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排序方式: 共有223条查询结果,搜索用时 62 毫秒
61.
La2CuO4 nanofibers (ca. 30 nm in diameter and 3 μm in length) have been grown in situ by using single walled carbon nanotubes (SWNTs; ca. 2 nm in inner diameter; made via cracking CH4 over the catalyst of Mg0.8Mo0.05Ni0.10Co0.05Ox at 800 °C) as templates under mild hydrothermal conditions and a temperature around 60 °C. During synthesis, the surfactant poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) and H2O2 were added to disperse SWNTs and oxidize the reactants, respectively. The structure of La2CuO4 nanofibers was confirmed by powder X-ray diffraction (XRD) and their morphologies were observed with field emission scanning electron microscope (FESEM) at the hydrothermal synthesis lasting for 5, 20 and 40 h, respectively. The La2CuO4 crystals grew from needle-like (5 h) through stick-like (20 h) and finally to plate-like (40 h) fibers. Twenty hours is an optimum reaction time to obtain regular crystal fibers. The La2CuO4 nanofibers are probably cubic rather than round and may capsulate SWNTs. 相似文献
62.
Jiang P Chen L Lin J Liu Q Ding J Gao X Guo Z 《Chemical communications (Cambridge, England)》2002,(13):1424-1425
A novel fluorescent chemosensor (L) demonstrates a remarkable selectivity and sensitivity for zinc(II) ion as evidenced from the solution characterisations and in vitro experiments using Hela cell lines. 相似文献
63.
Nd3+-doped NaGd(MoO4)2 crystal with dimensions were grown by Czochralski method. Nd3+:NaGd(MoO4)2 crystal melts at 1182 °C. The hardness of Nd3+:NaGd(MoO4)2 crystal is 334 VDH. The specific heat is 72.6 cal/mol K. The thermal expansion coefficients are for c-axis and for a-axis, respectively. The absorption cross-sections of Nd3+:NaGd(MoO4)2 crystal are with a FWHM of 9 nm at the 804 nm for π-polarization and with a FWHM of 17 nm at 807 nm for σ-polarization, respectively. The emission cross-section σem are at 1063 nm for π-polarization and 1.94×10-20 at 1070 nm cm2 for σ-polarization, respectively. The fluorescence lifetime τf is 93.9 μs at room temperature. 相似文献
64.
In order to prevent the electrolyte decomposition of liquid state Al-plastic film lithium-ion batteries during overcharge,
the redox reactions of 2-chloro-1,4-dimethoxybenzene and 4-fluoro-1,2-dimethoxy-benzene as possible electrolyte additives
were characterized by using overcharge tests, galvanostatic charge–discharge techniques, linear sweep voltammetry tests, rate
capability tests, and cycling tests. Results indicate that for both additives, the initial charge reaction occurred at 4.1 V
and their redox products were shuttled between the cathode and anode. The shuttle reactions will consume excess current, thus
resulting in an improvement on overcharge performance for the batteries. In addition, the additives had little negative effects
on the electrochemical performance when the current was low. 相似文献
65.
66.
Guangyan Yu Lizhen Guo Feiyun Xie Bixia Yao Qingle Zeng Wen Weng 《Chromatographia》2011,73(11-12):1049-1055
A β-cyclodextrin (β-CD) and a hydroxypropyl-β-cyclodextrin (HP-β-CD) bonded chiral stationary phase (CSP) were prepared. Comparative evaluations of these two CSPs for the enantioseparation of hydrobenzoin, benzoin and α-phenethyl alcohol by reversed-phase liquid chromatography were presented. The effects of buffer composition in the mobile phase on the retention and enantioseparation were investigated. The borate buffer had a significant influence on the retention and enantioseparation of hydrobenzoin. Linear solvent strength retention model was used to fit the chromatographic data. Good linearity existed between the logarithm of retention factor (k) and the volume fraction of organic modifier (φ). Another retention model, stoichiometric displacement theory for retention, was also tried to fit the chromatographic data. The results showed that not only acetonitrile, but also water molecules participated in the displacing process of the solute. 相似文献
67.
68.
Surface‐bonded zwitterionic stationary phases have shown highlighted performances in separation of polar and hydrophilic compounds under hydrophilic interaction chromatography mode. So, it would be helpful to evaluate the characteristics of zwitterionic stationary phases with different arranged charged groups. The present work involved the preparation and comparison of three zwitterionic stationary phases. An imidazolium ionic liquid was designed and synthesized, and the cationic and anionic moieties respectively possessed positively charged imidazolium ring and negatively charged sulfonic groups. Then, the prepared ionic liquid, phosphorylcholine and an imidazolium‐based zwitterionic selector were bonded on the surface of silica to obtain three zwitterionic stationary phases. The selectivity properties were characterized and compared through the relative retention of selected solute pairs, and different kinds of hydrophilic solutes mixtures were used to evaluate the chromatographic performances. Moreover, the zwitterionic stationary phases were further characterized by the modified linear solvation energy relationship model to probe the multiple interactions. All the results indicated that the types and arrangement of charged groups in zwitterionic stationary phases mainly affect the retention and separation of ionic or ionizable compounds, and for interaction characteristics the contribution from n and π electrons and electrostatic interactions displayed certain differences. 相似文献
69.
In this article,we consider the Bagley-Torvik type fractional differential equation ~cD~(ν1) l(t)-a~cD~(ν2) l(t) = g(t, l(t)) and differential inclusion ~cD~(ν1) l(t)-a~cD~(ν2) l(t) ∈ G(t, l(t)),t ∈(0, 1) subjecting to l(0) = l_0,and■ ds where 1 ν_1 ≤ 2, 1 ≤ν_2 ν_1,0 ω≤ 1, χ = ν_1-ν_2 0, a, λ′are given constants. By using Leray-Schauder degree theory and fixed point theorems, we prove the existence of solutions. Our results extend the existence theorems for the classical Bagley-Torvik equation and some related models. 相似文献
70.
催化动力学光度法测定痕量铂的研究 总被引:6,自引:0,他引:6
利用痕量铂在稀硫酸介质中对溴酸钾氧化酸性铬蓝K的催化作用,建立了催化动力学光度法测定痕量铂的新方法。方法的线性范围为0-0.8μg/25mL,检出限为7.93×10^-11g/mL。用于合成样品及含铂催化剂中铂的测定,结果满意。 相似文献