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   1566篇
  免费   133篇
  国内免费   12篇
耳鼻咽喉   14篇
儿科学   38篇
妇产科学   20篇
基础医学   232篇
口腔科学   39篇
临床医学   146篇
内科学   381篇
皮肤病学   13篇
神经病学   83篇
特种医学   51篇
外科学   231篇
综合类   70篇
预防医学   116篇
眼科学   83篇
药学   108篇
  1篇
中国医学   20篇
肿瘤学   65篇
  2023年   26篇
  2022年   44篇
  2021年   65篇
  2020年   40篇
  2019年   62篇
  2018年   52篇
  2017年   32篇
  2016年   64篇
  2015年   54篇
  2014年   66篇
  2013年   90篇
  2012年   137篇
  2011年   129篇
  2010年   83篇
  2009年   56篇
  2008年   91篇
  2007年   75篇
  2006年   72篇
  2005年   76篇
  2004年   75篇
  2003年   55篇
  2002年   40篇
  2001年   33篇
  2000年   30篇
  1999年   22篇
  1998年   13篇
  1997年   6篇
  1996年   7篇
  1995年   4篇
  1994年   5篇
  1993年   6篇
  1992年   8篇
  1991年   6篇
  1990年   6篇
  1989年   2篇
  1988年   7篇
  1987年   7篇
  1986年   4篇
  1985年   8篇
  1984年   5篇
  1983年   2篇
  1982年   4篇
  1981年   2篇
  1980年   7篇
  1979年   5篇
  1978年   7篇
  1975年   3篇
  1974年   3篇
  1972年   3篇
  1970年   3篇
排序方式: 共有1711条查询结果,搜索用时 15 毫秒
121.
122.
123.
Ankylosing spondylitis (AS) is a chronic inflammatory disease, characterized by axial arthritis in which the genetic-environmental factors seem to be involved in the pathogenesis of the disease. This study was performed to investigate the role of polymorphisms of the programmed cell death 1 (PDCD1) gene on susceptibility to AS. In this study, 161 Iranian patients with AS and 208 normal controls were enrolled; two single-nucleotide polymorphisms (SNPs) of the PDCD1 gene PD-1.3 (G, A) in nucleotide position +7146 of intron 4 and PD-1.9 (C, T) in nucleotide +7625 of exon 5 were studied. Analysis of PD-1.3 revealed that 82% of patients and 79% of controls had GG genotype, while GA and AA genotypes were detected in 17% and 0.6% of patients, respectively, and 20% and 1.4% of controls, respectively. Moreover, the genotype CC (PD-1.9) was present in 92% of patients and 97% of controls. Although these differences were not statistically significant between patients and controls, comparisons of genotypes frequencies in the AS patients, based on human leukocyte antigen (HLA)-B27, revealed that all patients who had CT genotype (PD-1.9) were HLA-B27 positive, whereas 30% of patients with CC genotype were HLA-B27 negative. There was no evidence of association for PDCD1 SNPs with AS in our study, but CT genotype (PD-1.9) seems to be associated with HLA-B27 positivity in the patients with AS.  相似文献   
124.
To the editor: WANG and his colleagues provided the evidence that "both melanopsin-containing and super/or collicular retinal ganglion cells were damaged by chronic ocular hypertension, indicating that glaucomatous neural degeneration involves the non-image-forming visual pathway") These cells as the authors have beautifully described dealing with a variety of functions including biological clock; pupillary light reaction and they are affected by glaucoma. The report is scientific and quite interesting. I would like to congratulate the authors for their superb studies.  相似文献   
125.
Neuronal Specific Increase of Phosphatidylserine by Docosahexaenoic Acid   总被引:1,自引:0,他引:1  
Phosphatidylserine (PS), the major acidic phospholipid class in eukaryotic biomembranes, plays an important role in various signaling pathways. We have previously demonstrated that docosahexaenoic acid (DHA, 22:6n-3) positively modulates PS biosynthesis and accumulation in neuronal cells, promoting survival. In this paper, we demonstrate that the increase of PS levels upon DHA enrichment is not a universal mechanism, but specific to neuronal cells. When cells were enriched with 20 muM DHA, 18:0, 22:6-PS increased in both neuronal (Neuro 2A) and non-neuronal cells (Chinese hamster ovary K1 cells, NIH-3T3, and human embryonic kidney cells). However, the increase of the total PS level was observed only in Neuro 2A cells because of the fact that other PS species, such as 18:0, 18:1-PS and 18:1, 18:1-PS decreased significantly in non-neuronal cells, compensating for the increase of 18:0, 22:6-PS. DHA enrichment did not affect the messenger RNA levels of PS synthase 1 (PSS1) and PSS2. Over-expression of genes encoding PSS1 or PSS2 altered neither the PS level nor the effect of DHA on PS increase in both neuronal and non-neuronal cells. From these results, it is concluded that the PS increase by DHA, specifically observed in neuronal cells, may represent a unique mechanism for expanding the PS pool so far known in mammalian cells.  相似文献   
126.
