全文获取类型
收费全文 | 787篇 |
免费 | 21篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 22篇 |
化学工业 | 190篇 |
金属工艺 | 18篇 |
机械仪表 | 23篇 |
建筑科学 | 23篇 |
能源动力 | 68篇 |
轻工业 | 54篇 |
水利工程 | 3篇 |
石油天然气 | 12篇 |
无线电 | 64篇 |
一般工业技术 | 89篇 |
冶金工业 | 62篇 |
自动化技术 | 188篇 |
出版年
2023年 | 7篇 |
2022年 | 19篇 |
2021年 | 32篇 |
2020年 | 15篇 |
2019年 | 22篇 |
2018年 | 32篇 |
2017年 | 26篇 |
2016年 | 35篇 |
2015年 | 21篇 |
2014年 | 28篇 |
2013年 | 59篇 |
2012年 | 27篇 |
2011年 | 50篇 |
2010年 | 29篇 |
2009年 | 39篇 |
2008年 | 26篇 |
2007年 | 23篇 |
2006年 | 22篇 |
2005年 | 15篇 |
2004年 | 17篇 |
2003年 | 19篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 30篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 12篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 17篇 |
1988年 | 4篇 |
1987年 | 10篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1975年 | 3篇 |
1974年 | 7篇 |
1973年 | 9篇 |
1972年 | 6篇 |
1971年 | 5篇 |
排序方式: 共有816条查询结果,搜索用时 31 毫秒
31.
Simulation of a localized heating system for broiler brooding to improve energy performance
下载免费PDF全文
![点击此处可从《国际能源研究杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The aim of this work is to evaluate the performance of an innovative localized solar‐assisted pen heating system for brooding using a 3D computational simulation model of the heated space. The warm air‐curtained pen ensures acceptable temperature, air velocity, relative humidity, and air quality that meet the ventilation and heat requirements for a typical pen of 100 chicks as recommended by the American Society of Heating Refrigeration and Air Conditioning Engineers and American Society of Agricultural and Biological Engineers. The supply flow characteristics and the simulated velocity and temperature field of the curtained region were determined such that they meet the ventilation requirements and comfort criteria. Results show that air supplied at 40°C is capable of delivering the desired microenvironment at bird level while the heat input to the unit is 685 W when outdoor temperature is ?5°C. The system's energy performance was then analyzed using a prototype of 16 pens. The energy consumption of the new heating scheme consumed one third of the energy required by conventional non‐localized system. Moreover, integrating the new design with a solar system utilizing parabolic concentrators provided 72% of the power load from solar energy during a winter flock operation and 100% during other seasons. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
32.
Kamel Mohamed Faraoun 《Multimedia Tools and Applications》2017,76(5):6247-6261
We propose a new (n,n) multi-secret images sharing scheme that provides high level of provable security with fast sharing and reconstruction procedures. It uses simple Boolean operations conjointly with a secure stream cipher and a cryptographic hash function in order to enable an efficient sharing of n secret images among a set of n different participants. This approach overcomes the security weakness detected in existing similar schemes, and provides additional advantages such as high sensitivity to alterations and ability to share heterogeneous images having diverse resolutions. Obtained experimental results show the effectiveness and robustness of the method compared to existing schemes, particularly its ability to ensure higher security level with competitive computational performances. 相似文献
33.
34.
Mechanical properties of alumina-fluorapatite composites with different titania additive amounts (0, 0.5, 1, 1.4, 2, 3, 4 and 5 wt%) have been investigated between 1200 and 1600℃. The optimum values of densification and mechanical properties of composites have been reached with 1.4 wt% of titania after the sintering process at 1500℃ for 1 h. Thus, the rupture strength of alumina-26.52 wt% Fap-1.4 wt% TiO2 reaches 75 MPa. At higher temperature and beyond 1.4 wt% TiO2 ,the densification and mechanical properties were hindered by the formation of both intergranular porosity and secondary phase. X-ray diffraction (XRD) analysis of alumina-Fap-TiO2 composites shows the formation of aluminium titanate (Al2O3-TiO2:Al2TiO5 ). The 27Al magic angle scanning nuclear magnetic resonance analysis of Al2O3-Fap-TiO2 composites reveals the presence of octahedral and pentahedral aluminium and novel environment relative to tetrahedral aluminium sites. 相似文献
35.
