全文获取类型
收费全文 | 8006篇 |
免费 | 514篇 |
国内免费 | 50篇 |
专业分类
耳鼻咽喉 | 120篇 |
儿科学 | 171篇 |
妇产科学 | 127篇 |
基础医学 | 971篇 |
口腔科学 | 270篇 |
临床医学 | 679篇 |
内科学 | 1685篇 |
皮肤病学 | 165篇 |
神经病学 | 516篇 |
特种医学 | 315篇 |
外国民族医学 | 2篇 |
外科学 | 1252篇 |
综合类 | 136篇 |
一般理论 | 5篇 |
预防医学 | 548篇 |
眼科学 | 362篇 |
药学 | 731篇 |
中国医学 | 73篇 |
肿瘤学 | 442篇 |
出版年
2024年 | 9篇 |
2023年 | 100篇 |
2022年 | 203篇 |
2021年 | 378篇 |
2020年 | 249篇 |
2019年 | 315篇 |
2018年 | 403篇 |
2017年 | 270篇 |
2016年 | 329篇 |
2015年 | 319篇 |
2014年 | 469篇 |
2013年 | 571篇 |
2012年 | 800篇 |
2011年 | 793篇 |
2010年 | 461篇 |
2009年 | 324篇 |
2008年 | 513篇 |
2007年 | 474篇 |
2006年 | 363篇 |
2005年 | 297篇 |
2004年 | 224篇 |
2003年 | 232篇 |
2002年 | 176篇 |
2001年 | 34篇 |
2000年 | 24篇 |
1999年 | 34篇 |
1998年 | 24篇 |
1997年 | 13篇 |
1996年 | 17篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1990年 | 4篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1974年 | 6篇 |
排序方式: 共有8570条查询结果,搜索用时 15 毫秒
101.
102.
Johannes Siebermair Eugene G Kholmovski Douglas Sheffer Joyce Schroeder Leif Jensen Mobin Kheirkhahan Alex A Baher Majd M Ibrahim Theresa Reiter Tienush Rassaf Reza Wakili Nassir F Marrouche Christopher J McGann Brent D Wilson 《The British journal of radiology》2021,94(1123)
Objectives:Magnetic resonance angiography (MRA) has been established as an important imaging method in cardiac ablation procedures. In pulmonary vein (PV) isolation procedures, MRA has the potential to minimize the risk of severe complications, such as atrio-esophageal fistula, by providing detailed information on esophageal position relatively to cardiac structures. However, traditional non-gated, first-pass (FP) MRA approaches have several limitations, such as long breath-holds, non-uniform signal intensity throughout the left atrium (LA), and poor esophageal visualization. The aim of this observational study was to validate a respiratory-navigated, ECG-gated (EC), saturation recovery-prepared MRA technique for simultaneous imaging of LA, LA appendage, PVs, esophagus, and adjacent anatomical structures.Methods:Before PVI, 106 consecutive patients with a history of AF underwent either conventional FP-MRA (n = 53 patients) or our new EC-MRA (n = 53 patients). Five quality scores (QS) of LA and esophagus visibility were assessed by two experienced readers. The non-parametric Mann–Whitney U-test was used to compare QS between FP-MRA and EC-MRA groups, and linear regression was applied to assess clinical contributors to image quality.Results:EC-MRA demonstrated significantly better image quality than FP-MRA in every quality category. Esophageal visibility using the new MRA technique was markedly better than with the conventional FP-MRA technique (median 3.5 [IQR 1] vs median 1.0, p < 0.001). In contrast to FP-MRA, overall image quality of EC-MRA was not influenced by heart rate.Conclusion:Our ECG-gated, respiratory-navigated, saturation recovery-prepared MRA technique provides significantly better image quality and esophageal visibility than the established non-gated, breath-holding FP-MRA. Image quality of EC-MRA technique has the additional advantage of being unaffected by heart rate.Advances in knowledge:Detailed information of cardiac anatomy has the potential to minimize the risk of severe complications and improve success rates in invasive electrophysiological studies. Our novel ECG-gated, respiratory-navigated, saturation recovery-prepared MRA technique provides significantly better image quality of LA and esophageal structures than the traditional first-pass algorithm. This new MRA technique is robust to arrhythmia (tachycardic, irregular heart rates) frequently observed in AF patients. 相似文献
103.
104.
105.
106.
Reza Taherkhani Sakineh Taherkhani Fatemeh Farshadpour 《World Journal of Clinical Cases》2021,9(18):4480-4490
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the most recent global health threat, is spreading throughout the world with worrisome speed, and the current wave of coronavirus disease 2019 (COVID-19) seems to have no mercy. While this mysterious virus challenges our ability to control viral infections, our opportunities to control the COVID-19 pandemic are gradually fading. Currently, pandemic management relies on preventive interventions. Although prevention is a good strategy to mitigate SARS-CoV-2 transmission, it still cannot be considered an absolute solution to eliminate this pandemic. Currently, developing a potent immunity against this viral infection seems to be the most promising strategy to drive down this ongoing global tragedy. However, with the emergence of new challenges in the context of immune responses to COVID-19, the road to control this devastating pandemic seems bumpier; thus, it is pivotal to characterize the dynamics of host immune responses to COVID-19, in order to develop efficient prophylactic and therapeutic tools. This begs the question of whether the effector mechanisms of the immune system are indeed potent or a possible contributing factor to developing more severe and lethal forms of COVID-19. In this review, the possible role of the immunopathologic phenomena including antibody-dependent enhancement, cytokine storm, and original antigenic sin in severity and mortality of COVID-19 will be discussed. 相似文献
107.
