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   2874篇
  免费   183篇
  国内免费   13篇
耳鼻咽喉   32篇
儿科学   81篇
妇产科学   57篇
基础医学   405篇
口腔科学   29篇
临床医学   344篇
内科学   675篇
皮肤病学   71篇
神经病学   248篇
特种医学   64篇
外科学   323篇
综合类   38篇
一般理论   1篇
预防医学   210篇
眼科学   188篇
药学   155篇
中国医学   7篇
肿瘤学   142篇
  2023年   20篇
  2022年   47篇
  2021年   69篇
  2020年   54篇
  2019年   69篇
  2018年   78篇
  2017年   58篇
  2016年   56篇
  2015年   60篇
  2014年   90篇
  2013年   141篇
  2012年   199篇
  2011年   170篇
  2010年   116篇
  2009年   106篇
  2008年   198篇
  2007年   188篇
  2006年   180篇
  2005年   149篇
  2004年   144篇
  2003年   145篇
  2002年   135篇
  2001年   65篇
  2000年   46篇
  1999年   39篇
  1998年   28篇
  1997年   30篇
  1996年   25篇
  1995年   15篇
  1994年   21篇
  1993年   18篇
  1992年   21篇
  1991年   16篇
  1990年   9篇
  1989年   15篇
  1988年   15篇
  1987年   19篇
  1986年   14篇
  1985年   12篇
  1984年   16篇
  1983年   14篇
  1982年   16篇
  1979年   9篇
  1977年   8篇
  1975年   11篇
  1974年   8篇
  1972年   9篇
  1969年   10篇
  1968年   9篇
  1966年   12篇
排序方式: 共有3070条查询结果,搜索用时 31 毫秒
1.
BackgroundEpidemiological studies on peptic ulcer disease (PUD) have shown a recent decrease in hospital admissions in Western countries.ObjectiveThis paper aimed to study the current status and risk factors of PUD in a Nigerian metropolis.MethodsA cross-sectional study of symptomatic patients at upper gastrointestinal (GI) endoscopy diagnosed with PUD from February 2014 to September 2019 at a referral endoscopy facility in Port Harcourt, Niger delta region of Nigeria. The variables studied included demographics, symptoms and duration, blood group, chronic non-steroidal anti-inflammatory (NSAID) use, smoking, endoscopic and histology findings. Statistical analysis was performed using SPSS version 20.ResultsA total of 434 upper GI endoscopies were performed during the study period with thirty-one diagnosis of PUD made. The mean age of gastric ulcer (GU) and duodenal ulcer (DU) cases were 54.4 ± 20.2yrs and 48.1 ± 14.5yrs respectively (p = 0.367). GU to DU ratio was 1.4:1. H. pylori infection, chronic NSAID use and blood group O were seen in 7(22.5%), 8(25.8%) and 18(72.0%) respectively. Major indication in 21(67.7%) cases was gastrointestinal bleeding.ConclusionThere is a low diagnostic rate of PUD (6.7%) with pre-pyloric antral gastric ulcers as most common type and multifactorial aetiology.  相似文献   
2.
3.
Entering the postmodern world in which society is confronting crossroads, paradoxes, and complexity, the health care system is encountering a transformation more comprehensive and revolutionary than has ever been seen before. Analysis of the state of nursing vis a vis these transformations indicates that the current paradigm does not ensure the existence of the profession in the postmodern health care system. That is because of increased difficulties in consolidating the economic and quality issues into the core of nursing, and in understanding the complexity inherent in health related situations.  相似文献   
4.
5.
BACKGROUND: Fluorine 18 fluorodeoxyglucose (FDG) uptake may be increased in atherosclerotic plaques in asymptomatic patients. Repeat positron emission tomography (PET)/computed tomography (CT) studies were assessed for changes in patterns of FDG uptake and CT calcifications. METHODS AND RESULTS: Fifty consecutive cancer patients (mean age, 68 +/- 8 years) had repeat PET/CT studies 8 to 26 months apart. PET, CT, and PET/CT images were retrospectively evaluated for vascular wall abnormalities and for interval changes in the thoracic and abdominal aortas, as well as in carotid and iliac arteries, classified as PET+/CT+, PET+/CT-, and PET-/CT+. There were 485 abnormal sites in the first study and 495 in the second. CT calcifications were found in 46 patients (92%) in the first study and in 47 (94%) in the second. Vascular wall FDG uptake was found in both studies in 37 patients (74%). The pattern changed in 57 of 119 PET+ sites (48%) in the second study compared with 15 of 366 PET- sites (4%) (P < .0001). In the second study new PET+ sites were observed in 36 of 111 sites (32%) versus new PET-/CT+ sites in 19 of 384 sites (5%) (P < .0001). CONCLUSIONS: Changes in vascular FDG activity and CT calcifications can be assessed by repeat PET/CT. FDG-avid foci may represent a dynamic process, transient inflammation, whereas CT calcifications may indicate stable atherosclerosis. These preliminary results support the need for further research.  相似文献   
6.
7.
8.
9.
A study has been made of the role of specific antibody in causing increased retention and specific localization of a weak antigen, human serum albumin (HSA), in the popliteal and aortic lymph nodes of rats. The antigen was labelled with 125I prior to mixing with antibody. HSA mixed with excess homologous antibody was trapped to the greatest extent in these nodes after footpad injection of the antigen. Injection of HSA with antibody caused increased uptake of HSA into the medulla but retention was poor as autoradiographs showed the area to be essentially free of antigen 4–5 days after injection. By contrast, antigen injected with antibody localized strongly in lymphoid follicles and persisted at this site. Both IgM and IgG antibody were found to cause follicular localization of HSA in rats. Heterologous, isologous and homologous antibody also caused follicular localization of the antigen. Purified homologous γ-globulin was found to localize in the follicles. A moderate increase in the net negative charge of the γ-globulin by acetylation did not appreciably affect the ability of the globulin to localize in the follicles. Detectable formation of antibody did not occur in the rats after injection of antigen—antibody complexes, owing possibly to the inhibitory effect of free antibody on the primary response.  相似文献   
10.
A hospital cafeteria-associated outbreak of gastroenteritis due to Salmonella enterica serotype Infantis was retrospectively evaluated using modified repetitive element PCR (rep-PCR) fingerprinting with the ERIC2 and BOXA1R primers and computer-assisted gel analysis and dendrogram construction. Rep-PCR yielded objective between-cycler, same-strain similarity values of from 92% (composite fingerprints) to 96% (ERIC2 fingerprints). The 70 Salmonella isolates (which included 19 serotype Infantis isolates from the hospital outbreak, 10 other serotype Infantis isolates, and 41 isolates representing 14 other serotypes) were resolved well to the serotype level with each of the three fingerprint types (ERIC2, BOXA1R, and composite). Rep-PCR typing uncovered several historical serotyping errors and provided presumptive serotype assignments for other isolates with incomplete or undetermined serotypes. Analysis of replicate fingerprints for each isolate, as generated on two different thermal cyclers, indicated that most of the seeming subserotype discrimination noted in single-cycler dendrograms actually represented assay variability, since it was not reproducible in combined-cycler dendrograms. Rep-PCR typing, which would have been able to identify the presence of the hospital-associated serotype Infantis outbreak after the second outbreak isolate, could be used as a simple surrogate for serotyping by clinical microbiology laboratories that are equipped for diagnostic PCR.  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