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   1349940篇
  免费   95436篇
  国内免费   2959篇
耳鼻咽喉   19895篇
儿科学   40546篇
妇产科学   38867篇
基础医学   189080篇
口腔科学   40009篇
临床医学   114109篇
内科学   265408篇
皮肤病学   30521篇
神经病学   107193篇
特种医学   54265篇
外国民族医学   435篇
外科学   210388篇
综合类   31142篇
现状与发展   6篇
一般理论   439篇
预防医学   93308篇
眼科学   31820篇
药学   101109篇
  4篇
中国医学   3066篇
肿瘤学   76725篇
  2018年   12339篇
  2016年   11040篇
  2015年   12346篇
  2014年   17273篇
  2013年   25887篇
  2012年   34018篇
  2011年   35852篇
  2010年   21331篇
  2009年   20705篇
  2008年   34406篇
  2007年   37491篇
  2006年   37927篇
  2005年   36682篇
  2004年   35643篇
  2003年   34558篇
  2002年   34015篇
  2001年   63974篇
  2000年   65640篇
  1999年   55651篇
  1998年   14749篇
  1997年   13547篇
  1996年   13011篇
  1995年   12278篇
  1994年   11520篇
  1992年   42875篇
  1991年   41360篇
  1990年   40649篇
  1989年   39641篇
  1988年   37046篇
  1987年   36471篇
  1986年   34957篇
  1985年   33139篇
  1984年   24865篇
  1983年   21077篇
  1982年   12682篇
  1981年   11578篇
  1979年   23936篇
  1978年   17075篇
  1977年   14847篇
  1976年   13393篇
  1975年   15275篇
  1974年   18087篇
  1973年   17564篇
  1972年   16814篇
  1971年   15718篇
  1970年   14917篇
  1969年   14355篇
  1968年   13463篇
  1967年   12021篇
  1966年   11265篇
排序方式: 共有10000条查询结果,搜索用时 0 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