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   4365篇
  免费   1074篇
  国内免费   427篇
耳鼻咽喉   15篇
儿科学   31篇
妇产科学   68篇
基础医学   874篇
口腔科学   99篇
临床医学   464篇
内科学   479篇
皮肤病学   42篇
神经病学   148篇
特种医学   77篇
外国民族医学   1篇
外科学   259篇
综合类   867篇
预防医学   94篇
眼科学   100篇
药学   408篇
中国医学   72篇
肿瘤学   1768篇
  2024年   27篇
  2023年   287篇
  2022年   480篇
  2021年   770篇
  2020年   697篇
  2019年   480篇
  2018年   330篇
  2017年   345篇
  2016年   364篇
  2015年   600篇
  2014年   474篇
  2013年   300篇
  2012年   205篇
  2011年   194篇
  2010年   105篇
  2009年   60篇
  2008年   26篇
  2007年   8篇
  2006年   1篇
  2005年   4篇
  2004年   1篇
  2003年   2篇
  2001年   1篇
  1998年   1篇
  1995年   1篇
  1994年   2篇
  1992年   1篇
  1989年   3篇
  1988年   1篇
  1985年   9篇
  1984年   21篇
  1983年   15篇
  1982年   13篇
  1981年   11篇
  1980年   5篇
  1979年   3篇
  1978年   8篇
  1977年   1篇
  1976年   2篇
  1975年   6篇
  1974年   1篇
  1973年   1篇
排序方式: 共有5866条查询结果,搜索用时 78 毫秒
61.
Objective To compare the expression level of exosomal miR-503 in peritoneal dialysis effluent (PDE) from patients of different peritoneal transport characteristics, predict the target genes of miR-503 and provide bioinformatic data for researches of peritoneal transport characteristics. Methods Twenty-four stable peritoneal dialysis (PD) patients were selected and divided into high transport group (H group, n=12) and low transport group (L group, n=12) according to the results of peritoneal equilibration tests (PET). The 500 ml PDE that was left on the patient's abdomen overnight was collected and concentrated using ultrafiltration cell. Exosomes in PDE were resuspended in phosphate buffered saline (PBS) after ultracentrifugation and the characteristics of PDE exosomes were identified by transmission electron microscope (TEM), nanoparticle tracking analysis (NTA), Western blotting and fluorescent staining. MicroRNAs were extracted from PDE exosomes. The expression levels of PDE exosomal miR-503 in the two groups were detected by quantitative real-time PCR. Then the relations between the relative quantity of PDE exosomal miR-503 and PET values or 24 h ultrafiltration volume (UF) were analyzed. Targetscan and miRDB databases were used to predict the target genes of miR-503. Gene ontology (GO) functional enrichment and Kyoto encyclopedia of genes and genomes (KEGG) signaling pathway analysis were relied on DAVID (https://david.ncifcrf.gov/). Results The exosomes in PDE showed a round and cup-shaped morphology under TEM, and the diameters were approximately 100 nm measured by NTA. The specific biomarkers of exosomes, CD63, CD81 and heat shock protein -70 (HSP-70) were all detected by Western blotting. The internalization and uptake of the exosomes was observed after fluorescent staining. The relative expression level of PDE exosomal miR-503 in H group was found to be significantly higher than that in L group (P=0.002), and the relative quantity of PDE exosomal miR-503 was significantly positively correlated with PET values (r=0.547, P=0.006), but not 24 h UF (r=-0.297, P=0.159). There were 156 target genes of miR-503 in total that could be predicted by two different databases at the same time. GO analysis of these 156 target genes was mainly focused on kinase binding, regulation of protein modification and catabolic process as well as regulation of epithelial cell proliferation. KEGG enriched many tumor associated or classical signaling pathways, including transforming growth factor-β (TGF-β) signaling pathway and vascular endothelial growth factor (VEGF) signaling pathway. The prediction showed that vascular endothelial growth factor A (VEGFA) was a direct target gene of miR-503 and it was also related to many proteins involved in fibrosis mechanism. Conclusions The expression level of PDE exosomal miR-503 is significantly higher in H group, and positively correlates with PET values, which may regulate the angiogenesis of peritoneal vessels by targeting VEGFA.  相似文献   
62.