A 38-year-old Ghanaian man presented with a 6-month history of worsening pruritus, jaundice, and ascites. He was previously fit and well and rarely drank alcohol. Screening tests for chronic liver disease including viral, autoimmune, and other metabolic causes including iron overload were unremarkable. A liver biopsy performed at the referring hospital demonstrated intralobular cholestasis and cirrhosis. He was listed for liver transplantation but subsequently developed sepsis with multiple organ failure and died. The sickle solubility test was positive. Blood smear showed cells consistent with liver failure and no sickle cells. Hemoglobin electrophoresis revealed HbA2 2.8%, HbF 0.5%, and HbS greater than HbA (49.6% vs. 41.3%) in the absence of blood transfusion. Sequence analysis of the beta-globin genes showed he was a compound heterozygote for the Hbs mutation at codon 6 (CAG --> GTG) and a novel mutation at position 844 of intron 2 (betaIVS2-844 C --> A). A diagnosis of sickle hepatopathy causing decompensated cirrhosis was made. This case is unusual insomuch as this patient was asymptomatic for over 35 years and represents a novel presentation of sickle cell disease. Sickle cell disease should be considered in appropriate patients when unusual presentations of liver disease arise.  相似文献   
127.
Between November 2001 and September 2004, 80 patients aged 11 to 56 years (mean, 27.6 years) underwent the Ross operation. The mean preoperative New York Heart Association functional class was 2.37 +/- 0.72, and the mean ejection fraction was 52.8% +/- 16%. Aortic involvement included stenosis in 19 (24%) patients, regurgitation in 22 (28%), and both in 39 (49%). Root replacement was the technique used in all cases. The mean hospital stay was 5 days, and 74 patients (93%) were followed up for 4-48 months. Four-year actuarial survival rate was 96.25%. Postoperative echocardiography revealed no pulmonary autograft insufficiency in 50 patients (63%), trivial to mild insufficiency in 22 (28%), moderate insufficiency in 2 (3%), and severe insufficiency in one (1%). Two patients required autograft re-intervention. Postoperative echocardiography of the pulmonary homograft valve showed severe stenosis (peak gradient > 50 mm Hg) in 2 patients, and moderate stenosis (peak gradient 25-50 mm Hg) in one. The mean postoperative left ventricular ejection fraction was 51.4%. The Ross operation can be considered an elegant alternative to prosthetic valves in the treatment of aortic valve diseases in developing countries.  相似文献   
128.
Barbarian A  Karbakhsh M 《Urology journal》2007,4(3):187; discussion 187-187; discussion 188
  相似文献   
129.
Introduction  Pemphigus vulgaris (PV), an autoimmune disease affecting the skin and mucous membranes, is associated with some human leukocyte antigen (HLA) class II alleles and haplotypes. Materials and Methods  In order to evaluate the association of HLA-DR and DQ alleles and haplotypes in Iranian non-Jewish patients with PV, 52 patients with PV and 180 normal subjects as control group were investigated in this study. Results and Discussion  HLA-DRB1*04, -DRB1*1401, -DRB4, -DQA1*0104, -DQA1*03011, -DQB1*0302, and -DQB1*0502 alleles have been significantly increased in our patients group. Moreover, the haplotypes HLA-DRB1*04/-DQA1*03011/-DQB1*0302 and HLA-DRB1*1401/-DQA1*0104/-DQB1*0502 increased significantly in our patients. In contrast, the following alleles decreased significantly in our patients: HLA-DRB1*15, -DRB1*0301, -DRB1*07, -DRB1*11, -DRB5, -DQA1*0101, -DQA1*0103, -DQA1*201, -DQA1*05, -DQB1*0201, -DQB1*0301, -DQB1*06011, and -DQB1*0602. In addition, HLA-DRB1*15/-DQA1*0103/-DQB1*06011, HLA-DRB1*0301/-DQA1*05011/-DQB1*0201, HLA-DRB1*07/-DQA1*0201/-DQB1*0201, and HLA-DRB1*11/-DQA1*05/-DQB1*03011 decreased significantly in our patients. Genetic factors are involved in the occurrence of PV; HLA-DRB1*04 and -DRB1*1401 alleles and the related haplotypes are suggestive to be two major PV susceptibility factors in our population study.  相似文献   
130.
Introduction  Asthma is one of the most common respiratory diseases caused by acute and chronic inflammation of airways. Proinflammatory cytokines could contribute to this inflammatory process. This study was performed in order to analyze the genetic profile of proinflammatory cytokines in Iranian asthmatic patients. Patients and Methods  The allele and genotype frequencies of a number polymorphic genes coding for tumor necrosis factor (TNF)-α, interleukin (IL)-1α, IL-1β, IL-1 receptor (IL-1R), IL-1RA, and IL-6 were investigated in 60 patients with asthma in comparison with 140 controls using polymerase chain reaction with sequence-specific primers. Results  The most frequent genotypes in our patients were TNF-α GA at position −308 (P = 0.001), TNF-α AA at position −238 (P = 0.01), IL-1α TC at position −889 (P = 0.0001), IL-1β TC at position −511 (P = 0.0001), and IL-1RA TC at position Mspa-I 11100 (P = 0.001). In contrast, the frequencies of the genotypes TNF-α GG at position −308 (P = 0.001), IL-1α CC at position −889 (P = 0.005), IL-1β CC at position −511 (P = 0.0001), and IL-1RA TT at position Mspa-I 11100 (P = 0.0001) in the patient group were significantly lower than controls. The most frequent haplotypes for TNF-α (positions 308, −238) was A/A in the patient group in comparison with controls (P = 0.0001). Conclusion  While environmental factors are important in the development of asthma, genetic factors could have a critical role in the expression of the disease. Considering the high frequency of presence of TNF-α AG genotype (−308), it seems that the production of TNF-α in the asthmatic patients could be higher than normal subjects.  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