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51.
Leonardo C. Ferreira Carlos A. L. Filgueiras Lorenzo C. Visentin Jairo Bordinho Manfredo Hrner 《无机化学与普通化学杂志》2008,634(11):1896-1900
The preparation and characterization of two novel HgCl2 and Hg(SCN)2 complexes with bis[N‐(2‐tert‐butylphenyl)imine]acenaphthene is here described. One‐pot reaction techniques were used, leading to high yields of 75 % and 81 %, respectively. The complexes were characterized by microanalysis, i.r. and 1HNMR spectroscopy, and by single crystal X‐ray diffraction. The structures of the complexes present similar characteristics, the most outstanding being the formation of dimers via intermolecular interaction. Whereas the HgCl2 complex shows a unidimensional network due to strong π–π interactions, its Hg(SCN)2 counterpart displays a supramolecular arrangement resulting from non classical hydrogen bond formation. 相似文献
52.
Elena E. Stashenko Jairo R. Martínez Carlos A. Ruíz Ginna Arias Camilo Durán William Salgar Mónica Cala 《Journal of separation science》2010,33(1):93-103
Chromatographic (GC/flame ionization detection, GC/MS) and statistical analyses were applied to the study of essential oils and extracts obtained from flowers, leaves, and stems of Lippia origanoides plants, growing wild in different Colombian regions. Retention indices, mass spectra, and standard substances were used in the identification of 139 substances detected in these essential oils and extracts. Principal component analysis allowed L. origanoides classification into three chemotypes, characterized according to their essential oil major components. α‐ and β‐phellandrenes, p‐cymene, and limonene distinguished chemotype A; carvacrol and thymol were the distinctive major components of chemotypes B and C, respectively. Pinocembrin (5,7‐dihydroxyflavanone) was found in L. origanoides chemotype A supercritical fluid (CO2) extract at a concentration of 0.83±0.03 mg/g of dry plant material, which makes this plant an interesting source of an important bioactive flavanone with diverse potential applications in cosmetic, food, and pharmaceutical products. 相似文献
53.
Mašek J Máca F Kudrnovský J Makarovsky O Eaves L Campion RP Edmonds KW Rushforth AW Foxon CT Gallagher BL Novák V Sinova J Jungwirth T 《Physical review letters》2010,105(22):227202
We analyze microscopically the valence and impurity band models of ferromagnetic (Ga,Mn)As. We find that the tight-binding Anderson approach with conventional parametrization and the full potential local-density approximation+U calculations give a very similar band structure whose microscopic spectral character is consistent with the physical premise of the k·p kinetic-exchange model. On the other hand, the various models with a band structure comprising an impurity band detached from the valence band assume mutually incompatible microscopic spectral character. By adapting the tight-binding Anderson calculations individually to each of the impurity band pictures in the single Mn impurity limit and then by exploring the entire doping range, we find that a detached impurity band does not persist in any of these models in ferromagnetic (Ga,Mn)As. 相似文献
54.
55.
Gabriel Chuchani Rosa M. Dominguez Alexandra Rotinov Jairo Quijano Cristina Valencia Bernardo Vicente Dimas Franco 《Journal of Physical Organic Chemistry》1999,12(1):19-23
The gas‐phase elimination kinetics of primary, secondary and tertiary β‐hydroxynitriles were examined in static seasoned vessels over the temperature range 360–450 °C and pressure range 47–167 Torr (1 Torr = 133.3 Pa). These reactions are homogeneous, unimolecular and follow a first‐order rate law. The rate coefficients are given by the Arrhenius equation: for 3‐hydroxypropionitrile log k1 = (14.29 ± 0.47) − (234.9 ± 6.3) kJ mol−1 (2.303 RT)−1; for 3‐hydroxybutyronitrile log k1 = (13.76 ± 0.10) − (222.6 ± 0.7) kJ mol−1 (2.303RT)−1; and for 3‐hydroxy‐3‐methylbutyronitrile log k1 (s−1) = (13.68 ± 0.68) − (212.5 ± 8.7) kJ mol−1 (2.303RT)−1. The decomposition rates of the β‐hydroxynitriles increase from primary to tertiary carbon containing the OH group. The rates for the β‐hydroxynitriles are found to be slower than those for the corresponding β‐hydroxyacetylene analogs. The value of log A from 13.7 to 14.4 and the small positive ΔS ≠ indicate a mechanism different from a six‐centered cyclic transition state. These data appear to indicate that a four‐membered cyclic transition state or a quasi‐heterolytic mechanism is conceivable. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
56.
William Lpez Prez Jairo Arbey Rodríguez M. Rafael Gonzlez Fabio Fajardo Luis Mancera 《physica status solidi b》2009,246(3):594-598
We have applied the full potential linearized augmented plane wave method (FP‐LAPW) within the density functional theory to investigate the structural and electronic properties of the Sc0.5In0.5N compound in the wurtzite and sodium chloride structures. We have analyzed the relative stability of this ternary compound in the two studied phases. We found that the wurtzite structure is the most stable phase, with the minimum ∼0.14 eV/(unit cell) lower than in the sodium chloride phase. A phase transition from wurtzite to sodium chloride structure was observed, with transition pressure ∼1.9 GPa. Our results predict a direct semiconductor in wurtzite structure and an indirect semiconductor in sodium chloride phase. We investigate the pressure effect on the electronic properties of this ternary compound in the two phases studied. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
57.
