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排序方式: 共有285条查询结果,搜索用时 15 毫秒
1.
Mackenzie Kelley Nastaran Abdol Parviz Soroushian Kristina Keating Anagi M. Balachandra Tyler Meldrum 《Journal of polymer science. Part A, Polymer chemistry》2020,58(4):616-623
Adhesively bonded joints using epoxy are widely used in aircraft and aerospace structures. Quality control and defect detection during epoxy curing in such applications is critical. We used single-sided nuclear magnetic resonance (NMR) to nondestructively probe and spatially resolve the change in the characteristic NMR relaxation time (T2) of epoxies during curing on a substrate. Time-dependent T2 values were fit to a Weibull function to model temporal changes in the NMR measurables. Our results demonstrate that the reduction in molecular mobility of various epoxy/curing agent mixtures occurs more rapidly at the interface than in the bulk. Further use of single-sided NMR to acquire spatially resolved T2 data will provide a route for elucidatory epoxy curing studies. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 616–623 相似文献
2.
Gholamreza Vaghar-Lahijani Mohammad Saber-Tehrani Parviz Aberoomand-Azar Mojtaba Soleimani 《Journal of Analytical Chemistry》2018,73(2):145-151
In this study, an effective method of ultrasound-assisted ionic liquid based dispersive liquid–liquid microextraction (UA?IL?DLLME) coupled with HPLC was applied for extraction and determination of two antidepressant drugs: venlafaxine hydrochloride and amitriptyline hydrochloride from human plasma samples. Three ionic liquids were studied: 1-butyl-3-methyl imidazolium hexafluorophosphate, 1-hexyl-3- methyl imidazolium hexa-fluoro-phosphate, and 1-octyl-3-methyl imidazolium hexafluorophosphate [C8MIM][PF6]. Various factors affect the stages and efficiency of extraction, some of which are pH of sample solution, type and volume of ionic liquid, the time of ultrasonication, centrifuging time and rate, and the ionic strength of solution. In this research, optimum conditions were obtained as 55 μL of [C8MIM][PF6] selected as ionic liquid, pH 11, 2% NaCl, 4 min ultrasonication and 5 min centrifuging at 3500 rpm. Under the optimized conditions, the linearity was obtained in the range of 0.2 to 250 μg/L. The limits of detection were 0.5 μg/L for venlafaxine and 0.8 μg/L for amitriptyline. Pre-concentration factors were 1.3 × 103 for venlafaxine and 1.2 × 103 for amitriptyline. The UA?IL?DLLME method coupled with HPLC was successfully used for the determination of venlafaxine and amitriptyline spiked into the real samples of human plasma. 相似文献
3.
Foroutan-Nejad C Shahbazian S Rashidi-Ranjbar P 《Physical chemistry chemical physics : PCCP》2011,13(10):4576-4582
The nature of bonding and aromaticity of Ti(3)(CO)(3), a mill-shaped metal-carbonyl complex, is studied carefully. A unique bonding mechanism between metal and carbonyl groups is found in this species. Ti(3)(CO)(3) is an example of a metal-carbonyl complex with prominent metal to carbonyl donation. Moreover, it is proven that not only is Ti(3)(CO)(3) not an antiaromatic complex but also it is the first synthesized example of d-block, σ+π aromatic species. A quick survey among the first row of transition metals in the periodic table shows that other local minima with similar structures and aromaticity are present and Ti(3)(CO)(3) is the first synthesized species of an unknown family. 相似文献
4.
Siavash Riahi Mohammad Reza Ganjali Maryam Hariri Shaghayegh Abdolahzadeh Parviz Norouzi 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(1):253-258
In this paper, a sensitive, easy, efficient, and suitable method for the calculation of Kf values of complexation between one derivative of Dansyl chloride [5-(dimethylamino) naphthalene-1-sulfonyl 4-phenylsemicarbazide] (DMNP) and Lanthanide(III) (Ln) ions is proposed, using both spectrofluorometric and spectrophotometric methods. Determination of Kf showed that DMNP was mostly selective towards the erbium (III) ion. The validity of the method was also confirmed calculating the Stern–Volmer fluorescence quenching constants (Ksv) that resulted in the same consequence, obtained by calculating the Kf of complexation values. In addition, the UV–vis spectroscopy was applied for the determination of Kf only for the Ln ions that had interactions with DMNP. Finally, the DFT studies were done on Er3+ and the DMNP complex for distinguishing the active sites and estimating the pair wise interaction energy. It can be concluded that this derivative of Dansyl chloride with inherent high fluorescence intensity is a suitable reagent for the selective determination of the Er3+ ion which can be used in constructing selective Er3+ sensors. 相似文献
5.
Norouzi Parviz Ganjali Mohammad Reza Qomi Mahnaz Nemati Kharat Ali Zamani Hassan Ali 《中国化学》2010,28(7):1133-1139
A continuous cyclic voltammetric study of letrozole at gold microelectrode was carried out. The drug in phosphate buffer (pH 2.0) is adsorbed at ?200 mV, giving rise to change in the current of well‐defined oxidation peak of gold in the flow injection system. The proposed detection method has some of advantages, the greatest of which are as follows: first, it is no more necessary to remove oxygen from the analyte solution and second, this is a very fast and appropriate technique for determination of the drug compound in a wide variety of chromatographic analysis methods. Signal‐to‐noise ratio has significantly increased by application of discrete Fast Fourier Transform (FFT) method, background subtraction and two‐dimensional integration of the electrode response over a selected potential range and time window. Also in this work some parameters such as sweep rate, eluent pH, and accumulation time and potential were optimized. The linear concentration range was of 1.0×10?7?1.0×10?10 mol/L (r=0.9975) with a limit of detection and quantitation 0.08 nmol/L and 0.15 nmol/L, respectively. The method has the requisite accuracy, sensitivity, precision and selectivity to assay letrozol in tablets. The influences of pH of eluent, accumulation potential, sweep rate, and accumulation time on the determination of the letrozol were considered. 相似文献
6.
