全文获取类型
收费全文 | 374298篇 |
免费 | 22784篇 |
国内免费 | 8209篇 |
专业分类
耳鼻咽喉 | 4678篇 |
儿科学 | 13753篇 |
妇产科学 | 6103篇 |
基础医学 | 28132篇 |
口腔科学 | 8203篇 |
临床医学 | 41083篇 |
内科学 | 64843篇 |
皮肤病学 | 6412篇 |
神经病学 | 18989篇 |
特种医学 | 17896篇 |
外国民族医学 | 22篇 |
外科学 | 56794篇 |
综合类 | 36773篇 |
现状与发展 | 28篇 |
一般理论 | 51篇 |
预防医学 | 36531篇 |
眼科学 | 6646篇 |
药学 | 32140篇 |
394篇 | |
中国医学 | 11399篇 |
肿瘤学 | 14421篇 |
出版年
2023年 | 5723篇 |
2022年 | 8667篇 |
2021年 | 16190篇 |
2020年 | 11910篇 |
2019年 | 19393篇 |
2018年 | 14836篇 |
2017年 | 10872篇 |
2016年 | 10505篇 |
2015年 | 13767篇 |
2014年 | 25229篇 |
2013年 | 22289篇 |
2012年 | 24356篇 |
2011年 | 23972篇 |
2010年 | 19576篇 |
2009年 | 18660篇 |
2008年 | 17609篇 |
2007年 | 16991篇 |
2006年 | 14412篇 |
2005年 | 10504篇 |
2004年 | 6667篇 |
2003年 | 5332篇 |
2002年 | 4919篇 |
2001年 | 4541篇 |
2000年 | 5142篇 |
1999年 | 4670篇 |
1998年 | 4770篇 |
1997年 | 3619篇 |
1996年 | 2766篇 |
1995年 | 2362篇 |
1994年 | 2312篇 |
1993年 | 1673篇 |
1992年 | 1950篇 |
1991年 | 1660篇 |
1990年 | 1710篇 |
1989年 | 1468篇 |
1988年 | 1470篇 |
1987年 | 1189篇 |
1985年 | 4091篇 |
1984年 | 5470篇 |
1983年 | 3983篇 |
1982年 | 4020篇 |
1981年 | 3819篇 |
1980年 | 3378篇 |
1979年 | 3081篇 |
1978年 | 2475篇 |
1977年 | 2196篇 |
1976年 | 2276篇 |
1975年 | 1800篇 |
1974年 | 1673篇 |
1973年 | 1577篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
《Journal of Cardiovascular Computed Tomography》2022,16(6):517-523
BackgroundSelection of the transcatheter heart valve size for a mitral valve-in-valve procedure is based on the type and manufacturer’s labelled size. However, accurate information of surgical heart valve (SHV) size may not be available in the patient’s medical record. The purpose of this study is to establish reference data for computed tomography (CT) dimensions of commonly used mitral SHV in order to determine the manufacturer’s labelled size from a cardiac CT data set.MethodsCT datasets of 105 patients with surgical mitral bioprosthesis and available manufacturer labeled datasets were included in the analysis. CT derived valve dimensions were assessed by two observers using multiplanar reformats aligned with the basal sewing ring. A circular region of interest was used in a standardized fashion to minimize influence of image acquisition and reconstruction parameters. Interobserver variability was assessed by Bland-Altman analysis.ResultsThe CT-derived dimensions were stratified by valve size and type, and SHV properties were demonstrated for 5 common valve types. Variability of measurements was small and inter-observer limits of agreement were narrow. Stratified by SHV type, no overlap was noted for CT-derived dimensions among different SHV sizes . A reference table of CT characteristics of surgical mitral bioprosthesis types was created.ConclusionThe study provides reference CT data for determining the manufacturers’ labeled SHV size across a range of commonly used mitral SHVs. The findings will be important to help identify types of surgical mitral bioprosthesis utilizing CT characteristics for patients without SHV size documentation. 相似文献
12.
