全文获取类型
收费全文 | 34371篇 |
免费 | 2248篇 |
国内免费 | 155篇 |
专业分类
耳鼻咽喉 | 257篇 |
儿科学 | 1091篇 |
妇产科学 | 836篇 |
基础医学 | 4431篇 |
口腔科学 | 682篇 |
临床医学 | 3561篇 |
内科学 | 6882篇 |
皮肤病学 | 546篇 |
神经病学 | 3489篇 |
特种医学 | 976篇 |
外国民族医学 | 3篇 |
外科学 | 4790篇 |
综合类 | 328篇 |
一般理论 | 32篇 |
预防医学 | 2804篇 |
眼科学 | 772篇 |
药学 | 2489篇 |
中国医学 | 39篇 |
肿瘤学 | 2766篇 |
出版年
2023年 | 245篇 |
2022年 | 442篇 |
2021年 | 832篇 |
2020年 | 519篇 |
2019年 | 782篇 |
2018年 | 891篇 |
2017年 | 676篇 |
2016年 | 713篇 |
2015年 | 875篇 |
2014年 | 1199篇 |
2013年 | 1661篇 |
2012年 | 2577篇 |
2011年 | 2569篇 |
2010年 | 1484篇 |
2009年 | 1250篇 |
2008年 | 2322篇 |
2007年 | 2521篇 |
2006年 | 2250篇 |
2005年 | 2179篇 |
2004年 | 2199篇 |
2003年 | 1961篇 |
2002年 | 1803篇 |
2001年 | 263篇 |
2000年 | 209篇 |
1999年 | 296篇 |
1998年 | 377篇 |
1997年 | 328篇 |
1996年 | 267篇 |
1995年 | 214篇 |
1994年 | 196篇 |
1993年 | 203篇 |
1992年 | 189篇 |
1991年 | 162篇 |
1990年 | 132篇 |
1989年 | 119篇 |
1988年 | 107篇 |
1987年 | 117篇 |
1986年 | 106篇 |
1985年 | 97篇 |
1984年 | 110篇 |
1983年 | 113篇 |
1982年 | 112篇 |
1981年 | 109篇 |
1980年 | 97篇 |
1979年 | 79篇 |
1978年 | 77篇 |
1977年 | 66篇 |
1976年 | 71篇 |
1975年 | 67篇 |
1972年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
BackgroundLittle is known about the extent of ordering low-value services by.PurposeTo compare the rates of low-value back images ordered by primary care physicians (PCMDs) and primary care nurse practitioners (PCNPs).MethodWe used 2012 and 2013 Medicare Part B claims for all beneficiaries in 18 hospital referral ?regions (HRRs) and a measure of low-value back imaging from Choosing Wisely. Models included random clinician effect and fixed effects for beneficiary age, disability, Elixhauser comorbidities, clinician sex, the emergency department setting, back pain visit volume, organization, and region (HRR).FindingsPCNPs (N = 231) and PCMDs (N = 4,779) order low-value back images at similar rates (NP: all images: 26.5%; MRI/CT: 8.4%; MD: all images: 24.5%; MRI/CT: 7.7%), with no detectable significant difference when controlling for covariates.DiscussionPCNPs and PCMDs order low-value back images at an effectively similar rate. 相似文献
4.
5.
6.
7.
8.
9.
Josh Greenstein Devjani Das Josie Acuna Monica Kapoor Cara Brown Abbas Husain Brendan Lally Barry Hahn 《The American journal of emergency medicine》2019,37(2):313-316
Background
In the emergency department, rib fractures are a common finding in patients who sustain chest trauma. Rib fractures may be a sign of significant, underlying pathology, especially in the elderly patients where rib fractures are associated with significant morbidity and mortality. To date, no studies have evaluated the ability of ultrasound to detect rib fractures using cadaver models and subsequently use this model as a teaching tool.Objectives
The purpose of this study was to determine if it is possible to generate rib fractures on cadaver models which could be accurately identified using ultrasound.Methods
This was a cross-sectional study performed during one session at a cadaver lab. A single hemithorax from four adult cadavers were used as models. Single rib fractures on each of rib five through eight were created. Four subjects, blinded to the normal versus fractured ribs, were asked to identify the presence of a fracture on each rib.Results
A total of 8 of 16 potential ribs had fractured induced by study staff. Mean accuracy was 55% for all subjects. The overall sensitivity and specificity for detecting rib fractures was 50% (CI: 31.89–68.11) and 59.38% (CI: 35.69–73.55) respectively. The overall PPV and NPV was 55.17% and 54.29% respectively.Conclusions
In this pilot study, subjects were not able to detect induced rib fractures using ultrasound on cadaver models. The use of this model as a teaching tool in the detection of rib fractures requires further investigation. 相似文献10.
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