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   47742篇
  免费   4124篇
  国内免费   1649篇
耳鼻咽喉   557篇
儿科学   1484篇
妇产科学   649篇
基础医学   3244篇
口腔科学   910篇
临床医学   4907篇
内科学   7193篇
皮肤病学   665篇
神经病学   1647篇
特种医学   1723篇
外科学   5736篇
综合类   8451篇
现状与发展   4篇
一般理论   3篇
预防医学   4725篇
眼科学   1130篇
药学   4770篇
  33篇
中国医学   2973篇
肿瘤学   2711篇
  2024年   165篇
  2023年   515篇
  2022年   1299篇
  2021年   1855篇
  2020年   1349篇
  2019年   1116篇
  2018年   1215篇
  2017年   1281篇
  2016年   1106篇
  2015年   1613篇
  2014年   2208篇
  2013年   2769篇
  2012年   4064篇
  2011年   4125篇
  2010年   3343篇
  2009年   2814篇
  2008年   3156篇
  2007年   3110篇
  2006年   2798篇
  2005年   2345篇
  2004年   1818篇
  2003年   1448篇
  2002年   1241篇
  2001年   1080篇
  2000年   969篇
  1999年   578篇
  1998年   196篇
  1997年   169篇
  1996年   138篇
  1995年   137篇
  1994年   131篇
  1993年   111篇
  1992年   303篇
  1991年   260篇
  1990年   231篇
  1989年   213篇
  1988年   177篇
  1987年   186篇
  1986年   162篇
  1985年   173篇
  1984年   149篇
  1983年   145篇
  1982年   69篇
  1981年   76篇
  1979年   117篇
  1978年   86篇
  1974年   76篇
  1973年   110篇
  1972年   100篇
  1971年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
211.
212.
目的探讨x-相关凋亡抑制蛋白(XIAP)和促凋亡因子Smac在胰腺癌细胞化疗抵抗中的作用,以及转染胞浆表达型Smac基因靶向下凋XIAP对化疗药物诱导的胰腺癌细胞凋亡的影响。方法应用流式细胞术检测顺铂、5-FU介导的Panc-1、BXPC-3的凋亡率及胞浆染色分析细胞XIAP表达变化,Western blot分析XIAP、Smac、Caspase-3表达水平;构建pEGFP-NI/Smac真核表达载体并转染胰腺癌Panc-1细胞,流式细胞术检测转染Smac基因前后Panc-1细胞的凋亡敏感性。结果与BXPC-3细胞相比,Panc-1对顺铂或5-FU介导的凋亡具有较强抵抗性,Western blot分析显示Panc-1细胞高表达XIAP,在化疗药物作用下化疗敏感细胞BXPC-3胞浆内XIAP水平下降明显多于Panc-1细胞,而且凋亡的BXPC-3细胞释放入胞浆内的成熟Smac蛋白水平明显高于Panc-1细胞。转染胞浆表达型Smac基因至化疗抵抗Panc-1细胞,可明显下调其XIAP表达水平,促进效应Caspase-3分子活化,显著提高顺铂、5-FU诱导的细胞凋亡率。结论胰腺癌细胞XIAP的表达水平下调与其化疗敏感性有关,XIAP是克服化疗抵抗的重要靶分子,而上调Smac活性蛋白的胞浆表达作为一种有效调节信号,通过拮抗XIAP的凋亡抑制作用协同化疗药物促进胰腺癌细胞凋亡。  相似文献   
213.
214.
An open comparative trial was conducted in 58 adult obese patients (Body Mass Index > or = 25 kg/square metre). Group I (n = 27), non-drug, was advised diet (1200-1600 cals) and a brisk walk for 30 minutes. Group II, in addition, received Guggulu (Medohar) 1.5-3 gms/day for 30 days. Mean difference in weight loss between Guggulu and non-drug group was 0.32 kg (ns) on day 15 and 0.58 kg on day 30 (ns). The mean weight reduction in patients (> 90 kgs) was 1.92 kg (ns) and 2.25 kg (ns) higher in Guggulu group. All patients weighing > 90 kg lost weight in Guggulu group whilst 3 in non-drug group did not lose weight. Guggulu was tolerated well. The data from this pilot study suggest a synergistic diet-Guggulu interaction over 30 days in patients weighing > 90 kgs which needs to be confirmed in a large placebo controlled study.  相似文献   
215.
老年抑郁症和焦虑障碍共病患者的临床特征   总被引:18,自引:0,他引:18  
目的探讨老年抑郁症和焦虑障碍共病患者的临床特征。方法根据美国精神障碍诊断手册第四版(DSM-IV)的诊断标准,把78例老年抑郁症患者分为两组,单纯抑郁症组(抑郁症组,N=44)及抑郁症和焦虑障碍共病组(共病组N=34)。对所有对象评定一般人口学资料及老年抑郁量表(GDS)、汉密顿抑郁量表(HAMD)、汉密顿焦虑量表(HAMA)、简易智能状态评定量表(MMSE)和健康状况调查问卷(SF-36)等,比较两组患者间差异。结果抑郁症组与共病组患者的性别、年龄、病程、居住情况、家族史、民族、发病诱因和受教育年限等方面的差异无统计学意义(均P>0.05)。GDS总分(14.0±1.2/12.1±2.0,t=4.92)、HAMD(38.1±4.0/33.4±4.7,t=4.35)和HAMA总分(22.6±5.5/11.7±2.7,t=10.93)及其因子分、HAMD第3项(自杀)条目分、SF-36躯体功能(79.2±13.6/69.1±13.6,t=3.25)、社交功能(70.0±21.2/50.0±22.5,t=4.02)评分共病组均高于抑郁症组差异有统计学意义(均P<0.05)。结论老年抑郁症和焦虑障碍共病患者较单纯抑郁患者的抑郁和焦虑症状更重、自杀风险大、生活质量更差。  相似文献   
216.
