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   3837篇
  免费   153篇
  国内免费   64篇
耳鼻咽喉   16篇
儿科学   121篇
妇产科学   43篇
基础医学   732篇
口腔科学   83篇
临床医学   621篇
内科学   619篇
皮肤病学   19篇
神经病学   155篇
特种医学   196篇
外科学   649篇
综合类   267篇
预防医学   197篇
眼科学   10篇
药学   256篇
中国医学   44篇
肿瘤学   26篇
  2023年   50篇
  2022年   76篇
  2021年   121篇
  2020年   100篇
  2019年   127篇
  2018年   145篇
  2017年   101篇
  2016年   67篇
  2015年   89篇
  2014年   189篇
  2013年   221篇
  2012年   128篇
  2011年   175篇
  2010年   111篇
  2009年   128篇
  2008年   172篇
  2007年   155篇
  2006年   160篇
  2005年   140篇
  2004年   103篇
  2003年   100篇
  2002年   66篇
  2001年   85篇
  2000年   64篇
  1999年   83篇
  1998年   59篇
  1997年   76篇
  1996年   80篇
  1995年   61篇
  1994年   59篇
  1993年   45篇
  1992年   53篇
  1991年   53篇
  1990年   55篇
  1989年   50篇
  1988年   44篇
  1987年   39篇
  1986年   38篇
  1985年   48篇
  1984年   36篇
  1983年   26篇
  1982年   27篇
  1981年   40篇
  1980年   39篇
  1979年   30篇
  1978年   30篇
  1977年   24篇
  1976年   29篇
  1975年   18篇
  1973年   17篇
排序方式: 共有4054条查询结果,搜索用时 15 毫秒
991.
BACKGROUND: In a previous study, we showed that sustained pulmonary hyperinflation, i.e. a lung recruitment maneuver, after closure of the chest in patients undergoing cardiac surgery had significantly negative effects on the central hemodynamics. As elevated pleural pressure is believed to be a major cause of this cardiovascular impairment, we hypothesized that performing the sustained pulmonary hyperinflation under open chest conditions would affect the circulation less. METHODS: Patients undergoing cardiac by-pass surgery were included and sustained pulmonary hyperinflations (40 cmH(2)O airway pressure for 15 s) were performed immediately before and after closure of the sternum. Pulse contour cardiac output, heart rate, mean arterial pressure and pulse pressure variation were measured before, during and 1 min after the hyperinflations. Left ventricular dimensions were measured using trans-esophageal echocardiography. RESULTS: Cardiac output (CO) and mean arterial blood pressure (MAP) decreased significantly during the sustained pulmonary hyperinflation both with an open and closed chest (in parenthesis): CO by 50 (45)% and MAP by 19 (24)%. The left ventricular end-diastolic area was significantly reduced by 24 (33)%. One minute after the hyperinflation, all measured variables had returned to baseline values. No significant differences in the measured variables were found between the two conditions before, during or 1 min after the hyperinflation. CONCLUSION: Contrary to our hypothesis, sustained pulmonary hyperinflations with the chest open, i.e. before sternal closure, had similar negative effects on central hemodynamics as those performed with the chest closed, i.e. after sternal closure.  相似文献   
992.
BACKGROUND: Increases in positive end-expiratory pressure (PEEP) are often associated with cardiovascular depression, responding to fluid loading. Therefore, we hypothesized that if stroke volume (SV) is reduced by an increase in PEEP this reduction is an indicator of hypovolemia or preload responsiveness, i.e. that SV would increase by fluid administration at zero end-expiratory pressure (ZEEP). The relationship between the cardiovascular response to different PEEP levels and fluid load as well as the relation between change in SV as a result of change in preload (Frank-Starling relationship) were evaluated in a porcine model. In addition, other measures of fluid status were assessed. METHODS: Eight, 20-22 kg, anesthetized, mechanically ventilated pigs were subjected to 0, 10, and 20 cm H(2)O PEEP at 10% (of estimated blood volume) hypovolemia, normo- and 10% hypervolemia, and to ZEEP at 20% hypervolemia. SV, cardiac output, intrathoracic blood volume and airway, esophageal, vascular pressures, stroke volume variations, left ventricular end-diastolic and end-systolic areas and respiratory variations in the diameter of the inferior vena cava were obtained. RESULTS: At hypovolemia and normovolemia, 10 cm H(2)O PEEP induced a significant decrease in SV, while no change occurred at 10% hypervolemia. SV measured at ZEEP increased from hypovolemia to normovolemia and 10% hypervolemia, while no change was found between 10% and 20% hypervolemia. The sensitivity and specificity decrease in SV by PEEP indicating an increase in SV by fluids was 60-88% and 67%, respectively, depending on the volemic (preload) levels. CONCLUSION: Although the overall results suggest that a change in SV by PEEP might predict preload responsiveness, the individual response of SV by 10 cm H(2)O PEEP and of the successive fluid administration seemed to be dependent on where on the Frank-Starling curve the heart function was located.  相似文献   
993.
Summary Vascular injury is a rare but not uncommon complication of spinal surgery and associated with dramatic consequences. Congestive heart failure secondary to a hyperkinetic circulation can occur in systemic diseases and in arterio-venous fistulae. A 57-year-old man was admitted to hospital complaining of dyspnoea and oedema of the left leg. Eight days previously he had undergone a discectomy at L4–L5. On auscultation a systolic-diastolic murmur was noted over the entire abdomen. An echocardiogram demonstrated an enlarged right atrium, severe mitral and tricuspid regurgitation and increased pulmonary artery pressure. An abdominal CT demonstrated irregular dilatation of the left common iliac vein and through a fistula and simultaneous opacification of the right common iliac artery; subsequently, this was also confirmed by angiography. The patient underwent an emergency endovascular stent-graft of the right common iliac artery with normalization of the venous return pressure and quick resolution of the heart failure. It is important for the physician involved in clinical work to keep in mind all the possible post-surgical complications that can occur in symptomatic patients who have recently undergone an intervention.  相似文献   
