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   675篇
  免费   79篇
  国内免费   8篇
耳鼻咽喉   3篇
儿科学   66篇
妇产科学   6篇
基础医学   96篇
口腔科学   30篇
临床医学   72篇
内科学   137篇
皮肤病学   19篇
神经病学   25篇
特种医学   128篇
外科学   40篇
综合类   42篇
预防医学   24篇
眼科学   29篇
药学   12篇
肿瘤学   33篇
  2023年   2篇
  2022年   2篇
  2021年   5篇
  2020年   6篇
  2019年   7篇
  2018年   19篇
  2017年   7篇
  2016年   21篇
  2015年   22篇
  2014年   26篇
  2013年   40篇
  2012年   23篇
  2011年   14篇
  2010年   42篇
  2009年   44篇
  2008年   15篇
  2007年   27篇
  2006年   12篇
  2005年   19篇
  2004年   7篇
  2003年   11篇
  2002年   5篇
  2001年   7篇
  2000年   6篇
  1999年   5篇
  1998年   40篇
  1997年   42篇
  1996年   42篇
  1995年   36篇
  1994年   22篇
  1993年   28篇
  1992年   4篇
  1991年   6篇
  1990年   6篇
  1989年   18篇
  1988年   15篇
  1987年   10篇
  1986年   13篇
  1985年   14篇
  1984年   7篇
  1983年   12篇
  1982年   5篇
  1981年   13篇
  1980年   7篇
  1979年   4篇
  1978年   4篇
  1977年   8篇
  1976年   9篇
  1975年   2篇
  1884年   1篇
排序方式: 共有762条查询结果,搜索用时 15 毫秒
91.
BACKGROUND: Although a common dermatosis, idiopathic poikiloderma of the face and neck has not been studied in depth for decades. OBJECTIVES: To reassess the clinical and epidemiological characteristics of poikiloderma of Civatte (PC). MATERIAL AND METHODS: Fifty consecutive patients with PC. Evaluation included history taking and physical examination. Epidemiological and clinical parameters were recorded and analysed. The literature from 1923 until today, was reviewed thoroughly. RESULTS: The frequency of PC among dermatologic patients was estimated to be 1.4%. There were 34 females (68%) and 16 males in the present study. The mean age at diagnosis was 47.8 years for females and 61.7 years for males. The majority (88%) had skin phototype II or III. Among females, 26 were at their peri-menopausal stage, including three cases of iatrogenic menopause. Four patients reported that other blood-related family members also had PC. The v and the sides of the neck and the upper chest were most often affected in a symmetric distribution. The face (preauricular and parotid region) was involved in 19 patients (38%). The erythemato-telangiectatic clinical type predominated (58%), followed by the mixed (22%) and the pigmented type (20%). Almost half of the patients (46%) were symptomatic (itching, burning and 'flushing'). The mean duration from onset to diagnosis was 6.2 years according to the patients' report. The course was usually slowly progressive (82%) and irreversible. CONCLUSIONS: PC shows characteristic features, supporting the theory that it represents a distinct entity. It is rather common in Greece. Although menopausal women predominated in our cohort, men were not uncommonly affected and were diagnosed at an older age. Based on the predominating clinical feature, PC can be classified into three clinical forms. Symmetry and sparing of the anatomically shaded areas of the neck are highly characteristic for PC. Face involvement was not as common and as severe as it had been considered in the past. Recognition of clinical type is important for the selection of the most appropriate treatment, which, despite the advent of novel modalities, remains problematic.  相似文献   
92.
1. We evaluated the use of non-radioactive fluorescent-labelled microspheres (FM) for the measurement of regional myocardial blood flow (RMBF) in an ischaemic sheep model. 2. Injection of FM directly into the coronary artery was compared with left atrial injection. There was a good correlation in the measurement of RMBF between these two injection methods (r = 0.92; n= 107 data points). Injection into the coronary artery requires less FM (one twentieth of that required by atrial injection) and is more economical. 3. The use of a fluorescent technique without filtering myocardial tissue was investigated. Calibration curves from the fluorescence plus myocardial tissue samples were similar to those of the pure fluorescence samples and both showed a linear relationship between fluorescent intensity and the number of microspheres (r > 0.97). These results indicate that the extraction of six fluorescent dyes (blue-green, yellow-green, green, orange, red and crimson) directly from the aqueous solution using ethyl acetate is effective. 4. A subendocardial ischaemic model was produced by partially occluding the circumflex artery (CxA) with concomitant left atrium (LA) pacing. During ischaemia, the endocardium/epicardium (Endo/Epi) flow ratios in the ischaemic area changed from 1.04 ± 0.12 to 0.47 ± 0.17 (P < 0.05; CxA injection) and from 1.08 ± 0.12 to 0.51 ± 0.05 (P < 0.05; LA injection). The ratio in the non-ischaemic area remained unchanged (1.12 ± 0.26 to 1.01 ± 0.22; not significant). 5. RMBF calculation using coronary inflow as the reference flow was also compared with that using the traditional method. We found that, in this study in which a non-filtering technique was applied, using coronary inflow as the reference flow was superior to the conventional distal sampling method.  相似文献   
93.