目的观察复肝丸调控miR-424表达以抑制肝窦内皮细胞血管新生的作用及其机制。方法以不同剂量(0~2 000 mg/L)的复肝丸与人肝窦内皮细胞(HHSEC)共孵育,CCK8法检测复肝丸对细胞活力的影响,分析复肝丸对细胞无毒性作用的剂量范围,并以此作为后续药效及机制评价的剂量。以CoCl_2诱导HHSEC血管新生模型,分为正常组、模型组、miR-424抑制剂组及复肝丸组,除正常组外,其余各组以CoCl_2诱导细胞血管新生,miR-424抑制剂组及复肝丸组分别以miR-424抑制剂及复肝丸(200 mg/L)与细胞共孵育24 h。采用CCK8法检测细胞活力与增殖情况;Transwell观察细胞迁移变化情况;Matrigel管腔生成实验评价细胞管腔形成情况;定量RT-PCR检测miR-424、HIF-1α、vWF、CD31基因表达;Western blot法检测HIF-1α、vWF、CD31蛋白表达。结果复肝丸剂量小于400 mg/L对HHSCE无明显细胞毒性。与正常组比较,200μmol/L CoCl_2可诱导肝窦内皮细胞缺氧损伤模型,且模型组miR-424、HIF-1α表达增加,细胞迁移和管腔生成增多,vWF、CD31表达增加(P0.01);与模型组比较,miR-424抑制剂与200 mg/L复肝丸干预后,miR-424与HIF-1α表达均不同程度降低,细胞迁移和管腔生成受抑制,vWF、CD31表达降低(P0.01);且复肝丸组综合疗效与miR-424抑制剂相当。结论复肝丸具有良好的抑制肝窦内皮细胞血管新生的作用,其作用机制与抑制miR-424表达相关。  相似文献   
63.
目的研究粉防己碱(TET)调控miR-21表达抑制卵巢癌上皮间质转化(EMT)的作用。方法以人卵巢癌细胞(A2780细胞)、人卵巢透明癌细胞(ES-2细胞)和正常人卵巢上皮细胞(IOSE80细胞)作为研究对象,采用MTT法测定0、1.0、2.0、5.0、10.0、20.0μmol/L的TET对上述3种细胞增殖的影响。实验分为IOSE80细胞对照组、A2780细胞对照组、ES-2细胞对照组、A2780细胞TET组、ES-2细胞TET组,采用实时荧光定量PCR法(RT-qPCR)测定各组细胞miR-21表达水平;迁移实验和侵袭实验考察TET对细胞迁移和侵袭的影响;蛋白印迹法(Western blot)测定各组细胞GSK3β、p-GSK3β、β-catenin、E-cadherin、N-cadherin、Vimentin蛋白表达水平。结果①与对照组相比,TET浓度在1.0~20.0μmol/L时,A2780细胞和ES-2细胞存活率随着TET浓度的增加显著降低(P0.05);为减少TET药物对细胞的毒性,采用TET对A2780细胞和ES-2细胞的处理浓度分别为5.0μmol/L和3.0μmol/L进行后续实验。②与IOSE80细胞组相比,A2780细胞对照组和ES-2细胞对照组miR-21表达水平显著升高(P0.05);与A2780细胞对照组和ES-2细胞对照组相比,A2780细胞5.0μmol/L TET组和ES-2细胞3.0μmol/L TET组miR-21表达水平、迁移能力、侵袭能力、GSK3蛋白磷酸化水平、β-catenin蛋白表达水平、N-cadherin蛋白表达水平、Vimentin蛋白表达水平明显降低(P0.05),E-cadherin蛋白表达水平明显升高(P0.05)。结论 TET可能通过下调miR-21表达水平,从而阻断Wnt/β-catenin信号通路抑制卵巢癌EMT。  相似文献   
64.
目的 探讨注意缺陷多动障碍(ADHD)儿童药物治疗前后microRNA表达量与临床症状的关系。方法 选取2017年5月至2018年10月初诊为ADHD儿童80例为研究对象,将愿意接受药物治疗的儿童随机分为盐酸哌甲酯治疗组(n=31)和盐酸托莫西汀治疗组(n=33),不愿接受治疗的作为未治疗组(n=16),随访中盐酸哌甲酯组脱落10例,盐酸托莫西汀组脱落13例。另随机选取同时期行健康体检儿童60例作为健康对照组。ADHD儿童在首诊、随访3个月、6个月时进行SNAP-V评分,并采集ADHD及健康对照组儿童血清样本以荧光定量PCR法检测miR-4655-3p和miR-7641的相对表达量。结果 重复测量方差分析结果显示,注意力不足症状SNAP-V评分在两治疗组和未治疗组中,以及两种miRNA相对表达量在两治疗组和健康对照组中均存在分组与时间因素差异,且分组与时间因素均存在交互作用(P < 0.05)。多动冲动症状SNAP-V评分在两治疗组和未治疗组中存在时间因素差异(P < 0.05),而分组因素差异无统计学意义,且时间因素与分组因素无交互作用(P > 0.05)。经药物治疗的ADHD儿童注意力不足症状SNAP-V评分与miRNA-4655-3p和miRNA-7641相对表达量均呈负相关(分别r=-0.314、-0.495,P < 0.05)。结论 药物治疗可显著改善ADHD儿童的临床症状;血清中miR-4655-3p和miR-7641的表达水平可能作为ADHD的诊断及疗效评估的分子指标。  相似文献   
65.
