首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1219篇
  免费   54篇
  国内免费   8篇
耳鼻咽喉   14篇
儿科学   45篇
妇产科学   18篇
基础医学   76篇
口腔科学   74篇
临床医学   91篇
内科学   231篇
皮肤病学   4篇
神经病学   67篇
特种医学   21篇
外科学   444篇
综合类   14篇
预防医学   32篇
眼科学   40篇
药学   35篇
中国医学   6篇
肿瘤学   69篇
  2024年   2篇
  2023年   5篇
  2022年   16篇
  2021年   34篇
  2020年   30篇
  2019年   32篇
  2018年   40篇
  2017年   37篇
  2016年   42篇
  2015年   40篇
  2014年   66篇
  2013年   60篇
  2012年   86篇
  2011年   86篇
  2010年   50篇
  2009年   55篇
  2008年   85篇
  2007年   92篇
  2006年   80篇
  2005年   86篇
  2004年   77篇
  2003年   55篇
  2002年   56篇
  2001年   22篇
  2000年   17篇
  1999年   2篇
  1998年   8篇
  1997年   2篇
  1996年   4篇
  1995年   4篇
  1994年   3篇
  1993年   2篇
  1991年   1篇
  1988年   1篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
排序方式: 共有1281条查询结果,搜索用时 15 毫秒
11.
There is increased risk of systemic embolism during cardiopulmonary bypass in patients with a severely atherosclerotic ascending aorta. We report a coronary-coronary bypass in a 74-year-old man with a porcelain aorta. He underwent a proximal right coronary-distal right coronary artery bypass with a saphenous vein graft, combined with a pedicled arterial graft (left internal mammary artery) to the left anterior descending artery, in the presence of a beating heart without cardiopulmonary bypass. The patient survived without evidence of perioperative myocardial infarction or cerebrovascular accident. One year later, follow-up angiography showed graft patency with good distal run-off. Coronary-coronary bypass on a beating heart without cardiopulmonary bypass can be performed safely in a patient with porcelain aorta.  相似文献   
12.
BACKGROUND: The International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire allows users to find factors associated with allergic diseases, but thus far most of the studies on risk factors for allergic diseases have been devoted to asthma and not to rhinitis. OBJECTIVE: To determine the main factors associated with symptoms of allergic rhinitis and rhinoconjunctivitis in school children and adolescents in northern Mexico City. PATIENTS AND METHODS: A cross sectional, multicenter survey was conducted in northern Mexico City, in children aged 6-7 and 13-14 years. The survey instrument was the Phase Three B ISAAC questionnaire, which was validated and standardized in Spanish. RESULTS: There were 4106 6-7-year-olds and 6576 13-14-year-olds. The total prevalence of diagnosis of allergic rhinitis was 4.6%. The prevalence of cumulative and current symptoms of rhinitis was considered high (>29%), but the prevalence of the diagnosis of allergic rhinitis was considered low (ranging from 3.4% to 5.6%). The prevalence of symptoms of rhinitis with conjunctivitis had intermediate values (ranging from 20.3% to 30.2%). Cumulative symptoms of allergic rhinitis, current symptoms of allergic rhinitis, and rhinoconjunctivitis were related to symptoms of current or cumulative asthma, symptoms of current or cumulative atopic eczema, and current use of paracetamol (odds ratio > 1, P < .05). CONCLUSION: The present results support the concept of rhinitis and asthma as common chronic respiratory diseases, and this study also found a relation between paracetamol use and rhinitis in children.  相似文献   
13.
IntroductionPassive antibody therapy has been used to immunize vulnerable people against infectious agents. In this study, we aim to investigate the efficacy of convalescent plasma (CP) in the treatment of severe and critically ill patients diagnosed with COVID-19.MethodThe data of severe or critically ill COVID-19 patients who received anti-SARS-CoV-2 antibody-containing CP along with the antiviral treatment (n = 888) and an age-gender, comorbidity, and other COVID-19 treatments matched severe or critically ill COVID-19 patients at 1:1 ratio (n = 888) were analyzed retrospectively.ResultsDuration in the intensive care unit (ICU), the rate of mechanical ventilation (MV) support and vasopressor support were lower in CP group compared with the control group (p = 0.001, p = 0.02, p = 0.001, respectively). The case fatality rate (CFR) was 24.7 % in the CP group, and it was 27.7 % in the control group. Administration of CP 20 days after the COVID-19 diagnosis or COVID-19 related symptoms were associated with a higher rate of MV support compared with the first 3 interval groups (≤5 days, 6?10 days, 11?15 days) (p=0.001).ConclusionCP therapy seems to be effective for a better course of COVID-19 in severe and critically ill patients.  相似文献   
14.
