全文获取类型
收费全文 | 206篇 |
免费 | 10篇 |
国内免费 | 5篇 |
专业分类
儿科学 | 1篇 |
妇产科学 | 7篇 |
基础医学 | 24篇 |
口腔科学 | 5篇 |
临床医学 | 67篇 |
内科学 | 25篇 |
神经病学 | 1篇 |
特种医学 | 46篇 |
外科学 | 17篇 |
综合类 | 4篇 |
预防医学 | 1篇 |
眼科学 | 1篇 |
药学 | 13篇 |
肿瘤学 | 9篇 |
出版年
2019年 | 1篇 |
2017年 | 1篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有221条查询结果,搜索用时 15 毫秒
1.
Dr. P. R. Hoskins P. J. Fish W. N. McDicken C. Moran 《Medical & biological engineering & computing》1998,36(3):259-269
Many of the changes resulting from arterial disease can be measured, using Doppler ultrasound for measurement of blood velocity
and B-scan imaging for measurement of tissue structure and composition. Wall thickness, the degree of arterial narrowing and
plaque volume can be measured using B-scan imaging, and 3D ultrasound can be used to improve the accuracy of measurements
of plaque volume and for improved visualisation of complex arterial geometries. Measurement of the dynamic properties of the
arterial wall permits estimation of wall elasticity and plaque motion. From the Doppler signal, measurements of blood velocity
are used to estimate the degree of arterial narrowing and volumetric flow, although measurement errors can be large. Wall
shear stress can be estimated by measuring the velocity gradient at the vessel wall. The problems of inadequate spatial resolution
and interference from overlying tissue are largely removed when intravascular systems are used, and these have superior capability
in the assessment of arterial structure and tissue composition. However, measurement of quantities relating to blood flow
is more difficult using the intravascular approach, as the indwelling cather disturbs the blood flow pattern, and currently,
assessment of flow and vessel cross-section are not performed at the same site. 相似文献
2.
Optimal insonation settings for contrast imaging are yet to be specified, mainly due to the lack of good understanding of the behaviour of the microbubbles. A satisfactory model that explains the behaviour of individual contrast agent scatterers has not yet been reported in the literature. An in vitro system based on a commercial scanner (ATL HDI3000) has been developed to investigate the backscatter of such agents. Suspensions of Definity were introduced in an anechoic tank. The frequency of transmitted ultrasound varied from 1 to 5 MHz, pulse period from 2 to 10 periods and peak negative acoustic pressure from 0.08 to 1.7 MPa. The backscatter at the fundamental and second harmonic frequency windows from the agent was normalized in terms of the corresponding components of backscatter from a blood mimicking fluid suspension. The agent provided a dominant resonance effect at 1.6 MHz transmit frequency. Second harmonic normalized backscatter averaged around 9 dB higher than the fundamental. The normalized fundamental backscatter intensity was linear with peak negative pressure. The second harmonic at resonance peaked at 0.5 MPa suggestive of bubble disruption above such pressure. The system proved capable of illustrating the ultrasonic behaviour of Definity in vitro, and the investigation suggested particular insonation conditions for optimal image enhancement using Definity. 相似文献
3.
4.
Colour Doppler velocity imaging of the myocardium. 总被引:31,自引:0,他引:31
W N McDicken G R Sutherland C M Moran L N Gordon 《Ultrasound in medicine & biology》1992,18(6-7):651-654
A technique has been developed for producing images of the velocity of tissue motion within the myocardium. It has been demonstrated that Colour Flow Doppler imagers can be operated to depict the velocities within the myocardium rather than moving blood in the cardiac chambers. The technique exhibits the normal advantages of diagnostic ultrasound, i.e., real-time imaging with relatively inexpensive equipment and no hazard to the patient. Further work requires to be done to determine the optimum signal processing algorithms for moving tissue echoes and to ascertain whether the technique is of value in clinical applications. 相似文献
5.
