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   15681篇
  免费   998篇
  国内免费   58篇
耳鼻咽喉   218篇
儿科学   360篇
妇产科学   292篇
基础医学   2256篇
口腔科学   1728篇
临床医学   1154篇
内科学   3123篇
皮肤病学   400篇
神经病学   1089篇
特种医学   331篇
外科学   1693篇
综合类   82篇
一般理论   6篇
预防医学   1696篇
眼科学   405篇
药学   1167篇
中国医学   164篇
肿瘤学   573篇
  2023年   145篇
  2022年   282篇
  2021年   628篇
  2020年   379篇
  2019年   538篇
  2018年   653篇
  2017年   426篇
  2016年   496篇
  2015年   587篇
  2014年   740篇
  2013年   848篇
  2012年   1356篇
  2011年   1394篇
  2010年   689篇
  2009年   589篇
  2008年   971篇
  2007年   950篇
  2006年   788篇
  2005年   680篇
  2004年   645篇
  2003年   502篇
  2002年   420篇
  2001年   278篇
  2000年   245篇
  1999年   247篇
  1998年   89篇
  1997年   50篇
  1996年   42篇
  1995年   44篇
  1994年   24篇
  1993年   25篇
  1992年   79篇
  1991年   84篇
  1990年   72篇
  1989年   70篇
  1988年   80篇
  1987年   69篇
  1986年   52篇
  1985年   51篇
  1984年   34篇
  1983年   35篇
  1980年   27篇
  1979年   24篇
  1975年   20篇
  1974年   30篇
  1973年   31篇
  1971年   18篇
  1970年   18篇
  1969年   18篇
  1967年   21篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
7.
8.
9.
Objective:The present study evaluates a training program for fitting different hearing protection devices (HPDs) based on personal attenuation rating (PAR) before, immediately after, and six months after training.Methods:A total of 67 workers from a public university in the city of São Paulo, Brazil, were invited to participate in the measurement of PARs for foam and silicone protectors through the 3M™ E-A-Rfit Validation System. Two evaluations were performed for each protector at each sampling date: one after reading printed material (the package instructions) and another after being trained by an audiologist. The same procedures were repeated after six months. The final sample consisted of 30 individuals. ANOVA was used for statistical analysis.Results:Larger PAR values were observed after training by the audiologist, and smaller values were observed after six months. Then, after re-training, the values increased again. There were no statistically significant differences in PAR among the HPDs tested. Even after the two training sessions, 23 to 27% of the subjects did not obtain adequate PAR values.Conclusion:These findings emphasize the need for continual worker training in the correct fit of earplug HPDs and the importance of longitudinal PAR monitoring. In addition, some workers, despite the training provided, did not adapt to the HPDs used. Therefore, it is essential that other protection methods and/or other HPD types are made available to these individuals.Key words: Hearing, noise-induced hearing loss, occupational health, personal protective equipment, hearing protection devices  相似文献   
10.
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   
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