全文获取类型
收费全文 | 251篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 32篇 |
综合类 | 7篇 |
化学工业 | 52篇 |
金属工艺 | 5篇 |
机械仪表 | 5篇 |
建筑科学 | 13篇 |
矿业工程 | 2篇 |
能源动力 | 1篇 |
轻工业 | 6篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
无线电 | 28篇 |
一般工业技术 | 48篇 |
冶金工业 | 11篇 |
原子能技术 | 4篇 |
自动化技术 | 49篇 |
出版年
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 12篇 |
2017年 | 14篇 |
2016年 | 17篇 |
2015年 | 7篇 |
2014年 | 11篇 |
2013年 | 22篇 |
2012年 | 12篇 |
2011年 | 7篇 |
2010年 | 20篇 |
2009年 | 14篇 |
2008年 | 14篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有269条查询结果,搜索用时 78 毫秒
261.
The kinetics of catalytic reduction of Np(V) with formic acid in HClO4 solutions in the presence of Pd/SiO2 catalysts differing in the Pd content and size of Pd nanocrystals was studied. The reaction is a structure-insenitive catalytic process, i.e., the size effect is absent. An increase in the percentage of Pd on SiO2 leads to a decrease in the activity of the catalysis centers due to a considerable increase in the contribution of the side reaction catalytic decomposition of HCOOH with an increase in the number of active centers in the catalyst grain. The effect of the S:L ratio, concentrations of HCOOH and HClO4, and temperature on the rate of catalytic reduction of Np(V) in the presence of palladium catalysts was examined. The suggested mechanism of the catalytic reduction of Np(V) with formic acid in the presence of Pd/SiO2 involves a slow step of decomposition of the protonated species NpO2H, formed by the reaction of the NpO 2 + ion with chemisorbed hydrogen atoms Pd(H). 相似文献
262.
Mesoporous silica nanoparticles inhibit cellular respiration 总被引:1,自引:0,他引:1
Tao Z Morrow MP Asefa T Sharma KK Duncan C Anan A Penefsky HS Goodisman J Souid AK 《Nano letters》2008,8(5):1517-1526
We studied the effect of two types of mesoporous silica nanoparticles, MCM-41 and SBA-15, on mitochondrial O 2 consumption (respiration) in HL-60 (myeloid) cells, Jurkat (lymphoid) cells, and isolated mitochondria. SBA-15 inhibited cellular respiration at 25-500 microg/mL; the inhibition was concentration-dependent and time-dependent. The cellular ATP profile paralleled that of respiration. MCM-41 had no noticeable effect on respiration rate. In cells depleted of metabolic fuels, 50 microg/mL SBA-15 delayed the onset of glucose-supported respiration by 12 min and 200 microg/mL SBA-15 by 34 min; MCM-41 also delayed the onset of glucose-supported respiration. Neither SBA-15 nor MCM-41 affected cellular glutathione. Both nanoparticles inhibited respiration of isolated mitochondria and submitochondrial particles. 相似文献
263.
设计的主体是人。室内"大众化"设计以广大人民群众为核心对象,有着科学性和必然性。现阶段,它已经具备了充分并完备发展的条件,正在以低调的,但迅速的步伐走进我们的生活。本文即是试图对现阶段室内"大众化"这种设计趋向进行的解析。 相似文献
264.
Robust SuperPoll with Chaining Protocol for IEEE 802.11 Wireless LANs in Support of Multimedia Applications 总被引:3,自引:0,他引:3
Design of Wireless Local Area Networks (WLANs) needs to take into consideration the limited bandwidth available in the ISM band along with the noisy characteristics of the wireless environment and hidden terminal effects. In this paper we propose an enhancement for IEEE 802.11 standard that improves the WLAN support for multimedia applications. In the IEEE 802.11 PCF polling based protocol designed for multimedia applications support, the Point Coordinator (PC) polls each station in the Basic Service Area (BSA) individually. In the proposed SuperPoll approach the PC broadcasts at the beginning of the contention free period a SuperPoll, i.e., a message that includes the list of stations that will be polled during the current period. To improve the reliability of the polling based approach in a noisy environment, we propose to use a chaining mechanism in which each packet resends in its turn the SuperPoll message appended to its packet. We provide performance measurements of the proposed method in terms of channel efficiency and channel access time for multimedia applications that use the contention free period of IEEE 802.11 PCF. We notice that for noisy channels, the proposed method provides a dramatic throughput increase and delay decrease when compared with the Single Poll mechanism used in IEEE 802.11 PCF, thus providing better support for multimedia applications. 相似文献
265.
