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   11241篇
  免费   486篇
  国内免费   77篇
耳鼻咽喉   258篇
儿科学   480篇
妇产科学   385篇
基础医学   1009篇
口腔科学   406篇
临床医学   926篇
内科学   2629篇
皮肤病学   185篇
神经病学   679篇
特种医学   503篇
外科学   2253篇
综合类   253篇
一般理论   3篇
预防医学   451篇
眼科学   245篇
药学   618篇
中国医学   36篇
肿瘤学   485篇
  2024年   7篇
  2023年   107篇
  2022年   230篇
  2021年   390篇
  2020年   202篇
  2019年   274篇
  2018年   322篇
  2017年   236篇
  2016年   366篇
  2015年   423篇
  2014年   528篇
  2013年   609篇
  2012年   774篇
  2011年   779篇
  2010年   467篇
  2009年   409篇
  2008年   768篇
  2007年   868篇
  2006年   849篇
  2005年   779篇
  2004年   663篇
  2003年   538篇
  2002年   476篇
  2001年   86篇
  2000年   79篇
  1999年   66篇
  1998年   60篇
  1997年   41篇
  1996年   51篇
  1995年   29篇
  1994年   21篇
  1993年   22篇
  1992年   23篇
  1991年   20篇
  1990年   24篇
  1989年   31篇
  1988年   20篇
  1987年   19篇
  1986年   18篇
  1985年   18篇
  1984年   8篇
  1983年   11篇
  1982年   6篇
  1980年   6篇
  1979年   7篇
  1978年   8篇
  1974年   5篇
  1973年   9篇
  1972年   7篇
  1971年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
BackgroundPRF treatment has recently been described as minimally neurodestructive alternative to radiofrequency heat lesions. Patients with some pain syndromes in whom the pain could not be controlled by alternative techniques may be treated using PRF. In the present study, our main goal was to evaluate and compare the ultrastructure of peripheral nerve tissue that was heated by PRF, CRF with 42°C, and CRF with 70°C.MethodsForty-five male rats were divided into 5 groups. In PRF group and CRF with 42°C group, the sciatic nerve was heated at a temperature of 42°C for 120 seconds. As a positive control, some rat sciatic nerves were treated with CRF lesions at 70°C. The rats were kept alive for 21 days and then killed. Tissue was evaluated with transmission electron microscope, and grading was done to the groups.ResultsThe unmyelinated nerve fibers were ultrastructurally normal in all groups. The results of myelinated axons indicated that PRF group had better grades, and CRF with 70°C group had the worst grade. Especially, comparison of the group of PRF and CRF with 42°C revealed significant difference. In PRF group, none of the myelinated axons showed severe degeneration findings, and most of the damaged myelinated axons showed only separation in myelin configuration.ConclusionsPRF treatment may cause separation in myelinated axons. However, it seems that all changes were reversible. The present study supports the hypothesis that pulsed RF treatment does not rely on thermal injury of neurologic tissue to achieve its effect.  相似文献   
72.
The stability of the shoulder is dependent on both static and dynamic anatomic restraints. In most cases, there must be insufficiency of more than one restraint for the shoulder joint to become instable. Although the role of these restraints is largely known in maintaining shoulder stability, our information on their interactions is insufficient. This article reviews the anatomy and biomechanics of the shoulder and conditions causing instability of the glenohumeral joint.  相似文献   
73.
Pseudoaneurysm of the thoracic aorta is a rare condition and usually occurs following blunt trauma. It is almost fatal in the absence of prompt surgical treatment. We describe the case of a 56-year-old male suffering from intermittent non-massive hemoptysis, mild dysphagia, and atypical chest pain for 1 month who has no history of trauma. A saccular aneurysm at the aortic arch between left common carotid artery and left subclavian artery was diagnosed by magnetic resonance imaging. Intraoperatively, compression of surrounding structures including trachea and esophagus by the aneurysmal sac (6 x 8 cm in diameter) was seen. Pseudoaneurysm adherent to the upper lobe of the left lung was resected and entire aortic arch replacement with a prosthetic graft was performed. Postoperative course was uneventful and neither specific changes on histologic examination nor any evidence of infection could be detected.  相似文献   
74.
