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71.
Several five‐membered heterocyclic molecules were studied theoretically as organic hydride donors. The density functional theory and ab initio methods are employed to study the direct one‐step or multistep sequence suggested for the hydride transfer from the selected molecules: H atom/electron, electron/proton/electron or electron/H atom. Out of the three multistep mechanisms, electron/H atom seems to be a probable pathway in the presence of suitable catalyst/photoreaction that can cause ionization. In the lack of such catalyst/photoreaction, the direct hydride transfer seems to be most probable with the presence of suitable hydride acceptor. A detailed mechanism of the hydride transfer from the five‐membered heterocylic compounds is important in understanding chemical and biological reactions and required for scientifically designing and synthesizing new desired five‐membered heterocyclic compounds as organic hydride donor. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
72.
本文基于粒子群优化算法的结构预测方法结合第一性原理计算,研究了LiYH4,Li2YH5和Li3YH6在0—300 GPa压力范围内的晶体结构、电子结构、热力学和动力学稳定性.研究结果表明LiYH4-P4/nmm,Li2YH5-I4/mmm和Li3YH6-P4/nmm结构可分别在169—221 GPa,141—300 GPa和166—300 GPa压力范围内由LiH和YH3按一定配比加压合成.富氢化合物的超导电性研究成为近年来高温超导体研究领域的热点,该研究结果有希望为Li-Y-H三元体系氢化物的超导电性研究及实验合成提供数据支撑. 相似文献
73.
The mechanism of reaction Cl2+2HBr=2HCl+Br2 has been carefully investigated with density functional theory (DFT) at B3LYP/6-311G** level. A series of three-centred and four-centred transition states have been obtained. The activation energy (138.96 and
147.24 kJ/mol, respectively) of two bimolecular elementary reactions Cl2+HBr→HCl+BrCl and BrCl+HBr→HCl+Br2 is smaller than the dissociation energy of Cl2, HBr and BrCl, indicating that it is favorable for the title reaction occurring in the bimolecular form. The reaction has
been applied to the chemical engineering process of recycling Br2 from HBr. Gaseous Cl2 directly reacts with HBr gas, which produces gaseous mixtures containing Br2, and liquid Br2 and HCl are obtained by cooling the mixtures and further separated by absorption with CCl4. The recovery percentage of Br2 is more than 96%, and the Cl2 remaining in liquid Br2 is less than 3.0%. The paper provides a good example of solving the difficult problem in chemical engineering with basic
theory. 相似文献
74.
Roberto Della Pergola Luigi Garlaschelli Mario Manassero Mirella Sansoni Donatella Strumolo 《Journal of Cluster Science》2001,12(1):23-34
The cluster [HIr5(CO)12]2- (1) was prepared by condensation of [HIr4(CO)11]- and [Ir(CO)4]- (molar ratio 1:1) in refluxing THF, with almost quantitative yields. Its solid state structure was determined by X-ray diffraction at low temperature on the salt [PPh3CH2Ph]2[HIr5(CO)12]. The metal atoms define a trigonal bipyramidal arrangement. The hydride ligand was located indirectly as a bridge between apical and equatorial metal atoms. The phosphine-substituted cluster [HIr4(CO)10PPh3]- (2) was synthetized by CO displacement on [HIr4(CO)11]-, in THF at room temperature. This reaction is selective, with no traces of polysubstitution products. In the solid state, the hydride and the triphenylphosphine are axially bound on basal iridium atoms; the terminal hydrogen atom was directly located by X-ray analysis at a Ir–H distance of 1.57(9) Å. On the contrary, two isomers are present in THF solution, and they interconvert rapidly at room temperature, as shown by1H and 31P NMR spectra. 相似文献
75.
提出一种用微反应色谱法来研究甲醇气相脱水制备二甲磨灭 的色谱分析流程,可以一次性分析得到气相和液相组份的定量数据,实现在线化实时分析,避免通常必须对液相组份进行冷凝然后单独对液相组份进行化学分析,流程的安排是:首先用一个色谱柱将甲醇脱水产物中的水、甲醇、乙醇完全分离并与其他组份分开,在氢化钙转化反应器中,将已经分离的水、甲醇、乙醇集资转化成氢,用热导检测器测定,在吕接的第二个色谱柱中实现其它组份的 相似文献
76.
M. G. Vinogradov L. S. Gorshkova V. A. Pavlov O. V. Mikhalev G. V. Chel'tsova I. V. Razmanov V. A. Ferapontov O. R. Malyshev G. L. Heise 《Russian Chemical Bulletin》2000,49(3):460-465
New stereoselective reducing reagents were preparedin situ by modification of NaAlH4 with various chiral diols. The efficiency of 1,4- and 1,3-diols as chiral auxiliaries in the reactions of alkyl aryl ketones
with modified NaAlH4 was considerably higher than that of 1,2-diols. The effect of the nature of the achiral ligand additionally introduced into
the chiral hydride reagent on the enantioselectivity of ketone reduction was studied. It was proposed that the sodium cation
does not necessarily participate at the stage governing the reaction stereochemistry.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp 459–464, March, 2000. 相似文献
77.
78.
Abstract High pressure X-ray studies on CuH up to 23 GPa have been performed at room temperature using a gasketed diamond anvil cell. The experimental data on the molar volume of CuH as a function of pressure have been fitted to Murnaghan's equation of state giving a bulk modulus: B0 = 72.5±2 GPa and B0 = 2.7 ± 0.3. By comparison with the equation of state for pure copper the effective additive volume of hydrogen has been evaluated as a function of pressure. It decreases from 3.2 cm3/mol H, at ambient pressure reaching a flattening value of 1.7cm3hol H at about 60 GPa. This suggests a continuous transition of CuH from ionic or covalent character at normal pressure to metallic hydride behavior at high pressure 相似文献
79.
The AC electrical conductivity of LiBH4 was investigated below 2 GPa between 1 Hz and 1.6 MHz. The high-temperature phase has an ionic conductivity of up to 0.01 S cm?1, while the low-temperature phases have conductivities two orders of magnitude lower. All phases show an Arrhenius behaviour with activation energies E a between 0.5 and 0.7 eV, in good agreement with earlier data except for phase III, which is found to have the highest activation energy of the phases studied. The high-temperature phase has a minimum in E a near 1 GPa, close to the triple point, correlated with a sudden change in activation volume. These features may indicate an isostructural phase transition. The conductivities of the ambient temperature phases increase temporarily by an order of magnitude after transitions between these phases, probably due to new diffusion channels via structural defects. The phase diagram agrees well with earlier results. 相似文献
80.
利用前一篇论文计算所得的振动频率、转动常数和配分函数,再将常温下的无转动跃迁矩平方近似为一常数并应用于高温,进一步编制程序,计算了氢化物AlH2分子001-000跃迁带不同温度段的辐射强度和吸收系数等谱带辐射特征.论文中计算的配分函数值与高斯计算及拟合值,不管是在常温还是高温下,都吻合较好,这说明构建的模型是可靠的,可以用来进一步计算谱带强度和吸收系数;从获得不同温度段的模拟光谱辐射特征图也可以看出,本文得到的谱带特征与文献一致.这对进一步研究自由基分子高温光谱的实验和理论都具有一定的参考作用. 相似文献