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151.
Hamed Douroudgari Hamed Bahrami Farshad Mirzaee Valadi Manijeh Tozihi Nasim Najafloo Morteza Vahedpour 《Journal of mass spectrometry : JMS》2022,57(3):e4814
The current research is constructed for considering the chemical ionization and dissociation of perindopril in the positive mode of corona discharge ion mobility spectrometry. Four product ion peaks are observed in the ion mobility spectrum of perindopril erbumine at the cell temperature of 473 K. These peaks are assigned through the obtained intensity variation analysis in the ion mobility spectra over the elapsed time accompanied by the calculations backed by the validated density functional theory (DFT). In this regard, the most stable ionic species associated with each peak and the corresponding reliable generation pathways are found by the well-confirmed meta hybrid density functional method, M06-2X. The peaks are assigned to the protonated perindopril and its dissociation products, including counter ion and the related fragment ions. However, the structures of the neutral perindopril in the gas phase are thoroughly assessed to find a more stable one. The predicted chemical ionization products by the theory are in excellent agreement with our presented experiment here. Theoretical evaluations demonstrated that the production of a fragment by dissociation process occurs when perindopril gets a proton from the ionization region. Also, without protons, there is no dissociation process. Therefore, our mechanism investigated here is the proton transfer one. All possible sites of perindopril are considered theoretically for protonation along with their possible reactions. In addition to the computed PES, the assigned ions for obtained spectra are confirmed by the computed equilibrium constants and rate constants. Our theoretical results show that the peak of the main fragment is for M-CH3CH2OH produced by a reaction pathway involving no barrier. This study opens new perspectives in interpreting large molecules spectra for future studies. 相似文献
152.
Ahmad Motahari Abbas Ali Rostami Abdollah Omrani Morteza Ehsani 《Journal of Macromolecular Science: Physics》2015,54(5):517-532
The thermal degradation kinetics of diglycidyl ether of bisphenol-A (DGEBA) cured with tryptophan (Trp) in the presence of silica nanoparticles (SiNP) was investigated by thermogravimetry analysis. The activation energies of the solid-state decomposition process were evaluated using the advanced isoconversional method. The dependence of conversion (degradation) on the temperature and activation energy was determined allowing the calculation of master plots. The experimental master plots agreed with the first-order (F1) kinetic function for both neat epoxy and nanocomposite in the conversion range of 0.45–0.85. Using the kinetic model and the calculated kinetic parameters, the times at half conversion (α = 0.5) were computed for different degradation temperatures. The kinetic analysis showed that the degradation rate of the epoxy nanocomposite was lower than that of the neat epoxy for conversions between 0.45 and 0.85. Therefore, we concluded that adding SiNP to DGEBA/Trp can improve the thermal stability in the conversion range of 0.45–0.85. 相似文献
153.
Akbar Shabanikia Mehran Javanbakht Hossein Salar Amoli Khadijeh Hooshyari Morteza Enhessari 《Ionics》2015,21(8):2227-2236
In this work, Fe2TiO5 nanoparticles were used for improving the proton conductivity, and water and acid uptake of polybenzimidazole (PBI)-based proton exchange membranes. The nanocomposite membranes have been prepared using different amounts of Fe2TiO5 nanoparticles and dispersed into a PBI membrane with the solution-casting method. The prepared membranes were then physico-chemically and electrochemically characterized for use as electrolytes in high-temperature PEMFCs. The PBI/Fe2TiO5 membranes (PFT) showed a higher acid uptake and proton conductivity compared with the pure PBI membranes. The highest acid uptake (156 %) and proton conductivity (78 mS/cm at 180 °C) were observed for the PBI nanocomposite membranes containing 4 wt% of Fe2TiO5 nanoparticles (PFT4). The PFT4 composite membrane showed 380 mW/cm2 power density and 760 mA/cm2 current density in 0.5 V at 180 °C at dry condition. The above results indicated that the PFT4 nanocomposite membranes could be utilized as proton exchange membranes for high-temperature fuel cells. 相似文献
154.
