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   4054篇
  免费   342篇
  国内免费   28篇
耳鼻咽喉   28篇
儿科学   140篇
妇产科学   175篇
基础医学   543篇
口腔科学   196篇
临床医学   437篇
内科学   796篇
皮肤病学   192篇
神经病学   285篇
特种医学   95篇
外科学   357篇
综合类   64篇
一般理论   7篇
预防医学   344篇
眼科学   81篇
药学   331篇
中国医学   47篇
肿瘤学   306篇
  2024年   8篇
  2023年   95篇
  2022年   166篇
  2021年   311篇
  2020年   200篇
  2019年   303篇
  2018年   337篇
  2017年   211篇
  2016年   211篇
  2015年   214篇
  2014年   259篇
  2013年   285篇
  2012年   403篇
  2011年   368篇
  2010年   160篇
  2009年   126篇
  2008年   179篇
  2007年   154篇
  2006年   128篇
  2005年   89篇
  2004年   77篇
  2003年   52篇
  2002年   55篇
  2001年   5篇
  2000年   1篇
  1999年   8篇
  1998年   4篇
  1997年   3篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1993年   4篇
  1992年   1篇
  1989年   3篇
  1965年   1篇
排序方式: 共有4424条查询结果,搜索用时 889 毫秒
161.

Objectives

The purpose of our study was to assess the echocardiographic and angiographic parameters in patients with symptomatic heart failure (HF) and mild diastolic dysfunction (grade I).

Background

It remains uncertain why some patients with mild diastolic dysfunction exhibit HF symptoms and others are asymptomatic.

Methods

The study enrolled 80 hospitalized patients with impaired left ventricular (LV) relaxation. Patients were divided into two groups; one group had chronic functional class II to III dyspnea and the other group had no symptoms of HF. After admission, echocardiography and coronary angiography were performed for all patients and LV systolic and diastolic parameters were compared between the two groups.

Results

More patients in the asymptomatic group were hypertensive (p-value: 0.012). However, coronary artery disease was more prevalent in symptomatic patients (p-value: 0.022). The LV ejection fraction (EF) was significantly lower in symptomatic patients [median 54.33 %, 95 % confidence interval (53.76–54.87 %) in asymptomatic patients and median 49.43, 95 % confidence interval (47.23–50.91 %) in symptomatic patients, p-value <0.001]. Furthermore, the systolic LV internal dimension was significantly larger in this group (p-value: 0.037). The results of logistic regression identified that only the absolute level of the LVEF was the negative determinant of the occurrence of HF in patients with impaired LV relaxation.

