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   1474篇
  免费   117篇
  国内免费   3篇
耳鼻咽喉   7篇
儿科学   44篇
妇产科学   29篇
基础医学   173篇
口腔科学   25篇
临床医学   304篇
内科学   255篇
皮肤病学   35篇
神经病学   154篇
特种医学   38篇
外科学   135篇
综合类   31篇
一般理论   1篇
预防医学   180篇
眼科学   23篇
药学   94篇
中国医学   2篇
肿瘤学   64篇
  2023年   9篇
  2022年   14篇
  2021年   29篇
  2020年   20篇
  2019年   24篇
  2018年   29篇
  2017年   27篇
  2016年   25篇
  2015年   23篇
  2014年   42篇
  2013年   74篇
  2012年   85篇
  2011年   89篇
  2010年   53篇
  2009年   40篇
  2008年   93篇
  2007年   88篇
  2006年   105篇
  2005年   123篇
  2004年   113篇
  2003年   97篇
  2002年   85篇
  2001年   17篇
  2000年   18篇
  1999年   11篇
  1998年   24篇
  1997年   7篇
  1996年   11篇
  1995年   5篇
  1993年   7篇
  1992年   5篇
  1991年   14篇
  1990年   10篇
  1989年   9篇
  1988年   11篇
  1987年   15篇
  1986年   6篇
  1985年   13篇
  1984年   10篇
  1983年   15篇
  1982年   6篇
  1978年   7篇
  1977年   5篇
  1976年   9篇
  1974年   5篇
  1973年   8篇
  1972年   10篇
  1971年   7篇
  1970年   4篇
  1968年   4篇
排序方式: 共有1594条查询结果,搜索用时 27 毫秒
61.
Cultured muscle fibers (CMF) from a patient with inclusion-body myositis (IBM) and cardiac amyloidosis associated with the transthyretin (TTR) Val122Ile mutation contained aspects of the IBM phenotype: vacuolation, congophilic inclusions, and clusters of immunocolocalizing amyloid beta-peptide (Abeta) and TTR accumulations. These abnormalities are never present in normal human CMF. These perturbations were greatly increased after Abeta precursor protein gene transfer. The TTR mutation may be a genetic predisposition factor for the patient's IBM.  相似文献   
62.
RATIONALE AND OBJECTIVES: The authors performed this study to investigate the causes of interscan variability of coronary artery calcium measurements at electron-beam computed tomography (CT). MATERIALS AND METHODS: Two sets of electron-beam CT scans were obtained in 298 consecutive patients who underwent electron-beam CT to screen for coronary artery calcium. Interscan variations of coronary artery calcium characteristics and the effects of heart rate, electrocardiographic (ECG) triggering method, image noise, and coronary motion on interscan variability were analyzed. RESULTS: The interscan mean variabilities were 21.6% (median, 11.7%) and 17.8% (median, 10.8%) with the Agatston and volumetric score, respectively (P < .01). Variability decreased with increasing calcification score (34.6% for a score of 11-50 and 9.4% for a score of 400-1,000, P < .0001). The absolute difference in Agatston score between scans was 44.1 +/- 95.6. The correlation coefficient between the first and second sets of scans was 0.99 (P < .0001). Lower interscan variability was found in younger patients (<60 years), patients with stable heart rates (heart rate changing less than 10 beats per minute during scanning), patients with no visible coronary motion, and those with an optimal ECG triggering method (P < .05 for all). Results of multivariate logistic analysis showed that changes in calcium volume, mean attenuation, and peak attenuation were significant predictors of interscan variability and caused the interscan variations of the coronary artery calcium measurements (r2 = 0.83, P < .0001). CONCLUSION: Coronary calcification at electron-beam CT varies from scan to scan. Volumetric scoring and optimal ECG triggering should be used to reduce interscan variability. Baseline calcium score and interscan variability must be considered in the evaluation of calcium progression.  相似文献   
63.
Purpose: To investigate the incidence, significance, and mechanism of stent-graft distortion after endovascular repair (EVR) of abdominal aortic aneurysm. Methods: EVR of abdominal aortic aneurysm was performed in 51 cases (49 modular, bifurcated; 2 tube). Thirty-two patients were followed for 6 or more months and had equivalent baseline and follow-up images which could be used to determine changes in graft configuration. Sac dimensions were measured using computed tomographic (CT) images and graft-related complications were recorded. Results: Amongst 32 patients evaluated on follow-up, there was graft distortion in 24. Distorted grafts were significantly (p= 0.002) associated with sac diameter reduction (mean 5 mm) and sac length reduction (mean 8.1 mm). All graft-related complications occurred in the limbs of eight distorted grafts, with a mean reduction of sac length in this group of 7.8 mm on reformatted CT images. Conclusion: There was a highly significant association between graft distortion and limb complications, and reduced sac dimensions.  相似文献   
64.
BACKGROUND: The adequate control of blood pressure in patients with diabetes mellitus (DM) is important to limit the ocular and systemic complications of the disease. Hypertension in African Americans is among the highest in the world. This cross-sectional study reports the level of blood pressure control in a small sample of African American patients with DM at an urban eye care facility using the criteria defined by the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC VII). METHODS: Five attending faculty members of the Illinois College of Optometry identified 234 African American patients with a diagnosis of DM over a period of 16 months. Blood pressure readings were recorded once at the time of their visit and were classified as controlled or uncontrolled based on the JNC VII cutoff of blood pressure less than 130/80 mmHg. RESULTS: Among the 234 African American patients in this study, 174 (74.4%) reported having DM and hypertension, and 60 (25.6%) reported having DM without hypertension. Of the patients with DM and a self-reported diagnosis of hypertension, 13.2% were controlled. Of the patients with diabetes without a self-reported diagnosis of hypertension, 26.7% were found to be adequately controlled. For the pooled data of 234 patients with diabetes, 16.7% met the JNC VII guidelines. CONCLUSION: The inadequate control of blood pressure in the African American population with DM is associated with increased disability and death from cardiovascular and renal disease. The results of this small cross-sectional study are consistent with those of other studies that show poor control of blood pressure in African American patients who have DM. Preventable blindness secondary to accelerated diabetic retinopathy from uncontrolled hypertension is a concern to all eye care practitioners.  相似文献   
65.
