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   3044篇
  免费   213篇
  国内免费   13篇
耳鼻咽喉   32篇
儿科学   80篇
妇产科学   79篇
基础医学   515篇
口腔科学   262篇
临床医学   318篇
内科学   621篇
皮肤病学   40篇
神经病学   316篇
特种医学   30篇
外科学   192篇
综合类   19篇
一般理论   2篇
预防医学   331篇
眼科学   48篇
药学   196篇
中国医学   14篇
肿瘤学   175篇
  2024年   8篇
  2023年   53篇
  2022年   97篇
  2021年   170篇
  2020年   111篇
  2019年   122篇
  2018年   123篇
  2017年   94篇
  2016年   117篇
  2015年   109篇
  2014年   136篇
  2013年   162篇
  2012年   270篇
  2011年   308篇
  2010年   168篇
  2009年   124篇
  2008年   222篇
  2007年   181篇
  2006年   185篇
  2005年   162篇
  2004年   107篇
  2003年   93篇
  2002年   75篇
  2001年   13篇
  2000年   6篇
  1999年   14篇
  1998年   8篇
  1997年   4篇
  1996年   6篇
  1995年   5篇
  1994年   3篇
  1993年   3篇
  1992年   1篇
  1991年   2篇
  1990年   1篇
  1989年   3篇
  1986年   1篇
  1985年   1篇
  1983年   1篇
  1974年   1篇
排序方式: 共有3270条查询结果,搜索用时 31 毫秒
61.
Forensic Toxicology - We have developed and validated a high-sensitivity method to quantify lysergic acid diethylamide (LSD) and 2-oxo-3-hydroxy-LSD (OH-LSD) in oral fluid samples using...  相似文献   
62.
Interactions between killer immunoglobulin-like receptors (KIRs) and human leukocyte antigen (HLA) class I ligands influence development of natural killer (NK) cell repertoire and response to infection, cancer, and allogeneic tissue. As KIRs and HLA class I molecules are highly polymorphic, clinical allogeneic hematopoietic cell transplantation is predicted to frequently involve KIR mismatch, and thus to provide a unique system for study of human NK cell receptor repertoire development. Eighteen leukemia patients undergoing HLA-matched transplantation and their donors were analyzed for KIR genotype. Ten of 13 HLA-identical donor-patient pairs were KIR mismatched and 3 were matched; all HLA-matched unrelated pairs were KIR mismatched. Reconstitution of recipient NK cell repertoire following transplantation was examined using flow cytometry and monoclonal antibodies specific for KIR and CD94:NKG2A. These data form 3 groups. Six to 9 months after transplantation, 8 patients (group 1) reconstituted an NK cell repertoire resembling that of their donor, and for KIR-mismatched transplants, distinct from the recipient before transplantation. In the first year after transplantation, 5 patients (group 2) exhibited a generally depressed frequency of KIR-expressing NK cells and concomitant high frequency of CD94:NKG2A expression. By 3 years after transplantation, the frequency of KIR-expressing NK cells had increased to donor values, in the 3 patients from group 2 analyzed for this period. The remaining 5 patients experienced severe clinical complications following transplantation and displayed unique features in their NK cell receptor reconstitution. These results demonstrate that a majority of HLA-matched hematopoietic cell transplantations involve KIR mismatch and reveal differences in NK cell repertoire having potential impact for immune responsiveness and transplantation outcome.  相似文献   
63.
BACKGROUND: Barrett's esophagus is a well-known pre-malignant condition. Pathologic interpretation of biopsy specimens guides endoscopic surveillance as well as the therapeutic approach that will be carried out. However, the predictive value of histopathologic diagnosis can be questioned due to its poor intra- and interobserver reproducibility. AIMS: To assess intra- and interobserver variability in the diagnosis of Barrett's dysplasia. MATERIAL AND METHODS: Three-micrometer thick sections from biopsy specimens from 42 patients with Barrett's esophagus were stained with hematoxylin-eosin and PAS-alcian blue. The reading of the slides was carried out blindly in a light microscope. Intra and interobserver variability in the interpretation of the slides was determined by kappa statistics. RESULTS: The number of tissue specimens was 229, with average of 5.45 (1 to 18) fragments for patient. Low grade dysplasia was diagnosed by pathologists in 21.4% to 52.4% of the cases. The intra-observer agreement for the diagnosis of low grade dysplasia was slight (kappa = 0.30). The interobserver agreement for the diagnosis of low grade dysplasia was poor, with kappa scores between 0.05 and 0.16. The diagnosis of dysplasia, with agreement for all pathologists examining the same set of slides, was 14.3%. CONCLUSIONS: Pathologic interpretation of Barrett's dysplasia may be subject to marked intra- and interobserver variabiliaty. Interpretation of low grade dysplasia, as high grade dysplasia, should also be considered for review by two or more pathologists.  相似文献   
64.
