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921.
922.
溶胶凝胶法制备Nd2O3改性钛酸钡陶瓷的研究 总被引:13,自引:0,他引:13
The technological condition for the preparation of BaTiO3 ceramics doped with Nd2O3 by Sol-Gel was deter-mined through orthogonal experiment. When nBa(Ac)2∶nTi(OC4H9)4∶nNd2O3∶nCH3(CH2)2CH2OH∶nH2O=1.00∶1.00∶0.003∶7.30∶37.04, pH=3.5,T=25℃,the light-yellow-transparent-stable solution and thorough transparent gel was generat-ed, the transforming time of solution to gel was 25h. The crystal structure and particle size of BaTiO3 ceramics doped with Nd2O3 were studied by SEM and X-ray respectively, the type of the crystal was tetragonal, the particle size was about 24.7nm. The dielectric constant (ε) and dielectric loss (tanδ) of BaTiO3 ceramics doped with Nd2O3 were determined between 104~106Hz, and the results showed that the dielectric constant was increased obviously, the dielectric loss was decreased clear and the resistivity (ρV) was also decreased noticeably. 相似文献
923.
稳定的ZrO2基SOFC中CeO2夹层的制备方法和作用机制 总被引:1,自引:0,他引:1
Sm、Gd和Y掺杂的CeO2夹层是解决固体氧化物燃料电池的电极和电解质间物理化学性质不相容问题的最佳材料,已经展示出广泛的应用前景。本文介绍了CeO2粉体的各种合成方法以及对粉体性能的影响。综述了制备CeO2夹层薄膜的各种方法,其中包括直流反应磁控溅射(Reactively direct current magnetron sputtering)物理方法;火焰辅助气相沉积(Flame assisted vapor deposition,FAVD)和溶胶凝胶法(Sol-gel)等化学方法;电泳沉积法(Electrophoretic deposition, EPD)、丝网印刷法(Screen printing)和浸渍涂布法(dipping deposition)等陶瓷成型方法,评述了这些方法的优缺点,详细介绍了近年来采用上述方法制备的CeO2夹层薄膜的性能以及对电池性能的改进,论述了CeO2夹层提高电池性能的作用机制。综合分析了这些制备方法的异同和特点,指明了该领域的发展前景。阐述了开展CeO2夹层研究对我国SOFC发展的重大意义。 相似文献
924.
Chia‐Chin Changa Li‐Chia Chena Shyh‐Jiun Liu Hsien‐Ju Tien Hsien‐Chang Chang 《中国化学会会志》2006,53(4):839-844
The electrochemical behaviors of formaldehyde (FA) at boron‐doped diamond (BDD) electrodes are investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear scanning voltammetry (LSV) techniques. The CV results show that the oxidation reaction of FA is influenced by the hydroxyl concentration in the solution, and the peak current response with the FA concentration is linear at the range from 10 to 100 mM. The differential capacitance from EIS results indicate that the FA molecules adsorb at the BDD electrode surface at low potential (from 1.0 to 1.4 V). The kinetic studies have been examined with the various concentrations of FA, pH, and temperature. The activation energy of FA oxidation is also calculated. The results of kinetic study indicate that the adsorption of FA molecules at the BDD electrode is the rate‐determining step at low potential (from 1.0 to 1.40 V). 相似文献
925.
交联聚苯乙烯包覆二氧化锆固定相是在溶液体系中通过自由基引发乙基苯乙烯、二乙烯基苯和乙烯基二氧化锆共聚反应获得。IR和SEM表征这种填料的表面特征,考察了这种交联聚合物包覆柱填料的色谱性能和化学稳定性,并用这种填料分离了苯甲酸酯类和碱性化合物。 相似文献
926.
不同方法制备的Ni/ZrO2-CeO2-Al2O3催化剂对CH4-CO2重整反应的催化性能 总被引:16,自引:0,他引:16
采用水热合成法、溶胶凝胶法和共沉淀-负载法制备了相同NiO含量的Ni/ZrO2-CeO2-Al2O3催化剂,考察了它们在CH4-CO2重整反应中的催化性能及稳定性,测定了积碳量.用CO2程序升温脱附方法测试了它们的CO2吸附性能,用H2程序升温脱附方法测试了表面Ni的分散度.结果表明,随温度升高,CH4和CO2转化率降低的顺序是:溶胶凝胶法≈共沉淀-负载法>水热合成法,并且反应产物中n(CO)/n(H2)比随温度升高而降低.水热法和共沉淀-负载法制备的催化剂稳定性好,且前者的活性比后者高;溶胶凝胶法制得的催化剂活性较高,但易失活.积碳量大小顺序是:水热法>溶胶凝胶法>共沉淀-负载法.与其他方法制备的催化剂相比,水热法制备的催化剂对CO2的吸附量更大,\r\n而且积碳主要存在于载体上,从而保证了催化剂的稳定性. 相似文献
927.
