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   2228644篇
  免费   155526篇
  国内免费   4046篇
耳鼻咽喉   32864篇
儿科学   70923篇
妇产科学   62300篇
基础医学   315617篇
口腔科学   66060篇
临床医学   195233篇
内科学   424942篇
皮肤病学   51260篇
神经病学   177092篇
特种医学   87703篇
外国民族医学   595篇
外科学   339419篇
综合类   48962篇
现状与发展   7篇
一般理论   712篇
预防医学   158349篇
眼科学   53342篇
药学   171604篇
  10篇
中国医学   5171篇
肿瘤学   126051篇
  2018年   22771篇
  2017年   18256篇
  2016年   20713篇
  2015年   22557篇
  2014年   30804篇
  2013年   46813篇
  2012年   62349篇
  2011年   66446篇
  2010年   39042篇
  2009年   36311篇
  2008年   62875篇
  2007年   67969篇
  2006年   68473篇
  2005年   65861篇
  2004年   63531篇
  2003年   61376篇
  2002年   59900篇
  2001年   106755篇
  2000年   110138篇
  1999年   91977篇
  1998年   24788篇
  1997年   22234篇
  1996年   21629篇
  1995年   20277篇
  1994年   18823篇
  1993年   17721篇
  1992年   69864篇
  1991年   67448篇
  1990年   66289篇
  1989年   64337篇
  1988年   59314篇
  1987年   58181篇
  1986年   55424篇
  1985年   52701篇
  1984年   39268篇
  1983年   33341篇
  1982年   19635篇
  1979年   36935篇
  1978年   26015篇
  1977年   22846篇
  1976年   20528篇
  1975年   23257篇
  1974年   27439篇
  1973年   26727篇
  1972年   25398篇
  1971年   23806篇
  1970年   22328篇
  1969年   21463篇
  1968年   19817篇
  1967年   17777篇
排序方式: 共有10000条查询结果,搜索用时 671 毫秒
61.
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   
62.
Lasers in Medical Science - Studies reported the harmful effects of 2,4-D on body tissues, provoking changes in the anatomy and physiology of the kidneys, liver, and testicles. Thus, the objective...  相似文献   
63.
64.
65.
66.

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   
67.
68.
69.
Behçet disease is a complex, multisystem disease characterized by recurrent oral and genital ulcerations. It rarely occurs in infants or children. Neonatal Behçet disease has been reported in infants whose ulcers resolve at or before 9 weeks of age. Few cases of neonatal Behçet disease persisting into childhood have previously been reported. We report the case of a 1‐month‐old infant who presented with severe recurrent genital ulcerations and at 6 months developed recurrent oral ulcerations. Her orogenital ulcerations continue to recur. Human leukocyte antigen testing revealed HLA‐B51 and B44 positivity. This is a case of pediatric Behçet disease in the neonatal period. Behçet disease should be considered in the differential diagnosis of recurrent genital and oral ulcerations in infants and children.  相似文献   
70.
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