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   1193篇
  免费   80篇
  国内免费   13篇
儿科学   22篇
妇产科学   26篇
基础医学   120篇
口腔科学   19篇
临床医学   101篇
内科学   348篇
皮肤病学   6篇
神经病学   155篇
特种医学   55篇
外科学   176篇
综合类   1篇
预防医学   33篇
眼科学   9篇
药学   104篇
中国医学   1篇
肿瘤学   110篇
  2024年   1篇
  2023年   23篇
  2022年   32篇
  2021年   27篇
  2020年   18篇
  2019年   29篇
  2018年   28篇
  2017年   19篇
  2016年   44篇
  2015年   42篇
  2014年   52篇
  2013年   69篇
  2012年   113篇
  2011年   108篇
  2010年   44篇
  2009年   41篇
  2008年   56篇
  2007年   91篇
  2006年   66篇
  2005年   77篇
  2004年   73篇
  2003年   67篇
  2002年   39篇
  2001年   5篇
  2000年   12篇
  1999年   4篇
  1998年   10篇
  1997年   8篇
  1996年   12篇
  1995年   3篇
  1994年   4篇
  1993年   7篇
  1992年   8篇
  1991年   4篇
  1990年   9篇
  1989年   3篇
  1988年   5篇
  1987年   6篇
  1986年   5篇
  1985年   2篇
  1984年   3篇
  1983年   3篇
  1981年   4篇
  1980年   3篇
  1979年   2篇
  1978年   1篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
排序方式: 共有1286条查询结果,搜索用时 15 毫秒
81.
BACKGROUND: Our aim was to prospectively evaluate a semi-quantitative pulmonary perfusion MR technique using a breath-hold 2D dynamic sequence in patients with severe pulmonary emphysema. MATERIALS AND METHODS: Thirty patients with severe emphysema were studied with pulmonary perfusion MRI. Results were compared with those obtained through lung scintigraphy, considered as the gold standard technique. We used Fast Field Echo (FFE) pulse sequences in the coronal and sagittal planes, with paramagnetic contrast agent administration. Ten healthy volunteers were studied as the control group. Three thoracic radiologists independently reviewed all the subjects, evaluating the site and entity of perfusional defects. Peak intensity and apparent mean transit time were calculated. RESULTS: MRI showed high sensitivity (86.7%) and good specifity (80.0%) in detecting perfusional defects. We observed lower peak signal intensities in emphysematous regions. CONCLUSION: Lung perfusion MR is a potential alternative to Nuclear Medicine in the evaluation of severe pulmonary emphysema.  相似文献   
82.
OBJECTIVE: With liberalization of donor eligibility criteria, organs are being harvested from remote locations, increasing donor ischemic times. Although several studies have evaluated the effects of prolonged donor ischemic times on short-term survival and graft function, few have addressed concerns regarding long-term survival. METHODS: Over the last 11 years, 819 consecutive adults underwent cardiac transplantation at Columbia Presbyterian Medical Center. Recipients were separated into the following 4 groups based on donor ischemic time: <150 minutes, 150 to 200 minutes, 200 to 250 minutes, and >250 minutes. Statistical analysis included Kaplan-Meier survival and Cox proportional hazard models to identify predictors of long-term survival. RESULTS: Donor ischemic time was 120.1 +/- 21.1 minutes for group 1 (n = 321), 174.1 +/- 14.7 minutes for group 2 (n = 264), 221.7 +/- 14.6 minutes for group 3 (n = 154), and 295.5 +/- 37.1 minutes for group 4 (n = 80) (P <.001). There were no significant differences in recipient age, donor age, etiology of heart failure, United Network for Organ Sharing status, or history of previous cardiac surgery among the groups (P = NS). Prolonged donor ischemic time did not adversely affect long-term survival, with actuarial survival at 1, 5, and 10 years of 86.9%, 75.2%, and 56.4% for group 1; 86.2%, 76.9%, and 50.9% for group 2; 86.4%, 71.0%, and 43.7% for group 3; and 86.7%, 70.1%, and 50.9% for group 4 (P =.867). There was no significant difference in freedom from transplant coronary artery disease among the 4 groups (P =.474). CONCLUSIONS: Prolonged donor ischemic time is not a risk factor for decreased long-term survival. Procurement of hearts with prolonged donor ischemic time is justified in the setting of an increasing recipient pool with a fixed donor population.  相似文献   
83.
84.
Choroidal metastases have been observed in about 8% of patients with metastatic breast cancer, even if their true incidence is likely to be higher, as they are not routinely investigated in the absence of symptoms. Radiotherapy is the treatment of choice for symptom palliation. The prognosis is traditionally poor, with a reported average survival of one year. Here we describe the third case reported in the literature of a metastatic tumor to the choroid from a male breast carcinoma.  相似文献   
85.
