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排序方式: 共有74条查询结果,搜索用时 15 毫秒
1.
Ji-Guang LiTakayasu Ikegami Yarong WangToshiyuki Mori 《Journal of solid state chemistry》2002,168(1):52-59
A novel carbonate (co)precipitation method, employing nitrates as the starting salts and ammonium carbonate as the precipitant, has been used to synthesize nanocrystalline CeO2 and Ce1−xYxO2−x/2 (x≤0.35) solid-solutions. The resultant powders are characterized by elemental analysis, differential thermal analysis/thermogravimetry (DTA/TG), X-ray diffractometry (XRD), Brunauer-Emmett-Teller (BET) analysis, and high-resolution scanning electron microscopy (HRSEM). Due to the direct formation of carbonate solid-solutions during precipitation, Ce1−xYxO2−x/2 solid-solution oxides are formed directly during calcination at a very low temperature of ∼300°C for 2 h. The thus-produced oxide nanopowders are essentially non-agglomerated, as revealed by BET in conjunction with XRD analysis. The solubility of YO1.5 in CeO2 is determined via XRD to be somewhere in the range from 27 to 35 mol%, from which a Y2O3-related type-C phase appears in the final product. Y3+-doping promotes the formation of spherical nanoparticles, retards thermal decomposition of the precursors, and suppresses significantly crystallite coarsening of the oxides during calcination. The activation energy for crystallite coarsening increases gradually from 68.7 kJ mol−1 for pure CeO2 to 138.6 kJ mol−1 for CeO2 doped with 35 mol% YO1.5. The dopant effects on crystallite coarsening is elaborated from the view point of solid-state chemistry. 相似文献
2.
Mori Toshiyuki Drennan John Wang Yarong Li Ji-Guang Ikegami Takayasu 《Journal of Thermal Analysis and Calorimetry》2002,70(2):309-319
Doped ceria (CeO2) compounds are fluorite type oxides that show oxygen ionic conductivity higher than yttria stabilized zirconia, in oxidizing
atmosphere. In order to improve the conductivity, the effective index was suggested to maximize the oxygen ionic conductivity
in doped CeO2 based oxides. In addition, the true microstructure of doped CeO2 was observed at atomic scale for conclusion of conduction mechanism. Doped CeO2 had small domains (10-50 nm) with ordered structure in a grain. It is found that the electrolytic properties strongly depended
on the nano-structural feature at atomic scale in doped CeO2 electrolyte.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
Fe掺杂g-C3N4的制备及其可见光催化性能 总被引:1,自引:0,他引:1
以硝酸铁和三聚氰胺为原料制备不同含铁量的Fe 掺杂石墨氮化碳(g-C3N4). 采用X 射线衍射光谱(XRD)、紫外-可见(UV-Vis)光谱、傅里叶变换红外(FT-IR)光谱、电感耦合等离子体-原子发射光谱(ICP-AES)、荧光(PL)光谱、X光电子能谱(XPS)等分析手段对制备的催化剂进行了表征. 结果表明,铁以离子形式镶嵌在g-C3N4的结构单元中,影响了g-C3N4的能带结构,增加了g-C3N4对可见光的吸收,降低了光生电子-空穴对的复合几率. 以染料罗丹明B的降解为探针反应系统研究了不同含铁量对g-C3N4在可见光下催化性能的影响. 结果表明,m(Fe)/m(g-C3N4)=0.14%时,制备的Fe 掺杂g-C3N4表现出最佳的光催化性能,120 min 内罗丹明B的降解率高达99.7%,速率常数达到0.026 min-1,是纯g-C3N4的3.2 倍. 以叔丁醇、对苯醌、乙二胺四乙酸二钠为自由基(·OH)、自由基(O2-·)和空穴(hVB+)的捕获剂,研究了光催化反应机理. 相似文献
4.
Resonance Energies,Absorption Oscillator Strengths and Ionization Potentials for the Element Hassium (Z = 108) 下载免费PDF全文
On the basis of successfully predicting low-lying energy levels for the element fermium (Z = 100), we calculate the resonance energies, absorption oscillator strengths and the first ionization potential of the element hassium (Z = 108) by taking important relativistic and improved electron correlation effects into account using the multiconfiguration Dirac Fock method. These calculations are carried out with the aim of assisting experimental investigations of hassium. 相似文献
5.