Morteza Mohseni 《General Relativity and Gravitation》2010,42(7):1727-1737
An energy-momentum tensor for general relativistic spinning fluids compatible with Tulczyjew-type supplementary condition
is derived from the variation of a general Lagrangian with unspecified explicit form. This tensor is the sum of a term containing
the Belinfante–Rosenfeld tensor and a modified perfect-fluid energy-momentum tensor in which the four-velocity is replaced
by a unit four-vector in the direction of fluid momentum. The equations of motion are obtained and it is shown that they admit
a Friedmann–Robertson–Walker space–time as a solution. 相似文献
155.
Hussein YH Anderson N Lian TT Abdou IM Strekowski L Timoshchuk VA Vaghefi MM Netzel TL 《The journal of physical chemistry. A》2006,110(13):4320-4328
The goal of this work is to produce high yields of long-lived AQ(*-)/dA(*+) charge transfer (CT) excited states (or photoproducts). This goal fits within a larger context of trying generally to produce high yields of long-lived CT excited states within DNA nucleoside conjugates that can be incorporated into DNA duplexes. Depending upon the energetics of the anthraquinonyl (AQ) (3)(pi,pi) state as well as the reduction potentials of the subunits in particular anthraquinonyl-adenine conjugates, CT quenching of the AQ (3)(pi,pi*) state may or may not occur in polar organic solvents. In MeOH, bis(3',5'-O-acetyl)-N(6)-(anthraquinone-2-carbonyl)-2'-deoxyadenosine (AQCOdA) behaves as intended and forms a (3)(AQ(*-)/dA(*+)) CT state with a lifetime of 3 ns. However, in nonpolar THF the AQ(*-)/dA(*+) CT states of AQCOdA are too high in energy to be formed, and in DMSO a (1)(AQ(*-)/dA(*+)) CT state is formed but lives only 6 ps. Although the lowest energy excited state for AQCOdA in MeOH is a (3)(AQ(*-)/dA(*+)) CT state, for N(6)-(anthraquinone-2-methylenyl)-2'-deoxyadenosine (AQMedA) in the same solvent it is a (3)(pi,pi*) state. Changing the linking carbonyl in AQCOdA to methylene in AQMedA makes the anthraquinonyl subunit harder to reduce by 166 mV. This raises the energy of the (3)(AQ(*-)/dA(*+)) CT state above that of the (3)(pi,pi*) in AQMedA. The conclusion is that anthraquinonyl-dA conjugates will not have lowest energy AQ(*-)/dA(*+) CT states in polar organic solvents unless the anthraquinonyl subunit is also substituted with an electron-withdrawing group that raises the AQ-subunit's reduction potential above that of AQ. A key finding in this work is that the lifetime of the (3)(AQ(*-)/dA(*+)) CT excited state (ca. 3 ns) is ca. 500-times longer than that of the corresponding (1)(AQ(*-)/dA(*+)) CT excited state (ca. 6 ps).' 相似文献
156.
Mohammad Hossein Habibi Morteza Montazerozohori Ross W. Harrington 《Journal of fluorine chemistry》2006,127(6):769-773
The Schiff base compound, N,N′-bis(trifluoromethylbenzylidene)ethylenediamine (C18H14F6N2) (1), CF3C6H4CHNCH2CH2NCHC6H4CF3 has been synthesized by adding a solution of ethylenediammine (en), 0.1 mmol in chloroform to 4-(trifluoromethyl)-benzaldehyde, CF3C6H4CHO (0.2 mmol) and the product was crystallized in ethanol with the mp, 109.2 °C and 75% yield. The crystal structure was investigated by a single-crystal X-ray diffraction study at 150 K. The compound crystallizes in monoclinic space group, P21/c with a = 9.295(3), b = 5.976(5), c = 15.204(9) Å and α = 90°, β = 96.56(5)° and γ = 90°. The crystal structure is stabilized by intermolecular CH · · · F hydrogen bonds. The asymmetric unit contains only one-half of the molecule related to the center of symmetry coinciding with C(1)-C(1′) and as a whole, the title molecule is in the staggered conformation. The phenyl rings and the CN imine bonds are co-planar. The infrared spectrum showed a sharp peak at 1640 cm−1 which is typical of the conjugated CN stretching and strong peaks at 800-1400 cm−1 regions are due to the C-C and C-H stretching modes. Electronic absorption spectra exhibits strong absorption in the UV region (240 nm wavelength) which have been ascribed to , and electronic transitions. The 1H NMR spectra showed three distinct peaks at 2.5, 7.8 and 8.5 ppm which are assigned based on the splitting of resonance signals and are clearly confirmed by the X-ray molecular structure. The aromatic protons appear at about 7.8 ppm and the imine protons at 8.5 ppm. The sharp singlet at about 3.95 ppm is assigned to the CH2-CH2 protons. Mass spectra of the titled compound showed the molecular ion peak at m/e 372 (M+), and fragments at m/e 353 (M-F), 342 (M-2F), 200 (M-CF3C6H4CHN), 186 (M-CF3C6H4CHNCH2). 相似文献
157.
