全文获取类型
收费全文 | 516篇 |
免费 | 21篇 |
专业分类
电工技术 | 17篇 |
综合类 | 1篇 |
化学工业 | 128篇 |
金属工艺 | 17篇 |
机械仪表 | 15篇 |
建筑科学 | 13篇 |
能源动力 | 12篇 |
轻工业 | 31篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 70篇 |
一般工业技术 | 93篇 |
冶金工业 | 90篇 |
原子能技术 | 15篇 |
自动化技术 | 31篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 18篇 |
2013年 | 16篇 |
2012年 | 29篇 |
2011年 | 27篇 |
2010年 | 22篇 |
2009年 | 37篇 |
2008年 | 30篇 |
2007年 | 23篇 |
2006年 | 11篇 |
2005年 | 17篇 |
2004年 | 18篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1998年 | 40篇 |
1997年 | 30篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1969年 | 2篇 |
排序方式: 共有537条查询结果,搜索用时 15 毫秒
11.
The kinetic parameters of the first stage of polystyrene degradation have been investigated to elucidate the reaction mechanisms using the flow reactor system. The decrease in molecular weight of polystyrene was recorded at minute intervals over the temperature range 310°–390°C. Generally, the first and second stages were observed by thermogravimetric analysis (t.g.a.), however in the early stage of the degradation volatile yields of at least 5% occurred. Therefore, using t.g.a. analysis it is difficult to detect this earlier stage. It became evident that the first stage in the earlier part of the reaction could be detected by g.p.c. analysis. We have observed the hidden kinetic parameters of the nature of the first stage of the polystyrene degradation. The results indicate that the main chains were degraded randomly with the small quantitative volatile groups in the first stage and the rates of decrease in molecular weight in the first stage against reaction temperatures were evaluated as log ks = 12.0 ? 41300/RT. 相似文献
12.
A new non-heating technique was developed for the sterilization of food stuff. Applying a roller compactor, ultra-high pressure sterilization has experimentally demonstrated its ability to sterilize dry powders, such as corn flour and Chinese herbs, with little quality deterioration. Also, the degree of food sterilization was found correlated well with the linear press forces between the rollers, roller gaps, and number of compaction passes. In comparison to the conventional high pressure sterilization technique, the new dry continuous processing method has the advantage of lower investment cost and is more versatile for sterilizing various food powders. 相似文献
13.
At temperature above 300°C the glycosyl units of cellulose are simultaneously depolymerized to a tar and decomposed to a char by evolution of H2O, CO, and CO2. When the glycosyl units are depleted, a stable char is formed containing about 30% aliphatic and 70% aromatic components. The aliphatic component is formed first, but on further heating is converted to polycyclic aromatic structures. The chars formed at lower temperatures are more combustible because the aliphatic component of the char is highly pyrophoric and is oxidized almost at the same temperature at which it is formed (~360°C). The aromatic component, however, is less reactive and is oxidized at ~520°C. Consequently, the chars formed at higher temperatures are less combustible. It has been shown that (NH4)2HPO4, which is a well-known flame retardant and smoldering inhibitor, lowers the pyrolysis temperature and increases the char yield by accelerating the decomposition reactions. This affects the composition of the intermediate chars but the final products have about the same composition irrespective of additives. (NH4)2HPO4 also lowers the rate of oxidation of the aromatic component and the corresponding heat release. NaCl, which is an enhancer of smoldering combustion, has a slight stabilizing effect on pyrolysis of cellulose. It lowers the oxidation temperature of the aromatic component and dramatically increases its rate. The corresponding heat release is also increased due to complete oxidation to CO2. The rate of oxidation calculated from the dynamic thermal analysis data is more than tripled by NaCl and significantly reduced by (NH4)2HPO4. 相似文献
14.
