收费全文 | 273867篇 |
免费 | 20707篇 |
国内免费 | 1147篇 |
耳鼻咽喉 | 3004篇 |
儿科学 | 7143篇 |
妇产科学 | 5130篇 |
基础医学 | 36027篇 |
口腔科学 | 5122篇 |
临床医学 | 28024篇 |
内科学 | 58181篇 |
皮肤病学 | 3711篇 |
神经病学 | 26347篇 |
特种医学 | 9078篇 |
外国民族医学 | 11篇 |
外科学 | 41413篇 |
综合类 | 4009篇 |
一般理论 | 329篇 |
预防医学 | 23791篇 |
眼科学 | 6987篇 |
药学 | 18873篇 |
7篇 | |
中国医学 | 389篇 |
肿瘤学 | 18145篇 |
2023年 | 1431篇 |
2022年 | 2544篇 |
2021年 | 5744篇 |
2020年 | 3432篇 |
2019年 | 5601篇 |
2018年 | 6304篇 |
2017年 | 4753篇 |
2016年 | 5218篇 |
2015年 | 6145篇 |
2014年 | 9025篇 |
2013年 | 12487篇 |
2012年 | 18953篇 |
2011年 | 19852篇 |
2010年 | 11154篇 |
2009年 | 9890篇 |
2008年 | 17461篇 |
2007年 | 18462篇 |
2006年 | 18213篇 |
2005年 | 18270篇 |
2004年 | 17060篇 |
2003年 | 15968篇 |
2002年 | 14895篇 |
2001年 | 2778篇 |
2000年 | 2279篇 |
1999年 | 2900篇 |
1998年 | 3331篇 |
1997年 | 2765篇 |
1996年 | 2382篇 |
1995年 | 2330篇 |
1994年 | 1957篇 |
1993年 | 1759篇 |
1992年 | 1768篇 |
1991年 | 1627篇 |
1990年 | 1457篇 |
1989年 | 1418篇 |
1988年 | 1371篇 |
1987年 | 1362篇 |
1986年 | 1315篇 |
1985年 | 1393篇 |
1984年 | 1580篇 |
1983年 | 1409篇 |
1982年 | 1634篇 |
1981年 | 1537篇 |
1980年 | 1368篇 |
1979年 | 1038篇 |
1978年 | 1034篇 |
1977年 | 838篇 |
1976年 | 822篇 |
1974年 | 744篇 |
1973年 | 680篇 |
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Methods: A retrospective cohort design and data from two US healthcare claims repositories were employed. The study population included patients who had non-metastatic cancer of the breast, colon/rectum, lung or ovaries, or non-Hodgkin’s lymphoma (NHL), and who received myelosuppressive chemotherapy regimens with an intermediate/high risk for FN. For each patient, the first cycle of the first course was characterized in terms of PP-CSF use and FN episodes. Crude incidence proportions for PP-CSF and FN during the first cycle were estimated by calendar quarter (2010–2016); multivariable logistic regression models were used to estimate quarter-specific adjusted mean probabilities of FN by PP-CSF use.
Results: The study population totaled 142,730 patients with breast cancer (61%), colorectal cancer (14%), NHL (11%), ovarian cancer (10%) or lung cancer (5%). PP-CSF use increased from 52% in 1Q2010 to 58% in 4Q2016; pegfilgrastim was the most commonly used agent (>96% across quarters). PP-CSF administration on the same day as chemotherapy ranged from 8 to 11% until 1Q2015, and increased to 64% by 4Q2016. Adjusted incidence proportions for FN in the first chemotherapy cycle ranged from 2.7% (95% CI: 2.3–3.0) to 3.7% (95% CI: 3.1–4.3) among those who did not receive PP-CSF, and was 2.6% (95% CI: 2.5–2.7) across quarters among those who received PP-CSF.
Conclusions: Although the use of PP-CSF is commonplace in current US clinical practice, underutilization in cancer patients receiving chemotherapy regimens with an intermediate/high risk for FN may still be an issue. Use of same-day PP-CSF increased markedly from the end of 2015, although this finding reflects (at least in part) increased uptake of pegfilgrastim delivered via an on-body injector as well as the recent change in clinical practice guidelines. Overall, patients receiving PP-CSF appear to have a lower risk of FN during the first cycle of chemotherapy. 相似文献