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排序方式: 共有290条查询结果,搜索用时 15 毫秒
1.
2.
XPS investigation on AISI 420 stainless steel corrosion in oil and gas well environments 总被引:3,自引:0,他引:3
G. Fierro G. M. Ingo F. Mancia L. Scoppio N. Zacchetti 《Journal of Materials Science》1990,25(2):1407-1415
The corrosion behaviour of 13Cr-martensitic stainless steel (AISI 420) was investigated in CO2-H2S-Cl– environments typical of oil and gas wells under different CO2 and H2S partial pressures. The corrosion tests indicated that the AISI 420 steel was highly corrosion resistant to CO2-induced phenomena (general corrosion and carbonate S.C.C.), while in the H2S environment a high S.S.C.C. (Sulphide Stress Corrosion Cracking) susceptibility and high corrosion rates were found. Moreover, CO2 in CO2-H2S-Cl– systems inhibited general corrosion and S.S.C.C. phenomena by favouring the formation of a protective film. By means of X-ray photoelectron spectroscopy (XPS) the chemical nature of the films grown on AISI 420 in different environmental conditions was investigated and the following statements were drawn out:
Furthermore from XPS results an index of protectivenessI
p = Cr+3/ (Cr+3 + Fe
OX
was defined and related to the environmental parameter
and to the corrosion rates. 相似文献
| CO2 favours the growth of a hydrated Cr-oxide rich protective film with a low Fe-oxide and sulphide content; |
| the presence of H2S favours the formation of less protective Fe-sulphide and Fe-oxide rich layers. |
3.
The perovskite-type oxide PrCoO3 has been studied by means of X-ray photoelectron spectroscopy (XPS), reduction in H2 and X-ray diffraction. Two types of oxygen were detected: lattice oxygen (binding energy = 528.4 eV) and adsorbed oxygen (binding energy = 530.9 eV). The increase in relative intensity of the peak corresponding to the latter species after reduction of PrCo03 to 3e– per molecule is assigned to the formation of hydroxyl groups. Temperature-programmed reduction (TPR) results showed two reduction steps: to 1 e– per molecule (Co3.1 Co2+) at 475 to 635 K, and to 3e– per molecule (Co21 Co0) at 725 to 815 K. Reduction in the first and second steps occurs according to the contracting sphere model and the nucleation mechanism, respectively. Reduction of Co3+ to Co2+ causes minimal structural changes in the perovskite. Reduction to 3e– per molecule yielded Pr2O3 and metallic cobalt. After this reduction and reoxidation at 973 K, the perovskite structure was regained. By XPS and TPR it was shown that PrCo03 is more easily reducible than LaCo03. It is concluded that the cation in the A position of the structure plays a significant role in the bulk and surface properties of LnCo03 (Ln, lanthanide elements) oxides. 相似文献
4.
V.A. de la Peña O’Shea M.C. Alvarez-Galvan J. M. Campos-Martin J. L. G. Fierro 《Catalysis Letters》2005,100(1-2):105-116
A 10 wt% Co/SiO2 catalyst was prepared by the incipient wet-impregnation method and tested in Fischer–Tropsch synthesis in a slurry reactor under conditions approaching industrial practice. The catalyst precursor was investigated by X-ray diffraction (XRD), temperature-programmed reduction (TPR), transmission electron microscopy (TEM) and photoelectron spectroscopy (XPS). The XPS and XRD techniques revealed the presence of a crystalline Co3O4 spinel-type phase, while-in addition-TEM and XPS analyses pointed to the formation of another amorphous Co3O4 spinel phase, both species interacting weakly with the silica substrate. The influence of total pressure on the conversion, selectivity and stability of the catalyst was studied. Upon increasing the overall pressure from 20 to 40 bar, not only activity increased but also the catalyst are not deactivating. These results are explained in terms of an increase of gases solubility in the solvent, this increment of CO concentration in the liquid phase favours carbonyl species formation and the cobalt particles segregation that implies an increase in the metal surface area. 相似文献
5.
o-xylene hydrogenation on supported ruthenium catalysts 总被引:1,自引:0,他引:1
P. Reyes M.E. König G. Pecchi I. Concha M. López Granados J.L.G. Fierro 《Catalysis Letters》1997,46(1-2):71-75
The influence of the support on the surface properties and catalytic activity of finely divided ruthenium catalysts is reported.
