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   723篇
  免费   107篇
  国内免费   12篇
耳鼻咽喉   43篇
儿科学   48篇
妇产科学   5篇
基础医学   167篇
口腔科学   19篇
临床医学   25篇
内科学   126篇
皮肤病学   20篇
神经病学   16篇
特种医学   8篇
外科学   73篇
综合类   48篇
预防医学   18篇
眼科学   8篇
药学   21篇
中国医学   1篇
肿瘤学   196篇
  2023年   17篇
  2022年   14篇
  2021年   23篇
  2020年   44篇
  2019年   44篇
  2018年   43篇
  2017年   45篇
  2016年   21篇
  2015年   27篇
  2014年   37篇
  2013年   60篇
  2012年   23篇
  2011年   26篇
  2010年   21篇
  2009年   13篇
  2008年   18篇
  2007年   20篇
  2006年   28篇
  2005年   20篇
  2004年   31篇
  2003年   36篇
  2002年   43篇
  2001年   42篇
  2000年   23篇
  1999年   14篇
  1998年   12篇
  1997年   14篇
  1996年   8篇
  1995年   2篇
  1994年   7篇
  1992年   1篇
  1991年   2篇
  1990年   1篇
  1989年   3篇
  1988年   2篇
  1986年   1篇
  1985年   6篇
  1984年   7篇
  1983年   7篇
  1982年   6篇
  1981年   6篇
  1980年   3篇
  1979年   4篇
  1978年   4篇
  1977年   2篇
  1976年   1篇
  1975年   3篇
  1974年   1篇
  1973年   4篇
  1971年   2篇
排序方式: 共有842条查询结果,搜索用时 15 毫秒
41.
Lymphocytic interstitial pneumonitis (LIP) in children has been most commonly associated with human immunodeficiency virus (HIV) infection. Epstein-Barr virus (EBV) associated LIP without HIV infection has been reported only in adults. EBV associated LIP has been reported in children, but only with concurrent HIV infection. We report a case of EBV associated, HIV negative LIP in a child.  相似文献   
42.
The SH2 domain containing SH2D1A protein has been characterized in relation to the X-linked lymphoproliferative disease (XLP), a primary immunodeficiency that leads to serious clinical conditions after Epstein-Barr virus (EBV) infection. The SH2D1A gene is mutated in the majority of XLP patients. We previously detected SH2D1A in activated T and NK cells, but not in B lymphocytes. We have found SH2D1A protein in Burkitt lymphoma (BL) lines, but only in those that carried EBV and had a Group I (germinal center) phenotype. All the EBV-carrying Group III (immunoblastic) and the EBV-negative BL lines tested were SH2D1A-negative. Motivated by these differences, we studied the impact of EBV and the cellular phenotype on SH2D1A expression. We approached the former question with BL sublines after both the loss of the virus and subsequent reinfection. We also tested original EBV-negative BL lines carrying transfected EBV genes, such as EBNA1, EBNA2, EBNA6, EBER1, 2 and LMP1, respectively. In our experiments, no direct relationship could be seen between EBV and SH2D1A expression. We modified the phenotype of the Group I BL cells by LMP1 transfection or CD40 ligation. The phenotypic changes, indicated by expression of immunoblastic markers, e.g., SLAM, were accompanied by downregulation of SH2D1A. It seems, therefore, that the presence of EBV and the phenotype of the cell together regulate SH2D1A expression in the BL cells. It is possible that SH2D1A is expressed in a narrow window of B cell development represented by germinal center cells.  相似文献   
43.
①目的建立EB病毒感染的人胃上皮细胞细胞株,并进行鉴定。②方法将舍有NEOr基因的重组EBV感染人胃上皮细胞GES-1.同时以pcDNA3(NEOr)空载体质粒经脂质体法持染同一细胞为对照,用有限稀释法进行克隆,经G418筛选,用免疫荧光组织化学法鉴定EBV编码的核抗原1(EBNA1)的表达情况,直至获得100%表达EBV的单克隆细胞株。③结果感染EBV的GES-1细胞大部分为EBNA1阳性,而转染pcDNA3(NEOr)空载体质粒的GES-1细胞均为EBV阴性。(蓟结论成功地建立EB病毒感染的人胃上皮细胞GES-1细胞株,对EB病毒致胃癌机制的研究具有重要的意义。  相似文献   
44.
