首页 | 官方网站   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   1458786篇
  免费   122645篇
  国内免费   14401篇
医药卫生   1595832篇
  2021年   14401篇
  2019年   13006篇
  2018年   17387篇
  2017年   14201篇
  2016年   16135篇
  2015年   19352篇
  2014年   26279篇
  2013年   35576篇
  2012年   44814篇
  2011年   48310篇
  2010年   30167篇
  2009年   28463篇
  2008年   42600篇
  2007年   45025篇
  2006年   46176篇
  2005年   44760篇
  2004年   40999篇
  2003年   39892篇
  2002年   37245篇
  2001年   68837篇
  2000年   70803篇
  1999年   59710篇
  1998年   18867篇
  1997年   17111篇
  1996年   17536篇
  1995年   17639篇
  1994年   16313篇
  1993年   14941篇
  1992年   48172篇
  1991年   46669篇
  1990年   44759篇
  1989年   42514篇
  1988年   39366篇
  1987年   38646篇
  1986年   36275篇
  1985年   35005篇
  1984年   26561篇
  1983年   22260篇
  1982年   13949篇
  1981年   12548篇
  1979年   23640篇
  1978年   17121篇
  1977年   14418篇
  1976年   13220篇
  1975年   13763篇
  1974年   16144篇
  1973年   15426篇
  1972年   14192篇
  1971年   13055篇
  1970年   11891篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Individuals with sudden unilateral deafness offer a unique opportunity to study plasticity of the binaural auditory system in adult humans. Stimulation of the intact ear results in increased activity in the auditory cortex. However, there are no reports of changes at sub-cortical levels in humans. Therefore, the aim of the present study was to investigate changes in sub-cortical activity immediately before and after the onset of surgically induced unilateral deafness in adult humans. Click-evoked auditory brainstem responses (ABRs) to stimulation of the healthy ear were recorded from ten adults during the course of translabyrinthine surgery for the removal of a unilateral acoustic neuroma. This surgical technique always results in abrupt deafferentation of the affected ear. The results revealed a rapid (within minutes) reduction in latency of wave V (mean pre = 6.55 ms; mean post = 6.15 ms; p < 0.001). A latency reduction was also observed for wave III (mean pre = 4.40 ms; mean post = 4.13 ms; p < 0.001). These reductions in response latency are consistent with functional changes including disinhibition or/and more rapid intra-cellular signalling affecting binaurally sensitive neurons in the central auditory system. The results are highly relevant for improved understanding of putative physiological mechanisms underlying perceptual disorders such as tinnitus and hyperacusis.  相似文献   
4.
5.
Vestibular function laboratories utilize a multitude of diagnostic instruments to evaluate a dizzy patient. Caloric irrigators, oculomotor stimuli, and rotational chairs produce a stimulus whose accuracy is required for the patient response to be accurate. Careful attention to everything from cleanliness of equipment to threshold adjustments determine on a daily basis if patient data are going to be correct and useful. Instrumentation specifications that change with time such as speed and temperature must periodically be checked using calibrated instruments.  相似文献   
6.
7.

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   
8.
ABSTRACT

Objective

To investigate primary care physician clinical practice patterns, barriers, and education surrounding pediatric physical activity (PA), and to compare practice patterns by discipline.  相似文献   
9.

Objectives

To investigate whether functional overreaching affects locomotor system behaviour when running at fixed relative intensities and if any effects were associated with changes in running performance.

Design

Prospective intervention study.

Methods

Ten trained male runners completed three training blocks in a fixed order. Training consisted of one week of light training (baseline), two weeks of heavy training designed to induce functional overreaching, and ten days of light taper training designed to allow athletes to recover from, and adapt to, the heavy training. Locomotor behaviour, 5-km time trial performance, and subjective reports of training status (Daily Analysis of Life Demands for Athletes (DALDA) questionnaire) were assessed at the completion of each training block. Locomotor behaviour was assessed using detrended fluctuation analysis of stride intervals during running at speeds corresponding to 65% and 85% of maximum heart rate (HRmax) at baseline.

Results

Time trial performance (effect size ±95% confidence interval (ES): 0.16 ± 0.06; p < 0.001), locomotor behaviour at 65% HRmax (ES: ?1.12 ± 0.95; p = 0.026), and DALDA (ES: 2.55 ± 0.80; p < 0.001) were all detrimentally affected by the heavy training. Time trial performance improved relative to baseline after the taper (ES: ?0.16 ± 0.10; p = 0.003) but locomotor behaviour at 65% HRmax (ES: ?1.18 ± 1.17; p = 0.048) and DALDA (ES: 0.92 ± 0.90; p = 0.045) remained impaired.

Conclusions

Locomotor behaviour during running at 65% HRmax was impaired by functional overreaching and remained impaired after a 10-day taper, despite improved running performance. Locomotor changes may increase injury risk and should be considered within athlete monitoring programs independently of performance changes.  相似文献   
10.

Background

Rosacea is a chronic inflammatory skin condition whose etiology has been linked to mast cells and the antimicrobial peptide cathelicidin LL-37. Individuals with refractory disease have demonstrated clinical benefit with periodic injections of onabotulinum toxin, but the mechanism of action is unknown.

Objectives

To investigate the molecular mechanism by which botulinum toxin improves rosacea lesions.

Methods

Primary human and murine mast cells were pretreated with onabotulinum toxin A or B or control. Mast cell degranulation was evaluated by β-hexosaminidase activity. Expression of botulinum toxin receptor Sv2 was measured by qPCR. The presence of SNAP-25 and VAMP2 was established by immunofluorescence. In vivo rosacea model was established by intradermally injecting LL-37 with or without onabotulinum toxin A pretreatment. Mast cell degranulation was assessed in vivo by histologic counts. Rosacea biomarkers were analyzed by qPCR of mouse skin sections.

Results

Onabotulinum toxin A and B inhibited compound 48/80-induced degranulation of both human and murine mast cells. Expression of Sv2 was established in mouse mast cells. Onabotulinum toxin A and B increased cleaved SNAP-25 and decreased VAMP2 staining in mast cells respectively. In mice, injection of onabotulinum toxin A significantly reduced LL-37-induced skin erythema, mast cell degranulation, and mRNA expression of rosacea biomarkers.

Conclusions

These findings suggest that onabotulinum toxin reduces rosacea-associated skin inflammation by directly inhibiting mast cell degranulation. Periodic applications of onabotulinum toxin may be an effective therapy for refractory rosacea and deserves further study.  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-23

京公网安备 11010802026262号