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   1307篇
  免费   138篇
  国内免费   44篇
耳鼻咽喉   12篇
儿科学   75篇
妇产科学   27篇
基础医学   153篇
口腔科学   65篇
临床医学   135篇
内科学   287篇
皮肤病学   19篇
神经病学   101篇
特种医学   222篇
外科学   159篇
综合类   19篇
一般理论   2篇
预防医学   67篇
眼科学   23篇
药学   62篇
中国医学   1篇
肿瘤学   60篇
  2021年   12篇
  2020年   13篇
  2019年   29篇
  2018年   29篇
  2017年   11篇
  2016年   17篇
  2015年   32篇
  2014年   36篇
  2013年   46篇
  2012年   44篇
  2011年   51篇
  2010年   33篇
  2009年   41篇
  2008年   38篇
  2007年   60篇
  2006年   50篇
  2005年   44篇
  2004年   35篇
  2003年   22篇
  2002年   36篇
  2001年   30篇
  2000年   29篇
  1999年   30篇
  1998年   51篇
  1997年   43篇
  1996年   42篇
  1995年   34篇
  1994年   56篇
  1993年   30篇
  1992年   29篇
  1991年   20篇
  1990年   19篇
  1989年   51篇
  1988年   53篇
  1987年   49篇
  1986年   39篇
  1985年   29篇
  1984年   28篇
  1983年   19篇
  1982年   13篇
  1981年   9篇
  1980年   10篇
  1979年   10篇
  1977年   10篇
  1976年   9篇
  1975年   6篇
  1972年   6篇
  1971年   6篇
  1970年   11篇
  1969年   7篇
排序方式: 共有1489条查询结果,搜索用时 18 毫秒
51.
Pulmonary histiocytosis X: comparison of radiographic and CT findings   总被引:6,自引:0,他引:6  
The authors retrospectively evaluated radiographs, computed tomographic (CT) scans, and results of pulmonary function tests (when available) for 17 patients with biopsy-proved pulmonary histiocytosis X. In 11 patients, high-resolution CT was used. In 12 patients, CT demonstrated cystic air spaces, usually less than 10 mm in diameter. In three of these 12, cysts were the only abnormality, but in six others, nodules (usually less than 5 mm in diameter) were also present. Two patients had only nodules and one, only emphysema. CT showed that many lesions that appeared reticular on plain radiographs were actually cysts. CT showed no central or peripheral concentration of lesions, but it did reveal that many small nodules were distributed in the centers of secondary lobules around small airways. CT findings correlated better with the diffusing capacity (rho = -0.71) than did the plain radiographic findings (rho = -0.57). Thus, CT was better than radiography at showing the morphology and distribution of lung abnormalities.  相似文献   
52.
Color Doppler flow imaging or compression ultrasound (US) was used to prospectively determine frequency of thrombosis at 54 venous insertion sites (47 in common femoral veins, seven in right internal jugular veins) after percutaneous placement of Greenfield filters for interruption of the inferior vena cava. Fifty-one filters were successfully placed in 51 patients with a dilator set or a balloon angioplasty catheter. Nine focal thrombi were detected in the common femoral vein (19%) and one in the right internal jugular vein (14%). Use of dilators induced eight thrombi (24%), compared with two (10%) from balloon catheters. The left common femoral vein had a high frequency of thrombosis, regardless of dilation technique (five of nine). Of nine patients with acute common femoral vein thrombosis, four became symptomatic within 10 days after the procedure. Patients may remain asymptomatic or have delayed symptoms; thus, US is valuable for determining patients at risk of thrombosis of the common femoral vein.  相似文献   
53.
Tempkin  DL; Ladika  JE 《Radiology》1987,163(1):275-276
An improved catheter for pulmonary arteriography via the antecubital approach is described. The catheter has been used successfully in 56 patients.  相似文献   
54.
Nyberg  DA; Filly  RA; Filho  DL; Laing  FC; Mahony  BS 《Radiology》1986,158(2):393-396
Simultaneous sonography and quantitative serum human chorionic gonadotropin (HCG) levels from 126 women with threatened abortion were compared. Of 56 women with normal outcome, 39 (70%) had a gestation sac greater than or equal to 5 mm in mean sac diameter, and in each case the HCG level was 1,800 milli-international units (mIU/ml) or greater. The serum HCG levels strongly correlated with the gestation sac sizes to a mean sac diameter of 25 mm. Of 70 abnormal pregnancies, 31 demonstrated a gestation sac. Of these, 20 women (65%) had disproportionately low HCG levels relative to sac size, including 12 in whom the HCG level was less than 1,800 mIU/ml. One woman with an early molar pregnancy had a disproportionately elevated HCG level. Correlation of sonograms with a simultaneous measurement of serum HCG level is a useful method for evaluating threatened spontaneous abortion. A disproportionately low HCG level relative to gestation sac size is evidence for an abnormal pregnancy.  相似文献   
55.

Objective

Recently, interspinous process devices have attracted much attention since they can be implanted between the lumbar spinous processes (LSP) of patients with degenerative disc disease (DDD) and degenerative spondylolisthesis (DLS) using a minimally invasive manner. However, the motion characters of the LSP in the DLS and DDD patients have not been reported. This study is aimed at investigating the kinematics of the lumbar spinous processes in patients with DLS and DDD.

Methods

Ten patients with DDD at L4–S1 and ten patients with DLS at L4–L5 were studied. The positions of the vertebrae (L2–L5) at supine, standing, 45° trunk flexion, and maximal extension positions were determined using MRI-based models and dual fluoroscopic images. The shortest ISP distances were measured and compared with those of healthy subjects that have been previously reported.

