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41.
Melek Hajji Hasan Mtiraoui Nesrine Amiri Moncef Msaddek Taha Guerfel 《International journal of quantum chemistry》2019,119(21):e26000
The present work arose out of a desire to fundamentally understand the molecular geometry, weak interactions, electron density delocalization, and chemical reactivity features of 1,5-benzodiazepines-containing family. Herein, a complete X-ray crystallographic study, supported by trustworthy sets of computational approaches, has been reported for two organic crystals. Quantifying intramolecular and intermolecular interactions by Hirshfeld-Becke surfaces analysis conjointly with noncovalent interaction-reduced density gradient topological study revealed that supramolecular assemblies are stabilized by N-H … O (inter) and O-H … N (intra) hydrogen bonds, Cg … Cg (π … π) and C-H(O) … π intercontacts, as well as Van der Waals interactions and steric effects. The long-range-corrected functional wB97XD, which uses Grimme's D2 dispersion model, seems to be just right for our systems. The quantum theory of atoms in molecules analysis confirms that both significant O1-H1…N1 and N2-H2A…O2 H-bonds are weak and electrostatic in nature. Furthermore, global reactivity indices computed via the conceptual density functional theory framework allows these molecules to be classified as moderate electrophiles and marginal nucleophiles. The active sites favorable for nucleophilic/electrophilic attacks were also predicted based on local Parr functions. Finally, a comparative evaluation on the aromaticity character and π-π stacking ability has been done for different (pseudo) rings. 相似文献
42.
43.
A metal-free phthalocyanine and its cobalt(II) and copper(II) phthalocyanate complexes were prepared by cyclotetramerization of 4-(8-quinolinoxy)phthalonitrile. The new compounds were characterized by elemental analyses, 1H-n.m.r., i.r. and u.v.–vis. spectral data. Electrochemical measurements indicated that CoPc had two metal based and two ligand based redox couples, while H2Pc and CuPc showed four ligand based redox couples. For all complexes, linear variation of the peak current of the first reduction peak (I
pc) with scan rate () indicated the adsorption of the complexes to the electrode surface. 相似文献
44.
The sorption of U(VI) by N, N-dibutyl, N'-benzoylthiourea (DBBT) impregnated resin has been studied. DBBT impregnated resin was prepared by direct adsorption of chelating ligand onto macroporous support, Amberlite XAD-16. The adsorption of DBBT on the macroporous support is shown by FTIR spectroscopy to be the result of only weak chelating ligand-support interactions. Parameters such as the pH effect on the sorption of uranium, the sorption capacity of the impregnated resin, the stripping of uranium and the effect of coexisting ions were investigated by batch experiments. The results demonstrated that uranium(VI) ions, at pH 4.5-7 could be sorbed completely using 0.1 g Amberlite XAD-16 resin loaded with DBBT. The sorption capacity of the impregnated resin is 0.90 mmol uranium(VI) g(-1). Quantitative recovery of U(VI) is achieved by stripping with 0.1 M HNO(3). The method was applied to the determination of uranium in synthetic samples. The precision of the method was 2.4 RSD% in a concentration of 1.20 mug ml(-1) for ten replicate analysis. 相似文献
45.
The determination of palladium and platinum in alumina-supported bimetallic Pt-Re, Pd and Pt catalysts at the 0.03 and 0.3% (m/m) levels, respectively, and of rhodium and platinum in platinum sieve catalysts at the 0.04% (m/m) level and in the 4.75–19.75% (m/m) range, respectively, is described. The platinum group metals in fresh or spent catalysts are determined chromatographically using densitometry by forming theirN,N-diethyl-N-benzoylthiourea complexes. The precision of the method, %RSD, is 0.4–3.5, 2.2–6.7, and 4.2–6.0 for Pt, Pd and Rh, respectively. The accuracy was tested using alumina-based and active carbon platinum and palladium standards. The results were also compared with those obtained by FAAS. There was at most 8% difference between the results obtained with these methods, except for one active carbon based Pd standard. 相似文献
46.
Benzoylthiourea immobilized on silica gel was prepared by two-step post-synthesis modification. The capacity of the chelating
silica gel, which was characterized by FTIR, was 3.21 mmol · g−1. The separation and enrichment of uranium(VI) from solutions was investigated. Effective extraction conditions were optimized
in both batch and column methods prior to determination by spectrophotometry using arsenazo(III). The optimum pH range for
quantitative adsorption is 4–7. Quantitative recovery of U(VI) was achieved by stripping with 0.1 mol · L−1 HCl. The sorption capacity of modified silica gel was 0.85 mmol · g−1 uranium(VI). Recovery of U(VI) was 99.1 ± 2.3% with a detection limit of 2 μg · L−1. The preconcentration factor was 250, and the relative standard deviation was 1.53% for a 1 μg · L−1 U(VI) solution. The method was used for the determination of uranium in synthetic samples and a soil sample. 相似文献
47.
