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   1708篇
  免费   176篇
  国内免费   1篇
耳鼻咽喉   6篇
儿科学   35篇
妇产科学   38篇
基础医学   386篇
口腔科学   11篇
临床医学   127篇
内科学   323篇
皮肤病学   26篇
神经病学   79篇
特种医学   77篇
外科学   272篇
综合类   30篇
预防医学   215篇
眼科学   18篇
药学   100篇
肿瘤学   142篇
  2022年   9篇
  2021年   20篇
  2020年   15篇
  2019年   30篇
  2018年   33篇
  2017年   22篇
  2016年   33篇
  2015年   38篇
  2014年   38篇
  2013年   77篇
  2012年   92篇
  2011年   96篇
  2010年   54篇
  2009年   50篇
  2008年   81篇
  2007年   81篇
  2006年   67篇
  2005年   81篇
  2004年   86篇
  2003年   71篇
  2002年   79篇
  2001年   61篇
  2000年   55篇
  1999年   43篇
  1998年   23篇
  1997年   23篇
  1996年   10篇
  1995年   12篇
  1994年   26篇
  1993年   13篇
  1992年   34篇
  1991年   27篇
  1990年   31篇
  1989年   32篇
  1988年   31篇
  1987年   25篇
  1986年   27篇
  1985年   37篇
  1984年   21篇
  1983年   16篇
  1982年   13篇
  1981年   12篇
  1980年   15篇
  1979年   11篇
  1978年   11篇
  1976年   12篇
  1974年   10篇
  1972年   9篇
  1969年   8篇
  1967年   8篇
排序方式: 共有1885条查询结果,搜索用时 15 毫秒
991.
BackgroundPancreatic cystic lesions are an increasing problem and investigation of these cysts can be fraught with difficulty. There is currently no gold standard for diagnosis or surveillance. This review was undertaken to determine the present reliability of the characterisation, assessment of malignant potential and diagnosis of pancreatic cystic lesions using available imaging modalities.MethodsA Medline search using the terms ‘pancreatic’, ‘pancreas’, ‘cyst’, ‘cystic’, ‘lesions’, ‘imaging’, ‘PET’. ‘CT’, ‘MRI’ and ‘EUS’ was performed. Publications were screened to include studies examining the performance of CT, MRI, MRCP, EUS and 18-FDG PET in the determination of benign or malignant cysts, cyst morphology and specific diagnoses.ResultsNineteen studies were identified that met the inclusion criteria. 18-FDG PET had a sensitivity and specificity of 57.0–94.0% and 65.0–97.0% and an accuracy of 94% in determining benign versus malignant cysts. CT had a sensitivity and specificity of 36.3–71.4% and 63.9–100% in determining benign disease but had an accuracy of making a specific diagnosis of 39.0–44.7%. MRI had a sensitivity and specificity of 91.4–100.0% and 89.7% in assessing main pancreatic duct communication.ConclusionCT is a good quality initial investigation to be used in conjunction with clinical data. MRCP can add useful information regarding MPD communication but should be used judiciously. PET may have a role in equivocal cases to determine malignancy. Further examination of CT-PET in this patient group is warranted.  相似文献   
992.
993.
994.
995.
996.
997.
Pediatric mastocytosis   总被引:2,自引:0,他引:2  
Pediatric mastocytosis presents with heterogeneous cutaneous lesions and symptoms that are caused by increased numbers of tissue mast cells. In contrast with adult patients with mastocytosis, the course of pediatric patients is usually transient. Therefore, it has long been speculated that pediatric and adult mastocytosis may be based on different pathogenetic mechanisms. Indeed, new genetic findings now indicate differences in the pathogenesis. Adult patients usually express activating mutations of the growth factor receptor c-kit. Most children lack these mutations but sometimes carry other inactivating mutations of c-kit. Only children with progressive mastocytosis seem to express the activating mutations seen in adults. Causal treatment is not yet available, but H1 and H2 antihistamines may provide relief of symptoms. It is important to counsel patients and their parents carefully to avoid triggers that induce systemic mast cell degranulation.  相似文献   
998.

