全文获取类型
收费全文 | 441370篇 |
免费 | 32420篇 |
国内免费 | 1784篇 |
专业分类
耳鼻咽喉 | 4884篇 |
儿科学 | 11551篇 |
妇产科学 | 8592篇 |
基础医学 | 57607篇 |
口腔科学 | 8838篇 |
临床医学 | 43523篇 |
内科学 | 93464篇 |
皮肤病学 | 5911篇 |
神经病学 | 42636篇 |
特种医学 | 14629篇 |
外国民族医学 | 24篇 |
外科学 | 67956篇 |
综合类 | 6691篇 |
现状与发展 | 2篇 |
一般理论 | 592篇 |
预防医学 | 39148篇 |
眼科学 | 10547篇 |
药学 | 30030篇 |
7篇 | |
中国医学 | 718篇 |
肿瘤学 | 28224篇 |
出版年
2023年 | 2078篇 |
2022年 | 3652篇 |
2021年 | 8498篇 |
2020年 | 5086篇 |
2019年 | 8245篇 |
2018年 | 9455篇 |
2017年 | 7303篇 |
2016年 | 7953篇 |
2015年 | 9423篇 |
2014年 | 14009篇 |
2013年 | 19812篇 |
2012年 | 29613篇 |
2011年 | 31525篇 |
2010年 | 17829篇 |
2009年 | 16045篇 |
2008年 | 28797篇 |
2007年 | 30374篇 |
2006年 | 29714篇 |
2005年 | 30139篇 |
2004年 | 28512篇 |
2003年 | 26686篇 |
2002年 | 25208篇 |
2001年 | 3896篇 |
2000年 | 3010篇 |
1999年 | 4246篇 |
1998年 | 5614篇 |
1997年 | 4760篇 |
1996年 | 4199篇 |
1995年 | 3868篇 |
1994年 | 3355篇 |
1993年 | 3095篇 |
1992年 | 2407篇 |
1991年 | 2244篇 |
1990年 | 2027篇 |
1989年 | 1897篇 |
1988年 | 1952篇 |
1987年 | 1936篇 |
1986年 | 1917篇 |
1985年 | 2026篇 |
1984年 | 2611篇 |
1983年 | 2511篇 |
1982年 | 3063篇 |
1981年 | 2844篇 |
1980年 | 2622篇 |
1979年 | 1500篇 |
1978年 | 1668篇 |
1977年 | 1535篇 |
1976年 | 1392篇 |
1975年 | 1140篇 |
1974年 | 1108篇 |
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
81.
82.
Denise Lee Marcella D. Walker Hsin Yi Chen John A. Chabot James A. Lee Jennifer H. Kuo 《Surgery》2019,165(1):107-113
Background
Bone mineral density (BMD) has been found to improve after parathyroidectomy (PTX) in patients with primary hyperparathyroidism. There are few data on the effect of PTX on BMD in normocalcemic and normohormonal primary hyperparathyroidism.Methods
A retrospective analysis of 92 primary hyperparathyroidism patients who underwent PTX between 2004 and 2012 with pre- and post-PTX dual-energy x-ray absorptiometry was performed. Within-person changes in BMD pre- and post-PTX were analyzed using log linear mixed models, stratified by biochemical status.Results
Bone mineral density increased post-PTX in the whole cohort at the lumbar spine (+2.5%), femoral neck (+2.1%), and total hip (+1.9%) and decreased at the one-third radius (–0.9%). On comparison of BMD changes by profile, BMD increased in those with the typical profile at the lumbar spine (3.2%), femoral neck (2.9%), and total hip (2.9%) but declined at the one-third radius (–1.5%). In contrast, BMD improved only at the femoral neck (4.3%) in the normohormonal group and did not change at any site in the normocalcemic group. The typical group had a greater increase in BMD over time at the femoral neck and total hip compared with normocalcemic patients.Conclusion
Our results indicate that the skeletal benefit of PTX was attenuated in normocalcemic and normohormonal patients, suggesting that skeletal changes after PTX may depend on biochemical profile. 相似文献83.
84.
85.
86.
87.
Yinong Young-Xu Julia Thornton Snider Robertus van Aalst Salaheddin M. Mahmud Edward W. Thommes Jason K.H. Lee David P. Greenberg Ayman Chit 《Vaccine》2019,37(11):1484-1490
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88.