Thirty patients were selected to bleach their maxillary teeth. Vacuum-formed trays were fabricated for the maxillary arch so that only one quadrant of bleaching tray had reservoirs. Nupro Gold 10% carbamide peroxide gel was given to patients. They were instructed to place a drop of gel in each tooth area and wear the trays twice a day for two-hour periods. After 10 days the patients were evaluated for shade changes in each quadrant. No clinical difference was observed in the after-shade match of the two quadrants. It appears that the addition of blockout spacers to create reservoirs does not increase the success of home bleaching.  相似文献   
66.
BACKGROUND: Two main models are currently used to evaluate psychosocial factors at work: the Job Strain model developed by Karasek and the Effort-Reward Imbalance model. A French version of the first model has been validated for the dimensions of psychological demands and decision latitude. As regards the second one evaluating three dimensions (extrinsic effort, reward, and intrinsic effort), there are several versions in different languages, but until recently there was no validated French version. The objective of this study was to explore the psychometric properties of the French version of the Effort-Reward Imbalance model in terms of internal consistency, factorial validity, and discriminant validity. METHODS: The present study was based on the GAZEL cohort and included the 10 174 subjects who were working at the French national electric and gas company (EDF-GDF) and answered the questionnaire in 1998. A French version of Effort-Reward Imbalance was included in this questionnaire. This version was obtained by a standard forward/backward translation procedure. RESULTS: Internal consistency was satisfactory for the three scales of extrinsic effort, reward, and intrinsic effort: Cronbach's Alpha coefficients higher than 0.7 were observed. A one-factor solution was retained for the factor analysis of the scale of extrinsic effort. A three-factor solution was retained for the factor analysis of reward, and these dimensions were interpreted as the factor analysis of intrinsic effort did not support the expected four-dimension structure. The analysis of discriminant validity displayed significant associations between measures of Effort-Reward Imbalance and the variables of sex, age, education level, and occupational grade. CONCLUSION: This study is the first one supporting satisfactory psychometric properties of the French version of the Effort-Reward Imbalance model. However, the factorial validity of intrinsic effort could be questioned. Furthermore, as most previous studies were based on male samples working in specific occupations, the present one is also one of the first to show strong associations between measures of this model and social class variables in a population of men and women employed in various occupations.  相似文献   
67.
Mature monocytic cells enter tissues and engraft   总被引:9,自引:0,他引:9       下载免费PDF全文
The goal of this study was to identify the circulating cell that is the immediate precursor of tissue macrophages. ROSA 26 marrow mononuclear cells (containing the β-geo transgene that encodes β-galactosidase and neomycin resistance activities) were cultured in the presence of macrophage colony-stimulating factor and flt3 Ligand for 6 days to generate monocytic cells at all stages of maturation. Expanded monocyte cells (EMC), the immature (ER-MP12+) and more mature (ER-MP20+) subpopulations, were transplanted into irradiated B6/129 F2 mice. β-gal staining of tissue sections from animals 15 min after transplantation demonstrated that the donor cells landed randomly. By 3 h, donor cells in lung and liver were more frequent in animals transplanted with ER-MP20+ (more mature) EMC than in animals transplanted with unseparated EMC or fresh marrow mononuclear cells, a pattern that persisted at 3 and 7 days. At 3 days, donor cells were found in spleen, liver, lung, and brain (rarely) as clusters as well as individual cells. By 7 and 14 days, the clusters had increased in size, and the cells expressed the macrophage antigen F4/80, suggesting that further replication and differentiation had occurred. PCR for the neogene was used to quantitate the amount of donor DNA in tissues from transplanted animals and confirmed that ER-MP20+ EMC preferentially engrafted. These data demonstrate that a mature monocytic cell gives rise to tissue macrophages. Because these cells can be expanded and manipulated in vitro, they may be a suitable target population for gene therapy of lysosomal storage diseases.  相似文献   
68.
69.
RATIONALE AND OBJECTIVE: The newest generation of electron beam tomographic scanner (e-Speed) has increased spatial and temporal resolution compared with the C-150 XP scanner. The aim of this study was to evaluate coronary artery calcium screening image quality between the e-Speed and C-150 scanners (GE Imatron, San Francisco, CA). MATERIALS AND METHODS: Studies from 41 patients (14 women and 27 men) who underwent serial coronary artery calcium screening with the C-150 (first study) and the e-Speed (second study) were analyzed. Individual computed tomography (CT) slices were assessed for coronary artery motion artifacts, and CT Hounsfield units (HU) and noise values (CT HU standard deviation) at 16 discrete cardiac sites were measured and averaged. RESULTS: With the e-Speed scanner, there were significant decreases in right coronary artery motion artifacts compared with the C-150 scanner (0.3% versus 1.8%, P < .001) as well as decreased noise values (24.3 versus 32.0 HU, P < .001). CONCLUSION: Image quality is significantly improved with use of the e-Speed scanner, due to its improved temporal and spatial resolution, compared with the C-150 scanner.  相似文献   
70.
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