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排序方式: 共有96条查询结果,搜索用时 31 毫秒
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SOLIMAN A.Y. BAKEER H.M. ATTIA LA.Science Department Faculty of Teachers P.O.Box Alhasa Saudi Arabia Chemistry Department Faculty of Science Fayoum Cairo University EgyptFaculty of Engineering Ain Shames University Egypt 《中国化学》1996,14(6):532-540
3-(4-Phenyl) benzoyl propionic acid was used as the starting material for the synthesisof furanones (2), pyrrolinones (5), pyridazinones (7), benzoxazinones (8) and quinazolinones (9-11). The behaviour of the derivatives of furanones and benzoxazinones toward different nucleophiles is reported. 相似文献
3.
Gilberto Schiavon Gianni Zotti Gino Bontempelli 《Journal of Electroanalytical Chemistry》1984,161(2):323-335
The electrochemical reduction of [Ni(PPh3)2(p-C6H4Br)Br] in acetonitrile results in a polymeric coating of a nickel-containing poly-p-phenylene, formulated as [-Ni(p-C6H4)n-] (n=6?7) on the basis of elemental analysis, IR, UV, MS and ESCA measurements. This coating is found to undergo a two-electron reversible reduction and a one-electron reversible oxidation with a large potential window (3.6 V), without the polymeric film being destroyed. Moreover, the polymer obtained is shown to be electroactive towards dissolved reactants via permeation or mediated electron transfer, depending on the molecular size of the electroactive species employed. 相似文献
4.
Gianni Zotti Giuseppe Pilloni Mario Bressan Mario Martelli 《Journal of Electroanalytical Chemistry》1977,75(2):607-612
The electrochemical reduction of chlorodi-(1,3-bisdiphenylphosphinopropane)ruthenium(II)hexafluorophosphate, [RuCl(DPP)2](PF6), has been studied on the mercury electrode in 1,2-dimethoxyethane +0.1 M TBAP. The polarogram shows two reversible one-electron waves corresponding to the formation of [RuCl(DPP)2] and [RuCl(DPP)2]. Both products are unstable and decay through a disproportionation pathway and a fast internal metalation via Cl? elimination with formation of HRu(C6H4PPh·CH2CH2 CH2·PPh2)(DPP), respectively. The hypothesis is put forward that the geometry of a metal-complex can be one of the factors which allow us to obtain d7 monomeric complexes by electrochemical methods. 相似文献
5.
MENG Jian REN Yu-Fang LI Xiao-GuangLaboratory of Rare Earth Chemistry Physics Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin ChinaPopov V.V. Repin S.M. Smirnov LA. loffe Physicotechnical Institute Russian Academy of Sciences Saint Petersburg Russia 《中国化学》1994,12(5):419-424
YBa2Cu3-xVxO7-y(x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) superconductors have been prepared. X-ray diffraction shows that the system remains orthorhombic for all compositions studied, but for x > 0.4 V2O5 was detected as an impurity phase. Substitution of V5+ for Cu2+ occurs in the Cu(2) sites on the Cu(2)-O planes. The introduction of the high valence element, vanadium, produces the extra free-electrons. These electrons recombine with the positive carrier of the system. It makes depression of the mobility and the Hall number of YBa2Cu3-xVxO7-v and also results in a depression of TC. 相似文献
6.
Gianni Zotti Sandro Zecchin Giuseppe Pilloni 《Journal of organometallic chemistry》1979,181(2):375-386
The new iron compound, trans-[Fe(DPE)2(MeCN)2] (ClO4)2 (DPE=PPh2CH2CH2PPh2), has been prepared and investigated electrochemically. In acetonitrile the complex shows two reduction steps, consistent with the formation of the stable iron(I) species, [Fe(DPE)2(MeCN)]+ and the rather labile π-bonded acetonitrile adduct, Fe(DPE)2(π-MeCN), respectively. Acetonitrile substitution by carbon monoxide leads to formation of the carbonylated species, which have been characterized, and examined by electrochemical techniques. A significant feature is that trans-[Fe(CO)2(DPE)2]2+, unlike trans-[Fe(DPE)2(MeCN)2]2+, takes up two electrons in a single process, the unstable d7 intermediate undergoing a fast disproportionation. A tentative interpretation of this behaviour is suggested. 相似文献
7.