目的 探讨长链非编码RNA(lncRNA)MLK7-AS1在人脑胶质瘤组织中表达及其对胶质瘤U251细胞增殖、侵袭的影响。方法 选择2016~2017年手术切除的脑胶质瘤组织标本45例,2007版WHO分级Ⅰ级8例,Ⅱ级15例,Ⅲ级10例,Ⅳ级12例。另选择其中10例瘤旁正常脑组织作对照。体外培养U251细胞和人正常星形胶质细胞(NHA)。U251细胞根据转染质粒分成四组:转染miR-375 mimic组、转染si-MLK7-AS1组、同时转染miR-375 inhibitor和si-MLK7-AS1组以及只转染miR-375 inhibitor组。RT-qPCR检测MLK7-AS1和miR-375的表达水平;荧光素酶报告基因实验验证MLK7-AS1与miR-375之间的关系;CCK-8法检测U251细胞增殖活性,Transwell实验检测U251细胞侵袭能力。结果 高级别胶质瘤组织MLK7-AS1表达水平明显高于低级别胶质瘤组织(P<0.05),而后者明显高于瘤旁正常脑组织(P<0.05);高级别胶质瘤组织miR-375表达水平明显低于低级别胶质瘤组织(P<0.05),而后者明显低于瘤旁正常脑组织(P<0.05)。U251细胞MLK7-AS1表达水平明显高于NHA(P<0.05),miR-375表达水平明显低于NHA(P<0.05)。序列分析显示MLK7-AS1和miR-375 存在特异性结合序列,荧光素酶报告基因实验表明U251细胞MLK7-AS1负调控miR-375表达。沉默MLK7-AS1表达通过上调miR-375表达明显抑制U251细胞增殖和侵袭(P<0.05)。结论 lncRN AMLK7-AS1可能通过调节miR-375的表达水平在人脑胶质瘤中发挥着促癌的作用  相似文献   
66.
目的 探讨miR-153对胶质母细胞瘤细胞增殖的影响。方法 体外培养胶质母细胞瘤细胞系U87、U251、SHG-44和T98G细胞,分别转染miR-153质粒(miR-153组)、空载质粒(载体组)和miR-153突变质粒(miR-153突变组),另设置空白对照组(不转染任何质粒)。RT-PCR检测miR-153、FOXR2、CDK8和CDK13的表达,MTT法检测细胞增殖能力。结果 miR-153组U87、U251、SHG-44和T98G细胞miR-153表达水平较载体组和空白对照组显著上升(P<0.05),细胞增殖水平较载体组和空白对照组均显著降低(P<0.05)。miR-153组U87、U251、SHG-44和T98G细胞FXOR2、CDK8和CDK13的mRNA水平较miR-153突变组、载体组和空白对照组均显著下降(P<0.05),而后三组之间均无统计学差异(P>0.05)。结论 miR-153抑制胶质母细胞瘤细胞增殖,其机制可能与抑制FXOR2、CDK8和CDK13表达有关。  相似文献   
67.
Effective therapeutic targets for triple-negative breast cancer (TNBC), a special type of breast cancer (BC) with rapid metastasis and poor prognosis, are lacking, especially for patients with chemotherapy resistance. Decitabine (DCA) is a Food and Drug Administration-approved DNA methyltransferase inhibitor that has been proven effective for the treatment of tumors. However, its antitumor effect in cancer cells is limited by multidrug resistance. Cancer stem cells (CSCs), which are thought to act as seeds during tumor formation, regulate tumorigenesis, metastasis, and drug resistance through complex signaling. Our previous study found that miR-155 is upregulated in BC, but whether and how miR-155 regulates DCA resistance is unclear. In this study, we demonstrated that miR-155 was upregulated in CD24CD44+ BC stem cells (BCSCs). In addition, the overexpression of miR-155 increased the number of CD24CD44+ CSCs, DCA resistance and tumor clone formation in MDA-231 and BT-549 BC cells, and knockdown of miR-155 inhibited DCA resistance and stemness in BCSCs in vitro. Moreover, miR-155 induced stemness and DCA resistance by inhibiting the direct target gene tetraspanin-5 (TSPAN5). We further confirmed that overexpression of TSPAN5 abrogated the effect of miR-155 in promoting stemness and DCA resistance in BC cells. Our data show that miR-155 increases stemness and DCA resistance in BC cells by targeting TSPAN5. These data provide a therapeutic strategy and mechanistic basis for future possible clinical applications targeting the miR-155/TSPAN5 signaling axis in the treatment of TNBC.  相似文献   
68.