994.
INTRODUCTION H pylori is recognized as the major pathogenetic factor in chronic active gastritis. Chronic active gastritis not only leads to gastric inflammation in various degrees but also can be the cause of gastric and duodenal ulcer disease and might …  相似文献   
995.
Objective: For years researchers have been attempting to understand the relationship between central hemodynamics and the resulting peripheral waveforms. This study is designed to further understanding of the relationship between ear pulse oximeter waveforms, finger pulse oximeter waveforms and cardiac output (CO). It is hoped that with appropriate analysis of the peripheral waveforms, clues can be gained to help to optimize cardiac performance. Methods. Part 1: Studying the effect of cold immersion test on plethysmographic waveforms. Part 2: Studying the correlation between ear and finger plethysmographic waveforms and (CO) during CABG surgery. The ear and finger plethysmographic waveforms were analyzed to determine amplitude, width, area, upstroke and downslope. The CO was measured using continuous PA catheter. Using multi-linear regression, ear plethysmographic waveforms, together with heart rate (HR), were used to determine the CO Agreement between the two methods of CO determination was assessed. Results. Part 1: On contralateral hand immersion, all finger plethysmographic waveforms were reduced, there was no significant change seen in ear plethysmographic waveforms, except an increase in ear plethysmographic width. Part 2: Phase1: Significant correlation detected between the ear plethysmographic width and other ear and finger plethysmographic waveforms. Phase 2: The ear plethysmographic width had a significant correlation with the HR and CO. The correlation of the other ear plethysmographic waveforms with CO and HR are summarized (Table 5). Multi-linear regression analysis was done and the best fit equation was found to be: CO = 8.084 − 14.248 × Ear width + 0.03 ×HR+ 92.322 × Ear down slope+0.027 × Ear Area Using Bland & Altman, the bias was (0.05 L) but the precision (2.46) is large to be clinically accepted. Conclusion. The ear is relatively immune to vasoconstrictive challenges which make ear plethysmographic waveforms a suitable monitor for central hemodynamic changes. The ear plethysmographic width has a good correlation with CO.  相似文献   
996.
The present study investigated the effects of positive end-expiratory pressure (PEEP) on propofol concentrations in humans. Eleven patients undergoing elective surgery were enrolled in this study. Anesthesia was induced with propofol, then maintained using 60% nitrous oxide in oxygen, fentanyl 10-20 microg/kg and continuous infusion of propofol. Vecuronium was used to facilitate the artificial ventilation of the lungs. Propofol was administered to all subjects via target-controlled infusion to achieve a propofol concentration of 6.0 microg/mL at intubation and 2.0 microg/mL after intubation. Before, during and after PEEP level of 10 cmH(2)O, cardiac output (CO) and effective liver blood flow (LBF) was measured using indocyanine green as an indicator and blood propofol concentration was determined using high-performance liquid chromatography. Data are expressed as median and range. After PEEP of 10 cmH(2)O was applied, CO and effective LBF was significantly decreased from 5.5 (3.8-6.8) L/min to 4.5 (3.2-5.8) L/min (P < 0.05), 0.78 (0.65-1.21) L/min to 0.65 (0.50-0.89) L/min (P < 0.05), respectively. Propofol concentration was significantly increased from 2.21 (1.46-2.63) microg/mL to 2.45(1.79-2.89) microg/mL (P < 0.05). These data indicate that propofol concentrations can be increased by PEEP, suggesting the possibility of overdosing following PEEP.  相似文献   
997.
Shock is a life-threatening clinical state in which cellular hypoxia develops due to an imbalance between oxygen supply and demand resulting in end organ dysfunction. It is the end result of a number of pathophysiological processes, and multiple processes may coexist. Shock may be reversible in early stages; however, if appropriate treatment is delayed the effects become irreversible, resulting in multiorgan failure and death. Given the morbidity and mortality associated with shock, its significance has been emphasized in medical education and public health campaigns globally in recent years. Early recognition and timely interventions to treat shock and address the underlying cause(s) are essential to improve outcomes.This article provides an overview of shock syndromes, presents an approach to assessment and investigations, and reviews the management of shock in a general context. It is beyond the scope of one article to discuss the vast subject of shock in as much depth as it deserves.  相似文献   
998.
999.

