全文获取类型
收费全文 | 1389篇 |
免费 | 65篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 19篇 |
综合类 | 3篇 |
化学工业 | 299篇 |
金属工艺 | 44篇 |
机械仪表 | 61篇 |
建筑科学 | 73篇 |
矿业工程 | 2篇 |
能源动力 | 173篇 |
轻工业 | 181篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 119篇 |
一般工业技术 | 224篇 |
冶金工业 | 50篇 |
原子能技术 | 4篇 |
自动化技术 | 199篇 |
出版年
2024年 | 8篇 |
2023年 | 12篇 |
2022年 | 27篇 |
2021年 | 47篇 |
2020年 | 48篇 |
2019年 | 62篇 |
2018年 | 56篇 |
2017年 | 58篇 |
2016年 | 61篇 |
2015年 | 49篇 |
2014年 | 58篇 |
2013年 | 128篇 |
2012年 | 74篇 |
2011年 | 108篇 |
2010年 | 81篇 |
2009年 | 103篇 |
2008年 | 96篇 |
2007年 | 74篇 |
2006年 | 52篇 |
2005年 | 43篇 |
2004年 | 19篇 |
2003年 | 24篇 |
2002年 | 24篇 |
2001年 | 23篇 |
2000年 | 21篇 |
1999年 | 17篇 |
1998年 | 21篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1978年 | 2篇 |
1974年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有1459条查询结果,搜索用时 15 毫秒
71.
In this study, a composite containing WC (Tungsten Carbide) and Ni was produced by two different processing routes. Electroless Ni coated WC powders were consolidated and sintered at 1200 °C. Diffusion bonding couples of WC(Ni)-electrolytic Cu, WC(Ni)-AISI 316 stainless steel and WC(Ni)-WC(Ni) were manufactured by using a preloaded compression system under Ar atmosphere. Diffusion bonding was carried out at varying bonding temperatures; 750 °C for (WC)Ni-Cu diffusion couple and 1200 °C for (WC)Ni-(WC)Ni and (WC)Ni-AISI 316 stainless steel diffusion couples. Standard metallographic techniques, Scanning Electron Microscopy and a shear test were employed to characterize the microstructure of bondline and mechanical properties of each diffusion couple, respectively. 相似文献
72.
Magalie Laniel Jean-Pierre Emond Ahmet E. Altunbas 《Sensing and Instrumentation for Food Quality and Safety》2009,3(1):34-40
The performance of radio waves in open environments has been studied for years. In contrast, the behavior of Radio Frequency
Identification (RFID) inside metal enclosed areas is not yet understood. This research project focuses on the 3-D mapping
of RFID signal strength inside a 12 m refrigerated marine container instrumented with three different types of radio frequency
(RF) emitters: 915 MHz reader; 2.45 GHz reader and 433 MHz RF transmitter. The main goal is to find a frequency/configuration
that would allow real time reading of the temperature in a shipment of perishable products using RFID. Only one frequency
and one antenna were used at a time. The RF transmitter antenna was mounted at two different places inside the container;
at the top of the front wall (facing back) and on the ceiling in the middle of the container (facing down). The signal strength
was acquired by a spectrum analyzer and its antenna was mounted on a small electric cart inside the container. The cart was
programmed to move along the length of the container and stop repeatedly, allowing three automated measures per position.
All data were analyzed in terms of power level and attenuation. The maps showed that the RFID antenna positioned at the front
of the container delivered slightly better results than the one in the middle of the ceiling. The results showed a significantly
higher performance at the 433 MHz level.
This article was presented at Food Processing Automation Conference, American Society of Agricultural and Biological Engineering
(ASABE), Providence, RI, June 28–29 2008. 相似文献
73.
Yasin Varol Hakan F. Oztop Ahmet Koca Engin Avci 《Expert systems with applications》2009,36(3):5813-5821
Forecasting of entropy generation of laminar natural convection in a partially cooled square cross-sectional room has been performed using support vector machines (SVM). The two-dimensional room was modeled as floor heating story with a window. Values of temperature and velocities were obtained by solving governing equations of natural convection with finite difference technique and using these values entropy generation was calculated with its definition. Forecasting of entropy generation due to fluid friction irreversibility (FFI) and heat transfer irreversibility (HTI) were made with known values for unknown parameters using SVM. Thus, calculation time was extremely reduced and values were obtained even for non-convergence cases. It was observed that the SVM was a strong method to predict the entropy generation without computational fluid dynamic analysis for all cases. 相似文献
74.
