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   2034篇
  免费   145篇
  国内免费   13篇
耳鼻咽喉   38篇
儿科学   113篇
妇产科学   81篇
基础医学   206篇
口腔科学   57篇
临床医学   149篇
内科学   476篇
皮肤病学   46篇
神经病学   103篇
特种医学   40篇
外国民族医学   1篇
外科学   430篇
综合类   73篇
一般理论   1篇
预防医学   97篇
眼科学   42篇
药学   128篇
中国医学   3篇
肿瘤学   108篇
  2023年   21篇
  2022年   20篇
  2021年   107篇
  2020年   72篇
  2019年   95篇
  2018年   100篇
  2017年   69篇
  2016年   65篇
  2015年   57篇
  2014年   66篇
  2013年   93篇
  2012年   120篇
  2011年   169篇
  2010年   86篇
  2009年   63篇
  2008年   90篇
  2007年   95篇
  2006年   91篇
  2005年   86篇
  2004年   77篇
  2003年   75篇
  2002年   72篇
  2001年   32篇
  2000年   23篇
  1999年   35篇
  1998年   13篇
  1997年   9篇
  1996年   12篇
  1995年   12篇
  1994年   9篇
  1993年   9篇
  1992年   20篇
  1991年   20篇
  1990年   19篇
  1989年   13篇
  1988年   11篇
  1987年   15篇
  1986年   17篇
  1985年   15篇
  1984年   6篇
  1983年   7篇
  1980年   9篇
  1979年   11篇
  1977年   9篇
  1976年   8篇
  1975年   9篇
  1974年   6篇
  1973年   7篇
  1970年   5篇
  1969年   5篇
排序方式: 共有2192条查询结果,搜索用时 31 毫秒
21.

Introduction

The influence that different concentrations of labour epidural local anesthetic have on assisted vaginal delivery (AVD) and many obstetric outcomes and side effects is uncertain. The purpose of this meta-analysis was to determine whether local anesthetics utilized at low concentrations (LCs) during labour are associated with a decreased incidence of AVD when compared with high concentrations (HCs).

Methods

We searched PubMed, Ovid EMBASE, Ovid MEDLINE, CINAHL, Scopus, clinicaltrials.gov, and Cochrane databases for randomized controlled trials of labouring patients that compared LCs (defined as ≤ 0.1% epidural bupivacaine or ≤ 0.17% ropivacaine) of epidural local anesthetic with HCs for maintenance of analgesia. The primary outcome was AVD and secondary outcomes included Cesarean delivery, duration of labour, analgesia, side effects (nausea and vomiting, motor block, hypotension, pruritus, and urinary retention), and neonatal outcomes. The odds ratios (OR) or weighted mean differences (WMD) and 95% confidence intervals (CI) were calculated using random effects modelling. An OR < 1 or a WMD < 0 favoured LCs.

Results

Eleven studies met our criteria (eight bupivacaine and three ropivacaine studies), providing 1,145 patients in the LCs group and 852 patients in the HCs group for analysis of the primary outcome. Low concentrations were associated with a reduction in the incidence of AVD (OR = 0.70; 95% CI 0.56 to 0.86; P < 0.001). There was no difference in the incidence of Cesarean delivery (OR 1.05; 95% CI 0.82 to 1.33; P = 0.7). The LCs group had less motor block (OR 3.9; 95% CI 1.59 to 9.55; P = 0.003), greater ambulation (OR 2.8; 95% CI 1.1 to 7.14; P = 0.03), less urinary retention (OR 0.42; 95% CI 0.23 to 0.73; P = 0.002), and a shorter second stage of labour (WMD ?14.03; 95% CI ?27.52 to ?0.55; P = 0.04) compared with the HCs group. There were no differences between groups in pain scores, maternal nausea and vomiting, hypotension, fetal heart rate abnormalities, five-minute Apgar scores, and need for neonatal resuscitation. One-minute Apgar scores < 7 favoured the HCs group (OR 1.53; 95% CI 1.07 to 2.21; P = 0.02), and there was more pruritus in the LCs group (OR 3.36; 95% CI 1.00 to 11.31; P = 0.05).

Conclusion

When compared with HCs of local anesthetics, the use of LCs for labour epidural analgesia reduces the incidence of AVD. This may be due to a reduction in the amount of local anesthetic used and the subsequent decrease in motor blockade. We therefore recommend the use of LCs of local anesthetics for epidural analgesia to optimize obstetric outcome.  相似文献   
22.

Objectives

There is currently no agreement on the best method of assessing active left atrial (LA) emptying. This study evaluated the relative merits of cine- and velocity encoded (VENC) magnetic resonance imaging (MRI) for the assessment of active LA emptying.

