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31.
Buglyó P Crans DC Nagy EM Lindo RL Yang L Smee JJ Jin W Chi LH Godzala Iii ME Willsky GR 《Inorganic chemistry》2005,44(15):5416-5427
The aqueous vanadium(III) (V(III)) speciation chemistry of two dipicolinate-type complexes and the insulin-enhancing effects of V-dipicolinate (V-dipic) complexes in three different oxidation states (V(III), V(IV), and V(V)) have been studied in a chronic animal model system. The characterization of the V(III) species was carried out at low ionic strength to reflect physiological conditions and required an evaluation of the hydrolysis of V(III) at 0.20 M KCl. The aqueous V(III)-dipic and V(III)-dipic-OH systems were characterized, and complexes were observed from pH 2 to 7 at 0.2 M KCl. The V(III)-dipic system forms stable 1:2 complexes, whereas the V(III)-dipic-OH system forms stable 1:1 complexes. A comparison of these complexes with the V-pic system demonstrates that a second ligand has lower affinity for the V(III), presumably reflecting bidentate coordination of the second dipic(2)(-) to the V(III). The thermodynamic stability of the [V(III)(dipic)(2)](-) complex was compared to the stability of the corresponding V(IV) and V(V) complexes, and surprisingly, the V(III) complexes were found to be more stable than anticipated. Oral administration of three V-dipicolinate compounds in different oxidation states {H[V(III)(dipic)(2)H(2)O].3H(2)O, [V(IV)Odipic(H(2)O)(2)].2H(2)O, and NH(4)[V(V)O(2)dipic]} and the positive control, VOSO(4), significantly lowered diabetic hyperglycemia in rats with streptozotocin-induced diabetes. The diabetic animals treated with the V(III)- or V(IV)-dipic complexes had blood glucose levels that were statistically different from those of the diabetic group. The animals treated with the V(V)-dipic complex had the lowest blood glucose levels of the treated diabetic animals, which were statistically different from those of the diabetic group at all time points. Among the diabetic animals, complexation to dipic increased the serum levels of V after the administration of the V(V) and V(IV) complexes but not after the administration of the V(III) complex when data are normalized to the ingested dose of V. Because V compounds differing only in oxidation state have different biological properties, it is implied that redox processes must be important factors for the biological action of V compounds. We observe that the V(V)-dipic complex is the most effective insulin-enhancing agent, in contrast to previous studies in which the V(IV)-maltol complex is the most effective. We conclude that the effectiveness of complexed V is both ligand and oxidation state dependent. 相似文献
32.
Chi-Hao Yang-Zhou Jia-Xin Cao Shan-Shan Dong Su-Hua Chen Ruby N. Michael 《Molecules (Basel, Switzerland)》2022,27(1)
The removal of boron (B) from water by co-precipitation with hydroxyapatite (HAP) has been extensively studied due to its low cost, ease of use and high efficiency. However, there is no explicit mechanism to express how resolved B was trapped by HAP. Thus, in this work, the process of removing B from water was studied using a low-cost calcium (Ca) precipitation agent derived from used waste oyster shells. The results showed that the removal rate of B in the simulated wastewater by calcined oyster shell (COS) in the presence of phosphorus (P) is up to more than 90%, as opposed to virtually no removal without phosphate. For B removal, the treated water needs to be an alkaline solution with a high pH above 12, where B is removed as [CaB(OH)4]+ but is not molecular. Finally, the synergistic mechanism of co-precipitation between HAP and dissolved B, occlusion co-precipitation, was explained in detail. The proposed method discovered the relationship between Ca, P and B, and was aimed at removing B without secondary pollution through co-precipitation. 相似文献
33.
Liliany Espitia Ruby Meneses Rosa M. Dominguez Maria Tosta Armando Herize Jesus Lezama Jennifer Lafont Gabriel Chuchani 《国际化学动力学杂志》2009,41(3):145-152
The gas‐phase elimination kinetics of ethyl 2‐furoate and 2‐ethyl 2‐thiophenecarboxylate was carried out in a static reaction system over the temperature range of 623.15–683.15 K (350–410°C) and pressure range of 30–113 Torr. The reactions proved to be homogeneous, unimolecular, and obey a first‐order rate law. The rate coefficients are expressed by the following Arrhenius equations: ethyl 2‐furoate, log k1 (s?1) = (11.51 ± 0.17)–(185.6 ± 2.2) kJ mol?1 (2.303 RT)?1; ethyl 2‐thiophenecarboxylate, log k1 (s?1) = (11.59 ± 0.19)–(183.8 ± 2.4) kJ mol?1 (2.303 RT)?1. The elimination products are ethylene and the corresponding heteroaromatic 2‐carboxylic acid. However, as the reaction temperature increases, the intermediate heteroaromatic carboxylic acid products slowly decarboxylate to give the corresponding heteroaromatic furan and thiophene, respectively. The mechanisms of these reactions are suggested and described. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 145–152, 2009 相似文献
34.
