全文获取类型
收费全文 | 271篇 |
免费 | 2篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 113篇 |
金属工艺 | 6篇 |
机械仪表 | 9篇 |
建筑科学 | 10篇 |
能源动力 | 8篇 |
轻工业 | 9篇 |
水利工程 | 1篇 |
无线电 | 19篇 |
一般工业技术 | 27篇 |
冶金工业 | 54篇 |
原子能技术 | 2篇 |
自动化技术 | 13篇 |
出版年
2021年 | 2篇 |
2019年 | 4篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2013年 | 5篇 |
2012年 | 6篇 |
2011年 | 6篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 9篇 |
2002年 | 13篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 23篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1973年 | 2篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1954年 | 1篇 |
1934年 | 1篇 |
排序方式: 共有273条查询结果,搜索用时 15 毫秒
271.
Sulzer P Mauracher A Denifl S Zappa F Ptasinska S Beikircher M Bacher A Wendt N Aleem A Rondino F Matejcik S Probst M Märk TD Scheier P 《Analytical chemistry》2007,79(17):6585-6591
Free electron attachment to the three different isomers of mononitrotoluene molecules in the gas phase is studied using a crossed electron-molecule beams technique. In contrast to previous studies for a large number of negative ions, the presently measured relative cross section curves are recorded with an electron energy resolution of better than 100 meV. For several product anions including the nitro anion NO(2)-, remarkable differences for the three isomers are observed. In almost all fragment anion efficiency curves, the 2-nitrotoluene exhibits pronounced differences from the two other isomers. In contrast, 3- and 4-nitrotoluene disagree only slightly in a few fragment anions from each other. 相似文献
272.
Municipal sewage sludge (MSS) is formed during wastewater treatment and its processing and disposal represent one of the most environmentally challenging aspects of the wastewater treating process. One disposal option currently being considered is a process involving heat treatment (to render the sludge biologically inactive) followed by dewatering, drying, pulverizing, and combustion. This research focuses on fine particle emissions from the combustion of dried, treated, MSS, cofired with either natural gas or pulverized Ohio bituminous coal as a supplemental fuel. These fuels were burned at 13 kW in a downflow laboratory combustor designed to replicate time/temperature histories and particle concentrations typical of practical combustion units yet also sufficiently well defined aerodynamically to allow elucidation of mechanisms. Size-segregated particle size distributions were obtained by isokinetic sampling followed by dilution/quenching and passage into a Berner Low-Pressure Impactor. Major and trace elements were analyzed by flame and graphite furnace atomic absorption spectroscopy. Four particle size regions were identified: furnace vapor-phase material that formed ultrafine particles either in or just before the sampling probe, submicron-sized particles formed during the combustion process, micron-sized fine particles, and larger supermicron sized bulk fly ash particles. The fuel mix appears to influence trace metal partitioning routes and the composition of fine particulate matter in the exhaust. Cofiring of MSS with coal increases the ultrafine/submicron particle emission compared to firing coal alone. This increase in ultrafine/submicron particles is most likely due to an interaction between species derived from MSS (possibly alkali metals) and those from coal (possibly sulfur and/or chlorine). Vapor-to-solid phase partitioning of arsenic and selenium is controlled by surface reaction with active surface sites during MSS combustion with either gas or coal. Co-combustion of MSS with the Ohio bituminous coal allows the arsenic and selenium to be reactively scavenged by calcium, thus changing the speciation of the trace metal emitted. Ohio bituminous coal alone contained insufficient calcium to accomplish this same scavenging effect. 相似文献
273.
Y. Liu C. BaktashJ.R. Beene C.C. HavenerH.F. Krause D.R. SchultzD.W. Stracener C.R. VaneCh. Geppert T. KesslerK. Wies K. Wendt 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(23):2771-2780
The time profiles of Cu, Sn, and Ni ions extracted from a hot-cavity resonant ionization laser ion source are investigated. The ions are produced in the ion source by three-photon resonant ionization with pulsed Ti:Sapphire lasers. Measurements show that the time spread of these ions generated within laser pulses of about 30 ns duration could be larger than 100 μs when the ions are extracted from the ion source. A one-dimensional ion-transport model using the Monte Carlo method is developed to simulate the time dependence of the ion pulses. The prediction of the model agrees reasonably well with the experimental data. To reproduce the observed ion time profiles, we find it necessary to postulate that ion-wall collisions are suppressed inside the ion source by an undetermined ion confinement mechanism and that a substantial fraction of the extracted ions are generated in the vapor-transfer tube rather than the hot cavity. Three-dimensional modeling will be necessary to understand the strong reduction in losses expected from ion-wall collisions which we interpret as evidence for confinement. 相似文献