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61.
62.
In this paper, we propose a new high accuracy numerical method of O(k2 + k2h2 + h4) based on off-step discretization for the solution of 3-space dimensional non-linear wave equation of the form utt = A(x,y,z,t)uxx + B(x,y,z,t)uyy + C(x,y,z,t)uzz + g(x,y,z,t,u,ux,uy,uz,ut), 0 < x,y,z < 1,t > 0 subject to given appropriate initial and Dirichlet boundary conditions, where k > 0 and h > 0 are mesh sizes in time and space directions respectively. We use only seven evaluations of the function g as compared to nine evaluations of the same function discussed in and . We describe the derivation procedure in details of the algorithm. The proposed numerical algorithm is directly applicable to wave equation in polar coordinates and we do not require any fictitious points to discretize the differential equation. The proposed method when applied to a telegraphic equation is also shown to be unconditionally stable. Comparative numerical results are provided to justify the usefulness of the proposed method. 相似文献
63.
Chary NS Herrera S Gómez MJ Fernández-Alba AR 《Analytical and bioanalytical chemistry》2012,404(6-7):1993-2006
A new analytical method using stir-bar-sorptive extraction (SBSE) followed by liquid desorption (LD) and gas chromatography with triple-quadrupole mass spectrometric detection (GC-QqQ-MS-MS) has been used for quantitative determination of 25 chlorinated endocrine-disrupting compounds (EDCs) in river water and wastewater. The experimental conditions affecting the SBSE-LD performance were studied and are discussed in detail. Results from systematic assay revealed that a 100-mL water sample, stir bars coated with 47?μL PDMS, an extraction time of 14?h (at 900?rpm), 5?% MeOH as modifier and 10?% NaCl resulted in the best analytical recovery of all the target compounds studied. Use of 1:1 ACN-MeOH as back-extraction solvent and two successive sonication steps, each for 5?min, resulted in the best performance for monitoring EDCs in water matrices. The method detection limits for most of the target compounds were very good- ≤?2?ng?L(-1) and ≤10?ng?L(-1) for river water and wastewater effluents respectively. Experimental recovery for all the compounds was >70?%, with the exception of simazine for which recovery from the matrix was 65?%. Signal enhancement observed for a few of the compounds in wastewater effluents was managed by use of matrix-matched standards and different injection liners. The method was successfully used for analysis of river water samples from Henares River (Spain) and wastewater effluent samples from wastewater-treatment plants (WWTP). Eleven of the 25 compounds studied were detected in both river water and wastewater effluents. Terbutylazine and methoxychlor were detected in almost all the river water and effluent samples; amounts varied between 37-58.5?ng?L(-1) and 15.2-46.8?ng?L(-1), respectively. This method was shown enable reliable, effective, and sensitive monitoring of chlorinated EDCs at nanogram levels in surface water and wastewater effluent. 相似文献
64.
Naresh Chary V Dinesh Kumar Ch Vairamani M Prabhakar S 《Journal of mass spectrometry : JMS》2012,47(1):79-88
Betaines belong to the naturally occurring osmoprotectants or compatible solutes present in a variety of plants, animals and microorganisms. In recent years, metabolomic techniques have been emerging as a fundamental tool for biologists because the constellation of these molecules and their relative proportions provide with information about the actual biochemical condition of a biological system. Therefore, identification and characterization of biologically important betaines are crucial, especially for metabolomic studies. Most of the natural betaines are derived from amino acids and related homologues. Although, theoretically, all the amino acids can be converted to corresponding betaines by simple methylation of the amine group, only a few of the amino acid-derived betaines were fully characterized in the literature. Here, we report a combined electrospray ionization tandem and high-resolution mass spectrometry study of all the betaines derived from amino acids, including the isomeric betaines. The decomposition pathway of protonated, sodiated and potassiated molecule ions that enable unambiguous characterization of the betaines including the isomeric betaines and overlapping ionic species of different betaines is distinctive. 相似文献
65.
66.
