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   812篇
  免费   74篇
  国内免费   3篇
耳鼻咽喉   10篇
儿科学   14篇
妇产科学   12篇
基础医学   125篇
口腔科学   4篇
临床医学   101篇
内科学   171篇
皮肤病学   7篇
神经病学   148篇
特种医学   26篇
外科学   83篇
综合类   10篇
预防医学   84篇
眼科学   5篇
药学   44篇
肿瘤学   45篇
  2024年   3篇
  2023年   13篇
  2022年   25篇
  2021年   35篇
  2020年   26篇
  2019年   26篇
  2018年   39篇
  2017年   35篇
  2016年   28篇
  2015年   22篇
  2014年   33篇
  2013年   38篇
  2012年   52篇
  2011年   67篇
  2010年   33篇
  2009年   29篇
  2008年   54篇
  2007年   50篇
  2006年   47篇
  2005年   34篇
  2004年   26篇
  2003年   30篇
  2002年   18篇
  2001年   17篇
  2000年   11篇
  1999年   5篇
  1998年   3篇
  1997年   5篇
  1996年   3篇
  1995年   2篇
  1993年   3篇
  1992年   6篇
  1991年   3篇
  1990年   6篇
  1989年   4篇
  1988年   2篇
  1987年   2篇
  1986年   6篇
  1985年   5篇
  1984年   8篇
  1983年   3篇
  1980年   3篇
  1979年   2篇
  1978年   5篇
  1977年   3篇
  1976年   3篇
  1974年   2篇
  1973年   3篇
  1972年   2篇
  1965年   2篇
排序方式: 共有889条查询结果,搜索用时 46 毫秒
101.
OBJECTIVES: To assess the relationships between current smoking status and psychosocial working conditions. METHODS: A cross-sectional population-based telephone survey was conducted (66% response rate, N = 1,101). Job stress was measured using the demand/control, effort/reward imbalance (ERI), and job pressure models. Multiple regression modelling was conducted for smoking status (current versus non-smokers, and a more restricted analysis of current versus former-smokers) and daily smoking intensity outcomes in relation to job stress measures, working hours, shift work, and other independent variables. RESULTS: After adjustment for age, education, martial status, and hostility, high job strain was positively associated with current smoking in men only. Employment in active jobs was associated with decreased odds of smoking among women only. High strain jobs were associated with decreased odds of current smoking compared to former smoking in women. In men, extreme and moderate job pressure were related to current smoking compared to current non-smoking, and moderate job pressure was associated with current smoking compared with former smokers. Other working conditions associated with smoking were excessive working hours in men and physical demand in women. Daily smoking intensity in current smokers was associated with high psychological demand and with ERI in women. CONCLUSIONS: These results suggest that job stress is related to smoking status at the population level, with different patterns in men and women.  相似文献   
102.
103.
INTRODUCTION: The quality of first-responder performance at the end of automated external defibrillator (AED) training may not predict the performance adequately during a real resuscitation attempt. METHODS: Between January and December 2000, we evaluated 67 resuscitation attempts in Amsterdam and surroundings, where police officers used an AED. We compared their performance with their assessment at the end of their ERC AED training course. One of the main goals of training was to deliver a shock within 90 s after switching the power on in the AED. RESULTS: We analysed 127 police officers working in 67 police-teams. The police officers had a mean age of 35 years (range 23-54 years), 73% was male. The interval between AED training and the first resuscitation attempt was a median of 4 months (range 1-13). 78% percent of the 67 teams consisted of two police officers who both were qualified as "competent" after the initial training. Successful completion of the course correlated well with good performance during a resuscitation attempt (p = 0.009). When measured switching the power on in the AED, 92% of the victims received a shock within 90 s. CONCLUSIONS: Successful training correlates well with successful performance in the field. Competence of a team may be better than competence of two separate individuals.  相似文献   
104.