目的 研究长链非编码RNA (LncRNA) UCA1对肺癌细胞增殖、凋亡及放射敏感性影响及其机制。方法 运用qRT-PCR法检测肺癌细胞A549、H1299和人正常肺细胞HBE中UCA1、miR-513a-5p表达。将si-con组(转染si-con)、si-UCA1组(转染si-UCA1)、miR-513a-5p组(转染miR-513a-5p mimics)、miR-NC组(转染miR-NC)、IR+si-con组(转染si-con+照射)、IR+si-UCA1组(转染miR-NC+照射)、IR+miR-513a-5p组(转染miR-513a-5p mimics+照射)、IR+miR-NC组(转染miR-NC+照射)、IR+si-UCA1+anti-miR-513a-5p组(共转染si-UCA1和anti-miR-513a-5p+照射)均用脂质体法转染至A549、H1299细胞,然后部分组进行4Gy照射。MTT法检测各组细胞增殖,克隆形成实验检测细胞增敏比,流式细胞术检测各组细胞凋亡,双荧光素没报告基因检测实验检测各组细胞的荧光活性。结果 与HBE细胞相比,A549、H1299细胞中UCA1表达显著升高(P<0.05),miR-513a-5p表达显著降低(P<0.05)。抑制UCA1、过表达miR-513a-5p均可明显抑制A549、H1299细胞增殖、促进凋亡、提高放射敏感性(放射增敏比为1.897、2.146和1.615、1.872)。miR-513a-5p可抑制野生型UCA1细胞的荧光活性,且UCA1可负向调控miR-513a-5p的表达。抑制miR-513a-5p可逆转抑制UCA1对细胞的放射敏感性的增强作用。结论 抑制LncRNA UCA1可增强放射对肺癌细胞敏感性,其机制可能与靶向抑制miR-513a-5p有关。  相似文献   
69.
Acute pancreatitis (AP) is an inflammatory disease with high morbidity and mortality. Dysregulation of microRNAs (miRNAs) was involved in human diseases, including AP. However, the effects of miR-92b-3p on AP process and its mechanism remain not been fully clarified. The expression levels of miR-92b-3p and tumor necrosis factor receptor-associated factor-3 (TRAF3) were measured by quantitative real-time polymerase chain reaction (qRT-PCR). The protein levels of TRAF3, tumor necrosis factor α (TNF-α) TNF-α, interleukin-6 (IL-6), phosphorylated mitogen-activated protein kinase kinase 3 (p-MKK3), MKK3, p38 and phosphorylated p38 (p-p38) were detected by western blot. The concentration of TNF-α and IL-6 in the medium was measured using ELISA kits. The possible binding sites of miR-92b-3p and TRAF3 were predicted by TargetScan and verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. The expression level of miR-92b-3p was decreased and TRAF3 expression was increased in AR42J cells stimulated with caerulein. Moreover, the protein levels of pro-inflammatory cytokines (TNF-α and IL-6) were markedly elevated, and the expression levels of autophagy-related markers Beclin1 as well as the ratio of LC3-II/I were obviously increased in AR42J cells treated with caerulein. In addition, overexpression of miR-92b-3p or knockdown of TRAF3 significantly suppressed the release of pro-inflammatory cytokines and autophagy in caerulein-induced AR42J cells. Furthermore, TRAF3 was a direct target of miR-92b-3p and its upregulation reversed the effects of miR-92b-3p overexpression on inflammatory response and autophagy. Besides, overexpression of miR-92b-3p inhibited the activation of the MKK3-p38 pathway by affecting TRAF3 expression. In conclusion, miR-92b-3p attenuated inflammatory response and autophagy by downregulating TRAF3 and suppressing MKK3-p38 pathway in caerulein-induced AR42J cells, providing a novel avenue for treatment of AP.  相似文献   
70.
目的 探讨miR-96与miR-103在肝癌组织中的表达及其与预后的关系。方法 选取122例肝细胞癌患者作为本研究对象。聚合酶链式反应检测miR-96和miR-103表达水平,采用单因素和多因素Cox回归模型,探讨肝癌患者中位生存时间的危险因素并建立预测模型。结果 肝癌组织中miR-96和miR-103相对表达水平均显著高于癌旁正常组织;肝癌组织中miR-96和miR-103的表达与肿瘤直径、淋巴结转移、临床分期及分化程度均有关(均P<0.05),而与性别、年龄及合并肝硬化等无关(P>0.05);所有患者随访60月,中位生存时间为37.8月。单因素分析结果显示:肝细胞癌患者中位生存时间与肿瘤直径、淋巴结转移、TNM分期、病理分化程度、miR-96和miR-103表达水平差异均有统计学意义(均P<0.05)。多因素分析结果显示:TNM分期为Ⅲ~Ⅳ、低分化、淋巴结转移、miR-96和miR-103高表达是肝癌患者中位生存时间独立危险因素。结论 肝癌组织中miR-96和miR-103的高表达是患者预后差的独立影响因素,可作为原发性肝癌患者预后评估指标。  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