BACKGROUND: Evidence for the effectiveness of topical treatments, in providing symptomatic relief from ocular allergy, remains uncertain. AIMS: To assess the effectiveness and relative efficacy of topical treatments for the management of seasonal allergic conjunctivitis. DESIGN OF STUDY: A systematic review and meta-analysis. SETTING: A literature search of the Cochrane Library, Medline, and EMBASE bibliographic databases. METHOD: Double-masked randomised controlled trials were identified, that compared the use of topical mast cell stabilisers (sodium cromoglycate, nedocromil, lodoxamide) with placebo, topical antihistamines with placebo, and topical mast cell stabilisers with topical antihistamines. RESULTS: A meta-analysis of six trials showed that patients using sodium cromoglycate were 17 times (95% confidence interval [CI] = 4 to 78) more likely to perceive benefit compared with those using a placebo, although this estimate may be partially influenced by publication bias. Five trials indicated that those patients using nedocromil were 1.8 times (95% CI = 1.3 to 2.6) more likely to perceive their allergy to be moderately or totally controlled than those using a placebo. Four trials showed that those using antihistamines were 1.3 times (95% CI = 0.8 to 2.2) more likely to perceive a 'good' treatment effect than those using mast cell stabilisers, although this beneficial effect was not statistically significant. Limited evidence suggests that antihistamines might have a faster therapeutic effect compared to mast cell stabilisers. CONCLUSION: Overall, these findings confirm the benefit of topical mast cell stabilisers and antihistamines over placebo for the treatment of allergic conjunctivitis. There is, however, insufficient evidence to recommend the use of one type of medication over another. Treatment preferences should therefore be based on convenience of use (with reduced frequency of instillation for some preparations), patient preference, and costs, especially as important side effects were not reported with any medication.  相似文献   
217.
218.
Objective To investigate the proliferation potential of colon cancer cells co-cultured with different proportions regenerating hepatocytes and role of the cell growth factors related to liver regeneration in vitro.Methods Active regenerating hepatocytes were obtained by collagenase perfusion in situ of rats models underwent 70% liver resection after 24 hours.Co-cultures with different proportions of hepatocytes to human colon cell line SW480 were performed respectively.The proportion of hepatocytes to human colon cell line SW480 Was 10:1 in group A,1:1 in group B.There was only human colon cell line SW480 in group C(control group).Proliferation capacity was assessed with the percentage by 3H-thy incorporation.Concentration of epidermal growth factor(EGF),insulin-like growth factor-1(IGF-1)and hepatocyte growth factor(HGF)was analyzed by ELISA.Results There was no significant difference among the 3 groups in 3H-thy incorporation percentage,and concentration of EGF,IGF-land HGF after 24 hours' culture(P>0.05).3H-thy incorporation percentage(15.9±1.4,13.2±1.5),and concerntration of EGF [(722.9±55.4)ng/L,(498.2+41.5)ng/L]and IGF-1[(755.2±35.7)ng/L,(538.1±37.5)ng/L]in Group A and B were higher than that in group C after 72 hours(P<0.05).Especially the indexes above in group A were higher than that in group B(P<0.05).there was no significant difference in concerntration of HGF among the 3 groups after 72 hours(P>O.05).Conclusions These results imply that the regenerating hepatocytes contribute to the hyperproliferative state of co-culturing colon cancer cells.The mechanism maybe have relationship with EGF and IGF-1 high expression in colon cancer cells caused by growth signals coming from hepatocytes.  相似文献   
219.
220.
目的探讨皖籍汉族人群MICA基因(major histocompatibility complex class Ⅰchain-related gene A,MICA)第2、3、4外显子的多态性,及其与HLA-B抗原的连锁不平衡在强直性脊柱炎(ankylosing spondylitis,AS)发病中的作用。方法采用聚合酶链反应-序列特异性寡核苷酸探针杂交(polymerase chain reactionsequence-specific oligonucleotide probing,PCR-SS0)技术对56例AS患者和112名正常对照人群进行MICA基因第2、3、4外显子的多态性和HLA-B抗原的检测。结果AS患者和正常对照人群的MICA等位基因分布均以MICA*008占优势,频率分别为32.14%和30.36%。两组人群MICA*007等位基因的分布差异有统计学意义(X^2=10.18,P〈0.05,RR=2.50)。单倍型分析显示,AS患者和正常对照人群的MICA等位基因均显示出与多个HLA-B位点的连锁不平衡现象,两组间差异有统计学意义的单倍型为MICA*007-B27(X^2=18.46,P〈0.05,RR=7.47)。分层分析结果显示,HLA-B27阳性与AS的相关性有统计学意义(P〈0.05),但MICA*007基因与AS的相关性无统计学意义(P〉0.05)。结论AS患者中MICA*007等位基因频率的显著升高可能源于MICA基因与HLA-B位点间的广泛连锁不平衡。  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