A short and effective training programme is an essential prerequisite for the use of automated external defibrillators (AED) by EMS providers and first responders. We evaluated a 3-h AED course based on the ERC requirements. METHODS: As part of a study evaluating the effectiveness of AEDs used by first responders (ARREST 4), we trained all police officers in the region of Amsterdam, the Netherlands. By means of a Basic Life Support (BLS) assessment at the beginning of the course and at the end, we evaluated whether BLS can be improved in a 3-h AED course. Through a combined BLS and AED assessment at the end of the course, we evaluated whether AED skills can be acquired sufficiently. BLS skills were measured with the Laerdal SkillMeter in evaluation mode. AED skills were assessed using 13 criteria. By means of logistic regression, we analysed the influence of student characteristics, such as age, gender, previous training, resuscitation experience and motivation for BLS and AED on BLS and AED skills acquisition. RESULTS: Between September 1999 and June 2000, 823 police officers were trained (76% male, mean age 36 (S.D. 9) years). BLS improved significantly (P < 0.001) in all criteria, except for hypoventilation (P < 0.001). After training, 89% of the students were able to use an AED safely and effectively. Self-confidence and motivation improved from 12 and 73% to 99 and 94% over the course (P < 0.001). Independent student characteristics influencing the success of the AED course were: previous BLS training, motivation before the course for an AED, and resuscitation experience that dated back for more than 12 months. CONCLUSION: The majority of police officers can be trained to use an AED safely and effectively within a 3-h AED course. During this course, they also improve on their BLS skills. Successful completion of the course depends in part on the student characteristics.  相似文献   
105.
INTRODUCTION: Recently, a method to analyse dried whole blood spots to diagnose Fabry disease (deficiency of the lysosomal enzyme alpha-Gal A) was described. However given its X-linked inheritance female Fabry patients can exhibit normal alpha-Gal A activities. This could lead to underestimation in screening females for Fabry disease using this method. METHODS: alpha-Gal A activity was measured in dried whole blood spots of 21 females with documented Fabry disease. RESULTS: Only 13/21 (67%) had reduced alpha-Gal A activities, concluding that one-third of female carriers would not be identified during screening. Additional determination of alphaGlucosidase activity (alphaGlu) and the construction of an alphaGal/alphaGlu ratio did not increase sensitivity of the assay. CONCLUSION: Assays using alpha-Gal activity for determination of Fabry disease in females have a high false-negative value. Screening for alpha-Gal A deficiency by means of whole blood spots should not be performed in a females.  相似文献   
106.
Two recurrent translocations have been associated with mucosa-associated lymphoid tissue (MALT)-type lymphoma, t(11;18)(q21;q21) and t(1;14)(p22;q32). The first, t(11;18)(q21;q21), results in the fusion protein API2-MLT (API2-MALT1). Through t(1;14)(p22;q32), the BCL10 gene is entirely transferred to the IgH gene, resulting in its overexpression. Wild-type BCL10 is implicated in apoptosis, and it has been suggested that mutated forms gain oncogenic activity. The occurrence of genomic BCL10 mutations in 35 gastric MALT-type lymphomas with or without t(11;18)(q21;q21) (10 and 25 cases, respectively) was investigated. DNA extracted from either whole tissue sections or microdissected clusters of tumor cells was used. Five polymerase chain reactions amplifying the coding exons were performed and were followed by direct sequencing of the products. Twenty differences with the published BCL10 sequence, all single nucleotide substitutions, were detected in 16 cases. Of these, 12 represented known polymorphisms, either at codon 8, 213, or 5. Of the remaining 8 substitutions, 2 were silent and 6 resulted in amino acid substitutions. Mutation analysis results were correlated with the BCL10 expression pattern. Aberrant nuclear BCL10 expression was detected in 14 cases. No association could be demonstrated between the latter and the presence of BCL10 mutations. In contrast, all 10 cases carrying t(11;18)(q21;q21) showed nuclear expression, whereas this staining pattern was absent in 21 of 25 cases without t(11;18)(q21;q21). These results demonstrate that BCL10 mutations are rare in gastric MALT-type lymphoma and are not related to the aberrant nuclear expression of BCL10. In contrast, they indicate that the presence of the API2-MLT fusion protein is associated with aberrant nuclear BCL10 expression.  相似文献   
107.