Ederley Vélez Jairo Quijano Rafael Notario Elizabeth Pabón Juliana Murillo Julieth Leal Edilma Zapata Gustavo Alarcón 《Journal of Physical Organic Chemistry》2009,22(10):971-977
This paper reports a theoretical study, at the B3LYP/6–31 + G(d,p) and M05‐2X/6–31G + (d,p) levels, on the thermal decomposition of menthyl benzoate (2‐isopropyl‐5‐methylcyclohexyl benzoate). It undergoes a unimolecular first‐order elimination to give 3‐menthene (1‐isopropyl‐4‐methylcyclohexene), 2‐menthene (3‐isopropyl‐6‐methylcyclohexene), and benzoic acid. We studied two possible mechanisms trying to explain the formation of 2‐ and 3‐menthene, via six‐membered or four‐membered cyclic transition states. Rate constants were calculated at two temperatures, 587.1 and 598.6 K, and they agree well with the experimentally determined values. We verify that 3‐menthene is the product mainly formed at both temperatures. The progress of the reactions has been followed by means of the Wiberg bond indices. Intrinsic reaction coordinate (IRC) calculations have been carried out to verify that the localized transition state structures connect with the reactants and products and also to verify that the parent compound, menthyl benzoate, is taking the cis‐configuration needed in the reaction. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
58.
Jairo Quiroga Mario Alvarado Braulio Insuasty Manuel Nogueras Adolfo Snchez M. Dolores Lpez 《Journal of heterocyclic chemistry》1999,36(1):113-115
The title compounds 4 and 5 have been prepared in one-step reaction from 6-amino-4-pyrimidinones 1 , the corresponding 4-substituted benzaldehyde 2 and ethyl cyanoacetate 3 in very good yields. The structure of the final compounds was determined on the basis of nmr measurements, especially by 1H, 1H-, 1H,13C COSY, and DEPT. 相似文献
59.
Gustavo Snchez-Duque Juan Jos Lozada-Castro Emerson Luis Yoshio Hara Marco Tadeu Grassi Milton Rosero-Moreano Jhon Jairo Ríos-Acevedo 《Molecules (Basel, Switzerland)》2022,27(24)
A new sorbent material based on modified clay with ionic liquid immobilized into an agarose film was developed as part of this study. It was applied to determine organochlorine pollutants, like disinfection byproducts, through headspace solid-phase microextraction-gas chromatography-electron capture detection (HS-SPME-GC-ECD). The disinfection byproducts determined in this study were used as model molecules because they were volatile compounds, with proven severe effects on human health. Their presence in aquatic environments is in trace concentrations (from pg L−1 to mg L−1). They are classified as emergent pollutants and their determination is a challenge for analytical chemists. The parameters which affected the extraction efficiency, i.e., number and distance between SPME discs, salt concentration, the temperature of extraction, extraction time, and desorption time, were optimized. A wide linear dynamic range of 10–1000 ng mL−1 and coefficients of determination better than 0.997 were achieved. The limits of detection and the limits of quantitation were found in the ranges of (1.7–3.7) ng mL−1 and (5.6–9.9) ng mL−1, respectively. The precision, expressed as relative standard deviation (RSD), was better than 8%. The developed sorbent exhibits good adsorption affinity. The applicability of the proposed methodology for the analysis of trihalomethanes in environmental and water samples showed recoveries in the range of 86–95%. Finally, the newly created method fully complied with the principles of green chemistry. Due to the fact that the sorbent holder was made of agarose, which is a wholly biodegradable material, sorbent clay is a widespread material in nature. Moreover, the reagents intercalated into the montmorillonite are new green solvents, and during the whole procedure, low amounts of organic solvents were used. 相似文献
60.
Synthesis and Structure Elucidation of New Regioisomeric 2‐Alkylamino‐6‐aryl‐8,9‐dihydropyrimido[4,5‐b][1,4]diazepin‐4(7H)‐ones 
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下载免费PDF全文 Braulio Insuasty Fabián Orozco Jairo Quiroga Rodrigo Abonía Manuel Nogueras Justo Cobo 《Journal of heterocyclic chemistry》2014,51(1):196-202
Novel 2‐Alkylamino‐6‐aryl‐8,9‐dihydropyrimido[4,5‐b][1,4]diazepin‐4(7H)‐ones 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l , 5m , 5n , 5o were prepared regioselectively by the reaction of 2‐alkylamino‐5,6‐diaminopyrimidin‐4(3H)‐ones 3a , 3b , 3c and dimethylamino propiophenones (Mannich bases) 4a , 4b , 4c , 4d , 4e , 4f . The combination of conventional heating and microwave irradiation approaches provided the possibility of working with both stable and sensitive diaminopyrimidines by controlling parameters such as reaction rates, temperature, and power of irradiation. All products were fully characterized by detailed NMR measurements. 相似文献