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   2090篇
  免费   85篇
  国内免费   4篇
耳鼻咽喉   10篇
儿科学   42篇
妇产科学   80篇
基础医学   294篇
口腔科学   89篇
临床医学   193篇
内科学   409篇
皮肤病学   46篇
神经病学   132篇
特种医学   129篇
外科学   217篇
综合类   20篇
一般理论   1篇
预防医学   112篇
眼科学   42篇
药学   125篇
中国医学   2篇
肿瘤学   236篇
  2023年   8篇
  2022年   7篇
  2021年   23篇
  2020年   15篇
  2019年   32篇
  2018年   32篇
  2017年   27篇
  2016年   40篇
  2015年   35篇
  2014年   66篇
  2013年   109篇
  2012年   107篇
  2011年   137篇
  2010年   80篇
  2009年   74篇
  2008年   139篇
  2007年   122篇
  2006年   128篇
  2005年   151篇
  2004年   145篇
  2003年   118篇
  2002年   116篇
  2001年   33篇
  2000年   19篇
  1999年   38篇
  1998年   24篇
  1997年   32篇
  1996年   20篇
  1995年   14篇
  1994年   12篇
  1993年   18篇
  1992年   18篇
  1991年   15篇
  1990年   20篇
  1989年   13篇
  1988年   4篇
  1987年   11篇
  1986年   15篇
  1985年   17篇
  1984年   18篇
  1983年   13篇
  1982年   9篇
  1981年   6篇
  1979年   5篇
  1978年   11篇
  1977年   7篇
  1976年   6篇
  1975年   9篇
  1974年   6篇
  1973年   6篇
排序方式: 共有2179条查询结果,搜索用时 109 毫秒
981.
982.
Objective:To test the null hypothesis of no significant difference in terms of intraoral pressure curve characteristics assessed simultaneously at the subpalatal space (SPS) and the vestibular space (VS), during different oral postures, between four groups with either an Angle Class II/1 (II1), Angle Class II/2 (II2), anterior open bite (O) malocclusion, or a neutral occlusion control group (I).Materials and Methods:Intraoral pressure recordings were performed simultaneously in the VS and SPS of 69 consecutive subjects (nII1  =  15; nII2  =  17; nO  =  17; nI  =  20; mean age/standard deviation 18.43/6.60 years). Assessments included defined sections of open mouth posture (OMP, 30 seconds), anteriorly closed mouth condition (60 seconds), dynamics by a tongue-repositioning maneuver (TRM, 60 seconds), swallowing, and positive pressure generation (PP, 10 seconds). Interactions of malocclusion, compartment location, and posture on pressure curve characteristics were analyzed by Kruskal-Wallis and Mann-Whitney U-tests, adopting an α level of 5%.Results:Globally significant group differences were detected at the VS (plateau duration and median peak heights during TRM; area under pressure curve [AUC] during PP) and SPS (AUC during TRM and PP). Subjects with anteriorly nonopen dental configurations (groups I and II2) were able to keep negative pressure levels at the VS for longer time periods during TRM, compared to groups O and II1.Conclusions:The null hypothesis was rejected for mean VS plateau durations and peak heights and for SPS AUC. Negative pressures at the VS may stabilize outer soft tissues passively and may explain the dental arch form shaping effect by mimic muscles.  相似文献   
983.
984.
985.
BACKGROUND AND PURPOSE: Focused dose escalation may improve local control in head and neck cancer. Planning results of [(18)F]fluoro-deoxy-glucose positron emission tomography ([(18)F]FDG-PET) voxel intensity-based intensity-modulated radiation therapy (IMRT) were compared with those of PET contour-based IMRT. PATIENTS AND METHODS: PET contour-based IMRT aims to deliver a homogeneous boost dose to a PET-based subvolume of the planning target volume (PTV), called PTV(PET). The present PET voxel intensity-based planning study aims to prescribe the boost dose directly as a function of PET voxel intensity values, while leaving the dose distribution outside the PTV unchanged. Two escalation steps (2.5 and 3 Gy/fraction) were performed for 15 patients. RESULTS: PTV(PET) was irradiated with a homogeneous dose in the contour-based approach. In the voxel intensity-based approach, one or more sharp dose peaks were created inside the PTV, following the distribution of PET voxel intensity values. CONCLUSIONS: While PET voxel intensity-based IMRT had a large effect on the dose distribution within the PTV, only small effects were observed on the dose distribution outside this PTV and on the dose delivered to the organs at risk. Therefore both methods are alternatives for boosting subvolumes inside a selected PTV.  相似文献   
986.
987.
Cyclooxygenase-2 (COX-2) is involved in carcinogenesis, immune response suppression, apoptosis inhibition, angiogenesis, and tumor cell invasion and metastasis. The gene for COX-2, designated as PTGS2, carries a common polymorphism at position 8473 in the 3'-untranslated region (PTGS2 8473T>C), which has been associated with susceptibility to malignant disease. To investigate the role of this polymorphism for breast cancer, we determined the prevalence of PTGS2 genotypes in 500 women with breast cancer and 500 sex- and age-matched healthy control subjects. Homozygous carriers of the 8473-CC genotype were more frequent among patients (12.4%) than among controls (6.6%; P = 0.002). The odds ratio for carriers of this genotype for breast cancer was 2.1 (95% confidence interval, 1.3-3.3). Among patients, estrogen receptor positivity was less frequent among carriers of a CC genotype (63.9%) than among carriers of a TT or TC genotype (76.9%; P = 0.028). Tumor size, histologic grade, presence of primary lymph node metastases, progesterone receptor positivity, or age at diagnosis were not associated with PTGS2 genotypes. We conclude that the homozygous PTGS2 8473-CC genotype may be associated with breast cancer risk.  相似文献   
988.
989.
990.
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