The aim of the study was to compare percutaneous nephrolithotomy (PCNL) and staged retrograde flexible ureteroscopy (FURS) methods used in the treatment of kidney stones of 2 cm or more in diameter. The study comprised a total of 60 patients with a diagnosis of kidney pelvic stones more than 2 cm in diameter, for whom surgery was planned between January 2013 and January 2014. The patients were randomly allocated to two groups as staged retrograde FURS (Group A) and PCNL (Group B). Comparison of the groups was made with respect to operating time, number of procedures, total treatment time, length of hospital stay, stone-free rates and complications according to the Clavien–Dindo classification. In Group A, the total operating time of multiple sessions was 114.46 min. In Group B, a single session of PCNL was applied to all patients and the mean operating time was 86.8 min (p = 0.014). Mean total treatment time was 2.01 weeks in Group A and 1 week in Group B (p < 0.01). The mean total hospitalization time was 3.66 days in Group A and 3.13 days in Group B (p = 0.037). At the end of the sessions, clinically insignificant residual fragments were observed in ten patients of Group A and one patient of Group B (p = 0.03). No statistically significant difference was determined between the groups in terms of stone-free rates or complications. Although current technology with FURS is effective on large kidney stones, it has no superiority to PCNL due to the need for multiple sessions and long treatment time.  相似文献   
15.
Currently, the free fibular flap is well accepted as the first choice for mandibular reconstruction. Achieving functional results in pediatric patients requires a different approach than that employed for mature patients. Because the pediatric craniofacial skeleton continues to grow, reconstruction is more challenging, and the long‐term results can be different from those of adult patients. In this study, we sought to measure flap growth objectively in our series. Ten pediatric patients who underwent reconstruction with free fibular flaps were retrospectively reviewed. Flap growth was evaluated by comparing the intraoperative photographs with photographs of the control panoramic mandibular radiographs taken using photo‐anthropometric techniques. The measurements were converted to proportionality indices (PI), and these indices were compared. Subsequent complications and functional results were also evaluated. The mean patient age was 11.8 years, and the mean follow up was 57.7 months. The mean preoperative PI value was 10.74 ± 2.47. The mean postoperative PI value was 12.52 ± 2.34. The mean difference between the preoperative and postoperative PI values was ?1.78±0.53. These photo‐anthropometric data clearly illustrated the growth of the fibular flaps (P = 0.001). None of these patients exhibited nonunion of the fractures; however, one patient experienced a delayed union, one had chronic temporomandibular joint pain, and one had chronic temporomandibular joint luxation. In two patients, the inter‐incisive measurements were below the third percentile, and two additional patients had grade 2 eating abilities, which can be regarded as poor. All of the patients had symmetric mandibular contours. Free fibular flaps continue to grow in pediatric patients. This flap is a “workhorse” flap in children because it adapts to the craniofacial skeleton via its ability to grow, and this ability results in subsequent good cosmetic and functional results. © 2014 Wiley Periodicals, Inc. Microsurgery 35:253–261, 2015.  相似文献   
16.
Background and purpose — Muscle atrophy is seen in patients with metal-on-metal (MOM) hip implants, probably because of inflammatory destruction of the musculo-tendon junction. However, like pseudotumors, it is unclear when atrophy occurs and whether it progresses with time. Our objective was to determine whether muscle atrophy associated with MOM hip implants progresses with time.

Patients and methods — We retrospectively reviewed 74 hips in 56 patients (32 of them women) using serial MRI. Median age was 59 (23–83) years. The median time post-implantation was 83 (35–142) months, and the median interval between scans was 11 months. Hip muscles were scored using the Pfirrmann system. The mean scores for muscle atrophy were compared between the first and second MRI scans. Blood cobalt and chromium concentrations were determined.

Results — The median blood cobalt was 6.84 (0.24–90) ppb and median chromium level was 4.42 (0.20–45) ppb. The median Oxford hip score was 34 (5–48). The change in the gluteus minimus mean atrophy score between first and second MRI was 0.12 (p = 0.002). Mean change in the gluteus medius posterior portion (unaffected by surgical approach) was 0.08 (p = 0.01) and mean change in the inferior portion was 0.10 (p = 0.05). Mean pseudotumor grade increased by 0.18 (p = 0.02).

Interpretation — Worsening muscle atrophy and worsening pseudotumor grade occur over a 1-year period in a substantial proportion of patients with MOM hip implants. Serial MRI helps to identify those patients who are at risk of developing worsening soft-tissue pathology. These patients should be considered for revision surgery before irreversible muscle destruction occurs.  相似文献   
17.
Both hereditary and nonhereditary retinoblastoma (Rb) are commonly initiated by loss of both copies of the retinoblastoma tumor suppressor gene (RB1), while additional genomic changes are required for tumor initiation and progression. Our aim was to determine whether there is genomic heterogeneity between different clinical Rb subtypes. Therefore, 21 Rb tumors from 11 hereditary patients and 10 nonhereditary Rb patients were analyzed using high‐resolution single nucleotide polymorphism (SNP) arrays and gene losses and gains were validated with Multiplex Ligation‐dependent Probe Amplification. In these tumors only a few focal aberrations were detected. The most frequent was a focal gain on chromosome 2p24.3, the minimal region of gain encompassing the oncogene MYCN. The genes BAZ1A, OTX2, FUT8, and AKT1 were detected in four focal regions on chromosome 14 in one nonhereditary Rb. There was a large difference in number of copy number aberrations between tumors. A subset of nonhereditary Rbs turned out to be the most genomic unstable, while especially very young patients with hereditary Rb display stable genomes. Established Rb copy number aberrations, including gain of chromosome arm 1q and loss of chromosome arm 16q, turned out to be preferentially associated with the nonhereditary Rbs with later age of diagnosis. In contrast, copy number neutral loss of heterozygosity was detected mainly on chromosome 13, where RB1 resides, irrespective of hereditary status or age. Focal amplifications and deletions and copy number neutral loss of heterozygosity besides chromosome 13 appear to be rare events in retinoblastoma. © 2013 Wiley Periodicals, Inc.  相似文献   
18.