Adenocarcinomas of the jejunum and ileum are rare gastrointestinal malignancies. Because few large published experiences exist, we reviewed patients with jejunal and ileal adenocarcinoma treated at our institution over the last 25 years. Between January 1976 and December 2001, 77 patients had an operation for a jejunal or ileal adenocarcinoma. Records were retrospectively reviewed for patient, tumor, and treatment variables. Factors affecting disease recurrence and patient survival were investigated. Fifty-two of the adenocarcinomas (67%) occurred in the jejunum and 25 occured in the ileum (33%). Mean patient age was 63 ±14 years. Segmental bowel resection was performed in 50 patients (65%) with curative intent. Palliative operative procedures including resection or bypass were performed in 27 patients (35%). One (1%) patient had stage I, 18 (23%) stage II, 19 (25%) stage III, and 39 (51%) stage IV adenocarcinoma at diagnosis. Postoperatively, 12 patients had palliative and 18 adjuvant chemotherapy (n 5 30), radiation therapy (n = 1), or combination treatment (n = 7). Median patient survival was 19 months. Sixty-six percent of patients who had a curative operation had a tumor relapse. Tumor stage had a highly significant effect (P < 0.0001) on median survival (72 months for stage I and II, 30 months for stage III, and 9 months for stage IV disease). In multivariate analysis of patients having curative treatment, tumor recurrence (P < 0.0001), stage (P < 0.0002), and weight loss (P < 0.001) were significant negative prognostic indicators. Most patients with adenocarcinoma of the jejunum or ileum present with advanced disease. Tumor stage, disease recurrence, and weight loss predicted patient outcome following a curative operation. Early recognition of these tumors requires a high index of suspicion. Presented at the Forty-Fifth Annual Meeting of The Society for Surgery of the Alimentary Tract, New Orleans, Louisana, May 15–19, 2004 (poster presentation).  相似文献   
75.
To investigate the effect of cyclosporine A (Cyc A) on the development of fibroadenomas, 30 renal transplant patients and 20 chronic renal failure patients on dialysis were breast examined with ultrasonography and/or mammography. Of the renal transplant patients, 17 were receiving Cyc A-based combination therapy for immunosuppression. All patients were female with the age range of 29.7+/-9.2 years in the transplant group and 33.95+/-9.91 in the dialysis group. Eight of the 17 patients receiving Cyc A had fibroadenomas, 5 of them having bilateral lesions. None of the other patients, those on dialysis and on non-Cyc A combination therapy had fibroadenomas. A significant difference for fibroadenoma incidence in patients receiving Cyc A combination immunosuppression was found.  相似文献   
76.
We investigated whether a proximal femoral nail (PFN) having two lag screws can be implanted without distal locking screws in AO/OTA 31-A1 and 31-A2 intertrochanteric femur fractures. Twenty-four patients with AO/OTA 31-A1 and 31-A2 fractures were treated with a PFN without distal interlocking by a single surgeon. The mean follow-up was 12 months (range: 7–23). Clinical and functional outcome was assessed according to the Harris hip score and Barthel’s activity score. The fractures healed in all patients; the average consolidation time was 14 weeks (range: 9–28). Fourteen patients had excellent and good results, nine patients had fair results, and one patient had a poor result according to the Harris hip score; 17 patients had a high range of mobility according to the Barthel activity score. Our results suggested that the PFN can be successfully implanted without distal interlocking in 31-A1 and 31-A2 fractures.  相似文献   
77.
Suicide has been reported as the second or third most common cause of death in children and adolescents all over the world. The aim of the study was to investigate the general properties of suicide in childhood and adolescents, and to evaluate the results in the light of literature. Reports of autopsies performed between 2001 and 2005 in the Morgue Department of the Council of Forensic Medicine in Istanbul (n = 16853) were examined retrospectively. Deaths between 0–18 years of age doubtlessly considered as suicide were included in the study. Childhood and adolescent (0–18 years) deaths comprised 10.4% (n = 1761) of all medico-legal autopsy cases. 136 cases of suicidal origin were evaluated in terms of age, gender, and method of suicide. The ages ranged between 7 and 18, with a mean of 15.54 ± 2.691(SD). The most common method of suicide was hanging (59.2%) in both genders. Older adolescents (16–18 age group) constituted the overwhelming number (63.2%, n = 86) of all cases. Seven cases of 10 years of age and below were determined, and hanging was the method of suicide in five of these cases. In order to prevent childhood suicides, families and society should be aware of their responsibilities.  相似文献   
78.