MARIAN ELBANOWSKI MARIA PAETZ JANUSZ SIAWINSKI LESZEK CIELA 《Photochemistry and photobiology》1988,47(3):463-466
Abstract— Chemiluminescence of the Eu(II)/Eu(III)-adenine nucleotide-H2 O2 system and fluorescence of the Eu(III)-adenosine triphosphate system have been investigated. The spectral distribution of the chemiluminescence emission has shown an occurrence of three main bands (Λ=470–480,590–620 and ca. 700 nm). The energy transfer process from the adenosine triphosphate molecules to the Eu(III) ions has been observed in the fluorescence spectrum. The examined chemiluminescence and fluorescence spectra show that these both kinds of emission originate from the 5 D *** τ7 F*** ( n =1–4) transitions in the Eu(III) ions. 相似文献
8.
Sascha Kubitzky Prof. Mariano Venanzi Dr. Barbara Biondi Dr. Raffaella Lettieri Dr. Marta De Zotti Dr. Emanuela Gatto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(8):2810-2817
External stimuli are potent tools that Nature uses to control protein function and activity. For instance, during viral entry and exit, pH variations are known to trigger large protein conformational changes. In Nature, also the electron transfer (ET) properties of ET proteins are influenced by pH-induced conformational changes. In this work, a pH-controlled, reversible 310-helix to α-helix conversion (from acidic to highly basic pH values and vice versa) of a peptide supramolecular system built on a gold surface is described. The effect of pH on the ability of the peptide SAM to generate a photocurrent was investigated, with particular focus on the effect of the pH-induced conformational change on photocurrent efficiency. The films were characterized by electrochemical and spectroscopic techniques, and were found to be very stable over time, also in contact with a solution. They were also able to generate current under illumination, with an efficiency that is the highest recorded so far with biomolecular systems. 相似文献
9.
A. D. Milov Y. D. Tsvetkov M. De Zotti C. Prinzivalli B. Biondi F. Formaggio C. Toniolo M. Gobbo 《Journal of Structural Chemistry》2013,54(1):73-85
The X band PELDOR spectroscopy was used to investigate the magnetic dipole-dipole interactions in glassy solutions of nitroxide mono-labeled tylopeptin B and heptaibin peptaibiotics at 77 K. Specifically, a study was performed of the tylopeptin B peptides labeled at either position 3, 8, or 13, denoted as T3, T8, and T13, respectively. The heptaibin analogs labeled at either position 2 or 14, denoted as H2 and H14, respectively, were also investigated. It was shown that in frozen glassy peptide solutions in methanol, the spin labels are randomly distributed over the solvent volume. This result points to the absence of specific dipolar interactions between the peptides under these conditions. However, peptide aggregation was detected in weakly polar methanol/toluene environments. To study the properties of the resulting aggregates, we examined the depth of modulation for the PELDOR traces as a function of the concentration of the peptides in solution and the distances between the spin labels in the aggregates. Based on the concentration dependencies, the number of peptide molecules in the aggregates was estimated. We find that this value ranges from 2 to 3, depending on the position of the spin label in the peptide sequence. The combined analysis of the distance spectra and the number of peptide molecules in the aggregates allows us to suggest that dimer formation is the prevailing mode of self-association. In the case of spin-labeled tylopeptin B, the molecules in the dimer are head-to-head oriented. In addition, the distance spectra of the aggregates show that the C-termini of the molecules in the tylopeptin B dimer are more mobile than the Ntermini. This phenomenon leads to an increase in the spread of the distances between the nitroxides as the label position is approaching the peptide C-terminus. For heptaibin, we show that two forms of dimerization (head-to-head and head-to-tail) occur. Finally, in addition to dimers, aggregates containing 3 or 4 peptide molecules, which give broad lines in the distance spectra, are seen in solution. 相似文献
10.
针对纤维材料变温环境力学性能测试的需要,在华中科技大学研制的纤维材料试验机的基础上引入了温控装置,从而实现纤维材料在高低温环境下的力学性能测试。采用该装置对不同直径微米铜丝在不同温度、不同拉伸速率条件下的力学性能开展实验研究,测试结果表明弹性模量和抗拉强度随温度的降低而线性增加,屈服强度的变化不太明显。另外,低温环境下微米铜丝的力学性能表现出与其直径相关的尺度效应,而这一现象在常温下一直没有观测到。最后,还研究了拉伸速率对微米铜丝的力学性能影响,结果表明,在现有装置的许用范围之内,拉伸速率对其力学性能的影响不大。 相似文献