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排序方式: 共有1006条查询结果,搜索用时 140 毫秒
61.
G.K. Surya Prakash Juan C. Colmenares Patrice T. Batamack Thomas Mathew George A. Olah 《Journal of molecular catalysis. A, Chemical》2009,310(1-2):180-183
The hydrolysis of methyl bromide with neutral water is performed in the presence and absence of various amines in a batch reactor at different temperatures (50–125 °C). Screening of poly(4-vinylpyridine) as a potential reusable solid amine catalyst showed maximum efficiency. This significant enhancement in efficiency is due to the capture of HBr by solid PVP and remains phase-separated driving the reaction forward. The major advantage of this process is that the polymer can be easily regenerated and reused without loss of activity making it a very effective catalyst for the conversion of methyl halides to methanol and dimethyl ether. 相似文献
62.
Tongtao Wang Caishun Lin Feng Ye Yong Fang Jingjing Li Xindong Wang 《Electrochemistry communications》2008,10(9):1261-1263
Methanol permeation is one of the key problems for direct methanol fuel cell (DMFC) applications. It is necessary to change the structure of the cathode of membrane electrode assembly (MEA). Therefore, a novel MEA with double-layered catalyst cathode was prepared in this paper. The double-layered catalyst consists of PtRu black as inner catalyst layer and Pt black as outer catalyst layer. The inner catalyst layer is prepared for oxidation of the methanol permeated from anode. The results indicate that this double-layered catalyst reduced the effects of methanol crossover and assimilated mixed potential losses. The performance of MEA with double-layered catalyst cathode was 52.2 mW cm−2, which was a remarkable improvement compared with the performance of MEA with traditional cathode. The key factor responsible for the improved performance is the optimization of the electrode structure. 相似文献
63.
B. Levasseur 《Journal of solid state chemistry》2008,181(11):2953-2963
The effect of the rare earth in the perovskite-type mixed oxides AMnO3 (A=Y, La, Pr, Sm, Dy) on catalytic properties in methanol oxidation was investigated in this work. The perovskites were prepared by reactive grinding in order to enhance the specific surface area in comparison with other classical synthesis procedures. These catalysts were characterized by N2 adsorption, X-ray diffraction, H2 temperature-programmed reduction (TPR-H2), O2-, CH3OH- and CO2-temperature-programmed desorption (TPD). The activity of the five catalysts under study in the methanol oxidation reaction was evaluated. The behaviour of the α-O2 from the surface of the perovskite was strongly related to the nature of the A-site cation and particularly to its electronegativity but also to its density. Concerning the β-O2 from the bulk, the rare earth only induces an indirect effect notably due to structural modifications. As suggested in a previous study, the activity in methanol oxidation was directly linked with the surface oxygen density. Under an excess of α-oxygen, the reaction intermediate was found to be a monodentate carbonate that decomposes into CO2. The stability of monodentate carbonates was also found to be related to the electronegativity of the rare earth during both CH3OH- and CO2-temperature-programmed desorption. However, as soon as a lack of α-oxygen was observed in the structure, the dominant reaction intermediate was a bidentate carbonate that induces a consumption of anion vacancies in spite of the production of CO2. Nevertheless, the accumulation of these carbonates leads to a decrease in the oxidation rate since their desorption requires high temperatures. 相似文献
64.
乙酰丙酮吸光光度法测定白酒中甲醇含量 总被引:2,自引:0,他引:2
乙酰丙酮法测定白酒中甲醇是一种新的测试方法。白酒样品用高锰酸钾氧化后,加草酸除去过量的氧化剂,在pH3~4范围内,加入乙酰丙酮溶液,在沸水浴中显色,于418nm波长处测量其吸光度。方法步骤简单,具有较高的灵敏度和较高的重现性。 相似文献
65.
