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排序方式: 共有91条查询结果,搜索用时 171 毫秒
31.
32.
Fahmy AS El-Beih FM Mohamed SA Abdel-Gany SS Abd-Elbaky EA 《Applied biochemistry and biotechnology》2008,149(3):205-217
Polygalacturonase (PGI) from Aspergillus niger NRRL3 was purified about 12.0-fold from the cell-free broth using diethylaminoethyl-Sepharose and Sephacryl S-200 columns. The molecular weight of the PGI was 32,000 Da as estimated by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. PGI had an isoelectric point of 7.6 and an optimum pH of 5.0. PGI was active on polygalacturonic acid and esterified pectins, but the activity on pectin decreased with an increase in degree of esterification. PGI had higher affinity (low Km) and turnover number (Vmax/Km and Kcat/Km) toward polygalacturonic acid. PGI was found to have a temperature optimum at 40 degrees C and was approximately stable up to 30 degrees C. All the examined metal cations had partial inhibitory effects on PGI, while Mn+2 at 5 mM caused a complete inhibition for the enzyme. Comparison of viscosity reduction rates with release of reducing sugars indicated that the enzyme from A. niger is exoacting. The storage stability study of PGI showed that the enzyme in powder form retained 56% of its activity after 9 months of storage at 4 degrees C. The above properties of PGI may be suitable for food processing. 相似文献
33.
34.
Saeed Ul Haq Raz Muhammad Afaf Khadr Alqorashi Muhammad Shafiullah Amir Sohail Amel Laref Muhammad Faizan 《International journal of quantum chemistry》2024,124(3):e27353
We investigated the magnetic and thermoelectric properties of REMoN3 (RE = La, Ce, Pr, Nd, Sm) perovskites using the full potential linearized augmented plane wave (FP-LAPW) method. To overcome the problem of underestimation of electronic interaction, we employed the DFT + U approach to accurately map the electronic structure of these compounds. Our study shows an increasing trend in the magnetic moments with the increasing number of unpaired electrons in RE. Among these compounds, SmMoN3 possesses a large magnetic moment, which is suitable for applications such as memory devices and sensors. Interestingly, all these perovskites display ferromagnetic behavior except CeMoN3, which exhibits an antiferromagnetic nature. Furthermore, our analysis indicates n-type thermoelectric behavior in all these materials. The compound, namely PrMoN3, exhibits a high figure of merit among REMoN3, which can be improved by modifying the lattice sites. 相似文献
35.
The hypoglycemic and antioxidants activities of the methanol extract of Lepidium sativum seeds was tested in alloxan-induced diabetic male rats. Thirty male albino rats weighing 190–200 g were divided into five groups as follows: negative control, positive control and three diabetic groups treated with three concentrations of L. sativum methanol extract for four weeks. Induction of hyperglycemia in the positive control group increased blood glucose, glycated hemoglobin A1c, immunoglobulins, liver enzyme, lipid peroxide and kidney function, total cholesterol, low-density lipoproteins, very low-density lipoproteins and decreased antioxidants and high-density lipoproteins compared with the negative control. Furthermore, pancreas tissues showed pathological changes compared with the negative control. Treating the diabetic rats with L. sativum methanol extract decreased blood sugar and restored all biochemical and histological changes to the normal. It could be concluded that L. sativum methanol extract succeeded in controlling diabetes, increasing antioxidants and ameliorating lipid profile. 相似文献
36.
Feng Jiang Douglas I. Trupp Norah Algethami Haining Zheng Wenxiang He Afaf Alqorashi Chenxu Zhu Chun Tang Ruihao Li Junyang Liu Hatef Sadeghi Jia Shi Ross Davidson Marcus Korb Alexandre N. Sobolev Masnun Naher Sara Sangtarash Paul J. Low Wenjing Hong Colin J. Lambert 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(52):19163-19169
Together with the more intuitive and commonly recognized conductance mechanisms of charge‐hopping and tunneling, quantum‐interference (QI) phenomena have been identified as important factors affecting charge transport through molecules. Consequently, establishing simple and flexible molecular‐design strategies to understand, control, and exploit QI in molecular junctions poses an exciting challenge. Here we demonstrate that destructive quantum interference (DQI) in meta‐substituted phenylene ethylene‐type oligomers (m‐OPE) can be tuned by changing the position and conformation of methoxy (OMe) substituents at the central phenylene ring. These substituents play the role of molecular‐scale taps, which can be switched on or off to control the current flow through a molecule. Our experimental results conclusively verify recently postulated magic‐ratio and orbital‐product rules, and highlight a novel chemical design strategy for tuning and gating DQI features to create single‐molecule devices with desirable electronic functions. 相似文献
37.