Atrial fibrillation (AF), which is the most common cardiac arrhythmia, may cause serious symptoms and impair quality of life.1 The development of AF is associated with many risk factors, including age, male gender, hypertension, heart failure, valvular disease, diabetes mellitus (DM) and left atrial (LA) enlargement.2-4 Electrical and/or mechanical remodelling of the atria is thought to be a pathophysiological characteristic of AF.5The pregnant state may be pro-dysrhythmic. This is related to the cardiovascular, hormonal, haemodynamic and autonomic changes during healthy pregnancy. Levels of oestrogen and β-human chorionic gonadotropin increase dramatically. Haemodynamic changes include an increase in circulating blood volume, which increases cardiac output. This results in myocardial stretch and an increase in cardiac end-diastolic volume. High plasma catecholamine concentrations and adrenergic receptor sensitivity increase sympathetic tone. All these changes in pregnant women may make them more prone to dysrhythmogenesis.6Most pregnant women complain of palpitations, dizziness and even syncope, but these symptoms are rarely associated with cardiac dysrhythmias. AF is the most common clinically significant cardiac arrhythmia in the general population but it is rarely seen in pregnant women. When it occurs, it can represent a benign, self-limited lone episode of AF or may be secondary to congenital or rheumatic valvular disease, hypertrophic cardiomyopathy, thyroid disease, or pre-excitation syndrome.Two simple electrocardiogram (ECG) markers, namely maximum P-wave duration (Pmax) and P-wave dispersion (PD), have been used to evaluate intra- and inter-atrial conduction times and the inhomogeneous propagation of sinus impulses, which are well-known electrophysiological characteristics of the atrium prone to fibrillation.7,8 Prolonged Pmax and PD have been reported to represent an increased risk for AF in patients with no underlying heart disease.7,8 Besides, evidence from laboratory and epidemiological research suggests that systemic inflammation may play a role in AF aetiology.9 It has also been demonstrated that atrial electromechanical coupling, measured by tissue Doppler imaging (TDI), as significantly longer in patients with paroxysmal AF than in control groups.10,11To our knowledge, no study evaluating PD and atrial electromechanical coupling has been investigated in pregnant subjects without additional systemic disease. Therefore, in this study we aimed to examine atrial electromechanical coupling and PD, reflecting inter-atrial conduction times in pregnant subjects.  相似文献   
19.
Elucidation of the molecular mechanisms of leukemogenesis is important for a better understanding of the prognosis of acute lymphoblastic leukemia (ALL). Studies have shown that the expression of upregulated gene 4 (URG4), which promotes cell growth and survival, is increased in different types of carcinomas including hepatocellular carcinoma, gastric cancer and osteosarcoma. Similarly, higher expression of URG4 and cyclin D1 gene might promote proliferation of the blast cells by causing escape from the G1 checkpoint and entry into the S phase. This study reports the high expression level of URG4 in 2 high-risk ALL patients for the first time in the literature. In conclusion, the higher expression of URG4 in our 2 patients suggests that URG4 might be involved in leukemogenesis. Future studies with a large number of high-risk ALL patients and cell culture studies are needed to demonstrate the exact role of URG4 in leukemogenesis.  相似文献   
20.
Purpose: The aim of this study was to compare vertical and horizontal mandibular alveolar bone resorption by measuring bone morphological variation in Kennedy Class II removable partial denture (RPD) wearers and non‐wearers using cone‐beam computed tomography (CBCT). Materials and Methods: In total, 124 sites in the CBCT scans of 62 (29 RPD non‐wearers, 33 RPD wearers) Kennedy Class II patients were analyzed retrospectively. Three‐dimensional representations of the mandible with superimposed cross‐sectional slices were developed with the CBCT scans to evaluate the mandibular alveolar height and width by measuring distances between the mandibular canal, mylohyoid ridge, alveolar crest, and lower border of the mandible in four regions (eight sites) of Kennedy Class II non‐wearers and wearers of RPDs. Results: Mandibular alveolar bone height and width were significantly lower in edentulous sites when compared with dentate sites in both Kennedy Class II non‐wearers and wearers of RPDs (p < 0.05). Additionally, mean vertical and horizontal mandibular bone resorption was significantly higher in RPD wearers than in non‐wearers (p < 0.05). Conclusions: Vertical and horizontal alveolar bone resorption was found to be higher in the RPD wearing patients when comparing the dentate and edentulous sites.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号