266.
舰载导弹在值班状态时被认为是一种舰上设备,在飞行状态时被认为是一种飞行器。GJB151B-2013中明确了舰载平台设备需进行CS106项目检测,而导弹由于并非直接与舰上电网连接,如若仍按照GJB151B-2013中规定的尖峰信号指标进行考核,明显存在过试验的情况。针对舰载导弹在电磁兼容CS106指标的裁剪需求,对其考核要求进行了充分的分析和研究,并给出了试验的裁剪建议。 相似文献
267.
Yoshio Oyumi Toshiyuki Anan Hakobu Bazaki Tadamasa Harada 《Propellants, Explosives, Pyrotechnics》1995,20(3):150-155
The site and mechanism by which iron oxide catalyst acted to enhance burning rate and produced plateau burning behavior at high pressure was studied. The condensed phase chemistry study was conducted by isothermal thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and rapid-scan FTIR spectroscopic technique. Uncatalyzed ammonium perchlorate (AP) based azide composite propellant showed unstable combustion at relatively lower pressure region. The heat balance at the buring surface would be unstable at these pressures. However, iron oxide altered the burning property of the propellant and enhanced the burning rate with the plateau-mesa burning characteristics. Such pressure insensitiveness of the burning rate indicated that the condensed phase chemistry played important role in the catalytic mechanism of action. According to the microrocket motor tests, physical effect, melted fuel binder covered the AP particles and prevented the further decomposition of AP, had not affected the plateau burning. Fe2O3 was more effective on the burning rate augmentation than Fe3O4. However, the pressure exponent of the burning rate point of view Fe3O4 was favored catalyst to the propellant used here. 相似文献
268.
The effects of storage temperature (4, 20, 30, 40, 50 °C) and atmospheric conditions in packages (vacuum, atmospheric) on degradation kinetics of monacolin K, an antihypercholesterolemic agent, in red yeast rice powder were investigated using multiresponse modeling approach. Storage of red yeast rice powder at 4 °C under vacuum package was found to enhance retention of monacolin K. Multiresponse modeling revealed degradation path of monacolin K acid form into their dehydromonacolin K and unknown product under vacuum package, while oxidized product was also formed under atmospheric package. Monacolin K lactone form and precursor were degraded into dehydromonacolin K lactone form, while degradation of dehydromonacolin K lactone form to unknown was more pronounced at temperature higher than 30 °C. Oxidized product was also generated from monacolin K lactone form in atmospheric package. High activation energy of monacolin K degradation in acid form indicated that degradation of monacolin K to their dehydromonacolin K was more susceptible to temperature change as compared to lactone form. 相似文献
269.
Hidetoshi Kawasaki Toshiyuki Anan Eishu Kimura Yoshio Oyumi 《Propellants, Explosives, Pyrotechnics》1997,22(2):87-92
In order to improve of mechanical properties at low temperature region, 3,3-bis(azidomethyl)oxetan (BAMO), 3-nitratomethyl-3-methyloxetane (NMMO) and polyester (PE) copolymer were synthesized by using polyester initiator with boron trifluoride etherate. The molar ratio of each units in the BAMO/NMMO/PE copolymer was 7.4/2.6/0.39 according to the 1H-NMR spectrum analysis and was almost exactly the same composition as the monomer fed (7/3/0.33). The relative composition of triad microstructures was same as theoretical value and they were randomly arranged. The PE, which was a replacement of 1,4-butanediol, acted as an excellent soft segment in the copolymer, and the glass transition point of the elastomer was 4.8 degrees lowered by the replacement. This effect was also verified in the mechanical properties of the composite propellant and the tensile elongation was increased from 15% to 40%percnt; at −40 °C. 相似文献