The catalysts were prepared using an organometallic precursor, Ru(acac)2, and three different supports, Al2O3, TiO2 and SiO2. In order to study the influence of the particle size on the catalytic performance, the effect of the calcination temperature
was also evaluated. XPS suggests that the state of ruthenium is essentially Ru0, and chemisorption measurements indicate a decrease in metal dispersion from catalysts supported on Al2O3 > TiO2 > SiO2. The turnover number in the o-xylene hydrogenation showed significant differences depending on the support and on the particle
size. Additionally, an increase in the selectivity to cis-dimethylcyclohexane with particle size was observed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Granados M. López Galisteo F. Cabello Lambrou P. S. Alifanti M. Mariscal R. Gurbani A. Sanz J. Sobrados I. Efstathiou A. M. Fierro J. L. G. 《Topics in Catalysis》2007,42(1-4):443-447
The chemical nature of P-containing species of varying concentration present in CeO2 after impregnation with (NH4)2HPO4 and calcination at 1273 K, and their effects on the oxygen storage and release (OSR) properties of ceria are reported for
the first time. The samples were characterized by different techniques and the results were compared with those recently reported
on the same samples but calcined at 873 K. When P-containing ceria solids were calcined at 1273 K, CePO4 (monazite) was the predominant P-containing species on the surface of ceria, confirming previous studies that showed that
monazite exists for those samples in which the surface P loading (P atoms per nm−2) is larger than 5.5. For lower surface P concentrations, isolated orthophosphate units are present at the surface and within
the subsurface region of the solid. Severe sintering of CeO2 after calcination at 1273 K resulted in P concentrations >5.5 P atoms·nm−2 in all samples. Isolated PO4 units that could initially be present in the samples calcined at 873 K nucleated and CePO4 was formed when samples were calcined at 1273 K. OSR properties of CeO2 deteriorated progressively when P loading increased due to the presence of larger crystals of the very stable Ce(III) phase
of CePO4 at the surface of the P-containing ceria solids. 相似文献
7.
This paper investigates stability of nonlinear control systems under intermittent information. Following recent results in the literature, we replace the traditional periodic paradigm, where the up‐to‐date information is transmitted and control laws are executed in a periodic fashion, with the event‐triggered paradigm. Building on the small gain theorem, we develop input–output triggered control algorithms yielding stable closed‐loop systems. In other words, based on the currently available (but outdated) measurements of the outputs and external inputs of a plant, a mechanism triggering when to obtain new measurements and update the control inputs is provided. Depending on the noise in the environment, the developed algorithm yields stable, asymptotically stable, and ‐stable (with bias) closed‐loop systems. Control loops are modeled as interconnections of hybrid systems for which novel results on ‐stability are presented. The prediction of a triggering event is achieved by employing ‐gains over a finite horizon. By resorting to convex programming, a method to compute ‐gains over a finite horizon is devised. Finally, our approach is successfully applied to a trajectory tracking problem for unicycles. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
8.
Summary The solution behaviour of the polycarboxylic acid derived from scleroglucan (sclerox) has been investigated as a function of NaOH concentration and temperature by means of polarimetry and viscosimetry techniques. In comparison to the native polymer, sclerox is less sensitive to degradation at high NaOH concentration (up to NaOH equal to 0.4 M) and thermally more stable. The viscosity data show a normal polyelectrolyte effect and the polymer chains seem to be not stiff. We conclude that at high pH sclerox chains are in a flexible, probably single stranded conformation. 相似文献
9.
M. E. Borges L. Hernández J. C. Ruiz-Morales P. F. Martín-Zarza J. L. G. Fierro P. Esparza 《Clean Technologies and Environmental Policy》2017,19(8):2113-2127
This work deals with the sustainable biodiesel production from low-cost renewable feedstock (waste and non-edible oils) using a heterogeneous catalyst constituted by potassium loaded on an amorphous aluminum silicate naturally occurring as volcanic material (pumice). The main challenge to biodiesel production from low-quality oils (used oils and greases) is the high percentage of free fatty acids (FFAs) and water in the feedstock that causes undesirable side reactions. The catalytic materials studied were tested in the transesterification reaction when using low-quality oils containing a high proportion of free fatty acids (FFAs) and water. Results indicated that the amount of acid and basic sites on the catalytic surface increases upon increasing potassium loading in the catalyst, displaying better performance for biodiesel production. Indeed, the modification of the aluminum silicate substrate upon potassium incorporation results in a catalytic material containing both acidic and basic sites, which are responsible for both triglycerides transesterification and FFA esterification reactions. The studied catalyst not only showed good performance in the biodiesel production reaction but also good tolerance to FFA and water contained in the feedstock for biodiesel production. The catalytic material was microstructured by 3D printing in order to design a catalytic stirring system with high mechanical strength, efficient and reusable. The use of 3D printing in biofuel production is a novelty that brings good solutions for catalyst production. 相似文献
10.
P. Ramírez de la Piscina J. L. G. Fierro G. Muller J. Sales N. Homs 《Catalysis Letters》1992,14(1):45-49
New heterogenized Pt/Sn catalysts selective for the hydroformylation of 1-pentene have been synthesized. The complex cis-[PtCl2(PPh3)2] and the SnCl2.2H2O or SnC2O4 precursors have been anchored on silica-, magnesia- and alumina-carriers. X-ray photoelectron spectroscopy was used to determine the surface composition and the nature of the anchored species. The hydroformylation activity was found to depend on the type of support and tin precursor used. Only the silica supported catalysts were active in the hydroformylation reaction. Samples prepared from SnCl2-2H2O were 200-fold more active than those prepared from SnC2O4. Selectivity ton-hexanal of the silica-supported catalyst prepared from SnCl2-2H2O was as high as 94.4% at 39.2% conversion of 1-pentene. 相似文献