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   4216024篇
  免费   329958篇
  国内免费   13848篇
耳鼻咽喉   58598篇
儿科学   134717篇
妇产科学   110324篇
基础医学   650624篇
口腔科学   113392篇
临床医学   381726篇
内科学   759547篇
皮肤病学   105896篇
神经病学   349733篇
特种医学   163571篇
外国民族医学   503篇
外科学   646632篇
综合类   119212篇
现状与发展   23篇
一般理论   2562篇
预防医学   352667篇
眼科学   98786篇
药学   294347篇
  26篇
中国医学   11298篇
肿瘤学   205646篇
  2021年   55674篇
  2020年   35453篇
  2019年   58387篇
  2018年   73604篇
  2017年   56238篇
  2016年   62273篇
  2015年   75312篇
  2014年   109645篇
  2013年   174766篇
  2012年   120472篇
  2011年   125953篇
  2010年   125134篇
  2009年   126492篇
  2008年   112311篇
  2007年   119665篇
  2006年   128448篇
  2005年   123638篇
  2004年   123913篇
  2003年   114337篇
  2002年   103602篇
  2001年   149683篇
  2000年   144541篇
  1999年   134314篇
  1998年   70077篇
  1997年   66198篇
  1996年   64410篇
  1995年   59686篇
  1994年   53774篇
  1993年   50038篇
  1992年   96052篇
  1991年   92646篇
  1990年   89065篇
  1989年   86824篇
  1988年   80030篇
  1987年   78518篇
  1986年   73863篇
  1985年   72982篇
  1984年   61663篇
  1983年   55428篇
  1982年   46017篇
  1981年   43116篇
  1980年   40504篇
  1979年   53109篇
  1978年   44038篇
  1977年   38885篇
  1976年   36264篇
  1975年   36274篇
  1974年   39410篇
  1973年   37635篇
  1972年   35244篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
995.
BACKGROUND: Psychotic symptoms in Alzheimer disease (AD+P) identify a heritable phenotype associated with more rapid cognitive decline. The authors have proposed that AD+P is itself a composite of a misidentification and a paranoid subtype with increased cognitive impairment restricted to the misidentification type. Most prior studies of the clinical correlates of AD+P have been limited, however, by the inclusion of prevalent cases. METHODS: Subjects with possible or probable AD or mild cognitive impairment (MCI) without psychosis at study entry were assessed at the time of initial presentation and then annually. Psychotic symptoms were assessed using the CERAD Behavioral Rating Scale. Survival analyses used Cox proportional hazard models with time-dependent covariates to examine the predictors of psychosis onset. RESULTS: A total of 288 subjects completed at least one follow-up examination. Mean duration of follow-up was 22.1 months. The incidence of psychosis was 0.19 per person-year. Cognitive impairment was associated with onset of psychosis, largely as a result of its association with onset of the misidentification, but not the paranoid, subtype. Including psychotropic medication use in the model revealed an association of antidepressant use with the onset of psychosis. This latter association appeared to arise from an underlying association between depression and the risk of psychosis onset rather than from antidepressant treatment. CONCLUSION: These findings are consistent with the hypothesis that the misidentification and the paranoid subtypes each define a more biologically homogeneous group than AD+P as a whole. Further exploration of the relationship between depressive symptoms and psychosis in patients with AD is warranted.  相似文献   
996.
997.
目的建立胰胆管合流异常的动物模型。方法选用健康杂种猫10只。术前禁食12 h,3.5%戊巴比妥钠麻醉后,取上腹正中切口约6 cm切开各层至腹腔。于胆总管入十二指肠处旁边,切开胰腺背膜,解剖胰管;靠近十二指肠处分别纵向切开胰管、胆管长约4~6 mm的切口。6-0线间断吻合切口,造成类似人类的胰胆管合流的共同通道。术后20天胆道造影。结果术后动物精神、食欲良好,无萎靡、烦燥等表现,造影显示胰胆管合流共同通道延长。结论本动物模型最接近于人类的胰胆管合流异常生理,优于其他动物模型。  相似文献   
998.
BACKGROUND: Previous research has demonstrated that academic and neuropsychological functions are compromised in pediatric bipolar disorder (PBD). Investigation of the degree to which neuropsychological deficits might contribute to those academic problems is needed to aid in the recognition and intervention for school achievement difficulties in PBD. METHODS: A sample of 55 children and adolescents with PBD with and without attention-deficit/hyperactivity disorder (ADHD) (PBD group, n = 28; PBD+ADHD group, n = 27) were tested with a computerized neurocognitive battery and standardized neuropsychological tests. Age range of subjects was 7-17 years, with the mean age of 11.97 (3.18) years. Parents completed a structured questionnaire on school and academic functioning. RESULTS: Logistic regression analyses indicated that executive function, attention, working memory, and verbal memory scores were poorer in those with a history of reading/writing difficulties. A separate logistic regression analysis found that attentional dysfunction predicted math difficulties. These relationships between neuropsychological function and academic difficulties were not different in those with PBD+ADHD than in those with PBD alone. CONCLUSIONS: In PBD neuropsychological deficits in the areas of attention, working memory, and organization/problem solving skills all contribute to academic difficulties. Early identification and intervention for these difficulties might help prevent lower academic achievement in PBD.  相似文献   
999.
1000.
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