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   1349篇
  免费   71篇
  国内免费   11篇
耳鼻咽喉   25篇
儿科学   67篇
妇产科学   8篇
基础医学   156篇
口腔科学   62篇
临床医学   103篇
内科学   256篇
皮肤病学   12篇
神经病学   188篇
特种医学   27篇
外科学   104篇
综合类   2篇
预防医学   126篇
眼科学   4篇
药学   41篇
中国医学   1篇
肿瘤学   249篇
  2024年   3篇
  2023年   11篇
  2022年   24篇
  2021年   40篇
  2020年   29篇
  2019年   32篇
  2018年   44篇
  2017年   31篇
  2016年   32篇
  2015年   32篇
  2014年   39篇
  2013年   47篇
  2012年   98篇
  2011年   106篇
  2010年   46篇
  2009年   51篇
  2008年   68篇
  2007年   75篇
  2006年   80篇
  2005年   85篇
  2004年   73篇
  2003年   64篇
  2002年   64篇
  2001年   27篇
  2000年   15篇
  1999年   15篇
  1998年   23篇
  1997年   9篇
  1996年   9篇
  1995年   10篇
  1994年   11篇
  1993年   4篇
  1992年   6篇
  1991年   17篇
  1990年   8篇
  1989年   9篇
  1988年   9篇
  1987年   9篇
  1986年   9篇
  1985年   10篇
  1984年   4篇
  1983年   4篇
  1982年   6篇
  1981年   3篇
  1980年   7篇
  1979年   7篇
  1978年   3篇
  1976年   4篇
  1968年   3篇
  1967年   3篇
排序方式: 共有1431条查询结果,搜索用时 31 毫秒
101.
Conventional distal pancreatectomy (cDP) and total pancreatectomy (cTP) also involve removal of the spleen. The spleen, however, is an important organ in the immunologic defense of the host and is worthy of preservation if this can be safely achieved. We performed a spleen-preserving total pancreatectomy (SPTP), with good results, in a Caucasian woman, 66-year-old, affected by pancreatic metastases of renal clear cell carcinoma. This is the first report of a SPTP for pancreatic metastases to our knowledge, and we therefore wish to describe the surgical technique and to suggest the possible indications for this new technique.  相似文献   
102.
The population of bipolar cells in the rabbit retina was studied using Golgi impregnation and photocatalyzed filling of single cells with dihydrorhodamine, a quantitative sampling technique. The Golgi method revealed the morphology and stratification of cells in detail. The photofilling method allowed us to estimate the frequency of the cell types. From a sample of 243 Golgi-impregnated bipolar cells and 107 photofilled cells, we identified 1 type of rod bipolar cell and 12 types of cone bipolar cells. An analysis based on retinal coverage indicates that this number of types could be contained within the number of bipolar cells known to exist. The dendrites of most cone bipolars contacted all the cones within the individual cone bipolar cell's dendritic field. Types of bipolar cell were encountered at roughly similar frequency, without any one type predominating. The rabbit retina thus contains about a dozen parallel and roughly equipotent through-pathways.  相似文献   
103.
PURPOSE: The aim of our work was to estimate the dose to paediatric patients undergoing micturating cystourethrography (MCU), and to optimize those examination procedures that were found to be particularly significant from the point of view of the radiation dose. At the same time it was also decided to evaluate the absorbed dose to the parents, who frequently assist the child during MCU. MATERIALS AND METHODS: The study was carried out on 220 children undergoing micturatig cystourethrography, by measuring in vivo the dose equivalent entering and exiting from the patient with thermoluminescent dosimetry and the KAP (Kerma Area Product). From the latter, the imparted energy and the average absorbed dose to the patients were subsequently calculated. RESULTS: The average absorbed dose was 0.69+/-0.54 mGy, with a variation interval of 0.126-3.110 mGy. A remarkable dispersion of the absorbed dose values was observed, also for subjects of similar size. This indicates that radiation protection of paediatric patients still allows for wide margins of optimization. In fact it was possible to verify that the dose depends not only on the size of the child, but also on his/her degree of cooperation, and on the technical ability of the operator. The latter aspect was estimated by comparing the doses delivered by two different physicians; differences by a factor of 5 were observed. The application of additional filtration of 2 mm of Al (total 5 mm Al) concurred to a dose reduction without significant variations in image quality. The effective dose received by the parents present during the examination was 4+/-7 microSv. CONCLUSIONS: A specific feature of paediatric MCU is not only the amount of radiation dose, often not negligible, but also the remarkable variation of the dose values, even within the same age group. The specialist has an important role in the justification of the examination: the adoption of a specific protocol has allowed reduction of the number of children undergoing MCU. Optimization of the examination requires quality control on the equipment, as well as the adoption of good radiographic techniques and the provision of suitable environments for children. The present study has helped to focus the attention of practitioners on radiation protection and, consequently, to reduce the dose delivered to the children. The effective dose received by the parents showed that their presence can be justified provided that they are adequately protected.  相似文献   
104.
