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   21824篇
  免费   1093篇
  国内免费   85篇
耳鼻咽喉   272篇
儿科学   518篇
妇产科学   384篇
基础医学   2868篇
口腔科学   2096篇
临床医学   1614篇
内科学   4555篇
皮肤病学   480篇
神经病学   1529篇
特种医学   574篇
外国民族医学   3篇
外科学   2256篇
综合类   192篇
一般理论   2篇
预防医学   3026篇
眼科学   262篇
药学   1488篇
中国医学   229篇
肿瘤学   654篇
  2023年   201篇
  2022年   488篇
  2021年   815篇
  2020年   565篇
  2019年   672篇
  2018年   792篇
  2017年   585篇
  2016年   626篇
  2015年   708篇
  2014年   951篇
  2013年   1135篇
  2012年   1677篇
  2011年   1845篇
  2010年   933篇
  2009年   692篇
  2008年   1252篇
  2007年   1286篇
  2006年   992篇
  2005年   896篇
  2004年   809篇
  2003年   714篇
  2002年   607篇
  2001年   404篇
  2000年   406篇
  1999年   319篇
  1998年   143篇
  1997年   110篇
  1996年   90篇
  1995年   105篇
  1994年   91篇
  1993年   72篇
  1992年   163篇
  1991年   138篇
  1990年   162篇
  1989年   145篇
  1988年   137篇
  1987年   88篇
  1986年   101篇
  1985年   78篇
  1984年   59篇
  1983年   64篇
  1982年   42篇
  1979年   65篇
  1978年   44篇
  1973年   43篇
  1970年   58篇
  1969年   74篇
  1968年   55篇
  1967年   56篇
  1966年   48篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Objective: To assess the quality of images and video clips of fetal central nervous (CNS) structures obtained by ultrasound and transmitted via tele-ultrasound from Brazil to Australia.

Methods: In this cross-sectional study, 15 normal singleton pregnant women between 20 and 26 weeks were selected. Fetal CNS structures were obtained by images and video clips. The exams were transmitted in real-time using a broadband internet and an inexpensive video streaming device. Four blinded examiners evaluated the quality of the exams using the Likert scale. We calculated the mean, standard deviation, mean difference, and p values were obtained from paired t tests.

Results: The quality of the original video clips was slightly better than that observed by the transmitted video clips; mean difference considering all observers = 0.23 points. In 47/60 comparisons (78.3%; 95% CI?=?66.4–86.9%) the quality of the video clips were judged to be the same. In 182/240 still images (75.8%; 95% CI?=?70.0–80.8%) the scores of transmitted image were considered the same as the original.

Conclusion: We demonstrated that long distance tele-ultrasound transmission of fetal CNS structures using an inexpensive video streaming device provided images of subjective good quality.  相似文献   
2.
Spinocerebellar ataxia (SCA) types 2 and 3 are autosomal-dominant neurodegenerative disorders caused by mutations in two different genes. We identified mutations for SCA2 and SCA3 segregating simultaneously in a single Brazilian family. The index patient had SCA2, whereas her two second-degree cousins had SCA3. Disease was more rapidly progressive in the SCA2 patient, who presented severe brainstem and pancerebellar atrophy, as opposed to the two SCA3 patients, who had only mild cerebellar vermian atrophy. In such situations, molecular confirmation of all patients may avoid misdiagnosis of SCA subtypes and eventual errors in predictive testing of unaffected family members.  相似文献   
3.
BACKGROUND: Oral hairy leukoplakia (OHL) may be an indicator of the progression of Human Immunodeficiency Virus (HIV)-induced immuno-depression, and the evaluation of risk factors leading to OHL is important in the management of these HIV-infected patients. However, there are few studies that analyze risk factors leading to OHL in the Brazilian population. The aim of this case-control study is to present data about prevalence rates and risk factors leading to OHL in a sample of HIV-infected adults in Brazil. METHODS: This case-control study included 111 HIV-infected patients treated at a clinic for sexually transmitted diseases and HIV. In the initial examinations with dentists, variables were collected from all patients. Diagnosis of OHL was performed in accordance with the International Classification System and cytological features. The Fisher and the chi-squared tests were used for statistical analysis. The proportional prevalence and odds ratio were estimated. RESULTS: Outcome presented a positive, statistically significant association among the presence of OHL and viral load of 3000 copies/mul or greater (P = 0.0001; odds ratio (OR) = 5.8), presence of oral candidiasis (P = 0.0000; OR = 11.1), previous use of fluconazole (P = 0.0000; OR = 24.6), and use of systemic acyclovir (P = 0.032; OR = 4.3). Antiretroviral medication presented a negative, statistically significant association with the presence of OHL (P = 0.002; OR = 8.4). CONCLUSIONS: Prevalence of OHL was 28.8%. Viral load, oral candidiasis, previous use of fluconazole, and systemic acyclovir were determined to be risk factors for OHL. Antiretroviral medication proved to be protective against the development of OHL.  相似文献   
4.
5.
6.
7.
A model of sleep phasic events such as vertex waves, K complexes, delta waves and sleep spindles is proposed. It consists of feedback loops that are driven by white noise (simulating tonic delta and sigma activity) and by isolated random impulses, simulating vertex waves or K complexes, depending on the background tonic activity. A model-based method for the detection of sleep phasic events was implemented in a personal computer. Its performance was investigated using simulated and real whole-night EEG signals. The method was able to detect K complexes and vertex waves in a reliable way in spite of their variable shapes and in the presence of a variety of background activities. The detector appears to have superior performance to those so far reported in the literature. The performance of the detector was also compared to that of an electroencephalographer using normal sleep EEG records of 8 h duration from 6 subjects. The performance was satisfactory both in terms of accuracy and reliability. The problem of detecting K complexes in stages 3 and 4 of sleep is discussed.  相似文献   
8.
9.
One hundred and forty-four children aged 9-20 months living in 14 villages in a rural area of Guinea-Bissau were examined for circulating rotavirus antibodies twice in a 15-month period. An immunofluorescence technique was used. About 3/4 of the children seroconverted, independent of age on entering the study. The age-specific proportion of seropositivity increased from 4/40 (10%) at 9-11 months to 26/29 (90%) at 33-35 months of age. All the initially seropositive children retained detectable antibodies to rotavirus. The relative risk of seroconversion was 1.4 times (95% confidence interval 1.0-2.0) more common among children living in villages by the mainroad as compared to those living off the road. Contact rate is probably dependent on population density and mobility but not on age. Breast-feeding, decreasing sharply through the age interval covered by the follow-up (9-35 months), had no apparent influence on seroconversion at the ages concerned.  相似文献   
10.
Accidental transmission of Chagas disease to man by blood transfusion is a serious problem in Latin America. This paper describes the testing of several naphthoquinones, some of which were active against blood trypomastigotes in vitro at 4 degrees C and might therefore warrant further study for preventing transmission of Chagas disease by blood transfusion.  相似文献   
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