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   2230836篇
  免费   153074篇
  国内免费   4042篇
耳鼻咽喉   32863篇
儿科学   70916篇
妇产科学   62293篇
基础医学   315567篇
口腔科学   66058篇
临床医学   195216篇
内科学   424900篇
皮肤病学   51232篇
神经病学   177071篇
特种医学   87699篇
外国民族医学   595篇
外科学   339373篇
综合类   48961篇
现状与发展   7篇
一般理论   712篇
预防医学   158336篇
眼科学   53340篇
药学   171591篇
  10篇
中国医学   5171篇
肿瘤学   126041篇
  2018年   22766篇
  2017年   18253篇
  2016年   20711篇
  2015年   22554篇
  2014年   30797篇
  2013年   46806篇
  2012年   62344篇
  2011年   66434篇
  2010年   39033篇
  2009年   36301篇
  2008年   62876篇
  2007年   67963篇
  2006年   68463篇
  2005年   65857篇
  2004年   63530篇
  2003年   61372篇
  2002年   59897篇
  2001年   106751篇
  2000年   110132篇
  1999年   91968篇
  1998年   24780篇
  1997年   22231篇
  1996年   21623篇
  1995年   20274篇
  1994年   18822篇
  1993年   17720篇
  1992年   69858篇
  1991年   67444篇
  1990年   66281篇
  1989年   64334篇
  1988年   59309篇
  1987年   58169篇
  1986年   55419篇
  1985年   52695篇
  1984年   39259篇
  1983年   33338篇
  1982年   19629篇
  1979年   36930篇
  1978年   26010篇
  1977年   22844篇
  1976年   20526篇
  1975年   23254篇
  1974年   27433篇
  1973年   26725篇
  1972年   25393篇
  1971年   23804篇
  1970年   22325篇
  1969年   21462篇
  1968年   19815篇
  1967年   17775篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
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   
42.
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   
43.
44.
45.
46.
47.
BackgroundSecond-hand smoking or environmental tobacco smoke is a critical health risk. Children are the most vulnerable to second-hand smoking because of their small bronchial ducts, less developed immunity, and low-physical activity.ObjectivesThe purpose of this study was to ascertain the effects of second-hand smoking on lung functions in athlete and non-athlete school-aged children.MethodsThis observational study included forty-six school-aged children, their age was 8–15 years, assigned to three groups; 2 study groups and 1 control group (n=15). The study groups comprised of 16 football players, and of 15 cyclists. Lung functions were evaluated recording forced vital capacity, forced expiratory volume in 1 sec and peak expiratory flow using digital spirometer.ResultsAll measures were recorded in definite values and the children were also classified into second-hand smoking (SH), or non-exposed to tobacco smoking (NE). The findings presented a significant increase (p<0.05) of the study groups in forced vital capacity, forced expiratory volume in 1 sec and peak expiratory flow solely for the non-exposed children. However, there were non-significant differences between the cyclists and football players or between the passive smoking children and non-exposed children in any of the two study groups (p>0.05).ConclusionThe outcomes of this study suggest beneficial influences of the sports activity on the lung functions, without different influences of the cyclists and football players on the lung functions.  相似文献   
48.
49.
As millions of people turn to social media for health information, better understanding the factors that guide health-related judgments and perceptions in this context is imperative. We report on two Web experiments (n > 400 total) examining the power of society’s widespread weight bias and related stereotypes to influence nutrition judgments in social media spaces. In Experiment 1, meals were judged as lower in nutritional quality when the person who recommended them (the source) was depicted as obese rather than of normal weight, an effect mediated by stereotypic beliefs about the source as a generally unhealthy person. Experiment 2 replicated this effect, which—notably—remained significant when controlling for objective nutritional information (calories and fat content). Results highlight spillover effects of weight bias that extend beyond person perception to color impressions of objects (here, food) that are associated with stigmatized attributes. Implications for everyday nutrition judgments and public health are considered.  相似文献   
50.
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