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   697篇
  免费   68篇
  国内免费   4篇
耳鼻咽喉   9篇
儿科学   43篇
妇产科学   1篇
基础医学   110篇
口腔科学   185篇
临床医学   74篇
内科学   103篇
皮肤病学   4篇
神经病学   31篇
特种医学   6篇
外科学   34篇
预防医学   66篇
眼科学   11篇
药学   40篇
肿瘤学   52篇
  2023年   4篇
  2022年   11篇
  2021年   17篇
  2020年   17篇
  2019年   17篇
  2018年   13篇
  2017年   32篇
  2016年   22篇
  2015年   26篇
  2014年   42篇
  2013年   32篇
  2012年   54篇
  2011年   42篇
  2010年   29篇
  2009年   25篇
  2008年   41篇
  2007年   29篇
  2006年   40篇
  2005年   34篇
  2004年   17篇
  2003年   29篇
  2002年   23篇
  2001年   18篇
  2000年   15篇
  1999年   11篇
  1998年   5篇
  1997年   9篇
  1996年   11篇
  1995年   12篇
  1994年   10篇
  1993年   6篇
  1992年   19篇
  1991年   3篇
  1990年   7篇
  1989年   7篇
  1988年   9篇
  1987年   9篇
  1986年   4篇
  1985年   3篇
  1984年   6篇
  1983年   3篇
  1982年   1篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
  1959年   1篇
排序方式: 共有769条查询结果,搜索用时 15 毫秒
111.
112.
113.
Objective: This study aims to clarify demographic and clinical aspects of patients with ameloblastoma treated at a single Finnish institute during 1985–2016. Associations between predictor variables (gender and age) and outcome variables (location, tumour type, growth patterns and average tumour size) were sought.

Materials and methods: A retrospective cohort study was designed and implemented including 34 patients diagnosed with primary ameloblastoma and treated at the Helsinki University Central Hospital. Patient records were investigated, and tissue samples re-evaluated. The chi-square test was used on all categorized variables and t-test for continuous ones. A p value equal to or under .05 was considered significant.

Results: Males were slightly more predominant among the Finnish patients with ameloblastoma. Maxillary tumours were seen exclusively in male patients (p?=?.034). Additionally, these patients were older than patients with mandibular tumours (p?=?.007). A mixture in histological growth patterns was more common than originally anticipated. The study revealed a wide range of clinical signs and subjective symptoms, of which pain or other sensations were experienced most often.

Conclusions: This study of 34 subjects shows that southern Finnish patients with ameloblastoma do not substantially differ from patients in similar study designs.  相似文献   
114.
Streptomyces bacteria are renowned for their ability to produce bioactive secondary metabolites. Recently, synthetic biology has enabled the production of intermediates and shunt products, which may have altered biological activities compared to the end products of the pathways. Here, we have evaluated the potential of recently isolated alnumycins and other closely related pyranonaphthoquinone (PNQ) polyketides against Staphylococcus aureus biofilms. The antimicrobial potency of the compounds against planktonic cells and biofilms was determined by redox dye-based viability staining, and the antibiofilm efficacy of the compounds was confirmed by viable counting. A novel antistaphylococcal polyketide, alnumycin D, was identified. Unexpectedly, the C-ribosylated pathway shunt product alnumycin D was more active against planktonic and biofilm cells than the pathway end product alnumycin A, where a ribose unit has been converted into a dioxane moiety. The evaluation of the antibiofilm potential of other alnumycins revealed that the presence of the ribose moiety in pyranose form is essential for high activity against preformed biofilms. Furthermore, the antibiofilm potential of other closely related PNQ polyketides was examined. Based on their previously reported activity against planktonic S. aureus cells, granaticin B, kalafungin, and medermycin were also selected for testing, and among them, granaticin B was found to be the most potent against preformed biofilms. The most active antibiofilm PNQs, alnumycin D and granaticin B, share several structural features that may be important for their antibiofilm activity. They are uncharged, glycosylated, and also contain a similar oxygenation pattern of the lateral naphthoquinone ring. These findings highlight the potential of antibiotic biosynthetic pathways as a source of effective antibiofilm compounds.  相似文献   
115.
