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排序方式: 共有196条查询结果,搜索用时 15 毫秒
71.
A rapid and diverse synthesis of biologically important 6-substituted-5,6-dihydro-4-hydroxy-2-pyrones through a double Reformatsky reaction of aldehydes to δ-hydroxy-β-ketoesters followed by lactonization is described. Due to the high functional group tolerance and reaction site discrimination between aldehyde, nitrile, and ester groups in the substrate, the protocol can provide the dihydropyrones with bromo, nitro, carboxylic acid, and β-ketoester groups, which are suitable for the further derivatizations. Furthermore, the protocol has been successfully applied to the rapid total synthesis of naturally occurring Yangonin. 相似文献
72.
Chetsumon A. Miyamoto K. Hirata K. Miura Y. Ikuta Y. Hamasaki A. 《Applied biochemistry and biotechnology》1993,39(1):573-586
Applied Biochemistry and Biotechnology - A fresh-water, nitrogen-fixing blue-green alga (cyanobacterium),Scytonema sp. No. 11 (TISTR 8208), was isolated from a paddy field in northern Thailand.... 相似文献
73.
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75.
Hammad SF Mabrouk MM Habib A Elfatatry H Kishikawa N Nakashima K Kuroda N 《Biomedical chromatography : BMC》2007,21(10):1030-1035
A highly selective and sensitive method was developed for simultaneous determination of the antihistaminic drug hydroxyzine (HZ) and its pharmacologically active metabolite cetirizine (CZ) in human serum using haloperidol as internal standard. The method was based on fluorescence labeling of both drugs with a fluorescent arylboronic acid 4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl boronic acid followed by separation on silica column using a mobile phase consisting of acetonitrile and water (90:10, v/v%) containing triethylamine and acetic acid. The labeling reaction conditions were optimized and the liquid-liquid extraction method was successfully applied to extract the both drugs from serum. The linearity range was 0.025-2.00 microg/mL for HZ and CZ. The limit of detection (S/N = 3) was 10 and 5 ng/mL for HZ and CZ, respectively. 相似文献
76.
Azumi Higashi Naoya Kishikawa Kaname Ohyama Naotaka Kuroda 《Tetrahedron letters》2017,58(28):2774-2778
Benzofuran-2-boronic acid could be used as a fluorescent sensor for the detection of Pd2+ because it was rapidly converted to highly fluorescent derivative after mixing with Pd2+ under basic condition at room temperature. We found that dimerization of benzofuran was occurred to form fluorescent derivative by the catalytic activity of palladium. The fluorescence intensity at 360 nm increased with increasing the concentration of Pd2+. The excellent selectivity for Pd2+ was demonstrated among other metal ions. Based on this findings, we successfully applied benzofuran-2-boronic acid to develop a microplate-based assay for high-throughput measurement of Pd2+. The detection limit (blank + 3SD) for Pd2+ of the proposed assay was 9.8 nM. 相似文献
77.
Nakamura S Wada M Crabtree BL Reeves PM Montgomery JH Byrd HJ Harada S Kuroda N Nakashima K 《Analytical and bioanalytical chemistry》2007,387(6):1983-1990
A sensitive semi-micro column HPLC method with peroxyoxalate chemiluminescence (POCL) detection and column switching has been
developed for simultaneous determination of 3,4-methylenedioxymethamphetamine (MDMA) and related compounds, for example 3,4-methylenedioxyamphetamine,
methamphetamine, and amphetamine, in hair. After digestion of the hair with 1 mol L−1 sodium hydroxide the compounds were extracted with n-heptane and derivatized with 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole. A mixture of hydrogen peroxide and bis(2,4,5-trichloro-6-carbopentoxyphenyl)oxalate
in acetonitrile was used as post-column CL reagent. Calibration plots showed linearity was good (r = 0.999); detection limits were 0.02–0.16 ng mg−1 hair at a signal-to-noise ratio of 3. The precision of the method, as RSD (n = 5), in intra-day and inter-day assays was better than 5.0 and 6.9%, respectively. The proposed method was sufficiently
sensitive to detect low ng mg−1 levels of MDMA and related compounds in hair, and could be used for quantification of the compounds in hair samples from
patients treated in a chemical dependency unit. 相似文献
78.
