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   1004篇
  免费   56篇
  国内免费   2篇
耳鼻咽喉   9篇
儿科学   35篇
妇产科学   17篇
基础医学   85篇
口腔科学   53篇
临床医学   119篇
内科学   191篇
皮肤病学   7篇
神经病学   67篇
特种医学   20篇
外科学   270篇
综合类   10篇
预防医学   16篇
眼科学   84篇
药学   24篇
中国医学   7篇
肿瘤学   48篇
  2024年   2篇
  2023年   21篇
  2022年   26篇
  2021年   53篇
  2020年   45篇
  2019年   53篇
  2018年   50篇
  2017年   29篇
  2016年   27篇
  2015年   34篇
  2014年   33篇
  2013年   86篇
  2012年   87篇
  2011年   68篇
  2010年   43篇
  2009年   31篇
  2008年   46篇
  2007年   55篇
  2006年   54篇
  2005年   50篇
  2004年   35篇
  2003年   28篇
  2002年   30篇
  2001年   16篇
  2000年   10篇
  1999年   8篇
  1998年   7篇
  1997年   4篇
  1996年   1篇
  1994年   2篇
  1993年   1篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1987年   1篇
  1985年   1篇
  1983年   1篇
  1979年   1篇
  1978年   2篇
  1977年   2篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1970年   5篇
  1969年   3篇
排序方式: 共有1062条查询结果,搜索用时 15 毫秒
1.
2.
BACKGROUND: Ventilator-associated pneumonia is the leading nosocomial infection in critically ill patients. The frequency of ventilator-associated pneumonia caused by multidrug-resistant bacteria has increased in recent years, and these pathogens cause most of the deaths attributable to pneumonia. The authors, therefore, evaluated factors associated with selected multidrug-resistant ventilator-associated pneumonia in critical care patients. METHODS: The authors prospectively recorded potential risk factors at the time of intensive care unit admission. An endotracheal aspirate was obtained in all patients who met clinical criteria for pneumonia. Patients were considered to have ventilator-associated pneumonia only when they met the clinical criteria and aspirate culture was positive for bacteria 48 h or more after initiation of mechanical ventilation. Pediatric patients were excluded. Adult patients with ventilator-associated pneumonia were first grouped as "early-onset" (< 5 days) and "late-onset," determined by episodes of ventilator-associated pneumonia, and then, assigned to four groups based on the bacteria cultured from their tracheal aspirates: Pseudomonas aeruginosa, Acinetobacter baumanii, methicillin-resistant staphylococci, and all others. The first three bacteria were considered to be multidrug resistant, whereas the others were considered to be antibiotic susceptible. Potential risk factors were evaluated with use of univariate statistics and multivariate regression. RESULTS: Among 486 consecutive patients admitted during the study, 260 adults underwent mechanical ventilation for more than 48 h. Eighty-one patients (31%) experienced 99 episodes of ventilator-associated pneumonia, including Pseudomonas(33 episodes), methicillin-resistant staphylococci (17 episodes), Acinetobacter(9 episodes), and nonresistant bacteria (40 episodes). Sixty-six of these episodes were early onset and 33 episodes were late onset. Logistic regression analysis identified three factors significantly associated with early-onset ventilator-associated pneumonia caused by any one of the multidrug-resistant bacterial strains: emergency intubation (odds ratio, 6.4; 95% confidence interval, 2.0-20.2), aspiration (odds ratio, 12.7; 95% confidence interval, 2.4-64.6), and Glasgow coma score of 9 or less (odds ratio, 3.9; 95% confidence interval, 1.3-11.3). A. baumanii-related pneumonia cases were found to be significantly associated with two of these factors: aspiration (odds ratio, 14.2; 95% confidence interval, 1.5-133.8) and Glasgow coma score (odds ratio, 6.0; 95% confidence interval, 1.1-32.6). CONCLUSIONS: The authors recommend that patients undergoing emergency intubation or aspiration or who have a Glasgow coma score of 9 or less be monitored especially closely for early-onset multidrug-resistant pneumonia. The occurrence of aspiration and a Glasgow coma score of 9 or less are especially associated with pneumonia caused by A. baumanii.  相似文献   
3.
Purpose: To describe fulminant toxoplasma retinochoroiditis induced by corticosteroid monotherapy.

