首页 | 官方网站   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   2434篇
  免费   120篇
  国内免费   16篇
医药卫生   2570篇
  2023年   20篇
  2022年   20篇
  2021年   76篇
  2020年   56篇
  2019年   69篇
  2018年   70篇
  2017年   54篇
  2016年   64篇
  2015年   48篇
  2014年   62篇
  2013年   134篇
  2012年   189篇
  2011年   153篇
  2010年   74篇
  2009年   108篇
  2008年   166篇
  2007年   153篇
  2006年   149篇
  2005年   137篇
  2004年   136篇
  2003年   131篇
  2002年   103篇
  2001年   23篇
  2000年   19篇
  1999年   27篇
  1998年   19篇
  1997年   32篇
  1996年   12篇
  1995年   18篇
  1994年   20篇
  1993年   19篇
  1992年   7篇
  1991年   10篇
  1990年   14篇
  1989年   13篇
  1988年   9篇
  1986年   9篇
  1985年   11篇
  1984年   10篇
  1983年   12篇
  1982年   16篇
  1981年   13篇
  1980年   8篇
  1979年   11篇
  1978年   8篇
  1977年   6篇
  1976年   5篇
  1973年   7篇
  1972年   7篇
  1971年   5篇
排序方式: 共有2570条查询结果,搜索用时 361 毫秒
51.
OBJECTIVES: The effects of long-term cardiac resynchronization therapy (CRT) on left ventricular (LV) energetics and metabolic reserve were evaluated. BACKGROUND: Cardiac resynchronization therapy is a new therapy for patients with drug-refractory severe heart failure (HF). METHODS: Ten patients with idiopathic dilated cardiomyopathy who had undergone implantation of biventricular pacemaker 8 +/- 5 months earlier were studied during two conditions: CRT switched on, and after CRT was switched off for 24 h. Left ventricular function was measured using echocardiography and oxidative metabolism using [(11)C]acetate positron emission tomography. Both measurements were performed at rest and during dobutamine-induced stress (5 microg/kg/min). Basal- and adenosine-stimulated (140 microg/kg/min) myocardial blood flow were quantitated using [(15)O]water. RESULTS: During CRT off, LV stroke volume was significantly reduced at rest (72 +/- 18 ml vs. 63 +/- 15 ml, p < 0.05), but LV oxidative metabolism (K(mono)) remained unchanged (0.046 +/- 0.008 vs. 0.054 +/- 0.016 min(-1)) leading to a significant deterioration of myocardial efficiency of forward work (from 48.2 +/- 16.7 to 36.6 +/- 11.7 mm Hg.l/g, p < 0.05). During dobutamine-induced stress, stroke volume and K(mono) values were not different whether CRT was on or off. However, myocardial efficiency (56.1 +/- 16.1 vs. 49.8 +/- 18.0 mm Hg.ml.g(-1).min(-1), p = 0.099) and metabolic reserve, the response of K(mono) to dobutamine (0.023 +/- 0.014 vs. 0.013 +/- 0.014 min(-1), p = 0.09), tended to reduce when CRT was switched off. Cardiac resynchronization therapy had no effects on myocardial perfusion. Natriuretic peptides increased significantly during CRT-off period. CONCLUSIONS: Long-term CRT has beneficial effects on LV function and myocardial efficiency at rest in patients with HF. These effects are not associated with changes in myocardial perfusion or oxygen consumption. During dobutamine-induced stress, CRT does not affect functional parameters, but myocardial efficiency and metabolic reserve may be increased.  相似文献   
52.
53.
