全文获取类型
收费全文 | 6493篇 |
免费 | 276篇 |
国内免费 | 102篇 |
专业分类
耳鼻咽喉 | 66篇 |
儿科学 | 78篇 |
妇产科学 | 212篇 |
基础医学 | 511篇 |
口腔科学 | 208篇 |
临床医学 | 481篇 |
内科学 | 2092篇 |
皮肤病学 | 88篇 |
神经病学 | 417篇 |
特种医学 | 272篇 |
外科学 | 1384篇 |
综合类 | 31篇 |
现状与发展 | 1篇 |
一般理论 | 3篇 |
预防医学 | 244篇 |
眼科学 | 132篇 |
药学 | 247篇 |
中国医学 | 3篇 |
肿瘤学 | 401篇 |
出版年
2024年 | 6篇 |
2023年 | 74篇 |
2022年 | 157篇 |
2021年 | 283篇 |
2020年 | 164篇 |
2019年 | 230篇 |
2018年 | 274篇 |
2017年 | 159篇 |
2016年 | 198篇 |
2015年 | 187篇 |
2014年 | 312篇 |
2013年 | 363篇 |
2012年 | 534篇 |
2011年 | 573篇 |
2010年 | 376篇 |
2009年 | 336篇 |
2008年 | 484篇 |
2007年 | 499篇 |
2006年 | 461篇 |
2005年 | 348篇 |
2004年 | 279篇 |
2003年 | 195篇 |
2002年 | 170篇 |
2001年 | 50篇 |
2000年 | 36篇 |
1999年 | 23篇 |
1998年 | 28篇 |
1997年 | 14篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 17篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有6871条查询结果,搜索用时 0 毫秒
31.
Kiriakos Stefanidis Dorothea Tsatsou Dimitrios Konstantinidis Lazaros Gymnopoulos Petros Daras Saskia Wilson-Barnes Kathryn Hart Vronique Cornelissen Elise Decorte Elena Lalama Andreas Pfeiffer Maria Hassapidou Ioannis Pagkalos Anagnostis Argiriou Konstantinos Rouskas Stelios Hadjidimitriou Vasileios Charisis Sofia Balula Dias Jos Alves Diniz Gonalo Telo Hugo Silva Alex Bensenousi Kosmas Dimitropoulos 《Nutrients》2022,14(20)
AI-based software applications for personalized nutrition have recently gained increasing attention to help users follow a healthy lifestyle. In this paper, we present a knowledge-based recommendation framework that exploits an explicit dataset of expert-validated meals to offer highly accurate diet plans spanning across ten user groups of both healthy subjects and participants with health conditions. The proposed advisor is built on a novel architecture that includes (a) a qualitative layer for verifying ingredient appropriateness, and (b) a quantitative layer for synthesizing meal plans. The first layer is implemented as an expert system for fuzzy inference relying on an ontology of rules acquired by experts in Nutrition, while the second layer as an optimization method for generating daily meal plans based on target nutrient values and ranges. The system’s effectiveness is evaluated through extensive experiments for establishing meal and meal plan appropriateness, meal variety, as well as system capacity for recommending meal plans. Evaluations involved synthetic data, including the generation of 3000 virtual user profiles and their weekly meal plans. Results reveal a high precision and recall for recommending appropriate ingredients in most user categories, while the meal plan generator achieved a total recommendation accuracy of 92% for all nutrient recommendations. 相似文献
32.
Charalampos Siristatidis Konstantinos Dafopoulos Nikolas Christoforidis George Anifandis Vasileios Pergialiotis Nikolaos Papantoniou 《Gynecological endocrinology》2017,33(12):968-971
Recombinant DNA technologies have produced Corifollitropin alfa (CFa) used during IVF/ICSI in order to keep the circulating FSH levels above the threshold necessary to support multi-follicular growth for a week. In this prospective case-control study, we compared 70 participants treated with 150?μg CFa combined with 150?IU of follitropin beta (study group) with 70 subfertile participants with matching baseline characteristics, conforming with the same inclusion criteria and treated with an antagonist protocol using follitropin beta (control group). Live birth was the primary outcome, while secondary outcome measures were IVF/ICSI cycles characteristics, including adverse events and complications. Live birth was determined in reduced rates in the study compared to the control group, reaching statistical significance [6/70 versus 20/70, p?=?0.002], as also in the respective number of clinical pregnancies [9/70 versus 23/70, p?=?0.005], although the incidence of miscarriage was similar for both groups [6/70 versus 5/70, p?>?0.99]. Most of the secondary parameters examined were similar between groups. Logistic regression revealed that protocol and AFC had a direct impact on live birth. Ovarian stimulation with CFa does not seem to constitute an equally effective method as compared with follitropin beta to be offered in a general subfertile population seeking IVF/ICSI treatments. 相似文献
33.