Conclusion

Our study showed that LV systolic performance has an important role in occurrence of HF symptoms in patients with grade I diastolic dysfunction.
  相似文献   
162.
This study constitutes a first attempt to describe the genetic population structure and drug resistance of the tubercle bacilli circulating in Saudi Arabia. A total of 1,505 clinical isolates of M. tuberculosis, isolated between 2002 and 2005 from seven regions of Saudi Arabia, were studied. The sample studied showed a male-to-female sex ratio of 1.27, with half of the cases among foreign-born individuals and 47% within the 21- to 40-year-old age group; a total resistance rate of 19.7%; and multiple drug resistance of 4.5%. Upon spoligotyping, a total of 387 individual patterns were obtained (clustering rate, 86.4%; 182 clusters containing between 2 and 130 isolates per cluster). A total of 94% of the strains matched the spoligotype patterns in an international database. Nearly 81% of the isolates in this study belonged to established phylogeographic clades: Central Asian (CAS), 22.5%; ill-defined T clade, 19.5%; East African-Indian (EAI), 13.5%; Haarlem, 7.5%; Latin American-Mediterranean, 7.2%; Beijing, 4.4%; Manu, 2.7%; X, 0.9%; and Bovis, 0.9%. Two clonal complexes with unique spoligotyping signatures (octal codes 703777707770371 and 467777377413771) specific to Saudi Arabia were identified. These belonged to the CAS and EAI clades, respectively, as confirmed upon secondary typing using mycobacterial interspersed repetitive units (MIRUs). The results obtained underline the predominance of historic clones of principal genetic group 1, which are responsible for roughly 45% of all tuberculosis cases in Saudi Arabia. The high rate of clustering observed might be an indication of rapid ongoing transmission within certain communities and/or subpopulations in Saudi Arabia; nonetheless, spoligotyping is known to overestimate clustering, and only a systematic second-line typing, such as MIRUs, coupled with a better tuberculosis registry and epidemiological investigations would allow us to know the exact rate of ongoing transmission and associated risk factors in Saudi Arabia.  相似文献   
163.
OBJECTIVE: This study compares telephone consultations with the results of clinical examinations to assess the value and accuracy of telephone consultations for the future planning in a breast cancer clinic in Tehran, Iran. METHODS: In 2500 telephone calls, 800 Symptomatic patients were identified and asked to visit the center for the further investigations by the specialists. The agreement between two observers data were compared by the kappa statistic. RESULTS: Totally 174 patients complied with the recommendation and included in the study. The most common chief complaints of visitors were: breast mass (42%) and breast pain (35%). Kappa statistic showed a very good agreement (K=0.62, P<0.001) between consultants' diagnosis and the specialists findings. This agreement for breast cancer diagnosis, although lower, was also good (K=0.55, P<0.001). CONCLUSION: The study findings indicate that consultants may diagnose and manage some common conditions via telephone, usually following the established protocols. More studies are needed to determine the economic and logistic advantages of telephone consultations. PRACTICE IMPLICATIONS: By assessment of strength and weakness of this service, it is possible to develop an easy to use information system for women who need breast care.  相似文献   
164.
GABAergic intracortical inhibition (ICI) in human motor cortex (M1) assists fractionated activation of muscles, and it has been suggested that hemispheric differences in ICI may contribute to hand preference. Previous studies of this issue have all been conducted at rest, with conflicting results. Testing during voluntary activation may reveal functionally relevant differences. In normal subjects, we assessed (1) operation of ICI circuits during selective activation of an intrinsic hand muscle at different forces, and (2) whether this differs between right and left hemispheres. Surface EMG was recorded bilaterally from abductor pollicis brevis (APB), first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles in eleven right-handed subjects. A circular coil applied paired transcranial magnetic stimulation (TMS) with posteriorly directed current in the brain. Conditioning intensity was 0.8 × active threshold and interstimulus interval was 3 ms. TMS was applied to right or left M1 while subjects were at rest or performing isometric thumb abduction at different forces (0.5, 1, 2, 3, 5 and 10 N) with the contralateral hand. Conditioning TMS was less effective at suppressing the muscle evoked potential in APB during 2–10 N thumb abduction (P < 0.0001) versus rest, but not with lower target forces (0.5, 1 N). Conditioning TMS was less effective for FDI and ADM only during 10 N thumb abduction. We conclude that differential modulation of ICI in M1 during selective muscle activation is a function of target isometric force level. At low forces (<5% MVC), ICI is not modulated for the corticospinal neurons controlling the active or inactive muscles. There is a progressive reduction of ICI effects on corticospinal neurons at higher forces, which is largely restricted to corticospinal neurons controlling the muscle targeted for activation over the range of forces tested (up to ∼25% MVC). The pattern of ICI modulation with selective voluntary muscle contraction was similar in left and right hemispheres during this relatively simple static task. If hemispheric differences in operation of M1 ICI circuits contribute to hand preference, a more challenging finger movement protocol may be needed to demonstrate this asymmetry.  相似文献   
165.

Objective

Physicians often need uptodate, reliable and with easy access information for clinical decisions evidence based medicine (EBM) databases can be a suitable approach to meet this need. The aim of this study was to assess the knowledge, use and factors affecting the acceptance of EBM and its databases by Iranian medical residents using UTAUT model.

Method

The present research is an applied survey, the population of which consisted of 192 medical residents of Shahid Beheshti University of Medical Sciences (SBUMS) in Iran. A questionnaire was used for collecting data and SPSS software was used for data analysis.

Results

The results show that the total average score of assistants (range?=?1–5), 2.99 and 2.73 scores were respectively obtained for the awareness and use of EBM databases. The study of factors affecting the acceptance using UTAUT showed that item "performance expectancy" with an average of 3.02 is the most important factor in the acceptance of EBM databases by medical residents and items "effort expectancy", "facilitating conditions" and "social influence" are in their next ranks with an average score of 2.54, 2.45 and 2.14, respectively.

Conclusion

The findings of this study showed that the majority of medical residents do not have sufficient awareness and knowledge about concepts of EBM and still not comprehend the necessity of using EBM databases. Therefore, planning for accepting and teaching Evidence based medicine and databases is essential.  相似文献   
166.
Considering the importance of urease inhibitors in the treatment of ureolytic bacterial infections, in this work, the synthesis of novel, aryl urea‐triazole‐based derivatives as effective urease inhibitors is described. Dichloro‐substituted derivative 4o , with IC50 = 22.81 ± 0.05 μM, is found to be the most potent urease inhibitor, determined by Berthelot colorimetric assay. Docking studies were also carried out for compound 4o to confirm the effective interactions with the urease active site.
  相似文献   
167.
168.

Objectives

Dysphagia is a frequent finding in nursing home residents. The aim of this study is to evaluate the association of dysphagia and mortality in nursing home residents and identify further risk factors for mortality in residents with dysphagia.

