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   4815篇
  免费   229篇
  国内免费   67篇
耳鼻咽喉   32篇
儿科学   164篇
妇产科学   64篇
基础医学   596篇
口腔科学   32篇
临床医学   421篇
内科学   1326篇
皮肤病学   58篇
神经病学   392篇
特种医学   95篇
外国民族医学   2篇
外科学   913篇
综合类   12篇
预防医学   176篇
眼科学   220篇
药学   270篇
中国医学   3篇
肿瘤学   335篇
  2022年   32篇
  2021年   74篇
  2020年   35篇
  2019年   58篇
  2018年   100篇
  2017年   55篇
  2016年   51篇
  2015年   55篇
  2014年   92篇
  2013年   171篇
  2012年   257篇
  2011年   267篇
  2010年   172篇
  2009年   170篇
  2008年   287篇
  2007年   366篇
  2006年   315篇
  2005年   301篇
  2004年   282篇
  2003年   253篇
  2002年   255篇
  2001年   118篇
  2000年   128篇
  1999年   109篇
  1998年   74篇
  1997年   61篇
  1996年   44篇
  1995年   35篇
  1994年   40篇
  1993年   26篇
  1992年   68篇
  1991年   56篇
  1990年   62篇
  1989年   64篇
  1988年   38篇
  1987年   53篇
  1986年   49篇
  1985年   41篇
  1984年   31篇
  1983年   28篇
  1981年   21篇
  1979年   25篇
  1975年   27篇
  1974年   23篇
  1972年   16篇
  1970年   21篇
  1969年   17篇
  1967年   16篇
  1966年   18篇
  1965年   21篇
排序方式: 共有5111条查询结果,搜索用时 754 毫秒
101.
INTRODUCTION: Before the HIV infection era, plasmocyte tumor rarely occurred in patients younger than 40 years of age. Less frequent than lymphomas, the incidence of these blood diseases has however substantially increased in HIV-infected patients. In these patients, in addition to onset at earlier age, their clinical presentation is quite different and extramedullary plasmocytomas in unexpected locations are more common. EXEGESIS: We report the case of a 29-year-old HIV-infected female patient in whom were diagnosed occipital, parotidal, sphenoidal, epidural, and uterine plasmocytomas for which chemotherapy and subsequent radiotherapy were successful. The increase in the incidence of plasmocyte tumors in HIV-infected patients might be facilitated by Epstein Barr Virus (EBV) co-infection, HIV-related chronic antigenic stimulation, and secretion of interleukin 6 by infected lymphocytes. CONCLUSION: Plasmocyte tumors belong to neoplasia whose incidence is increased in HIV infection. Their currently poor diagnosis should be improved by highly active antiretroviral therapies allowing enhanced chemotherapy with possibility of autograft.  相似文献   
102.
Multiple mechanisms exist by which tumour cells can escape CD95-mediated apoptosis. Previous studies by our laboratory have shown that primary B cells from non-Hodgkin's Lymphoma (B-NHL) were resistant to CD95-induced cell death. In the current study, we have analysed the mechanisms underlying CD95 resistance in primary human lymphoma B cells. We report that FADD (FAS-associated death domain protein) and caspase-8 were constitutively expressed in lymphoma B cells and that the CD95 pathway was blocked upstream to caspase-8 activation. However, caspase-8 was processed and functional after treatment with staurosporine (STS). We found that the expression levels of FLICE (FADD-like interleukin-1 beta-converting enzyme)-Inhibitory Protein (c-FLIP) and Bcl-2-related proteins were heterogeneous in B-NHL cells and were not related to CD95 resistance. Finally, we report the absence of a CD95-induced signalling complex [death-inducing signalling complex (DISC)] in lymphoma B cells, with no FADD and caspase-8 recruitment to CD95 receptor. In contrast, DISC formation was observed in CD95-resistant non-tumoural (NT) B cells. Therefore, we propose that the absence of DISC formation in primary lymphoma B cells may contribute to protect these cells from CD95-induced apoptosis.  相似文献   
103.
