全文获取类型
收费全文 | 176篇 |
免费 | 12篇 |
国内免费 | 2篇 |
专业分类
化学 | 127篇 |
晶体学 | 5篇 |
力学 | 9篇 |
数学 | 18篇 |
物理学 | 31篇 |
出版年
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 8篇 |
2019年 | 15篇 |
2018年 | 13篇 |
2017年 | 17篇 |
2016年 | 10篇 |
2015年 | 5篇 |
2014年 | 14篇 |
2013年 | 19篇 |
2012年 | 14篇 |
2011年 | 14篇 |
2010年 | 11篇 |
2009年 | 15篇 |
2008年 | 5篇 |
2007年 | 2篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2001年 | 2篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有190条查询结果,搜索用时 850 毫秒
131.
Nafiseh Moazzen Mohammadreza Khanmohammadi Amir Bagheri Garmarudi Maryam Kazemipour Mehdi Ansari Dogaheh 《Journal of the Iranian Chemical Society》2017,14(3):671-680
Fourier transform infrared spectroscopy coupled with chemometrics was employed to detect packaging polylactic acid-based biocomposite samples adulterated with polypropylene (PP) 30–45% and linear low-density polyethylene 2–10%. Principal component analysis, soft independent modeling of class analogy (SIMCA) and partial least square discriminate analysis (PLS-DA) chemometric techniques were utilized to classify samples in different classes. Totally, 362 samples were modeled in three different classes (two adulterated and one non-adulterated). The obtained results revealed that PLS-DA is the most suitable chemometric approach for prediction of probable adulteration in biocomposite samples with reliable specificity and selectivity. It could provide 99% correct class prediction rate between non-adulterated biocomposite samples and adulterated ones, while SIMCA methods provided 73.33% prediction accuracy in classification. 相似文献
132.
Analysis of unsteady stagnation‐point flow over a shrinking sheet and solving the equation with rational Chebyshev functions
下载免费PDF全文
![点击此处可从《Mathematical Methods in the Applied Sciences》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mohammadreza Foroutan Ali Ebadian Shahram Najafzadeh 《Mathematical Methods in the Applied Sciences》2017,40(7):2610-2622
This paper investigates the nonlinear boundary value problem, resulting from the exact reduction of the Navier–Stokes equations for unsteady laminar boundary layer flow caused by a stretching surface in a quiescent viscous incompressible fluid. We prove existence of solutions for all values of the relevant parameters and provide unique results in the case of a monotonic solution. The results are obtained using a topological shooting argument, which varies a parameter related to the axial shear stress. To solve this equation, a numerical method is proposed based on a rational Chebyshev functions spectral method. Using the operational matrices of derivative, we reduced the problem to a set of algebraic equations. We also compare this work with some other numerical results and present a solution that proves to be highly accurate. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
133.
Mohammadreza Jooyandeh Brendan D. McKay Patric R. J. Östergård Ville H. Pettersson Carol T. Zamfirescu 《Journal of Graph Theory》2017,84(2):121-133
A graph is hypohamiltonian if it is not Hamiltonian, but the deletion of any single vertex gives a Hamiltonian graph. Until now, the smallest known planar hypohamiltonian graph had 42 vertices, a result due to Araya and Wiener. That result is here improved upon by 25 planar hypohamiltonian graphs of order 40, which are found through computer‐aided generation of certain families of planar graphs with girth 4 and a fixed number of 4‐faces. It is further shown that planar hypohamiltonian graphs exist for all orders greater than or equal to 42. If Hamiltonian cycles are replaced by Hamiltonian paths throughout the definition of hypohamiltonian graphs, we get the definition of hypotraceable graphs. It is shown that there is a planar hypotraceable graph of order 154 and of all orders greater than or equal to 156. We also show that the smallest planar hypohamiltonian graph of girth 5 has 45 vertices. 相似文献
134.
