全文获取类型
收费全文 | 1001篇 |
免费 | 63篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 199篇 |
金属工艺 | 19篇 |
机械仪表 | 26篇 |
建筑科学 | 46篇 |
矿业工程 | 2篇 |
能源动力 | 21篇 |
轻工业 | 133篇 |
水利工程 | 7篇 |
石油天然气 | 6篇 |
无线电 | 79篇 |
一般工业技术 | 166篇 |
冶金工业 | 162篇 |
原子能技术 | 10篇 |
自动化技术 | 185篇 |
出版年
2023年 | 9篇 |
2022年 | 13篇 |
2021年 | 42篇 |
2020年 | 22篇 |
2019年 | 35篇 |
2018年 | 45篇 |
2017年 | 34篇 |
2016年 | 47篇 |
2015年 | 21篇 |
2014年 | 40篇 |
2013年 | 72篇 |
2012年 | 50篇 |
2011年 | 72篇 |
2010年 | 48篇 |
2009年 | 51篇 |
2008年 | 47篇 |
2007年 | 44篇 |
2006年 | 30篇 |
2005年 | 25篇 |
2004年 | 22篇 |
2003年 | 15篇 |
2002年 | 20篇 |
2001年 | 14篇 |
2000年 | 13篇 |
1999年 | 14篇 |
1998年 | 39篇 |
1997年 | 25篇 |
1996年 | 16篇 |
1995年 | 20篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1981年 | 4篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1968年 | 2篇 |
1965年 | 4篇 |
排序方式: 共有1069条查询结果,搜索用时 62 毫秒
71.
72.
Image acquisition technology is improving very fast from a performance point of view. However, there are physical restrictions that can only be solved using software processing strategies. This is particularly true in the case of super resolution (SR) methodologies. SR techniques have found a fertile application field in airborne and space optical acquisition platforms. Single-frame SR methods may be advantageous for some remote-sensing platforms and acquisition time conditions. The contributions of this article are basically two: (1) to present an overview of single-frame SR methods, making a comparative analysis of their performance in different and challenging remote-sensing scenarios, and (2) to propose a new single-frame SR taxonomy, and a common validation strategy. Finally, we should emphasize that, on the one hand, this is the first time, to the best of our knowledge, that such a review and analysis of single SR methods is made in the framework of remote sensing, and, on the other hand, that the new single-frame SR taxonomy is aimed at shedding some light when classifying some types of single-frame SR methods. 相似文献
73.
Ruben GonzalezBiao Huang Fangwei XuAris Espejo Joseph AmalrajWilliam Lam 《Computers & Chemical Engineering》2011,35(3):519-529
In order to perform data reconciliation, it is important that noises in the data have well-defined distributions. The motivation behind this study was to enable the comparison between a discrete and continuous data set so that means can be compared for gross error over the short term; this required that local variables exhibit similar distributions.A case study was done on a system where non-continuum loads from a dump truck were to be reconciled with two downstream continuum weightometers. An algorithm was developed using the binomial distribution and time delay in order to simulate the effect of the dump pocket.Regression analysis based on principal components was used to evaluate the performance of the smoothing algorithm and to determine the most likely maximum hopper capacity that locates between the two weightometers. 相似文献
74.
This study reports on the development and validation of measurement scales to study the different roles fulfilled by ICT coordinators. Based on a review of the literature, a 24 item questionnaire was constructed and administered to a sample of 177 Flemish ICT coordinators working in primary education. Exploratory factor analysis revealed a four-factor solution: the ICT coordinator as a planner, a budgeter, a technician, and an educationalist. Qualitative data corroborated these roles. This study provides a quantitative measure of the different roles assumed by ICT coordinators in practice. The implications of our findings for schools, researchers and policy makers are discussed. 相似文献
75.
