全文获取类型
收费全文 | 35708篇 |
免费 | 1811篇 |
国内免费 | 615篇 |
专业分类
耳鼻咽喉 | 365篇 |
儿科学 | 446篇 |
妇产科学 | 383篇 |
基础医学 | 5290篇 |
口腔科学 | 529篇 |
临床医学 | 3574篇 |
内科学 | 5627篇 |
皮肤病学 | 827篇 |
神经病学 | 2480篇 |
特种医学 | 1698篇 |
外国民族医学 | 5篇 |
外科学 | 3998篇 |
综合类 | 2611篇 |
现状与发展 | 7篇 |
一般理论 | 9篇 |
预防医学 | 1887篇 |
眼科学 | 885篇 |
药学 | 3509篇 |
28篇 | |
中国医学 | 1103篇 |
肿瘤学 | 2873篇 |
出版年
2025年 | 22篇 |
2024年 | 439篇 |
2023年 | 526篇 |
2022年 | 1143篇 |
2021年 | 1586篇 |
2020年 | 942篇 |
2019年 | 1061篇 |
2018年 | 1088篇 |
2017年 | 867篇 |
2016年 | 1120篇 |
2015年 | 1542篇 |
2014年 | 1850篇 |
2013年 | 2025篇 |
2012年 | 2857篇 |
2011年 | 2951篇 |
2010年 | 1741篇 |
2009年 | 1453篇 |
2008年 | 2008篇 |
2007年 | 1895篇 |
2006年 | 1709篇 |
2005年 | 1599篇 |
2004年 | 1282篇 |
2003年 | 1077篇 |
2002年 | 887篇 |
2001年 | 709篇 |
2000年 | 738篇 |
1999年 | 585篇 |
1998年 | 286篇 |
1997年 | 240篇 |
1996年 | 188篇 |
1995年 | 191篇 |
1994年 | 153篇 |
1993年 | 110篇 |
1992年 | 166篇 |
1991年 | 174篇 |
1990年 | 144篇 |
1989年 | 119篇 |
1988年 | 98篇 |
1987年 | 86篇 |
1986年 | 81篇 |
1985年 | 50篇 |
1984年 | 39篇 |
1983年 | 44篇 |
1982年 | 33篇 |
1981年 | 26篇 |
1980年 | 27篇 |
1979年 | 31篇 |
1978年 | 22篇 |
1977年 | 20篇 |
1974年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
目的 探讨全身照射(TBI)对肠道黏膜通透性和肠三叶因子(ITF)mRNA表达的影响以及二者之间的关系.方法 32只BALB/c小鼠随机均分为4组:空白对照组和总剂量8.0 Gy全身照射后4、8和12 d组.TBI剂量8.0 Gy,剂量率1.0 Gy/min.高效液相色谱-蒸发光散射检测器分析(HPLC-ELSD)检测尿液标本中乳果糖与甘露醇的排出率比值(L/M),评价各组小鼠的肠道通透性;收集空肠组织标本,实时荧光定量PCR检测肠道ITF mRNA表达水平.结果 TBI后4、8和12d组L/M比值分别为0.5092±0.0353,0.7174±0.0116和0.7295±0.0063,均明显高于空白对照组(0.2908±0.0533,F=321.47,P<0.05).TBI后4、8和12 d组ITF mRNA表达水平分别为0.78612±0.1428,0.2521±0.1223,和0.2306±0.0221,均显著低于空白对照组(1.3498±0.0476,F=235.71,P<0.05).各TBI组中L/M与肠道ITF mRNA水平呈显著负相关(r=-0.985,P<0.01).结论 TBI后随着时间延长ITF mRNA表达逐渐下降而肠黏膜通透性逐渐增加,即TBI后ITF mRNA表达与肠道通透性呈显著负相关.ITF在TBI所致肠道黏膜通透性增加中起着保护作用.Abstract: Objective To investigate the change of the intestinal permeability,the expression level of intestinal trefoil factor (ITF) mRNA and the relationship between them after total body irradiation (TBI),and explore the effect of TBI on the development of intestinal permeability and the expression level of ITF mRNA.Methods Twenty two BALB/c mice were randomly divided into 4 equal groups: 3 groups at 4,8 and 12 d after TBI with the total dose of 8.0 Gy and the dose rate of 1.0 Gy/min respectively,and a control group.Lactulose (L) and mannitol (M) were perfused into the esophagus before the experiment and urine samples were collected.Liquid chromatography was used to measure the L/M excretion ratio in the urine samples collected 4,8,and 12 days after the TBI.And then the mice were killed with their intestine were taken out.The expression of ITF mRNA in the jejunum tissue was detected by real-time fluorescence quantitative PCR.Results The urine L/M ratio levels of the groups 4,8 and 12 days after TBI were (0.5092 ± 0.0352),(0.7174 ± 0.0116),and (0.7295 ± 0.0533) respectively,all significantly higher than that of the control group [(0.2908 ± 0.0533),F = 321.47,P < 0.05].The ITF mRNA expression levels of groups 4,8 and 12 days after TBI were (0.78612 ±0.1428),(0.2521 ±0.1223),and (0.2306 + 0.0221 ) respectively,all significantly lower than that of the control group [( 1.3498 + 0.0476),F = 235.71 ,P < 0.05].The urine L/M ratio was significantly negatively correlated with the expression of ITF mRNA in all TBI groups (r = - 0.985,P < 0.01 ).Conclusions The intestinal permeability increases and the expression level of ITF mRNA decreases after TBI.The urine L/M ratio is negatively correlated with the expression level of ITF mRNA after TBI.ITF is involved in protection against intestinal permeability induced by TBI. 相似文献
993.