在全相对论理论框架下,利用多组态Dirac-Fock(MCDF)方法,系统计算了NⅡ离子2p4f—2p3d的辐射跃迁概率,得到的结果与已有实验值符合很好.具体计算中,详细分析了相对论效应、电子关联、弛豫效应、Breit相互作用和量子电动力学(QED)效应对能级精细结构及辐射跃迁概率的影响.结果表明:相对论效应、电子关联和弛豫效应对NⅡ 2p4f-2p3d辐射跃迁概率有很重要的影响,考虑了这些效应后计算值得到明显改善. 相似文献
6.
在298.15 K下利用等温环境溶解反应热量计测定了离子液体C3MIBF4(四氟硼酸1-甲基-3-丙基咪唑)和C5MIBF4(四氟硼酸1-甲基-3-戊基咪唑)不同浓度水溶液的摩尔溶解焓(ΔsHm). 借助Pitzer电解质溶液理论, 得到了它们的标准摩尔溶解焓 和Pitzer焓参数: 和 , 并计算了表观相对摩尔焓. 根据Glasser理论计算了离子液体晶格能, 进而估算了离子液体C5MIBF4和C3MIBF4中正离子的水化焓分别为-171 kJ•mol-1 (C5MI+)和-207 kJ•mol-1 (C3MI+). 相似文献
7.
最优公交线路选择问题的数学模型及算法 总被引:1,自引:0,他引:1
公交线路选择问题是城市公共交通信息查询的重要内容,本文建立了满足不同公交线路查询者需求的最优线路选择模型并给出了相应的算法。首先通过引入各条公交线路直达最短距离矩阵构造了公交网络直达关系图(直达矩阵),在直达关系图(直达矩阵)上,利用修改了的最短路算法,即可求得最优换乘路线。根据出行者的不同需求,通过在直达关系图上定义不同的权系数,可以分别求得换乘次数最少的公交出行线路、经过站点最少的公交出行线路;通过修改最短路算法,可以求得出行耗时最少的线路及出行费用最低的线路,另外,本模型还可以综合考虑出行者的需求情况,求得出行者满意度最大的出行路线。 相似文献
8.
Ji-Guang Li Yu-Feng Hu Chuan-Wei Jin Hong-Da Chu Xiao-Ming Peng Ying-Guo Liang 《Journal of solution chemistry》2010,39(12):1877-1887
Electrical conductivities were measured for the pure ionic liquids [C6mim][Br] (1-hexyl-3-methylimidazolium bromide) and [C8mim][Br] (1-octyl-3-methylimidazolium bromide) at 0.1 MPa from 293.15 to 333.15 K. Conductivity measurements were also made
for the binary water + [C6mim][Br] and water + [C8mim][Br] systems and their ternary water + [C6mim][Br] + [C8mim][Br] system at 0.1 MPa and 293.15, 298.15, and 303.15 K. The conductivity data of the pure ionic liquids were correlated
by the VFT (Vogel-Tamman-Fulcher) equation, and the fitting parameters and mean absolute deviations were determined. New explanations
are presented for the molality-dependent behavior of the conductivity of the binary water + [C6mim][Br] and water + [C8mim][Br] systems. The generalized Young’s rule and the semi-ideal solution theory for conductivity were used to predict the
conductivities of the ternary water + [C6mim][Br] + [C8mim][Br] system from the conductivities of its corresponding binary water + [C6mim][Br] and water + [C8mim][Br] subsystems. The predictions are in good agreement with the measured values. 相似文献
9.
Daiwon Choi Donghai Wang Vish V. Viswanathan In-Tae Bae Wei Wang Zimin Nie Ji-Guang Zhang Gordon L. Graff Jun Liu Zhenguo Yang Tien Duong 《Electrochemistry communications》2010,12(3):378-381
Li-ion batteries made from LiFePO4 cathode and anatase TiO2/graphene composite anode were investigated for potential application in stationary energy storage. Fine-structured LiFePO4 was synthesized by a novel molten surfactant approach whereas anatase TiO2/graphene nanocomposite was prepared via self-assembly method. The full cell that operated at 1.6 V demonstrated negligible fade even after more than 700 cycles at measured 1 C rate. While with relative lower energy density than traditional Li-ion chemistries interested for vehicle applications, the Li-ion batteries based on LiFePO4/TiO2 combination potentially offers long life and low cost, along with safety, all which are critical to the stationary applications. 相似文献
10.
保继光 《数学物理学报(A辑)》2002,22(3):348-352
在一般有界区域上,建立了次线性椭圆方程广义Dirichlet问题改进的正解估计和有界强解的存在性定理. 相似文献