全文获取类型
收费全文 | 255篇 |
免费 | 18篇 |
国内免费 | 8篇 |
专业分类
儿科学 | 1篇 |
基础医学 | 14篇 |
口腔科学 | 4篇 |
临床医学 | 175篇 |
内科学 | 13篇 |
皮肤病学 | 1篇 |
神经病学 | 4篇 |
特种医学 | 22篇 |
外科学 | 14篇 |
综合类 | 18篇 |
预防医学 | 2篇 |
药学 | 6篇 |
中国医学 | 1篇 |
肿瘤学 | 6篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 8篇 |
2017年 | 10篇 |
2016年 | 3篇 |
2015年 | 12篇 |
2014年 | 17篇 |
2013年 | 22篇 |
2012年 | 41篇 |
2011年 | 21篇 |
2010年 | 16篇 |
2009年 | 27篇 |
2008年 | 22篇 |
2007年 | 21篇 |
2006年 | 26篇 |
2005年 | 4篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2001年 | 1篇 |
1999年 | 2篇 |
排序方式: 共有281条查询结果,搜索用时 15 毫秒
1.
目的 探讨应用超声靶向破坏微泡(UTMD)技术介导shRNA抑制小鼠肝癌细胞株JNK1基因表达的能力。方法 构建并筛选shRNA最佳表达载体。体外培养肝癌细胞Hca-F,共分为5组:A组为空白对照组;B组为shRNA质粒组;C组为脂质体组;D组为超声微泡+超声辐照组;E组为脂质体+超声微泡+超声辐照组。应用倒置荧光显微镜观察转染率;荧光定量PCR检测JNK1的mRNA水平;Western-Blot检测JNK1的蛋白质表达。结果 获得了shRNA干扰效果最好的表达载体。各组转染率比较:E组均大于B、C、D组(P均<0.05);C、D组之间差异无统计学意义(P>0.05)。荧光定量PCR和Western-Blot检测各组JNK1mRNA和蛋白表达比较:E组的JNK1mRNA和蛋白表达水平均最低(P均<0.05)。结论 脂质体转染法与UTMD技术结合可以提高小鼠肝癌细胞株JNK1 shRNA的转染效率,并能够增强基因表达的抑制效果。 相似文献
2.
超声微泡造影剂在聚焦超声开放血脑屏障中的应用 总被引:2,自引:1,他引:1
超声微泡造影剂在聚焦超声无创性开放血脑屏障的过程中具有非常重要的作用,本文就其发展历程、机制、安全性、时效和量效关系进行慨述和探讨。 相似文献
3.
超声辐射微泡剂抑制SMMC-7721移植瘤的实验研究及其作用机制探讨 总被引:2,自引:0,他引:2
目的研究低频超声辐射微泡剂对裸鼠移植肿瘤增长抑制情况和组织病理学变化,并探讨其与局部氧自由基代谢产物SOD浓度改变的关系。方法建立SMMC-7721系肝癌Balb/c裸鼠移植瘤模型,随机分为五组,对照组(A),微泡组(B),单纯超声组(C),超声微泡隔日组(D),超声微泡每日组(E)。连续一周观察肿瘤组织病理学损伤,肿瘤体积生长曲线和体积增长率。应用免疫组化的方法分析局部氧自由基代谢产物SOD的变化。分析增长率与SOD浓度之间的相关性。结果超声辐射D组、E组肿瘤体积明显小于对照组(P<0.05),超声辐射D组(73.20%±0.138%),E组(57.24%±0.1653%)肿瘤增长率明显低于对照的A组(121.24%±0.347%)、B组(123.13%±0.232%)和C组(108.74%±0.221%)(P<0.05),病理学检查见瘤内血栓形成和梗死,瘤组织细胞坏死。免疫组化法得出局部SOD阳性率D组(28.83%±2.483%)、E组(32.50%±3.017%)高于A组(11.50%±2.881%),(P<0.01)。并且SOD阳性率与肿瘤生长率间呈负相关(r=-0.663)。结论低频超声辐射微泡剂可以抑制肝癌移植瘤裸小鼠肿瘤的增长,并增加局部氧自由基代谢产物SOD浓度。肿瘤增长率与SOD浓度间有负相关关系。 相似文献
4.
Low-intensity focused ultrasound was applied with microbubbles (Definity, Lantheus Medical Imaging, North Billerica, MA, USA; 0.02 mL/kg) to produce brain lesions in 50 rats at 558 kHz. Burst sonications (burst length: 10 ms; pulse repetition frequency: 1 Hz; total exposure: 5 min; acoustic power: 0.47–1.3 W) generated ischemic or hemorrhagic lesions at the focal volume revealed by both magnetic resonance imaging and histology. Shorter burst time (2 ms) or shorter sonication time (1 min) reduced the probability of lesion production. Longer pulses (200 ms, 500 ms and continuous wave) caused significant near-field damage. Using microbubbles with focused ultrasound significantly reduced acoustic power levels and, therefore, avoided skull heating issues and potentially can extend the treatable volume of transcranial focused ultrasound to brain tissues close to the skull. 相似文献
5.
