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   189550篇
  免费   38525篇
  国内免费   6603篇
耳鼻咽喉   3367篇
儿科学   4131篇
妇产科学   3304篇
基础医学   13832篇
口腔科学   6661篇
临床医学   36565篇
内科学   37410篇
皮肤病学   4753篇
神经病学   16495篇
特种医学   8069篇
外国民族医学   27篇
外科学   27418篇
综合类   15217篇
现状与发展   70篇
一般理论   10篇
预防医学   19716篇
眼科学   4770篇
药学   11396篇
  82篇
中国医学   4868篇
肿瘤学   16517篇
  2024年   742篇
  2023年   6003篇
  2022年   3742篇
  2021年   6956篇
  2020年   8310篇
  2019年   4714篇
  2018年   9778篇
  2017年   10087篇
  2016年   10694篇
  2015年   12305篇
  2014年   15695篇
  2013年   17253篇
  2012年   11371篇
  2011年   11581篇
  2010年   12202篇
  2009年   13612篇
  2008年   9147篇
  2007年   7753篇
  2006年   8705篇
  2005年   6626篇
  2004年   4892篇
  2003年   4537篇
  2002年   3922篇
  2001年   3965篇
  2000年   2896篇
  1999年   3243篇
  1998年   3013篇
  1997年   2767篇
  1996年   2665篇
  1995年   2317篇
  1994年   1714篇
  1993年   1340篇
  1992年   1295篇
  1991年   1132篇
  1990年   925篇
  1989年   900篇
  1988年   817篇
  1987年   659篇
  1986年   608篇
  1985年   500篇
  1984年   401篇
  1983年   398篇
  1982年   313篇
  1981年   284篇
  1980年   189篇
  1979年   173篇
  1978年   180篇
  1977年   170篇
  1976年   134篇
  1972年   133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.
目的探究老年胃癌患者术前血清白细胞介素6 (IL-6)、胃蛋白酶原(PG)Ⅰ、Ⅱ及PG-Ⅰ/Ⅱ比值在患者预后评估中的意义。方法选择2016年1月—2017年1月南通大学附属海安医院收治的101例外科手术治疗的老年胃癌患者为研究对象。收集患者的临床病理资料,检测血清IL-6和PG-Ⅰ/Ⅱ水平。以全因死亡为随访终点,使用Kaplan-Meier曲线明确患者预后与各指标间的关系。结果受试者工作特征曲线提示,IL-6、PG-Ⅰ和PG-Ⅰ/Ⅱ比值在最佳切割值为10.23pg/mL、30.65μg/L和2.44时,可评估患者的预后,而PG-Ⅱ则无法评估患者的预后。与IL-6≤10.23pg/mL组相比,IL-6> 10.23pg/mL组的肿瘤细胞分化更差、TNM分期Ⅲ期比例明显升高。Kaplan-Meier曲线结果表明,IL-6> 10.23pg/mL组的中位生存期显著短于IL-6≤10.23pg/mL组(28个月vs47个月,P<0.001);PG-Ⅰ≤30.65μg/L组的中位生存期显著短于PG-Ⅰ>30.65μg/L组(34个月vs49个月,P=0.008);PG-Ⅰ/Ⅱ≤2.44组的中位生存期显著短于PG-Ⅰ/Ⅱ> 2.44组(29个月vs56个月,P=0.02)。多因素Cox回归分析表明,肿瘤分化程度、TNM分期、IL-6及PG-Ⅰ/Ⅱ比值是影响患者生存率的独立危险因素。结论术前检测IL-6及PG-Ⅰ/Ⅱ比值有助于评估老年胃癌患者的预后。  相似文献   
9.
Social Psychiatry and Psychiatric Epidemiology - The negative effect of catastrophic financial loss on suicide risk is widely perceived but hardly studied in-depth because of various difficulties...  相似文献   
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