应用PCR技术和免疫组化SP法检测了46例鼻咽癌组织中EB病毒DNA、EB病毒潜在膜蛋白(LMP-1)的表达。结果发现EB病毒DNA检出率和LMP-1的表达率分别为80.4%和53.3%,EB病毒DNA检出率和LMP-1表达与鼻咽癌组织学分级有关。提示EB病毒NDA的存在和LMP-1表达与细胞癌变关系密切  相似文献   
45.
Objective: The present study has been carried out to analyse the trend of heterophile antibody positive infectious mononucleosis cases.Methods: A total of 1741 cases of clinically suspected infectious mononucleosis from various age groups were investigated during the period January, 1986 to December, 2000 and were analysed for infectious mononucleosis (IM) specific heterophile antibody by Paul-Bunnel-Davidsohn (PBD) test. Forty seven heterophile antibody negative samples were also tested simultaneously for the presence of the IgG antibody to viral capsid antigen (VCA) and Epstein Barr nuclear antigen (EBNA) to detect the exposure to Epstein Barr Virus (EBV) infection.Results : The overall percentage of EBV specific heterophile (Paul-Bunnel) antibody positivity was found to be 11.1 % (194/1741). The average Paul-Bunnel antibody positivity between 1986 to 1990 was 20.5% which declined drastically to 5.7% during 1991-2000. Males comprised of 55.2% of the serologically proven IM cases. Of the 47 heterophile antibody negative cases, 38 (80.9%) and 33 (70.2%) were found to be positive for anti-VCA IgG and anti-EBNA IgG antibodies respectively. Paul Bunnel antibody positivity was found to be higher in > 14 year5 age group patients than those below 14 years.Conclusion : These findings suggest that the EBV infection still continues to be endemic in this part of the country, however, a declining trend in IM cases was observed during the last decade.  相似文献   
46.
Pai PC  Tsang NM  Tseng CK  Hao SP  Kuo TT  Wei KC  Hsueh C  Chuang CC 《Head & neck》2004,26(7):619-624
BACKGROUND: The purpose of this study was to investigate the frequency of Epstein-Barr virus (EBV) latent membrane protein-1 (LMP-1) in tonsils and non-neoplastic nasopharynxes in Taiwan. METHODS: Nest-polymerase chain reaction (nest-PCR) was used to examine the presence of LMP-1 gene in lymphoid hyperplasia from non-neoplastic tonsillar and nasopharyngeal tissues and in tonsillar cancers. RESULTS: In 152 cases, 64 biopsy tissues were obtained from lymphoid hyperplasia of nasopharynxes, 57 from tonsillectomy of non-neoplastic tonsils, and 31 from tonsillar cancers. LMP-1 was detected in 43.4% of the study group. Nineteen (29.7%) and 29 (50.9%) lymphoid hyperplasias from normal nasopharynxes and tonsils, respectively, and 18 (58.1%) biopsies from tonsillar cancers had positive LMP-1. The 30-base pair (bp) deleted variant was detected in 89.5% and 82.8% of normal nasopharynxes and tonsils, respectively, and in 66.7% of biopsies from tonsillar cancers (p =.198). CONCLUSION: This study found that the 30-bp variant was the predominant type of LMP-1 from a healthy population in Taiwan.  相似文献   
47.
Chronic active Epstein-Barr virus (EBV) infection is a chronic mononucleosis syndrome associated with clonal proliferation of EBV-carrying T-/natural killer (NK)-cells. High levels of circulating EBV and activated T-cells are sustained during the prolonged disease course, whereas it is not clear how ectopic EBV infection in T-/NK-cells has been established and maintained. To assess the biological role of activated T-cells in chronic active EBV infection (CAEBV), EBV DNA and cellular gene expressions in peripheral T-cells were quantified in CAEBV and infectious mononucleosis (IM) patients. In CAEBV, HLA-DR(+) T-cells had higher viral load and larger amounts of IFN gamma, IL-10, transforming growth factor-beta (TGF beta), and cytotoxic T lymphocyte antigen-4 (CTLA4) mRNA than HLA-DR(-)T-cells. HLA-DR(+) T cells of IM patients transcribed more IFN gamma and IL-10 than their HLA-DR(-)T cells. Expression levels of IFN gamma and forkhead box p3 (Foxp3) in CAEBV HLA-DR(+) T-cells were higher than in IM HLA-DR(+) T-cells. The effective variables to discriminate the positivity of HLA-DR were IL-10, IFN gamma, CTLA4, TGF beta, and IL-2 in the order of statistical weight. EBV load in CAEBV T-cells correlated with the expression levels of only IL-10 and TGF beta. These results suggest that CAEBV T-cells are activated to transcribe IFN gamma, IL-10, and TGF beta excessively, and the latter two genes are expressed preferentially in the EBV-infected subsets. The dominant expression of regulatory cytokines in T-cells may imply a viral evasion mechanism in the disease.  相似文献   
48.
