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   22924篇
  免费   2285篇
  国内免费   1935篇
耳鼻咽喉   174篇
儿科学   190篇
妇产科学   290篇
基础医学   2915篇
口腔科学   261篇
临床医学   3233篇
内科学   3267篇
皮肤病学   202篇
神经病学   1352篇
特种医学   901篇
外国民族医学   13篇
外科学   2170篇
综合类   3863篇
现状与发展   6篇
一般理论   1篇
预防医学   1528篇
眼科学   673篇
药学   2641篇
  35篇
中国医学   1600篇
肿瘤学   1829篇
  2024年   89篇
  2023年   437篇
  2022年   1055篇
  2021年   1337篇
  2020年   1044篇
  2019年   795篇
  2018年   823篇
  2017年   814篇
  2016年   752篇
  2015年   1121篇
  2014年   1393篇
  2013年   1164篇
  2012年   1626篇
  2011年   1952篇
  2010年   1203篇
  2009年   1011篇
  2008年   1193篇
  2007年   1174篇
  2006年   1185篇
  2005年   1178篇
  2004年   756篇
  2003年   729篇
  2002年   587篇
  2001年   498篇
  2000年   533篇
  1999年   542篇
  1998年   318篇
  1997年   334篇
  1996年   251篇
  1995年   247篇
  1994年   208篇
  1993年   131篇
  1992年   135篇
  1991年   95篇
  1990年   98篇
  1989年   79篇
  1988年   72篇
  1987年   70篇
  1986年   53篇
  1985年   25篇
  1984年   9篇
  1983年   8篇
  1982年   7篇
  1981年   5篇
  1980年   2篇
  1979年   6篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
ObjectivesTo investigate the effect and mechanism of macrophage activation and graft damage caused by nucleoside triphosphate diphosphohydrolase 1 (NTPDase1) in acute antibody-mediated rejection (AMR).MethodsAcute AMR was induced in different skin-grafted nude mouse models with wild-type NTPDase1 expression, transgene-enhanced NTPDase1 expression, or NTPDase1 gene knockout. Several methods (eg, real-time fluorescence quantitative polymerase chain reaction, high-performance liquid chromatography [HPLC], immunofluorescence, flow cytometry, and luciferin/luciferase assays) were used to study (at the histologic and molecular levels) the extracellular adenosine diphosphate (ADP) concentration, macrophage proliferation, major histocompatibility complex (MHC) class II antigen expression on the surface of macrophages, B-cell activating factor (BAFF) expression in the peripheral blood serum, and the total number of SmIg-positive B cells during acute AMR. The relative activity of NTPDase1 in B cells and epithelial cells, pathologic changes, and the incidence of positive C4d deposition around the capillaries of skin grafts on the different nude mice were studied.ResultsMacrophages proliferated significantly when acute AMR occurred. The higher the NTPDase1 expression level, the lower the extracellular ADP concentration, the expression of MHC class II antigens on the surface of macrophages, the expression of BAFF in the peripheral blood serum, and the total number of SmIg-positive B cells, indicating negative correlations. The relative activity of NTPDase1 in B cells and epithelial cells of the skin graft was different among the different mice. The higher the NTPDase1 expression level, the lower the degree of pathologic damage to the skin graft.ConclusionsImbalance in extracellular ADP degradation by NTPDase1 may promote macrophage activation, and activated macrophages may be an important cause of graft damage.  相似文献   
82.
PurposeTo investigate the clinical characteristics, chemosensitivity, and outcome of metastatic upper tract urothelial carcinoma (UTUC).Patients and MethodsRecords of patients with metastatic UTUC since January 2005 were retrieved from a database that included clinical and survival data. Statistical analyses including survival and multivariate analyses of factors were respectively performed by the Kaplan-Meier method and Cox proportional hazard model.ResultsA total of 250 consecutive UTUC cases were evaluated. There were 56 patients (22.4%) with initially diagnosed stage IV disease. The most common metastatic sites were lung (39.6%), distant lymph nodes (39.2%), bone (19.6%), liver (18.0%), and adrenal gland (7.2%), respectively, and the local recurrence rate was 10.4%. Two hundred thirteen patients received first-line chemotherapy. The overall response rate was only 28.7% and the median progression-free survival time was only 5.0 months. The overall survival time of the cohort was 18.0 months. Multivariate analyses showed that initially diagnosed stage IV disease, number of metastatic organs ≥3, no response to chemotherapy and cycles of chemotherapy ≤2 were adverse prognosticators for overall survival.ConclusionUTUC presented to be more prone to metastasize than locally recur and thought to have low chemosensitivity. Stage IV disease at initial diagnosis, number of metastatic organs, response and cycles of chemotherapy were independent prognosticators for metastatic UTUC.  相似文献   
83.
84.
