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71.
Sandeep P. Netalkar Priya P. Netalkar Anupama A. Nevrekar Vidyanand K. Revankar 《应用有机金属化学》2016,30(4):170-180
The reaction of [PdCl2(CH3CN)2] and N(4)‐substituted phenylaminoacetohydrazone ligands (LH) in methanol at room temperature afforded air‐ and moisture‐stable palladium(II) complexes of two types with general formulae [Pd(LH)Cl] and [Pd2(LH)(L)]Cl. An unusual coordination mode of ligand LH is observed, in which the ligand coordinates through N(4)H nitrogen and without enolization of the carbonyl group of the hydrazone moiety in both mono‐ and bimetallic complexes. The crystal structure of the complexes reveals that the oxime LH reacts with [PdCl2(CH3CN)2] presumably via the elimination of HCl from hydrazine NH. All the synthesized Pd(II) complexes were evaluated as catalysts in the Suzuki cross‐coupling reaction of aryl halides, activated 4‐bromoacetophenone and non‐activated bromobenzene, with phenylboronic acid in aqueous medium. In both cases, i.e. with activated and non‐activated aryl halides, all the complexes show moderate conversion leading to biaryls with yields in the range 50–65%. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
72.
73.
Neetu Tiwari Anupama Asthana Kanchan Upadhyay 《Research on Chemical Intermediates》2013,39(6):2867-2879
A sensitive analytical procedure based on solid phase extractive-spectrophotometry has been established for the determination of the widely used herbicide atrazine .The method is based on the Konig reaction in which atrazine reacts with pyridine reagent to form a quaternary pyridinium halide, which further forms glutaconic aldehyde in the presence of alkali. Glutaconic aldehyde is subsequently coupled with 4-aminoacetanilide in the micellar medium of anionic surfactant sodium dodecyl sulphate to give a yellow-orange dye. The produced dye was enriched on a C18 cartridge and is measured spectrophotometrically at 460 nm. The sensitivity and selectivity of the method was largely enhanced in the micellar media and SPE on the C18 cartridge and avoids the use of toxic solvents. Beer’s law was obeyed in the range 0.012–0.12 μg mL?1. Molar absorptivity and Sandell’s sensitivity were found to be 1.52 × 106 L mol? 1 cm?1 and 0.0002 μg cm?2, respectively. The limit of detection and quantification were 0.001 and 0.003 μg mL?1, respectively. The proposed method was applied successfully for the determination of atrazine in environmental and biological samples with a recovery range of 96–101 %. The method was found to be free from interference of a large number of foreign species. The accuracy and reliability of the method was further established by parallel determination by the reference method, and by recovery studies. 相似文献
74.
Kanchan Upadhyay Anupama Asthana Neetu Tiwari Snitha B. Mathew 《Research on Chemical Intermediates》2013,39(8):3553-3563
A simple and sensitive spectrophotometric method for the determination of nimesulide in bulk, in pharmaceutical dosage form, and in biological fluids was developed. The method is based on the reduction of the nitro group of nimesulide by zinc and hydrochloric acid followed by diazotization, and coupling with orcinol in basic medium to form a stable chromophore, which absorbs at 465 nm. The method showed a good linearity in the range 0.4–4.0 μg mL?1. Partial least square modeling as a powerful multivariate statistical tool is also applied, compiled, and compared for determination of nimesulide. The experimental matrix for the partial least square calibration method was designed with 24 samples. The cross-validation was used for selecting the number of factors. The root mean square error prediction (RMSEP) and the relative error of prediction (REP %) were 0.089 and 3.95, respectively. The developed method is free from the interference of common excipients used in pharmaceutical dosages. The method was also used for the determination of nimesulide in pharmaceutical dosages as well as in human serum and urine samples. 相似文献
75.
Adsorption of Fe(ClO4)3(H2O)6 onto chromatographic grade silica gel in the presence of alcohol (to be used for esterification) produces a supported reagent, Fe(ClO4)3(ROH)6/SiO2. This reagent, has been found effective for the rapid and high yield of esters, on grinding in the presence of carboxylic acids using pestle and mortar in the solid state. 相似文献
76.
