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   1212391篇
  免费   78848篇
  国内免费   1659篇
耳鼻咽喉   17343篇
儿科学   39692篇
妇产科学   31952篇
基础医学   173188篇
口腔科学   33631篇
临床医学   105376篇
内科学   228454篇
皮肤病学   28477篇
神经病学   94556篇
特种医学   49812篇
外国民族医学   224篇
外科学   186042篇
综合类   22676篇
现状与发展   1篇
一般理论   301篇
预防医学   81345篇
眼科学   28168篇
药学   96111篇
  7篇
中国医学   3091篇
肿瘤学   72451篇
  2021年   8576篇
  2019年   8842篇
  2018年   13734篇
  2017年   10927篇
  2016年   12877篇
  2015年   14341篇
  2014年   18438篇
  2013年   26769篇
  2012年   37685篇
  2011年   39082篇
  2010年   22922篇
  2009年   20963篇
  2008年   36579篇
  2007年   39527篇
  2006年   40114篇
  2005年   38812篇
  2004年   37193篇
  2003年   35793篇
  2002年   34636篇
  2001年   64630篇
  2000年   65967篇
  1999年   54906篇
  1998年   13652篇
  1997年   12000篇
  1996年   11760篇
  1995年   10949篇
  1994年   9914篇
  1993年   9378篇
  1992年   39572篇
  1991年   37948篇
  1990年   37402篇
  1989年   35839篇
  1988年   32231篇
  1987年   31368篇
  1986年   29469篇
  1985年   27638篇
  1984年   20120篇
  1983年   16888篇
  1982年   9363篇
  1979年   18044篇
  1978年   12171篇
  1977年   10844篇
  1976年   9416篇
  1975年   10832篇
  1974年   12458篇
  1973年   12037篇
  1972年   11534篇
  1971年   10834篇
  1970年   9924篇
  1969年   9584篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
31.
32.
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   
33.
34.
35.
36.
37.
38.
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   
39.

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   
40.
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