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   6427篇
  免费   1256篇
  国内免费   236篇
耳鼻咽喉   38篇
儿科学   210篇
妇产科学   72篇
基础医学   1121篇
口腔科学   112篇
临床医学   806篇
内科学   1172篇
皮肤病学   155篇
神经病学   522篇
特种医学   87篇
外科学   427篇
综合类   897篇
现状与发展   1篇
预防医学   775篇
眼科学   234篇
药学   456篇
  1篇
中国医学   157篇
肿瘤学   676篇
  2024年   25篇
  2023年   136篇
  2022年   282篇
  2021年   345篇
  2020年   281篇
  2019年   368篇
  2018年   422篇
  2017年   483篇
  2016年   468篇
  2015年   419篇
  2014年   569篇
  2013年   500篇
  2012年   452篇
  2011年   453篇
  2010年   318篇
  2009年   266篇
  2008年   254篇
  2007年   242篇
  2006年   232篇
  2005年   193篇
  2004年   177篇
  2003年   182篇
  2002年   163篇
  2001年   115篇
  2000年   103篇
  1999年   70篇
  1998年   70篇
  1997年   54篇
  1996年   30篇
  1995年   26篇
  1994年   28篇
  1993年   23篇
  1992年   25篇
  1991年   16篇
  1990年   14篇
  1989年   15篇
  1988年   18篇
  1987年   6篇
  1986年   9篇
  1985年   15篇
  1984年   10篇
  1983年   8篇
  1982年   4篇
  1981年   8篇
  1980年   3篇
  1979年   10篇
  1978年   3篇
  1977年   4篇
  1976年   2篇
排序方式: 共有7919条查询结果,搜索用时 0 毫秒
11.
Frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP‐17) is a hereditary progressive neurodegenerative disorder. FTDP‐17 was originally defined in Ann Arbor, Michigan, in 1996. Since then, more than 100 families with FTDP‐17 have been described throughout the world, including 18 families identified in Japan. Genetic studies have identified 40 different mutations in the microtubule‐associated protein tau (MAPT) gene. The clinical features of FTDP‐17 are characterized by behavioral, cognitive and motor disturbances that may occur in various combinations and degrees. Neuropathologic examination shows that various degrees of atrophy may be present in the frontal and temporal lobes, basal ganglia, amygdala and hippocampus. All the brains from patients with FTDP‐17 have also shown the presence of tau deposits in neurons and glial cells. Mutations in MAPT may result in the increased splicing of exon 10, leading to 4‐repeat tau depositions in both neurons and glial cells. MAPT mutations outside of exon 10 show 3‐ and 4‐repeat tau deposits, predominantly in neurons with less glial pathology. Neuronal pathology may resemble that of Alzheimer’s disease or Pick’s disease because of the presence of neurofibrillary tangles or Pick‐like bodies, whereas glial pathology may resemble that of progressive supranuclear palsy or corticobasal degeneration because of the presence of coiled bodies, tufted astrocytes or astrocytic plaques. Correlations between genetic mutations and the heterogeneity of clinical and neuropathologic features remain unclear.  相似文献   
12.
应用银染技术,对24例结肠腺癌Ⅱ级不典型增生,30例绒毛状腺瘤,14例绒毛状腺瘤Ⅲ级不典型增生和29例高分化管状腺癌进行银染核仁形成区嗜银蛋白(Ag-NORs)定量研究,观察Ag-NORs数量、形态、大小和分布在结肠肿瘤交界性病变中的表达.提示Ag-NORs四项指标定量研究对结肠脉瘤,特别是Ⅲ级不典型增生与绒毛状腺瘤之结肠癌前病变有较好的监测作用.  相似文献   
13.
BACKGROUND: Classification of patients with chronic whiplash associated disorders (WAD) into homogenous subgroups is an important objective in order to tailor interventions and to control for subgroup differences when evaluating treatment outcome. AIMS: The aims of this study were to investigate if it was possible to replicate and describe the three cluster solution and profiles found in other pain groups and describe cluster profiles based on self-reported Multidimensional Pain Inventory-scores for patients with WAD three months after the injury, describe characteristics of the clusters in relation to disability, self-efficacy and coping at the same point in time and to validate the cluster solution by comparing clusters in disability, self-efficacy and coping over time. METHODS: Ninety-one WAD-patients three months after the accident took part in the study. The measures used were the Multidimensional Pain Inventory-Swedish version (MPI-S), The Self-Efficacy Scale, The Coping Strategies Questionnaire and The Pain Disability Index. Cluster analysis was conducted for the total sample MPI-S subscale scores. RESULTS: The adaptive copers cluster represented 42% of the sample, dysfunctional 34% of the sample, and interpersonally distressed 24% of the sample. The external validation of cluster solution showed that there were several significant differences between clusters in self-efficacy, disability and coping measures. There was also a significant interaction effect (clusterxtime) in disability (PDI). Patients in dysfunctional cluster reported a decreased disability over time. CONCLUSIONS: These results support the presence of different subgroups among patients with whiplash associated disorders. This classification can be seen as a complement to a classification based on medical condition.  相似文献   
14.
