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   1092178篇
  免费   73625篇
  国内免费   1417篇
耳鼻咽喉   15681篇
儿科学   35007篇
妇产科学   30382篇
基础医学   156012篇
口腔科学   30346篇
临床医学   95521篇
内科学   206444篇
皮肤病学   25074篇
神经病学   83224篇
特种医学   43218篇
外国民族医学   201篇
外科学   165050篇
综合类   21808篇
现状与发展   1篇
一般理论   264篇
预防医学   75854篇
眼科学   25395篇
药学   88468篇
  7篇
中国医学   2836篇
肿瘤学   66427篇
  2019年   7934篇
  2018年   11639篇
  2017年   9171篇
  2016年   10364篇
  2015年   11575篇
  2014年   15731篇
  2013年   22814篇
  2012年   31390篇
  2011年   33227篇
  2010年   19440篇
  2009年   18043篇
  2008年   30528篇
  2007年   32838篇
  2006年   33542篇
  2005年   31802篇
  2004年   30599篇
  2003年   29398篇
  2002年   28241篇
  2001年   60546篇
  2000年   61986篇
  1999年   51344篇
  1998年   12574篇
  1997年   11029篇
  1996年   11043篇
  1995年   10354篇
  1994年   9361篇
  1993年   8874篇
  1992年   38072篇
  1991年   36508篇
  1990年   36019篇
  1989年   34603篇
  1988年   31219篇
  1987年   30323篇
  1986年   28572篇
  1985年   26774篇
  1984年   19452篇
  1983年   16311篇
  1982年   8916篇
  1979年   17454篇
  1978年   11648篇
  1977年   10428篇
  1976年   9049篇
  1975年   10343篇
  1974年   12072篇
  1973年   11681篇
  1972年   11107篇
  1971年   10425篇
  1970年   9561篇
  1969年   9266篇
  1968年   8228篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
22.
23.
24.
25.
We report on a child with several café au lait spots in association with a lumbar lipomeningomyelocele as an apparently new association. Cutaneous markers, the identification of which plays a crucial role in the early diagnosis and management of spinal malformations, can accompany occult spinal dysraphism. Herein we report a case of lumbar lipomeningomyelocele associated with an overlying café au lait spot that served as a marker of occult spinal dysraphism. The patient also had segmental café au lait spots on the face, making the association unique.  相似文献   
26.
27.
28.
29.
Prevalence of osteoporosis is more than 50% in older adults, yet current clinical methods for diagnosis that rely on areal bone mineral density (aBMD) fail to detect most individuals who have a fragility fracture. Bone fragility can manifest in different forms, and a “one-size-fits-all” approach to diagnosis and management of osteoporosis may not be suitable. High-resolution peripheral quantitative computed tomography (HR-pQCT) provides additive information by capturing information about volumetric density and microarchitecture, but interpretation is challenging because of the complex interactions between the numerous properties measured. In this study, we propose that there are common combinations of bone properties, referred to as phenotypes, that are predisposed to different levels of fracture risk. Using HR-pQCT data from a multinational cohort (n = 5873, 71% female) between 40 and 96 years of age, we employed fuzzy c-means clustering, an unsupervised machine-learning method, to identify phenotypes of bone microarchitecture. Three clusters were identified, and using partial correlation analysis of HR-pQCT parameters, we characterized the clusters as low density, low volume, and healthy bone phenotypes. Most males were associated with the healthy bone phenotype, whereas females were more often associated with the low volume or low density bone phenotypes. Each phenotype had a significantly different cumulative hazard of major osteoporotic fracture (MOF) and of any incident osteoporotic fracture (p < 0.05). After adjustment for covariates (cohort, sex, and age), the low density followed by the low volume phenotype had the highest association with MOF (hazard ratio = 2.96 and 2.35, respectively), and significant associations were maintained when additionally adjusted for femoral neck aBMD (hazard ratio = 1.69 and 1.90, respectively). Further, within each phenotype, different imaging biomarkers of fracture were identified. These findings suggest that osteoporotic fracture risk is associated with bone phenotypes that capture key features of bone deterioration that are not distinguishable by aBMD. © 2021 American Society for Bone and Mineral Research (ASBMR).  相似文献   
30.

Background

Resistin is an immunometabolic mediator that is elevated in several inflammatory disorders. A ligand for Toll-like receptor 4, resistin modulates the recruitment and activation of myeloid cells, notably neutrophils. Neutrophils are major drivers of cystic fibrosis (CF) lung disease, in part due to the release of human neutrophil elastase- and myeloperoxidase-rich primary granules, leading to tissue damage. Here we assessed the relationship of resistin to CF lung disease.

Methods

Resistin levels were measured in plasma and sputum from three retrospective CF cohorts spanning a wide range of disease. We also assessed the ability of neutrophils to secrete resistin upon activation in vitro. Finally, we constructed a multivariate model assessing the relationship between resistin levels and lung function.

Results

Plasma resistin levels were only marginally higher in CF than in healthy control subjects. By contrast, sputum resistin levels were very high in CF, reaching 50–100 fold higher levels than in plasma. Among CF patients, higher plasma resistin levels were associated with allergic bronchopulmonary aspergillosis, and higher sputum resistin levels were associated with CF-related diabetes. Mechanistically, in vitro release of neutrophil primary granules was concomitant with resistin secretion. Overall, sputum resistin levels were negatively correlated with CF lung function, independently of other variables (age, sex, and genotype).

Conclusions

Our data establish relationships between resistin levels in the plasma and sputum of CF patients that correlate with disease status, and identify resistin as a novel mechanistic link between neutrophilic inflammation and lung disease in CF.  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