Methods

Total LA emptying volume (TLAEV) and active LA stroke volume (ALASV) were assessed in 107 consecutive patients using cine-MRI and transmitral flow measurements by VENC-MRI. The fraction of active LA emptying (ALAEF) was calculated as the ratio of ALASV to TLAEV. LA and left ventricular (LV) output were calculated by multiplying TLAEV and LV stroke volume by heart rate, respectively.

Results

Intra- and inter-observer variances were significantly larger for cine-MRI than for VENC-MRI measurements of ALASV (24.7?mL2 vs. 3.7?mL2 and 57.7?mL2 vs. 4.2?mL2; P?P?P?P?P?Conclusion VENC-MRI is the more appropriate method of assessing active LA emptying and its use should be favoured.

Key Points

? Cardiac magnetic resonance imaging (MRI) offers new possibilities in assessing atrial emptying. ? Cine-MRI measurements of active LA emptying have lower reproducibility than velocity encoded MRI. ? Cine-MRI overestimates the fraction of active LA emptying compared with VENC-MRI. ? VENC-MRI is the more appropriate method of assessing active LA emptying.  相似文献   
23.
Tropical pyomyositis is a bacterial infection of the skeletal muscles leading to abscess formation, occurring in the tropical areas, often following minor trauma. We report a case of pancarditis as the direct complication of pyomyositis in a 10-year-old girl who presented with painful swelling of her right thigh, high grade fever and impaired consciousness. Echocardiography showed pericardial effusion with strands and a large vegetation in the left ventricle cavity. She was treated successfully with open heart surgical drainage and intravenous antibiotics. We emphasize early diagnosis and prompt treatment of pyomyositis to reduce its associated mortality and morbidities.  相似文献   
24.
25.
OBJECTIVE: Osteoprotegerin (OPG) is an inhibitor of osteoclastogenesis, which has been recently involved in atherosclerosis. The relationship between coronary atherosclerosis and OPG has never been studied in asymptomatic type 2 diabetic patients. RESEARCH DESIGN AND METHODS: This is a nested case-control study; 162 asymptomatic type 2 diabetic patients were evaluated for silent myocardial ischemia using stress myocardial perfusion imaging; of 50 patients with positive results, 37 underwent coronary angiography, 20 of whom showed significant coronary artery disease (CAD group). Of 112 patients without silent myocardial ischemia, 20 subjects (NO-CAD group) were selected and matched by age and sex to patients with CAD. OPG, C-reactive protein, adiponectin, lipoprotein(a), albuminuria, and classical risk factors were measured. RESULTS: The percentages of subjects with OPG levels above median and with nephropathy were higher in the CAD group than in the NO-CAD group (70 vs. 25%, P = 0.004 and 50 vs. 5%, P = 0.001, respectively). LDL cholesterol levels were higher and HDL cholesterol levels lower in the CAD compared with the NO-CAD group (P = 0.033 and P = 0.005, respectively). No other variables were associated with CAD. Logistic regression analysis showed that OPG values above median (odds ratio 8.31 [95% CI 1.18-58.68], P = 0.034) and nephropathy (21.98 [1.24-388.36], P = 0.035) were significant independent predictors of asymptomatic CAD in type 2 diabetic patients. CONCLUSIONS: Our investigation reports the first evidence of an independent association of OPG with asymptomatic CAD in type 2 diabetic patients. The results of this nested case- control study with 20 cases need to be confirmed in a larger population.  相似文献   
26.
27.

Objectives:

To determine preferences of patients regarding their involvement in the clinical decision making process and the related factors in Saudi Arabia.

Methods:

This cross-sectional study was conducted in a major family practice center in King Abdulaziz Medical City, Riyadh, Saudi Arabia, between March and May 2012. Multivariate multinomial regression models were fitted to identify factors associated with patients preferences.

Results:

The study included 236 participants. The most preferred decision-making style was shared decision-making (57%), followed by paternalistic (28%), and informed consumerism (14%). The preference for shared clinical decision making was significantly higher among male patients and those with higher level of education, whereas paternalism was significantly higher among older patients and those with chronic health conditions, and consumerism was significantly higher in younger age groups. In multivariate multinomial regression analysis, compared with the shared group, the consumerism group were more likely to be female [adjusted odds ratio (AOR) =2.87, 95% confidence interval [CI] 1.31-6.27, p=0.008] and non-dyslipidemic (AOR=2.90, 95% CI: 1.03-8.09, p=0.04), and the paternalism group were more likely to be older (AOR=1.03, 95% CI: 1.01-1.05, p=0.04), and female (AOR=2.47, 95% CI: 1.32-4.06, p=0.008).