Doppler echocardiographic examinations were performed in 146 patients with normal and 42 patients with pathological (31 regurgitations and 11 obstructions) mitral valve prostheses confirmed by catheterisation and/or surgery. The maximum and mean transprosthetic gradients and pressure half times (PHT) were calculated from continuous wave Doppler recordings and regurgitant signals were searched for by continuous and pulsed wave Doppler. In the group of normal mitral valve prostheses, the mean gradients and PHT were very variable even within the subgroups of the same type and size of prosthesis. The best haemodynamic profile was observed with the St Jude prosthesis (mean gradient = 5 +/- 2 mmHg, PHT = 90 +/- 22 ms, p less than 0.05 vs other prostheses). Minimal mitral regurgitation was detected in 12 per cent of bioprostheses and 20 per cent of mechanical prostheses. No correlations were found between the mean pressure gradient or PHT and the size of the prostheses. Regular Doppler echocardiographic follow-up over 2.4 years was obtained in 25 patients and showed a remarkable stability of the Doppler parameters in 17 patients whereas prosthetic valve dysfunction was diagnosed in the other 8 cases. In the group of pathological mitral valve prostheses, regurgitation (N = 31) was associated with a high early diastolic pressure gradient (20.2 +/- 8 mmHg) and a normal or shortened PHT (84 +/- 28 ms). Obstructed prostheses (N = 11) had high mean pressure gradients (17 +/- 5 mmHg) and increased PHT (195 +/- 53 ms). All cases of obstruction were correctly identified by the Doppler but 4 prosthetic valve regurgitations were missed or underestimated (4 mechanical prostheses).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
104.
The authors report a case of percutaneous closure of paravalvular mitral regurgitation in a 9 year old child. This patient had complete atrioventricular canal with levo-isomerism completely repaired with replacement of the left atrioventricular valve by a mechanical prosthesis. One year after an episode of infectious endocarditis, the patient was readmitted because of jaundice due to haemolysis attributed to paravalvular mitral regurgitation. Transoesophageal echocardiography demonstrated a crescent-shaped dehiscence of the prosthesis opposite the left atrial appendage associated with a small paraseptal regurgitation. First of all, a 6 mm Amplatzer Septal Occluder and a 5 x 5 coil were introduced by retrograde catheterisation to treat the regurgitation due to the valve dehiscence. This procedure was completed 3 months later by the implantation of a second 8 mm Amplatzer prosthesis for persistent haemolysis. Closure of the paraseptal regurgitation resulted in a reduction of the patient's transfusional requirements.  相似文献   
105.
OBJECTIVES: We sought to highlight the clinical, morphologic, and pathogenetic features in patients with a cleft mitral valve (MV). BACKGROUND: Few studies have addressed the morphologic features of cleft MV and the outcome of these patients. The pathogenetic features, including the developmental relation to an atrioventricular (AV) septal defect, remain unclear. METHODS: We reviewed the patients with cleft MV that were diagnosed by echocardiography since 1980. Patients with an AV canal, ventriculo-arterial discordance, and hypoplastic ventricles were excluded. RESULTS: Twenty-two patients were identified at a median age of 0.5 years (range 0 to 10.6). In three patients, no chordal attachments of the cleft to the ventricular septum were seen. Ten patients had significant mitral regurgitation (MR), and three had subaortic obstruction by the cleft. Associated cardiac lesions and extracardiac features were present in 13 and 10 patients, respectively. During the median follow-up period of 1.5 years (range 0 to 11.8), two patients died of extracardiac causes, and one neonate died of severe subaortic obstruction. Surgical repair was performed in 10 patients at a median age of 5.2 years (range 1.3 to 10.6). Multivariate analysis showed no predictors for MV surgery. One patient was re-operated for mitral stenosis associated with aortic valve stenosis. Follow-up echocardiography demonstrated moderate MR in two unoperated patients and moderate MV stenosis in two operated patients. CONCLUSIONS: A cleft of the MV comprises a wide spectrum. Important morphologic differences exist with an AV septal defect, although the two lesions may be pathogenetically related. Surgical repair always seems possible. Long-term echocardiographic follow-up is warranted.  相似文献   
106.
BACKGROUND: In the general population, pulse pressure (PP) is a correlate of cardiovascular outcomes. Few data are available regarding the links between PP and documented coronary artery disease (CAD). METHODS: From July 2000 to January 2002, a total of 1337 patients referred for a first diagnostic coronary angiogram at 75 participating centers were prospectively included. Of these individuals, 280 patients receiving no hypertensive therapy constituted the study population. Pulse pressure was recorded in the aortic root before angiography, and baseline characteristics, medical history, treatment used, and data from coronary angiography were recorded. RESULTS: In the whole population, aortic PP strongly correlated with the presence and extent of CAD in univariate analyses. However, the correlation disappeared in multivariate analysis, and a strong interaction with gender was found. In women (n = 82), aortic PP was not an independent predictor of CAD. However, in men (n = 198) an independent correlation between aortic PP and CAD was found, together with age and hypercholesterolemia. In addition, PP was strongly correlated with the extent of CAD (no disease, 51 +/- 16 mm Hg; one or two stenoses, 54 +/- 18 mm Hg; and more than two stenoses: 64 +/- 20 mm Hg). CONCLUSIONS: In this multicenter study, aortic PP was significantly correlated with the presence and extent of CAD in patients without antihypertensive therapy. This correlation, however, was independent of other risk factors for CAD in men but not in women.  相似文献   
107.