Muhammad Umer Siddiqui Ahmed K. Pasha Ibtisam Rauf Justin Z. Lee Muhammad Danial Siddiqui Youssef Yaacoub Mohammad Reza Movahed 《Clinical Medicine & Research》2021,19(1):19
Objective: The study objective was to determine if peri-operative bridging anticoagulation in patients with atrial fibrillation is beneficial or harmful.Design: Systematic review and meta-analysis.Setting: Inpatient or in-hospital setting.Participants: Adults with atrial fibrillation having a CHADS2 score >1 undergoing elective surgical procedure on anticoagulation.Methods: A systemic search of multiple databases (Cochrane, Medline, PubMed) was performed regarding studies conducted on efficacy and safety of perioperative bridging anticoagulation in patients with atrial fibrillation. Studies identified were reviewed by two authors individually before inclusion. The results were then pooled using Review Manager to determine the combined effect. Stroke/systemic embolism was considered as the primary efficacy outcome. Major bleeding was the primary safety outcome.Results: The systematic search revealed 108 potential articles. The full texts of 28 articles were retrieved for assessment of eligibility. After full text review, 25 articles were excluded. Three articles met inclusion criteria. No significant difference in stroke/systemic embolism with bridging anticoagulation was noted (risk ratio, 1.25-95% confidence interval [CI], 0.55–2.85). Bridging was associated with significantly higher risk of major bleeding (risk ratio, 3.29-95% CI, 2.25–4.81).Conclusion: An individualized approach is required when initiating peri-operative bridging anticoagulation. There is certainly a higher risk of bleeding with bridging anticoagulation and no difference in stroke/systemic embolism. However, the results cannot be extrapolated to patients who have valvular atrial fibrillation or CHADS2 score of 5 or greater. 相似文献
108.
Recently, visible light-driven organic photochemical synthesis has been a pioneering field of interest from academic and industrial associations due to its unique features of green and sustainable chemistry. Herein, WO3ZnO/Fe3O4 was synthesized, characterized, and used as an efficient magnetic photocatalyst in the preparation of a range of 2-substituted benzimidazoles via the condensation of benzyl alcohol and o-phenylenediamine in ethanol at room temperature for the first time. The key feature of this work is focused on the in situ photocatalytic oxidation of benzyl alcohols to benzaldehydes under atmospheric air and in the absence of any further oxidant. This new heterogeneous nanophotocatalyst was characterized via XRD, FT-IR, VSM and SEM. Short reaction time, cost-effectiveness, broad substrate scope, easy work-up by an external magnet, and excellent product yield are the major advantages of the present methodology. A number of effective experimental parameters were also fully investigated to clear broadness and generality of the protocol.WO3ZnO/Fe3O4 is used as a magnetic photocatalyst in the preparation of 2-substituted benzimidazoles in EtOH at RT. The key feature is the in situ photocatalytic oxidation of benzyl alcohols to benzaldehydes under atmospheric air in the absence of further oxidant. 相似文献
109.
Reza Barati rashvanlou Abbas Rezaee Mahdi Farzadkia Mitra Gholami Majid Kermani 《RSC advances》2020,10(59):35718
Micro-aeration as a pretreatment method improves the efficiency of anaerobic digestion of municipal sewage sludge and consequently promotes the methane production. In this study, adenosine triphosphate (ATP) and flow cytometry (FCM) were employed to monitor the performance of the micro-aerobic process and investigate the survival of bacterial cells within the process. At first, the effect of air flow rate (AFR) (0.1, 0.2, 0.3 and 0.5 vvm) on hydrolysis of mixed sludge in 5 aeration cycles (20, 30, 40, 48 and 60 hours) was examined. Then, the effects of the micro aerobic process on methane (CH4) production in anaerobic digestion were surveyed. The highest VSS reduction was 30.6% and 10.4% for 40 hours in the reactor and control, respectively. Soluble COD also fluctuated between 40.87 and 65.14% in micro-aerobic conditions; the highest SCOD was achieved at the time of 40 h. Microbial activities were increased by 597%, 170% and 79.4% for 20, 30 and 40 h pretreatment with the micro-aerobic process, respectively. Apoptosis assay showed that micro-aerobic pre-treatment at 20, 30 and 40 h increased the percentage of living cells by 57.4, 62.8 and 67.9%, respectively. On the other hand, FCM results showed that the highest percentage of viable bacteria (i.e., 67.9%) was observed at 40 h pretreating which was approximately 40% higher the ones for the control. Variation in cumulative methane production shows that methane production was increased by 221% compared to anaerobic digestion (control group). Therefore, ATP and FCM can be employed as two appropriate, accurate, relatively specific indicators for monitoring the process and bacteria viability.Micro-aeration as a pretreatment method improves the efficiency of anaerobic digestion of municipal sewage sludge and consequently promotes the methane production. 相似文献