Gilmore JH Lin W Corouge I Vetsa YS Smith JK Kang C Gu H Hamer RM Lieberman JA Gerig G 《AJNR. American journal of neuroradiology》2007,28(9):1789-1795
BACKGROUND AND PURPOSE: The early postnatal period is perhaps the most dynamic phase of white matter development. We hypothesized that the early postnatal development of the corpus callosum and corticospinal tracts could be studied in unsedated healthy neonates by using novel approaches to diffusion tensor imaging (DTI) and quantitative tractography. MATERIALS AND METHODS: Isotropic 2 x 2 x 2 mm(3) DTI and structural images were acquired from 47 healthy neonates. DTI and structural images were coregistered and fractional anisotropy (FA), mean diffusivity (MD), and normalized T1-weighted (T1W) and T2-weighted (T2W) signal intensities were determined in central midline and peripheral cortical regions of the white matter tracts of the genu and splenium of the corpus callosum and the central midbrain and peripheral cortical regions of the corticospinal tracts by using quantitative tractography. RESULTS: We observed that central regions exhibited lower MD, higher FA values, higher T1W intensity, and lower T2W intensity than peripheral cortical regions. As expected, MD decreased, FA increased, and T2W signal intensity decreased with increasing age in the genu and corticospinal tract, whereas there was no significant change in T1W signal intensity. The central midline region of the splenium fiber tract has a unique pattern, with no change in MD, FA, or T2W signal intensity with age, suggesting different growth trajectory compared with the other tracts. FA seems to be more dependent on tract organization, whereas MD seems to be more sensitive to myelination. CONCLUSIONS: Our novel approach may detect small regional differences and age-related changes in the corpus callosum and corticospinal white matter tracts in unsedated healthy neonates and may be used for future studies of pediatric brain disorders that affect developing white matter. 相似文献
994.
995.
目的:研究CD133+细胞的干性鉴定和131I-CD133抗体在体内外对人肝癌CD133-HepG2干细胞的抑制作用。方法:氯胺T法制备并鉴定131I-CD133抗体;免疫磁珠(magnetic-activatedcellsorting,MACS)分选CD133-HepG2细胞;流式细胞仪(flowcytometry,FCM)检测分选前后CD133表达率;体外克隆形成实验、成球实验和体内成瘤实验验证其干细胞特性;将分选出的CD133细胞分组为CD133抗体、131I、131I-CD133抗体和131ICD133抗体4个组,MTT法检测不同处理后不同组中CD133细胞生长抑制率;成功构建人肝癌CD133-HepG2移植瘤模型;随机分4组,1次/2d给予尾静脉用药,共14次。4周后,处死小鼠,比较肿瘤的体积、质量、计算抑瘤率;HE染色观察肿瘤组织病理学改变。结果:131I-CD133抗体标记率为89.34%,放化纯度为98.21%。流式显示分选前后CD133表达率分别为(1.78±0.54)%和(98.46±0.97)%。成球实验、克隆形成实验和裸鼠成瘤实验显现CD133细胞相对于CD133-细胞更具有干细胞特性。131I-CD133抗体治疗组体外对细胞抑制率及体内抑瘤率明显高于其余各实验组,差异具有统计学意义(P<0.05)。结论:131I-CD133抗体在体内外均能有效抑制人肝癌CD133-HepG2细胞的生长。 相似文献
996.
