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51.
Nano-baskets of calixarenes have been subject to extensive research in the construction of liquid chromatographic phases, extractants, transporters, electrode ionophores, and optical and electrochemical sensors over the past 4 decades. There has long been interest in calixarene-based liquid chromatographic phases. Owing to the recent rapid growth in the number of publications on calixarene-based liquid chromatographic phases, this review paper focuses on their different applications in the main fields of molecular and ionic species as well as liquid chromatographic mobile and stationary phases. Although the recent reports have focused on the optimization and application of one kind or a unique group of calixarenic mobile or stationary phases, this review is a collection and comparison of a variety of research data dealing with the synthesis, preparation and behavior of calixarene-based liquid chromatographic phases. 相似文献
52.
A new micelle-mediated phase preconcentration method for preconcentration of ultra-trace quantities of beryllium as a prior step to its determination by spectrophotometry has been developed. Chrome Azurol S (CAS) and cetyltrimethylammonium bromide (CTAB) were used as chelating agent and cationic surfactant, respectively. The method evaluates and eliminates the blank bias error present in such procedures using mean centering of ratio spectra. This procedure gives more accurate results than the traditional approach using absorbance values against reagent blank. The optimal extraction and reaction conditions were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration and improvement factors) were obtained. Linearity was obeyed in the range of 0.9-18.0 ng mL−1 (1.00 × 10−7-2.00 × 10−6 mol L−1) of beryllium. The detection limit of the method is 0.51 ng mL−1 (5.66 × 10−8 mol L−1) of beryllium. The interference effect of some anions and cations was also tested. The method was applied to the determination of beryllium in spring water samples. 相似文献
53.
A new convenient colorimetric sensor for fructose based on anti-aggregation of citrate-capped gold nanoparticles(Au NPs) is presented. 4-Mercaptophenylboronic acid(MPBA) induces the aggregation of Au NPs, leading to a color change from red to blue. Fructose as a potent competitor has strong affinity for MPBA and a borate ester is formed between MPBA and fructose. There is an obvious color change from blue to red with increasing the concentration of fructose. The anti-aggregation effect of fructose on Au NPs was seen by the naked eye and monitored by UV–vis spectra. Our results showed that the absorbance ratio(A_(519)/A_(640)) was linear with fructose concentration in the range of 0.032–0.96 μmol/L(R~2= 0.996), with a low detection limit of 0.01 μmol/L(S/N = 3). Notably, a highly selective recognition of fructose was shown against other monosaccharide and disaccharide(glucose, mannose, galactose,lactose and saccharose). With anti-aggregation assays higher selectivity is achievable. The results of this work provide a rapid method for evaluating the quantitative analysis of fructose in human plasma at physiologically meaningful concentrations and at neutral pH. The proposed procedure can be used as an efficient method for the precise and accurate determination of fructose. 相似文献
54.
To find metal ion recognition by L (L = O2N2-donor naphthodiaza-crown macrocyclic ligand), the complexes [ML]2+ (M = Cd, Hg and Pb) were synthesized and characterized by IR, 1H, 13C NMR, and mass spectrometry, as well as elemental microanalysis. Hg(II) showed perceptible enhancement of the fluorescence of L in which ultra-low limit of detection for Hg(II) by L was determined as 1 nM in ethanol and DMSO. L reserved selectivity of Hg(II) in its binary mixtures with metal cations in solution. A 1 : 1 stoichiometry was found for the interaction of Hg(II) with L while Benesi–Hildebrand method was applied to calculate its complexation binding constant (KBH) employing fluorescence spectrophotometry. The monitoring of the chemical shifts in 1H NMR spectra of these complexes demonstrated that the central macrocycle of L was tailored for the size of Hg(II). Density functional theory calculations using B3LYP/6–31G* basis set demonstrated that the macrocycle cavity of L was properly fitted for complex formation with Hg(II) cation, while both Cd(II) and Pb(II) cations did not form strong bonds with L from inadequate cation size. The present study shows detection method of Hg(II) and also possible application of naphthodiaza as an appropriate fluorophore macrocyclic ligand for detecting other metal ions. 相似文献
55.
BAKHERAD Mohammad BAHRAMIAN Bahram NASR-ISFAHANI Hossein KEIVANLOO Ali SANG Golnaz 《中国化学》2009,27(2):353-358
The polymer-supported palladium(II) ethylenediamine complex was used as a catalyst for the heterocyclization during Sonogashira reaction between a substituted phenyl iodide and 2-amino-3-(2-propynyl)-1,3-benzothiazolium bromide, which could readily be recovered from the reaction medium by a simple filtration, and reused without a significant loss in its activity. 相似文献
56.
Bahram Hemmateenejad Saeed Yousefinejad 《Analytical and bioanalytical chemistry》2009,394(7):1965-1975
This article describes the use of the net analyte signal (NAS) concept and rank annihilation factor analysis (RAFA) for building
two different multivariate standard addition models called “SANAS” and “SARAF.” In the former, by the definition of a new
subspace, the NAS vector of the analyte of interest in an unknown sample as well as the NAS vectors of samples spiked with
various amounts of the standard solutions are calculated and then their Euclidean norms are plotted against the concentration
of added standard. In this way, a simple linear standard addition graph similar to that in univariate calibration is obtained,
from which the concentration of the analyte in the unknown sample and the analytical figures of merit are readily calculated.
In the SARAF method, the concentration of the analyte in the unknown sample is varied iteratively until the contribution of
the analyte in the response data matrix is completely annihilated. The proposed methods were evaluated by analyzing simulated
absorbance data as well as by the analysis of two indicators in synthetic matrices as experimental data. The resultant predicted
concentrations of unknown samples showed that the SANAS and SARAF methods both produced accurate results with relative errors
of prediction lower than 5% in most cases. 相似文献
57.
58.
The mean centering of ratio kinetic profiles method was used for the simultaneous determination of binary mixtures of Ni(II) and Zn(II) in water samples, without prior separation steps. The method is based on the difference in the rate of the reaction of Ni(II) and Zn(II) with xylenol orange at pH 5.3. The method allows rapid and accurate determination of Ni(II) and Zn(II). The analytical characteristics of the methods for the simultaneous determination of binary mixtures of Ni(II) and Zn(II) were calculated. The linear range was 0.025‐2.400 μg mL?1 and 0.025‐2.20 μg mL?1 for Zn(II) and Ni(II), respectively. Interference effects of common anions and cations were studied, and the method was successfully applied to the simultaneous determination of Zn(II) and Ni(II) in water samples. 相似文献
59.
Spin Fidelity for Three-Qubit Greenberger-Horne-Zeilinger and W States Under Lorentz Transformations
Bahram Nasr Esfahani Mohsen Aghaee 《International Journal of Theoretical Physics》2011,50(5):1395-1406
Constructing the reduced density matrix for a system of three massive spin-
\frac12\frac{1}{2} particles described by a wave packet with Gaussian momentum distribution and a spin part in the form of GHZ or W state, the
fidelity for the spin part of the system is investigated from the viewpoint of moving observers in the jargon of special relativity.
Using a numerical approach, it turns out that by increasing the boost speed, the spin fidelity decreases and reaches to a
non-zero asymptotic value that depends on the momentum distribution and the amount of momentum entanglement. 相似文献
60.
Anke Hammer Bahram Mohammadi Marlen Schmicker Sina Saliger Thomas F Münte 《BMC neuroscience》2011,12(1):1-9