目的 研究凉血通瘀方对高血压大鼠急性脑出血模型脑组织miRNA表达的影响,对差异表达的miRNA靶基因进行分析,探索凉血通瘀方可能的药效机制。方法 将自发性高血压大鼠随机分成对照组(B)和实验组(C)。适应性饲养一周后,C组灌胃凉血通瘀方,B组灌胃等体积生理盐水,连续5天,每天1次。构建脑出血模型后收集脑组织,借助全转录组测序技术获得miRNA表达量,与miRBase数据库比对获取已知miRNA,使用miRDeep2预测新miRNA。差异分析软件为DESeq2,筛选阈值为|log2FC| ≥1 并且P <0.05。对显著差异表达的miRNA进行靶基因预测,对靶基因进行GO功能、KEGG通路富集和PPI网络分析。结果 实验组和对照组对比,共发现21个显著差异表达的miRNA,上调有9个,下调有12个,共预测得到1243个有统计学意义的靶基因。GO富集分析发现,生物过程中突触囊泡分泌的调节、神经递质分泌的调节和神经递质运输的调节占前三位,神经元投射终点、全膜、质膜区域和细胞投射则是主要的细胞成分。分子功能分别为小GTPase绑定、底物特异性跨膜转运蛋白活性和离子跨膜转运体活性。通路分析结果显示,靶基因在癌证通路、pI3K-Akt信号通路、人类乳头瘤病毒感染、神经活性配体-受体相互作用和MAPK通路等分布广泛。采用STRING网站和Cytoscape软件,根据MCC算法筛选出ADRA2C、CASR、CCL28、CCR1、DRD2、GNAT3、GRM2、DYNC1LI1、GABBR1、GNAI1等核心靶基因。结论 凉血通瘀方对脑出血急性期鼠脑组织内miRNA的表达有重要影响;显著差异表达miRNAs可能通过靶向核心基因调控凉血通瘀方干预急性脑出血的病理过程及预后。 相似文献
13.
《Obstetrics, Gynaecology and Reproductive Medicine》2022,32(8):179-187
Continuous utero-placental circulation, and patent umbilical blood vessels ensure an uninterrupted transfer of oxygen and nutrients to the fetus as well as clearance of metabolic waste products. The onset of labour characterized by progressive and strong uterine contractions poses a threat to fetal oxygenation as a result of collapsing the spiral arterioles traversing the myometrium to supply the placental bed, and repetitive compression of the blood vessels within the umbilical cord. Human fetuses are equipped with compensatory mechanisms to cope with transient interruptions of blood supply during labour. The ability to compensate may be blunted in cases of poor fetal reserves, increased metabolic demand (macrosomia or maternal fever), and due to non-hypoxic pathways (e.g. chorioamniontis or fetal hypovolumia-hypotension syndrome). Intrapartum fetal surveillance involves prompt recognition of the features that signal the onset of fetal decompensation on the cardiotocograph (CTG) to ensure a timely intervention to avoid hypoxic-ischaemic encephalopathy (HIE) or perinatal deaths. This article summarises a ‘physiological approach’ to the interpretation of the CTG which, in places, conflicts with other current UK guidance. 相似文献
14.
15.
16.
17.
《Journal of pediatric surgery》2023,58(9):1843-1848
BackgroundCommon salt is a safe, effective and cheap home-made remedy for umbilical granuloma. The aim of this scoping review is to identify and summarize the available evidence and examine the research conducted on salt treatment for umbilical granuloma.MethodsA literature search was performed in the second week of September, 2022 using Google scholar, PubMed, MEDLINE and EMBASE databases using the keywords ‘umbilical granuloma’ and ‘salt treatment’ to identify all English articles pertaining to salt treatment for umbilical granuloma. Tables were made to summarize the methodological characteristics, results and the dosage regimens of salt used by different authors. The Cochrane Collaboration's tool was used for assessing risk of bias in RCTs. The indexing statuses of the journals publishing these studies were also noted. The overall efficacy with the use of common salt was calculated by adding the success rates mentioned in each study.ResultsTwenty-four articles (2 systematic reviews, 6 Randomized Controlled Trials, 11 prospective cohort studies, 1 case control study, 3 retrospective case series and 1 case report) were included. An overall 93.91% success rate (1033/1100) was seen with common salt application, without any reports of complications/recurrences.ConclusionTopical application of common salt for umbilical granulomas is simple, effective and inexpensive. This scoping review provides a broader outlook at the existing level of evidence and may help in planning interventional comparative studies, so that recommendations can be formulated. It also highlights a lack of properly designed randomized controlled trials on this topic.Level of EvidenceI. 相似文献
18.
《The Journal of thoracic and cardiovascular surgery》2023,165(2):591-604.e3
ObjectivesGuidelines suggest aortic valve replacement (AVR) for low-risk asymptomatic patients. Indications for transcatheter AVR now include low-risk patients, making it imperative to understand state-of-the-art surgical AVR (SAVR) in this population. Therefore, we compared SAVR outcomes in low-risk patients with those expected from Society of Thoracic Surgeons (STS) models and assessed their intermediate-term survival.MethodsFrom January 2005 to January 2017, 3493 isolated SAVRs were performed in 3474 patients with STS predicted risk of mortality <4%. Observed operative mortality and composite major morbidity or mortality were compared with STS-expected outcomes according to calendar year of surgery. Logistic regression analysis was used to identify risk factors for these outcomes. Patients were followed for time-related mortality.ResultsWith 15 observed operative deaths (0.43%) compared with 55 expected (1.6%), the observed:expected ratio was 0.27 for mortality (95% confidence interval [CI], 0.14-0.42), stroke 0.65 (95% CI, 0.41-0.89), and reoperation 0.50 (95% CI, 0.42-0.60). Major morbidity or mortality steadily declined, with probabilities of 8.6%, 6.7%, and 5.2% in 2006, 2011, and 2016, respectively, while STS-expected risk remained at approximately 12%. Mitral valve regurgitation, ventricular hypertrophy, pulmonary, renal, and hepatic failure, coronary artery disease, and earlier surgery date were residual risk factors. Survival was 98%, 91%, and 82% at 1, 5, and 9 years, respectively, superior to that predicted for the US age-race-sex–matched population.ConclusionsSTS risk models overestimate contemporary SAVR risk at a high-volume center, supporting efforts to create a more agile quality assessment program. SAVR in low-risk patients provides durable survival benefit, supporting early surgery and providing a benchmark for transcatheter AVR. 相似文献
19.