Behrooz Rezaie Mohammad Reza Jahed Motlagh Siavash Khorsandi Morteza Analoui 《Nonlinear Analysis: Real World Applications》2010,11(5):3842-3857
This paper carries out a Hopf bifurcation analysis on a model of Internet congestion control system for a network with arbitrary topology. The general form of the rate-based Kelly model for a multi-source multi-link network with a communication delay is considered. Assuming the communication delay as a bifurcation parameter, we find that when the delay parameter passes a critical value, a periodic solution bifurcates from the equilibrium point. The stability and direction of bifurcating periodic solutions are studied by using the center manifold theorem and the normal form theory. We simulate our model for a typical example to show the applicability of the approach. 相似文献
158.
In this work rank annihilation factor analysis (RAFA) is used to analyze difference spectra of kinetic‐spectrophotometric data. Annihilation of the contribution of one chemical component from the original data matrix is a general method in RAFA. However, sometimes RAFA is not suitable for studying rank deficient data such as kinetic‐spectrophotometric measurements. On the other hand, in order to apply RAFA for the determination of an analyte in an unknown sample, a standard two‐way matrix of the analyte with rank one should generally be available. This is not usually attainable for kinetic‐spectrophotometric monitoring of complexation reactions. Processes monitored by difference spectroscopy always have the spectrum of the initial stage subtracted from each spectrum in the data matrix. In this work we show that, for kinetic‐spectrophotometric data of complexation reactions, the spectrum of ligand (reactant) itself can be used as initial spectrum for subtraction. The obtained difference matrix of sample and that of analyte of interest will be full‐rank and rank 1, respectively. Therefore the system can be analyzed by RAFA. The proposed method was investigated with simulated data at the first stage. The method was then applied in the analysis of experimental kinetic‐spectrophotometric data of a complexation reactions of Co(II) and Ni(II) with chromogenic reagent 1‐(2‐pyridylazo) 2‐naphthol in order to do multi‐component determination of these ions in various real samples. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
159.
A simple, rapid, and efficient method, based on surfactant assisted dispersive liquid-liquid microextraction (SA-DLLME), followed by high performance liquid chromatography (HPLC) has been developed for the extraction and determination of chlorophenols as model compounds in environmental water samples. A conventional cationic surfactant called cethyltrimethyl ammonium bromide (CTAB) was used as a disperser agent in the proposed approach. Thirty-five microliter of 1-octanol as an extraction solvent was injected rapidly into 11 mL aqueous sample containing 0.09 mmol L−1 of CTAB, the mixture was then shaken for 3 min to disperse the organic phase. Having the extraction procedure been completed, the mixture was centrifuged and 20 μL of collected phase was injected into HPLC for subsequent analysis. Some parameters such as the type and volume of the extraction solvent, the type and concentration of surfactant, pH, ionic strength, shaking time, extraction temperature and centrifugation time were optimized. The preconcentration factors (PFs) in a range of 187-353 were obtained under the optimum conditions. The linear range, detection limit (S/N = 3), and precision (n = 5) were 0.2-200, 0.1 μg L−1, and 4.7-6.9%, respectively. Tap water, sea water and mineral water samples were successfully analyzed for the existence of chlorophenols using the proposed method. 相似文献
160.