Brahim Wael Betrouni Nacim Mestiri Makram Hamrouni Kamel 《Multimedia Tools and Applications》2019,78(10):13033-13046
Multimedia Tools and Applications - The involvement of medical imaging in medical procedures plays an important role in the diagnosis and planning of a therapeutic treatment. Computerized... 相似文献
36.
Rik Bhnemann Michael Pantic Marija Popovi Dominik Schindler Marco Tranzatto Mina Kamel Marius Grimm Jakob Widauer Roland Siegwart Juan Nieto 《野外机器人技术杂志》2019,36(1):78-103
This study describes the hardware and software systems of the Micro Aerial Vehicle (MAV) platforms used by the ETH Zurich team in the 2017 Mohamed Bin Zayed International Robotics Challenge (MBZIRC). The aim was to develop robust outdoor platforms with the autonomous capabilities required for the competition, by applying and integrating knowledge from various fields, including computer vision, sensor fusion, optimal control, and probabilistic robotics. This paper presents the major components and structures of the system architectures and reports on experimental findings for the MAV‐based challenges in the competition. Main highlights include securing the second place both in the individual search, pick, and place the task of Challenge 3 and the Grand Challenge, with autonomous landing executed in less than 1 min and a visual servoing success rate of over for object pickups. 相似文献
37.
Clear poly(methyl-methacrylate)—PMMA—dosimeter is widely used in food irradiations. Positron annihilation lifetime spectroscopy (PALS) is one of the unique tools used for studying free-volumes and open-volume type defects in solid media. The Vicker's microhardness measurements offer a simple and nondestructive tool for investigating the mechanical behavior of polymer materials. PALS as well as microhardness measurements were carried out for PMMA samples, irradiated with low- and high-linear energy transfers (LET). The low-LET irradiations were provided at lethal doses of gamma radiations for vegetative bacteria. Such irradiations showed a chain scission in the PMMA samples. High-LET irradiations showed behavior different from the low-LET ones. The observed behavior depends on the alpha particle fluence. The microhardness testing was carried out for virgin and irradiated PMMA samples at high-LET. A negative correlation was found between PALS measurements and microhardness results. The optical characteristics and structural studies for the virgin and irradiated PMMA samples were in agreement with the PALS and microhardness measurements. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
38.
The COVID-19 pandemic has affected the educational systems worldwide, leading to the near-total closures of schools, universities, and colleges. Universities need to adapt to changes to face this crisis without negatively affecting students’ performance. Accordingly, the purpose of this study is to identify and help solve to critical challenges and factors that influence the e-learning system for Computer Maintenance courses during the COVID-19 pandemic. The paper examines the effect of a hybrid modeling approach that uses Cloud Computing Services (CCS) and Virtual Reality (VR) in a Virtual Cloud Learning Environment (VCLE) system. The VCLE system provides students with various utilities and educational services such as presentation slides/text, data sharing, assignments, quizzes/tests, and chatrooms. In addition, learning through VR enables the students to simulate physical presence, and they respond well to VR environments that are closer to reality as they feel that they are an integral part of the environment. Also, the research presents a rubric assessment that the students can use to reflect on the skills they used during the course. The research findings offer useful suggestions for enabling students to become acquainted with the proposed system’s usage, especially during the COVID-19 pandemic, and for improving student achievement more than the traditional methods of learning. 相似文献
39.
Imen Gueddi Othman Nasri Kamel Ben Othman 《International Journal of Adaptive Control and Signal Processing》2020,34(1):42-62
This paper presents a new optimized interval principal component analysis applied to detect and isolate actuators faults of an autonomous spacecraft involved in the rendezvous phase of the Mars sample return mission. Based on the exploitation of various arithmetic and interval analysis properties, the new interval model is built by solving the interval eigenpairs problem via a resolution of a parametric linear programming problem. The detection and isolation phases are performed by extending the classic methods to interval-valued data. The proposed method is applied to detect and isolate actuators faults that can occur on the spacecraft's thrusters. Based on data provided by a “high fidelity” industrial simulator developed by Thales Alenia Space, the obtained results proved the effectiveness of the proposed interval fault diagnosis method on detecting and isolating thrusters' faults. 相似文献
40.