《Journal of pediatric surgery》2023,58(9):1694-1698
BackgroundThe Coronavirus Disease 2019 pandemic provided a natural experiment to study the effect of social distancing on the risk of developing Hirschsprung's Associated Enterocolitis (HAEC).MethodsUsing the Pediatric Health Information System (PHIS), a retrospective cohort study of children (<18 years) with Hirschsprung's Disease (HSCR) across 47 United States children's hospitals was performed. The primary outcome was HAEC admissions per 10,000 patient-days. The exposure (COVID-19) was defined as April 2020–December 2021. The unexposed (historical control) period was April 2018–December 2019. Secondary outcomes included sepsis, bowel perforation, intensive care unit (ICU) admission, mortality, and length of stay.ResultsOverall, we included 5707 patients with HSCR during the study period. There were 984 and 834 HAEC admissions during the pre-pandemic and pandemic periods, respectively (2.6 vs. 1.9 HAEC admissions per 10,000 patient-days, incident rate ratio [95% confidence interval]: 0.74 [0.67, 0.81], p < 0.001). Compared to pre-pandemic, those with HAEC during the pandemic were younger (median [IQR]: 566 [162, 1430] days pandemic vs. 746 [259, 1609] days pre-pandemic, p < 0.001) and more likely to live in the lowest quartile of median household income zip codes (24% pandemic vs. 19% pre-pandemic, p = 0.02). There were no significant differences in rates of sepsis (6.1% pandemic vs. 6.1% pre-pandemic, p > 0.9), bowel perforation (1.3% pandemic vs. 1.2% pre-pandemic, p = 0.8), ICU admissions (9.6% pandemic vs. 12% pre-pandemic, p = 0.2), mortality (0.5% pandemic vs. 0.6% pre-pandemic, p = 0.8), or length of stay (median [interquartile range]: 4 [(Pastor et al., 2009; Gosain and Brinkman, 2015) 2,112,11 days pandemic vs. 5 [(Pastor et al., 2009; Tang et al., 2020) 2,102,10 days pre-pandemic, p = 0.4).ConclusionsThe COVID-19 pandemic was associated with significantly decreased incidence of HAEC admissions across US children's hospitals. Possible etiologies such as social distancing should be explored.Level of evidenceII. 相似文献
20.
《The Annals of thoracic surgery》2023,115(1):88-95
BackgroundRecent guidelines for the treatment of moderate or severe ischemic mitral regurgitation (IMR) in patients undergoing coronary artery bypass grafting (CABG) have changed. This study assessed the real-world impact of changing guidelines on the management of IMR during CABG over time. We hypothesized that the utilization of mitral valve repair for IMR would decrease over time, whereas mitral valve replacement for severe IMR would increase.MethodsPatients undergoing CABG in a statewide collaborative database (2011-2020) were stratified by severity of IMR. Trends in mitral valve repair or replacement were evaluated. To account for differences of the patients, propensity score–matched analyses were used to compare patients with and without mitral intervention.ResultsA total of 11,676 patients met inclusion criteria, including 1355 (11.6%) with moderate IMR and 390 (3.3%) with severe IMR. The proportion of patients undergoing mitral intervention for moderate IMR decreased over time (2011, 17.7%; 2020, 7.5%; Ptrend = .001), whereas mitral replacement for severe IMR remained stable (2011, 11.1%; 2020, 13.3%; Ptrend = .14). Major morbidity was higher for patients with moderate IMR who underwent mitral intervention (29.1% vs 19.9%; P = .005). In a propensity analysis of 249 well-matched pairs, there was no difference in major morbidity (29.3% with mitral intervention vs 23.7% without; P = .16) or operative mortality (1.2% vs 2.4%; P = .5).ConclusionsConsistent with recent guideline updates, patients with moderate IMR were less likely to undergo mitral repair. However, the rate of replacement for severe IMR did not change. Mitral intervention during CABG did not increase operative mortality or morbidity. 相似文献