This work is concerned with the effects of environmental factors on the adhesion and durability characteristics of epoxy-bonded concrete prisms. The results indicate that the presence of liquid water at the interfacial zone during the epoxy injection process disrupts the initial bond configurations. The freezing and thawing up to about 40 cycles do not have a significant effect on the bond stability. An adequate degree of chemical stability is maintained in the bond line by the epoxy adhesives after 120 days of exposure to corrosive environments such as MgSO4 and MgCl2. However, there is a pronounced effect of these chemical substances on the concrete strength. The load-bearing capacity of epoxy-bonded concrete prisms decreases with increasing temperature. Despite this fact, the EP3-bonded concrete prisms give relatively high joint strengths at temperatures up to 100 °C. 相似文献
75.
76.
Ahmet Ekicibil G?kmen Bulun Selda K?l?? ?etin Zafer Dikmen ?nder Orhun Tezer F?rat Kerim K?yma? 《Journal of Superconductivity and Novel Magnetism》2012,25(2):435-440
In this study the origin of ferromagnetism in ZnO-based bulk systems has been investigated using Ni-doped ZnO samples, Zn1−x
Ni
x
O with 0.25≤x≤0.50, prepared by solid-state reactions. The structural characterizations indicated that the Ni2+ ions almost uniformly distributed in all the samples, and the samples have hexagonal wurtzite structure; however, when x is increased toward 0.50, a new NiO phase is formed. A ferromagnetism (FM) has been observed for all the samples at and below
the room temperature. In other words, the room temperature results of (M–H) curves show that the FM observed is intrinsic for all the Ni-doped ZnO samples. However, the saturated magnetizations decrease
gradually with increasing Ni concentration. This indicates that, in addition to FM, the excessive doping of Ni in ZnO also
causes an antiferromagnetic (AFM) contribution which increases with increasing Ni amount. This result is also supported by
the magnetization against temperature measurements. Furthermore, the trend of the ac-susceptibility (χ) versus temperature curves, measured under an ac-magnetic field of 100 Oe, also support our conclusion about the antiferromagnetic
contribution to ferromagnetism in our samples. 相似文献
77.
Hakan Demir Ahmet Koyun Ş. Özgür Atayılmaz Özden Ağra Ahmet Selim Dalkılıç 《Journal of Mechanical Science and Technology》2013,27(8):2497-2506
Heat transfer from finned pipes buried in the soil has been investigated using experimental, analytical and numerical techniques. The experimental setup consists of a ground source heat pump system and two separate ground heat exchangers. Constant surface temperature approach based on Carslaw and Jaeger’s theory study was used for calculating the heat transfer from the pipes analytically. The problem was modeled and solved using a CFD program numerically. Effects of the fin number, fin length and simulation time on the heat transfer rate have been investigated and compared with bare tube. A modified analytical formula was also proposed for finned pipes in this study. 相似文献
78.
The reactions of cyclohexanone-formaldehyde-resin via its hydroxy and carbonyl functional groups with a number of different reagents such as acetic anhydride, benzoyl chloride, hydroxylamine, semicarbazide, and phenyl hydrazine were studied. Melting points, IR spectrums, and solubilities in various solvents of the products were determined. 相似文献
79.
Ahmet H. Aydilek 《Canadian Metallurgical Quarterly》2007,133(1):38-42
Existing research has shown that visual input significantly contributes to learning, therefore, it is paramount to use visual tools to help demonstrate engineering concepts. One of these tools, digital image analysis, can help effectively communicate complex concepts to students in a simple and understandable format as a supplement to traditional lecturing, while simultaneously enabling students to have hands-on experience. This note describes a series of activities to incorporate digital image analysis into engineering education. The undergraduate students worked in research projects that involved image-based analysis of geomaterials. Based on these activities and the students’ response to a questionnaire, it was recognized that digital image analysis can enhance the understanding of engineering phenomena for undergraduate students. The hands-on experience and visual demonstration improved the students’ grasp of fundamental concepts in research projects. The research experience allowed the students to build a connection between the classroom and the solution of state-of-the-art engineering scientific problems. It also taught them about cooperation and teamwork, as well as academic independence. 相似文献
80.
Murat Ali Bayir Ismail H. Toroslu Ahmet Cosar 《IEEE transactions on systems, man and cybernetics. Part C, Applications and reviews》2007,37(1):147-153
Producing answers to a set of queries with common tasks efficiently is known as the multiple-query optimization (MQO) problem. Each query can have several alternative evaluation plans, each with a different set of tasks. Therefore, the goal of MQO is to choose the right set of plans for queries which minimizes the total execution time by performing common tasks only once. Since MQO is an NP-hard problem, several, mostly heuristics based, solutions have been proposed for solving it. To the best of our knowledge, this correspondence is the first attempt to solve MQO using an evolutionary technique, genetic algorithms 相似文献