Diego Gutierrez Francisco J. Seron Adolfo Munoz Oscar Anson 《Computers & Graphics》2006,30(6):994-1010
This paper presents a physically based simulation of atmospheric phenomena. It takes into account the physics of non-homogeneous media in which the index of refraction varies continuously, creating curved light paths. As opposed to previous research on this area, we solve the physically based differential equation that describes the trajectory of light. We develop an accurate expression of the index of refraction in the atmosphere as a function of wavelength, based on real measured data. We also describe our atmosphere profile manager, which lets us mimic the initial conditions of real-world scenes for our simulations. The method is validated both visually (by comparing the images with the real pictures) and numerically (with the extensive literature from other areas of research such as optics or meteorology). The phenomena simulated include the inferior and superior mirages, the Fata Morgana, the Novaya–Zemlya, the Viking's end of the world, the distortions caused by heat waves and the green flash. 相似文献
76.
77.
The aim of this study was to quantify how elite high jumpers used their free limbs in a competitive high jump and to estimate the contribution that these made to vertical take-off velocity. This was achieved by analysing the competitive performances of six elite male high jumpers using 3D motion analysis and assessing limb function using the relative momentum method. The mean peak relative momentum of the arm nearest to the bar at take-off was 9.4 kg m s(-1), while that of the arm furthest away from the bar was 11.3 kg m s(-1) and these did not differ significantly. The free (lead) leg reached a mean peak relative momentum of 20.9 kg m s(-1). At touch-down the free leg had a large positive relative momentum that was offset by the negative relative momentum of the arms, although their combined value still remained positive. The mean combined free limbs' relative momentum at touch-down was 13.8 kg m s(-1) and reached a peak of 37.6 kg m s(-1). The difference between these two values amounted to 7.1 % of whole-body momentum, which was judged to be the amount by which the free limbs contributed to performance. The arms had a greater influence on performance than had the lead leg. This was because the lead leg increased its relative momentum little during the contact period while the arms had an initial negative value that increased markedly after touch-down. The compressive force exerted by the motion of the free limbs, estimated by the change in the combined free limbs' relative momentum, reached a mean peak of 366 N and was greatest at 37% of the contact period. It was concluded that to maximize the contribution the free limbs can make to performance, given the restraints imposed on technique by other performance requirements, the arms should have a vigorous downward motion at touch-down to make the most use of the high (but little changing) relative momentum of the lead leg. 相似文献
78.
The use of a fluidised bed reactor and a conductivity cell provide a technique for the study of degradation of PVC with greatly increased sensitivity. The kinetics of the reaction may be studied at 350 K and for small (1%) amounts of degradation. The effects of diffusion within the particles may be distinguished from that of diffusion in the surrounding atmosphere. The influence of temperature and particle size and sintering were examined. The catalytic effect of HCl was confirmed and an apparent activation energy of 29 kcal mol?1 was observed. 相似文献
79.
PK Woodard D Li EM Haacke PJ Dhawale S Kaushikkar B Barzilai AC Braverman PA Ludbrook AN Weiss JJ Brown SA Mirowitz TK Pilgram FR Gutierrez 《Canadian Metallurgical Quarterly》1998,170(4):883-888
OBJECTIVE: Our objective was to study the ability of three-dimensional MR angiography with retrospective respiratory gating to reveal stenoses in proximal coronary arteries on source and projection images. CONCLUSION: Proximal coronary artery stenoses can be identified using three-dimensional MR angiography with retrospective respiratory gating, both with projection images and on source images alone. Reasons for missed lesions included collateral vessels and retrograde flow distal to complete occlusion and volume averaging of vessels with adjacent structures. Causes of false-positive interpretations included small foci of decreased signal intensity distal to complete occlusion, partial volume effects on individual partitions, and regions of distal vessels leaving the imaging plane. 相似文献
80.
The experimental results presented here have been obtained on a solar chicken brooder built in the Peruvian mountains (altitude 3000m, latitude 13°S). This installation is made of adobe and part of its roof is a solar collection-storage system consisting of two tanks of paraffin-wax located below glass panes. We study the short-range and long-range fluctuations of the variables characterizing the behaviour of the system and its fitness to its purpose: breeding young chickens that must be kept in a given range of temperature, with the air regularly renewed. 相似文献