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   3087799篇
  免费   215771篇
  国内免费   4447篇
耳鼻咽喉   43212篇
儿科学   100177篇
妇产科学   83111篇
基础医学   450206篇
口腔科学   85722篇
临床医学   278354篇
内科学   590967篇
皮肤病学   68650篇
神经病学   240669篇
特种医学   117373篇
外国民族医学   676篇
外科学   464324篇
综合类   63117篇
现状与发展   13篇
一般理论   1044篇
预防医学   235464篇
眼科学   72177篇
药学   235350篇
  18篇
中国医学   6537篇
肿瘤学   170856篇
  2019年   24404篇
  2018年   34015篇
  2017年   25909篇
  2016年   29166篇
  2015年   32769篇
  2014年   45976篇
  2013年   68852篇
  2012年   94544篇
  2011年   100641篇
  2010年   59801篇
  2009年   56271篇
  2008年   94260篇
  2007年   100654篇
  2006年   101568篇
  2005年   98269篇
  2004年   94101篇
  2003年   90725篇
  2002年   87810篇
  2001年   145895篇
  2000年   150061篇
  1999年   125914篇
  1998年   35428篇
  1997年   31139篇
  1996年   31450篇
  1995年   29574篇
  1994年   27209篇
  1993年   25662篇
  1992年   96969篇
  1991年   94298篇
  1990年   92435篇
  1989年   88937篇
  1988年   81529篇
  1987年   79934篇
  1986年   75040篇
  1985年   71535篇
  1984年   52936篇
  1983年   44980篇
  1982年   26247篇
  1979年   48439篇
  1978年   34069篇
  1977年   28972篇
  1976年   26993篇
  1975年   29530篇
  1974年   35028篇
  1973年   33518篇
  1972年   31691篇
  1971年   29945篇
  1970年   27596篇
  1969年   26414篇
  1968年   23979篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.

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   
102.
103.
104.
105.
106.
Objective: Report measured resting energy expenditure (REE) in wheelchair rugby athletes and evaluate agreement between REE and the prediction models of Chun, Cunningham, Harris-Benedict, Mifflin, Nightingale and Gorgey, and Owen.

Design: Cohort-based validation study.

Setting. Paralympic team training camp.

Participants: Fourteen internationally competitive athletes who play wheelchair rugby, 13 of whom had cervical spinal cord injuries (SCI).

Outcome Measures: A portable metabolic analyzer was used to measure REE following an overnight fast and dual-energy X-ray absorptiometry (DXA) was used to assess lean body mass for the prediction equations.

Results: REE in the current sample was 1735?±?257?kcal?×?day?1 ranging from 1324 to 2068?kcal?×?day?1 Bhambhani Y. Physiology of wheelchair racing in athletes with spinal cord injury. Sports Med 2002;32(1):2351.[Crossref], [PubMed], [Web of Science ®] [Google Scholar]. Bland–Altman analyses revealed negative mean bias but similar limits of agreement between measured REE and scores predicted by Chun, Cunningham, Mifflin, Nightingale and Gorgey, and Owen models in elite athletes who play wheelchair rugby.

Conclusion: Prediction models regressed on persons with and without SCI under-predicted REE of competitive wheelchair rugby athletes. This outcome may be explained by the higher REE/fat-free mass (FFM) ratio of current athletes compared to less active samples. Findings from the current study will help practitioners to determine nutrient intake needs on training days of varied intensity.  相似文献   
107.
108.
109.
110.
Pulmonary hypertension of the newborn (PHN) constitutes a critical condition with severe cardiovascular and neurological consequences. One of its main causes is hypoxia during gestation, and thus, it is a public health concern in populations living above 2500 m. Although some mechanisms are recognized, the pathophysiological facts that lead to PHN are not fully understood, which explains the lack of an effective treatment. Oxidative stress is one of the proposed mechanisms inducing pulmonary vascular dysfunction and PHN. Therefore, we assessed whether melatonin, a potent antioxidant, improves pulmonary vascular function. Twelve newborn sheep were gestated, born, and raised at 3600 meters. At 3 days old, lambs were catheterized and daily cardiovascular measurements were recorded. Lambs were divided into two groups, one received daily vehicle as control and another received daily melatonin (1 mg/kg/d), for 8 days. At 11 days old, lung tissue and small pulmonary arteries (SPA) were collected. Melatonin decreased pulmonary pressure and resistance for the first 3 days of treatment. Further, melatonin significantly improved the vasodilator function of SPA, enhancing the endothelial‐ and muscular‐dependent pathways. This was associated with an enhanced nitric oxide‐dependent and nitric oxide independent vasodilator components and with increased nitric oxide bioavailability in lung tissue. Further, melatonin reduced the pulmonary oxidative stress markers and increased enzymatic and nonenzymatic antioxidant capacity. Finally, these effects were associated with an increase of lumen diameter and a mild decrease in the wall of the pulmonary arteries. These outcomes support the use of melatonin as an adjuvant in the treatment for PHN.  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