生长抑素受体显像近年来研究较多,depreotide已成为其研究热点之一。Depreotide在诊断与鉴别诊断临床常见的孤立性肺结节方面有其独特优势;此外,^99mTc—depreotide生长抑素受体显像在乳腺癌、甲状腺癌、淋巴瘤等肿瘤及甲状腺相关性眼病等非肿瘤性疾病也有一定应用前景。  相似文献   
15.
目的构建重组人骨形态发生蛋白7(hBMP7)的腺相关病毒(AAV)载体。方法通过RT-PCR方法,从HEK293细胞中扩增hBMP7全长cDNA并亚克隆入通用型AAV载体质粒pSNAV。将pSNAV-hBMP7质粒DNA转染BHK-21细胞,筛选出携带hBMP7的AAV载体细胞株—BHK-21细胞。用能表达Rap和Cap的重组1型单纯疱疹病毒HSV1-rc/ΔUL2按MOI=0·1感染BHK-21载体细胞株后收获病毒液,通过氯仿—PEG/NaCl沉淀—氯仿抽提纯化病毒。结果所克隆的hBMP7全长cDNA经测序证实和已知hBMP7序列完全一致。通过用能表达Rap和Cap的重组1型单纯疱疹病毒HSV1-rc/ΔUL2感染携带hBMP7基因的AAV载体细胞株BHK-21细胞的方法获得了滴度为2×1012vg/ml、纯度达99%的重组人骨形态发生蛋白7的腺相关病毒载体(AAV-hBMP7)。结论RT-PCR方法从HEK293细胞中扩增克隆hBMP全长cDNA是一种有效可行的方法。成功地构建了高滴度、高纯度的AAV-hBMP7载体,为进一步体内及体外研究基因治疗促进骨愈合提供了有力的工具。  相似文献   
16.
目的 探讨部分肿瘤相关分子标志物免疫组织化学的表达与结直肠癌淋巴结转移的相关性.方法 应用免疫组织化学技术检测65例结直肠癌手术标本Ki-67、p53的表达情况,对照手术所见和手术标本的病理检查结果 ,研究这些肿瘤相关分子标志物与肿瘤的生物学特性如浸润和淋巴结转移等的关系.结果 65例结直肠癌手术标本Ki-67、p53免疫组织化学的表达与肿瘤肠壁浸润深度无明显相关性(P>0.05).Ki-67的表达及Ki-67标记指数的表达与淋巴结转移及Dukes分期有明显的相关性(P<0.01);p53标记指数的表达与淋巴结转移有相关性(P<0.05),与Dukes分期有明显的相关性(P<0.01).结论 作为反应细胞增殖活性的肿瘤相关分子标志物Ki-67,其免疫组织化学的表达程度可间接反映结直肠癌淋巴结转移状况,可能成为反映淋巴结转移的一个标志物.  相似文献   
17.
Senile plaques in Alzheimer's disease (AD) are composed principally of Aβ, a 4 kDa fragment of the amyloid precursor protein (APP). Longer forms of APP which contain a Kunitz proteinase inhibitor (KPI) domain are elevated in aged and in AD brains. Tissue factor pathway inhibitor-1 (TFPI) contains three tandem KPI domains and has been well characterized for its role as a natural anticoagulant in the extrinsic coagulation pathway. Functionally, the first two KPI domains of TFPI bind and inhibit the activity of factor Xa and VIIa respectively. In addition, TFPI and APP-KPI share a common clearance mechanism through the low density lipoprotein receptor-related protein (LRP). As part of an ongoing study of the role of KPI-containing proteins in AD, the current study examines TFPI localization in the brain. We report here that TFPI is immunohistochemically localized to microglia in both AD and non-AD individuals and is localized to some senile plaques in AD. Western blot analyses indicate that the amount of TFPI is elevated in frontal cortex samples from AD brains. We propose that TFPI may play a cell specific role in proteinase regulation in the brain.  相似文献   
18.
SUMMARY: A comparative immunohistological study was performed for the glomerular deposition of complements (C1q and C3c), fibrin/fibrinogen‐related antigen (FRA), the expression of intercellular adhesion molecule‐1 (ICAM‐1), and the infiltration of leucocytes bearing β2 integrins (leucocyte function associated antigen‐1 (LFA‐1), complement receptor 3 (CR3) and complement receptor 4 (CR4)) on renal biopsy specimens from 49 cases with Henoch‐Schoenlein purpura nephritis (HSPN), and 49 age‐matched cases with immunoglobulin A nephropathy (IgAN). the glomerular expression of ICAM‐1 was signifcantly correlated with the glomerular infiltration of leucocyte function associated antigen (LFA)‐1+ leucocytes in both diseases, and with that of CR3+ leucocytes in HSPN. the expression of ICAM‐1 was closely localized with the infiltration of LFA‐1+ leucocytes in the study with double immunostaining. the incidence and intensity of glomerular deposition of FRA were significantly higher in HSPN than in IgAN (P< 0.001), and those of C3c were significantly lower in HSPN than in IgAN (P< 0.001). the glomerular deposition of FRA was significantly correlated with the glomerular infiltration of CR4+ leucocytes in HSPN (P<0.05) but not in IgAN. In contrast, the glomerular deposition of C3c was significantly correlated with the glomerular infiltration of CR4+ leucocytes in IgAN (P<0.05), but not in HSPN. Studies with double immunostaining revealed a close association of CR4+ leucocytes with FRA deposition in HSPN and with C3c deposition in IgAN, respectively. the number of glomerular leucocytes bearing β2 integrins was significantly correlated with urinary protein at the time of renal biopsy in both diseases. These results suggested the differential roles of β2 integrins in the induction of glomerular injury in HSPN and IgAN. the ICAM‐1/LFA‐1 interaction may commonly be involved in the glomerular infiltration of leucocytes in both diseases. the ICAM‐1/CR3 interaction may be involved only in HSPN. Complement receptor 4 may function as a fibrin/fibrinogen receptor in HSPN, while CR4 may function as a complement receptor in IgAN.  相似文献   
19.
目的 探讨胃癌组织中HpcagA菌株感染对IL-8蛋白表达的影响。方法 采用流式细胞技术,对27例胃癌及相应的癌旁正常组织中IL-8蛋白的表达进行定量检测,用PCR法,对27例胃癌组织中HpcagA基因进行扩增。结果 27例胃癌组织中中,有25例(92%)可明显表达IL-8蛋白;而相应的癌旁正常组织中,基本没有IL-8蛋白的表达或仅有弱相应的癌旁正常组织中,基本没有IL-8蛋白的表达或仅有弱表达,HpcagA感染的胃癌组织中,IL-8的表达水平为64.27%,高于未感染HpcagA的胃癌组织(39.86%)。结论 IL-8在胃癌组织中的高表达与HpcagA感染有关。即HpcagA菌株感染可上调IL-8在胃癌组织中的表达水平。  相似文献   
20.

