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   2500249篇
  免费   175999篇
  国内免费   6534篇
耳鼻咽喉   33754篇
儿科学   81021篇
妇产科学   68781篇
基础医学   355400篇
口腔科学   71878篇
临床医学   227023篇
内科学   479083篇
皮肤病学   56675篇
神经病学   192710篇
特种医学   95538篇
外国民族医学   443篇
外科学   376018篇
综合类   57805篇
现状与发展   12篇
一般理论   768篇
预防医学   182858篇
眼科学   59028篇
药学   189433篇
  34篇
中国医学   7785篇
肿瘤学   146735篇
  2021年   20289篇
  2019年   20412篇
  2018年   29261篇
  2017年   22480篇
  2016年   24906篇
  2015年   28690篇
  2014年   39296篇
  2013年   56813篇
  2012年   78393篇
  2011年   82331篇
  2010年   48999篇
  2009年   45625篇
  2008年   75518篇
  2007年   80335篇
  2006年   80847篇
  2005年   77159篇
  2004年   74063篇
  2003年   70757篇
  2002年   67895篇
  2001年   128864篇
  2000年   131640篇
  1999年   109215篇
  1998年   28818篇
  1997年   25186篇
  1996年   25241篇
  1995年   24100篇
  1994年   22002篇
  1993年   20489篇
  1992年   82276篇
  1991年   79323篇
  1990年   77102篇
  1989年   73980篇
  1988年   67244篇
  1987年   65542篇
  1986年   61932篇
  1985年   58665篇
  1984年   42980篇
  1983年   36565篇
  1982年   20544篇
  1979年   38274篇
  1978年   26326篇
  1977年   22896篇
  1976年   20779篇
  1975年   22584篇
  1974年   26966篇
  1973年   25985篇
  1972年   24267篇
  1971年   22654篇
  1970年   20940篇
  1969年   19794篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
85.
BACKGROUND: The aim of this study was to estimate the cost effectiveness of screening for abdominal aortic aneurysm (AAA). MATERIAL AND METHODS: All 12,639 men born in the years 1921-1933 (aged 64-73) living in Viborg County, Denmark, were randomly allocated either to receive an invitation to abdominal ultrasound scanning for AAA or to be controls. Costs for screening and surveillance were assessed prospectively. Diagnosis Related Group (DRG) costs from 1999 were used concerning admissions with uncomplicated and complicated operations. Admissions for AAA surgery were retrospectively classified according to complications in patient records. RESULTS: Mean follow-up time was 52 months. 76.6% of invited men attended screening, and 191 (4.0%) had an AAA. As previously reported, the cumulative 5-year AAA-specific mortality in the invited group was significantly reduced by 67% compared to the control group (P = 0.003). The costs were estimated to be Euro 11.23 per scan. The costs per life-year saved were Euro 9057 (Euro 5872-20,063) after 5 years, and were expected to decrease to Euro 2708 (Euro 1758-6031) after 10 years and to Euro 1825 (Euro 1185-4063) after 15 years. CONCLUSION: Screening of 64-73 years old males in Denmark seems cost effective.  相似文献   
86.
We have recently shown that HPV-positive tonsillar carcinoma in young patients exhibits nonkeratinizing basaloid morphology and a characteristic immunophenotype. The purpose of this study was to review a large number of cases of oropharyngeal carcinomas, in all age groups, and to identify tumors with nonkeratinizing morphology. Using polymerase chain reaction (PCR) the prevalence and type of HPV DNA was determined in representative cases and in a control group of conventional keratinizing squamous cell carcinomas. The tumors were further characterized with a panel of immunohistochemical stains. A total of 235 carcinomas were reviewed; 141 of the tonsils and 94 in the base of tongue. Ninety (36%) of the tonsillar and 30 (32%) of the base of tongue carcinomas were nonkeratinizing (NKCa) with basal cell features; the rest were classical keratinizing squamous cell carcinomas (KSCC). HPV DNA, particularly type 16, was identified in 10 (100%) of 10 of NKCA and in only 2 (20%) of 10 of KSCC (P = .0014). NKCas were strongly reactive to p16 antibodies while KSCC showed weak and focal reactivity. Higher Ki67 and lower p53 staining scores were observed in NKCa as compared to KSCC. It is concluded that NKCa of the tonsils and base of tongue is a distinct subtype of squamous cell carcinoma of the head and neck with high prevalence of HPV DNA and a characteristic immunophenotype.  相似文献   
87.
88.
Background: Few studies have examined the use of ultrasound for sciatic nerve localization. The authors evaluated the usefulness of low-frequency ultrasound in identifying the sciatic nerve at three locations in the lower extremity and in guiding needle advancement to target before nerve stimulation.

Methods: In this prospective observational study, 15 volunteers underwent sciatic nerve examination using a curved ultrasound probe in the range of 2-5 MHz and a Philips-ATL 5000 unit (ATL Ultrasound, Bothell, WA) in the gluteal, infragluteal, and proximal thigh regions. Thereafter, an insulated block needle was advanced inline with the ultrasound beam to reach the nerve target, which was further confirmed by electrical stimulation. The quality of sciatic nerve images, ease of needle to nerve contact, threshold stimulating current, and resultant motor response were recorded.

Results: The sciatic nerve was successfully identified in the transverse view as a solitary predominantly hyperechoic structure on ultrasound in all of the three regions examined. The target nerve was visualized easily in 87% and localized within two needle attempts in all patients. Nerve stimulation was successful in 100% after two attempts with a threshold current of 0.42 +/- 0.12 (mean +/- SD) eliciting foot plantarflexion or dorsiflexion.  相似文献   

89.
Infections due to Penicillium species other than P.marneffei are rare. We identified a boy with X-linked chronic granulomatous disease (X-CGD) with a pulmonary nodule and adjacent rib osteomyelitis caused by Penicillium piceum. The only sign of infection was an elevated sedimentation rate. P. piceum was isolated by fine needle aspirate and from excised infected tissues. Surgical removal and one year of voriconazole treatment were very well tolerated and led to complete recovery. Microbiological, microscopic and molecular studies support the fungal diagnosis. P. piceum should be considered as a relevant pathogen in immunocompromised patients.  相似文献   
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