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   1090836篇
  免费   74381篇
  国内免费   1431篇
耳鼻咽喉   15150篇
儿科学   34993篇
妇产科学   28912篇
基础医学   155709篇
口腔科学   29876篇
临床医学   96651篇
内科学   207258篇
皮肤病学   24582篇
神经病学   83247篇
特种医学   43591篇
外国民族医学   201篇
外科学   165607篇
综合类   22005篇
现状与发展   1篇
一般理论   281篇
预防医学   76290篇
眼科学   24932篇
药学   87356篇
  8篇
中国医学   2847篇
肿瘤学   67151篇
  2019年   8049篇
  2018年   11588篇
  2017年   9146篇
  2016年   10346篇
  2015年   11605篇
  2014年   15716篇
  2013年   22932篇
  2012年   31603篇
  2011年   33351篇
  2010年   19566篇
  2009年   18399篇
  2008年   30930篇
  2007年   33216篇
  2006年   33865篇
  2005年   32226篇
  2004年   30799篇
  2003年   29599篇
  2002年   28567篇
  2001年   60229篇
  2000年   61659篇
  1999年   51155篇
  1998年   12654篇
  1997年   11214篇
  1996年   11176篇
  1995年   10477篇
  1994年   9498篇
  1993年   9016篇
  1992年   37917篇
  1991年   36385篇
  1990年   35861篇
  1989年   34412篇
  1988年   31011篇
  1987年   30095篇
  1986年   28347篇
  1985年   26569篇
  1984年   19328篇
  1983年   16267篇
  1982年   8965篇
  1979年   17108篇
  1978年   11481篇
  1977年   10316篇
  1976年   8897篇
  1975年   10124篇
  1974年   11721篇
  1973年   11322篇
  1972年   10787篇
  1971年   10125篇
  1970年   9280篇
  1969年   8958篇
  1968年   7937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