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   251573篇
  免费   39576篇
  国内免费   2272篇
耳鼻咽喉   4450篇
儿科学   5511篇
妇产科学   6025篇
基础医学   26022篇
口腔科学   8287篇
临床医学   40142篇
内科学   53808篇
皮肤病学   7405篇
神经病学   23525篇
特种医学   11483篇
外科学   38556篇
综合类   2268篇
现状与发展   45篇
一般理论   82篇
预防医学   22429篇
眼科学   6359篇
药学   14525篇
中国医学   1614篇
肿瘤学   20885篇
  2024年   587篇
  2023年   5607篇
  2022年   3076篇
  2021年   7473篇
  2020年   7567篇
  2019年   5505篇
  2018年   10984篇
  2017年   10247篇
  2016年   11702篇
  2015年   13286篇
  2014年   16851篇
  2013年   19973篇
  2012年   16120篇
  2011年   15484篇
  2010年   13699篇
  2009年   14782篇
  2008年   12438篇
  2007年   11271篇
  2006年   11680篇
  2005年   9866篇
  2004年   8405篇
  2003年   7174篇
  2002年   6289篇
  2001年   6136篇
  2000年   5121篇
  1999年   4890篇
  1998年   3320篇
  1997年   2837篇
  1996年   2858篇
  1995年   2511篇
  1994年   1811篇
  1993年   1532篇
  1992年   2300篇
  1991年   2191篇
  1990年   1850篇
  1989年   1737篇
  1988年   1644篇
  1987年   1396篇
  1986年   1351篇
  1985年   1170篇
  1984年   887篇
  1983年   855篇
  1982年   621篇
  1981年   571篇
  1980年   453篇
  1979年   582篇
  1978年   526篇
  1977年   503篇
  1976年   425篇
  1974年   431篇
排序方式: 共有10000条查询结果,搜索用时 31 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