Pavankumar Pallerla Sudarshana Reddy Bhumireddy Sai Sachin Lingampally Nagarjuna Chary Ragi Prabhakar Sripadi 《Journal of mass spectrometry : JMS》2019,54(9):761-771
Methylation is one of the important posttranslational modifications of biological systems. At the metabolite level, the methylation process is expected to convert bioactive compounds such as amino acids, fatty acids, lipids, sugars, and other organic acids into their methylated forms. A few of the methylated amino acids are identified and have been proved as potential biomarkers for several metabolic disorders by using mass spectrometry–based metabolomics workstation. As it is possible to encounter all the N‐methyl forms of the proteinogenic amino acids in plant/biological systems, it is essential to have analytical data of all N‐methyl amino acids for their detection and identification. In earlier studies, we have reported the ESI‐MS/MS data of all methylated proteinogenic amino acids, except that of mono‐N‐methyl amino acids. In this study, the N‐methyl amino acids of all the amino acids ( 1 ‐ 21 ; including one isomeric pair) were synthesized and characterized by ESI‐MS/MS, LC/MS/MS, and HRMS. These data could be useful for detection and identification of N‐methyl amino acids in biological systems for future metabolomics studies. The MS/MS spectra of [M + H]+ ions of most N‐methyl amino acids showed respective immonium ions by the loss of (H2O, CO). The other most common product ions detected were [MH‐(NH2CH3]+, [MH‐(RH)]+ (where R = side chain group) ions, and the selective structure indicative product ions due to side chain and N‐methyl group. The isomeric/isobaric N‐methyl amino acids could easily be differentiated by their distinct MS/MS spectra. Further, the MS/MS of immonium ions inferred side chain structure and methyl group on α‐nitrogen of the N‐methyl amino acids. 相似文献
67.
Parameshwara Chary Jilloju Allam Vinaykumar Perugu Shyam Rajeswar Rao Vedula 《Journal of heterocyclic chemistry》2019,56(3):1012-1019
A facile and simple one‐pot procedure for the synthesis of various aralkyl/alkylthio‐3,5‐dimethyl‐1H‐pyrazolyl‐4H‐1,2,4‐triazol‐4‐amines has been described via a multicomponent reaction of 4‐amino‐5‐hydrazinyl‐4H‐1,2,4‐triazole‐3‐thiol, acetylacetone, and various aryl/alkyl halides in good yields. All the newly synthesized compounds were characterized by using analytical and spectral studies. Our in silico studies confirmed that 4e , 4f , 4g , and 4j have the best inhibition activity among the synthesized compounds with a high selective index against the Tubulin protein and showed best interactions with receptor structure. The present study provides a novel series of compounds with a promising inhibitor to prevent on Tubulin protein. 相似文献
68.
V. Keshava Rao T. Jaganmohana Chary A. Krishna Murthy 《Journal of Chemical Sciences》1992,104(5):569-576
Sunlight photolysis of 4,5-diphenylisoxazole (1) in methanol sensitized by benzophenone gives 4,4′,5,5′-tetraphenyl-2,2′-bioxazole, (4). On irradiation at 350nm in acetone or at 253.7 nm in absolute alcohol, isoxazole (1) yields α-benzoylphenylacetonitrile (6) besides the expected phenanthro [9,10-d]-oxazole (5). The bioxazole and the ketonitrile have been identified by single crystal X-ray studies. 相似文献
69.
Carbon dioxide reforming (CDR) of methane to synthesis gas over supported nickel catalysts has been reviewed. The present
review mainly focuses on the advantage of ceria based nickel catalysts for the CDR of methane. Nickel catalysts supported
on ceria–zirconia showed the highest activity for CDR than nickel supported on other oxides such as zirconia, ceria and alumina.
The addition of zirconia to ceria enhances the catalytic activity as well as the catalyst stability. The catalytic performance
also depends on the crystal structure of Ni–Ce–ZrO2. For example, nickel catalysts co-precipitated with Ce0.8Zr0.2O2 having cubic phase gave synthesis gas with CH4 conversion more than 97% at 800 °C and the activity was maintained for 100 h during the reaction. On the contrary, Ni–Ce–ZrO2 having tetragonal phase (Ce0.8Zr0.2O2) or mixed oxide phase (Ce0.5Zr0.5O2) deactivated during the reaction due to carbon formation. The enhanced catalytic performance of co-precipitated catalyst
is attributed to a combination effect of nano-crystalline nature of cubic Ce0.8Zr0.2O2 support and the finely dispersed nano size NiO
x
crystallites, resulting in the intimate contact between Ni and Ce0.8Zr0.2O2 particles. The Ni/Ce–ZrO2/θ–Al2O3 also exhibited high catalytic activity during CDR with a synthesis gas conversion more than 97% at 800 °C without significant
deactivation for more than 40 h. The high stability of the catalyst is mainly ascribed to the beneficial pre-coating of Ce–ZrO2 resulting in the existence of stable NiO
x
species, a strong interaction between Ni and the support, and an abundance of mobile oxygen species in itself. TPR results
further confirmed that NiO
x
formation was more favorable than NiO or NiAl2O4 formation and further results suggested the existence of strong metal-support interaction (SMSI) between Ni and the support.
Some of the important factors to optimize the CDR of methane such as reaction temperature, space velocity, feed CO2/CH4 ratio and H2O and/or O2 addition were also examined. 相似文献
70.
Srinivas Kantevari Mahankhali Venu Chary Srinivasu V. N. Vuppalapati N. Lingaiah 《Journal of heterocyclic chemistry》2008,45(4):1099-1102