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   27697篇
  免费   1204篇
  国内免费   96篇
耳鼻咽喉   332篇
儿科学   679篇
妇产科学   653篇
基础医学   3507篇
口腔科学   1736篇
临床医学   2017篇
内科学   6538篇
皮肤病学   561篇
神经病学   2056篇
特种医学   573篇
外科学   3459篇
综合类   146篇
一般理论   34篇
预防医学   3184篇
眼科学   413篇
药学   1798篇
中国医学   169篇
肿瘤学   1142篇
  2023年   245篇
  2022年   253篇
  2021年   680篇
  2020年   410篇
  2019年   679篇
  2018年   1114篇
  2017年   665篇
  2016年   689篇
  2015年   842篇
  2014年   935篇
  2013年   1245篇
  2012年   2210篇
  2011年   2401篇
  2010年   1139篇
  2009年   820篇
  2008年   1841篇
  2007年   1924篇
  2006年   1722篇
  2005年   1672篇
  2004年   1463篇
  2003年   1342篇
  2002年   1244篇
  2001年   477篇
  2000年   517篇
  1999年   389篇
  1998年   114篇
  1997年   71篇
  1996年   59篇
  1995年   54篇
  1994年   39篇
  1993年   47篇
  1992年   231篇
  1991年   163篇
  1990年   142篇
  1989年   126篇
  1988年   106篇
  1987年   101篇
  1986年   86篇
  1985年   75篇
  1984年   58篇
  1983年   58篇
  1979年   31篇
  1975年   38篇
  1974年   52篇
  1973年   30篇
  1971年   35篇
  1970年   36篇
  1969年   32篇
  1968年   38篇
  1967年   28篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
2.
3.
4.
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   
5.
6.
The 2008 dioxin crisis occurred as a result of contamination of Irish pork. The event had significant implications for Ireland’s economy and the reputation of its agricultural industry, as well as raising concerns for human health. This study describes the results of a content analysis of Irish and UK newspaper coverage of the 2008 Irish dioxin crisis, as this is likely to provide insight into how public perceptions of this issue were shaped. Articles from 16 print publications were systematically sampled for the period December 2008 to February 2009. The resulting data set of 141 articles was examined using a coding protocol developed based on previous research and refined during piloting. Results indicated that the dioxin crisis was primarily portrayed by the media as an industry/economic crisis, dominant in 26.9% of articles in the sample. Within this dominant portrayal, the agricultural industry was frequently cited as being in crisis (42.6%); however, the implications of the crisis on the wider economic environment also received attention (17.7%). Differences between Irish and UK-based media were also examined, revealing that while the Irish media most frequently described the crisis in terms of its impact on the industry and economy, the UK media were more likely to portray the crisis as a risk to health. These dominant media messages and message framings have implications for the public understanding of the issue in each country and potential consequences regarding perception of the adequacy of existing food policy and regulatory oversight.  相似文献   
7.
8.
Using 3,3'-diclorophenolsulfoftaleinil N-acetyl-beta-D-glucosaminide as a substrate, the apparent activation energy of beta-N-acetylhexosaminidase (Hex) was determined in samples of plasma and urine, as well as in leukocyte and platelet lysates. Incubation with papain produced an increase in this thermodynamic variable for plasma Hex (precursor forms with high molecular mass) that would be caused by the proteolytic action of papain on the Hex A isoenzyme. However, digestion with papain did not significantly modify the activation energy of Hex in leukocyte and platelet lysates (mature enzymatic forms). In 11 healthy subjects and 28 patients with different renal diseases, no statistically significant differences were found with regard to the values obtained in cellular lysates for variations in the activation energy of urinary Hex, regardless of whether they presented normoalbuminuria, microalbuminuria or macroalbuminuria. These results support the hypothesis that even in patients with proteinuria, no significant amounts of plasma Hex precursor forms are found in urine samples, and the source of the enzyme activity is the kidney itself.  相似文献   
9.
10.
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