Design

One-day, annually repeated cross-sectional study, evaluating the nutritional situation of nursing home residents with 6-month mortality as outcome.

Setting

191 nursing homes from 14 countries in Europe and the United States participating in the nutritionDay study between 2007 and 2012.

Participants

Data of all nursing home residents in the nutritionDay study aged 65 years or older with available information about dysphagia and outcome were analyzed.

Measurements

Residents’ characteristics and mortality rate were calculated by group comparison, and mortality risk was calculated by multivariate regression analysis with adjustment for potential confounding factors.

Results

10,185 residents (78% female) with a mean age of 85 ± 8.1 years were included in the analysis. Dysphagia was reported in 15.4% of residents. The 6-month mortality of residents with dysphagia was significantly higher than of those without dysphagia (24.7% vs 11.9%; P < .001). The multivariate regression analysis revealed dysphagia [odds ratio (OR) 1.44, 95% confidence interval (CI) 1.24-1.68, P < .001] along with body mass index <20 (OR 1.78, 95% CI 1.55-2.03, P < .001) and weight loss >5 kg (OR 1.61, 95% CI 1.37-1.88, P < .001) as independent and significant risk factors for mortality. Because of significant interaction, a disproportionately high mortality of 38.9% was found in residents with dysphagia accompanied by previous weight loss >5 kg (OR for interaction 1.44; 95% CI 1.03-2.01; P = .032). Tube feeding was reported in 14.6% of residents with dysphagia. The mortality rate of dysphagic residents receiving tube feeding vs those who were not was not significantly different (21.4% vs 25.3%; P = .244).

Conclusion

In this nutritionDay study, dysphagia was identified as an independent risk factor for mortality in nursing home residents. Residents with dysphagia accompanied by weight loss are at a particularly high risk of mortality and should therefore receive special attention.  相似文献   
169.
Objective: Alternative medicine and herbal drugs have been taken into account for managing cardiovascular risk factors. Sumac (Rhus coriaria L.) is rich in biologically active ingredients known to improve cardiovascular health. We investigated the effect of sumac on systolic (SBP) and diastolic (DBP) blood pressure, flow-mediated dilation (FMD), body mass index (BMI), and serum concentrations of lipids and fasting blood sugar (FBS) in participants with hyperlipidemia in a triple-blind randomized placebo- controlled crossover trial.

Methods: Thirty adults with dyslipidemia (mild to moderate elevation of plasma total cholesterol and/or triglycerides [TG; total cholesterol ≥ 6.0 mmol/L or TG ≥ 1.7 mmol/L and TG ≤ 5.0 mmol/L]) were assigned randomly to a sumac or a placebo group. Participants in the sumac group received sumac capsules (500 mg/twice daily) for the first 4 weeks, followed by 2 weeks’ washout period; the patients were then switched to a 4-week interval and received placebo for 4 weeks in the second period. The placebo group received these treatments in reverse order. FMD, BMI, SBP, DBP, lipids, and FBS were measured at baseline and after each period.

Results: Differences between placebo group and sumac group (placebo-sumac) were significantly decreased for BMI (0.21 ± 0.075 kg/m2), SBP (1.87 ± 0.83 mm Hg), DBP (1.32 ± 0.46 mm Hg), and total cholesterol (14.42 ± 4.95 mmol/L) and significantly increased for FMD (?0.23% ± 0.065%). Plasma level of TG did not change significantly across the treatment.

Conclusion: Sumac consumption may decrease cardiovascular risk factors in persons with mild to moderate hyperlipidemia.  相似文献   
170.
AIM: Dental impressions are potential sources of bacterial contamination which could eventually lead to transmissible infectious diseases through the blood or saliva. Sodium hypochlorite is an effective disinfectant recommended by the American Dental Association (ADA) in a 1:10 dilution for a ten minute immersion to disinfect irreversible hydrocolloid impressions. As the ADA protocol is sometimes neglected in busy practice settings, this pilot study was designed to determine an efficient and effective protocol for disinfection of irreversible hydrocolloid impressions. METHODS AND MATERIALS: Various concentrations of sodium hypochlorite and disinfection times were challenged against irreversible hydrocolloid impressions contaminated with six Gram-positive and Gram-negative bacteria. RESULTS: A two minute immersion time in a 0.6% solution of sodium hypochlorite protocol was found to prevent bacterial growth on the impressions. CONCLUSION: Disinfection of irreversible hydrocolloid impressions in a 0.6% solution of sodium hypochlorite for two minutes was as effective as the ADA's protocol of using a 0.5% sodium hypochlorite solution for ten minutes to destroy the test bacteria.  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