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141.
In situ complexation reactions between 2,6-bis(3,5-dimethylpyrazoyl)pyridine (bdmpp) and some transition metals (Cu2+, Co2+ and Ni2+) were studied with a new method in liquid cell using FT-IR. In this method, the FT-IR spectrum of the solution of ligand was defined as a background, and then the changes in the FT-IR spectra by the addition of the metal salts were investigated. This method allows one to obtain the spectra of the ligand-metal complex before yielding the solid-state product. Complexation ratios (M/L) of these metals with bdmpp were found 1/1, 1/2 and 1/2, for Cu, Co and Ni, respectively. Studying with Mg2+ and Ca2+ ions showed that there were no interaction between bdmpp and these metal ions in methanol. 相似文献
142.
143.
Emanuel Makrlík J. Budka P. Vaňura P. Selucký 《Monatshefte für Chemie / Chemical Monthly》2009,140(2):157-160
Abstract From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium
taking place in the two-phase water–nitrobenzene system (M2+ = Ca2+, Ba2+, Cu2+, Zn2+, Cd2+, Pb2+, UO2
2+, Mn2+, Co2+, Ni2+; 1 = tetraphenyl p-tert-butylcalix[4]arene tetraketone; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants
of the 1 · M2+ complexes in water-saturated nitrobenzene were calculated; they were found to increase in the cation order Ba2+, Mn2+ < Co2+ < Cu2+, Ni2+ < Zn2+, Cd2+, UO2
2+ < Ca2+ < Pb2+.
Graphical abstract
相似文献
144.
In order to develop a receptor molecule for recognizing differences in catechin structures, complexation between catechins and a water-soluble acyclic phane composed of an isophthalate and two aminodisulfonaphthalenes was investigated with 1H NMR spectroscopy. The phane receptor formed 1:1 complexes with the catechins and showed preferential binding ability for the 2,3-trans-gallate-type catechin. The binding studies demonstrated the length of naphthalene framework required to form a hydrophobic environment for the complexation. 相似文献
145.
In recent years, liquid-phase microextraction (LPME), a microscale implementation of liquid-liquid extraction, has become a very popular sample pretreatment technique because it combines extraction and enrichment, and is inexpensive, easy to operate and nearly solvent-free. Especially so in hollow fiber-protected LPME, sample cleanup is also effected. Essentially, owing to its high sample-to-extracting solvent volume ratio, LPME can achieve high analyte enrichment. Since its advent, the technique has been widely used, and applied to environmental, pharmaceutical, biological and forensic analyses. This review focuses on developments relating to chemical reactions associated with LPME applications, in contrast to conventional, straightforward extractions in which analytes remain as they are during the extraction process. Chemical reactions brought about during LPME serve to promote the extractability of the analytes (thus expanding the scope of applicability of the technique), facilitate their (analyte) compatibility with the analytical system and/or improve detection sensitivity. The reactions that are usually enabled during LPME include ion-pair extraction (carrier-mediated membrane transport), complexation, chemical (pre-extraction, in situ, and post-extraction) derivatization, phase-transfer catalysis and other "special affinity" reactions. Strategies on chemical reactions in LPME are overviewed in this report. 相似文献
146.
The complexation of Eu(III), Am(III) and Cm(III) with dicarboxylate anions with O, N or S donor groups was measured in I=6.60 mol⋅kg−1 (NaClO4) at temperatures of 0–60 °C by potentiometry and solvent extraction. The complexation thermodynamics of these complexes show
that their stability is due to highly favorable complexation entropies because the complexation enthalpies are endothermic.
Luminescence studies with Eu(III) and Cm(III) were used to measure the hydration numbers of the complexes. NMR spectra of
1H and 13C were used to determine the binding modes of La(III) with the ligands. The formation of 1:1:1 ternary complexes of M(EDTA)− with the dicarboxylate ligands was studied to determine changes in coordination of the metal cation with formation of the
ternary species. The complexation of ternary complexes changes from bidentate to monodentate as the chain length between the
binding sites of the dicarboxylates increases from 1 (malonate) to 4 (adipate). DFT computations were used to confirm the
structural aspects of the interaction of these complexes. 相似文献
147.
Partially hydrolyzed polyacrylamide (HPAM) has been widely used for water shut-off and profile control to enhance oil recovery. Herein, we reported a novel technique by which the crosslinking between HPAM and Cr3+ in aqueous solutions at 60 ℃ can be delayed effectively. Citric acid was selected as an organic complexing agent of Cr3+ so that the crosslinking between HPAM and Cr3+ can be prevented completely. Due to the decomposition of the bicarbonate (HCO3-) embedded in solution, CO2 released from solution and the pH value of solution increased gradually. The degree of ionization of HPAM and its ability to complex with Cr3+ increased accordingly. When the complexation of Cr3+ with HPAM is stronger than that with citric acid, the viscosity of the HPAM solution increased significantly. Under the closed condition, together with the existence of potassium dihydrogen phosphate (KH2PO4), the release of CO2 was very slow and the condition was highly controlled so that the ionization of HPAM was prevented initially. Furthermore, the hydrogen bonding interactions between HPAM and melamine embedded in solution previously also postponed the ionization of HPAM. As a result, the crosslinking between HPAM and Cr3+ can be delayed for almost one month, completely meeting the requirements for deep water shut-off and profile control to enhance oil recovery. 相似文献
148.
Summary The new Technique of reversed-flow gas chromatography was used to study the possible interactions between the two components of salt-modified adsorbents. The inert volatile solutes weren-hexane and benzene. Partition ratios of these solutes on the modified adsorbents, at various temperatures, were measured, followed by the determination of the differential enthalpies of adsorption. The plots of these enthalpies versus mole fraction of the modifier show a minimum for benzene and a maximum forn-hexane. These are taken as indications of an interaction between the components of the modified adsorbent. 相似文献
149.
The complexation kinetics of the reaction of copper(II) with isomeric tetraamine macrocyclic ligands, C-rac-5, 7, 7, 12, 12, 14-hexamethyl-l, 4, 8, 11-tetraazacyclotetradecane (tet c), C-meso-5, 7, 7, 12, 12, 14-hexamethyl-l, 4, 8, 11-tetraazacyclotetradecane (tet d), and C-meso-5, 5, 7, 12, 12, 14-hexamethyl-1, 4, 8, 11-tetraazacyclotetradecane (tet a) in strongly basic aqueous media have been examined at 25.0 ± 0.1°C by means of the stopped-flow technique. The variation in the values of the resulting rate constants indicates that the positions of the methyl substituents play a significant role in these reactions. These reactions exhibit associative character and second-bond formation is proposed as the rate-determining step. 相似文献
150.
Studies of the complexation of Sn(II) by N,N-dimethylformamide show that Sn(II) ion forms six successive complexes with the ligand. The stability constants were determined by the method of DeFord and Hume. The free energy of transfer of Sn(II) from acetonitrile to N,N-dimethylformamide and to their mixtures was obtained using the theory of Cox et al. The energy decreases with increasing N,N-dimethylformamide concentration, the decrease being most pronounced for nearly pure acetonitrile. 相似文献