Methods: Clinical records of nine patients were reviewed.

Results: All patients (five female, four male; aged 15–64 years) had been misdiagnosed as unilateral non-infectious uveitis and given systemic and/or local corticosteroid injections elsewhere. Mean disease duration before referral was 105.6 ± 71 (45–240) days. Visual acuity at presentation was <20/200 in six eyes. Average lesion size was 6.6 disc areas in eight eyes and all four quadrants were involved in one. Toxoplasma DNA was detected in eight tested eyes. Mean duration of anti-toxoplasmic therapy was 92.5 ± 37.1 days. Three eyes developed rhegmatogenous retinal detachment. Four patients underwent pars plana vitrectomy. Final visual acuity was <20/200 in five eyes.

Conclusions: Iatrogenic immunosuppression due to initial misdiagnosis may lead to an aggressive course and serious complications of ocular toxoplasmosis, a potentially self-limiting infection.  相似文献   

4.
BACKGROUND/PURPOSE: Preventing thrombus formation after caustic esophageal ingestion has been proposed to have beneficial effects. Therefore, an experimental study was carried out to investigate the effects of heparin on the esophagus after caustic burns. METHODS: Caustic esophageal burns were produced in rats by irrigation with 50% NaOH as described by Liu. Rats were divided into four groups as follows: group A, animals with esophageal burns, received placebo and underwent autopsy 48 hours after caustic injury; group B, animals with esophageal burns, received subcutaneous heparin treatment and underwent autopsy 48 hours after caustic injury; group C, animals with esophageal burns, received placebo and underwent autopsy 28 days after caustic injury; group D, animals with esophageal burns, received subcutaneous heparin treatment for 7 days and underwent autopsy 28 days after caustic injury. Histopathologic evaluation was performed in all groups, and collagen content of esophageal sections was analyzed by determination of hydroxyproline levels. RESULTS: Submucosal vascular thrombosis was encountered in all group A animals but the submucosal venules and arterioles were patent in most of group B animals. Esophageal strictures did not develop in any of group D animals, although varying degree of esophageal stenoses were encountered in all animals of group C. The circumferences of the burned segment have been narrowed to 3+/-1 mm in group C rats. There was obvious collagen deposition in submucosa, and epithelial regeneration was not complete in group C rats. Submucosa and epithelial integrity seemed normal in group D animals. Hydroxyproline contents in group D were significantly lower compared with group C (P < .05). CONCLUSIONS: Heparin has ameliorating effects on stricture formation after caustic esophageal burn. Those effects may occur through possible anticoagulant, antithrombotic, and endothelial protective effects, and modifying effects of heparin on wound healing.  相似文献   
5.

Background:

Epiphrenic diverticula are rare outpouchings of the distal esophagus that infrequently require surgical intervention for the treatment of symptoms. In cases where surgical therapy is indicated, the traditional approach is through a thoracotomy. Advances in minimally invasive techniques have led to thoracoscopic and more recently laparoscopic management of epiphrenic diverticula. The purpose of this article is to review the literature on minimally invasive surgery for epiphrenic diverticula with particular attention to the operative approach and technique, surgical mortality and morbidity, and symptomatic outcomes.

Methods:

A review of the literature limited to studies in the English language and performed on humans was conducted on PubMed using the following key words: “esophageal diverticula” and “epiphrenic”. Articles retrieved by the PubMed search were reviewed.

Conclusions:

A minimally invasive approach to epiphrenic diverticula offers reduced operative mortality, decreased length of stay, and similar symptom relief compared with open surgery in the hands of experienced laparoscopic surgeons.  相似文献   
6.

Background

Early assessment of injury severity is important in trauma. Trauma scores are calculated after the fact and are useful for audit and research, but not in the emergency clinical setting. Glucose metabolism is altered in trauma, and we hypothesised that alterations in glucose and lactate levels would be an early predictor of mortality.