Active materials have gained increasing momentum during the last decades due to their ability to act as sensors and actuators without the need for an external controlling system or an electronic signal. Shape memory alloys (SMAs), which are a subcategory of active materials, are slowly being introduced in the civil engineering sector in applications that refer to prestressing and strengthening of various structural elements. Low-cost iron-based SMAs are a good alternative to the Ni-Ti SMAs for such uses since the cost of large-scale civil engineering applications would otherwise be prohibitive. The scope of this study is the investigation of the thermomechanical response of the Fe-17Mn-5Si-10Cr-4Ni-1(V,C) ferrous SMA. In particular, this study focuses on the application of prestress, and on the alloy’s behavior under fatigue loadings. In addition, the effect of loading frequency on the recovery stress of the material is thoroughly investigated. Four dog-bone specimens were prepared and tested in low-cycle fatigue. All the experiments aimed at the simulation of prestress. The recovery stress was monitored after pre-straining and heating applied under strain–control conditions. The experimental results are promising in terms of the is situ prestress feasibility since the measured recovery stress values are satisfactory high. 相似文献
34.
Panagiotis M. Angelopoulos Nikolaos Rafael Vrithias Zacharias Viskadourakis Petros Tsakiridis Konstantinos C. Vasilopoulos Antonis Peppas Georgios Asimakopoulos Anastasia V. Spyrou Michael A. Karakassides Maria Taxiarchou George Kenanakis 《Materials》2022,15(14)
The use of amorphous microspheres as filler in composites is promising due to their light weight, low cost, incombustibility, and the ability to alter relevant properties of the final composite. Contrary to glass spheres, perlite microspheres are much cheaper and can be tailor-made to facilitate purpose-oriented alteration of the final composite. We report the use of perlite microspheres for the preparation of: (1) composites, through a compression molding (hot pressing) technique; and (2) composite filaments, in a single screw extruder, as well as their use for sample printing through Fused Deposition Modeling (FDM). Proper characterization of the produced composites allows for their evaluation in terms of physical, thermal, and mechanical properties and with regards to the manufacturing technique, the filler fraction, and size. Composite samples of acceptable quality in terms of filler survival and dispersion as well as mechanical properties were produced through compression molding using fine expanded perlite microspheres (<90 μm) up to an infill ratio of 40 vol.%. Fine fillers (<90 μm) performed well in FDM, allowing printing of composite dogbone samples with a higher Young’s modulus and elongation and similar ultimate tensile strength compared to benchmark, up to an infill ratio of 20 vol.%. Composite samples present a slightly lower burning rate compared to those produced solely by ABS. Perlite microspheres present good workability in both applications, possessing satisfactory performance as filler in the composites, and can thus be assumed a promising multifunctional filler for various thermoplastics considering their low price, environmental impact, and fire rating. 相似文献
35.
36.
