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   3452篇
  免费   218篇
  国内免费   24篇
耳鼻咽喉   131篇
儿科学   70篇
妇产科学   96篇
基础医学   490篇
口腔科学   81篇
临床医学   291篇
内科学   632篇
皮肤病学   164篇
神经病学   261篇
特种医学   308篇
外科学   552篇
综合类   26篇
预防医学   179篇
眼科学   18篇
药学   261篇
中国医学   1篇
肿瘤学   133篇
  2023年   26篇
  2021年   50篇
  2020年   40篇
  2019年   54篇
  2018年   61篇
  2017年   68篇
  2016年   66篇
  2015年   67篇
  2014年   82篇
  2013年   117篇
  2012年   116篇
  2011年   150篇
  2010年   68篇
  2009年   85篇
  2008年   114篇
  2007年   156篇
  2006年   154篇
  2005年   158篇
  2004年   130篇
  2003年   122篇
  2002年   92篇
  2001年   79篇
  2000年   100篇
  1999年   99篇
  1998年   48篇
  1997年   45篇
  1996年   53篇
  1995年   60篇
  1994年   46篇
  1993年   49篇
  1992年   61篇
  1991年   79篇
  1990年   76篇
  1989年   64篇
  1988年   65篇
  1987年   85篇
  1986年   79篇
  1985年   68篇
  1984年   53篇
  1983年   47篇
  1982年   25篇
  1981年   30篇
  1980年   25篇
  1979年   47篇
  1978年   34篇
  1977年   19篇
  1976年   35篇
  1975年   29篇
  1974年   28篇
  1973年   28篇
排序方式: 共有3694条查询结果,搜索用时 9 毫秒
51.
AIMS: To study the association between gestational age and birth weight and the risk of clinically verified hyperkinetic disorder. METHODS: Nested case-control study of 834 cases and 20 100 controls with incidence density sampling. RESULTS: Compared with children born at term, children born with gestational ages of 34-36 completed weeks had a 70% increased risk of hyperkinetic disorder (rate ratio (RR) 1.7, 95% confidence interval (CI) 1.2 to 2.5). Children with gestational ages below 34 completed weeks had an almost threefold increased risk (RR 2.7, 95% CI 1.8 to 4.1). Children born at term with birth weights of 1500-2499 g had a 90% increased risk of hyperkinetic disorder (RR 1.9, 95% CI 1.2 to 2.9), and children with birth weights of 2500-2999 g had a 50% increased risk (RR 1.5, 95% CI 1.2 to 1.8) compared with children born at term with birth weights above 2999 g. The results were adjusted for socioeconomic status of the parents, family history of psychiatric disorders, conduct disorders, comorbidity, and maternal smoking during pregnancy. Results related to birth weight were unchanged after adjusting for differences in gestational age. CONCLUSIONS: Children born preterm, also close to term, and children born at term with low birth weights (1500-2499 g) have an increased risk of clinically verified hyperkinetic disorder. These findings have important public health perspectives because the majority of preterm babies are born close to term.  相似文献   
52.
PURPOSE Positron emission tomography (PET) has been used in grading of CNS tumors in adults, whereas studies of children have been limited. PATIENTS AND METHODS Nineteen boys and 19 girls (median age, 8 years) with primary CNS tumors were studied prospectively by fluorine-18 2-fluoro-2-deoxy-D-glucose (FDG) PET with (n = 16) or without (n = 22) H(2)(15)O-PET before therapy. Image processing included coregistration to magnetic resonance imaging (MRI) in all patients. The FDG uptake in tumors was semiquantitatively calculated by a region-of-interest-based tumor hotspot/brain index. Eight tumors without histologic confirmation were classified as WHO grade 1 based on location, MRI, and clinical course (22 to 42 months). Results Four grade 4 tumors had a mean index of 4.27 +/- 0.5, four grade 3 tumors had a mean index of 2.47 +/- 1.07, 10 grade 2 tumors had a mean index of 1.34 +/- 0.73, and eight of 12 grade 1 tumors had a mean index of -0.31 +/- 0.59. Eight patients with no histologic confirmation had a mean index of 1.04. For these 34 tumors, FDG uptake was positively correlated with malignancy grading (n = 34; r = 0.72; P < .01), as for the 26 histologically classified tumors (n = 26; r = 0.89; P < .01). The choroid plexus papilloma (n = 1) and the pilocytic astrocytomas (n = 3) had a mean index of 3.26 (n = 38; r = 0.57; P < .01). H(2)(15)O-uptake showed no correlation with malignancy. Digitally performed PET/MRI coregistration increased information on tumor characterization in 90% of cases. CONCLUSION FDG PET of the brain with MRI coregistration can be used to obtain a more specific diagnosis with respect to malignancy grading. Improved PET/MRI imaging of the benign hypermetabolic tumors is needed to optimize clinical use.  相似文献   
53.
Summary Using sucrose gradient centrifugation, human breast cancer estrogen receptors appear in two molecular forms sedimenting at either 8S or 4S fractions. The sum of these two fractions has been valuable clinically in helping to predict response to hormonal therapies. It has been suggested that the 4S receptor may not be of predictive value and that the practice of using only dextran-coated charcoal methodology might thus overestimate the number of patients whose tumors might be hormonally dependent. The present study correlates clinical response to hormonal manipulations with 8S and 4S receptors as determined by sucrose density gradient centrifugation. Patients with only 4S positive receptors had a 56% response rate to hormonal manipulation compared with a 52% response rate in patients with positive 8S alone or with both 8S and 4S receptors. Although patient numbers are small in this and the other three published series addressing this question, our data do not confirm two previously published studies suggesting clinical importance of 8S/4S fractionation.  相似文献   
54.
55.
56.
57.
58.
59.
60.
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