Background and purpose

Contouring variation is a well know uncertainty in modern radiotherapy. This study investigates the relationship between contouring variation, tumor control probability (TCP) and equivalent uniform dose (EUD) for conformal non-small cell lung cancer (NSCLC) radiotherapy.

Material and methods

Seven patients were retrospectively recruited to the study and multiple PTV contours were generated based on CT and PET imaging by three observers. Plans were created for each PTV volume. Volumes were analyzed geometrically using volume, location, dimension and conformity index (CI). Radiobiological plan analysis consisted of two TCP models and EUD. Spearman’s correlation coefficient (ρ) was used to quantify the association between geometric variation and radiobiological metrics.

Results

The variation in CI and TCP for the study was 0.66–0.90% and 0.19–0.68%. Changes in lateral dimension and volume were significantly correlated with TCP and EUD with an average ρ of −0.49 and 0.43 (p < 0.01) respectively.

Conclusions

TCP and geometric contour variation show significant correlation. This correlation was most significant for changes in lateral dimensions of PTV volumes. This association may be used in the assessment of contouring protocol violations in multicenter clinical trials and aid in the design of future contouring studies.  相似文献   
999.
A sizeable literature focusing on QOL in children and adolescents with epilepsy has been produced over the last few years. However, relatively little emphasis has been placed on defining these issues from direct exploration of children's and adolescents' views. Qualitative methodologies are proposed in this review as an appropriate means of eliciting such information. This review systematically investigated the extent to which studies of QOL in children and adolescents with epilepsy have used recognised qualitative methodology. Articles for inclusion were identified by searching the term 'epilepsy', combined with 'adolescent(s) and/or child(ren)' and 'psychosocial and/or quality of life'. Selected articles were reviewed and rated using CASP Guidelines for qualitative research by two independent raters. Seventeen studies were retrieved through literature search. Of these six used some form of qualitative methodology either individually or combined with quantitative methods. However, only one study met quality criteria for selection in this systematic review. A summary of both selected and excluded studies is presented and methodological limitations discussed. Recommendations for appropriate methodology for investigation of QOL issues in children and adolescents are given.  相似文献   
1000.
BACKGROUND: There is evidence to suggest that insufficient sleep may have an adverse effect on physical and psychological health. Previous studies have reported that when adjusting for major risk factors for cardiovascular disease and a number of demographic and social variables, sleeping 7-8 h each night is associated with lower mortality. These studies, however, have excluded any consideration of stress, which is known to be related to a number of behavioural risk factors for disease and, like sleep, may influence neurochemical, hormonal and immunological functioning. METHODS: This study revisits the associations between sleep duration, cardiovascular disease risk factors and mortality, taking into account the perceived stress of individuals. The data come from a cohort of working Scottish men and women recruited between 1970 and 1973; approximately half of the cohort was screened for a second time, 4-7 years after the baseline examination. RESULTS: For both men and women, higher self-perceived stress was associated with a reduction in the hours of sleep reported. The pattern of mortality from all causes and the pattern of mortality from cardiovascular disease were consistent for both men and women. When sleep was measured on one occasion only, the risk of dying was reduced for men sleeping more than 8 h in every 24 h compared with those sleeping 7-8 h over the same period. This was after adjustment had been made for age, marital status, social class, cardiovascular risk factors and stress. The risk of dying was increased for women sleeping less than 7 h in every 24 h compared with those sleeping 7-8 h over the same period, after similar adjustments. When the data from the 1st and 2nd screening were considered longitudinally, both men and women who reported that they slept less than 7 h on both occasions that they were questioned, had a greater risk of dying from any cause than those who had reported sleeping 7-8 h at both screenings, after adjusting for age, marital status, social class and stress. CONCLUSIONS: Short sleep over a prolonged period may be associated with an increased risk of mortality: men and women who reported sleeping fewer than 7 h in 24 on two occasions between 4 and 7 years apart, had greater risk of dying from any cause over a 25 year period than those who reported sleeping 7-8 h on both occasions that they were questioned.  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