Methods

Review of trauma registry data identified 1197 patients between May 2000 and September 2006 who had a trauma-team call out. Data collected included trauma scores, venous glucose (gluc), and arterial lactate (lact) on arrival. The predictive value of these variables was compared by ROC curves.

Results

The mortality rate for patients with gluc >11.0 mmol/L was 13.4% compared to 1.8% in those with gluc ≤11.0 mmol/L (p < 0.0001). Gluc had a specificity of 93.2% and a sensitivity of 37.9% for death. 13.0% of patients with lact >2.0 mmol/L died, versus 2.7% with lact ≤2.0 mmol/L, (p 0.0003, specificity 56.8% and sensitivity 81.0%). Glucose was the better biochemical predictor of mortality compared to lactate (ROC area 0.845 and 0.716, respectively). The TRISS (trauma and injury severity score) was a very accurate predictor (ROC 0.963), whereas the ISS (injury severity score) significantly less so (ROC 0.854). There was a significant correlation between gluc, ISS, and TRISS (p 0.01), as well as lactate and ISS (p 0.01).

Conclusion

Glucose and lactate can predict mortality in severe trauma. The predictive value of glucose is comparable to that of ISS, and can be more easily employed in the clinical setting.  相似文献   
7.
Procalcitonin (PCT) is increasingly recognised as an important diagnostic parameter in clinical evaluation of the critically ill. This prospective study was designed to investigate PCT as a diagnostic marker of infection in critically ill patients with sepsis. Eighty-five adult ICU patients were studied. Four groups were defined on the basis of clinical, laboratory and bacteriologic findings as systemic inflammatory response syndrome (SIRS) (n = 10), sepsis (n = 16), severe sepsis (n = 18) and septic shock (n = 41). Data were collected including C-reactive protein (CRP), PCT levels and Sequential Organ Failure Assessment and Acute Physiology and Chronic Health Evaluation II scores on each ICU day. PCT levels were significantly higher in patients with severe sepsis and septic shock (19.25 +/- 43.08 and 37.15 +/- 61.39 ng/ml) than patients with SIRS (0.73 +/- 1.37 ng/ml) (P < 0.05 for each comparison). As compared with SIRS patients, plasma PCT levels were significantly higher in infected patients (21.9 +/- 47.8 ng/ml), regardless of the degree of sepsis (P < 0.001). PCT showed a higher sensitivity (73% versus 35%) and specificity (83% versus 42%) compared to CRP in identifying infection as a cause of the inflammatory response. Best cut-off levels were 1.31 ng/ml for PCT and 13.9 mg/dl for CRP. We suggest that PCT is a more reliable marker than CRP in defining infection as a cause of systemic inflammatory response.  相似文献   
8.
9.
10.
Applications in imaging and spectroscopy rely on pulse processing methods for appropriate data generation. Often, the particular method utilized does not highly impact data quality, whereas in some scenarios, such as in the presence of high count rates or high frequency pulses, this issue merits extra consideration. In the present study, a new approach for pulse processing in nuclear medicine imaging and spectroscopy is introduced and evaluated. The new non-linear recursive filter (NLRF) performs nonlinear processing of the input signal and extracts the main pulse characteristics, having the powerful ability to recover pulses that would ordinarily result in pulse pile-up. The filter design defines sampling frequencies lower than the Nyquist frequency.In the literature, for systems involving NaI(Tl) detectors and photomultiplier tubes (PMTs), with a signal bandwidth considered as 15 MHz, the sampling frequency should be at least 30 MHz (the Nyquist rate), whereas in the present work, a sampling rate of 3.3 MHz was shown to yield very promising results. This was obtained by exploiting the known shape feature instead of utilizing a general sampling algorithm. The simulation and experimental results show that the proposed filter enhances count rates in spectroscopy. With this filter, the system behaves almost identically as a general pulse detection system with a dead time considerably reduced to the new sampling time (300 ns). Furthermore, because of its unique feature for determining exact event times, the method could prove very useful in time-of-flight PET imaging.  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