Conclusion:

Preferences of patients for involvement in the clinical decision-making varied considerably. In our setting, underlying factors that influence these preferences identified in this study should be considered and tailored individually to achieve optimal treatment outcomes.Patients and physicians assume different and varying roles in the medical consultation process. This could determine the extent of involvement of the patient and the physicians in the clinical decision making process and patient care management. In one extreme, the physician assumes the responsibility of the clinical decision with no or very little joint deliberation with the patient. This is known as the “paternalistic” approach.1,2 In the other extreme, the informed medical decision approach means that the clinical decision is made by patients and potential others, including family members, after obtaining all needed medical information that could enable the patient to make on appropriate decision. This is known as the “consumerism” approach to clinical decision-making.3,4 Shared decision making is probably at the center of this spectrum, in which patients and physicians exchange information, discuss the details of the medical problems, explore available treatment options, and conclude together an agreed treatment plan.5 The provision of health care that is consistent with the preferences of patients may improve the patients’ satisfaction and health outcomes.6,7 The practice of shared clinical decision-making was encouraged as it respects patients’ autonomy, values, and commitment to the agreed health plan and continuity of care.8 The relevant literature shows that most patients prefer to be offered information on their medical conditions, available options of treatment, and future plan of care.1,3,9 However, the extent of the involvement of patients in the process of decision making is variable and influenced by issues related to the patients status of their illnesses, and types of decisions under consideration.10,11 Patients of younger age, women, and with higher levels of education have been found to prefer an active role and to share this process. In addition, preferences of patients may change with time and different stages of the sickness.11,12 The complexity of this process is further compounded by the fact that patient views and attitudes towards involvement in medical decision making are influenced significantly by certain underlying cultural aspects. This necessitates a sensitive and individual approach for each patient.13 This study aims to explore preferences of patients from Saudi Arabia regarding their involvement in medical decision making, and to explore factors that may affect these preferences.  相似文献   
28.

Objectives:

To compare the mean total antioxidant status (TAS) among 3 glaucoma types, namely: pseudoexfoliation glaucoma (PEG), primary open angle glaucoma (POAG), and primary angle closure glaucoma (PACG), and study its potential association with various clinical glaucoma-parameters.

Methods:

In this case-control study, plasma samples were obtained between September 2013 and October 2014 from 340 glaucoma patients (PEG [n=54]; POAG [n=147]; PACG [n=139]), and 351 controls of matching age, gender, ethnicity, and 5 different systemic co-morbidities from King Abdulaziz University Hospital, Riyadh, Saudi Arabia. The TAS in all samples was determined by a colorimetric-based assay.

Results:

The mean±standard deviation of TAS was significantly lower among cases: 0.77±0.32 than controls: 1.1±0.22, p<0.0001. Moreover, the TAS levels were significantly different across the 3 types of glaucoma: 0.86±0.24 in PEG, 0.47±0.32 in POAG, and 0.98±0.41 in PACG (all p<0.0001). In addition, there was a significant correlation between TAS and age at onset (Pearson correlation coefficient [R] 0.17, p<0.0001), cup/disc ratio (R: -0.13, p=0.004), and number of anti-glaucoma medications (R: -0.16, p=0.001).

Conclusion:

