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   955篇
  免费   117篇
  国内免费   7篇
耳鼻咽喉   1篇
儿科学   71篇
妇产科学   11篇
基础医学   149篇
口腔科学   7篇
临床医学   112篇
内科学   174篇
皮肤病学   17篇
神经病学   76篇
特种医学   178篇
外科学   77篇
综合类   20篇
预防医学   69篇
眼科学   4篇
药学   62篇
肿瘤学   51篇
  2022年   7篇
  2021年   9篇
  2020年   14篇
  2019年   10篇
  2018年   14篇
  2017年   10篇
  2016年   12篇
  2015年   12篇
  2014年   14篇
  2013年   38篇
  2012年   20篇
  2011年   39篇
  2010年   21篇
  2009年   24篇
  2008年   28篇
  2007年   43篇
  2006年   36篇
  2005年   38篇
  2004年   20篇
  2003年   29篇
  2002年   38篇
  2001年   25篇
  2000年   31篇
  1999年   25篇
  1998年   26篇
  1997年   29篇
  1996年   26篇
  1995年   18篇
  1994年   23篇
  1993年   17篇
  1992年   15篇
  1991年   17篇
  1990年   27篇
  1989年   31篇
  1988年   29篇
  1987年   15篇
  1986年   31篇
  1985年   20篇
  1984年   22篇
  1983年   11篇
  1982年   17篇
  1981年   11篇
  1980年   10篇
  1979年   17篇
  1978年   12篇
  1977年   12篇
  1976年   12篇
  1975年   15篇
  1974年   8篇
  1971年   11篇
排序方式: 共有1079条查询结果,搜索用时 15 毫秒
61.
62.
The impact of cricoid pressure on laryngoscopy is unknown. We have developed a quantitative method of recording the laryngoscopic view using a rigid, zero-degree endoscope. We found that an image matching the laryngoscopist's view could be obtained by positioning the endoscope along the laryngoscopist's 'line of sight'. Photographing this image allowed us to measure laryngeal exposure. We set out to define the effect of cricoid pressure on laryngoscopy using this method. In 40 patients undergoing elective surgery, laryngoscopy was performed with cricoid pressures of 0-60 N, increasing by increments of 10 N. We photographed the laryngoscopic view at each force and recorded dynamic images as cricoid pressure was released. The change in laryngoscopic view with increasing cricoid pressure fell into one of four broad patterns: little change (11 subjects); gradual deterioration (10 subjects); improvement at low force (< 20 N) followed by deterioration (9 subjects); improvement at high force (> 30 N) (10 subjects). We identified five subjects with a good initial view (anteroposterior length of the rima glottidis > 5 mm) who showed a marked deterioration in laryngoscopic view as cricoid pressure increased; in three of these subjects this progressed to obscure the larynx completely at a force of 30 N, 40 N and 60 N, respectively. We conclude that the effect of cricoid pressure on laryngoscopy is complex. However, in some individuals, a force close to that currently recommended (30 N) may cause a complete loss of the glottic view.  相似文献   
63.
64.
65.
Purpose: In a prospective randomized study a standard dual-tip hemodialysis catheter (PermCath, Sherwood Medical, St. Louis, MO, USA) was compared with a newer split-lumen catheter (Ash Split, Medcomp, Harleysville, PA, USA).Methods: Sixty-nine patients (42 men, 27 women; mean age 62 years) were randomized to receive either the Ash Split (AS) or the PermCath (PC) catheter. The catheters were inserted into the internal jugular vein. The primary outcome evaluated was blood flow measurements during the first six hemodialysis sessions. Secondary outcomes included: technical difficulties encountered at insertion, early complications and late complications requiring catheter removal or exchange.Results: A total of 69 hemodialysis catheters, 33 AS and 36 PC, were successfully inserted in the internal jugular vein (right 60, left 9) of 69 patients. Mean blood flow during dialysis (Qb) was 270.75 ml/min and 261.86 ml/hr for the AS and PC groups respectively (p=0.27). Mean duration of catheter use was 111.7 days (range 5.4–548.9 days) and 141.2 days (range 7.0–560.9 days) in the AS and PC groups respectively (p=0.307). Catheter failures leading to removal or exchange occurred in 20 patients: 14 in the AS group and six in the PC group. Survival curves with censored endpoints (i.e., recovery, arteriovenous fistula formation, peritoneal dialysis and transplantation) showed significantly better outcome with PermCath catheters (p=0.024). There was no significant difference in ease of insertion or early complication rates.Conclusion: The Ash Split catheter allows increased rates of blood flow during hemodialysis but this increase was not significant at the beginning (p=0.21) or end (p=0.27) of the first six hemodialysis sessions. The Ash Split catheter is more prone to minor complications, particularly dislodgment, than the PermCath catheter.  相似文献   
66.
Classifications of perinatal deaths have been undertaken for surveillance of causes of death, but also for auditing individual deaths to identify suboptimal care at any level, so that preventive strategies may be implemented. This paper describes the history and development of the paired obstetric and neonatal Perinatal Society of Australia and New Zealand (PSANZ) classifications in the context of other classifications. The PSANZ Perinatal Death Classification is based on obstetric antecedent factors that initiated the sequence of events leading to the death, and was developed largely from the Aberdeen and Whitfield classifications. The PSANZ Neonatal Death Classification is based on fetal and neonatal factors associated with the death. The classifications, accessible on the PSANZ website (http://www.psanz.org), have definitions and guidelines for use, a high level of agreement between classifiers, and are now being used in nearly all Australian states and New Zealand.  相似文献   
67.
Haslam J 《Nursing times》2004,100(48):56-59
Urinary incontinence is an unpleasant, unwanted and distressing problem that is common among women in the UK. A recent study (Hunskarr et al, 2004) estimated that 10 million women in the UK suffer with urinary incontinence. Stress urinary incontinence (SUI) is the most common form, affecting four million women. The International Continence Society defines SUI as 'the complaint of involuntary leakage [of urine] on effort or exertion, or on sneezing or coughing' (Abrams et al, 2002).  相似文献   
68.
The Heartbeat Award (HBA) scheme is a national nutrition labelling scheme that operates throughout England. The aim of this study was to assess whether the implementation of the HBA scheme in the workplace results in an improvement in eating habits at work. A longitudinal survey of employees using a structured questionnaire pre- and post-HBA intervention in six workplaces in Leicestershire, England, was conducted. A qualitative food frequency questionnaire was used to assess dietary behaviour 6 months before the scheme was implemented and 6 months afterwards. Four HBA workplaces (n = 453 employees) were compared with two comparison workplaces (n = 124 employees). The outcome measures for dietary change were consumption of 20 food items, i.e. 16 food-frequency and four food-type items. Changes in pre-intervention data compared with post-intervention data evaluated the impact of the HBA on eating habits. Differences were considered statistically different at the p < 0.05 level. Crude and adjusted odds ratios were used to assess differences in change in dietary behaviour between the intervention and comparison workplaces. The results showed that there was significantly more positive change in intervention workplaces only (i.e. the changes were not detected in the comparison workplaces) for four of the 20 food items tested: increase in consumption of fruit (p = 0.029); reduction in consumption of fried foods (p = 0.044) and sweet puddings (p = 0.042); and change to lower fat milks (p = 0.034). In conclusion, the HBA had a modest impact on dietary intake, resulting in a significant positive change in four out of 20 foods consumed by employees in HBA-holding premises.  相似文献   
69.