PURPOSE: This paper describes our experience in developing a DICOM (Digital Imaging and Communications in Medicine) server based on widely available personal computers enabling to use X-ray digital images for teaching and scientific purposes. MATERIALS AND METHODS: The system is based on a DICOM server running on a widely used personal computer. The selected DICOM images are collected directly from the radiological equipment or from a dedicated 3D image processing workstation through a LAN connection and converted into one of the standard formats (JPEG or GIF) to allow their direct importing into multimedia presentations for teaching or scientific purposes. RESULTS: This system allows fast and easy collection of radiological images in DICOM format directly from the diagnostic equipment or from the graphical workstation. These images may be used for scientific and teaching presentations without loss of image quality and colour characteristics in 3D images as there is no off-line acquisition process. CONCLUSIONS: The extensive possibilities of implement the system described on widely used PCs makes the system extremely versatile and facilitates the preparation of teaching material and scientific publications.  相似文献   
105.
PURPOSE: To describe our experience in three cases of abdominal haemorrhage caused by bleeding renal angiomyolipomas, which were studied with Computed Tomography (CT). MATERIALS AND METHODS: A retrospective study carried out at our archives identified 3 patients (aged 58.6 on average) with renal angiomyolipomas clinically manifested with acute abdomen and haemorrhage. The patients underwent an emergency CT scan of the abdomen. One patient also under-went a subsequent renal angiography. All patients had surgery and histological characterizations of the renal lesions. RESULTS: The CT study on all three patients allowed detection of a lesion in the kidneys with inhomogeneous density due to haemorrhage. Areas with fat-density values (-60 -80 UH) were always observable within the lesions. The lesions, measuring 5-9 cm, were located in the right kidney in two patients and in the left kidney in one. CONCLUSIONS: In 40% of patients, renal angiomyolipoma may account for a picture of hypovolemic shock, so a correct diagnostic approach is important to guide the surgical approach. CT allows detection of the angiomyolipoma as the cause of the haemorrhage in most cases. The diagnosis is relatively simple when the lesion has typical features such as adipose content, whereas it may be difficult with non-typical aspects. Furthermore the fat content may also be detected in varying quantities in other renal lesions responsible for bleeding.  相似文献   
106.
AIM OF THE STUDY: To evaluate the effectiveness of oral amoxicillin/clavulanate (25 mg/kg every 12 h) for prevention of fever and/or infection in neutropenic children with cancer. METHODS: Multicenter, prospective, randomized, double blind placebo-controlled trial. RESULTS: In the intention-to-treat analysis, amoxicillin/clavulanate had a 12% benefit increase in terms of reduction in the incidence of febrile or infectious episodes, compared with placebo [44 of 83 (53%) vs.55 of 84 (65%); 95% confidence interval, -28% to +3%; P = 0.101]. This benefit was also associated with a 30% increase in the probability of failure-free survival at Day 15 (P = 0.138). A logistic regression analysis showed the effect of prophylaxis to be relevant, especially in patients with leukemia or lymphoma and in those not receiving hematopoietic growth factors, with 17 and 15% absolute benefit increases (logistic P = 0.014 and 0.034, respectively). Compliance with oral drugs was good, with very few and nonsevere drug-related adverse events. CONCLUSIONS: In this study amoxicillin/clavulanate was associated with a detectable clinical effect in the reduction of fever and infection in neutropenic children with cancer, especially those with acute leukemia and not receiving growth factors; the study was not powered to demonstrate a statistically significant effect in the overall patient population.  相似文献   
107.
ICU nurses hold an important role in the management of septic patients underlining with their ability to recognize SIRS that is the first step in the proinflammatory and procoagulant cascade following an infection. Early and timely approach to organ dysfunction can indeed modify the damages due to hypoperfusion. The ability to recognize organ dysfunction using different monitoring devices available should be part of the nursing attitudes.  相似文献   
108.
