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   384993篇
  免费   19089篇
  国内免费   795篇
耳鼻咽喉   5019篇
儿科学   11432篇
妇产科学   8851篇
基础医学   54816篇
口腔科学   10196篇
临床医学   30388篇
内科学   84118篇
皮肤病学   10042篇
神经病学   33868篇
特种医学   11448篇
外国民族医学   107篇
外科学   46573篇
综合类   1708篇
一般理论   87篇
预防医学   38792篇
眼科学   8720篇
药学   27793篇
中国医学   1248篇
肿瘤学   19671篇
  2023年   2376篇
  2022年   1979篇
  2021年   6308篇
  2020年   3822篇
  2019年   6539篇
  2018年   13081篇
  2017年   8661篇
  2016年   8128篇
  2015年   8819篇
  2014年   9963篇
  2013年   15133篇
  2012年   24105篇
  2011年   24553篇
  2010年   12876篇
  2009年   10219篇
  2008年   20809篇
  2007年   22049篇
  2006年   20700篇
  2005年   20260篇
  2004年   19012篇
  2003年   17601篇
  2002年   16734篇
  2001年   10572篇
  2000年   11015篇
  1999年   9339篇
  1998年   2050篇
  1997年   1600篇
  1996年   1582篇
  1992年   5410篇
  1991年   4803篇
  1990年   4681篇
  1989年   4174篇
  1988年   3927篇
  1987年   3670篇
  1986年   3587篇
  1985年   3285篇
  1984年   2418篇
  1983年   2059篇
  1979年   2368篇
  1978年   1624篇
  1977年   1555篇
  1975年   1668篇
  1974年   2054篇
  1973年   2116篇
  1972年   1984篇
  1971年   1933篇
  1970年   1809篇
  1969年   1919篇
  1968年   1848篇
  1967年   1620篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.

Background

Limited data exists demonstrating the efficacy of minimally invasive surgery (MIS) compared to median sternotomy (MS) for multiple valvular disease (MVD). This systematic review and meta-analysis aims to compare operative and peri-operative outcomes of MIS vs MS in MVD.

Methods

PubMed, Ovid, and Embase were searched from inception until August 2019 for randomized and observational studies comparing MIS and MS in patients with MVD. Clinical outcomes of intra- and postoperative times, reoperation for bleeding and surgical site infection were evaluated.

Results

Five observational studies comparing 340 MIS vs 414 MS patients were eligible for qualitative and quantitative review. The quality of evidence assessed using the Newcastle-Ottawa scale was good for all included studies. Meta-analysis demonstrated increased cardiopulmonary bypass time for MIS patients (weighted mean difference [WMD], 0.487; 95% confidence interval [CI], 0.365-0.608; P < .0001). Similarly, aortic cross-clamp time was longer in patients undergoing MIS (WMD, 0.632; 95% CI, 0.509-0.755; P < .0001). No differences were found in operative mortality, reoperation for bleeding, surgical site infection, or hospital stay.

Conclusions

MIS for MVD have similar short-term outcomes compared to MS. This adds value to the use of minimally invasive methods for multivalvular surgery, despite conferring longer operative times. However, the paucity in literature and learning curve associated with MIS warrants further evidence, ideally randomized control trials, to support these findings.
  相似文献   
3.

Background

Since recent reports have shown that (-)-Epigallocatechin-3-gallate (EGCG) could be used for treating proliferative and inflammatory disorders, we explored its use for the management of corneal chemical burns.

Materials and methods

Initially, EGCG was assayed on the rabbit corneal epithelial cell line RCE1(5T5) to establish the best testing conditions, and to avoid unwanted outcomes in the experimental animals. Then, we studied its effects on cell proliferation, cell cycle progression and cell differentiation. Afterwards, we instilled EGCG in experimental grade II corneal alkali burns in mice, three times a day up to 21 days, and evaluated by slit lamp examination and histological sections of corneal epithelial, corneal endothelial and stromal edema, as well as the presence of inflammatory cells and neovascularization.

Results

EGCG reduced cell growth and led to a decline in the proportion of proliferative cells in a concentration dependent manner. At 10 μM, EGCG promoted cell differentiation, an effect not related with apoptosis or cytotoxicity. When 10 μM EGCG was instilled in corneal alkali burns in mice three times a day up to 21 days, EGCG significantly reduced corneal opacity and neovascularization. The improved clinical appearance of the cornea was associated to a controlled epithelial growth; epithelial morphology was similar to that observed in normal epithelium and contrasted with the hyperproliferative, desquamating epithelium observed in control burn wounds. EGCG reduced corneal, stromal and endothelial edema, and wound inflammation.

Conclusion

This work constitutes the first evidence for the use of EGCG in the acute phase of a corneal alkali burn, representing a possible novel alternative to improve patient outcomes as an add-on therapy.  相似文献   
4.
5.
6.
7.
8.
9.
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