目的 通过比较羧甲司坦单用或联合布地奈德对人气道上皮细胞炎症的影响探讨其调控机制。方法MTT 法检测不同浓度烟雾提取物(CSE)对细胞生存率的影响。给予不同药物抑制剂和激动剂干预后,检测炎症因子水平、ERK 和IκBα 蛋白,以及ERK 和NF-κB mRNA 的表达。结果 模型组炎症因子水平、p-ERK 和p-IκBα 蛋白,以及ERK 和NF-κB mRNA 表达均增高;用药组上述指标较模型组均有所改善,但用药组之间比较差异无统计学意义(P >0.05)。羧甲司坦、PD98059 干预后p-ERK 蛋白及ERK、NF-κBmRNA 水平均降低,而给予EGF 干预后上述指标较羧甲司坦组有所回升。结论 羧甲司坦的抗炎机制可能与糖皮质激素存在重叠,基础应用糖皮质激素者由于抑制了相同的信号转导通路,故再联合应用羧甲司坦时效果不佳。 相似文献
997.
目的 探讨糖尿病对老年患者行非体外循环冠状动脉旁路移植术( off-pump coronary artery bypass grafting, OPCABG)的影响。方法 回顾性分析176例60岁以上行OPCABG患者的临床资料。根据术前是否合并糖尿病分为糖尿病组(n=86) 及非糖尿病组(n=90)。比较两组患者的一般资料及术中、术后资料,分析60岁以上糖尿病患者OPCABG近期预后的特点。结果 糖尿病组高脂血症发生率明显高于非糖尿病组,差别有统计学意义(37.2% vs 17.8%,P <0.01)。糖尿病组患者的3支血管病变及冠脉弥漫性病变的发生率明显高于非糖尿病组(83.7% vs 62.2%,P<0.05;75.6% vs 52.2%,P<0.05), 两组桥血管数(3.2±0.8 vs 2.8±0.6,P<0.05),ICU时间[(3.6±0.9) d vs (3.2±0.6) d,P<0.05]等方面差导有统计学意义。糖尿病组主动脉球囊反搏 (itraarotic ballon pumping, IABP)使用率(7% vs 1.1%,P<0.05)、肺内感染(12.8% vs 4.4%,P<0.05)、二次插管发生率(9.3% vs 2.2%,P<0.05)等显著增加。两组在呼吸机使用时间、ICU停留时间、住院时间和院内病死率等方面差异无统计学意义。结论 合并糖尿病老年患者冠脉血管病变较重,但是OPCABG总体疗效与非糖尿病患者相同。 相似文献
998.
Lee NK Kim S Kim GH Heo J Seo HI Kim TU Kang DH 《Journal of magnetic resonance imaging : JMRI》2012,35(3):678-685
Purpose:
To identify MRI biomarkers that could be used to follow disease progression and therapeutic efficacy in one individual muscle in patients with myotonic dystrophy type 1 (DM1).Materials and Methods:
Lower limb MRI and maximal ankle dorsiflexor strength assessment, using a hand‐held dynamometer, were performed in 19 DM1 patients and 6 control subjects. The volume of residual muscle tissue of Tibialis Anterior (TA) muscle was chosen as an index for muscle atrophy, and the T2‐relaxation‐time of the residual muscle tissue was measured to evaluate edema‐like lesions. The fat‐to‐water ratio was assessed using three‐point Dixon images to quantify fat infiltration in the entire muscle.Results:
The intra‐observer variability of MRI indices (~5.2% for the residual muscle tissue volume and 2.5% for the fat‐to‐water ratio) was lower than that of the dorsiflexor torque measurement (~11.5%). A high correlation (r = 0.91) was found between maximal ankle dorsiflexor strength and residual TA muscle tissue volume in DM1 patients. Increases in the fat‐to‐water ratio and T2‐relaxation‐time were associated with a decrease in maximal ankle dorsiflexor strength.Conclusion:
MRI appears as a noninvasive method which can be used to follow disease progression and therapeutic efficacy. J. Magn. Reson. Imaging 2012;35:678‐685. © 2011 Wiley Periodicals, Inc. 相似文献999.
滤泡性树突状细胞肉瘤( follicular dendritic cell sarcoma, FDCS) 是一种较罕见的树突状细胞肿瘤, 1986年首次由Monda等[1]报道。从WHO的肿瘤分类中可知, FDCS属于组织细胞和树突细胞肿瘤类[2]。该细胞群还包括组织细胞恶性肿瘤、朗汉斯组织细胞肿瘤、指状树突型细胞肿瘤。此肿瘤罕见, 患者年龄14~80岁, 中位年龄约45岁, 通常发生于中青年, 无性别差异。大部分发生于淋巴结, 常表现为无痛性淋巴结大, 约1/3病例发生于结外部位。1994年Chan等[3]首次报道2例发生于口腔的结外FDCS, 以后结外FDCS的报道逐渐增多, 有发生于扁桃体、咽部、胃、胰腺、腹膜、腹膜后、腭、小肠、肠系膜、脾、纵膈、肝脏、甲状腺、肺、乳腺、结肠等[4-19]。 相似文献
1000.