108.
OBJECTIVE: Prediction of the clinical course of Crohn's disease (CD) is difficult in the long term. Our aim was to determine whether the presence of severe endoscopic lesions (SELs) may predict a higher risk of colectomy and penetrating complications. METHODS: All patients at our institution with active ileocoIonic CD who had colonoscopies between 1990 and 1996 were included in the study. SELs were defined as extensive and deep ulcerations covering more than 10% of the mucosal area of at least one segment of the colon. RESULTS: Among the 102 patients included, 53 had SELs at index colonoscopy. During the follow-up (median = 52 months), 37 patients underwent colonic resection. Probabilities of colectomy at 1, 3, and 8 yr were 20%, 26%, and 42%. Risk of colectomy was independently affected by the presence of SELs at index colonoscopy (relative risk [RR] = 5.43, 95% CI = 2.64-11.18), a Crohn's Disease Activity Index level greater than 288 (RR = 2.21, 95% CI = 1.09-4.47), and the absence of immunosuppressive therapy during the follow-up (RR = 2.44, 95% CI = 1.20-5.00). Probabilities of colectomy were, respectively, 31% and 6% at 1 yr, 42% and 8% at 3 yr, and 62% and 18% at 8 yr in patients with and without SELs. We performed a second analysis excluding the 14 patients operated on within the 3 months after the index colonoscopy: presence of SELs remained the only significant factor predictive of colectomy (RR = 6.72, 95% CI = 2.26-20.03). All six patients with penetrating complications during the follow-up had SELs at index colonoscopy. CONCLUSIONS: Patients with CD exhibiting deep and extensive ulcerations at colonoscopy have a more aggressive clinical course with an increased rate of penetrating complications and surgery.  相似文献   
109.
Our aim in this study was to examine the relationship between regular exercise and major cardiovascular events in hypertensive elderly with established coronary heart disease (CHD) in the primary care setting. The PREHACOR study recruited 3193 hypertensive patients, aged 74 ± 6 years, 67% male, with CHD. Regular exercise assessed by questionnaire was defined as recreational activity >20 min/day, >3 times/week. Endpoints at 6 months were new cardiovascular events (NCEs: myocardial infarction and hospitalization for stroke, unstable angina, congestive heart failure, or coronary revascularization). New cardiovascular events occurred in 376 patients (11.8%), with 17 deaths (0.5%). New cardiovascular events patients were older, with higher body mass index, and were more likely to have diabetes, arrhythmia, history of congestive heart failure, and noncardiac organ damage than non-NCE patients. Blood pressure was significantly and similarly reduced in both groups. Multivariate logistic regression associated NCEs positively and independently with a history of congestive heart failure (odds ratio [OR] 2.50; confidence interval [CI] = 1.9–3.23), noncardiac target organ damage (OR 1.51; CI = 1.20–1.90), and beta-blocker use (OR 1.28; CI = 1.02–1.59), and inversely and independently with combination low-dose angiotensin converting enzyme inhibitor + diuretic therapy (OR 0.66; CI = 0.45–0.95) and regular exercise (OR 0.70; CI = 0.54–0.90). Regular exercise is significantly associated with fewer major cardiovascular events in hypertensive elderly subjects with established CHD.  相似文献   
110.
ContextPsychological distress is associated with adverse health outcomes in serious illness and magnified among patients of low socioeconomic status. Aspects of one's culture, such as religion and spirituality, can influence these patients' coping response to distress. Advanced chronic kidney disease (CKD) is a serious illness that disproportionately affects patients of low socioeconomic status, but a theory-based understanding of this group's lived experience of CKD is lacking.ObjectivesWe explored the cognitions, emotions, and coping behaviors of patients with CKD with emphasis on those of low socioeconomic status. We further inquired into any influences of religion or spirituality.MethodsWe interviewed 50 English-speaking or Spanish-speaking adults with advanced CKD from three medical centers in Nashville, Tennessee. Analyses occurred with isolation of themes; development of a coding system; and creation of a conceptual framework using an inductive-deductive approach.ResultsMedian age was 65 years; median annual income was $17,500 per year; and 48% of participants had not progressed beyond high school. Key beliefs (awareness of mortality and lack of control) influenced patients' emotions (existential distress in the form of death anxiety, prognostic uncertainty, and hopelessness) and coping behaviors (acceptance, avoidance, emotion regulation via spirituality, and seeking social support via a religious community).ConclusionIndividuals with advanced CKD and low socioeconomic status lack control over disease progression, experience death anxiety and existential distress, and emphasize spirituality to cope. Our study identifies novel components for a psychotherapeutic intervention for patients with advanced CKD at high risk for adverse health outcomes.  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