Hao SP  Tsang NM  Chang KP 《The Laryngoscope》2004,114(11):2027-2030
OBJECTIVES: Epstein-Barr virus (EBV) is closely related to nasopharyngeal carcinoma (NPC). Detection of EBV genomic DNA in a nasopharyngeal swab specimen may indicate the presence of NPC, and the EBV genomic DNA is only detected in patients with NPC and not in other head and neck cancers. This study aims to prove that detection of EBV genomic DNA by means of the latent membrane protein (LMP)-1 gene and the Epstein-Barr nuclear antigen (EBNA)-1 gene in the nasopharynx in NPC patients after radiation therapy indicates local recurrence of NPC. STUDY DESIGN: Prospective. METHODS: Nasopharyngeal swab with polymerase chain reaction (PCR)-based LMP-1 and EBNA-1 gene detection was used to monitor local recurrence in 84 NPC patients who completed radiation therapy. RESULTS: Of the 12 patients demonstrating positive LMP-1 and EBNA-1 gene, 11 had local recurrence, and 10 of them had early rT1 mucosal recurrence. Subsequent salvage nasopharyngectomy controlled local disease in nine. Only one local recurrence in the skull base failed to show LMP-1 gene initially. Detection of LMP-1 gene and later verification with EBNA-1 gene from nasopharyngeal swabs in NPC patients after radiation therapy predicted local recurrence with a sensitivity of 91.7% and a specificity of 98.6%. CONCLUSIONS: Nasopharyngeal swab with LMP-1 and EBNA-1 gene detection is a useful and reliable method to monitor local recurrence in NPC patients. It helps to detect recurrence early and may improve local control and enhance survival.  相似文献   
49.
In developing countries, BL has a strong association with EBV infection during childhood. In South America, the data have shown an EBV association intermediate between that reported in the United States (30%) and that in equatorial Africa (95%). Early age at EBV infection and lower socioeconomic status have been related to increased EBV-associated BL in developing countries. In Brazil, there are not enough data on childhood BL related to EBV infection. Our aim was to evaluate the clinicopathologic features and EBV association of 44 children with NHL from the state of Rio de Janeiro, situated in the southeast of Brazil. EBV was detected using RNA in situ hybridization in 36 biopsy specimens. DNA from fresh tumor samples and from paraffin-embedded tissues of patients were analyzed by PCR, in which the first reaction included primers for an EBNA-2 common region while the nested reaction amplified the region discriminating between EBV types 1 and 2 in separate reactions. EBV was detected in 21 of 29 BLs (72%), and type 1 virus infected the majority of EBV-positive BLs (18/21). There was a trend for younger age in children with EBV-positive BL compared to EBV-negative BL (median age 4 compared to 6 years, respectively; p = 0.056). Our study confirmed that in the southeast of Brazil BL had an intermediate association with EBV. A higher rate of EBV-associated BL was described in the northeast of Brazil. These differences are probably related to regional socioeconomic status. In conclusion, our study suggests that early infection with EBV in the background of a low socioeconomic condition associated with other environmental factors could contribute to BL in Brazil.  相似文献   
50.
Epstein-Barr virus (EBV) is present within the tumor cells of most cases of nasopharyngeal carcinoma (NPC). Recent studies suggest that tumor burden is proportional to the level of EBV DNA in blood and that rapid blood testing can be used to guide therapeutic intervention. The relative utility of viral load vs. serology has been insufficiently studied. In our study, EBV viral load was measured by quantitative PCR using either real-time or end-point detection systems in serum samples from 124 NPC patients (93 pretreatment, 13 relapsed, 18 in remission) and 40 controls. Serologic titers against EBV early antigen were measured in the same serum samples. EBV DNA was detectable in 64 of 93 untreated NPC patients (69%; mean viral load 11,211 copies/ml), 11 of 13 relapsed NPC patients (85%; mean 53,039 copies/ml) and 0 of 18 remission patients. EBV DNA was detectable in only 1 of 40 non-NPC controls (3%). In 34 instances where paired plasma and serum samples were available for testing, both were effective sample types, and there was no significant difference between end-point and real-time methods for measuring viral load. Early antigen (EA) IgA and IgG titers were elevated in most NPC patients regardless of whether their disease was active or in remission. EBV viral load was more informative than was EA serology for distinguishing remission from relapsed disease. EBV DNA measurement appears to be a noninvasive way to monitor tumor burden after therapy.  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