The adsorption of methanol in zeolites of the faujasite type with sodium and calcium counter ions is studied with quantum chemical methods. The zeolite is represented with a cluster model allowing calculations at the Møller-Plesset as well as the DFT level of theory. An adsorption energy of −62.4 kJ/mol is calculated at the MP2/TZVP//BP86/TZVP level of theory for one methanol molecule at one site II sodium cation. Insight into the adsorption process is obtained with a three-body decomposition which reveals a strong destabilisation of the adsorption strength by large, positive three-body terms, which is important for force field development. 相似文献
66.
The adsorption kinetics (by thermal desorption spectroscopy) and adsorption dynamics (by molecular beam scattering) have been determined for a number of alkanes, methanol, thiophene, and water on a silica wafer—SiO2/Si(1 1 1). No indications for bond activation were present, i.e., all probe molecules adsorb molecularly obeying 1st order kinetics. The coverage-dependent heat of adsorption has been determined accordingly. The adsorption dynamics are precursor-mediated with Kisliuk-like shapes of the adsorption probabilities at low impact energies and adsorbate-assisted adsorption at large impact energies. 相似文献
67.
Xiaogang Wang Weilin Xu Xiaochun Zhou Tianhong Lu Wei Xing Changpeng Liu Jianhui Liao 《Journal of Solid State Electrochemistry》2009,13(9):1449-1453
A prominent methanol-tolerant characteristic of the PtCeOx/C electrocatalyst was found during oxygen reduction reaction process. The carbon-supported platinum modified with cerium
oxide (PtCeOx/C) as cathode electrocatalyst for direct methanol fuel cells was prepared via a simple and effective route. The synthesized
electrocatalysts were characterized by X-ray diffraction and transmission electron microscopy. It was found that the cerium
oxide within PtCeOx/C present in an amorphous form on the carbon support surface and the PtCeOx/C possesses almost similar disordered morphological structure and slightly smaller particle size compared with the unmodified
Pt/C catalyst. 相似文献
68.
Alfonsina E. Andreatta Alberto Arce Eva Rodil Ana Soto 《The Journal of chemical thermodynamics》2009,41(12):1317-1323
Densities, dynamic viscosities, and refractive indices of the ternary system composed by methanol, methyl acetate, and 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide and the binary combinations of these constituents have been measured. The excess molar volumes as well as molar refraction and viscosity changes of mixing were calculated and fitted to the Redlich–Kister equation to determine the fitting parameters and the root-mean-square deviations. 相似文献
69.
We have investigated the effect of methanol addition on the RF8(EO)9 and RF7(EO)8 surfactant-based systems. While upon the addition of methanol the L1 micellar phase grows, the direct hexagonal (H1) and the lamellar (Lα) liquid crystals progressively melt with the increase of alcohol content. Phase behavior and SAXS measurements proved that methanol molecules interact with the oxyethylene units of the surfactant. This involves a folding up of the hydrophobic chains in the liquid crystal phases. Moreover, for the RF7(EO)8 surfactant, the cloud point curve is shifted to high temperatures upon addition of alcohol. Starting from these systems, we have prepared mesoporous materials. Results show that due to the hydrogen bonds between the alcohol and the EO groups, the hexagonal structure of the mesostructured silica obtained from RF8(EO)9 is lost when the content of CH3OH is increased. In contrast, for the compounds prepared from the RF7(EO)8-based system, the pore ordering occurs in the presence of alcohol. This phenomenon has been related to the moving of the cloud point curve toward high temperatures with the addition of methanol. Our study reveals also that under our conditions the methanol released during the hydrolysis of the silica precursor does not affect the self-assembly mechanism in a positive or negative way. 相似文献
70.
A light-modulated chemosensor for methanol has been developed by using a photochromic spirophenanthoxazine as an indicator. In such a sensor, methanol can be detected easily by colorimetric recognition with high selectivity and anti-interference. Moreover, the concentration of indicator can be modulated and manipulated by light, which provides a simple way for the detection of methanol in a wide range of detectable limit that would be useful in different detection cases. 相似文献