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101.
Hydroethanolic extracts of C. langsdorffii leaves have therapeutic potential. This work reports a validated chromatographic method for the quantification of polar compounds in the hydroethanolic extract of C. langsdorffii leaves. A reliable HPLC method was developed using two monolithic columns linked in series (100 x 4.6 mm - C18), with nonlinear gradient elution, and UV detection set at 257 nm. A procedure for the extraction of flavonols was also developed, which involved the use of 70% aqueous ethanol and the addition of benzophenone as the internal standard. The developed method led to a good detection response as the values for linearity were between 10.3 and 1000 microg/mL, and those for recovery between 84.2 and 111.1%. The detection limit ranged from 0.02 to 1.70 microg/mL and the quantitation limit from 0.07 to 5.1 microg/mL, with a maximum RSD of 5.24%. Five compounds, rutin, quercetin-3-O-alpha-L-rhamnopyranoside, kaempferol-3-O-alpha-L-rhamnopyranoside, quercetin and kaempferol, were quantified. This method could, therefore, be used for the quality control of hydroethanolic extracts of Copaifera leaves and their cosmetic and pharmaceutical products. 相似文献
102.
César Ortega López William López Pérez Jairo Arbey Rodríguez M. 《Applied Surface Science》2009,255(6):3837-3842
We report first principles calculations to analyze the ruthenium adsorption and diffusion on GaN(0 0 0 1) surface in a 2×2geometry. The calculations were performed using the generalized gradient approximation (GGA) with ultrasoft pseudopotential within the density functional theory (DFT). The surface is modeled using the repeated slabs approach. To study the most favorable ruthenium adsorption model we considered T1, T4 and H3 special sites. We find that the most energetically favorable structure corresponds to the Ru- T4 model or the ruthenium adatom located at the T4 site, while the ruthenium adsorption on top of a gallium atom (T1 position) is totally unfavorable. The ruthenium diffusion on surface shows an energy barrier of 0.612 eV. The resultant reconstruction of the ruthenium adsorption on GaN(0 0 0 1)- 2×2 surface presents a lateral relaxation of some hundredth of Å in the most stable site. The comparison of the density of states and band structure of the GaN(0 0 0 1) surface without ruthenium adatom and with ruthenium adatom is analyzed in detail. 相似文献
103.
Elena E. Stashenko Martha Cervantes Yajaira Combariza Hernn Fuentes Jairo Ren Martínez 《Journal of separation science》1999,22(6):343-349
Steam distillation (SD), simultaneous distillation-solvent extraction (SDE), microwave-assisted solvent extraction (MWE), and supercritical (CO2) extraction (SFE) were used to isolate secondary metabolites from Lepechinia schiedeana. The various extracts were analyzed by capillary gas-chromatography, on poly (dimethylsiloxane) (DB-1) and poly(ethyleneglycol) (INNOWAX), 60 m columns, using FID or MSD (EI, 70 eV). Kováts indexes, mass spectra, or standard compounds were employed for compound identification. 43, 61, 67, and 79 compounds at concentrations above 0.01% were detected in the SD, SDE, MWE, and SFE extracts, respectively. Ledol, C15H26O, was the major constituent (20.04–36.87%) in all extracts. Oxygenated sesquiterpenes (24.36–43.14%), C10H16, monoterpenes (27.70–39.87%), and C15H24, sesquiterpenes (10.04–22.22%) were the main groups of compounds present in SD, SDE, MWE, and SFE extracts. Heavy hydrocarbons (Cn > 15), diterpenoids, and phytosterols were found only in MWE and SFE extracts. The antioxidant activity of Lepechinia schiedeana was measured by the HRGC quantification of the volatile carbonyl compounds, final products of lipoxidation, released in a model lipid system (sunflower oil) by the effect of the Fenton reagent. The concentration of volatile carbonyl compounds decreased by 65% when lipid oxidation was induced in the presence of macerated Lepechinia plant. The protection of polyunsaturated acids in sunflower oil was also studied by measuring their concentrations after heating of the oil (180°C, 2 h) with and without macerated Lepechinia plant. 相似文献
104.
105.
