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   1336000篇
  免费   94296篇
  国内免费   2910篇
耳鼻咽喉   19713篇
儿科学   40240篇
妇产科学   38664篇
基础医学   187206篇
口腔科学   39818篇
临床医学   112620篇
内科学   262465篇
皮肤病学   30205篇
神经病学   106374篇
特种医学   53667篇
外国民族医学   435篇
外科学   208225篇
综合类   31047篇
现状与发展   6篇
一般理论   436篇
预防医学   92036篇
眼科学   31357篇
药学   100058篇
  4篇
中国医学   2987篇
肿瘤学   75643篇
  2018年   11739篇
  2015年   11874篇
  2014年   16694篇
  2013年   25253篇
  2012年   33003篇
  2011年   34865篇
  2010年   20727篇
  2009年   20226篇
  2008年   33576篇
  2007年   36682篇
  2006年   37258篇
  2005年   36017篇
  2004年   35087篇
  2003年   34061篇
  2002年   33592篇
  2001年   63617篇
  2000年   65325篇
  1999年   55391篇
  1998年   14650篇
  1997年   13460篇
  1996年   12939篇
  1995年   12221篇
  1994年   11468篇
  1992年   42767篇
  1991年   41285篇
  1990年   40560篇
  1989年   39557篇
  1988年   36968篇
  1987年   36414篇
  1986年   34904篇
  1985年   33105篇
  1984年   24826篇
  1983年   21057篇
  1982年   12668篇
  1981年   11570篇
  1980年   10773篇
  1979年   23927篇
  1978年   17069篇
  1977年   14837篇
  1976年   13387篇
  1975年   15267篇
  1974年   18081篇
  1973年   17560篇
  1972年   16810篇
  1971年   15717篇
  1970年   14914篇
  1969年   14348篇
  1968年   13460篇
  1967年   12017篇
  1966年   11260篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Introduction The associations between vitamin D receptor (VDR) Bsm I and Fok I genotypes, parity, and risk of osteoporotic hip fracture were evaluated in a statewide population-based case-control study in Utah.Methods Women age 50–89 years with hip fracture (n=882) were ascertained via surveillance of 18 Utah hospitals from 1997 to 2001. Age-matched controls were randomly selected (n=897). Participants were interviewed in their homes, and blood samples were collected for genotyping.Results In logistic regression analyses that controlled for multiple confounders, Bsm I VDR genotype but not Fok I genotype was associated with risk of osteoporotic hip fracture (OR bb vs. BB genotype: 0.68; 95% CI: 0.50, 0.95). In similar analyses, no overall association was observed between parity status and risk of osteoporotic hip fracture. However, the effect of VDR genotype was modified by parity status. Among nulliparous women (n=140), Bsm I genotype was not associated with risk of hip fracture (OR bb vs. BB: 0.82; 95% CI: 0.28, 2.4); among primiparous women (n=133), bb genotype was associated with increased risk of hip fracture (OR bb vs. BB: 3.30; 95% CI: 0.96, 11.29); among multiparous women (n=1,400), bb genotype was associated with decreased risk of hip fracture (OR bb vs. BB: 0.59; 95% CI: 0.42, 0.84).Conclusion VDR Bsm I genotype was associated with risk of hip fracture in Utah women, and this effect was modified by parity status. Hormonal or lifestyle factors related to parity may underlie this interaction.  相似文献   
82.
There are no data available combining transbronchial needle aspiration (TBNA) of mediastinal lymph nodes and positron emission tomography (PET) in the staging of nonsmall cell lung cancer (NSCLC). The aim of the current study was to determine if these two methods can enhance the negative predictive value of the individual modality alone, for a specific lymph node station, and if this integrated approach can reduce the number of mediastinoscopies. A total of 113 patients with enlarged mediastinal lymph nodes (> or = 1 cm), who underwent both TBNA and PET scanning, were included. In 51 patients, histopathology, confirmed by surgical lymph node dissection, was compared with PET results and TBNA. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy to detect malignant lymphadenopathy was 68 (13/19), 89 (119/134), 46 (13/28), 95 (119/125) and 86% (132/152) for PET, respectively; 54% (6/11), 100 (53/53), 100 (6/6), 91 (53/58) and 92% (59/64), respectively for TBNA; and 100 (11/11), 94 (50/53), 79 (11/14), 100 (50/50) and 95 (61/64) for combined TBNA and PET, respectively. Combination of transbronchial needle aspiration and positron emission tomography has the potential to allow adequate mediastinal staging of nonsmall cell lung cancer with enlarged lymph nodes in most patients without the need for mediastinoscopy.  相似文献   
83.
84.
85.
86.
87.
Abstract Chorea is a rare complication of polycythaemia vera. Polycythaemic chorea occurs predominantly in females and usually in generalised form. We present a 66-year-old woman with acute onset hemichorea-ballism with no vascular pathology in the basal ganglia region. A clear relationship was observed between the onset of chorea and worsening of haematological parameters in the patient. After repeated phlebotomies the patient's clinical status was improved. Polycythaemic chorea must be considered, especially in the elderly, as early diagnosis leads to effective treatment and prevention of complications.  相似文献   
88.
89.
A new semi-empirical formula for the evaluation of (n,(3)He) reaction cross-sections at the energy of 14.6 and 20 MeV is presented. Formula was derived using the analytical expression for the evaluation of the (3)He spectrum within the frame of pre-equilibrium exciton model. The systematics obtained is compared with the empirical formula for the (n,(3)He) reaction cross-section.  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