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   1340681篇
  免费   94536篇
  国内免费   2940篇
耳鼻咽喉   19806篇
儿科学   40326篇
妇产科学   38712篇
基础医学   187838篇
口腔科学   39901篇
临床医学   112974篇
内科学   263612篇
皮肤病学   30347篇
神经病学   106856篇
特种医学   53813篇
外国民族医学   435篇
外科学   208790篇
综合类   31054篇
现状与发展   6篇
一般理论   436篇
预防医学   92268篇
眼科学   31393篇
药学   100447篇
  4篇
中国医学   2991篇
肿瘤学   76148篇
  2018年   11840篇
  2015年   11959篇
  2014年   16790篇
  2013年   25372篇
  2012年   33258篇
  2011年   35100篇
  2010年   20858篇
  2009年   20339篇
  2008年   33792篇
  2007年   36904篇
  2006年   37502篇
  2005年   36237篇
  2004年   35324篇
  2003年   34296篇
  2002年   33851篇
  2001年   63737篇
  2000年   65435篇
  1999年   55545篇
  1998年   14728篇
  1997年   13516篇
  1996年   13002篇
  1995年   12283篇
  1994年   11529篇
  1992年   42851篇
  1991年   41374篇
  1990年   40625篇
  1989年   39627篇
  1988年   37072篇
  1987年   36477篇
  1986年   34965篇
  1985年   33178篇
  1984年   24867篇
  1983年   21076篇
  1982年   12684篇
  1981年   11590篇
  1980年   10785篇
  1979年   23965篇
  1978年   17107篇
  1977年   14854篇
  1976年   13393篇
  1975年   15290篇
  1974年   18093篇
  1973年   17572篇
  1972年   16822篇
  1971年   15730篇
  1970年   14923篇
  1969年   14357篇
  1968年   13469篇
  1967年   12028篇
  1966年   11267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