Many factors have been proposed as predictors of poor renal prognosis in children with hemolytic uremic syndrome (HUS), but their role is still controversial. Our aim was to detect the most reliable early predictors of poor renal prognosis to promptly identify children at major risk of bad outcome who could eventually benefit from early specific treatments, such as plasmapheresis. Prognostic factors identifiable at onset of HUS were evaluated by survival analysis and a proportional hazard model. These included age at onset, prodromal diarrhea (D), leukocyte count, central nervous system (CNS) involvement, and evidence of Shiga toxin-producing Escherichia coli (STEC) infection. Three hundred and eighty-seven HUS cases were reported; 276 were investigated for STEC infection and 189 (68%) proved positive. Age at onset, leukocyte count, and CNS involvement were not associated with the time to recovery. Absence of prodromal D and lack of evidence of STEC infection were independently associated with a poor renal prognosis; only 34% of patients DSTECrecovered normal renal function compared with 65%–76% of D+STEC+, D+STEC and DSTEC+ patients. In conclusion, absence of both D and evidence of STEC infection are needed to identify patients with HUS and worst prognosis, while D but STEC+ patients have a significantly better prognosis.  相似文献   
109.
We and others have demonstrated expression of the aldo-keto reductase AKR1C3 in myeloid leukemia cell lines and that inhibitors of the enzyme, including nonsteroidal anti-inflammatory drugs (NSAIDs), promote HL-60 differentiation in response to all-trans retinoic acid (ATRA) and 1alpha,25-dihydroxyvitamin D3 (D3). Here, we demonstrate that overexpression of AKR1C3 reciprocally desensitizes HL-60 cells to ATRA and D3, thus confirming the enzyme as a novel regulator of cell differentiation. AKR1C3 possesses marked 11-ketoreductase activity converting prostaglandin (PG) D2 to PGF2alpha. Supplementing HL-60 cultures with PGD2 mimicked treatment with AKR1C3-inhibitors by enhancing the differentiation of the cells in response to ATRA. However, PGD2 is chemically unstable, being converted first to PGJ2 and then stepwise to 15-deoxy-Delta(12,14)-prostaglandin J2(15Delta-PGJ2), a natural ligand for the peroxisome proliferator-activated receptor-gamma (PPARgamma). Consistent with this, PGD2 was rapidly converted to PGJ2 under normal tissue culture conditions but not in the presence of recombinant AKR1C3 when PGF2alpha was predominantly formed. In addition, PGJ2 but not PGF2alpha recapitulated the potentiation of HL-60 differentiation by PGD2 and AKR1C3 inhibitors. Furthermore, the capacity of all of these treatments to potentiate HL-60 cell differentiation was significantly reduced in the presence of the PPARgamma-antagonist GW 9662. We conclude that AKRIC3 protects HL-60 cells against ATRA and D3-induced cell differentiation by limiting the production of natural PPARgamma ligands via the diversion of PGD2 toward PGF2alpha and away from PGJ2. In addition, these observations identify AKR1C3 as plausible target for the non-cyclooxygenase-dependent antineoplastic actions of NSAIDs.  相似文献   
110.
Smoking has recently been recognised as causally associated with the development of gastric cancer (GC). However, evidence on the effect by sex, duration and intensity of smoking, anatomic subsite and cessation of smoking is limited. Our objective was to assess the relation between tobacco use and GC incidence in the European Prospective Investigation into Cancer and Nutrition (EPIC). We studied data from 521,468 individuals recruited from 10 European countries taking part in the EPIC study. Participants completed lifestyle questionnaires that included questions on lifetime consumption of tobacco and diet in 1991-1998. Participants were followed until September 2002, and during that period 305 cases of stomach cancer were identified. After exclusions, 274 were eligible for the analysis, using the Cox proportional hazard model. After adjustment for educational level, consumption of fresh fruit, vegetables and preserved meat, alcohol intake and body mass index (BMI), there was a significant association between cigarette smoking and gastric cancer risk: the hazard ratio (HR) for ever smokers was 1.45 (95% confidence interval [CI] = 1.08-1.94). The HR of current cigarette smoking was 1.73 (95% CI = 1.06-2.83) in males and 1.87 (95% CI = 1.12-3.12) in females. Hazard ratios increased with intensity and duration of cigarette smoked. A significant decrease of risk was observed after 10 years of quitting smoking. A preliminary analysis of 121 cases with identified anatomic site showed that current cigarette smokers had a higher HR of GC in the cardia (HR = 4.10) than in the distal part of the stomach (HR = 1.94). In this cohort, 17.6 % (95% CI = 10.5-29.5 %) of GC cases may be attributable to smoking. Findings from this large study support the causal relation between smoking and gastric cancer in this European population. Stomach cancer should be added to the burden of diseases caused by smoking.  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