739篇
  1988年   1639篇
  1987年   1391篇
  1986年   1347篇
  1985年   1165篇
  1984年   886篇
  1983年   853篇
  1982年   619篇
  1981年   571篇
  1980年   453篇
  1979年   579篇
  1978年   524篇
  1977年   501篇
  1976年   425篇
  1974年   428篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.

Objective

The aim of the study was to estimate the effect of the state-based reinsurance programs through the section 1332 State Innovation Waivers on health insurance marketplace premiums and insurer participation.

Data Source

2015 to 2022 Robert Wood Johnson Foundation Health Insurance Exchange Compare Datasets.

Study Design

An event study difference-in-differences (DD) model separately for each year of implementation and a synthetic control method (SCM) are used to estimate year-by-year effects following program implementation.

Data Collection/Extraction Methods

Not applicable.

Principal Findings

Reinsurance programs were associated with a decline in premiums in the first year of implementation by 10%–13%, 5%–19%, and 11%–17% for bronze, silver, and gold plans (p < 0.05). There is a trend of sustained declines especially for states that implemented their programs in 2019 and 2020. The SCM analyses suggest some effect heterogeneity across states but also premium declines across most states. There is no evidence that reinsurance programs affected insurer participation.

Conclusion

State-based reinsurance programs have the potential to improve the affordability of health insurance coverage. However, reinsurance programs do not appear to have had an effect on insurer participation, highlighting the need for policy makers to consider complementary strategies to encourage insurer participation.  相似文献   
2.
3.

Physical activity brings significant health benefits to middle-aged adults, although the research to date has been focused on late adulthood. This study aims to examine how ageing affects the self-reported and accelerometer-derived measures of physical activity levels in middle-aged adults. We employed the data recorded in the UK Biobank and analysed the physical activity levels of 2,998 participants (1381 men and 1617 women), based on self-completion questionnaire and accelerometry measurement of physical activity. We also assessed the musculoskeletal health of the participants using the dual-energy X-ray absorptiometry (DXA) measurements provided by the UK Biobank. Participants were categorised into three groups according to their age: group I younger middle-aged (40 to 49 years), group II older middle-aged (50 to 59 years), and group III oldest middle-aged (60 to 69 years). Self-reported physical activity level increased with age and was the highest in group III, followed by group II and I (P?<?0.05). On the contrary, physical activity measured by accelerometry decreased significantly with age from group I to III (P?<?0.05), and the same pertained to the measurements of musculoskeletal health (P?<?0.05). It was also shown that middle-aged adults mostly engaged in low and moderate intensity activities. The opposing trends of the self-reported and measured physical activity levels may suggest that middle-aged adults over-report their activity level as they age. They should be aware of the difference between their perceived and actual physical activity levels, and objective measures would be useful to prevent the decline in musculoskeletal health.

  相似文献   
4.
5.
6.
7.
8.
9.
10.
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