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   1503169篇
  免费   101141篇
  国内免费   1927篇
耳鼻咽喉   20973篇
儿科学   49147篇
妇产科学   40186篇
基础医学   224606篇
口腔科学   41998篇
临床医学   132500篇
内科学   280307篇
皮肤病学   34721篇
神经病学   111501篇
特种医学   58143篇
外国民族医学   263篇
外科学   227265篇
综合类   29069篇
现状与发展   1篇
一般理论   370篇
预防医学   108443篇
眼科学   35214篇
药学   119908篇
  7篇
中国医学   3596篇
肿瘤学   88019篇
  2018年   15300篇
  2017年   11861篇
  2016年   13375篇
  2015年   14971篇
  2014年   20287篇
  2013年   30198篇
  2012年   41193篇
  2011年   44284篇
  2010年   25967篇
  2009年   24333篇
  2008年   41479篇
  2007年   44469篇
  2006年   45221篇
  2005年   43121篇
  2004年   41584篇
  2003年   39951篇
  2002年   38835篇
  2001年   78531篇
  2000年   80758篇
  1999年   66891篇
  1998年   16910篇
  1997年   14903篇
  1996年   15122篇
  1995年   14103篇
  1994年   12871篇
  1993年   12290篇
  1992年   50430篇
  1991年   49476篇
  1990年   49104篇
  1989年   47177篇
  1988年   42805篇
  1987年   41854篇
  1986年   39448篇
  1985年   37316篇
  1984年   27275篇
  1983年   23040篇
  1982年   12738篇
  1979年   25085篇
  1978年   17331篇
  1977年   15249篇
  1976年   13740篇
  1975年   15688篇
  1974年   18425篇
  1973年   17596篇
  1972年   16951篇
  1971年   16054篇
  1970年   14773篇
  1969年   14173篇
  1968年   12893篇
  1967年   11612篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
41.
42.
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   
43.
44.
45.

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   
46.
47.
48.
Pharmaceutical Chemistry Journal - Three extracts were produced from the above-ground part of the meadowsweet Filipendula ulmaria (L.) Maxim. using water, 40% ethanol, and 70% ethanol. Comparative...  相似文献   
49.
50.
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   
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