《Electroanalysis》2005,17(3):269-274
The electrochemical behavior of nitrofurazone (NFZ) at a highly boron doped diamond (BDD) electrode was studied in Britton‐Robinson (BR) buffer using cyclic voltammetry. NFZ was directly reduced to the amine derivative (RNH2) in the pH range of 2.0 to 4.0 in a process involving six (6.0±0.4) electrons and six protons. In the range of pH 7.0 to 12 and, predominantly aqueous medium, the reduction step split into its two components: the reduction of NFZ to the radical anion (RNO2.?) and reduction of RNO2.? to hydroxylamine derivative (RNHOH) in processes involving one and three (3.1±0.1) electrons, respectively. On the anodic scan of the voltammograms and at pH 8.0, the oxidation of the hydroxylamine to the nitroso derivative (RNO), was observed in a process involving 2 (1.7±0.2) electrons and 2 protons. In addition and unreported in the literature on any electrode material, was the detection of a new oxidation peak at pH>8.0, which was observed regardless of whether NFZ had been previously reduced or not. The calculation of n, number of electrons, involved in each electrochemical step was satisfactorily accomplished using the Randles‐?evcik equation. 相似文献
928.
M Karbowiak 《Journal of solid state chemistry》2004,177(7):2415-2422
Temperature-dependent line broadening measurements of emission and excitation transitions for two intrinsic sites U(1) and U(2) of U3+ ions doped in a RbY2Cl7 single crystals as well as of U4+ ions have been performed. Values of the electron phonon (EP) coupling parameter were determined by a fit of experimentally observed line widths to an equation containing the temperature dependent broadening term due to the Raman two-phonon process. The parameters for U3+ ions in RbY2Cl7 are larger than those determined for this ion in LaCl3 host crystals. This is due to shorter M-Cl distances in RbY2Cl7 which leads to a stronger interaction of uranium with the chlorine ions and to an increase of covalency. The relatively large value determined for the multiplet of U3+ in RbY2Cl7 may result from the proximity of opposite parity 5f26d1 states. The parameters obtained for the U3+ ions are larger than those for U4+. The latter ones are affected by a stronger crystal-field (CF), however the position of the first 5f26d1 or 5f16d1 states, which for U3+ is observed at an energy of ∼15,000 cm−1 lower than for U4+, is the dominating one among the factors influencing the EP coupling strength. The EP coupling parameters for all investigated transitions of the U3+ ions are larger for U(2) than for U(1), which results mainly from the larger crystal field strength observed for the U(2) site. The differences in the EP coupling strength of the U3+ ions in the U(1) and U(2) sites are in accordance with decay times observed for emission for both sites from the multiplet. 相似文献
929.
Navío J.A. Marchena F.J. Macías M. Colón G. Avilés M.A. Sánchez-soto P.J. 《Journal of Sol-Gel Science and Technology》1997,10(2):165-175
Composite ZrO2-SiO2 powders, with different ZrO2 contents, including pure ZrO2 powders, were prepared by precipitation in SiO2 suspensions, of zirconia gels from solutions of zirconyl chloride at pH = 11. These products were investigated in connection with the phase changes in ZrO2 caused by heat-treatments. ZrO2-SiO2 mixtures containing 0–100% mol ZrO2, were studied by differential thermal analysis (DTA), X-ray powder diffraction (XRD), temperature programmed desorption combined with mass spectroscopy (TPD-MS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), to obtain information on the morphological and structural features of the particles before and during the heat treatment up to 1200°C. Specific surface areas were determined using nitrogen adsorption by the BET method. The results offer an explanation about some of the factors which can be influencing on the stabilization of metastable-cubic/tetragonal (C/T) phase of ZrO2 and the evolution of surface areas (vulcano profile) observed in the composites. 相似文献
930.
《Electroanalysis》2005,17(13):1160-1170
Analysis of aqueous solutions containing chlorinated phenol pollutants was accomplished by capillary electrophoresis with direct and indirect amperometric detection using a boron‐doped diamond microelectrode. The microelectrode was prepared by (i) coating a thin film of boron‐doped polycrystalline diamond on a sharpened platinum wire (76‐μm diameter) and (ii) sealing the coated wire in a polypropylene pipet tip. The diamond microelectrode, used in end‐column detection, exhibited a low and stable background current with low peak‐to‐peak noise and good electrochemical activity for the pollutants without any conventional pretreatment. The electrode performance was evaluated in terms of the linear dynamic range, sensitivity, limit of quantitation, and response precision for the detection of several priority pollutants (2‐chlorophenol, 3‐chlorophenol, 4‐chlorophenol, 2,4‐dichlorophenol, 2,4,6‐trichlorophenol, and pentachlorophenol). The diamond microelectrode gave good detection figures of merit for these contaminants in the direct amperometric mode with no evidence of any electrode fouling. As an example, the concentration limit of quantitation for 2‐chlorophenol was 100 nM or 13 ppb (S/N=3) and the relative standard deviation of the peak height for 9 injections was 4.7±0.5% (est. 1.1 nL inj.). The separation efficiency was greater than 100 000 plates/m for all seven solutes. The microelectrode was also employed for the indirect detection of the chlorinated phenols. In this approach, which is useful for detecting electroinactive solutes, ferrocene carboxylic acid was added to the run buffer as the electrophore. Good detection figures of merit were also achieved for the separation and detection of 2‐chlorophenol, 3‐chlorophenol, and 2,4‐dichlorophenol in this mode, although the linear dynamic range was not as wide and the limit of quantitation was not as low as in direct amperometry. For example, the concentration limit of quantitation for these pollutants was in the mid micromolar range (1–10 ppm) with excellent response reproducibility of 3.2±0.8%, or less. 相似文献