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   24828篇
  免费   1250篇
  国内免费   82篇
耳鼻咽喉   440篇
儿科学   519篇
妇产科学   415篇
基础医学   3365篇
口腔科学   2417篇
临床医学   1654篇
内科学   5526篇
皮肤病学   474篇
神经病学   2066篇
特种医学   490篇
外科学   3127篇
综合类   76篇
一般理论   9篇
预防医学   2463篇
眼科学   471篇
药学   1523篇
中国医学   173篇
肿瘤学   952篇
  2024年   27篇
  2023年   217篇
  2022年   477篇
  2021年   770篇
  2020年   519篇
  2019年   635篇
  2018年   976篇
  2017年   619篇
  2016年   680篇
  2015年   825篇
  2014年   1047篇
  2013年   1316篇
  2012年   2084篇
  2011年   2448篇
  2010年   1221篇
  2009年   870篇
  2008年   1718篇
  2007年   1828篇
  2006年   1516篇
  2005年   1413篇
  2004年   1221篇
  2003年   1052篇
  2002年   912篇
  2001年   236篇
  2000年   221篇
  1999年   174篇
  1998年   79篇
  1997年   61篇
  1996年   59篇
  1995年   55篇
  1994年   41篇
  1993年   39篇
  1992年   67篇
  1991年   87篇
  1990年   56篇
  1989年   51篇
  1988年   33篇
  1987年   43篇
  1986年   34篇
  1985年   35篇
  1984年   32篇
  1983年   33篇
  1982年   25篇
  1980年   25篇
  1979年   23篇
  1978年   26篇
  1977年   18篇
  1974年   17篇
  1971年   22篇
  1969年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
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   
4.
5.
6.
The outbreaks of rabies in humans transmitted by Desmodus rotundus in 2004 and 2005, in the northeast of the Brazilian State of Para, eastern Amazon basin, made this a priority area for studies on this zoonosis. Given this, the present study provides data on this phenomenon in an urban context, in order to assess the possible circulation of the classic rabies virus (RABV) among bat species in Capanema, a town in the Amazon basin. Bats were collected, in 2011, with mist nets during the wet and dry seasons. Samples of brain tissue and blood were collected for virological and serological survey, respectively. None of the 153 brain tissue samples analyzed tested positive for RABV infection, but 50.34% (95% CI: 45.67-55.01%) of the serum samples analyzed were seropositive. Artibeus planirostris was the most common species, with a high percentage of seropositive individuals (52.46%, 95% CI: 52.31 52.60%). Statistically, equal proportions of seropositive results were obtained in the rainy and dry seasons (c2 = 0.057, d.f. = 1, p = 0.88). Significantly higher proportions of males (55.96%, 95% CI: 48.96-62.96%) and adults (52.37%, 95% CI: 47.35-57.39%) were seropositive. While none of the brain tissue samples tested positive for infection, the high proportion of seropositive specimens indicates that RABV may be widespread in this urban area.  相似文献   
7.
We report on 3 patients with pseudoathetosis, which are involuntary, slow, writhing movements due to loss of proprioception.  相似文献   
8.
9.
10.
Black-pigmented anaerobic rods such as Prevotella spp. and Porphyromonas spp. are involved in the etiology and perpetuation of endodontic infections. The aim of this study was to evaluate the prevalence of these species in chronic endodontic infections by using culture and polymerase chain reaction (PCR) techniques. Samples of 100 patients with root canals displaying chronic endodontic infections were obtained by sterilized paper points. Bacterial identification was performed by using culture and PCR techniques. By culture, in 33% of the samples, P. intermedia-P. nigrescens (75.8%), P. gingivalis (27.3%), and P. endodontalis (9.1%) were identified, and by PCR 60% of the samples harbored P. nigrescens (43.3%), P. gingivalis (43.3%), P. intermedia (31.7%), and P. endodontalis (23.3%). The presence of these black-pigmented anaerobic rods alone or in association in chronic endodontic infections seems to be frequent. PCR is a very sensitive technique for detecting DNA from bacterial cells. Culturing is only able to reveal living bacteria and is less sensitive for the identification of low numbers of bacterial cells.  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