Abdullah Menzek Melek Gökmen Karakaya Afşin Ahmet Kaya 《Helvetica chimica acta》2008,91(12):2299-2307
Reductions of compounds whose benzylic positions bear O‐atoms, such as benzyl alcohol, dibenzyl ether, styrene oxide, benzaldehyde, acetophenone, and benzophenone, to the corresponding non‐conjugated dienes were performed by using t‐BuOH, Li, and gaseous NH3 in THF at room temperature. In these reductions, it was observed that the functional groups at benzylic positions were reduced first. 相似文献
48.
Yang Y Wang B Ucisik MN Cui G Fierke CA Merz KM 《Journal of the American Chemical Society》2012,134(2):820-823
Protein farnesyltransferase (FTase) catalyzes farnesylation of a variety of peptide substrates. (3)H α-secondary kinetic isotope effect (α-SKIE) measurements of two peptide substrates, CVIM and CVLS, are significantly different and have been proposed to reflect a rate-limiting S(N)2-like transition state with dissociative characteristics for CVIM, while, due to the absence of an isotope effect, CVLS was proposed to have a rate-limiting peptide conformational change. Potential of mean force quantum mechanical/molecular mechanical studies coupled with umbrella sampling techniques were performed to further probe this mechanistic dichotomy. We observe the experimentally proposed transition state (TS) for CVIM but find that CVLS has a symmetric S(N)2 TS, which is also consistent with the absence of a (3)H α-SKIE. These calculations demonstrate facile substrate-dependent alterations in the transition state structure catalyzed by FTase. 相似文献
49.
We have developed a cloud point extraction procedure based on room temperature ionic liquid for the preconcentration and determination of mercury in water samples. Mercury ion was quantitatively extracted with tetraethyleneglycol-bis(3- methylimidazolium) diiodide in the form of its complex with 5,10,15,20-tetra-(4-phenoxyphenyl)porphyrin. The complex was back extracted from the room temperature ionic liquid phase into an aqueous media prior to its analysis by spectrofluorimetry. An overall preconcentration factor of 45 was accomplished upon preconcentration of a 20?mL sample. The limit of detection obtained under the optimal conditions is 0.08?μg mL?1, and the relative standard deviation for 10 replicate assays (at 0.5?g mL?1 of Hg) was 2.4%. The method was successfully applied to the determination of mercury in tap, river and mineral water samples. Figure
In this work, a novel and sensitive analytical methodology for mercury preconcentration and determination in different water samples using ionic liquid was developed. The use of room temperature ionic liquid‘s biphasic systems as an alternative to conventional solvents offers several advantages including safety and high capacity to extract Hg(II) and other elements with high recoveries. ?onic liquid in combination with porphyrin complexing reagent was successfully applied in this study for the extraction and preconcentration of Hg(II). Likewise, a fast and quantitative back extraction of the analyte from room temperature ionic liquid phase into aqueous phase was possible, allowing its further determination by spectrofluorimetry. The preconcentration method allowed mercury determination in tap, river and mineral water samples at trace levels with high accuracy and reproducibility. 相似文献
50.
Duygu Totur Serap Seyhan Bozkurt Melek Merdivan 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(1):321-327
A sensitive and selective solid phase extraction procedure for the determination of trace of uranium(VI) has been developed.
An alumina-sodium dodecyl sulfate coated on with pyrocatechol violet was used for preconcentration and determination of uranyl
ions by spectrophotometry method using Arsenazo III reagent. Sorbed ions were quantitatively eluted using 5 mL of 0.25 mol L−1 HNO3. The effects of parameters such as pH, amount of alumina, amount of ligand, flow rate, type and concentration of elution
agent were examined. The capacity of the sorbent for U(VI) was found to be 0.92 mmol g−1. The relative standard deviation was 1.28% for 10 replicate determinations of U(VI) ion in a solution with a concentration
of 1.0 μg mL−1. The practical applicability of the developed sorbent was examined using synthetic and real samples such as standard reference
material 2709 (San Joaquin Soil) and 2711 (Montana Soil). 相似文献