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311.
In this study, a new pressure drop method has been used to investigate the kinetics of carbon dioxide reaction with aqueous blend of 2-amino-2-ethyl-1,3-propanediol (AEPD) with piperazine (PZ). The blending of a small amount of PZ with AEPD has a significant effect on the observed rate constant, kobs. It was observed that kobs values of the blend increased more than twice than the summation of kobs values of individual alkanolamines. The reaction kinetics in this study were modeled by assuming a termolecular mechanism. The addition of 0.1 mol/L of PZ to 1 mol/L AEPD exhibited an observed rate constant, kobs of 8824.1 s−1, which is comparable to other alkanolamine mixtures. Hence, PZ/AEPD mixtures can be potentially used for rapid carbon dioxide capture.  相似文献   
312.
Group 6 transition metal dichalcogenides (TMDs), such as MoS2 and WS2 have been extensively studied for various applications while few studies have delved into other TMDs such as platinum dichalcogenides. In this work, layered crystalline and amorphous platinum disulfide (PtS2) were synthesized, characterised and their fundamental electrochemical properties were investigated. Both materials exhibited inherent oxidation and reduction reactions which would limit their operating potential window for sensing applications. Amorphous phase materials are considered to be promising electrocatalysts due to the porous, and nanostructured morphology with high concentration of unsaturated active sites. The electrocatalytic performances towards oxygen reduction (ORR) and hydrogen evolution reactions (HER) of crystalline and amorphous PtS2 were analysed. Amorphous PtS2 was found to exhibit superior electrocatalytic performances towards ORR and HER as compared to crystalline PtS2. For HER, amorphous and crystalline PtS2 have overpotential values of 0.30 V and 0.70 V (vs. RHE) at current density of 10 mA cm−2, respectively. The influence of electrochemical reduction pre-treatment on their catalytic behaviours was also investigated. Electrochemical reduction pre-treatment on both crystalline and amorphous PtS2 removed the oxidized sulfate groups and increased the proportion of Pt0 oxidation state which exposed more catalytic sites. As such, these materials were activated and displayed improved ORR and HER performances. Electrochemically reduced amorphous PtS2 outperformed the untreated counterparts and exhibited the best HER performance with overpotential of 0.17 V (vs. RHE) at current density of −10 mA cm−2. These findings provide insights into the electrochemical properties of noble metal PtS2 in both crystalline and amorphous states which can be activated by electrochemical reduction pre-treatment.  相似文献   
313.
314.
While bound organic ligands provide steric protection against aggregation for metallic nanoparticles in solution, they can block a large fraction of the surface atoms which are needed for binding in catalysis and sensing applications. In this work, highly accessible Au nanoparticles ligated with bis(diphenylphosphine) molecules are synthesized and characterized in solution. Characterization is performed using high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), ultraviolet-visible (UV-Vis) spectroscopy, and fluorescence chemisorption experiments. These synthesized nanoparticles are accessible to a 2-napthalenethiol (2-NT) probe molecule in solution. The highest 2-NT accessibility is observed when using 1,1-bis(diphenylphosphino)methane (dppm) ligand where 61 % of the total gold atoms are accessible. It is hypothesized that increasing the rigidity of the bis(diphenylphosphine) ligand increases the number of binding sites on the Au nanoparticles. These nanoparticles are catalytically active for resazurin reduction, and the resazurin reduction rate scales with the number of binding sites.  相似文献   
315.
A series of highly cross-linked polysiloxane was synthesised via hydrosilylation and condensation reaction. Structural identification using Fourier Transform Infrared (FTIR) and 1H-NMR confirmed their chemical structures. Their thermal and, mechanical properties, and crystallinity, were analysed and related to the level of cross-link density. These systems displayed elevated thermal and hardness properties at an increased cross-link density. Furthermore, the level of crystallinity was reduced as displayed by XRD analysis. Along with this observation, the calculated fractional free volume (FFV) showed a decreasing trend leading to the ‘densification’ effect. It was envisaged that the linear polysiloxane chain segments aligned parallel to each other in a triclinic crystal system to generate a crystalline domain. The spacing between these stacking chains was found to be about 7.2 Å as measured from simulated XRD pattern.  相似文献   
316.
Research on Chemical Intermediates - Gallic acid-coated magnetic nanoparticles were efficiently prepared, characterized by Fourier transform infrared spectroscopy, X-ray diffraction, vibrating...  相似文献   
317.
Production, remanufacture and waste disposal models in the literature assume that produced and recovered (repaired or remanufactured) items are of the same quality. However, a recent study considered a more realistic situation where produced and remanufactured items are incompatible. That is, they are not perceived by customers to have the same quality characteristics. This results in a lost sales situation for produced (remanufactured) items when they are requested by customers during the remanufacturing (production) period. In today’s competitive market, where firms thrive to sustain or increase the market share for their products, a stock-out situation where demand is completely lost seems to go contrary to the objectives of these firms. In reality, a firm may choose to either backorder fully or partially their unsatisfied demand. This paper extends along this line of research by modelling these stock-out situations. Several stock-out cases are considered for which mathematical models are developed and numerical examples are provided with their results discussed.  相似文献   
318.

Turbulent flow characteristics and heat transfer applications of a twisted heat exchanger with 3-lobed cross section along with Y-tape insert are numerically studied. The working fluids for the simulations are pure water and water–Al2O3 nanofluid using two-phase mixture model. The study is carried out for various nanofluid volume fractions of 0.01, 0.02 and 0.03 with Reynolds number in the range of 5000–20,000. The effect of nanoparticles in heat transfer augmentation for smooth and lobed tubes is discussed based on presenting the highest thermal performance, which is a relation between heat transfer rate and pressure loss. Results show that implementing the twisted tube with Y-tape insert enhances the heat transfer more than the twisted tube. Relative Nusselt numbers for twisted tubes decrease with Reynolds number in comparison with the plain tube. Turbulent intensity, swirl number and tangential velocity of twisted tube with insert are higher than empty twisted tube indicating that inserting the Y-tape intensifies the turbulence and disturbs the fluid flow further. On the other hand, although the twisted tube increases the pressure drop more than plain tube, the case with Y-tape drastically increases the friction factor. So, the thermal performance of twisted tube with insert is lower than empty twisted tube. Adding nanoparticles to the base fluid has different influence on the investigated cases. It augments the relative Nusselt number inside plain tube and empty twisted tube with slight increment in friction factor. Increasing the nanoparticles concentration enhances the heat transfer rates for these cases while it does not increase the relative Nusselt number inside twisted tube with Y-tape insert at high Reynolds number and nanoparticle concentration. Moreover, it can be found that twisted tube with or without Y-tape insert is more efficient at low Reynolds number in comparison with the plain tube.

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319.
320.
Depollution processes are based on a dual approach that combines catalyst design (formulation) and reactor design. This paper illustrates the interest of this approach to get innovative depollution solutions using three examples: depollution of water containing chlorophenols at trace level by hydrogenation; destruction of nitrates by hydrogenation and oxidation; combustion of diluted VOC with no extra heat supply.  相似文献   
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