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581.
Javad Beheshtian Ali Ahmadi Peyghan Zargham Bagheri Mohammad Bigdeli Tabar 《Structural chemistry》2014,25(1):1-7
Graphyne, a lattice of benzene rings connected by acetylene bonds, is one-atom-thick planar sheet of sp- and sp2-bonded carbons differing from the hybridization of graphene (considered as pure sp2). Here, HCN adsorption on the pristine and Si-doped graphynes was studied using density-functional calculations in terms of geometric, energetic, and electronic properties. It was found that HCN molecule is weakly adsorbed on the pristine graphyne and slightly affects its electronic properties. While, Si-doped graphyne shows high reactivity toward HCN, and, in the most favorable state, the calculated adsorption energy is about ?10.1 kcal/mol. The graphyne, in which sp-carbon was substituted by Si atom, is more favorable for HCN adsorption in comparison with sp2-carbon. It was shown that the electronic properties of Si-doped graphyne are strongly sensitive to the presence of HCN molecule and therefore it may be used in sensor devices. 相似文献
582.
Farzaneh Zanjanchi Nasser L. Hadipour Hassan Sabzyan Javad Beheshtian 《Journal of the Iranian Chemical Society》2014,11(1):111-121
Electronic absorption spectra and the frontier orbitals of 1-arylazo-2-naphtol dyes are computed and analyzed in four models, namely in the gas phase (model I), in a solvent (model I + CPCM), adsorbed on the cellulose surface (model II), and model II in the presence of solvent (model II + CPCM) via time-dependent density functional theory (TD-DFT) and conductor-like polarizable continuum model (CPCM) at the B3LYP/6-31G** level of theory. A bathochromic shift is observed for the λmax peak due to both short-range and long-range interactions of the non-ionic dyes with cellulose, while the ionic dyes exhibit hypsochromic shift in their λmax peak. The results predict that the studied dyes should be nearly yellow after being adsorbed on cellulose with excellent color strength. Furthermore, the ionic dyes are suitable for the dyeing of cellulose fibers. The nuclear magnetic resonance (NMR) chemical shieldings calculated for the azo dyes in the gas phase and adsorbed states and for their tautomeric equilibrium mixtures show that the NMR technique can be used successfully to follow the dyeing process. 相似文献
583.
Extraction of aflatoxins from food samples using graphene‐based magnetic nanosorbents followed by high‐performance liquid chromatography: A simple solution to overcome the problems of immunoaffinity columns 下载免费PDF全文
Zarrin Es'haghi Hamed Reza Beheshti Javad Feizy 《Journal of separation science》2014,37(18):2566-2573
In this research, magnetic graphene nanoparticles were prepared and used as adsorbents for preconcentrating the aflatoxins in rice, wheat, and sesame samples. For this purpose, graphene was synthesized by Hummer's method. Magnetically modified graphene formed by the deposition of magnetite (Fe3O4) on graphene was used for the separation of aflatoxins B1, B2, G1, and G2 from the samples. The extractants were subsequently analyzed with high‐performance liquid chromatography and fluorescence detection. Parameters affecting the efficiency of the method were thoroughly investigated. The measurements were done under the optimized conditions. For aflatoxins B1, B2, G1, and G2, limits of detection were 0.025, 0.05, 0.05, and 0.075 ng/g and limits of quantification were 0.083, 0.16, 0.16, and 0.23 ng/g, respectively. Accuracy was examined by the determination of the relative recovery of the aflatoxins. The relative recovery of aflatoxins B1, B2, G1, and G2 were quite satisfactory (between 64.38 and 122.21% for food samples). Relative standard deviations for within laboratory repeatability (n = 6) were in the range from 1.3 to 3.2. The application of this sorbent for the separation and concentration of the mentioned aflatoxins from food samples was examined. 相似文献
584.
A series of 2-(thiazol-2-yl)-4,5-dihydropyridazin-3(2H)-one derivatives were synthesized by one-pot multicomponent cyclocondensation of ketoacid, thiosemicarbazide, and phenacyl bromide using catalytical amount of KSF in EtOH under reflux. The straightforward synthesis, presence of two important class of heterocyclic rings in the individual molecule, easy workup of the products, rapid reaction, mild conditions, and good to excellent yields are notable features of this protocol.
[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] 相似文献
585.
Javad Ghafari Masoomeh Vahabi Somayeh Farhang Dehghan Rezvan Zendehdel 《Biomedical chromatography : BMC》2020,34(10):e4924
Monitoring the trace amount of chemicals in various samples remains a challenge. This study was conducted to develop a new solid-phase microextraction (SPME) system (inside-tube SPME) for trace analysis of n-hexane in air and urine matrix. The inside-tube SPME system was prepared based on the phase separation technique. A mixture of carbon aerogel and polystyrene was loaded inside the needle using methanol as the anti-solvent. The air matrix of n-hexane was prepared in a Tedlar bag, and n-hexane vapor was sampled at a flow rate of 0.1 L/min. Urine samples spiked with n-hexane were used to simulate the sampling method. The limit of detection using the inside-tube SPME was 0.0003 μg/sample with 2.5 mg of adsorbent, whereas that using the packed needle was 0.004 μg/sample with 5 mg of carbon aerogel. For n-hexane analysis, the day-to-day and within-day coefficient variation were lower than 1.37%, with recoveries over 98.41% achieved. The inside-tube SPME is an inter-link device between two sample preparation methods, namely, a needle trap device and an SPME system. The result of this study suggested the use of the inside-tube SPME containing carbon aerogel (adsorbent) as a simple and fast method with low cost for n-hexane evaluation. 相似文献
586.