Abstract

Whether polyphenols could ameliorate inflammatory bowel disease (IBD) is still conflicting. To explore the efficacy of polyphenols as an adjuvant therapy for IBD, we conducted this systematic review and meta-analysis. Literature search was performed using PubMed, Web of Science, Scopus and Cochrane databases. Finally, 12 randomized controlled trials (RCTs) were included. In contrast to control group, curcumin treatment significantly improved clinical remission in intention-to-treat (ITT) (OR = 3.36, 95% CI: 1.09–10.37) and per-protocol (PP) analysis (OR = 5.13, 95% CI: 1.84–14.27). Meanwhile, curcumin could significantly ameliorate endoscopic remission (OR = 5.69, 95% CI: 1.28–25.27) and clinical response (OR = 4.69, 95% CI: 1.03–21.47) in PP analysis. Heterogeneity was present across the studies. In conclusions, polyphenols might be an effective adjuvant treatment for ameliorating IBD. Considering the relatively few studies included in our present study, further clinical trials are required to verify the effects of polyphenols on IBD.  相似文献   
85.
目的 在“营养校园”试点学校进行为期一年的营养干预,分析评价干预效果。方法 在石家庄新华区选取一所小学和一所初中进行干预,从三、五、七年级中分别随机抽取2个班级的学生在干预前后进行调查。干预方法包括开展营养健康教育、促进身体活动、科学营养供餐支持等综合措施,通过问卷和体格测量调查学生干预前后的营养知识、饮食行为及超重肥胖变化情况。结果 干预后,营养知识题目的正确率显著提高(χ2=613.737,P<0.001),总体正确率为59.8%。学生早餐食物种类(χ2=19.841,P<0.001)和早餐摄入频率(χ2=5.405,P<0.05)均有显著改善。总体超重肥胖率未见显著改善,按性别、年级分层分析发现,女生超重肥胖率降低(χ2=1.891,P<0.05),5年级(χ2=4.923,P<0.05)和7年级(χ2=10.563,P<0.01)学生超重肥胖率降低,且高年级学生降幅更明显。结论 以校园为基础开展综合营养干预措施,可以提高学生的营养知识水平,并改善学生的不良饮食行为及超重肥胖现状。  相似文献   
86.
87.
王德光主任医师对许多较难治愈的体温升高的发热,用秦艽鳖甲散加减治疗,在临床上收到了良好的效果,文中列举两则病例以资说明。据王老经验,此方对发热者体温升高,日久不降;或发热者曾用抗菌素、激素、清热解毒类中药而无效;或者外感热病,呈现壮热骨蒸均可获效。  相似文献   
88.
Zhang Z  Jia Z  Zhu Z  Cui Y  Cheng J  Wang Q 《Planta medica》1990,56(3):293-294
Two new taxane diterpenes, decinnamoyltaxagifine ( 3) and decinnanioyltaxagifine acetate ( 2), have been isolated from the leaves and stems of TAXUS CHINENSIS. Their structures were elucidated by spectroscopic methods. Their (13)C-NMR chemical shifts were assigned.  相似文献   
89.
诊断超声对人胚胎安全性的研究   总被引:3,自引:0,他引:3  
目的 探讨诊断级B超对人胚胎发育的安全性。方法 取 12 0名孕 6~ 8周拟行人工流产孕妇 ,随机分成正常对照组 (Ⅰ组 )、辐照 5min(Ⅱ组 )、10min(Ⅲ组 )、2 0min(Ⅳ组 )、30min(Ⅴ组 )于 1h内取绒毛 ,超声辐照 30min(Ⅵ组 )于 7~ 10d后取绒毛。检测绒毛的生物化学变化。结果 诊断剂量超声辐照 2 0min可致人体宫内绒毛发生生物化学变化。丙二醛 (MDA)值随超声剂量增加而升高 (PⅠ -Ⅲ >0 .0 5,PⅠ .Ⅳ <0 .0 1,PⅠ -Ⅴ <0 .0 1) ,而超氧化物歧化酶及谷胱甘肽过氧化物酶活性随超声辐照剂量增加而下降 (PⅠ -Ⅲ >0 .0 5,PⅠ -Ⅳ <0 .0 1,PⅠ -Ⅴ <0 .0 1)。对照组与Ⅵ组比较P >0 .0 5,提示损伤作用是可逆性的。结论 诊断超声辐照时间 2 0min以上时对绒毛可造成潜在危害  相似文献   
90.
目的:比较双甘注射液与甘露醇注射液的临床疗效和不良反应。方法:用甘露醇、甘油、1,6-二磷酸果糖制成注射液双甘注射液。通过动物实验及临床应用比较其疗效和不良反应。结果:双甘注射液的脱水、利尿作用优于甘露醇注射液,对肾脏的损害小于甘露醇注射液;同样条件下输注(5ml/min),复方甘油注射液发生溶血,本品无溶血现象发生。结论:双甘注射液脱水作用强,副作用小,是比较理想的脱水药。  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