Results

The shortest distance of the interspinous processes (ISP) gradually decreased from healthy subjects to DDD and to DLS patients when measured in the supine, standing, and extension positions. During supine-standing and flexion–extension activities, the changes in the shortest ISP distances in DDD patients were 2 ± 1.2 and 4.8 ± 2.1 mm at L4–L5; in DLS patients they were 0.5 ± 0.4 and 2.8 ± 1.7 mm at L4–L5, respectively. The range of motion is increased in DDD patients but decreased in DLS patients when compared with those of the healthy subjects. No significantly different changes were detected at L2–L3 and L3–L4 levels.

Conclusion

At the involved level, the hypermobility of the LSP was seen in DDD and hypomobility of the LSP in DLS patients. The data may be instrumental for improving ISP surgeries that are aimed at reducing post-operative complications such as bony fracture and device dislocations.  相似文献   
56.
57.
Objective:The PRECISE criteria for reporting multiparametric MRI in patients on active surveillance (AS) for prostate cancer (PCa) score the likelihood of clinically significant change over time using a 1–5 scale, where 4 or 5 indicates radiological progression. According to the PRECISE recommendations, the index lesion size can be reported using different definitions of volume (planimetry or ellipsoid formula) or by measuring one or two diameters. We compared different measurements using planimetry as the reference standard and stratified changes according to the PRECISE scores.Methods:We retrospectively analysed 196 patients on AS with PCa confirmed by targeted biopsy who had two MR scans (baseline and follow-up). Lesions were measured on T2 weighted imaging (T2WI) according to all definitions. A PRECISE score was assessed for each patient.Results:The ellipsoid formula exhibited the highest correlation with planimetry at baseline (ρ = 0.97) and follow-up (ρ = 0.98) imaging, compared to the biaxial measurement and single maximum diameter. There was a significant difference (p < 0.001) in the yearly percentage volume change between radiological regression/stability (PRECISE 2–3) and progression (PRECISE 4–5) for planimetry (39.64%) and for the ellipsoid formula (46.78%).Conclusion:The ellipsoid formula could be used to monitor tumour growth during AS. Evidence of a significant yearly percentage volume change between radiological regression/stability (PRECISE 2-3) and progression (PRECISE 4-5) has been also observed.Advances in knowledge:The ellipsoid formula is a reasonable surrogate for planimetry in capturing tumour volume changes on T2WI in patients on imaging-led AS. This is also associated with radiological changes using the PRECISE recommendations.  相似文献   
58.
雄激素对骨骼肌合成有明显影响,随着年龄增大,雄激素的下降常伴随肌量和肌力的下降。这种肌量和肌功能的下降,被称为少肌症或肌体老化,是老年人体质弱化(男性化减退)进展的关键事项。也是导致快速机能衰退及其不良后果的关键。雄激素水平下降对老年男性体质弱化(男性化减退)的潜在影响和对躯体功能的促进治疗作用无疑已经引起了相当的关注。本综述概述了近期关于肌肉老化、少肌症、老年体质弱化的概念、定义,并评估了关于雄激素和老年体质弱化的研究进展。近期源于观测性和介入性研究的证据强烈支持雄激素对老年男性肌量的作用,但雄激素对肌力和特有的躯体功能的效用并不明确。研究显示,雄激素治疗在老年男性中通常有良好的耐受性,而近期的研究则关注于雄激素的高剂量治疗和对于心血管风险较高人群的治疗。雄激素受体调节剂(SARMs)的初期试验研究显示传统雄激素治疗对于老年患者在肌量和肌功能方面有相同的效用。将来的重要研究方向包括利用这类雄激素治疗并结合适用于不同老年患者群体促进躯体功能的运动训练,同时将更多地关注近期关于激素水平、身体成分及躯体功能间关系的观测性(回顾性)研究。  相似文献   
59.
Background contextTraumatic fractures of the spine are most common at the thoracolumbar junction and can be a source of great disability.PurposeTo review the most current information regarding the pathophysiology, injury pattern, treatment options, and outcomes.Study designLiterature review.MethodsRelevant articles, textbook chapters, and abstracts covering thoracolumbar spine fractures with and without neurologic deficit from 1960 to the present were reviewed.ResultsThe thoracolumbar spine represents a unique system from a skeletal as well as neurological standpoint. The rigid rib-bearing thoracic spine articulates with the more mobile lumbar spine at the thoracolumbar junction (T10 - L2), the site of most fractures. A complete examination includes a careful neurologic examination of both motor and sensory systems. CT scans best describe bony detail while MRI is most efficient at describing soft tissues and neurological structures. The most recent classification system is that of the new Thoracolumbar Injury Classification and Severity Score. The different fracture types include compression fractures, burst fractures - both stable and unstable -, flexion-distraction injuries and fracture dislocations. Their treatment, both operative and non-operative depends on the degree of bony compromise, neurological involvement, and the integrity of the posterior ligamentous complex. Minimally invasive approaches to the care of thoracolumbar injuries have become more popular, thus, the evidence regarding their efficacy is presented. Finally, the treatment of osteoporotic fractures of the thoracolumbar spine is reviewed, including vertebroplasty and kyphoplasty, their risks and controversies, and senile burst fractures, as well.ConclusionsThoracolumbar spine fractures remain a significant source of potential morbidity. Advances in treatment have minimized the invasiveness of our surgery and in certain stable situations, eliminated it all together.  相似文献   
60.
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