Toshiji Mukai T. G. Nieh Yoshihito Kawamura Akihisa Inoue Kenji Higashi 《Intermetallics》2002,10(11-12)
Mechanical deformation of Pd40Ni40P20 was characterized in compression over a wide strain rate range (3.3×10−5 to 2×103 s−1) at room temperature. The compression sample fractured with a shear plane inclined 42 degree with respect to the loading axis, in contrast to 56 degree for the case of tension. This suggests the yielding of the material deviates from the classical von Mises yield criterion, but follows the Mohr-Coulomb yield criterion. Fracture stress as well as strain was found to decrease with increasing applied strain rate. The compressive stress (1.74 GPa) was also found to be higher than the tensile fracture stress at a quasi-static strain rate. Close examination of the stress–strain curves revealed that localized shear might have occurred at a compressive stress of about 1.4 GPa, much lower than the “apparent” yield stress of 1.74 GPa. However, the stress of 1.4 GPa for shear band initiation is almost the same as the fracture stress measured at a dynamic strain rate of 5×102 s−1. These results suggested that the fracture of a bulk metallic glass is sensitive to the applied loading rate. 相似文献
15.
Artificial Life and Robotics - This study considers an autonomous mobile vehicle using SLAM technology in an unknown environment. The focused problem is the decrease of trajectory following... 相似文献
16.
17.
Jun Xin Jianjun Li Anthony Vetro Shun-ichi Sekiguchi 《Multimedia Tools and Applications》2007,35(2):203-223
This paper describes novel transcoding techniques aimed for low-complexity MPEG-2 to H.264/AVC transcoding. An important application
for this type of conversion is efficient storage of broadcast video in consumer devices. The architecture for such a system
is presented, which includes novel motion mapping and mode decision algorithms. For the motion mapping, two algorithms are
presented. Both efficiently map incoming MPEG-2 motion vectors to outgoing H.264/AVC motion vectors regardless of the block
sizes that the motion vectors correspond to. In addition, the algorithm maps motion vectors to different reference pictures,
which is useful for picture type conversion and prediction from multiple reference pictures. We also propose an efficient
rate-distortion optimised macroblock coding mode decision algorithm, which first evaluates candidate modes based on a simple
cost function so that a reduced set of candidate modes is formed, then based on this reduced set, we evaluate the more complex
Lagrangian cost calculation to determine the coding mode. Extensive simulation results show that our proposed transcoder incorporating
the proposed algorithms achieves very good rate-distortion performance with low complexity. Compared with the cascaded decoder-encoder
solution, the coding efficiency is maintained while the complexity is significantly reduced.
相似文献
Shun-ichi SekiguchiEmail: |
18.
J. Hu Y. Bando J. Zhan X. Yuan T. Sekiguchi D. Golberg 《Advanced materials (Deerfield Beach, Fla.)》2005,17(8)
The inside cover shows a scanning electron micrograph of a novel hierarchical heterostructures, as reported by Hu and co‐workers on p. 971. The heterostructures are formed from Si core microwires covered by dense, aligned SiO2 nanowires, thus forming multiple junctions to the cores. The inset shows a schematic of the Sn‐catalyzed vapor–liquid–solid growth mechanism. These materials are envisaged to become important for optical fibers, low‐dimensional waveguides, scanning near‐field optical microscopes and high‐bandwidth optical signal processing devices. 相似文献
19.
Thermal effects on welded joints between fiber-reinforced thermoplastics (FRTPs) and metals have been investigated theoretically and experimentally. Because FRTPs use thermoplastics as the matrix resin, they have advantages over fiber-reinforced thermoset plastics (FRPs or FRSPs), including the ability to be welded. When dissimilar materials are welded together, however, thermal stress occurs due to the different thermal expansions of the materials and affects the energy release rate of the joint. Therefore, a method for evaluating the true energy release rate, including the effect of thermal stress, is necessary for strength evaluation tests. Although several theories that compensate for the thermal stress and evaluate the true energy release rate have already been proposed, they require parameters that are difficult to measure. Therefore, it is difficult to apply them in experimental investigations. In this article, a theoretical method with easily measurable parameters is proposed to calculate the energy release rate of welded double cantilever beam (DCB) joints. The effect of the thermal stress on the critical energy release rate is discussed in terms of the experimental results of a welded DCB specimen composed of a FRTP and an aluminum alloy. 相似文献
20.