全文获取类型
收费全文 | 41369篇 |
免费 | 1960篇 |
国内免费 | 243篇 |
专业分类
耳鼻咽喉 | 458篇 |
儿科学 | 779篇 |
妇产科学 | 968篇 |
基础医学 | 4934篇 |
口腔科学 | 2639篇 |
临床医学 | 3082篇 |
内科学 | 10551篇 |
皮肤病学 | 762篇 |
神经病学 | 3666篇 |
特种医学 | 1508篇 |
外科学 | 5859篇 |
综合类 | 160篇 |
一般理论 | 12篇 |
预防医学 | 2503篇 |
眼科学 | 707篇 |
药学 | 2339篇 |
中国医学 | 182篇 |
肿瘤学 | 2463篇 |
出版年
2023年 | 270篇 |
2022年 | 629篇 |
2021年 | 1163篇 |
2020年 | 671篇 |
2019年 | 902篇 |
2018年 | 1206篇 |
2017年 | 841篇 |
2016年 | 979篇 |
2015年 | 1202篇 |
2014年 | 1604篇 |
2013年 | 2071篇 |
2012年 | 3184篇 |
2011年 | 3483篇 |
2010年 | 1903篇 |
2009年 | 1685篇 |
2008年 | 2900篇 |
2007年 | 2953篇 |
2006年 | 2683篇 |
2005年 | 2588篇 |
2004年 | 2347篇 |
2003年 | 2055篇 |
2002年 | 1867篇 |
2001年 | 323篇 |
2000年 | 253篇 |
1999年 | 297篇 |
1998年 | 308篇 |
1997年 | 237篇 |
1996年 | 234篇 |
1995年 | 170篇 |
1994年 | 176篇 |
1993年 | 133篇 |
1992年 | 169篇 |
1991年 | 172篇 |
1990年 | 152篇 |
1989年 | 150篇 |
1988年 | 134篇 |
1987年 | 135篇 |
1986年 | 126篇 |
1985年 | 115篇 |
1984年 | 131篇 |
1983年 | 103篇 |
1982年 | 101篇 |
1981年 | 72篇 |
1980年 | 49篇 |
1979年 | 59篇 |
1978年 | 56篇 |
1977年 | 51篇 |
1975年 | 46篇 |
1974年 | 48篇 |
1973年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Melatonin reduces oxidative stress and improves vascular function in pulmonary hypertensive newborn sheep 下载免费PDF全文
Flavio Torres Alejandro González‐Candia Camilo Montt Germán Ebensperger Magdalena Chubretovic María Serón‐Ferré Roberto V. Reyes Aníbal J. Llanos Emilio A. Herrera 《Journal of pineal research》2015,58(3):362-373
Pulmonary hypertension of the newborn (PHN) constitutes a critical condition with severe cardiovascular and neurological consequences. One of its main causes is hypoxia during gestation, and thus, it is a public health concern in populations living above 2500 m. Although some mechanisms are recognized, the pathophysiological facts that lead to PHN are not fully understood, which explains the lack of an effective treatment. Oxidative stress is one of the proposed mechanisms inducing pulmonary vascular dysfunction and PHN. Therefore, we assessed whether melatonin, a potent antioxidant, improves pulmonary vascular function. Twelve newborn sheep were gestated, born, and raised at 3600 meters. At 3 days old, lambs were catheterized and daily cardiovascular measurements were recorded. Lambs were divided into two groups, one received daily vehicle as control and another received daily melatonin (1 mg/kg/d), for 8 days. At 11 days old, lung tissue and small pulmonary arteries (SPA) were collected. Melatonin decreased pulmonary pressure and resistance for the first 3 days of treatment. Further, melatonin significantly improved the vasodilator function of SPA, enhancing the endothelial‐ and muscular‐dependent pathways. This was associated with an enhanced nitric oxide‐dependent and nitric oxide independent vasodilator components and with increased nitric oxide bioavailability in lung tissue. Further, melatonin reduced the pulmonary oxidative stress markers and increased enzymatic and nonenzymatic antioxidant capacity. Finally, these effects were associated with an increase of lumen diameter and a mild decrease in the wall of the pulmonary arteries. These outcomes support the use of melatonin as an adjuvant in the treatment for PHN. 相似文献
5.
6.
Del Lama Rafael Silva Candido Raquel Mariana Chiari-Correia Natália Santana Nogueira-Barbosa Marcello Henrique de Azevedo-Marques Paulo Mazzoncini Tinós Renato 《Journal of digital imaging》2022,35(3):446-458
Journal of Digital Imaging - Vertebral Compression Fracture (VCF) occurs when the vertebral body partially collapses under the action of compressive forces. Non-traumatic VCFs can be secondary to... 相似文献
7.
8.
9.
Carlos Robles-Medranda Manuel Valero Miguel Puga-Tejada Roberto Oleas Jorge Baquerizo-Burgos Miguel Soria-Alc var Haydee Alvarado-Escobar Hannah Pitanga-Lukashok 《World journal of gastrointestinal endoscopy》2020,12(1):23-32
BACKGROUND Accurate detection of gastric infection by Helicobacter pylori(H.pylori) and premalignant lesions are important for effective provision of treatment,preventing the development of gastric neoplasia.Optical enhancement systems with optical magnification improved the identification of mucosal superficial and vascular patterns in patients with dyspepsia.AIM To evaluate an optical enhancement system with high-definition magnification,for diagnosis of normal gastric mucosa,H.pylori-associated gastritis,and gastric atrophy.METHODS A cross-sectional,nonrandomized study from November 2015 to April 2016 performed in a single-tertiary academic center from Ecuador.Seventy-two consecutive patients with functional dyspepsia according to the Rome III criteria,were tested for H.pylori using a stool antigen test and were assigned to an Hp+group or an Hp-control group.Esophagogastroduodenoscopy with highdefinition optical magnification and digital chromoendoscopy was performed,and patients were classified into 4 groups,in accordance to the microvasculararchitecture pattern of the mucosa.Interobserver and intraobserver agreement among operators were calculated.RESULTS Of the 72 participants,35 were Hp+ and 37 were Hp-.Among 10 patients with normal mucosal histology in biopsy samples,90% had a Type I pattern of microvascular architecture by endoscopy.Among participants with type IIa and type IIb patterns,significantly more were Hp+ than Hp-(32 vs 8),and most(31 out of 40) had histological diagnoses of chronic active gastritis.Two of the three participants with a histological diagnosis of atrophy had a type III microvascular pattern.The type I pattern predicted normal mucosa,type IIa–IIb predicted H.pylori infection,and type III predicted atrophy with sensitivities of 90.0%,91.4%,and 66.7%,respectively.The intraobserver and interobserver agreements had kappa values of 0.91 and 0.89,respectively.CONCLUSION High-definition optical magnification with digital chromoendoscopy is useful for diagnosis of normal gastric mucosa and H.pylori-associated gastritis with high accuracy,but further studies are needed to determine whether endoscopic diagnosis of gastric atrophy is feasible. 相似文献