BackgroundThe data on acute kidney injury (AKI) in patients without chronic kidney disease (CKD) after transcatheter aortic valve replacement (TAVR) are limited. The study sought to compare the incidence of AKI and its impact on 5-year mortality after TAVR and surgical aortic valve replacement (SAVR) in patients without CKD.MethodsThis registry included data from 6463 consecutive patients who underwent TAVR or SAVR. CKD was defined as estimated glomerular filtration rate <60 mL/min/1.73 m2. AKI was defined according to the Kidney Disease Improving Global Outcomes criteria. For sensitivity analysis, propensity-score matching between TAVR and SAVR was performed.ResultsThe study included 4555 consecutive patients (TAVR, n = 1215 and SAVR, n = 3340) without CKD. Propensity-score matching identified 542 pairs. Patients who underwent TAVR had a significantly lower incidence of AKI in comparison to those who underwent SAVR (unmatched 4.7% vs 16.4%, P < 0.001, multivariable analysis: odds ratio, 0.29, 95% confidence interval [CI], 0.20-0.41; matched 5.9% vs 19.0%, P < 0.001). Patients with AKI had significantly increased 5-year mortality compared with those without AKI (unmatched 36.0% vs 19.1%, log-rank P < 0.001; matched 36.3% vs 24.0%, log-rank P < 0.001). The adjusted hazard ratios for 5-year mortality were 1.58 (95% CI, 1.20-2.08) for AKI grade 1, 3.27 (95% CI, 2.09-5.06) for grade 2, and 4.82 (95% CI, 2.93-8.04) for grade 3.ConclusionsTAVR in patients without CKD was associated with a significantly less frequent incidence of AKI compared with SAVR. AKI significantly increased the risk of 5-year mortality after either TAVR or SAVR, and increasing severity of AKI was incrementally associated with 5-year mortality.  相似文献   
54.
BACKGROUND AND AIM: asymptomatic relatives of patients with familial dilated cardiomyopathy who have left ventricular enlargement [LVE] are at risk for progression to dilated cardiomyopathy. A novel index of the fractal correlation properties of heart rate variability (HRV), the short-term scaling component (proportional, variant(1)) in detrended fluctuation analysis, is a promising prognostic tool in left ventricular dysfunction. The aim of this study was to compare values of proportional, variant(1) and conventional HRV indices in LVE relatives with dilated cardiomyopathy patients and normal controls. METHODS: time-domain and spectral HRV measures, and the short-term scaling component ( proportional, variant(1)) were assessed from 24-h Holter recordings from 22 LVE relatives (left ventricular end-diastolic dimension >112% predicted, normal fractional shortening), 24 dilated cardiomyopathy patients and 14 controls. RESULTS: the time domain index SDNN was lower in dilated cardiomyopathy patients [101.8(+/-44.0)] than in LVE relatives [161.7(+/-53.9)] or controls [152.9(+/-51.4)], P=0.01. Similarly, triangular index and spectral measures were reduced in dilated cardiomyopathy patients but not in LVE relatives or controls. In contrast, the short term scaling component ( proportional, variant(1)) in detrended fluctuation analysis was reduced in both dilated cardiomyopathy patients [1.06(+/-0.33)] and in LVE relatives [1.15 (+/-0.20)], compared with controls [1.32(+/-0.16)], P=0.01. Among DCM patients the short-term scaling component ( proportional, variant(1)) was significantly associated with echocardiographic deterioration during follow-up (3.7+/-2.1 year) (P=0.004). CONCLUSION: the short-term scaling component ( proportional, variant(1)) is reduced in asymptomatic relatives of dilated cardiomyopathy patients who have LVE.  相似文献   
55.
56.
People live longer than ever before, and the rapidly growing population of the oldest-old are increasingly frequent users of health care services. To determine the extent and causes of hospital care in the population aged 90, we examined the hospital discharge registers for the annual cohorts of Tampere residents born in 1907-1910 at age 90. The basic population consisted of 1077 people, 20.6% of who were men and 79.4% women. Close on one-fifth or 18.7% of this group died during the year under review. During this year, 43.2% of men and 50.3% of women had been admitted to hospital. Men spent significantly fewer days in hospital than women: the mean length of stay for men was 19 days, for women 46 days. Of the 90-year olds, 6.7% were permanently staying in hospitals. The most common diagnoses at discharge were cardiovascular diseases, infections, psychiatric diseases including dementia, and trauma. Of those who had been admitted to hospital once or more within the year, 31.7% died during the follow-up time, while the figure for those not admitted was only 6.2%. People aged 90 are an important group of hospital users. In the future, hospitals need to be prepared to provide adequate care for the most common diseases affecting the growing population of the oldest-old.  相似文献   
57.