Afaf R. Genady Mohamed E. El-Zaria Detlef Gabel 《Central European Journal of Chemistry》2008,6(2):154-160
Derivatives of purine, adenine, guanine, and 2,6-diaminopurine linked to the azanonaborane (B8N cluster) have been prepared, for possible use as powerful agents for boron neutron capture therapy (BNCT). The synthesis
was carried out via a ligand exchange reaction. The exo-NH2R group of the azanonaborane of the type [(RH2N)B8H11NHR] can be exchanged by one hetero-nitrogen atom of the pyrimidine ring, and except for guanine, also by an N atom of the
imidazole ring. The identity of the products was confirmed by NMR, elemental analysis, IR, and mass spectrometry. No reaction
was found to occur with caffeine and theophylline under the same reaction conditions.
相似文献
38.
Mohamed SA El-Badry MO Drees EA Fahmy AS 《Applied biochemistry and biotechnology》2008,150(2):127-137
The major pool of peroxidase activity is present in the peel of some Egyptian citrus species and cultivars compared to the juice and pulp. Citrus jambhiri cv. Adalia had the highest peroxidase activity among the examined species. Four anionic and one cationic peroxidase isoenzymes from C. jambhiri were detected using the purification procedure including ammonium sulfate precipitation, chromatography on diethylaminoethanol-cellulose, carboxymethyl-cellulose, and Sephacryl S-200 columns. Cationic peroxidase POII is proved to be pure, and its molecular weight was 56 kDa. A study of substrate specificity identified the physiological role of POII, which catalyzed the oxidation of some phenolic substrates in the order of o-phenylenediamine > guaiacol > o-dianisidine > pyrogallol > catechol. The kinetic parameters (K (m), V (max), and V (max)/K (m)) of POII for hydrolysis toward H2O2 and electron donor substrates were studied. The enzyme had pH and temperature optima at 5.5 and 40 degrees C, respectively. POII was stable at 10-40 degrees C and unstable above 50 degrees C. The thermal inactivation profile of POII is biphasic and characterized by a rapid decline in activity on exposure to heat. The most of POII activity (70-80%) was lost at 50, 60, and 70 degrees C after 15, 10, and 5 min of incubation, respectively. Most of the examined metal ions had a very slight effect on POII except of Li+, Zn2+, and Hg2+, which had partial inhibitory effects. In the present study, the instability of peroxidase above 50 degrees C makes the high temperature short time treatment very efficient for the inactivation of peel peroxidase contaminated in orange juice to avoid the formation of off-flavors. 相似文献
39.
Two aza-analogues of distyrylbenzene namely: 1,4-bis[β-(4-quinolyl)vinyl]benzene (PhQ) and 1,4-bis[β-(4-pyridyl)vinyl]benzene (PhPy) containing arachno-decaborane or arachno-nonaborane clusters have been isolated: 6,9-(PhQ)2-arachno-B10H12 (1), N,N′-bis[9-Me2S-arachno-B10H12-6-yl]PhQ (2), 6,9-(PhPy)2-arachno-B10H12 (3), N,N′-bis[(9-Me2S)-arachno-B10H12-6-yl]PhPy (4), N,N′-bis[arachno-B9H13-4-yl]PhQ (5), 4-PhQ-arachno-B9H13 (6), N,N′-bis[arachno-B9H13-4-yl]PhPy (7), and 4-PhPy-arachno-B9H13 (8). These boronated compounds were easily prepared from the displacement reactions of weaker ligand (SMe2) of bis (dimethyl sulfide) arachno-decaborane(14) {6,9-(Me)2SB10H12}or dimethyl sulfide-arachno-nonaborane {4-(Me)2SB9H13} by the stronger bidentate ligands of PhQ or PhPy in ratio (1:2). The electronic interaction between decaborane or nonaborane arachno-type unit and the bonded pyridine units has been investigated by UV-Vis spectroscopy and by AM1 molecular orbital calculations. The resulting compounds undergo trans-cis photoisomerization upon excitation. The connection of boron clusters to PhQ and PhPy led to enhancing of the photoreactivity and decreasing of the fluorescence quantum yield of the products. 相似文献
40.
Dealing with the shifted and inverted Tietz–Hua oscillator potential using the J‐matrix method
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Mohamed S. Abdelmonem Afaf Abdel‐Hady Ibraheem Nasser 《International journal of quantum chemistry》2016,116(12):897-907
The tridiagonal J‐matrix approach has been used to calculate the low and moderately high‐lying eigenvalues of the rotating shifted Tietz–Hua (RSTH) oscillator potential. The radial Schrödinger equation is solved efficiently by means of the diagonalization of the full Hamiltonian matrix, with the Laguerre or oscillator basis. Ro–vibrational bound state energies for 11 diatomic systems, namely , , , NO, CO, , , , , , and NO+, are calculated with high accuracy. Some of the energy states for molecules are reported here for the first time. The results of the last four molecules have been introduced for the first time using the oscillator basis. Higher accuracy is achieved by calculating the energy corresponding to the poles of the S‐matrix in the complex energy plane using the J‐matrix method. Furthermore, the bound states and the resonance energies for the newly proposed inverted Tietz–Hua IRSTH‐potential are calculated for the H2‐molecule with scaled depth. A detailed analysis of variation of eigenvalues with n, quantum numbers is made. Results are compared with literature data, wherever possible. © 2015 Wiley Periodicals, Inc. 相似文献