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   1253篇
  免费   54篇
  国内免费   5篇
耳鼻咽喉   55篇
儿科学   49篇
妇产科学   19篇
基础医学   89篇
口腔科学   75篇
临床医学   76篇
内科学   238篇
皮肤病学   7篇
神经病学   144篇
特种医学   153篇
外科学   221篇
综合类   23篇
一般理论   2篇
预防医学   41篇
眼科学   19篇
药学   58篇
中国医学   3篇
肿瘤学   40篇
  2023年   11篇
  2022年   27篇
  2021年   32篇
  2020年   14篇
  2019年   21篇
  2018年   43篇
  2017年   33篇
  2016年   34篇
  2015年   34篇
  2014年   44篇
  2013年   50篇
  2012年   74篇
  2011年   68篇
  2010年   51篇
  2009年   36篇
  2008年   62篇
  2007年   75篇
  2006年   87篇
  2005年   74篇
  2004年   59篇
  2003年   71篇
  2002年   41篇
  2001年   30篇
  2000年   32篇
  1999年   34篇
  1998年   6篇
  1997年   6篇
  1996年   6篇
  1995年   8篇
  1994年   5篇
  1992年   13篇
  1991年   7篇
  1990年   4篇
  1989年   9篇
  1988年   8篇
  1987年   5篇
  1985年   4篇
  1984年   5篇
  1983年   5篇
  1980年   8篇
  1979年   8篇
  1978年   4篇
  1976年   4篇
  1974年   5篇
  1973年   5篇
  1972年   5篇
  1971年   11篇
  1970年   5篇
  1969年   3篇
  1967年   3篇
排序方式: 共有1312条查询结果,搜索用时 15 毫秒
1.
2.
Conclusions: This study revealed a significant correlation between red-green-blue (RGB) values of tympanic membrane (TM) images and the presence of effusion in the middle ear. These results confirm that endoscopic RGB evaluation is a rapid and non-invasive procedure yielding objective results. Objective: To investigate, in cases of otitis media with effusion (OME), the correlation of the TM color changes with the presence and viscosity of the effusion in the middle ear. Methods: Endoscopic images of the TMs of 52 patients (group 1) and 52 healthy controls (group 2) were taken during their otologic examinations. RGB values of particular points were measured on the TM images of both groups. Additionally, in group 1 the viscosity of each effusion taken by paracentesis during surgery was also measured intraoperatively with a viscometer. Patients with viscosity values lower and higher than 450 cP (centipoise) were subdivided into groups 1a and 1b, respectively. Results: Study and control groups were comparable regarding the number of patients and their mean ages (p > 0.05). Statistically significant differences were found in RGB values of the TM between groups 1 and 2, but not between groups 1a and 1b.  相似文献   
3.
Autistic disorder and 22q11.2 duplication.   总被引:2,自引:0,他引:2  
Although several reports have described the co-occurrence of autism in subjects with chromosome 22 abnormalities including trisomy 22, translocation 20/22, 22q11.2 deletion, ring chromosome 22, and 22q13.3 deletion, there is no report with 22q11.2 duplication. We report a 9-year-old girl, referred to our department for her behavioural problems and language delay. She was diagnosed with autistic disorder according to DSM-IV criteria. Because of her dysmorphic characteristics comprising narrow face, narrow forehead, mandibular prognathism, synophrys, and operated cleft palate and cardiac problems, she had gone under cytogenetic analysis. Although she was ascertained as suspected velocardiofacial syndrome (VCFS), the duplication of 22q11.2 was detected by interphase fluorescence in situ hybridization. Previous reports on the psychiatric aspects of 22q11.2 duplication have shown the existence of hyperactivity, learning disability, speech problems, and aggressive behaviours but not autism. Moreover, the lack of reports of co-occurrence of autism and 22q11.2 duplication may be related to paucity as a result of technical problems.  相似文献   
4.
Severe middle vault deformity with disturbed nasal form and function is one of the most challenging procedures to correct in a secondary rhinoplasty. Reconstructing the deformity with autologous septal cartilage would be the primary choice of most surgeons, if it were always available. However in certain cases the lack of a sufficient quantity of autologous cartilage has forced surgeons to explore other viable options. This paper discusses our experience with the combined use of spreader and dorsal onlay grafts from various materials in the reconstruction of severe middle vault deformity in 110 patients. In follow up, (between 6 and 42 months; mean 21 months) all patients were noted to have improved in both aesthetics and function with no major complications noted. In summary, this study proposes that any engrafting material can be used safely when the proper surgical principals and technique are employed.  相似文献   
5.
