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   1132篇
  免费   67篇
  国内免费   1篇
耳鼻咽喉   11篇
儿科学   6篇
妇产科学   25篇
基础医学   102篇
口腔科学   98篇
临床医学   71篇
内科学   149篇
皮肤病学   3篇
神经病学   63篇
特种医学   22篇
外科学   55篇
综合类   2篇
预防医学   183篇
眼科学   6篇
药学   95篇
肿瘤学   309篇
  2023年   7篇
  2022年   4篇
  2021年   12篇
  2020年   20篇
  2019年   19篇
  2018年   32篇
  2017年   39篇
  2016年   25篇
  2015年   30篇
  2014年   33篇
  2013年   31篇
  2012年   82篇
  2011年   88篇
  2010年   32篇
  2009年   33篇
  2008年   66篇
  2007年   67篇
  2006年   62篇
  2005年   63篇
  2004年   51篇
  2003年   38篇
  2002年   39篇
  2001年   34篇
  2000年   29篇
  1999年   20篇
  1998年   8篇
  1997年   7篇
  1996年   5篇
  1995年   5篇
  1994年   4篇
  1992年   20篇
  1991年   9篇
  1990年   11篇
  1989年   22篇
  1988年   21篇
  1987年   10篇
  1986年   13篇
  1985年   20篇
  1984年   14篇
  1982年   3篇
  1981年   4篇
  1980年   5篇
  1979年   11篇
  1978年   6篇
  1977年   4篇
  1976年   8篇
  1975年   7篇
  1974年   9篇
  1969年   2篇
  1968年   4篇
排序方式: 共有1200条查询结果,搜索用时 15 毫秒
91.
OBJECTIVE: to analyze the clinical features and associated morbidity in a group of patients with vascular dementia (VD). METHODS: we retrospectively evaluated 25 patients with diagnosis of VD, based on the State of California Alzheimers Disease Diagnostic and Treatment Centers (ADDTC) criteria. Clinical and neuroimaging data and laboratory test results were obtained for the characterization of the sample. RESULTS: the mean age was 68.7 +/- 14.6 years (64.0% men), with mean educational level of 5.2 +/- 4.4 years. Sudden onset of symptoms was observed in 48.0% of patients and stepwise deteriorating and fluctuating courses being observed in 4.0% and 16% respectively. Focal neurologic deficits were the first symptom in 48.0%, with focal deficits being observed in 80% on examination. The main morbidity were: hypertension (92.0%); hypercholesterolemia (64.0%); coronary heart disease (40.0%); smoking (40.0%); hypertriglyceridemia (36.0%); diabetes mellitus (32.0%); Chagas' disease (8.0%). CONCLUSIONS: we observed strong association between VD and hypertension and hypercholesterolemia. The observation of two patients presenting Chagas' disease suggests that this endemic condition may be considered a possible regional risk factor.  相似文献   
92.
93.
94.
This study evaluated recently suggested invasive and noninvasive parameters of myocardial reperfusion after acute myocardial infarction (AMI), assessing their predictive value for left ventricular function 4 weeks after AMI and reperfusion defined by myocardial contrast echocardiography (MCE). In 38 patients, angiographic myocardial blush grade, corrected Thrombolysis In Myocardial Infarction frame count, ST-segment elevation index, and coronary flow reserve (n = 25) were determined immediately after primary percutaneous transluminal coronary angioplasty (PTCA) for first AMI, and intravenous MCE was determined before, and at 1 and 24 hours after PTCA to evaluate myocardial reperfusion. Results were related to global wall motion index (GWMI) at 4 weeks. MCE 1 hour after PTCA showed good correlation with GWMI at 4 weeks (r = 0.684, p <0.001) and was in an analysis of variance the best parameter to predict GWMI 4 weeks after AMI. The ST-segment elevation index was close in its predictive value. Considering only invasive parameters of reperfusion myocardial blush grade was the best predictor of GWMI at 4 weeks (R2 = 0.3107, p <0.001). A MCE perfusion defect size at 24 hours of ≥50% of the MCE perfusion defect size before PTCA was used to define myocardial nonreperfusion. In a multivariate analysis, low myocardial blush grade class was the best predictor of nonreperfusion defined by MCE. Thus, intravenous MCE allows better prediction of left ventricular function 4 weeks after AMI than other evaluated parameters of myocardial reperfusion. Myocardial blush grade is the best predictor of nonreperfusion defined by MCE and is the invasive parameter with the greatest predictive value for left ventricular function after AMI. Coronary flow parameters are less predictive.  相似文献   
95.