Objective

The purpose of this study was to prospectively evaluate the two different ultrasound-guided injection techniques for MR arthrography of the hip.

Materials and methods

Fifty-nine consecutive patients (21 men, 38 women) referred for MR arthrographies of the hip were prospectively included in the study. Three patients underwent bilateral MR arthrography. The two injection techniques were quantitatively and qualitatively compared. Quantitative analysis was performed by the comparison of injected contrast material volume into the hip joint. Qualitative analysis was performed with regard to extraarticular leakage of contrast material into the soft tissues. Extraarticular leakage of contrast material was graded as none, minimal, moderate, or severe according to the MR images. Each patient rated discomfort after the procedure using a visual analogue scale (VAS).

Results

The injected contrast material volume was less in femoral head puncture technique (mean 8.9?±?3.4?ml) when compared to femoral neck puncture technique (mean 11.2?±?2.9?ml) (p?<?0.05). The chi-squared test showed significantly more contrast leakage by femoral head puncture technique (p?<?0.05). Statistical analysis showed no difference between the head and neck puncture groups in terms of feeling of pain (p?=?0.744) or in the body mass index (p?=?0.658) of the patients.

Conclusion

The femoral neck injection technique provides high intraarticular contrast volume and produces less extraarticular contrast leakage than the femoral head injection technique when US guidance is used for MR arthrography of the hip.  相似文献   
79.
AimThe purpose of our study was to determine the relationship between liver ultrasound scores and insulin sensitivity in a population of obese children with nonalcoholic fatty liver disease (NAFLD) and the relationships between other metabolic features and ultrasound scores.MethodsOne hundred sixty-nine obese adolescents, 96 girls, and 73 boys (mean age: 12.7±1.3 years, mean body mass index: 26.3±4.6) were enrolled the study. The obese subjects were divided into 2 groups based on their pubertal status. Ultrasonography findings were scored in this study included hepatorenal echo contrast, liver brightness, deep attenuation, and vascular blurring. Scores ranged from 0 to 6 points, and NAFLD was defined if ultrasound score was ≥ 1. Insulin resistance was evaluated by homeostasis model assessment (HOMA-IR) from fasting samples.ResultsPrevalence of NAFLD in pubertal children (61.9%) had significantly higher than pre-pubertal children (40.8%) (P= .008). Transaminases ratio was significantly correlated in both prepubertal (r= 0.231; P= .03) and pubertal (r= 0.628, P= 0.017) groups. HOMA-IR values were elevated in both groups; however, liver ultrasound score was positively correlated with HOMA-IR (r= 0.735, P= .014) in pubertal children.ConclusionNAFLD prevalence among obese children is quite high, especially pubertal adolescents than prepubertal children. We demonstrated an association between insulin resistance and NAFLD ultrasound scoring in pubertal obese children. We suggested that ultrasound examination of the liver be included in the routine check-up of the pubertal obese children with insulin resistance to allow the detection of NAFLD at an early stage.  相似文献   
80.
Most experiments assume a global transit delay time with blood flowing from the tagging region to the imaging slice in plug flow without any dispersion of the magnetization. However, because of cardiac pulsation, nonuniform cross‐sectional flow profile, and complex vessel networks, the transit delay time is not a single value but follows a distribution. In this study, we explored the regional effects of magnetization dispersion on quantitative perfusion imaging for varying transit times within a very large interval from the direct comparison of pulsed, pseudo‐continuous, and dual‐coil continuous arterial spin labeling encoding schemes. Longer distances between tagging and imaging region typically used for continuous tagging schemes enhance the regional bias on the quantitative cerebral blood flow measurement causing an underestimation up to 37% when plug flow is assumed as in the standard model. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.  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