Objectives

The aim of the study was to characterize the differences in the frequencies of NS3 and NS5A resistance-associated variants (RAVs) among Polish therapy-naive genotype 1 (G1) hepatitis C virus (HCV)-monoinfected and human immunodeficiency virus (HIV)/HCV-coinfected patients including clustering patterns and association of RAV frequency with liver fibrosis.

Methods

NS3/NS5A RAVs were identified by population sequencing in 387 directly acting antiviral treatment-naive G1-infected individuals (54 with genotype 1a (G1a) and 333 with genotype 1b (G1b)). Liver fibrosis was assessed based on histopathology or ultrasound elastography. Phylogenetic clusters were identified using maximum likelihood models. For statistics, chi-squared or two-sided Fisher's exact tests and multivariate logistic regression models were used, as appropriate.

Results

NS3 RAVs were found in 33.33% (18/54) for G1a and 2.62% (8/297) for G1b whereas NS5A variants were present in 5.55% (3/54) G1a and 9.31% (31/333) G1b sequences. Variations in NS5A 31 and 93 codon positions were found only in G1b (4.2% (14/333) for L31I/F/M and 5.39% (17/333) for Y93H). NS5A RAVs were more frequent among patients with advanced liver fibrosis (17.17% (17/99) for F3–F4 versus 6.94% (17/245) for F0–F2; p 0.004) or liver cirrhosis (20.34% (12/59) for F4 versus 7.72% (22/285) for F0–F3; p 0.003). Liver cirrhosis (F4) was associated with higher odds ratio of the NS5A RAVs among HCV-infected patients (odds ratio 2.34, 95% CI 1.004–5.291; p 0.049). NS5A RAVs were less frequent among sequences forming clusters and pairs (5.16% (8/155) versus 11.21% (26/232); p 0.039).

Conclusions

Presence of NS5A RAVs correlated with progression of liver fibrosis and represents de novo selection of variants rather than transmission of drug resistance. Hence, the presence of NS5A RAVs may be a predictor for a long-lasting HCV infection.  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