Although neuroendocrine changes after induction of hypoglycemia, in patients with diabetes and healthy persons, are thoroughly investigated, cognitive adaptation processes are still insufficiently understood. Changes in cognitive functions are mainly investigated by psychometric tests, which represent a summation of different cognitive processes. We aimed at dissecting cognitive adaptation into single components, i.e. stimulus selection, response choice, and reaction speed during a hyperinsulinemic hypoglycemic clamp in patients with type-1 diabetes and matched healthy controls. Using novel neurophysiological analyses, the event-related potentials of early stimulus selection (selection negativity) and response selection (lateralized readiness potential) were studied, in addition to reaction time (RT). A total of 12 diabetic patients and 12 normal volunteers were studied while receiving a hyperinsulinemic hypoglycemic clamp. RTs and the event-related potentials related to stimulus selection and response selection were significantly delayed during hypoglycemia in both groups, whereas early evoked potentials (P100) were unaltered. This suggests that hypoglycemia delays stimulus selection, with the consequence that also central and motor processing are delayed. In addition, patients with diabetes showed an earlier negative shift over the frontal cortex, which, when compared with the controls, reveals better adaptation to hypoglycemia in frontal cortical brain regions. After restoration of euglycemia stimulus selection, response selection and RT returned to baseline level in the type-1 group. In the control group, however, response selection and RTs were still delayed. This suggests that type-1 patients, possibly because of the past occurrence of hypoglycemic events, might be able to better cope with the hypoglycemic state than healthy volunteers who lack such a history. In summary, our data demonstrate, for the first time, that cognitive adaptation processes to an experimental hypoglycemic episode can clearly be dissected into their single components.  相似文献   
96.
Patients with sepsis in the ICU (intensive care unit) are characterized by skeletal muscle wasting. This leads to muscle dysfunction that also influences the respiratory capacity, resulting in prolonged mechanical ventilation. Catabolic conditions are associated with a general activation of the ubiquitin-proteasome pathway in skeletal muscle. The aim of the present study was to measure the proteasome proteolytic activity in both respiratory and leg muscles from ICU patients with sepsis and, in addition, to assess the variation of proteasome activity between individuals and between duplicate leg muscle biopsy specimens. When compared with a control group (n=10), patients with sepsis (n=10) had a 30% (P<0.05) and 45% (P<0.05) higher proteasome activity in the respiratory and leg muscles respectively. In a second experiment, ICU patients with sepsis (n=17) had a 55% (P<0.01) higher proteasome activity in the leg muscle compared with a control group (n=10). The inter-individual scatter of proteasome activity was larger between the patients with sepsis than the controls. We also observed a substantial intra-individual difference in activity between duplicate biopsies in several of the subjects. In conclusion, the proteolytic activity of the proteasome was higher in skeletal muscle from patients with sepsis and multiple organ failure compared with healthy controls. It was shown for the first time that respiratory and leg muscles were affected similarly. Furthermore, the variation in proteasome activity between individuals was more pronounced in the ICU patients for both muscle types, whereas the intra-individual variation between biopsies was similar for ICU patients and controls.  相似文献   
97.
This study, which is a part of the initiative 'Lifting The Burden: The Global Campaign to Reduce the Burden of Headache Worldwide', assesses and presents all existing evidence of the world prevalence and burden of headache disorders. Population-based studies applying International Headache Society criteria for migraine and tension-type headache, and also studies on headache in general and 'chronic daily headache', have been included. Globally, the percentages of the adult population with an active headache disorder are 46% for headache in general, 11% for migraine, 42% for tension-type headache and 3% for chronic daily headache. Our calculations indicate that the disability attributable to tension-type headache is larger worldwide than that due to migraine. On the World Health Organization's ranking of causes of disability, this would bring headache disorders into the 10 most disabling conditions for the two genders, and into the five most disabling for women.  相似文献   
98.
