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   7971篇
  免费   2525篇
  国内免费   47篇
耳鼻咽喉   138篇
儿科学   131篇
妇产科学   240篇
基础医学   110篇
口腔科学   302篇
临床医学   3289篇
内科学   1410篇
皮肤病学   220篇
神经病学   934篇
特种医学   188篇
外科学   1453篇
综合类   4篇
预防医学   1206篇
眼科学   410篇
药学   47篇
肿瘤学   461篇
  2024年   81篇
  2023年   476篇
  2022年   82篇
  2021年   204篇
  2020年   360篇
  2019年   133篇
  2018年   624篇
  2017年   701篇
  2016年   635篇
  2015年   654篇
  2014年   759篇
  2013年   770篇
  2012年   223篇
  2011年   227篇
  2010年   469篇
  2009年   624篇
  2008年   212篇
  2007年   139篇
  2006年   166篇
  2005年   125篇
  2004年   80篇
  2003年   67篇
  2002年   83篇
  2001年   190篇
  2000年   73篇
  1999年   173篇
  1998年   248篇
  1997年   239篇
  1996年   296篇
  1995年   208篇
  1994年   211篇
  1993年   160篇
  1992年   128篇
  1991年   110篇
  1990年   66篇
  1989年   77篇
  1988年   65篇
  1987年   64篇
  1986年   59篇
  1985年   38篇
  1984年   39篇
  1983年   27篇
  1982年   33篇
  1981年   17篇
  1980年   19篇
  1979年   14篇
  1978年   13篇
  1977年   10篇
  1975年   8篇
  1971年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.

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   
2.
3.
4.
High levels of tumor necrosis factor-alpha (TNF-alpha), a pro-inflammatory cytokine, are present in the wound fluid of chronic nonhealing wounds. This leads to increased inflammation, cytokine expression, and ultimately results in impaired wound healing and tissue destruction. Etanercept is a recombinant fusion protein that consists of the soluble TNF receptor (p75) linked to the Fc portion of human IgG1. It is an effective inhibitor of TNF-alpha and has been shown to provide rapid and sustained improvement in rheumatoid arthritis by acting as a soluble receptor binding TNF-alpha and preventing its proinflammatory activities. Therefore, the aim of this study was to determine whether Etanercept could inhibit TNF-alpha activity in chronic wound fluid. Wound fluid was collected from the venous leg ulcers of 16 different patients. The effect of Etanercept on TNF-alpha activity was evaluated using both a TNF-alpha bioassay and an enzyme-linked immunoassay. Etanercept was found to reduce the cytotoxic effect of chronic wound fluid on L929 fibroblasts by approximately 30% and neutralized TNF-alpha binding in the enzyme-linked immunoassay by up to 80%. Direct application of Etanercept to chronic wounds may therefore reduce the inflammatory activity of TNF-alpha, which could reduce the chronicity of venous leg ulcers and thus aid in the healing of these wounds.  相似文献   
5.
Summary: This is the first report of the largest study of blood pressure measurement in pregnancy in a New Zealand population using standardized definitions and methodology. Over 3,800 women who delivered in an 8-month period in the Wellington region were included in the study. Blood pressure measurement and the presence of oedema and proteinuria were recorded from booking until delivery and in the puerperium. Only 2.7% of women were unable to be contacted after delivery for details on outcomes. The results established normal ranges for blood pressure throughout pregnancy. The data show that Mood pressure greater than 140/90 until 35 weeks' gestation is outside 2 standard deviations at all gestations and justifies using these measurements as the definition of hypertension in pregnancy. The fall in blood pressure in the 2nd trimester was less than 1 mm Ffg per week in both the systolic and diastolic pressures. This fall was smaller than previously recorded in other studies. Gestational hypertension was the commonest blood pressure abnormality occurring in 15.2% of the population. This represented 69% of the pregnant women with a hypertensive disorder. The overall incidence of both gestational hypertension and preeclampsia was 18.5% which is higher than reported in other parts of the world. In this study obesity was significantly associated with hypertensive disorders in pregnancy. An arm circumference of >33 cm, one of the measurements of obesity, was found in 6.8% of the study population. Even after the effect of arm circumference was taken into account, hypertensive disorders were also more common in Pacific Island women. Ankle oedema was significantly associated with the development of both gestational hypertension and preeclampsia but the incidence of oedema was noted in only 11.9% of the subjects.  相似文献   
6.
7.
8.
Fracture of the metatarsal head is uncommon, and reports of isolated osteochondral fracture of the metatarsal head are rare. Because of the distal location of the fracture, it is difficult to achieve and maintain reduction, and potential complications include avascular necrosis and subchondral fatigue fracture. The authors present a case of an osteochondral fracture in a 40-year-old man, which was treated by open reduction and internal fixation with a single twist-off screw, with good results 12 months postoperatively.  相似文献   
9.
10.
Recent New Labour policy for the ‘modernisation’ of Government places a good deal of emphasis on decentralisation. This emphasis is particularly marked in relation to the organisation of primary care. However, like hospitals and other National Health Service institutions, primary care trusts (PCTs) are subject to a substantial raft of centrally established performance targets and indicators, including those which contribute to the public award of between zero and three performance ‘stars’. This raises questions about the extent to which employees can exercise autonomy in the context of rigid top‐down directives. This paper presents findings from a study using participant observation and interviews to examine the impact of a training course aimed ostensibly at increasing employee autonomy in an English PCT. The suggestion is that attempts to make employees more autonomous can be seen as a strategy for increasing central control based upon the internalisation by the employees of centrally promulgated values. The attraction of such strategies is that they may be potentially more effective and less costly than alternative strategies of direct control. However, the study suggests that the outcome of attempts by such methods as programmes to increase employee autonomy may be very different from those intended.  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