Tahereh Harsij Sani Mohammadreza Hadjmohammadi Mohammad Hossein Fatemi 《Journal of separation science》2020,43(7):1224-1231
Extraction and determination of three flavonoids (morin, quercetin, and kaempferol) were performed by dispersive magnetic solid phase extraction based on mixed hemi/ad‐micelles and high‐performance liquid chromatography with UV detection. The Fe3O4/SiO2 nanoparticles were synthesized and characterized by X‐ray diffraction, FTIR, scanning electron microscopy, and thermogravimetric analysis. Fe3O4/SiO2 nanoparticles coated with mixed hemi/ad‐micelles cetyltrimethyl ammonium bromide was applied as a sorbent and used for extraction of flavonoids. Effective parameters on the extraction recovery such as amount of magnetic nano particles, volume of cetyltrimethyl ammonium bromide solution with specific concentration, pH of sample solution, adsorption equilibrium time, volume of desorption solvent, and desorption times were evaluated and optimized using fractional factorial design and central composite design. Under the optimum condition limit of detection and linearity were 0.83, 2.7–500.0 for morin, 0.18, 0.7–500.0 for quercetin and, 0.37, 1.3–500.0 µg/L for kaempferol. The extraction recovery with relative standard deviation were 97.88, 1.94 for morin, 95.77, 0.80 for quercetin, and 93.35, 1.45 for kaempferol. The proposed method was applied for simultaneous extraction and determination of flavonoids in several fruit juices and vegetable samples. 相似文献
135.
Mohammadreza Mohammadi Nilash Sajad Avar Fahimeh Mirzaei Ali Reza Fakhari Abbas Rezaee Shirin‐abadi 《Journal of separation science》2020,43(5):920-928
The present study deals with the synthesis and electrospining of a new terpolymer nanofiber in order to determine the amount of diazinon and chlorpyrifos in water and fruit juice samples. The synthesized terpolymer and the prepared nanofiber were characterized using 1H NMR spectroscopy, FTIR spectroscopy, scanning electron microscopy, and gel permeation chromatography. The performance of terpolymer nanofiber, prepared as a sorbent for micro solid phase extraction was investigated for the extraction of diazinon and chlorpyrifos from aquaeous media. Then, the target analytes were desorbed from the coating with an organic solvent and analyzed by gas chromatography with flame ionization detector. Extraction efficiencies were significant (>90%) under the optimum condition. The proposed method also demonstrated good linear dynamic ranges for diazinon and chlorpyrifos (3–250 and 5–200 µg/L), and low limit of detections (0.5 and 0.7 µg/L) respectively. Moreover, under optimum condition for extraction of diazinon and chlorpyrifos, square of correlation coefficients (R2) of 0.9978 and 0.9953 and relative standard deviations of 4.6 and 5.1% were achieved, respectively. The recoveries for diazinon and chlorpyrifos were in the range of 85–97%. 相似文献
136.
Mir Mohammad Alavi Nikje Mohammadreza Khanmohammad Amir Bagheri Garmarudi Keyvan Ghasemi 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(1):116-120
Epoxy based nanocomposite samples containing SiO2 nanoparticles (0.0–3.0 %w) were prepared for physical and mechanical evaluation. Some thermomechanical and physical properties of samples were investigated using dynamic mechanical analysis (DMA), tensile strength, hardness and abrasion tests. The main aim of experimentation was to realize the optimum amount of nano-SiO2 which would demonstrate the best improving effect on mechanical and physical properties of nanocomposite samples and finding how significant a factor is for improving in physical and mechanical properties. Analysis of variance (ANOVA) was applied for optimization of SiO2 content in epoxy based nanocomposites. 相似文献
137.
S. Salehzadeh M. Khalaj S. Dehghanpour A. Mahmoudi 《Journal of the Iranian Chemical Society》2013,10(5):921-928
From the reaction of ZnCl2 and HgCl2 metal salts with (E)-4-chloro-N-(pyridine-2-ylmethylene)benzeneamine (L) in methanol solution, two binuclear Schiff base complexes were prepared. Both complexes were characterized by elemental analysis, UV–Vis, and IR spectrophotometry. X-ray crystal structure analysis showed that metal ion in the resulting centrosymmetric dinuclear ML2Cl4 complexes is in a distorted trigonal bipyramidal and a distorted square pyramidal coordination environment in the case of Zn(II) and Hg(II) metal ions, respectively. Three types of reaction between MCl2 salts and ligand L producing three different types of products—ML2 2+, MLCl2, and M2L2Cl4—were simulated in both the gas phase and solution. The gas phase calculations at DFT (B3LYP) level of theory using SDD, CEP-121G, and LanL2DZ basis sets showed that the binuclear M2L2Cl4 complexes are more stable than corresponding mononuclear MLCl2 complexes. Furthermore, both the gas phase and solution studies showed that the formation of M2L2Cl4 complexes from the metal cations, chloride anion, and ligand molecule is energetically more favored than that of MLCl2 and ML2 2+ complexes. 相似文献
138.