A.D. Fleming W.N. McDicken G.R. Sutherland P.R. Hoskins 《Ultrasound in medicine & biology》1994,20(9):937-951
An investigation has been carried out on the velocity resolution, spatial resolution and accuracy of Doppler images as part of a study into the Doppler display of cardiac tissue motion. Test-phantoms were designed to perform this work and images were captured on a computer. The characteristics of the phantom images and of the image capture process were studied. The smallest spatial detail that was observed in the Doppler image was 3 mm by 3 mm. Doppler receive gain and Doppler ensemble size both affected velocity resolution. Different target materials gave different measures for velocity resolution. This could be related to the different back-scatter intensities of the materials. 相似文献
6.
This study details the design and construct of an anthropomorphic phantom of the oesophagus suitable for use with endoscopic ultrasound (EUS) and 3-D volume measurements. The phantom was constructed using agar-based tissue-mimicking material (TMM) of different acoustical properties to simulate various anatomical and pathologic features. The acoustical properties were measured with a scanning acoustical macroscope. An Olympus GF-UM200 echo-endoscope and digital position measurement arm were used to scan the phantom at 7.5 and 12 MHz. Comparative dimensional measurements were performed on the phantom via 2-D and 3-D EUS. TMM attenuation varied between 0.1 and 0.5 dB/cm.MHz. Backscatter power, relative to normal TMM, was from 0 to -12.2 dB, with an average speed of sound of 1537 +/- 1.9 m/s. Measurements of objects within the phantom by 2-D and 3-D EUS had mean errors of 8% and 2.2%, respectively. The construction of the anthropomorphic EUS phantom facilitated EUS training and research and development studies. 相似文献
7.
Dynamic imaging of the stomach by real-time ultrasound--a method for the study of gastric motility. 下载免费PDF全文
The use of real-time ultrasonic imaging of the stomach for the study of gastric contractions in response to a liquid test meal is described. Gastric contractions in the pyloric antrum and distal body of the stomach were observed on closed circuit television, recorded on to cassette tape and also imaged on polaroid and ciné film. Gastric contractions were recorded from the pyloric antrum by longitudinal scanning in the lower epigastrium and reproducible motility tracings were obtained on a fibreoptic chart recorded. Intravenous metoclopramide enhanced the magnitude and frequency of antral movement, which was abolished by intravenous propantheline. Real-time ultrasonic imaging permits the non-invasive study of gastric contractions. It is safe, may be repeated as required, and provides a method for the study of the effect of drugs and disease states on gastric motility. 相似文献
8.
Sboros V Moran CM Anderson T Pye SD Macleod IC Millar AM McDicken WN 《Ultrasound in medicine & biology》2000,26(1):105-111
The ultrasonic properties of microbubble contrast agents need to be fully understood if reproducible images and quantitative results are to be produced. Additional aspects of the physical and chemical environment into which the contrast agents are introduced also need to be taken into account, and their effect on contrast agent performance evaluated. A setup that provides an accurate and reproducible data-acquisition system is presented and evaluated in this paper. The linear range of this system is assessed, as well as its accuracy and precision. A new approach to the investigation of contrast agents, based on normalised backscatter, is discussed. Also, a common technique of degassing, widely used in other areas, is described and evaluated to determine its appropriateness to contrast agent studies. 相似文献
9.
S E Chambers P R Hoskins N G Haddad F D Johnstone W N McDicken B B Muir 《British journal of obstetrics and gynaecology》1989,96(7):803-808
A total of 145 pregnancies clinically suspected of being small-for-dates was studied at presentation with a single measurement of the fetal abdominal circumference and Doppler studies of the umbilical and arcuate arteries. The abdominal circumference measurement gave the best prediction of the small-for-gestational-age (SGA) baby (sensitivity 73%, umbilical artery sensitivity 47%, arcuate artery sensitivity 29%). The umbilical artery measurement gave the best prediction of antenatal fetal compromise; the performance of the tests was compared for a fixed sensitivity of 100% (i.e. all cases of antenatal compromise would be detected), the specificity of the umbilical artery measurement was 77%, abdominal circumference measurement 12% and arcuate artery measurement 2%. In our data, umbilical artery studies were not a sensitive predictor of the SGA baby but they did give an accurate prediction of the potentially compromised SGA fetus. 相似文献
10.