Lonidamine, a derivate of indazole-3-carboxylic acid, is an antineoplastic drug with a typical mechanism of action. Lonidamine has no function on cellular nucleic acids or protein synthesis, whereas it exerts a powerful inhibitory effect on oxygen consumption, aerobic glycolysis and lactate transport and accumulation of neoplastic cells. Nevertheless, its proven ability to modify the permeability of membranes is consistent with the possible increase of drug uptake, reverse of drug resistance and triggering of apoptotic pathway. Lonidamine has been experimentally shown to potentiate the cytotoxic effects of anthracyclines in human breast cancer cell lines and cisplatin activity in both platinum-sensitive and platinum-resistant human ovarian carcinoma cell lines. Since the specific mechanism of action and side effects are not overlapping with those of standard antineoplastic agents, combination of lonidamine with standard chemotherapy has been widely investigated for the treatment of solid tumors. Additionally, the enhancement of radiotherapy activity by lonidamine has been considered for palliative therapy of lesions from metastatic cancers. The encouraging results of phase II-III trials for the treatment of advanced breast, ovarian and lung cancer must be confirmed by larger studies. Specifically designed studies to address the role of lonidamine in the adjuvant setting are warranted. Lonidamine, a dechlorinate derivative of indazole-3-carboxylic acid, has proved to exert a powerful antiproliferative effect and to impair the energy metabolism of neoplastic cells. Herein we review the current experience on combining lonidamine and chemotherapy and/or radiation therapy in the treatment of solid tumors. Several studies have been published on this topic. The total number of trials reported in literature and length of follow-up are still insufficient to draw a firm conclusion. However, the available data demonstrate a significant role of lonidamine in modulating anthracycline and platinum compound activity.  相似文献   
86.
87.
Selective delay activity in the cortex: phenomena and interpretation   总被引:2,自引:1,他引:1  
The present article does not intend to present technical progress nor recent successes in accounting for experiments, as this issue of the journal presents a rich inventory. Rather, the paper presents a retrospective reflection on the history of the subject; on the relation between the different aspects of the concepts and the phenomena involved; on its strengths and weaknesses; and on some future prospects. It is a tribute to an extremely rich and growing wealth of physiological phenomena and of interpretative concepts. Yet the extent of achievement is used to expose open questions, which appear to become ever deeper. It is also an attempt to make the subject a matter of discourse between biologists and modelers, without the distraction of technical details.  相似文献   
88.
The authors report the early results of a case-control study carried out about the risk of legionellosis. During the first year, they have tested urine samples from patients with unknown pneumonia, using a legionella-sensitive test for the detection of its antigen. Out of 171 samples, 9 have turned out to be positive (5.3%). Lifestyles, predisposing factors, possible sources of infection and stressful events were investigated.  相似文献   
89.

Background  

Little is known about the prevalence of depressive symptoms in the Italian general population, nor about help-seeking behaviours among those with depressive symptoms.  相似文献   
90.
OBJECTIVES: To establish a novel nutritional score based on a series of objective parameters capable of detecting protein-calorie malnutrition in children being treated with chronic peritoneal dialysis (CPD), to test the score in a healthy pediatric population, and to apply it to children on CPD to evaluate their nutritional status. STUDY POPULATION: 264 healthy school children (mean age 8.69 +/- 3.26 years, range 3.05-14.98 years) and 29 patients treated with CPD for 1.75 +/- 1.02 years (mean age 10.54 +/- 6.28 years, range 2.8-15.24 years). METHODS: Nutritional status was evaluated by means of three sets of measurements: anthropometric (A1 and A2) and bioimpedance analysis (BIA) measurements. Anthropometry included two sets of measures: set A1 consisted of height (H), weight (W), and body mass index (BMI); set A2 consisted of midarm muscle circumference (MAMC), arm muscle area (AMA), and arm fat area (AFA). The BIA measurements included reactance, phase angle, and distance. All parameters are expressed as standard deviation scores (SDS).Tanner's, Rolland-Cachera's, and Frisancho's data were used as references for H, W, BMI, MAMC, AMA, and AFA; personal data obtained from 551 healthy boys and girls were used for the BIA indices. The nine anthropometry and BIA parameters were given scores of 1 to 5: 5 = > 0 SDS, 4 = < or = 0 and > -1 SDS, 3 = < or = -1 and > -2 SDS, 2 = <-2 and > -3 SDS, and 1 = < or = -3 SDS. Average scores were established for each of A1, A2, and BIA, and then summed to obtain the anthropometry-BIA nutrition (ABN) score. To establish the cutoff value between normal nutritional status and malnutrition, the method was first applied to the 264 healthy children; distribution percentiles were calculated for each area score and the ABN score. The ABN score corresponding to the 3rd percentile was considered the limit of normality and then applied three times to the 29 children on CPD, for a total of 87 nutritional assessments. RESULTS: The score corresponding to the 3rd percentile in the population of healthy children was 10.33. Among the CPD-treated children, 41.4% of the ABN scores were higher than 10.33 (indicating a state of normal nutrition) and 58.6% were lower (indicating various degrees of malnutrition). Severe malnutrition was found in only 1.1% of the cases. The values of all nine A1, A2, and BIA parameters, as well as serum albumin levels, were significantly higher in patients with an ABN score > 10.33 than in those with a score < 10.33. CONCLUSION: The ABN score is a simple and objective method of assessing, in clinical practice, the nutritional status of children on CPD.  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