108.
IntroductionIntensive Care Units (ICUs) provide life-supporting treatment; however, resources are limited, so demand may exceed supply in the event of pandemics, environmental disasters, or in the context of an aging population. We hypothesized that comprehensive national data on ICU resources would permit a better understanding of regional differences in system capacity.MethodsAfter the 2009–2010 Influenza A (H1N1) pandemic, the Canadian Critical Care Trials Group surveyed all acute care hospitals in Canada to assess ICU capacity. Using a structured survey tool administered to physicians, respiratory therapists and nurses, we determined the number of ICU beds, ventilators, and the ability to provide specialized support for respiratory failure.ResultsWe identified 286 hospitals with 3170 ICU beds and 4982 mechanical ventilators for critically ill patients. Twenty-two hospitals had an ICU that routinely cared for children; 15 had dedicated pediatric ICUs. Per 100,000 population, there was substantial variability in provincial capacity, with a mean of 0.9 hospitals with ICUs (provincial range 0.4-2.8), 10 ICU beds capable of providing mechanical ventilation (provincial range 6–19), and 15 invasive mechanical ventilators (provincial range 10–24). There was only moderate correlation between ventilation capacity and population size (coefficient of determination (R2) = 0.771).ConclusionICU resources vary widely across Canadian provinces, and during times of increased demand, may result in geographic differences in the ability to care for critically ill patients. These results highlight the need to evolve inter-jurisdictional resource sharing during periods of substantial increase in demand, and provide background data for the development of appropriate critical care capacity benchmarks.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0852-6) contains supplementary material, which is available to authorized users.  相似文献   
109.
110.
Single functional group modifications of glucocorticoid steroids have been performed in an effort to obtain antiglucocorticoids with high affinity and specificity for glucocorticoid receptors. This approach tests the hypothesis that the structural determinants of biological activity and receptor binding are independent so that modification of more potent glucocorticoids could yield more potent antiglucocorticoids . In this study, a new functional group capable of conferring antiglucocorticoid activity has been identified, i.e. the spiro C-17 oxetan -3'-one group. Using three glucocorticoids of greatly different potency ( deacylcortivazol greater than dexamethasone greater than cortisol), we examined the effects of incorporation of the oxetanone group and the previously described, alkylating C-21 mesylate group on steroid affinity for receptors and biological activity. In both series of modified steroids, the receptor affinity of the derivatives paralleled that of the parent steroids. The biological activities of the dexamethasone and cortisol derivatives were predominantly or totally antagonistic, while both deacylcortivazol derivatives were full agonists. We conclude that antiglucocorticoid activity can arise from the incorporation of a single functional group into glucocorticoid steroid structures, but that the expression of agonist vs. antagonist activity is determined by a balance of structural group determinants which are not restricted to a common region of the steroid. Within a given class of derivatives, receptor affinity correlated with the amount of agonist activity. The structure-activity relationships for dexamethasone oxetanone and deacylcortivazol mesylate were studied in detail. Dexamethasone oxetanone is a potent antiglucocorticoid in HTC cells. [3H]Dexamethasone oxetanone binds to cell-free glucocorticoid receptors with a Kd of 3.2 X 10(-8) M. No specific antiglucocorticoid binder was detected. Direct binding experiments with [3H]dexamethasone oxetanone as well as indirect studies of the kinetics of cell-free competition of [3H]dexamethasone binding demonstrated that dexamethasone oxetanone binds to receptors faster (by about a factor of 2) and dissociates from receptors much faster than does dexamethasone. Deacylcortivazol mesylate was a more potent agonist and binder to receptors than dexamethasone, but displayed no irreversible interactions with HTC cell receptors under those conditions that afforded a covalent receptor-steroid complex with the closely related dexamethasone mesylate.(ABSTRACT TRUNCATED AT 400 WORDS)  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