Two chromogenic complexes, L.Zn (where L is (E)-4-((4-(1,4,8,11-tetraazacyclotetradecan-1-ylsulfonyl)phenyl)diazenyl)-N,N-dimethylaniline) and its [2]pseudorotaxane form (α-CD.L.Zn), were found to bind preferentially to adenosine triphosphate (ATP), among all other common anions and biologically important phosphate (AMP, ADP, pyrophosphate, and phosphate) ions in aqueous HEPES buffer medium of pH 7.2. Studies with live cell cultures of prokaryotic microbes revealed that binding of these two reagents to intercellular ATP, produced in situ, could be used in delineating the gram-positive and the gram-negative bacteria. More importantly, these dyes were found to be nontoxic to living microbes (eukaryotes and prokaryotes) and could be used for studying the cell growth dynamics. Binding to these two viable staining agents to intercellular ATP was also confirmed by spectroscopic studies on cell growth in the presence of different respiratory inhibitors that influence the intercellular ATP generation. 相似文献
77.
An experimental charge density study has been carried out on perylene based on X-ray diffraction measurements at 130 K. The
electron density and its associated properties have been evaluated at the bond and the ring critical points for the naphthalene
residues as well as for the central ring. The variation of the Laplacian along the axis, above and below the ring plane, is
found to be symmetric for the central ring while for the naphthalene rings, the Laplacian values are enhanced under the bow-shaped
region. A plot of the Laplacian versus density evaluated at various points along the axis above the ring plane, shows a steep
variation in the case of the central ring implying that theπ-density is smeared out compared to that over the naphthalene rings. Similar data extracted from a quinoid ring and a regular
phenyl ring (both based on earlier reports from this laboratory) exhibit increasingly shallower trends and indicate, by contrast,
that the central ring of perylene is much less aromatic.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
78.
Benjamin M. Brandsen Tania E. Velez Dr. Amit Sachdeva Nora A. Ibrahim Prof. Scott K. Silverman 《Angewandte Chemie (International ed. in English)》2014,53(34):9045-9050
Catalyzing the covalent modification of aliphatic amino groups, such as the lysine (Lys) side chain, by nucleic acids has been challenging to achieve. Such catalysis will be valuable, for example, for the practical preparation of Lys‐modified proteins. We previously reported the DNA‐catalyzed modification of the tyrosine and serine hydroxy side chains, but Lys modification has been elusive. Herein, we show that increasing the reactivity of the electrophilic reaction partner by using 5′‐phosphorimidazolide (5′‐Imp) rather than 5′‐triphosphate (5′‐ppp) enables the DNA‐catalyzed modification of Lys in a DNA‐anchored peptide substrate. The DNA‐catalyzed reaction of Lys with 5′‐Imp is observed in an architecture in which the nucleophile and electrophile are not preorganized. In contrast, previous efforts showed that catalysis was not observed when Lys and 5′‐ppp were used in a preorganized arrangement. Therefore, substrate reactivity is more important than preorganization in this context. These findings will assist ongoing efforts to identify DNA catalysts for reactions of protein substrates at lysine side chains. 相似文献
79.
Dr. Gangavaram V. M. Sharma Thota Anupama Yadav Kanakaraju Marumudi Prashanth Thodupunuri Pothula Purushotham Reddy Dr. Ajit C. Kunwar 《化学:亚洲杂志》2014,9(11):3153-3162
A new three‐residue turn in β peptides nucleated by a 12/10‐mixed helix is presented. In this design, β peptides were derived from the 1:1 alternation of C‐linked carbo‐β‐amino acid ester [BocNH‐(R)‐β‐Caa(r)‐OMe] (Boc=tert‐butyloxycarbonyl), which consisted of a D ‐ribo furanoside side chain, and β‐hGly residues. The hexapeptide with (R)‐β‐Caa(r) at the N terminus showed the ‘turn’ stabilized by a 14‐membered NH(4) ??? CO(6) hydrogen bond at the C terminus nucleated by a robust 12/10‐mixed helix, thus providing a ‘helix‐turn’ (HT) motif. The turn and the helix were additionally stabilized by intraresidue electrostatic interaction between the furan oxygen in the carbohydrate side chain and NH in the backbone. However, the hexapeptide with a β‐hGly residue at the N terminus demonstrated the presence of a 10/12 helix through its entire length, which again showed the intraresidue interaction between NH and furan oxygen. The intraresidue NH ??? O? Me electrostatic interactions observed in the monomer, however, were absent in the peptides. 相似文献
80.
Copper perchlorate is found to be a heterogeneous catalyst for an efficient and greener synthesis of 4-substituted 2H-chromen-2-ones via von Pechmann condensation of substituted phenols and β-keto esters in solventless media with excellent yields using ultrasound irradiation. The present methodology offers several advantages such as excellent yields, simple procedure and milder conditions. 相似文献