Frequency of hereditary nonpolyposis colorectal cancer   总被引:10,自引:0,他引:10  
PURPOSE: Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant cancer syndrome characterized by early onset of colorectal carcinomas (CRC). Recently, two HNPCC genes have been mapped and cloned, one in the short arm of chromosome 2 and another in the short arm of chromosome 3. There has been a major controversy about the frequency of HNPCC. The few estimates available have been based on series selected by age or series representing local area. The purpose of the present study was to design a nonselected, prospective, multicenter study, taking into account the family background and other risk factors of CRC. METHODS: The proportion of HNPCC of all (N=406) CRC cases was evaluated in a prospective multicenter study. Family history and other risk factors were investigated over a 12-month period for all new CRC patients in ten hospitals. These cases constituted 23 percent of all CRCs diagnosed in Finland during the study period. RESULTS: Three (0.7 percent) cases of verified and seven (1.7 percent) cases of suspected HNPCC were identified, following the evaluation of all families with features indicative of susceptibility to cancer. The proportion of identifiable risk factors of CRC was 5.8–7.5 percent (HNPCC, 0.7-2.4 percent; previous CRC, 3.4 percent; ulcerative colitis, 1.0 percent; familial adenomatous polyposis coli, 0.7 percent). CONCLUSION. This prospective multicenter study revealed that the frequency of hereditary colorectal cancer is lower than in some previous studies, when diagnosis is based on extensive pedigree analysis. This result with recent findings of common ancestral founding mutation in Finnish HNPCC families indicates that there may be geographic differences in the occurrence of HNPCC. However, this does not change the fact that identification of HNPCC—perhaps one of the most common inherited diseases identified in humans—has become a question of vital importance now when diagnosis of the syndrome and largescale screening of gene carriers using specific tests are on the horizon.Supported by grants from the Finnish Cancer Society, the Finnish Foundation for Gastroenterological Research, the Sigrid Juselius Foundation, and the Academy of Finland, Helsinki, Finland.  相似文献   
58.
BACKGROUND AND AIMS: In a few, earlier, uncontrolled trials, alleviation of chronic pain has been documented by vitamin D supplementation. This randomized double-blind placebo controlled trial addressed the association between pain and vitamin D deficiency and the effects of vitamin D supplementation on pain in institutionalized aged patients. METHODS: 216 long-term care patients were enrolled in Helsinki, Finland. Pain was assessed by three tools: Resident Assessment Instrument (RAI), Discomfort Behavior Scale, and Pain Assessment in Advanced Dementia Scale. Scores for Cognitive Performance Scale (CPS) and other clinical assessments were also collected from the RAI-database. Levels of 25-hydroxyvitamin D (25- OHD) and parathyroid hormone were also determined. Patients in pain (n=202) were randomized into three treatment groups, each receiving 0, 400, or 1200 IU cholecalciferol per day, respectively. Assessments were repeated after six-month vitamin D supplementation. RESULTS: Patients were aged (84.5+/-7.5 yrs), demented (CPS= 4.9+/-1.4, range 1-6), and chronically bedridden. Pain was present in 38.4% to 83.8% of patients depending on assessment tool. Low 25-OHD levels (<50 nmol/L) were very common (98.1%). However, vitamin D deficiency was not associated with pain or pain behavior. The supplementation resulted in a marked increase in 25-OHD levels. However, neither prevalence of painlessness nor pain scores changed significantly after vitamin D supplementation. CONCLUSIONS: We were not able either to show an association between vitamin D deficiency and pain or to observe alleviation of pain by vitamin D supplementation. The independent role of vitamin D in the etiology of pain remains controversial.  相似文献   
59.
60.
During prolonged viewing of ambiguous stimuli, such as Necker cubes, sudden perceptual reversals occur from one perceptual interpretation to another. The role of attention in such reversals is not clear. We tested whether perceptual reversals depend on attentional resources by manipulating perceptual load and recording event‐related potentials (ERPs) during intermittent presentation of Necker stimuli. The results did not reveal any influence for perceptual load on the frequency of reversals. The ERPs showed that perceptual load influenced electrophysiological activity over parieto‐central areas in the P1 time window (110–140 ms), but load did not modify the early enhancements of positivity (30–140 ms), which correlated with perceptual reversals at occipito‐temporal sites. We conclude that disambiguation of ambiguous figures is based on early mechanisms that can work efficiently with only a minimal amount of attentional resources.  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-23

京公网安备 11010802026262号