Dispersive liquid-liquid microextraction (DLLME) combined with spectrofluorimetry was applied to the extraction, pre-concentration and analysis of thiamine (vitamin B1). The procedure is based on (a) the oxidation of thiamine with ferricyanide to form fluorescent thiochrome (TC), (b) the trapping of TC into a microextraction solvent, and (c) spectrofluorometric determination. Microextraction solvent and disperser solvent are directly injected into an aqueous solution containing TC. After centrifuging, phase separation is performed by sedimenting the fine droplets of the microextraction solvent on the bottom of a test tube. The settled phase is transferred into a fluorometer for the determination of thiamine at excitation/emission wavelengths of 375/438 nm. Under the optimized experimental conditions, the method provides a linear dynamic range of 0.2–100 ng mL?1, a detection limit of 0.06 ng mL?1, and a relative standard deviation of 3.0%. The method was successfully applied to pharmaceutical formulations and human urine. The results were validated by recovery test and by comparison with other methods, and were found to be highly satisfactory. 相似文献
7.
Seyyed Javad Sabounchei Khadijeh Badpa Mehdi Bayat Roya Karamian Fatemeh Ghasemlou Robert W. Gable Parviz Gohari Derakhshandeh Kristof Van Hecke 《应用有机金属化学》2019,33(3)
The reaction of α‐keto‐stabilized diphosphine ylides [Ph2P(CH2)nPPh2═C(H)C(O)C6H4‐p‐CN] (n = 1 (Y1); n = 2 (Y2)) with dibromo(1,5‐cyclooctadiene) palladium(II)/platinum(II) complexes, [Pd/PtBr2(cod)], in equimolar ratio gave the new cyclometalated Pd(II) and Pt(II) complexes [Br2Pd(κ2‐Y1)] ( 1 ), [Br2Pt(κ2‐Y1)] ( 2 ), [Br2Pd(κ2‐Y2)] ( 3 ) and [Br2Pt(κ2‐Y2)] ( 4 ). These compounds were screened in a search for novel antibacterial agents and characterized successfully using Fourier transfer infrared and NMR (1H, 13C and 31P) spectroscopic methods. Also, the structures of complexes 1 and 2 were characterized using X‐ray crystallography. The results showed that the P,C‐chelated complexes 1 and 2 have structures consisting of five‐membered rings, while 3 and 4 have six‐membered rings, formed by coordination of the ligand through the phosphine group and the ylidic carbon atom to the metal centre. Also, a theoretical study of the structures of complexes 1 – 4 was conducted at the BP86/def2‐SVP level of theory. The nature of metal–ligand bonds in the complexes was investigated using energy decomposition analyses (EDA) and extended transition state combined with natural orbitals for chemical valence analyses. The results of EDA confirmed that the main portions of ΔEint, about 57–58%, in the complexes are allocated to ΔEelstat. 相似文献
8.
Mohammad T. Baei Ali Varasteh Moradi Parviz Torabi Masoumeh Moghimi 《Monatshefte für Chemie / Chemical Monthly》2012,18(3):37-41
Abstract
The behavior of H2O2 adsorbed inside a [4,4] armchair boron phosphide nanotube (BPNT) was studied by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using the Gaussian 03 suite of programs. We present the nature of the H2O2 interactions inside the nanotube. The interaction between the guest species (H2O2) and the nanotube and the dipole moments of the different geometries are discussed. The results show that the binding energies and the dipole moments of the nanotube depend on the orientation and location of the H2O2 inside the tube. Among the parallel orientation (AT) and perpendicular orientations (PTA and PTP), the PTA and PTP geometries of the H2O2 are unstable whereas the AT-state geometries show stabilization of the guest species inside the BPNT. For AT orientations, the value of the dihedral angle of the H2O2 trapped inside the BPNT in the most stable conformation displays a notable change with respect to free H2O2. Also, with change of tube type, more efficient binding could not be achieved, and only the orientation and location of the H2O2 inside the tube play an important role in determining the binding energy. The polarization of the BPNT in the presence of the guest species in the PT state is higher than that of the AT state. Adsorption of H2O2 in the AT state slightly reduces the energy gap of the pristine BPNTs and slightly increases their electrical conductance. 相似文献9.
Mahboobeh Behnam Dehkordi Majid M. Heravi Parviz Khosrofar Ahmad Ziafat Mitra Ghassemzadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2595-2598
Hexamethylenetetramine-bromine supported onto[3pc] silica gel rapidly converts trimethylsilyl ethers to their corresponding carbonyl compounds under microwave irradiation in solventless system. 相似文献
10.
Hu Zhang ** Sally Lamping Parviz Ayazi ShamlouAdvanced Biochemical Engineering Centre University College London Torrington Place London WCE JE 《高等学校化学研究》2002,18(2):113-116
IntroductionShakeflasksareusedroutinelyinthepharmaceu tical,biochemicalandmedicalfieldsforcellgrowthculture ,mediascreeningandforcellexpansion .Shakeflaskfermentationrequiresrelativelysmallamountsofmaterial,typicallybetween 5 0and 5 0 0mL ,andreliesonahorizon… 相似文献