John Nicolson Low Justo Cobo Manuel Nogueras Adolfo Sánchez Jairo Quiroga Diana Mejía 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(11):1356-1358
Molecules of the title compound, C28H27ClN4O4·C2H6O, form a C(6) chain via an N—H⋯O hydrogen bond along the c axis by the operation of a c-glide plane, with N⋯O = 2.761 (3) Å and N—H⋯O = 165°. The molecules are further linked by a weak C—H⋯O interaction, with C⋯O = 3.344 (4) Å and C—H⋯O = 150°. Pendant hydrogen-bonded ethanol solvent molecules are attached to the chains by O—H⋯N hydrogen bonds, with O⋯N = 2.904 (3) Å and O—H⋯N = 175°. 相似文献
106.
Braulio Insuasty O Henry Insuasty I Jairo Quiroga P Claudio Saitz Carolina Jullian 《Journal of heterocyclic chemistry》1999,36(3):635-638
New 4-Aryl-6-methyl-8-phenyl-2,3-dihydropyrazolo[3,4-b]diazepines and 4-aryl-8-methyl-6-phenyl-2,3-dihydropyrazolo[4,3-b]diazepines were obtained from the reaction of 4,5-diamino-3-methyl-1-phenylpyrazole 1 with one equivalent of the 3-dimethylaminopropiophenones 2 in absolute ethanol. The structures of 4-aryl-6-methyl-8-phenyl-2,3-dihydropyrazolo[3,4-b]diazepines 3 and 4-aryl-8-methyl-6-phenyl-2,3-dihydropyrazolo[4,3-b]diazepines 4 were determined by detailed nmr measurements. 相似文献
107.
Elena Stashenko Jairo Ren Martinez Carlos MacKu Takayuki Shibamoto 《Journal of separation science》1993,16(7):441-444
Samples of essential oil from Colombian ylang-ylang trees were analyzed by means of HRGC, HRGC–MS, IR and 1H- and 13C-NMR. 57 components were detected, 51 of which were positively identified. Camphene and anethol were identified in ylang-ylang essential oil for the first time. Among the composition-determining variables studied (extraction time, part of the flower, and flower freshness), the extraction time and the flower condition (fresh versus dry) were found to have the largest incidence in the quality of the essential oil. 相似文献
108.
Braulio Insuasty Ricaurte Rodriguez Jairo Quiroga Roberto Martinez Enrique Angeles 《Journal of heterocyclic chemistry》1997,34(4):1131-1133
The acid catalyzed condensation of 4,5-diaminopyrazoles and chalcones gave the hitherto unknown 1-benzyl-2,4,6-triphenyl-2,3-dihydropyrazolo[3,4-b][1,4]diazepines derivatives. The structure of all products was supported by ir, 1H and 13C-nmr and mass spectra. 相似文献
109.
Hydrodistillation (HD), simultaneous distillation-solvent extraction (SDE), microwave-assisted hydrodistillation (MWHD), and supercritical fluid (CO2) extraction (SFE), were employed to isolate volatile secondary metabolites from Colombian Xylopia aromatica (Lamarck) fruits. Static headspace (S-HS), simultaneous purge and trap (P&T) in solvent (CH2Cl2), and headspace (HS) solid-phase microextraction (SPME) were utilised to obtain volatile fractions from fruits of X. aromatica trees, which grow wild in Central and South America, and are abundant in Colombia. Kováts indices, mass spectra or standard compounds, were used to identify more than 50 individual components in the various volatile fractions. beta-Phellandrene was the main component found in the HD and MWHD essential oils, SDE and SFE extracts (61, 65, 57, and ca. 40%, respectively), followed by beta-myrcene (9.1, 9.3, 8.2 and 5.1%), and alpha-pinene (8.1, 7.3, 8.1 and 5.9%). The main components present in the volatile fractions of the X. aromatica fruits, isolated by S-HS, P&T and HS-SPME were beta-phellandrene (53.8, 35.7 and 39%), beta-myrcene (13.3, 12.3 and 10.1%), p-mentha-1(7),8-diene (7.1, 10.6 and 10.4%), alpha-phellandrene (2.2, 5.0 and 6.4%), and p-cymene (2.2,4.7 and 4.4%), respectively. 相似文献
110.
da Silva R Heleno VC de Albuquerque S Bastos JK Andrade e Silva ML Donate PM da Silva GV 《Magnetic resonance in chemistry : MRC》2004,42(11):985-989
We describe the complete 1H and 13C NMR analysis of three aryltetralin lignan lactones (polygamain, morelensin and 4,5-dimethoxymorelensin) using modern NMR techniques such as COSY, HMQC, HMBC, 2D-J-resolved and NOE experiments. The relative stereochemistry of these compounds, which is very important with regard to their biological activity, was completely determined. 相似文献