全文获取类型
收费全文 | 4907篇 |
免费 | 764篇 |
国内免费 | 206篇 |
专业分类
电工技术 | 63篇 |
综合类 | 313篇 |
化学工业 | 1688篇 |
金属工艺 | 29篇 |
机械仪表 | 35篇 |
建筑科学 | 154篇 |
矿业工程 | 1045篇 |
能源动力 | 687篇 |
轻工业 | 224篇 |
水利工程 | 18篇 |
石油天然气 | 1116篇 |
武器工业 | 6篇 |
无线电 | 72篇 |
一般工业技术 | 201篇 |
冶金工业 | 75篇 |
原子能技术 | 41篇 |
自动化技术 | 110篇 |
出版年
2024年 | 4篇 |
2023年 | 85篇 |
2022年 | 156篇 |
2021年 | 176篇 |
2020年 | 190篇 |
2019年 | 207篇 |
2018年 | 220篇 |
2017年 | 193篇 |
2016年 | 195篇 |
2015年 | 205篇 |
2014年 | 356篇 |
2013年 | 260篇 |
2012年 | 363篇 |
2011年 | 367篇 |
2010年 | 270篇 |
2009年 | 268篇 |
2008年 | 217篇 |
2007年 | 264篇 |
2006年 | 247篇 |
2005年 | 232篇 |
2004年 | 170篇 |
2003年 | 165篇 |
2002年 | 140篇 |
2001年 | 137篇 |
2000年 | 109篇 |
1999年 | 104篇 |
1998年 | 98篇 |
1997年 | 83篇 |
1996年 | 93篇 |
1995年 | 71篇 |
1994年 | 67篇 |
1993年 | 37篇 |
1992年 | 24篇 |
1991年 | 27篇 |
1990年 | 16篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1951年 | 5篇 |
排序方式: 共有5877条查询结果,搜索用时 31 毫秒
961.
962.
煤矿瓦斯抽排立眼套管安设及水泥固井工艺探讨 总被引:1,自引:0,他引:1
在煤矿瓦斯抽排立眼施工的过程中,套管安设及水泥固井是2个关键性的工序,如果出现失误,便可能产生严重的工程事故,甚至可能使整个工程报废。通过对坪上煤矿瓦斯抽排立眼工程的套管安设及水泥固井工序的施工,吸取了一些套管安设的事故教训,总结了一些套管安设、水泥固井的经验,可对今后类似工程的安全施工提供帮助。 相似文献
963.
R. A. Dawe S. Thomas 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2013,35(3):217-229
Abstract Natural gas, essentially methane, can be obtained from natural gas hydrate (NGH). NGH reserves are difficult to pinpoint in the subsurface, but large sources have been identified by seismic reflection. This is particularly so below the sea floor near continental shelf plates in the oceans deeper than 300 m as NGH is stable at 4°C and 50 bar pressure. When extracted, 1 m3 of NGH can contain 160 sm3 of gas. Currently, estimates of this gas resource are very uncertain, but recent estimates suggest perhaps 2,500 trillion sm3, but how much gas can actually be produced from these accumulations is totally unclear at present. NGH could possibly solve much of the energy needs after 2020, but safe ways of extraction still have to be designed. Possible methods include the injection of hot water or inhibitor or reduction of reservoir pressure, but none have yet been commercially tested. Great caution will be needed because catastrophic environmental damage is likely if the methane is carelessly released from the sediments. This article reviews the ‘state of the art’ of NGH. 相似文献
964.
Xinli ZHU Kailu YU Dangguo CHENG Yueping ZHANG Qing XIA Changjun LIU 《Frontiers of Chemical Engineering in China》2008,2(1):55-58
The NH3-TPD characterization was conducted to confirm that the acidity of Mo-Fe/HZSM-5 zeolite could be selectively modified via
the glow discharge plasma treatment. The plasma catalyst treatment could totally change the distribution of aromatic products
with higher methane conversion compared to the untreated catalyst. Some polycyclic aromatics such as anthracene, pyrene and
phenanthrene were also produced over the plasma treated catalyst, in addition to benzene, toluene and naphthalene, which were
normally obtained over the untreated catalyst. 相似文献
965.
采用葡萄糖溶胶-凝胶法合成了Sr2FeMoO6催化剂,研究了空气、氩气和H2/N2 3种焙烧气氛对产物的结构和性能的影响。运用X射线衍射(XRD)、程序升温还原(TPR)、傅里叶变换红外光谱(FT-IR)、比表面(BET)及磁性测量与甲烷催化燃烧活性评价等技术对所制备的样品进行了表征。XRD实验结果表明,H2/N2气氛下焙烧得到的样品是单相的双层钙钛矿结构氧化物Sr2FeMoO6,在氩气下焙烧的样品形成了主相为双层钙钛矿结构氧化物Sr2FeMoO6,同时伴有少量的SrMoO4相,但在空气下焙烧的样品中除了Sr2FeMoO6的衍射峰,还出现了强度很高的SrMoO4相的衍射峰。从TPR、FT-IR和磁性表征结果发现,不同的焙烧气氛所形成的样品程序升温还原图谱和红外光谱均有所差别,H2/N2气氛下合成的样品有较好的磁性,而氩气和空气下合成的样品的磁性几乎为零。对于H2/N2气氛下合成的单相Sr2FeMoO6样品的甲烷催化燃烧活性测试表明,甲烷燃烧起燃温度T10为475℃,完全转换温度T100为744℃,可见单相双层钙钛矿型结构化合物Sr2FeMoO6对甲烷催化燃烧也有很好的活性。 相似文献
966.