Saeed Dehghanpour Maryam Rezazadeh Ali Mahmoudi Amir H. Mahmoudkhani Mehdi Khalaj Khadijeh Jahani 《Journal of the Iranian Chemical Society》2014,11(3):751-757
The new copper(II) tetraphosphonate, [Cu3(HO3PCH2)2N–CH2C6H4CH2–N(CH2PO3H)2)(H2O)4] n (1) was hydrothermally synthesized from the reaction of Cu(NO3)2 and (H2O3PCH2)2N–CH2C6H4CH2–N(CH2PO3H2)2, (H8L). Compound 1 was structurally characterized by means of X-ray single crystal diffraction. The structure of 1 showed a 3D structure constructed from two types of Cu(II) and chelating and bridging modes of (HO3PCH2)2N–CH2C6H4CH2–N(CH2PO3H)2, and features a (44.610.8) topological network. The 3D compound is further stabilized by hydrogen bonds. UV–Vis diffuse reflectance and infrared spectroscopy as well as elemental analysis of compound 1 are also presented. 相似文献
139.
S. Salehzadeh M. Khalaj S. Dehghanpour M. Bayat 《Journal of the Iranian Chemical Society》2014,11(1):9-16
A new binuclear mercury(I) complex, [Hg2(L)2(NO3)2] (L = (4-nitrophenyl)pyridin-2-ylmethyleneamine), 1, has been synthesized and characterized by CHN analyses, IR, UV–vis spectroscopy and X-ray crystal structure analysis. The complex contains a metal–metal bonded core, [Hg–Hg]2+, in which a single bidentate imine ligand is coordinated to each mercury atom. The Hg atoms have an additional interaction with the oxygen atom of the NO3 ? ion. Theoretical studies show that the interaction energy between the two {Hg(L)NO3} fragments is about 45–59 kcal/mol depending on the level of calculation. The Mayer-Mulliken and Wiberg bond indices (WBI) for Hg–Hg bond at different levels of theory are about 0.75–0.88 and 0.60–0.70, respectively, and are significantly larger than that for Hg–N and Hg–O bonds. The NBO calculations by using different methods and basis sets also show that the S character in Hg–Hg bond is very large (94.65–97.81 %). All above data for this complex are compared with those for linear Hg2X2 (X = F,Cl, Br, I, Ph) complexes. Interestingly, the bond order for Hg–Hg bond in complex 1 is comparable with that for Hg2F2 and larger than those in above linear complexes. This is consistent with the experimental data indicating that the Hg–Hg bond in 1 is shorter than that in all above complexes, except Hg2F2. 相似文献
140.
Seyed Milad Vahabi Mojtaba Shamsaie Zafarghandi Mohammadreza Ghasemi Anita Alipoor Arjang Shahvar 《Journal of Radioanalytical and Nuclear Chemistry》2014,301(1):91-96
Extrapolation chamber is the only primary standard dosimeter for beta radiation. With the aim to test new configurations and materials using easily-available and low-cost materials and fulfill the need of a chamber for scientific metrological purposes, in this paper the prototype of an extrapolation chamber has been built and its performance has been investigated in the beta radiation field of 90Sr+90Y. The main differences between the chamber and commercially available chambers are the geometry, constituent material and configuration. The obtained results were compared with those of the calibration certificate of the source and an agreement within 4 % was verified. The depth-dose curve was also obtained and compared with the curve published in ISO 6980, showing a good agreement. Moreover, Monte Carlo simulation was undertaken using MCNP4C code and the relative difference of 0.3 % was observed compared to the experiment. All of the results proved the suitability of the chamber in the beta radiation field of 90Sr+90Y. 相似文献