全文获取类型
收费全文 | 2350642篇 |
免费 | 171727篇 |
国内免费 | 3335篇 |
专业分类
耳鼻咽喉 | 32053篇 |
儿科学 | 75915篇 |
妇产科学 | 62702篇 |
基础医学 | 348398篇 |
口腔科学 | 63639篇 |
临床医学 | 211481篇 |
内科学 | 457426篇 |
皮肤病学 | 51891篇 |
神经病学 | 185326篇 |
特种医学 | 88013篇 |
外国民族医学 | 489篇 |
外科学 | 353912篇 |
综合类 | 47511篇 |
现状与发展 | 12篇 |
一般理论 | 848篇 |
预防医学 | 182795篇 |
眼科学 | 54330篇 |
药学 | 175157篇 |
11篇 | |
中国医学 | 4577篇 |
肿瘤学 | 129218篇 |
出版年
2021年 | 18990篇 |
2019年 | 19554篇 |
2018年 | 27082篇 |
2017年 | 20381篇 |
2016年 | 22771篇 |
2015年 | 25678篇 |
2014年 | 36134篇 |
2013年 | 54003篇 |
2012年 | 74750篇 |
2011年 | 79479篇 |
2010年 | 47096篇 |
2009年 | 44608篇 |
2008年 | 74669篇 |
2007年 | 79526篇 |
2006年 | 80339篇 |
2005年 | 77810篇 |
2004年 | 74395篇 |
2003年 | 71713篇 |
2002年 | 69381篇 |
2001年 | 108764篇 |
2000年 | 111482篇 |
1999年 | 93509篇 |
1998年 | 27000篇 |
1997年 | 23665篇 |
1996年 | 24058篇 |
1995年 | 22720篇 |
1994年 | 20901篇 |
1993年 | 19719篇 |
1992年 | 72014篇 |
1991年 | 70083篇 |
1990年 | 68404篇 |
1989年 | 65678篇 |
1988年 | 60318篇 |
1987年 | 59130篇 |
1986年 | 55225篇 |
1985年 | 53012篇 |
1984年 | 39313篇 |
1983年 | 33398篇 |
1982年 | 19859篇 |
1979年 | 35867篇 |
1978年 | 25653篇 |
1977年 | 21234篇 |
1976年 | 20334篇 |
1975年 | 21819篇 |
1974年 | 26150篇 |
1973年 | 24802篇 |
1972年 | 23200篇 |
1971年 | 22037篇 |
1970年 | 20248篇 |
1969年 | 19316篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Patricia A Wilkosz Sachiko Miyahara Oscar L Lopez Steven T Dekosky Robert A Sweet 《The American journal of geriatric psychiatry》2006,14(4):352-360
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
62.
Mani N Pavuluri Megan Marlow O'Connor Erin M Harral Melissa Moss John A Sweeney 《Neuropsychopharmacology》2006,60(9):951-956
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
63.
64.
65.
66.
67.
68.
69.
70.
C F A Peralta P Cavoretto B Csapo O Falcon K H Nicolaides 《Ultrasound in obstetrics & gynecology》2006,27(2):128-133
OBJECTIVE: To establish reference intervals for the fetal right, left and total lung volumes and heart volume between 12 and 32 weeks of gestation. METHODS: Fetal lung and heart volumes were measured using three-dimensional (3D) ultrasound in 650 normal singleton pregnancies at 12-32 weeks. The VOCAL (Virtual Organ Computer-aided AnaLysis) technique was used to obtain a sequence of six sections of each lung and the heart around a fixed axis, each after a 30 degrees rotation from the previous one. The rotation axis for the lungs extended from the apex to the upper limit of the diaphragm dome, and the rotation axis for the heart extended from its apex to its connection to the great vessels. The contour of each of these organs was drawn manually in the six different rotation planes to obtain the 3D volume measurement. In 60 cases the fetal lungs and heart volumes were measured by the same sonographer twice and also by a second sonographer once in order to compare the measurements and calculate intra- and interobserver agreement. RESULTS: The total lung volume and heart volume increased with gestation, from respective mean values of 1.6 and 0.6 mL at 12 weeks to 10.9 and 4.3 mL at 20 weeks and 49.3 and 26.6 mL at 32 weeks. The right to left lung volume ratio did not change significantly with gestation (median, 0.7), whereas the heart to total lung volume ratio increased with gestation from about 0.3 at 12 weeks to 0.5 at 32 weeks. In the Bland-Altman plot, the difference between paired measurements by two sonographers was, in 95% of the cases, less than 0.05, 0.5 and 1.9 mL for each lung at 12-13, 19-22 and 29-32 weeks, respectively, and the corresponding values for the heart volumes were 0.04, 0.4 and 2.3 mL. CONCLUSIONS: In normal fetuses the lung and heart volumes increase between 12 and 32 weeks of gestation. The extent to which in pathological pregnancies possible deviations in these measurements from normal prove to be useful in the prediction of outcome remains to be determined. 相似文献