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   250101篇
  免费   18360篇
  国内免费   1127篇
耳鼻咽喉   2783篇
儿科学   6497篇
妇产科学   4587篇
基础医学   32792篇
口腔科学   4562篇
临床医学   25172篇
内科学   53036篇
皮肤病学   3382篇
神经病学   24217篇
特种医学   8380篇
外国民族医学   11篇
外科学   38421篇
综合类   3442篇
一般理论   318篇
预防医学   21205篇
眼科学   6526篇
药学   16937篇
  4篇
中国医学   361篇
肿瘤学   16955篇
  2023年   1208篇
  2022年   1263篇
  2021年   5437篇
  2020年   3262篇
  2019年   5302篇
  2018年   5954篇
  2017年   4469篇
  2016年   4956篇
  2015年   5830篇
  2014年   8607篇
  2013年   11798篇
  2012年   18015篇
  2011年   18905篇
  2010年   10580篇
  2009年   9432篇
  2008年   16603篇
  2007年   17460篇
  2006年   17308篇
  2005年   17286篇
  2004年   16195篇
  2003年   15047篇
  2002年   14070篇
  2001年   2113篇
  2000年   1602篇
  1999年   2320篇
  1998年   3071篇
  1997年   2562篇
  1996年   2186篇
  1995年   2096篇
  1994年   1744篇
  1993年   1575篇
  1992年   1263篇
  1991年   1154篇
  1990年   1002篇
  1989年   979篇
  1988年   973篇
  1987年   957篇
  1986年   931篇
  1985年   966篇
  1984年   1191篇
  1983年   1103篇
  1982年   1318篇
  1981年   1284篇
  1980年   1122篇
  1979年   694篇
  1978年   734篇
  1977年   619篇
  1976年   568篇
  1975年   458篇
  1974年   468篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
51.
52.
53.
54.
BackgroundRural populations face many health disadvantages compared to urban areas. There is a critical need to better understand the current lung cancer screening landscape in these communities to identify targeted areas to improve the impact of this proven tool.MethodsData from the County Health Rankings of New Hampshire and Vermont was reviewed for population density, distribution of adult smokers, and level of education compared to the distribution of Lung Cancer Screening Facilities throughout these two states.ResultsScreening programs in southern counties of Vermont with lower levels of education have decreased access. In New Hampshire, there are no programs within 30 miles of the areas with the largest distribution of smokers, and decreased access in some areas with the lowest levels of education.ConclusionsImproving equitable access to high-quality screening services in rural regions and the creation of targeted interventions to address decreased access in areas of high tobacco use and low education is vital to decreasing the incidence of latestage presentations of lung cancer within these populations.  相似文献   
55.
Magnetic resonance elastography aims to non-invasively and remotely characterize the mechanical properties of living tissues. To quantitatively and regionally map the shear viscoelastic moduli in vivo, the technique must achieve proper mechanical excitation throughout the targeted tissues. Although it is straightforward, ante manibus, in close organs such as the liver or the breast, which practitioners clinically palpate already, it is somewhat fortunately highly challenging to trick the natural protective barriers of remote organs such as the brain. So far, mechanical waves have been induced in the latter by shaking the surrounding cranial bones. Here, the skull was circumvented by guiding pressure waves inside the subject's buccal cavity so mechanical waves could propagate from within through the brainstem up to the brain. Repeatable, reproducible and robust displacement fields were recorded in phantoms and in vivo by magnetic resonance elastography with guided pressure waves such that quantitative mechanical outcomes were extracted in the human brain.  相似文献   
56.
57.
58.
59.
60.

Background

Observational studies of the relative effectiveness of influenza vaccines are essential for public health decision making. Their estimates, however, are subject to bias due to unmeasured confounders. Instrumental variable (IV) methods can control for observed and unobserved confounders.

Methods

We used linked electronic medical record databases in the Veterans Health Administration (VHA) as well as Medicare administrative files to examine the relative vaccine effectiveness (rVE) of high-dose influenza vaccine (HD) versus standard-dose influenza vaccines (SD) in preventing hospitalizations among VHA-enrolled Veterans ≥65?years of age during 5 influenza seasons (2010–2011 through 2014–2015). Using multivariable IV Poisson regression modeling to address unmeasured confounding and bias, we analyzed the data by each season and through longitudinal analysis of all five seasons.

Findings

We included 3,638,924 person–influenza seasons of observation where 158,636 (4%) were among HD vaccine recipients and 3,480,288 (96%) were among SD vaccine recipients. Of the 1,728,562 Veterans, 1,702,824 (98.5%) were male and 1,299,412 (75%) were non-Hispanic white. Based on the longitudinal analysis of all five seasons, the IV-adjusted rVE estimate of HD vs. SD was 10% (95% CI, 8–12%) against all-cause hospitalization; 18% (95% CI, 15–21%) against cardiorespiratory-associated hospitalization; and 14% (95% CI, 6–22%) against influenza/pneumonia-associated hospitalization. The findings by season were similar.

Interpretation

Our analysis of VHA clinical data collected from approximately 1.7 million Veterans 65?years and older during five seasons demonstrates that high-dose influenza vaccine is more effective than standard-dose influenza vaccines in preventing influenza- or pneumonia-associated hospitalizations, cardiorespiratory hospitalizations, and all-cause hospitalizations.  相似文献   
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