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71.
以乙二胺四乙酸(EDTA)为螯合剂,用一种改进的共沉淀法制备了 Yb3+/Er3+共掺的立方相NaYF4和Yb3+/Er3+/Gd3+三掺的六角相NaYF4纳米晶。用透射电子显微镜、X射线衍射、荧光光谱等测量手段对样品的形貌、晶相和发光性能进行了表征。结果表明,通过掺杂Gd3+,实现了NaYF4基质从立方相到六角相的相变。虽然据报道六角相的NaYF4比立方相的NaYF4上转换效率高,但是相变对上转换荧光光谱的影响还不清楚。本文着重研究了相变对晶格场能级分裂、发光强度和发光颜色的调控作用,提出了荧光增强和发光颜色可调的机理。用10 mW ,980 nm二极管激光激发,在立方相和六角相样品中均观察到肉眼可见的上转换荧光发射,分别是525/550 nm附近2 H11/2/4 S3/2→4 I15/2跃迁引起的绿光发射和657 nm附近4 F9/2→4 I15/2跃迁引起的红光发射。与立方相样品相比,六角相样品荧光发射谱线变窄,荧光强度增强了一个量级,出现了2 H9/2→4 I13/2跃迁引起的新发射峰,红绿比由2∶1增大到3∶1,这是因为六角相基质的晶格场对称性降低,于是增强了上转换荧光强度,同时六角相的晶胞体积变小,提高了掺杂离子周围的晶格场强度,导致发射谱线变锐,表明相变可以调节晶格场能级分裂,发光强度和发光颜色。 相似文献
72.
The co-precipitation of Cd, Co and Eu from seawater onto ferric hydroxide was studied, using the radioactive tracers109Cd,60Co and152–154Eu, as a function of the pH, the concentration of the collector iron, the concentration of the metal spike and the aging of the internally formed precipitate. For preconcentration purpose, a pH 9 and a 35 ppm iron concentration appeared to be suitable. At pH 8, the natural pH of seawater, the distribution coefficients for Cd, Co and Eu are 104.5, 105 and 107, respectively.On leave from: Department of Chemistry, Rammohan College, Calcutta, India. 相似文献
73.
(Pb_(0.88)Nd(0.10))(Ti_(0.92)In_(0.06)Mn_(0.2))O_3超细陶瓷粉末的制备与研究杨昆山,陈种菊,陈坚业,张惊涛(四川联合大学化学系,成都,610064)关键词超细粉,共沉淀,制备掺In2O3、Nd2O3和MnO?.. 相似文献
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Satoru Sasaki Hidetoshi Hirahara Hirokazu Nakayama 《Journal of solid state chemistry》2006,179(4):1129-1135
The intercalation of water-soluble p-sulfonated calix[4 and 6]arene (CS4 and CS6) in the interlayer of the Mg-Al and Zn-Al layered double hydroxide (LDH) by the coprecipitation method has been investigated, as well as the adsorption properties of the resulting CS/LDHs for benzyl alcohol (BA) and p-nitrophenol (NP) to prepare new microporous organic-inorganic hybrid adsorbents. The amount and arrangement of CS intercalated was different by the kind of the host metal ions. CS4 cavity axis was perpendicular for the Mg-Al LDH basal layer and parallel for the Zn-Al LDH basal layer, while CS6 cavity axis was perpendicular for both the LDH basal layers. In the BET surface area measurement, the surface area of the Zn-Al/CS4/LDH was four times than that of the Mg-Al/CS4/LDH, expecting that the former has higher adsorption capacity than the latter. In fact, the adsorption ability of the CS/LDHs for BA and NP in aqueous solution was found to be larger in the Zn-Al/CS4/LDH than in the Mg-Al/CS4/LDH. In addition, the adsorption ability of both the LDHs was larger in the CS6/LDHs than in the CS4/LDHs. These results were explained by the difference in the amount and arrangement of CS intercalated in the LDH interlayer space. 相似文献
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A.?V.?ShlyakhtinaEmail author L.?G.?Shcherbakova A.?V.?Knotko A.?V.?Steblevskii 《Journal of Solid State Electrochemistry》2004,8(9):661-667
The ordering processes in Ln2Ti2O7 (Ln=Lu, Yb, Tm) are studied by X-ray diffraction, thermal analysis, infrared absorption (IR) spectroscopy, and electrical conductivity measurements. The coprecipitation method followed by freeze-drying was used for Ln2Ti2O7 synthesis. The region of low-temperature fluorite phase existence is 600 °C<T<740 °C. The low-temperature fluorite–pyrochlore phase transition in Ln2Ti2O7 takes place at ~740–800 °C. Ln2Ti2O7 (Ln=Lu, Yb, Tm) have the structure of disordered pyrochlore with antisite Ln–Ti defects at 800 °C<T<1,100 °C.The high-temperature pyrochlore–fluorite transformation takes place in Tm2Ti2O7, Yb2Ti2O7, and Lu2Ti2O7 in air at T>1,600 °C. The conductivity values are 5·10–3 S/cm for Tm2Ti2O7, 6·10–3 S/cm for Yb2Ti2O7, and 10–2 S/cm for Lu2Ti2O7 at 740 °C. This order–disorder transition leads to a 2 orders of magnitude conductivity growth and a 10–30 times permittivity increase in Ln2Ti2O7 samples obtained at 1,700 °C.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003 相似文献
78.
Hui Zhang 《Journal of solid state chemistry》2005,178(11):3485-3493
A core-shell structured magnetic layered organic-inorganic material involving 5-aminosalicylic acid (5-ASA) intercalated Zn-Al layered double hydroxides (LDHs) and magnesium ferrite (MgFe2O4) is assembled by a coprecipitation method. The powder X-ray diffraction results show the coexistence of the clear but weak diffractions of MgFe2O4 and ordered relatively stronger reflections of 5-ASA intercalated LDHs. The TEM image of magnetic 5-ASA intercalated LDHs reveals that the LDHs layer covers the MgFe2O4 particles or their aggregates with particle size of 50-80 nm. The vibration sample magnetization (VSM) measurements exhibit the increase in saturation magnetization of magnetic 5-ASA intercalated LDHs samples with increasing amount of magnetic core. The XPS analyses account for a majority of Zn, Al and O atoms on the surface of magnetic particles. It is suggested that the magnetic core MgFe2O4 was coated with LDHs layer probably through Zn-O-Mg and Al-O-Mg linkages, and a core-shell structured model is tentatively proposed. 相似文献
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