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   5531篇
  免费   430篇
  国内免费   16篇
耳鼻咽喉   103篇
儿科学   246篇
妇产科学   86篇
基础医学   743篇
口腔科学   81篇
临床医学   447篇
内科学   1184篇
皮肤病学   148篇
神经病学   289篇
特种医学   216篇
外科学   630篇
综合类   339篇
一般理论   4篇
预防医学   344篇
眼科学   84篇
药学   433篇
中国医学   30篇
肿瘤学   570篇
  2022年   68篇
  2021年   121篇
  2020年   68篇
  2019年   100篇
  2018年   133篇
  2017年   82篇
  2016年   119篇
  2015年   124篇
  2014年   169篇
  2013年   211篇
  2012年   356篇
  2011年   346篇
  2010年   206篇
  2009年   180篇
  2008年   289篇
  2007年   311篇
  2006年   223篇
  2005年   198篇
  2004年   196篇
  2003年   181篇
  2002年   151篇
  2001年   161篇
  2000年   163篇
  1999年   160篇
  1998年   82篇
  1997年   74篇
  1996年   58篇
  1995年   55篇
  1994年   54篇
  1993年   45篇
  1992年   120篇
  1991年   81篇
  1990年   78篇
  1989年   104篇
  1988年   59篇
  1987年   70篇
  1986年   57篇
  1985年   75篇
  1984年   42篇
  1983年   30篇
  1982年   34篇
  1979年   28篇
  1977年   45篇
  1976年   27篇
  1975年   26篇
  1974年   32篇
  1973年   41篇
  1972年   34篇
  1971年   29篇
  1967年   33篇
排序方式: 共有5977条查询结果,搜索用时 11 毫秒
71.
PurposeThe purpose of this study was to review the principles involved in the management of proximal femoral fractures as reported in the literature. Methods: A medical literature search in the MEDLINE (PubMed) and Cochrane database was undertaken to review strategies and principles in proximal femoral fracture treatment. Randomized control trials and meta analysis were given preference while case reports/small series were rejected. Results and conclusions: Early anatomical reduction and surgical fixation remains the best option to reduce the risk of complications like non-union and avascular necrosis in treating fracture neck femurs. Cancellous screws continue to be the preferred treatment for fixation of neck femur fractures in younger population until the benefit of using sliding hip screws is validated by large multicentric studies. In the geriatric age group, early prosthetic replacement brings down the mortality and morbidity associated with neck femur fractures. Sliding hip screw (DHS) is the best available option for stable inter trochanteric fractures. The use of intramedullary nails e.g. PFN is beneficial in treating inter trochanteric fractures with comminution and loss of lateral buttress. Intramedullary implants have been proven to have increased success rates in subtrochanteric fractures and should be preferred over extramedullary plate fixation systems.  相似文献   
72.
A study was conducted to evaluate the potential of autologous bone marrow-derived cells in comparison with buffy coat of autologous blood for rapid cutaneous wound healing in rabbit model. Three square full-thickness skin excisional wounds were created in 15 selected experimental animals (rabbit) divided randomly into three groups. The wound was treated with autologous bone marrow cells in plasma (group 1), buffy coat of blood in plasma (group 2) and autologous plasma as control (group 3). Wounds were observed for 30 days for granulation tissue formation, biochemical, histomorphological and histochemical evaluation. In this study, granulation tissue appeared significantly lesser in wounds of group 3 animals followed by group 2 and 1 animals. Neovascularisation, granulation tissue formation, denser, thicker and better arranged collagen fibres, reticulin fibres and elastin fibres formation was more in group 1 as compared with other groups. It was concluded that the application of bone marrow-derived nucleated cells into the wound margins resulted in early and significantly faster rate of complete healing as compared with buffy coat of autologous blood and autologous plasma (control). This approach may be beneficial in various surface wounds that heal at a slower rate and recommended for healing of various complicated wound in future.  相似文献   
73.