Howard C. Haas Ruby L. MacDonald 《Journal of polymer science. Part A, Polymer chemistry》1973,11(2):327-343
Certain copolymers of maleimide and N-substituted maleimides yield brilliant colors when treated with sufficiently strong basic reagents under nonhydrolytic conditions. For color generation, the copolymer must be capable of HX elimination. The chromophores which account for color probably result from the ionization of acidic protons in structures involving one or more double bonds conjugated with imide carbonyl. The analogy to the color reactions of aconitylanil is pointed out. Spectra covering the range of 330–700 mμ are presented for a number of copolymer–amine color-generating systems. The colors produced in base with radical-initiated polymaleimide and imidazole-initiated poly-N-alkylmaleimides as well as the absence of color with anionic polymaleimide and radical poly-N-alkylmaleimides are discussed in light of what is known about their polymerization kinetics and mechanisms. Corresponding maleic anhydride copolymer systems are mentioned. 相似文献
35.
36.
Andrew M. White Simon J. de Veer Guojie Wu Peta J. Harvey Kuok Yap Gordon J. King Joakim E. Swedberg Conan K. Wang Ruby H. P. Law Thomas Durek David J. Craik 《Angewandte Chemie (International ed. in English)》2020,59(28):11273-11277
Ruthenium‐catalysed azide–alkyne cycloaddition (RuAAC) provides access to 1,5‐disubstituted 1,2,3‐triazole motifs in peptide engineering applications. However, investigation of this motif as a disulfide mimetic in cyclic peptides has been limited, and the structural consequences remain to be studied. We report synthetic strategies to install various triazole linkages into cyclic peptides through backbone cyclisation and RuAAC cross‐linking reactions. These linkages were evaluated in four serine protease inhibitors based on sunflower trypsin inhibitor‐1. NMR and X‐ray crystallography revealed exceptional consensus of bridging distance and backbone conformations (RMSD<0.5 Å) of the triazole linkages compared to the parent disulfide molecules. The triazole‐bridged peptides also displayed superior half‐lives in liver S9 stability assays compared to disulfide‐bridged peptides. This work establishes a foundation for the application of 1,5‐disubstituted 1,2,3‐triazoles as disulfide mimetics. 相似文献
37.
Ruby Upadhyay Mridula Tripathi Priyanka Chawla Ashutosh Pandey 《Journal of Solid State Electrochemistry》2014,18(7):1889-1892
Extracts from roots of Beta vulgaris were used as natural sensitizers of a wide-bandgap semiconductor (CeO2–TiO2) in photoelectrochemical solar cells. The natural dye, adsorbed onto the semiconductor surface, absorbs visible light and promotes electron transfer across the dye/semiconductor interface. We have applied CeO2–TiO2 to natural dye sensitizer solar cells as a photoelectrode to reduce the charge recombination rate by providing energy barrier at the interface between the photoanode and electrolyte which offers an improvement of photovoltaic efficiency. Short-circuit current density (J sc) and open-circuit voltages (V oc) of 9.0 mA cm?2 and 680 mV, respectively, were obtained, and an effective energy conversion efficiency of 3.5?% was achieved. This simple and cheap technique of cell preparation opens up a perspective of commercial feasibility for inexpensive and environment-friendly dye cells. 相似文献
38.
Claudia Loerbroks Jeaphianne van Rijn Marc‐Philipp Ruby Qiong Tong Prof. Dr. Ferdi Schüth Prof. Dr. Walter Thiel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12298-12309
A joint experimental and computational study on the glucose–fructose conversion in water is reported. The reactivity of different metal catalysts (CrCl3, AlCl3, CuCl2, FeCl3, and MgCl2) was analyzed. Experimentally, CrCl3 and AlCl3 achieved the best glucose conversion rates, CuCl2 and FeCl3 were only mediocre catalysts, and MgCl2 was inactive. To explain these differences in reactivity, DFT calculations were performed for various metal complexes. The computed mechanism consists of two proton transfers and a hydrogen‐atom transfer; the latter was the rate‐determining step for all catalysts. The computational results were consistent with the experimental findings and rationalized the observed differences in the behavior of the metal catalysts. To be an efficient catalyst, a metal complex should satisfy the following criteria: moderate Brønsted and Lewis acidity (pKa=4–6), coordination with either water or weaker σ donors, energetically low‐lying unoccupied orbitals, compact transition‐state structures, and the ability for complexation of glucose. Thus, the reactivity of the metal catalysts in water is governed by many factors, not just the Lewis acidity. 相似文献
39.
40.
Christian Ruby Mustapha Abdelmoula Ghouti Medjahdi Michel François 《Journal of solid state chemistry》2008,181(9):2285-2291
The formation and the modifications of the structural properties of an aluminium-substituted iron(II-III)-layered double hydroxide (LDH) of formula (OH)12 SO4, 8H2O are followed by pH titration curves, Mössbauer spectroscopy and high-resolution X-ray powder diffraction using synchrotron radiation. Rietveld refinements allow to build a structural model for hydroxysulphate green rust, GR(SO42−), i.e. y=0, in which a bilayer of sulphate anions points to the Fe3+ species. A cationic order is proposed to occur in both GR(SO42−) and aluminium-substituted hydroxysulphate green rust when y<0.08. Variation of the cell parameters and a sharp decrease in average crystal size and anisotropy are detected for an aluminium content as low as y=0.01. The formation of Al-GR(SO42−) is preceded by the successive precipitation of FeIII and AlIII (oxy)hydroxides. Adsorption of more soluble AlIII species onto the initially formed ferric oxyhydroxide may be responsible for this slowdown of crystal growth. Therefore, the insertion of low aluminium amount (y∼0.01) could be an interesting way for increasing the surface reactivity of iron(II-III) LDH that maintains constant the quantity of the reactive FeII species of the material. 相似文献