BACKGROUND: The characteristic feature of chronic rhinosinusitis with nasal polyposis (CRSwNP) is eosinophilic inflammation of the sinus mucosa; a type of inflammation also seen in asthmatic airways. Similar histopathologic findings of airway remodelling are present in both diseases. Remodelling is tightly controlled by matrix metalloproteinases (MMP). Increase of collagenase-2 (MMP-8) expression in the bronchial epithelial cells has been described in asthmatic patients, but it has not been studied in CRSwNP. METHODS: The concentrations and degree of activation of MMP-8 were analysed by immunofluorometric assay and Western blotting, respectively, in sinus mucus samples from CRSwNP patients and in nasal lavages from healthy controls in relation to inductive cytokines interleukin-8 (IL-8) and tumour necrosis factor-alpha (TNF-alpha). RESULTS: Significantly elevated levels of MMP-8 and IL-8 but not TNF-alpha were found in CRSwNP patients relative to controls. In particular, the activation of mesenchymal-type MMP-8 but not polymorphonuclear-type MMP-8 was associated with elevated IL-8 levels. CONCLUSIONS: The IL-8 and MMP-8 seemingly form an inductive cytokine-proteinase cascade in CRSwNP pathogenesis. Together they provide a target for novel therapies and a diagnostic tool for monitoring CRSwNP treatment.  相似文献   
116.
The purpose of this study was to determine whether other cellular sources than neutrophils can express matrix metalloproteinase (MMP)-8 protein and mRNA in bronchiectatic (BE) lung. The molecular forms of MMP-8 in the BE bronchoalveolar lavage fluid (BALF) and healthy control BALF were analysed by western immunoblotting. MMP-8 expression was demonstrated by immunohistochemistry and in situ hybridization in BE lung tissue and by immunohistochemistry in control lung tissue. In the BE BALF, different MMP-8 species were detected: 70-80 kD MMP-8 apparently of polymorphonuclear leukocyte (PMN) origin and also 40-60 kD MMP-8 from non-PMN cellular sources, such as bronchial epithelial cells, glandular cells or monocytes/macrophages. Both of these MMP-8 species were elevated and converted to a significant extent to activated forms in BE BALF compared with healthy control BALF. The levels of high molecular weight (>80 kD) MMP-8 complexes, evidently representing MMP-8 trapped by endogenous MMP inhibitors and/or MMP-8 dimers, were significantly elevated in BE BALF compared with healthy control BALF. In BE lung tissue, the MMP-8 protein and mRNA expression was found in bronchial ciliated epithelial cells, glandular cells, neutrophils, and monocytes/macrophages infiltrating the bronchial epithelial area. Minimal MMP-8 expression was observed in neutrophils, monocytes/macrophages, and epithelial cells in control lung tissues. In this study, new potential cellular sources have been demonstrated for MMP-8 in the inflamed lung. MMP-8 from multiple cellular sources, including inflamed lung epithelium, was activated to a significant extent in the BE BALF, indicating a major role for MMP-8 in the destruction of lung and bronchial tissues.  相似文献   
117.
The species Escherichia coli comprises not only non-pathogenic or commensal variants that belong to the normal intestinal flora of most mammals, but also various pathogenic strains causing diverse intestinal and extraintestinal infections in man and animals. Virulence factors and mechanisms involved in pathogenesis have been successfully analyzed for many years resulting in a wealth of knowledge about many E. coli pathotypes. However, our knowledge on the genome content, diversity and variability between pathogenic and also non-pathogenic subtypes is only slowly accumulating. Pathotypes have been largely defined by the presence or absence of particular DNA segments that in most cases appear to have been acquired via horizontal gene transfer events. As these regions are frequently subjected to excisions, rearrangements, and transfers they contribute to the previously unexpected and underestimated rapid evolution of E. coli variants resulting in the development of novel strains and even pathotypes. In these studies various novel aspects of genome diversity and plasticity in extraintestinal and intestinal pathogenic E. coli pathotypes have been addressed and the results have been directly applied for the improvement of diagnostic methods.  相似文献   
118.