Dendritic cells (DCs) play an important role in inducing immune tolerance. Inhibitory receptors, such as ILT2/CD85j, are involved in the tolerogenic effect of DCs and previous studies have indicated the important role of these receptors on the pathogenesis of autoimmune diseases. The aim of this study was to evaluate the expression and function of ILT2 in DCs from SLE patients. Peripheral blood from fifty patients with SLE and 38 healthy volunteers was obtained. ILT2 expression was assessed by flow cytometry. DCs were generated in the absence or presence of an anti-ILT2 antibody. The effect of ILT2 in the immunogenic ability of SLE DCs was also evaluated. We observed that SLE patients had significant higher levels of circulating plasmacytoid DCs (pDCs), and that these levels correlated with disease activity. In contrast, the expression of ILT2 was diminished in both pDCs and myeloid DCs (mDCs) from these patients. However, under our experimental conditions, the in vitro differentiation of DCs was not apparently affected by ILT2 engagement. In contrast, the immunogenic capability of monocyte-derived DCs was not down-regulated by ILT2 cross-linking in a significant proportion of SLE patients. Our results suggest that ILT2 participates in the defective immune-regulation observed in patients with SLE.  相似文献   
65.
Activating and inhibitory killer immunoglobulin‐like receptors (KIR) and their ligands HLA‐Bw4 (loci A and B) were studied by way of establishing whether they can contribute to protection against HIV‐1 infection in highly exposed and persistently seronegative (HESN) patients. Twenty‐three HIV‐1 serodiscordant heterosexual couples, 100 HIV‐1+ patients and 200 healthy individuals were included in this retrospective case–control study. HLA typing was performed by means of PCR followed by sequence‐specific oligonucleotide probe reverse hybridization. KIR3DL1 and KIR3DS1 were studied by PCR sequence‐specific primers. The frequency of KIR3DS1(3DS1/3DL1)‐Bw4 combination was significantly higher in HESN patients versus the discordant couples (P = 0·0003) and HIV‐1+ patients (P = 0·0001). Conversely, the KIR3DL1/KIR3DL1 homozygosity was significantly decreased in HESN patients versus the discordant couples (P = 0·00003), and HIV‐1+ patients (P = 0·00066). The frequency of HLA‐A*32 and HLA‐B*44 was higher in HESN versus their discordant couples (P = 0·009; P = 0·049), and HIV‐1+ patients (P = 0·00002; P = 0·0001). This had greater significance in combination with KIR3DS1 (3DS1/3DL1). KIR3DS1(3DS1/3DL1) could have a greater effect on protection against HIV‐1 infection in HESN patients when bound to a specific HLA allele, in this case HLA‐A*32 and HLA‐B*44, both Bw4 alleles. The differences probably arise both in the HLA alleles and in the subtypes of KIR receptors depending on the ethnic group studied.  相似文献   
66.
Journal of NeuroVirology - This study aims to characterize the acute neurological manifestations caused by DENV, ZIKV, and YFV during hospitalization; identify the risk factors associated with...  相似文献   
67.
68.
69.
70.
BackgroundAllergic rhinitis (AR), allergic conjunctivitis (AC), and asthma composing multiple phenotypes and improved understanding of these phenotypes and their respective risk factors are needed.ObjectivesThe objective of this study was to define the prevalence of AR, AC, and asthma and their association with allergen‐specific immunoglobulin E (sIgE) sensitization in a large cohort of blood donors and identify risk factors.MethodsFrom the nationwide population‐based Danish Blood Donor Study, 52,976 participants completed an electronic questionnaire including AR, AC, asthma, allergic predisposition, and childhood residence. Of these, 25,257 were additionally tested for sIgE to inhalation allergens (Phadiatop).ResultsThe prevalence of sIgE sensitization, AR, AC, and asthma was 30%, 19%, 15%, and 9%, respectively. The youngest birth cohorts had the highest prevalence of sIgE sensitization and symptoms of asthma, AR, and AC, and for asthma, they apparently experienced symptoms at an earlier age. The sIgE sensitization was positively associated with male sex. The sIgE seroprevalence was higher in participants with both AR and AC (ARC) than in participants with either AR or AC. Allergic predisposition and sIgE sensitization increased the risk of the diseases, while farm upbringing was associated with reduced prevalence of ARC, however, only in sIgE sensitized participants.ConclusionBirth year, childhood residence, sIgE sensitization, and allergic predisposition were associated with asthma, AR, and AC prevalence. Individuals with self‐reported ARC represent a primarily sIgE‐positive phenotype, while those with either AR or AC represent more diverse phenotypes.  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