Katherine M. Duszynski Nicole L. Pratt John W. Lynch Jesia G. Berry Michael S. Gold 《Vaccine》2019,37(2):280-288
Objective
To determine whether differences in combination DTaP vaccine types at 2, 4 and 6?months of age were associated with mortality (all-cause or non-specific), within 30?days of vaccination.Design
Observational nationwide cohort study.Setting
Linked population data from the Australian Childhood Immunisation Register and National Death Index.Participants
Australian infants administered a combination trivalent, quadrivalent or hexavalent DTaP vaccine (DTaP types) between January 1999 and December 2010 at 2, 4 and 6?months as part of the primary vaccination series. The study population included 2.9, 2.6, & 2.3?million children in the 2, 4 and 6?month vaccine cohorts, respectively.Main outcome measures
Infants were evaluated for the primary outcome of all-cause mortality within 30?days. A secondary outcome was non-specific mortality (unknown cause of death) within 30?days of vaccination. Non-specific mortality was defined as underlying or other cause of death codes, R95 ‘Sudden infant death syndrome’, R96 ‘Other sudden death, cause unknown’, R98 ‘Unattended death’, R99 ‘Other ill-defined and unspecified cause of mortality’ or where no cause of death was recorded.Results
The rate of 30?day all-cause mortality was low and declined from 127.4 to 59.3 deaths per 100,000 person-years between 2 and 6?month cohorts. When compared with trivalent DTaP vaccines, no elevated risk in all-cause or non-specific mortality was seen with any quadrivalent or hexavalent DTaP vaccines, for any cohort.Conclusion
Use of routine DTaP combination vaccines with differing disease antigens administered during the first six months of life is not associated with infant mortality. 相似文献89.
Gudrun Aspelund Elaa M Mahdi David H Rothstein Derek S Wakeman 《Journal of gastroenterology and hepatology》2019,34(6):966-974
Choledochal cysts (CDCs) and biliary atresia (BA) are rare pediatric hepatobiliary anomalies that require surgical intervention due to increased risk of malignancy and liver failure, respectively. The underlying disease and operative procedures place patients at risk for long‐term complications, which may continue to affect them into adulthood. Lack of a transitional care model in the health‐care system potentiates the challenges they will face following aging out of their pediatric providers' care. We sought to elucidate the long‐term complications and challenges patients with CDCs and BA face, review the current literature regarding transitioning care, and propose guidelines aiding adult providers in continued care and surveillance of these patients. A literature review was performed to assess short‐term and long‐term complications after surgery and the current standards for transitioning care in patients with a history of CDCs and BA. While transitional programs exist for patients with other gastrointestinal diseases, there are few that focus on CDCs or BA. Generally, authors encourage medical record transmission from pediatric to adult providers, ensuring accuracy of information and compliance with treatment plans. Patients with CDCs are at risk for developing biliary malignancies, cholangitis, and anastomotic strictures after resection. Patients with BA develop progressive liver failure, necessitating transplantation. There are no consensus guidelines regarding timing of follow up for these patients. Based on the best available evidence, we propose a schema for long‐term surveillance. 相似文献
90.
Keith P. Reber John D. Sivey Matthew Vollmuth Priyansh D. Gujarati 《Journal of labelled compounds & radiopharmaceuticals》2022,65(9):254-263
Parabens are antimicrobial additives found in a wide array of consumer products. However, the halogenated compounds formed from parabens during wastewater disinfection are a potential environmental concern. In order to identify these transformation products and investigate their mechanism of formation, a synthetic route to ethyl parabens labeled with the stable isotope carbon-13 at specific positions within the benzene ring was developed. This efficient two-step procedure starts from commercially available 13C-labeled phenols and involves (1) initial acylation of the phenol via a Houben–Hoesch reaction with trichloroacetonitrile followed by (2) a modified haloform reaction of the resulting trichloromethyl ketone to afford the corresponding 13C-labeled ethyl parabens in 65%–80% overall yield. The scope of the modified haloform reaction was also investigated, allowing for the synthesis of other parabens derived from primary or secondary alcohols, including 13C- and deuterium-labeled esters. In addition, 4-hydroxybenzoic acid can be formed directly from the common trichloromethyl ketone intermediate upon treatment with lithium hydroxide. This protocol complements existing methods for preparing 13C-labeled paraben derivatives and offers the specific advantages of exhibiting complete regioselectivity in the Houben–Hoesch reaction (to form the para-disubstituted product) and avoiding the need for protecting groups in the modified haloform reaction that forms the paraben esters. 相似文献