MMP-8 (collagenase-2) is the most effective collagenase to initiate type I collagen degradation. Since initiation of lysis of the surrounding collagen matrix is an essential prerequisite for carcinoma cells to spread, this study investigated the expression of MMP-8 in squamous cell carcinoma (SCC) of the head and neck in vivo and in vitro. Most of the recently established head and neck carcinoma cell lines (22/25), corresponding tumour (5/7) and dermal (2/2) fibroblasts, commercial tongue carcinoma (HSC-3 and SCC-25), and transformed keratinocyte cell lines of the tongue (IHGK) and skin (HaCaT) expressed MMP-8 mRNA analysed by the PCR method. Western blotting revealed a latent 50 kD band in concentrated culture media of carcinoma cells and corresponding tumour and dermal fibroblasts. The expression of immunoreactive MMP-8 protein was reduced 30% by transforming growth factor beta-1 (TGF-beta1) at 1 ng/ml concentration and 60% at 10 ng/ml concentration, but up-regulated 2- and 2.5-fold after 10 nM and 100 nM phorbol 12-myristate 13 acetate (PMA), respectively. Immunohistological staining localized MMP-8 protein in a few malignant invading tumour cell islands, certain fibroblasts, polymorphonuclear neutrophils (PMNs), and plasma cells. In situ hybridization revealed a faint sporadic signal in carcinoma cells of all eight tissue sections analysed. It is concluded that tissue from head and neck carcinomas can express MMP-8 both in vivo and in vitro. Since the amount of MMP-8 in carcinoma and stromal cells is rather low, MMP-8 may have a potential role, with other collagenases, in the proteolysis of connective tissue associated with the spreading of invasive carcinoma.  相似文献   
119.
We related hepatic gene and serum expression of matrix metalloproteinases (MMP) and their tissue inhibitors (TIMP) to liver histology in pediatric LT recipients. Liver biopsies and serum samples were obtained from 52 patients 10.6 years post‐LT and age‐matched controls for analyses of MMPs and TIMPs. Patients with fibrosis had significantly higher hepatic gene expression of MMP‐2, MMP‐9, MMP‐14, TIMP‐1, and TIMP‐2 than patients without. Expression of these genes correlated with graft Metavir fibrosis stage (r = 0.494–0.684, P ≤ 0.006 for all). Gene expression of MMP‐1, MMP‐3, MMP‐8, TIMP‐3, and TIMP‐4 was undetectable in both patients and controls. Portal inflammation and cytokeratin 7 correlated positively with gene expression of TIMP‐1. Gene expression of MMP‐2, MMP‐9, and TIMP‐2 correlated negatively with the time of low‐dose cortisone usage (r = ?0.448 to ?0.422, P < 0.05 for all). Serum concentrations of MMP‐8 and TIMP‐1 were significantly increased and MMP‐9 decreased among patients compared with controls, but no correlations to graft histology or gene expression were observed. Hepatic gene expression of certain MMPs and TIMPs is increased in stable pediatric LT recipients displaying graft fibrosis, but this did not reflect to their serum concentrations. Increased hepatic gene expression of TIMP‐1 correlated with graft fibrosis stage, inflammation, and chronic cholestasis.  相似文献   
120.
The aim of the present observational study was to identify and characterize matrix metalloproteinase (MMP) -2, -8, -9, and -13 in gingival crevicular fluid (GCF) of patients with short root anomaly (SRA). GCF samples collected from affected maxillary central incisors and premolars of five SRA patients and five systemically and periodontally healthy controls were analysed using the zymographic technique for gelatinase A and B (MMP-2 and -9) and by Western blot for collagenase -2 and -3 (MMP-8 and -13). SRA GCF revealed MMP-9 (30 per cent of the total gelatinolytic activity), of which 18 per cent was in 90 kDa proform and 12 per cent in 71-82 kDa active form. Moreover, high-molecular weight complexes (37 per cent) and low-molecular size fragmented (33 per cent) gelatinolytic enzymes were detectable. No MMP-8 or -13 immunoreactivities existed. These results may suggest that activation and complex formation of MMP-9 is characteristic of SRA GCF. From the findings it may be assumed that the GCF of SRA teeth has low collagenolytic resorptive or pathological activity.  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