A detailed mechanism comprising the GRI-Mech natural gas combustion mechanism and recent updates to it that included soot formation and reactions involving acetylene by Frenklach and coworkers was chosen to describe the gas phase reactions in the oxidative coupling of methane (OCM). The complete mechanism was reduced for use under OCM conditions with the directed relation graph method. The mechanism reduction achieved reduction ratios of 0.55 for the number of species and 0.57 for the number of reactions when the differences in the concentrations of CH4, O2, C2H6, C2H4, and C2H2 between the original and reduced mechanisms were required to be less than 5%. 相似文献
967.
This paper briefly reviews the most important aspects of catalyst testing in packed-bed catalytic laboratory reactors to properly assess the intrinsic chemical kinetics. Next it discusses approaches to assess the kinetics of fast reactions or those accompanied with strong heat effects that cannot be performed in a packed-bed reactor configuration free from transport limitations. As an example the partial oxidation of methane is presented in a steady-state fixed bed reactor as well as in a TAP (temporal analysis of products) reactor. The continuing increase in computational power leads to more sophisticated reaction and reactor models due to the increasing use of computational chemistry and computational fluid dynamics in reaction engineering. 相似文献
968.
W. H. Cassinelli L. S. F. Feio J. C. S. Araújo C. E. Hori F. B. Noronha C. M. P. Marques J. M. C. Bueno 《Catalysis Letters》2008,120(1-2):86-94
The effect of the addition of CeO2 or La2O3 on the surface properties and catalytic behaviors of Al2O3-supported Pd catalysts was studied in the steam reforming of methane. The FTIR spectroscopy of adsorbed CO and the Pd dispersion
suggest the partial coverage of Pd0 by ceria or lanthana species. This could lead to the formation of an adduct MPd
x
O (M = Ce or La) at the surface of the metal crystallites. The addition of ceria or lanthana resulted in an increase of the
turnover rate and specific rate for steam reforming of methane. One possible explanation if that the Pd0*Pdδ+O–M interfacial species (M = Ce or La) are oxidized by H2O or CO2, promoting the O* transfer to the metal surface. This could facilitate the removal of C* species from the metal surface,
resulting in the increase of specific reaction rate and increase of the accessibility of CH4 to metal active sites. 相似文献
969.
Steam methane reforming with oxygen input is simulated in staged‐separation membrane reactors. The configuration retains the advantage of regular membrane reactors for achieving super‐equilibrium conversion, but reaction and membrane separation are carried out in two separate units. Equilibrium is assumed in the models given the excess of catalyst. The optimal pure hydrogen yield is obtained with 55% of the total membrane area allocated to the first of two modules. The performance of the process with pure oxygen input is only marginally better than with air. Oxygen must be added in split mode to reach autothermal operation for both reformer modules, and the oxygen input to each module depends on the process conditions. The effects of temperature, steam‐to‐carbon ratio and pressure of the reformer and the area of the membrane modules are investigated for various conditions. Compared with a traditional reformer with an ex situ membrane purifier downstream, the staged reactor is capable of much better pure hydrogen yield for the same autothermal reforming operating conditions. 相似文献
970.
The reduction and oxidation behaviour of oxygen carrier particles of NiO and NiAl2O4 has been investigated in a fluidized bed reactor as well as a thermogravimetric analyzer (TGA). The particles showed high reactivity and gas yield to CO2 with methane in the temperature interval 750–950°C. In the fluidized bed the yield to CO2 was between 90 and 99% using bed masses corresponding to 16–57 kg/MWfuel. Complementary experiments in a TGA at 750 and 950°C showed a clear reaction of the NiAl2O4 with CH4 at the higher temperature. There was methane released from the reactor at high degrees of solid oxidation, which is likely associated with the lack of Ni‐sites on the particles which can reform the methane. There was some carbon formation during the reduction, although the amount was minor when the gas yield to carbon dioxide and degree of oxidation of the solid was high. A simple reactor model using kinetic data from a previous study predicted the gas yield during the reduction in the fluidized bed experiments with reasonable accuracy. The oxygen carrier system investigated in this work shows high promise for use in a real CLC system, provided that the particle manufacturing process can be scaled up with reasonable cost. 相似文献