The HAM/TSP caused by HTLV-1 infection usually affects patients to disabling states, and sometimes can lead them to paraplegia presenting symptoms of depression and anxiety, impacting on quality of life.ObjectiveThe purpose of this study was to evaluate the frequency of depression and anxiety and its impact on quality of life in HTLV-1-infected TSP/HAM patients.Material and MethodsThis was a cross-sectional study including 67 asymptomatic (control group) and 63 with TSP/HAM subjects. The instruments used were a demographic questionnaire, scales for anxiety and depression diagnosis (BDI and BAI), questionnaire for the assessment of Quality of Life of the World Health Organization (WHOQOL-Brief) and neurological scale to measure the disability level (Osame's Disability Status Scale). All patients had HTLV-I diagnosis by serological and molecular approaches, monitored at Instituto de Infectologia Emílio Ribas from May 2008 to July 2009. Data were analyzed statistically by frequencies, the Mann-Whitney test and the Spearman correlation test. Data among groups were analyzed and correlated with functional and severity aspects.ResultsThe results showed that patients with HAM/TSP compared to asymptomatic carriers had higher rates of depression (p < 0.001) and anxiety (p < 0.001), and impairment on quality of life in the areas of: dissatisfaction with health (p < 0.001), physical (p < 0.001) and the environment (p = 0.003). The main factors that correlated with levels of depression and anxiety and the domains of the WHOQOL-brief were: education, family income and social class.ConclusionA well conducted evaluation and counseling may help in treatment, for a better quality of life of these patients.  相似文献   
99.
Epidemiological data show that reproductive and hormonal factors are involved in the etiology of endometrial cancer, but there is little data on the association with endogenous sex hormone levels. We analyzed the association between prediagnostic serum concentrations of sex steroids and endometrial cancer risk in the European Prospective Investigation into Cancer and Nutrition using a nested case-control design of 247 incident endometrial cancer cases and 481 controls, matched on center, menopausal status, age, variables relating to blood collection, and, for premenopausal women, phase of menstrual cycle. Using conditional regression analysis, endometrial cancer risk among postmenopausal women was positively associated with increasing levels of total testosterone, free testosterone, estrone, total estradiol, and free estradiol. The odds ratios (ORs) for the highest versus lowest tertile were 2.66 (95% confidence interval (CI) 1.50-4.72; P=0.002 for a continuous linear trend) for estrone, 2.07 (95% CI 1.20-3.60; P=0.001) for estradiol, and 1.66 (95% CI 0.98-2.82; P=0.001) for free estradiol. For total and free testosterone, ORs for the highest versus lowest tertile were 1.44 (95% CI 0.88-2.36; P=0.05) and 2.05 (95% CI 1.23-3.42; P=0.005) respectively. Androstenedione and dehydroepiandrosterone sulfate were not associated with risk. Sex hormone-binding globulin was significantly inversely associated with risk (OR for the highest versus lowest tertile was 0.57, 95% CI 0.34-0.95; P=0.004). In premenopausal women, serum sex hormone concentrations were not clearly associated with endometrial cancer risk, but numbers were too small to draw firm conclusions. In conclusion, relatively high blood concentrations of estrogens and free testosterone are associated with an increased endometrial cancer risk in postmenopausal women.  相似文献   
100.
Platelets Stored in a New-Generation Container   总被引:2,自引:0,他引:2  
Background and Objectives : In order to preserve platelet concentrates (PCs) with high yields, a new polyolefin platelet storage container (PL 2410, 1.3L, Baxter, La Châtre, France) with increased gas permeability in combination with a larger surface area has been developed. The storage capacity was studied with platelets in plasma and platelets additive solution. Materials and Methods : Platelet concentrate pools (PCs) of different yields suspended in either plasma (PCs-PL; n = 30) or PAS II (PCs-PAS; n = 37) were prepared. For preparation of PCs with a low, intermediate and high number of platelets 3, 5 and 6 buffy coat (BCs) were pooled with different volumes of plasma and 5 and 6 BCs were pooled with different volumes of PAS II, in order to obtain PCs of equal volumes comparable with routine conditions. All PCs were stored on a flatbed shaker at 22±2°C and evaluated on days 1, 2, 5 and 7 by determining platelet and white cell counts, pH (37°C), pO2, pCO2 and swirling score. Results : Platelet yields ranged from 1.5 up to 5.5 × 1011 platelets/U. On day 7 all PCs-PL (n = 4) with platelet yields above 4.5×1011 had a pH value below 6.8 (range 5.91–6.79). While 7 of 8 PCs-PAS units with platelet yields above 4.0×1011/U showed a pH value below 6.8 (range 6.31–6.70). Conclusion : During 7 days of storage in a new 1.3-liter platelet container, the pH was maintained above 6.8 in PCs in plasma with a yield between 1.5-and 4.5×1011/U; when PAS II was used, the maximum platelet yield allowed for comparable pH maintenance was somewhat lower (4.0x1011/U).  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