全文获取类型
收费全文 | 560篇 |
免费 | 25篇 |
国内免费 | 1篇 |
学科分类
工业技术 | 586篇 |
出版年
2023年 | 5篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 19篇 |
2017年 | 22篇 |
2016年 | 11篇 |
2015年 | 6篇 |
2014年 | 16篇 |
2013年 | 33篇 |
2012年 | 23篇 |
2011年 | 33篇 |
2010年 | 30篇 |
2009年 | 32篇 |
2008年 | 37篇 |
2007年 | 31篇 |
2006年 | 28篇 |
2005年 | 25篇 |
2004年 | 17篇 |
2003年 | 14篇 |
2002年 | 18篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 17篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 5篇 |
1994年 | 11篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有586条查询结果,搜索用时 15 毫秒
1.
2.
Isolated rat hearts were subjected to 15, 45, or 60 minutes of global ischaemia and then fixed by perfusion at 37°C with glutaraldehyde containing various amounts of oxygen. This either had been bubbled with 100% oxygen (PO2 620 mm Hg) or with 100% nitrogen (PO2 40 mm Hg) immediately before use, or it had been routinely prepared and stored exposed to atmospheric oxygen (PO2 245 mm Hg). The ultrastructure of myocytes and endothelial cells subjected to 15 minutes of ischaemia was not affected by the treatment of the fixative. However, when the tissue subjected to longer periods of ischaemia was fixed with routinely prepared or oxygen-bubbled glutaraldehyde, ultrastructural changes characteristic of reoxygenation damage were uniformly evident in both the microvasculature and myocytes. These qualitatively distinct changes included mitochondrial swelling, cell swelling, endothelial bleb formation, and narrowing of capillary lumina. These abnormalities were not observed in tissue fixed with nitrogen-bubbled glutaraldehyde. These findings indicate that deliberate steps should be taken to reduce or eliminate dissolved oxygen from the fixatives used to study ischaemic tissues. Otherwise artefactual reoxygenation damage in vitro may occur and make valid ultrastructural interpretation difficult or impossible. 相似文献
3.
D Levine PD Barnes S Sher RC Semelka W Li CR McArdle S Worawattanakul RR Edelman 《Canadian Metallurgical Quarterly》1998,206(2):549-554
PURPOSE: To evaluate the normal appearance of fetal anatomy, the conspicuity of fetal organs, the reproducibility of images, and the limitations to image quality with the use of half-Fourier, single-shot rapid acquisition with relaxation enhancement (RARE) magnetic resonance (MR) imaging. MATERIALS AND METHODS: Fifty-four fetuses of 49 pregnancies underwent MR imaging with the half-Fourier, single-shot RARE technique. Two reviewers attempted to identify 47 organs and anatomic regions in each fetus. Organ or region conspicuity, image quality, and the limitations of image quality were graded. RESULTS: Fetal anatomy was well depicted in fetuses over 20 weeks in gestational age. Fetal imaging was limited by gestational age of 20 weeks or less usually owing to the small size of the organ or region being evaluated and, less frequently, by motion. CONCLUSION: Half-Fourier, single-shot RARE MR imaging provided a detailed and reproducible evaluation of normal fetal anatomy, which can be used as a standard of reference in MR imaging of fetal anomalies. 相似文献
4.
5.
6.
Graham P. Gavin Garrett B. McGuinness Finbar Dolan M.S.J. Hashmi 《International Journal of Mechanical Sciences》2007,49(3):298-305
Therapeutic ultrasound angioplasty has been investigated, clinically, by a number of researchers and represents a potentially promising therapy for the treatment of atherosclerotic lesions. To date, there has been no detailed analysis of the effect of mechanical design parameters, such as wire geometry or damping characteristics, on wire waveguide performance. An apparatus capable of delivering therapeutic ultrasound down small diameter nickel–titanium (NiTi) wire waveguides is described. The output peak-to-peak (p–p) displacements at the distal tip of a 1.0 mm diameter waveguide were measured experimentally, by means of an optical microscope and image analysis software. The output was measured for a range of waveguide lengths from 118 to 303 mm. Wire waveguide distal tip displacements as high as 98 μm (p–p) at 23.5 kHz were measured. For the range of lengths tested, the experimental measurements show the critical relationship between the length of the waveguide and the output distal tip displacements. A finite element model that can predict the resonant frequencies and distal tip displacements of various wire waveguide geometries and configurations, including the effect of damping, is presented. This numerical model has been validated against the experimental displacement data obtained. This will be a valuable design tool for ensuring the safety and effectiveness of therapeutic ultrasound angioplasty procedures. 相似文献
7.
The activation of propane using zeolite H-Y and Ga3+ exchanged zeolite Y indicates that in the presence of Ga3+ the mechanism of propane activation is changed from a cracking pathway to a dehydrogenation pathway. The presence of both Ga3+ and H+ are required to achieve this effect. 相似文献
8.
L. B. Gavin A. S. Mul'gi V. V. Shor 《Journal of Engineering Physics and Thermophysics》1986,50(5):505-511
Temperature and momentum distributions of the carrier phase are determined experimentally and compared to results of numerical calculations using the (k–) model.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 50, No. 5, pp. 735–743, May, 1986. 相似文献
9.
The concentration fields of disperse impurity are calculated on the basis of a k- model of turbulence in a wide range of Stokes numbers.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 4, pp. 548–555, October, 1985. 相似文献
10.
Silicon - Inverted pyramid (IP) texturization on silicon wafers has recently attracted attention for the structure’s light trapping ability and low specific surface area. The later property... 相似文献