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   259228篇
  免费   40095篇
  国内免费   2296篇
耳鼻咽喉   4482篇
儿科学   5702篇
妇产科学   7041篇
基础医学   26112篇
口腔科学   8321篇
临床医学   44952篇
内科学   54404篇
皮肤病学   7398篇
神经病学   23803篇
特种医学   11589篇
外科学   39036篇
综合类   2291篇
现状与发展   45篇
一般理论   81篇
预防医学   22990篇
眼科学   6330篇
药学   14553篇
中国医学   1602篇
肿瘤学   20887篇
  2024年   592篇
  2023年   5661篇
  2022年   3118篇
  2021年   7409篇
  2020年   7564篇
  2019年   5487篇
  2018年   11039篇
  2017年   10367篇
  2016年   11809篇
  2015年   13380篇
  2014年   17041篇
  2013年   20281篇
  2012年   16153篇
  2011年   15729篇
  2010年   14009篇
  2009年   15290篇
  2008年   12747篇
  2007年   11594篇
  2006年   11986篇
  2005年   10152篇
  2004年   8677篇
  2003年   7432篇
  2002年   6482篇
  2001年   6339篇
  2000年   5275篇
  1999年   5091篇
  1998年   3607篇
  1997年   3238篇
  1996年   3208篇
  1995年   2828篇
  1994年   2058篇
  1993年   1734篇
  1992年   2444篇
  1991年   2347篇
  1990年   1991篇
  1989年   1869篇
  1988年   1750篇
  1987年   1488篇
  1986年   1453篇
  1985年   1292篇
  1984年   971篇
  1983年   942篇
  1982年   700篇
  1981年   652篇
  1980年   510篇
  1979年   654篇
  1978年   584篇
  1977年   568篇
  1976年   492篇
  1972年   464篇
排序方式: 共有10000条查询结果,搜索用时 484 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