Background

Patients under haemodialysis are considered at high risk to acquire hepatitis B virus (HBV) infection. Since few data are reported from Brazil, our aim was to assess the frequency and risk factors for HBV infection in haemodialysis patients from 22 Dialysis Centres from Santa Catarina State, south of Brazil.

Methods

This study includes 813 patients, 149 haemodialysis workers and 772 healthy controls matched by sex and age. Serum samples were assayed for HBV markers and viraemia was detected by nested PCR. HBV was genotyped by partial S gene sequencing. Univariate and multivariate statistical analyses with stepwise logistic regression analysis were carried out to analyse the relationship between HBV infection and the characteristics of patients and their Dialysis Units.

Results

Frequency of HBV infection was 10.0%, 2.7% and 2.7% among patients, haemodialysis workers and controls, respectively. Amidst patients, the most frequent HBV genotypes were A (30.6%), D (57.1%) and F (12.2%). Univariate analysis showed association between HBV infection and total time in haemodialysis, type of dialysis equipment, hygiene and sterilization of equipment, number of times reusing the dialysis lines and filters, number of patients per care-worker and current HCV infection. The logistic regression model showed that total time in haemodialysis, number of times of reusing the dialysis lines and filters, and number of patients per worker were significantly related to HBV infection.

Conclusions

Frequency of HBV infection among haemodialysis patients at Santa Catarina state is very high. The most frequent HBV genotypes were A, D and F. The risk for a patient to become HBV positive increase 1.47 times each month of haemodialysis; 1.96 times if the dialysis unit reuses the lines and filters ≥ 10 times compared with haemodialysis units which reuse < 10 times; 3.42 times if the number of patients per worker is more than five. Sequence similarity among the HBV S gene from isolates of different patients pointed out to nosocomial transmission.  相似文献   
70.
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