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   256494篇
  免费   39935篇
  国内免费   2290篇
耳鼻咽喉   4466篇
儿科学   5631篇
妇产科学   6978篇
基础医学   25731篇
口腔科学   8304篇
临床医学   44579篇
内科学   53831篇
皮肤病学   7354篇
神经病学   23503篇
特种医学   11528篇
外科学   38810篇
综合类   2268篇
现状与发展   45篇
一般理论   81篇
预防医学   22642篇
眼科学   6278篇
药学   14390篇
中国医学   1600篇
肿瘤学   20700篇
  2024年   591篇
  2023年   5649篇
  2022年   2520篇
  2021年   7350篇
  2020年   7531篇
  2019年   5418篇
  2018年   10988篇
  2017年   10330篇
  2016年   11758篇
  2015年   13318篇
  2014年   16971篇
  2013年   20165篇
  2012年   16008篇
  2011年   15575篇
  2010年   13922篇
  2009年   15197篇
  2008年   12606篇
  2007年   11422篇
  2006年   11837篇
  2005年   10007篇
  2004年   8554篇
  2003年   7309篇
  2002年   6371篇
  2001年   6325篇
  2000年   5258篇
  1999年   5074篇
  1998年   3586篇
  1997年   3222篇
  1996年   3195篇
  1995年   2821篇
  1994年   2045篇
  1993年   1726篇
  1992年   2439篇
  1991年   2341篇
  1990年   1984篇
  1989年   1859篇
  1988年   1744篇
  1987年   1485篇
  1986年   1443篇
  1985年   1283篇
  1984年   969篇
  1983年   932篇
  1982年   690篇
  1981年   646篇
  1980年   499篇
  1979年   649篇
  1978年   576篇
  1977年   561篇
  1976年   488篇
  1972年   462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