Our findings provide evidence that plasma TAS levels are decreased in patients with glaucoma, more so in POAG and PEG than PACG, supporting the hypothesis that decreased antioxidative defense and/or increased oxidative stress may have a critical role in the pathogenesis of glaucoma.Glaucoma is a progressive optic neuropathy associated with optic nerve damage, and is one of the most leading cause of blindness worldwide.1 Elevated intraocular pressure (IOP) as a result of reduction in normal aqueous outflow is a major causal risk factor that is well supported by animal studies.2-4 Although IOP is considered a major risk factor for glaucoma,2,3 other concomitant factors affecting the pathophysiology of glaucomatous retinal ganglion cell (RGC) death include retinal ischemia,5 nutritional status,6 and oxidative stress.7 There is evidence of oxidative damage in ocular diseases, such as cataract and age-related macular degeneration.8 In addition, significant oxidative damage has been demonstrated in human trabecular meshwork (TM) cells of patients with glaucoma,7 causing elevated IOP and visual field damage.9 Furthermore, our previous studies have documented mitochondrial abnormalities10-12 (oxidative stress marker), and glutathione-S-transferase (antioxidant) gene (GST) polymorphisms to be associated with various types of glaucoma.13 It is clearly evident from the literature, and our own studies, that oxidative stress mechanisms play a critical role in the pathogenesis of glaucoma. Previous studies had demonstrated reduced total antioxidant capacity in aqueous humor and blood samples from patients with glaucoma.14-17 To evaluate the role of oxidative stress in different types of glaucoma we had previously investigated total antioxidants status (TAS) in the plasma of pseudoexfoliation glaucoma (PEG) patients,18 primary angle closure glaucoma (PACG) patients,19 and in the plasma of primary open angle glaucoma (POAG) patients.20 As an extension to these studies, here, we compare the mean TAS level among these 3 glaucoma types, and study the potential association between the TAS level and various clinical parameters important to each type of glaucoma.18-20  相似文献   
29.
Endosonography of the anal sphincters in solitary rectal ulcer syndrome   总被引:1,自引:0,他引:1  
Twenty-one patients with histologically proven solitary rectal ulcer syndrome (SRUS) were examined by anal endosonography (AES) in order to determine the frequency of any ultrasound abnormality. Comparison was made with a group of 17 age and sex matched asymptomatic subjects. Four patients with SRUS had anal sphincter defects on AES. All were of the internal anal sphincter (IAS), which appeared fragmented in two patients with complete rectal prolapse. Measurements of internal and external anal sphincter (EAS) diameter and cross-sectional crea were taken, excluding the 4 patients with defects. The submucosa was inhomogeneous (P=0.0016) and thickness increased in patients with SRUS (median 4.0 mm vs 2.0 mm; P<0.0001). IAS diameter was increased (median 3.8 mm vs 2.0 mm; P<0.0001), as was cross-sectional area (median 241 sq mm vs 112 sq mm; P<0.0001). EAS diameter was also increased (median 8.5 mm vs 7.0 mm; P=0.0173), as was cross-sectional area (median 905 sq mm vs 594 sq mm; P=0.0052). The ratio of EAS to IAS thickness was reduced in patients with SRUS (median 2.6 vs 4.0; P=0.0029). The mechanism of these changes is unclear but apparent muscle hypertrophy on ultrasound may diagnose those patients with SRUS in whom defecatory difficulty is a predominant symptom.
Résumé Vingt-et-un patients présentant un ulcère solitaire du rectum prouvé histologiquement (SRUS) ont été examinés par échographie endo-anale (AES) afin de déterminer la fréquence d'anomalies échographiques. Une comparison a été établie avec un groupe de 17 sujets asymptomatiques comparatifs quant à l'âge et au sexe. Quatre patients avec un SRUS présentaient des défects sphinctériens à l'échographie. Toutes les anomalies poraient sur le sphincter interne qui apparaissait comme fragmenté chez deux patients porteurs d'un prolapsus complet du rectum. Des mesures du diamètre et de la surface de section des sphincters internes et externes ont été établies à l'exclusion des 4 patients-présentant des défauts sphinctériens. La sous-muqueuseétait inhomogène (P=0.007) et le sphincter était épaissi chez des patients porteurs d'un ulcère solitaire (médiane 4,0 mm versus 2,0 mm; P<0.0001). Le diamètre du sphincter interne était augmenté (médiane 3,8 mm versus 2,0 mm; P<0.0001), de même que la surface de section (médiane 241 mm2 versus 112 mm2, P<0,0001). Le diamètre du sphincter externe était également augmenté (8,5 mm versus 7,0 mm; P=0.0173), de même que la surface de la section (mediane 905 mm2 versus 504 mm2; P=0.0052). Le ratio de l'épaisseur du sphincter externe par rapport à l'épaisseur du sphincter interne était réduit chez les patients porteurs d'un ulcère solitaire du rectum (médiane 2,6 versus 4,0; P=0.0029). Le canisme de ces changements n'est pas clair mais l'hypertrophie apparente du muscle lors de l'examen échographique permet d'identifier les patients porteurs d'un ulcère solitaire du rectum chez lesquels des problèmes d'exonération constitutent un symptôme prédominant.
  相似文献   
30.

Objective

Oxidative metabolism is impaired in several medical conditions including psychiatric disorders, and this imbalance may be involved in the etiology of these diseases. The present study evaluated oxidative balance in pediatric and adolescent patients with attention deficit hyperactivity disorder (ADHD).

Methods

The study included 48 children and adolescents (34 male, 14 female) with ADHD who had no neurological, systemic, or comorbid psychiatric disorders, with the exception of oppositional defiant disorder (ODD), and 24 sex- and age-matched healthy controls (17 male and seven female).

Results

TAS was significantly lower, and TOS and OSI were significantly higher in patients with ADHD than in healthy controls. Total antioxidant levels were lower in patients with comorbid ODD than in those with no comorbidity. No difference was found in TOS or OSI among the ADHD subtypes; however, TAS was higher in the attention-deficient subtype.

Conclusion

Our findings demonstrated that oxidative balance is impaired and oxidative stress is increased in children and adolescents with ADHD. This results are consistent with those of previous studies.  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