Poly(l‐lactic acid)‐modified silica stationary phase for reversed‐phase and hydrophilic interaction liquid chromatography
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Kaname Ohyama Shizuka Takasago Naoya Kishikawa Naotaka Kuroda 《Journal of separation science》2015,38(5):720-723
Poly(l ‐lactic acid) is a linear aliphatic thermoplastic polyester that can be produced from renewable resources. A poly(l ‐lactic acid)‐modified silica stationary phase was newly prepared by amide bond reaction between amino groups on aminopropyl silica and carboxylic acid groups at the end of the poly(l ‐lactic acid) chain. The poly(l ‐lactic acid)‐silica column was characterized in reversed‐phase liquid chromatography and hydrophilic interaction liquid chromatography with the use of different mobile phase compositions. The poly(l ‐lactic acid)‐silica column was found to work in both modes, and the retention of test compounds depending on acetonitrile content exhibited “U‐shaped” curves, which was an indicator of reversed‐phase liquid chromatography/hydrophilic interaction liquid chromatography mixed‐mode retention behavior. In addition, carbonyl groups included into the poly(l ‐lactic acid) backbone work as an electron‐accepting group toward a polycyclic aromatic hydrocarbon and provide π–π interactions. 相似文献
79.
Kishikawa N Ohkuma M Wada M Ohyama K Ikeda R Nakashima K Kuroda N 《Journal of chromatography. A》2011,1218(20):3002-3006
A novel fluorescent labeling method for alprenolol was developed based on Mizoroki-Heck coupling reaction. We designed and synthesized fluorescent aryl iodide, 4-(4,5-diphenyl-1H-imidazol-2-yl)iodobenzene (DIBI) as a labeling reagent. DIBI has a lophine skeleton carrying an iodide atom acting as fluorophore and reactive center, respectively. In order to evaluate the usefulness of DIBI, a high-performance liquid chromatography (HPLC) with fluorescence detection method was developed for the determination of alprenolol as a model compound of terminal double bond. The fluorescent labeling of alprenolol with DIBI was achieved in the presence of palladium acetate as a catalyst, and the labeled alprenolol was detected fluorometrically. In addition, it was found that the fluorescence of DIBI derivative increased and red shifted when compared with that of DIBI. Furthermore, the proposed method could be applied to determine the alprenolol concentration in rat plasma after administration of alprenolol without interferences from biological components. The detection limit (S/N=3) for alprenolol in rat plasma was 0.74 ng/mL (30 fmol on column). 相似文献
80.
Futamura R Iiyama T Hamasaki A Ozeki S 《Physical chemistry chemical physics : PCCP》2012,14(2):981-986
The density and intermolecular structure of water in carbon micropores (w = 1.36 nm) are investigated by small-angle X-ray scattering (SAXS) and X-ray diffraction (XRD) measurements between 20 K and 298 K. The SAXS results suggest that the density of the water in the micropores increased with increasing temperature over a wide temperature range (20-277 K). The density changed by 10%, which is comparable to the density change of 7% between bulk ice (I(c)) at 20 K and water at 277 K. The results of XRD at low temperatures (less than 200 K) show that the water forms the cubic ice (I(c)) structure, although its peak shape and radial distribution functions changed continuously to those of a liquid-like structure with increasing temperature. The SAXS and XRD results both showed that the water in the hydrophobic nanospaces had no phase transition point. The continuous structural change from ice I(c) to liquid with increasing temperature suggests that water shows negative thermal expansion over a wide temperature range in hydrophobic nanospaces. The combination of XRD and SAXS measurements makes it possible to describe confined systems in nanospaces with intermolecular structure and density of adsorbed molecular assemblies. 相似文献