94.
BACKGROUND.: The effectiveness of health promotion activity in general practiceon risk factor reduction for coronary heart disease remainsthe subject of active debate. OBJECTIVE.: The study aimed to assess the impact of practice-based healthcheck-ups on health behaviours over a 2-year period. METHOD.: A general practice cohort of 7123 patients from 18 practiceswas surveyed. Eight hundred and forty (12%) patients had beenoffered a heafth check within a 12-month period from September1992 and 621 (9%) received one. Two hundred and fifty patients(40%) were asked back for follow-up after their health check. RESULTS.: Over a 2-year period there was no difference in smoking cessation,alcohol consumption, weight loss nor the amount of exercisetaken between those who attended for a health check and thosewho did not. The food score chosen to assess dietary change(Oxcheck) showed a statistically significant 1.16-point risefor the whole sample over the survey period. There was a significantdifference in mean food score change between heafth check attendersand non-attenders (Mann-Whitney U test: P << 0.002). Maintenanceof dietary improvement over a 2-year period was not affectedby health check attendance. CONCLUSIONS.: This study confirms the low impact of health checks on the selfreported modification of cardiovascular risk factors and showsthat maintenance of appropriate health behaviour change is nomore likely in those who have received a health check. Keywords. Health promotion, general practice.  相似文献   
95.
Peripheral vascular disease: correlation of MR imaging and angiography   总被引:1,自引:0,他引:1  
The capability of magnetic resonance (MR) imaging for detecting aortic, iliac, and femoral stenoses and occlusions was evaluated. Multisection spin-echo studies at 0.35 tesla were obtained of the infrarenal aorta to the femoral bifurcation in 24 patients, all of whom had undergone intraarterial angiography within 14 days of imaging. Transaxial MR images were compared with the angiograms. Arterial stenoses and occlusions in these vessels detected by MR imaging correlated with angiographic findings in 91% of the instances. Protrusional atherosclerotic plaques and occlusions and stenoses in the aortoiliac region were demonstrated accurately on MR images; complications of previous vascular surgery, such as aneurysms at sites of previous anastomoses or endarterectomy, were also identified. Due to the limited spatial resolution, MR images failed to demonstrate some femoral stenoses. MR imaging may be used for evaluation of aortoiliac vascular disease and for follow-up study after surgical revascularization. However, the limited spatial resolution, noncomposite display of the aortoiliofemoral circulation, and lack of evaluation of peripheral runoff provided by current MR imaging techniques militate against its replacing angiography prior to vascular intervention.  相似文献   
96.
97.
98.
Accessory muscles of the lower calf   总被引:1,自引:0,他引:1  
  相似文献   
99.
The serum levels of soluble intercellular adhesion molecule 1 (ICAM-1) were significantly elevated (P < .001) in patients with chronic B- lymphocytic leukemia (B-CLL, n = 113) compared with healthy controls (n = 31). sICAM-1 levels in B-CLL were positively correlated to the tumor mass as reflected by the modified Rai and the Binet staging systems, lymphocyte counts, and isolated spleno/hepatomegaly. During disease progression or regression on cytoreductive therapy, the circulating sICAM-1 levels changed accordingly. sICAM-1 was also correlated to a kinetic parameter such as the lymphocyte doubling time. Furthermore, the serum sICAM-1 levels were inversely correlated to hemoglobin levels in patients with early clinical stage, and this may turn out to be of prognostic value. sICAM-1 was compared with other serum markers said to reflect disease activity in B-CLL, ie, soluble CD23, thymidine kinase, lactate dehydrogenase (LDH), and beta 2-microglobulin. sICAM-1 was equally well or better correlated to clinical stage and lymphocyte doubling time. In univariate regression analysis, all serum markers but LDH correlated with survival, and in multivariate analysis, sICAM-1 was the only marker approaching significance for additional prognostic information when included after clinical stage and lymphocyte doubling time. Based on the present observations, it appears that prospective studies repeatedly monitoring serum sICAM-1 in B-CLL are justified.  相似文献   
100.
High-resolution P-31 MR spectra were obtained in four patients with bone tumors of their distal extremities. In one case the tumor, a Ewing sarcoma of the tibia, was investigated during clinical remission after radiation therapy and chemotherapy. The other three cases - one low-grade chondrosarcoma of the tibial head, one malignant fibrous histiocytoma of the tibia, and one chondroblastoma of the medial femoral condyle - showed clinically active tumor growth, with corresponding increased metabolism as demonstrated by bone scintigraphy. The spectra of the three active tumors indicated a comparably high adenosine triphosphate content, similar to previously published spectra from animal tumors or human tumors implanted into animals. There were also high resonances of inorganic phosphate and low resonances of phosphocreatine; there were definite peaks in the phosphodiester and phosphomonoester regions, indicating the existence of these metabolites in the tumors. Slight but definite changes in the metabolite content were observed in one tumor after chemotherapy. The spectra of the unaffected leg did not show any well-resolved P-31 signals, which is typical for healthy bone. These are the first P-31 MR spectra of human bone tumors measured in patients to our knowledge.  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