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   43550篇
  免费   3549篇
  国内免费   165篇
耳鼻咽喉   506篇
儿科学   1155篇
妇产科学   744篇
基础医学   5556篇
口腔科学   988篇
临床医学   4763篇
内科学   8556篇
皮肤病学   486篇
神经病学   4523篇
特种医学   1810篇
外国民族医学   1篇
外科学   6571篇
综合类   780篇
现状与发展   1篇
一般理论   31篇
预防医学   4150篇
眼科学   1245篇
药学   2971篇
中国医学   92篇
肿瘤学   2335篇
  2021年   535篇
  2020年   372篇
  2019年   547篇
  2018年   653篇
  2017年   499篇
  2016年   559篇
  2015年   702篇
  2014年   1132篇
  2013年   1756篇
  2012年   2405篇
  2011年   2802篇
  2010年   1480篇
  2009年   1427篇
  2008年   2429篇
  2007年   2787篇
  2006年   2666篇
  2005年   2791篇
  2004年   2554篇
  2003年   2509篇
  2002年   2561篇
  2001年   548篇
  2000年   504篇
  1999年   616篇
  1998年   609篇
  1997年   498篇
  1996年   479篇
  1995年   431篇
  1994年   409篇
  1993年   401篇
  1992年   403篇
  1991年   356篇
  1990年   348篇
  1989年   360篇
  1988年   354篇
  1987年   357篇
  1986年   328篇
  1985年   392篇
  1984年   439篇
  1983年   410篇
  1982年   537篇
  1981年   510篇
  1980年   494篇
  1979年   325篇
  1978年   312篇
  1977年   327篇
  1976年   251篇
  1975年   229篇
  1974年   262篇
  1973年   235篇
  1972年   226篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
BACKGROUND: Recently, epidemiological and clinical data have revealed important changes with regard to clinical adenovirus infection, including alterations in antigenic presentation, geographical distribution, and virulence of the virus. METHODS: In an effort to better understand the epidemiology of clinical adenovirus infection in the United States, we adopted a new molecular adenovirus typing technique to study clinical adenovirus isolates collected from 22 medical facilities over a 25-month period during 2004-2006. A hexon gene sequence typing method was used to characterize 2237 clinical adenovirus-positive specimens, comparing their sequences with those of the 51 currently recognized prototype human adenovirus strains. In a blinded comparison, this method performed well and was much faster than the classic serologic typing method. RESULTS: Among civilians, the most prevalent adenovirus types were types 3 (prevalence, 34.6%), 2 (24.3%), 1 (17.7%), and 5 (5.3%). Among military trainees, the most prevalent types were types 4 (prevalence, 92.8%), 3 (2.6%), and 21 (2.4%). CONCLUSIONS: For both populations, we observed a statistically significant increasing trend of adenovirus type 21 detection over time. Among adenovirus isolates recovered from specimens from civilians, 50% were associated with hospitalization, 19.6% with a chronic disease condition, 11% with a bone marrow or solid organ transplantation, 7.4% with intensive care unit stay, and 4.2% with a cancer diagnosis. Multivariable risk factor modeling for adenovirus disease severity found that age <7 years (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.4-7.4), chronic disease (OR, 3.6; 95% CI, 2.6-5.1), recent transplantation (OR, 2.7; 95% CI, 1.3-5.2), and adenovirus type 5 (OR, 2.7; 95% CI, 1.5-4.7) or type 21 infection (OR, 7.6; 95% CI, 2.6-22.3) increased the risk of severe disease.  相似文献   
83.
Cell transplantation to improve ventricular function in the failing heart   总被引:9,自引:0,他引:9  
Current therapies for congestive heart failure are limited in efficacy or in applicability. Cardiac cell transplantation offers a novel therapeutic approach to improve heart function. Although significant progress has been made over the past decade in the development of cell transplantation, only recently have investigators studied the changes in ventricular function following cell transplantation. This review article describes the latest research developments, evaluates recent studies of ventricular function after cell transplantation, and discusses the future directions of cell transplantation as a new therapy to ‘repair broken hearts’.  相似文献   
84.
85.
Implant surface morphology regulates osteoblast phenotypic expression. Osteoblast sensitivity to non-biologic surfaces suggests that native bone surface features may also affect osteoblast response. To test this, MG63 osteoblast-like cells were grown for 7 days on bovine cortical bone wafers pretreated with rat bone marrow osteoclasts for 0, 10 or 20 days. Response to osteoclast-treated surfaces was compared to the response of MG63 cells to titanium surfaces with smooth and rough microtopographies. Cell number, differentiation (alkaline phosphatase activity and osteocalcin levels), and local factors (PGE(2) and TGF-beta1) were measured in confluent cultures. Compared to culture on plastic, cell number was reduced on all three types of bone wafers; this effect was dose-dependent with increasing resorption of the surface. Alkaline phosphatase specific activity was increased (P相似文献   
86.
87.
88.
A 7-cm anterior mediastinal tumor in an 80-year-old woman was found by light and electron microscopy to be a neuroblastoma. Immunoreactivity for neuron-specific enolase, synaptophysin, and chromogranin supported the diagnosis. Neuroblastoma is an uncommon tumor in adults and we are not aware of a previous report of such a tumor in a patient of this age.  相似文献   
89.
90.
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