Introduction

Academic dermatologists in Australia and New Zealand provide high-quality and meaningful contributions to the understanding of disease and therapeutic translational research. Concerns have been raised by the Australian Medical Association regarding the decline of clinical academics in Australia as a whole, however, such trends in scholarly output have not previously been analysed for Australasian dermatologists.

Methods

A bibliometric analysis of dermatologists in Australia and New Zealand was conducted in January and February 2023. Available Scopus profiles for all dermatologists were used to measure lifetime H index, scholarly output, citation counts and field-weighted citation impact (FWCI) in the last 5 years (2017–2022). Trends in output over time were measured using non-parametric tests. Differences in output between subgroups stratified by gender and academic leadership positions (associate professor or professor) were measured using Wilcoxon rank-sum and one-way ANOVA tests. The scholarly output of recent College graduates was also analysed as a subgroup, comparing the same bibliographic variables in the 5 years preceding and 5 years following awarding of their fellowships.

Results

From the 463 practising dermatologists in Australia and New Zealand, 372 (80%) were successfully matched to Scopus researcher profiles. Of these dermatologists, 167 were male (45%) and 205 (55%) were female, and 31 (8%) held academic leadership positions. Most dermatologists (67%) published at least one paper in the last 5 years. The median lifetime H index was 4, and between 2017 and 2022 median scholarly output was 3, the median citations were 14 and the median FWCI was 0.64. There was a non-significant trend towards fewer publications per year, however, citation count and FWCI decreased significantly. By subgroups, female dermatologists published significantly more papers between 2017 and 2022, and other bibliographic variables were comparable to male dermatologists. However, women were underrepresented in positions of academic leadership—comprising only 32% of this cohort despite representing 55% of dermatologists. Professors were also significantly more likely to have higher bibliographic outcomes than associate professors. Finally, analysis of recent College graduates highlighted a significant decline in bibliometric outcomes pre- and post-fellowship.

Conclusion

Overall, our analysis identifies a trend towards decreased research output by dermatologists in Australia and New Zealand in the last 5 years. Strategies to support dermatologists in research endeavours, particularly women and recent graduates, will be essential in maintaining strong scholarly output among Australasian dermatologists and thereby sustaining optimal evidence-based patient care.  相似文献   
1000.
Autonomic dysfunction in persons with acquired immune deficiency syndrome (AIDS) has been reported previously but its incidence in early stage HIV infection and its relation to cardiovascular function have not been fully examined. The present study evaluated cardiovascular and autonomic function in 55 HIV-seronegative, and 52 HIV-asymptomatic and 31 HIV-symptomatic seropositive men. Measures of hemodynamic and autonomic function were obtained at rest and during a standardized battery of autonomic tests. Results were compared across groups while controlling for age, body mass, and physical activity. Analyses indicated that measures of autonomic function did not differ among groups. However, at rest, both HIV seropositive groups exhibited diminished stroke volume and elevated diastolic blood pressure, albeit within normotensive levels. In addition, the ability to sustain a blood pressure response during prolonged challenge and the relationship between stroke volume and baroreceptor/vagal responsiveness were disrupted in the HIV-symptomatic group. Therefore, in the pre-AIDS stages of infection, autonomic functioning appeared intact; yet alterations in baroreceptor/vagal function associated with depressed myocardial function may be an early warning signal reflecting cardiovascular pathological processes potentially exacerbated by HIV spectrum disease. This study was supported by research grant PO1-MH49548 and training grant T32-MH18917 from the National Mental Health Institute of the National Institutes of Health.  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