Ioannis S Papanikolaou Georgios Tziatzios Alexandros Chatzidakis Antonio Facciorusso Stefano Francesco Crin Paraskevas Gkolfakis Gjorgi Deriban Mario Tadic Goran Hauser Antonios Vezakis Ivan Jovanovic Nicola Muscatiello Anna Meneghetti Konstantinos Miltiadou Kalina Stardelova Alojzije Lacković Maria-Zoi Bourou Srdjan Djuranovic Konstantinos Triantafyllou 《World journal of gastrointestinal endoscopy》2021,13(9):416-425
BACKGROUND Coronavirus disease 2019(COVID-19) significantly affected endoscopy practice,as gastrointestinal endoscopy is considered a risky procedure for transmission of infection to patients and personnel of endoscopy units(PEU).AIM To assess the impact of COVID-19 on endoscopy during the first European lockdown(March-May 2020).METHODS Patients undergoing endoscopy in nine endoscopy units across six European countries during the period of the first European lockdown for COVID-19(MarchMay 2020) were included. Prior to the endoscopy procedure, participants were stratified as low-or high-risk for potential COVID-19 infection according to the European Society of Gastrointestinal Endoscopy(ESGE) and the European Society of Gastroenterology and Endoscopy Nurses and Associates(ESGENA) joint statement, and contacted 7-14 d later to assess COVID-19 infection status. PEU were questioned regarding COVID-19 symptoms and/or infection via questionnaire, while information regarding hospitalizations, intensive care unitadmissions and COVID-19-related deaths were collected. The number of weekly endoscopies at each center during the lockdown period was also recorded.RESULTS A total of 1267 endoscopies were performed in 1222 individuals across nine European endoscopy departments in six countries. Eighty-seven(7%) were excluded because of initial positive testing. Of the 1135 pre-endoscopy low risk or polymerase chain reaction negative for COVID-19, 254(22.4%) were tested post endoscopy and 8 were eventually found positive, resulting in an infection rate of 0.7% [(95%CI: 0.2-0.12]. The majority(6 of the 8 patients, 75%) had undergone esophagogastroduodenoscopy. Of the 163 PEU, 5 [3%;(95%CI: 0.4-5.7)] tested positive during the study period. A decrease of 68.7%(95%CI: 64.8-72.7) in the number of weekly endoscopies was recorded in all centers after March 2020. All centers implemented appropriate personal protective measures(PPM) from the initial phases of the lockdown.CONCLUSION COVID-19 transmission in endoscopy units is highly unlikely in a lockdown setting, provided endoscopies are restricted to emergency cases and PPM are implemented. 相似文献
37.
38.
39.
Ng DW Vlachonassios K Nimalasuriya AR Nguyen VT Wijesekera C Khan A Chandraratna PA 《The American journal of cardiology》2004,93(7):923-925
In this pilot study, we used transthoracic echocardiography to measure coronary sinus blood flow in 15 patients before and after coronary artery bypass grafting. Coronary sinus blood flow before and after revascularization was 274 +/- 95 and 451 +/- 102 ml/min, respectively (p <0.001). This finding is consistent with those previously demonstrated by invasive techniques. 相似文献
40.
Siagris D Christofidou M Tsamandas A Lekkou A Thomopoulos K Labropoulou-Karatza C 《The Journal of infection》2004,49(3):236-241
OBJECTIVES: Mixed cryoglobulinemia (MC) is the most common extrahepatic manifestation of HCV infection. The aim of this study is to determine the prevalence of MC in HCV infected Greek patients and to identify if it is associated with liver histology or the mode of HCV transmission. METHODS: One hundred and twenty-six patients with chronic HCV infection were evaluated for the presence of serum cryoglobulins, autoantibodies and viral markers. One hundred and eighteen of them underwent liver biopsy and each specimen was evaluated according to the grading and staging system described by Ishak et al. RESULTS: Cryoglobulins were detected in 37/126 (29.4%) HCV patients and cryocrit values ranged between 0.5 and 6.5%. Only two patients presented clear clinical manifestations of MC. In patients with MC, a higher grading (6.40+/-2.06 vs. 5.27+/-2.55, p=0.013) and staging score (3.71+/-1.45 vs. 2.83+/-1.84, p=0.007) was noted in liver biopsy compared to those without MC. Logistic regression analysis identified staging score (OR, 1.33; CI, 1.06-1.66, p=0.015) as the only independent variable associated with cryoglobulinemia. Correlation between the presence of cryoglobulins and the mode of HCV transmission was not found. CONCLUSIONS: Greek patients with chronic HCV infection have high prevalence of cryoglobulinemia. A clear association between the presence of serum cryoglobulins and staging score of chronic hepatitis was found, with no difference in patients' age or the duration of infection. It is possible that cryoglobulinemia results in more rapid hepatic fibrosis in HCV infected patients. 相似文献