Mahmood Tajbakhsh Manijeh Karimi Mohammad Javad Chaichi Mohammad A. Khalilzadeh Saeed Haghighi 《Monatshefte für Chemie / Chemical Monthly》2008,139(1):13-15
Summary. In this paper two methods are presented. One involves the separation of cholecalciferol from a topical ointment. The other
involves the assay of cholecalciferol in this ointment. The study was performed with normal-phase high performance liquid
chromatography using a NP-L3 column and UV detection. Applying a mobile phase mixture containing n-hexane:2-propanol (99:1) a total separation was achieved within 15 min. For isolation and assay of cholecalciferol from an
ointment (vitamin A + D), dissolution in n-hexane gave the highest recovery (>95%). The isolation and assay process can be performed within 3.5 h. 相似文献
587.
Enhanced spectrofluorimetric determination of aflatoxin B1 in wheat by second-order standard addition method 总被引:1,自引:0,他引:1
Determination of aflatoxin B1 (AFB1) in wheat has been accomplished by enhanced spectrofluorimetry in combination with second-order standard addition method (EF-SOSAM). The adopted strategy combined the use of parallel factor analysis (PARAFAC) for extraction of the pure analyte signal and the standard addition method, for a determination in the presence of matrix effect caused by wheat matrix. The method is based on the enhanced fluorescence of AFB1 by beta-cyclodextrin in 10% (w/w) methanol-water solution. After sample treatment and without any extended cleanup steps and derivatization process, four standard additions were performed for each sample. A specific PARAFAC model was built from three-way arrays formed by excitation-emission spectra and 5 measurements (sample plus 4 additions). The scores related to AFB1 were used for a linear regression in the standard addition method. Two naturally contaminated wheat and spiked wheat samples containing AFB1 in the range 0-18 microg kg(-1) were analyzed by EF-SOSAM and compared with HPLC results. EF-SOSAM analysis of spiked wheat samples gave a good correlation with spiked values (R(2)>0.990). The limit of detection of method was 0.9 microg kg(-1) for the determination of AFB1 in wheat samples. 相似文献
588.
Both aryl and alkyl imines, which formed in situ from aldehydes and amines undergo smooth nucleophilic addition with trimethylsilyl cyanide in the presence of a catalytic amount of a silica-based scandium (III) interphase catalyst under mild reaction condition to furnish the corresponding α-aminonitriles in good to excellent yields. The catalyst shows high thermal stability (up to 300 °C) and it could also be recovered and reused for at least 6 reaction cycles without considerable lose of its reactivity. 相似文献
589.
Nematollahi D Azizian J Sargordan-Arani M Hesari M Jameh-Bozorghi S Alizadeh A Fotouhi L Mirza B 《Chemical & pharmaceutical bulletin》2008,56(11):1562-1566
The 4-(dihydroxyphenylthio)-2H-chromen-2-one derivatives have been synthesized by direct electrochemical oxidation of catechols in the presence of 4-mercaptocoumarin as a nucleophile in water/acetonitrile (50/50) solution, in a one-pot process, at carbon rod electrode, in an undivided cell and in constant current conditions, through an EC mechanism. The products are characterized by spectra data. Besides, the difference in electrochemical oxidation of catechol in the presence of 4-hydroxycoumarin and 4-mercaptocoumarin explained by computational structure, natural bond orbital (NBO) analysis and density functional theory (DFT: B3LYP/6-31G*//B3LYP/6-31G*) based methods, using the GAUSSIAN 98 package of programs. 相似文献
590.
We have examined the specificity of electrosynthesized poly-o-phenylenediamine as a kind of material molecularly imprinted with metal chelates. Molecularly imprinted polymers (MIPs) were prepared in situ by an electrochemical method. The EDTA chelate complexes of Cu(II), Zn(II), Fe(III) and Cd(II) ions were used as templates of the MIPs deposited on a gold electrode of a quartz crystal microbalance (QCM). The binding ability and specificity of the MIPs were investigated via the frequency response of the QCM to the adsorption of the template chelates and their analogs. Linear relationships are observed between the frequency shift and the concentration of the template chelates over a typical range of ~10?6 to ~10?4?mol·L?1. The results reveal good binding specificity of such MIPs for their templates over structurally related analogs, but the selectivity coefficients are less significant than that for enantiomers. The results also suggest no significant correlation between binding specificity and the ionic (or atomic) radius of the investigated metal ions. The observed specificity is qualitatively attributed to the overall conformational difference of the metal-EDTA complexes resulting from their difference in both ionic radius and electronic structures. Figure
Schematic Representation of the Molecular Imprinting Procedures. The metal ions chelate with EDTA to form metal-EDTA chelates as the template, then polymerization is initiated by an electrochemical method. After the polymerization, the templates are removed to create cavities in the polymer film which have binding ability and specificity to the templates. 相似文献