This study was aimed at assessing the effects of urokinase (UK) in combination with ultrasound and microbubbles in in vitro and in vivo thrombolytic therapy for the treatment of deep vein thrombosis (DVT). Thrombi with formation times of 1, 3, 7, 14 and 21 d were used for thrombolysis. Forty-five adult mongrel dogs were used to evaluate thrombosis in vivo. Both in vitro and in vivo analyses revealed that UK?+?microbubbles had the best effect among the combinations. Thrombolysis <7 d was more effective at a thrombolysis rate of about 50%, but the thrombolytic effect of thrombi >7 d was poor at thrombolysis rates <30%. Ultrasound?+?UK significantly increased the thrombolysis rate of thrombi <7 d. These results suggest that the combination of ultrasound with microbubble contrast agents and UK may have a synergistic effect on thrombolysis. 相似文献
6.
本文建立了超声激励下微管内微泡的有限元数值分析方法。计算结果表明微管内微泡的振动受到一定程度的限制。微泡的有效半径膨胀率和振动频率随着微管半径的减小而减小。同时,微管内微泡的形变为非球形,且程度随着入射声压幅值的增大而变得明显。因此,微管内的微泡动力学行为不同于无限大液体中。 相似文献
7.
The destruction and replenishment of microbubbles has been previously applied to estimating blood flow in the microcirculation. The rate of increase of the time–intensity curve (TIC) due to microbubbles flowing into the region-of-interest (ROI) as measured from the conventional B-mode images reflects the flow velocity. In this study, we monitored microbubble replenishment using a new proposed approach called the time–Nakagami-parameter curve (TNC) obtained from the parametric image based on the Nakagami statistical parameter for quantifying the microvascular flow velocity. The Nakagami parameter is estimated from signal envelope to reflect the backscattered statistics. The feasibility of using the TNC to estimate the microvascular flow was explored by carrying out phantom measurements and in vivo animal experiments. The rates of increase of the TIC and TNC were quantified as the rate constants βI and βN of monoexponential fitted curves, respectively. The experimental results showed that βN behaves similarly to the conventional βI in quantifying the flow velocity. Moreover, the tolerance to the effects of clutter is greater for the TNC than for the TIC, which makes it possible to use βN to differentiate various flow velocities even when the ROI contains nonperfused areas. This finding suggests that the TNC-based technique can be used as a complementary tool for the conventional TIC to improve measurement of blood flow in the microcirculation. (E-mail: ckyeh@mx.nthu.edu.tw) 相似文献
8.
干细胞移植已应用于多种疾病的治疗研究,但其效果受到移植干细胞存活率、分化率以及靶向性等因素影响.随着超声影像学技术的不断发展,超声联合微泡造影剂不仅能有效介导细胞基因转染,而且能靶向性传递移植细胞,从而提高干细胞移植效果.本文将就近年来超声联合微泡造影剂促进干细胞移植的研究进展作一综述. 相似文献
9.
低频超声辐射微泡造影剂对人乳腺癌细胞的生物学效应研究 总被引:13,自引:0,他引:13
目的观察微泡造影剂不同浓度、不同声学参数对体外培养人乳腺癌细胞的生物学效应。方法人乳腺癌细胞株MDA-MB-231,受不同剂量,频率为300kHz的超声波辐照破坏微泡声学造影剂,采用噻唑蓝(MTT)法检测细胞存活率。结果在微泡浓度为5%时,0.25W/cm2×10s与0.5W/cm2×5s组细胞存活率未见明显改变,而0.5W/cm2×10s、0.5W/cm2×20s、0.5W/cm2×40s、1.0W/cm2×10s、2.0W/cm2×10s各组与对照组比较,细胞存活率明显下降。辐照强度为0.5W/cm2、照射时间10s时,随着微泡浓度增加,超声对细胞的杀伤效应越强,与对照组相比,5%微泡浓度组P<0.05,其余各组P<0.01。结论超声破坏微泡声学造影剂对人乳腺癌细胞的杀伤程度与超声辐照时间、声强及微泡浓度有关。 相似文献
10.
Sboros V Glynos E Pye SD Moran CM Butler M Ross J Short R McDicken WN Koutsos V 《Ultrasound in medicine & biology》2006,32(4):579-585
Predicting the acoustic response of an encapsulated microbubble to ultrasound requires an accurate assessment of the mechanical properties of the microbubble shell. Atomic force microscopy (AFM) provides an unprecedented spatial and force resolution of the order of Angstroms and subnanonewtons, respectively. It is introduced here as a means to interrogate microbubbles manufactured for ultrasonic imaging. The advantage of AFM over scanning electron microscopy (SEM) is that the microbubbles need not be subjected to a low temperature or low-pressure environment. The microbubbles were interrogated in a liquid environment, which could potentially be a simulated physiological environment. AFM was used in tapping mode imaging to reveal topographical detail of biSphere microbubbles. Because microbubbles are large objects compared with the overall size of usual AFM tips, a convolution between the AFM tip and the microbubble was typical of the acquired topographies. However, a part of the top half of the bubble was imaged with nanometer resolution, and roughness measurements are reported. Force-distance curves were captured using contact mode AFM. The range of stiffness or effective spring constant of biSphere was found to be between 1 and 6 N m(-1). In conclusion, the AFM is proposed here for the first time as a tool to image the surface of bubbles at the nanometer range in liquid and to perform reproducible measurements on the mechanical properties of individual microbubbles. 相似文献