Genetically modified keratinocytes and fibroblasts are suitable for delivery of therapeutic genes capable of modifying the wound healing process. However, efficient gene delivery is a prerequisite for successful gene therapy of wounds. Whereas adenoviral vectors (Ads) exhibit superior levels of in vivo gene transfer, their transductional efficiency to cells resident within wounds may nonetheless be suboptimal, due to deficiency of the primary adenovirus receptor, coxsackie-adenovirus receptor (CAR). We explored CAR-independent transduction to fibroblasts and keratinocytes using a panel of CAR-independent fiber-modified Ads to determine enhancement of infectivity. These fiber-modified adenoviral vectors included Ad 3 knob (Ad5/3), canine Ad serotype 2 knob (Ad5CAV-2), RGD (Ad5.RGD), polylysine (Ad5.pK7), or both RGD and polylysine (Ad5.RGD.pK7). To evaluate whether transduction efficiencies of the fiber-modified adenoviral vectors correlated with the expression of their putative receptors on keratinocytes and fibroblasts, we analyzed the mRNA levels of CAR, alpha upsilon integrin, syndecan-1, and glypican-1 using quantitative polymerase chain reaction. Analysis of luciferase and green fluorescent protein transgene expression showed superior transduction efficiency of Ad5.pK7 in keratinocytes and Ad5.RGD.pK7 in fibroblasts. mRNA expression of alpha upsilon integrin, syndecan-1 and glypican-1 was significantly higher in primary fibroblasts than CAR. In keratinocytes, syndecan-1 expression was significantly higher than all the other receptors tested. Significant infectivity enhancement was achieved in keratinocytes and fibroblasts using fiber-modified adenoviral vectors. These strategies to enhance infectivity may help to achieve higher clinical efficacy of wound gene therapy.  相似文献   
74.
Tobacco smoking is associated with a substantially increased risk of postoperative complications. The peri-operative period offers a unique opportunity to support patients to stop tobacco smoking, avoid complications and improve long-term health. This systematic review provides an up-to-date summary of the evidence for tobacco cessation interventions in surgical patients. We conducted a systematic search of randomised controlled trials of tobacco cessation interventions in the peri-operative period. Quantitative synthesis of the abstinence outcomes data was by random-effects meta-analysis. The primary outcome of the meta-analysis was abstinence at the time of surgery, and the secondary outcome was abstinence at 12 months. Thirty-eight studies are included in the review (7310 randomised participants) and 26 studies are included in the meta-analysis (5969 randomised participants). Studies were pooled for subgroup analysis in two ways: by the timing of intervention delivery within the peri-operative period and by the intensity of the intervention protocol. We judged the quality of evidence as moderate, reflecting the degree of heterogeneity and the high risk of bias. Overall, peri-operative tobacco cessation interventions increased successful abstinence both at the time of surgery, risk ratio (95%CI) 1.48 (1.20–1.83), number needed to treat 7; and 12 months after surgery, risk ratio (95%CI) 1.62 (1.29–2.03), number needed to treat 9. More work is needed to inform the design and optimal delivery of interventions that are acceptable to patients and that can be incorporated into contemporary elective and urgent surgical pathways. Future trials should use standardised outcome measures.  相似文献   
75.
76.
We report a process that results in the acceleration of matrix degradation in human articular cartilage, a phenomenon commonly observed in osteoarthritis (OA). The study was conducted by (1) examining the potential of collagen II in modulating the gene expression profile of primary human chondrocytes (PHCs), and (2) investigating the involvement of pro‐inflammatory signaling cascades. We first tested the collagen II‐dependent induction of pro‐inflammatory cytokines and matrix metalloproteinases (MMPs) in PHCs. PHCs were incubated with or without monomeric (i.e., nonfibrillar) collagen II. Cells were then analyzed by RT‐PCR for the expression of MMP1, MMP3, MMP13, MMP14, and IL‐1β. ELISA was used to quantify IL‐6 and IL‐8 release. To examine the influence of collagen II signaling, specifically the role of MAPK p38, a p38‐inhibitor was added prior to collagen treatment. Changes in IκB concentration were monitored by immunoblot analysis to detect NFκB signaling. Results indicated that incubation of PHCs with collagen II did produce a dose‐dependent induction of MMP1, MMP3, MMP13, MMP14, as well as cytokines IL‐1β, IL‐6, and IL‐8. At the same time, inhibition of p38 and IκB degradation revealed that collagen II‐dependent gene induction also involves MAPK p38 and NFκB signaling. Thus, we provide evidence for a collagen II‐dependent feed‐forward mechanism whereby collagen II induces first MMPs and pro‐inflammatory cytokines and then release of collagen II fragments from mature collagen II fibers. This, in turn, induces more pro‐inflammatory cytokines and MMPs, and the process is repeated, which results in the acceleration and perpetuation of cartilage matrix degradation. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:65–70, 2009  相似文献   
77.