2-[18F]Fluoro-3-(2(S)-azetidinylmethoxy)pyridine (2-[18F]F-A-85380) was among the first subtype selective radioligands to visualise the in vivo distribution of alpha4beta2-containing neuronal nicotinic acetylcholine receptors (nAChRs) in human brain. We developed a one-pot synthesis for the preparation of 2-[18F]F-A-85380 in a commercially available TRACERlab FXF-N synthesis module. The synthesis comprises a nucleophilic substitution followed by hydrolysis of a t-butyloxycarbonyl (BOC)-protected intermediate. After formulation for intravenous application up to 20 G Bq 2-[18F]F-A-85380 were produced from a starting activity of 100 G Bq [18F]fluoride in 60 min with a specific activity of about 4.10(5)GBq/mmol and a mean radiochemical purity of more than 99%.  相似文献   
6.
This article describes the treatment of an adolescent girl who was congenitally missing all 4 second premolars and had a retained mandibular second primary molar. Various treatment alternatives are discussed, and the final treatment plan of space opening for 3 implants and space closure of the maxillary left second premolar site is presented.  相似文献   
7.
Cholinergic deficits in Alzheimer's disease are accompanied by a number of alterations in other transmitter systems including glutamate, noradrenaline and serotonin, suggesting the involvement also of other neurotransmitter systems in the pathogenesis of the disease. To address the question whether beta-amyloid may contribute to these deficits, brain tissue from transgenic Tg2576 mice with Alzheimer plaque pathology at ages of 5 (still no significant plaque load) and 17 months (moderate to high cortical beta-amyloid plaque load) were examined for a number of cholinergic and non-cholinergic markers. Transgenic mice with no significant plaque load demonstrated reduced hemicholinium-3 (HCh-3) binding to choline uptake sites in anterior brain regions as compared to non-transgenic littermates, while in aged transgenic mice with high number of plaque deposits decreased HCh-3 binding levels were accompanied by increased vesicular acetylcholine transporter binding in selected cortical brain regions. In aged transgenic mice GABA(A), NMDA, AMPA, kainate, and beta-adrenergic as well 5-HT(1A)- and 5-HT(2A)-receptor binding levels were hardly affected, whereas alpha(1)- and alpha(2)-adrenoceptor binding was increased in selected cerebral cortical regions as compared to non-transgenic littermates. The development of changes in both cholinergic and non-cholinergic markers in transgenic Tg2576 mouse brain already before the onset of progressive plaque deposition provides in vivo evidence of a modulatory role of soluble beta-amyloid on cortical neurotransmission and may be referred to the deficits in learning and memory observed in these mice also before significant plaque load.  相似文献   
8.
9.
10.
The present study investigated whether an explanation for the conflicting reports on the interleukin-2 (IL-2) status of amniotic fluid is due to the presence of IL-15 which shares biological activities with IL-2 and utilizes the IL-2 receptor beta-chain. Amniotic fluids from 45 normally progressing pregnancies between 14 and 16 weeks after the last menstrual period were assayed for IL-2 and IL-15 by bioassay and enzyme-linked immunosorbent assay (ELISA). The ability of amniotic fluids to induce cytotoxic T lymphoblastoid line-2 (CTLL-2) cell proliferation was demonstrated to be dependent upon bioassay culture conditions. In serum-free medium each amniotic fluid stimulated CTLL-2 proliferation with a mean level of IL-2-like bioactivity of 14.7 +/- 2.3 ng/ml but amniotic fluids failed to induce CTLL-2 proliferation in serum-supplemented medium. Treatment with neutralizing anti-IL-2 or anti-IL-15 antibodies failed to inhibit amniotic fluid-induced CTLL cell proliferation in serum-free medium, indicating a lack of IL-2 and IL-15 bioactivity. In contrast, treatment with anti-IL-2 receptor beta-chain antibody significantly reduced amniotic fluid-induced proliferation. The lack of IL-2 and IL-15 activity in amniotic fluids was confirmed using ELISA. Although high levels of IL-15 immunoactivity were detected in all samples, specificity controls showed a lack of specific IL-15 immunoactivity in amniotic fluid. Pretreatment of amniotic fluids with 100-500 ng/ml mouse immunoglobulin G abrogated IL-15 immunoactivity, indicating that amniotic fluid contains molecules binding to Fc regions of immunoglobulins and responsible for false ELISA positivity. These studies unequivocally show that amniotic fluid lacks IL-2 and IL-15 but can stimulate CTLL-2 cell proliferation via the IL-2 receptor beta-chain. The absence of IL-2 and IL-15 in normal mid-trimester amniotic fluid suggests that the cytokine profile of human pregnancy appears to be associated with a bias against type 1 cytokines within the feto-placental unit.  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