Bronchiolitis obliterans syndrome (BOS) compromises lung transplant outcomes and is characterised by airway epithelial damage and fibrosis. The process whereby the normal epithelial configuration is replaced by fibroblastic scar tissue is poorly understood, but recent studies have implicated epithelial mesenchymal transition (EMT). The primary aim of this study was to assess the utility of flow cytometry in detecting and quantifying EMT in bronchial epithelial cells.
Large airway brushings were obtained at 33 bronchoscopies in 16 BOS-free and 6 BOS grade 1–3 patients at 2–120 months posttransplant. Flow cytometry was used to assess expression of the mesenchymal markers αSMA, S100A4 and ED-A FN and HLA-DR. TGF β1 and HGF were measured in Bronchoalveolar lavage (BAL). Expression of all three mesenchymal markers was increased in BOS, as was HLA-DR. BAL HGF, but not TGF β1 was increased in BOS. Longitudinal investigation of one patient revealed a 100% increase in EMT markers concurrent with a 6-fold increase in BAL TGF β1 and the diagnosis of BOS at 17 months posttransplant.
Flow cytometric evaluation of bronchial epithelium may provide a novel and rapid means to assess lung allografts at risk of BOS.  相似文献   
78.
India contributes about 80% of the global leprosy case load including case of fresh infection and reinfection. Due to lack of gold standard, diagnosis is done mainly based on routine clinical signs and symptoms, smear and histopathological evidences. There is a lot of lacunae in early confirmatory diagnosis in terms of sensitivity and specificity, especially in paucibacillary tuberculoid type. Moreover, the classification of different classes of leprosy is very important for selection of proper therapeutic schedule. Hence this study was undertaken to develop a multiplex polymerase chain reaction for the diagnosis and strain differentiation of M leprae. A multiplex polymerase chain reaction was developed using the primers R1 and R2 (a) amplifying 372bp DNA target from a repetitive sequence of M leprae and this repetitive sequence (372bp) that was used as a target DNA for amplification was reported to be specific for M leprae was not present in 20 mycobacterium species other than M leprae and primers TTCA and TTCB (b) amplifying (201bp) DNA target of variable sizes from the regions flanking TTC repeats of M leprae genome. This multiplex polymerase chain reacton developed in our laboratory revealed that the number of repeats at each locus might be variable among M leprae but they are found mostly in multibacillary (as the bacterial load is higher in multibacillary) type.  相似文献   
79.
Objective: To analyse the influence of long‐term smoking on the hearing threshold of individuals subjected to occupational noise exposure. Design: Prospective observational cohort study. Setting: Occupational health examination of noise‐exposed employees in the brick manufacturing industry. Participants: A study group of long‐term smokers (n = 30) and a control group of non‐smokers (n = 58) were identified from a population of 227 male noise‐exposed employees. Individuals of both groups were employed for 10 years or more at a single brick manufacturing plant. Data on noise exposure, smoking habits, medical and otological history were collected and standard pure tone audiometry was obtained. Exclusion criteria included asymmetrical or conductive hearing loss, uncontrolled systemic illnesses, history of head injury, chronic middle ear pathology or major ear operations. Main outcome measure: Pure tone audiometry. Results: Both groups had similar mean age and total duration of occupational noise exposure. The median age‐corrected hearing thresholds at 3 and 4 kHz in the smokers group were significantly higher (~7dB) than those in the non‐smokers group. No statistical difference in the hearing thresholds between both groups was found in any other tested frequency (0.5, 1, 2, 6 and 8 kHz). Conclusion: Long‐term smokers with occupational noise exposure may, on the basis of this limited study, have a higher risk of developing permanent hearing loss at 3 and 4 kHz when compared with non‐smokers with a similar occupational history.  相似文献   
80.
Complications of parotid surgery: the need for selectivity   总被引:1,自引:0,他引:1  
The morbidity rate following 112 operations on the parotid gland is reported. Facial nerve palsy (temporary, 38 per cent; permanent, 9 per cent) and Frey's syndrome (11 per cent) were common following superficial parotidectomy. For pleomorphic adenoma and malignant lesions this procedure is justified. Benign conditions, which can be diagnosed preoperatively, should be treated by more limited surgery which has a lower complication rate.  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