全文获取类型
收费全文 | 263篇 |
免费 | 6篇 |
专业分类
化学 | 140篇 |
晶体学 | 5篇 |
力学 | 34篇 |
数学 | 41篇 |
物理学 | 49篇 |
出版年
2023年 | 1篇 |
2022年 | 9篇 |
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 17篇 |
2015年 | 6篇 |
2014年 | 15篇 |
2013年 | 30篇 |
2012年 | 27篇 |
2011年 | 19篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 8篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 2篇 |
2003年 | 7篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1981年 | 2篇 |
排序方式: 共有269条查询结果,搜索用时 15 毫秒
81.
82.
Mehrdad Seifali Abbas-Abadi Mehdi Nekoomanesh Haghighi Hamid Yeganeh Babak Bozorgi 《Journal of Thermal Analysis and Calorimetry》2013,114(3):1333-1339
The powder of EX5 grade of high density polyethylene—without any additives—manufactured by Amirkabir petrochemical company was separated by shaker equipment. The separated powder of average diameter ~25, ~62.5, ~87.5, ~112.5, ~137.5, ~175 and the particles >200 μm was tested by a thermogravimetric (TG) analysis instrument in nitrogen atmosphere and heating rates of 10, 20, and 30 °C min?1. In addition, the separated powders were analyzed by a melt flow index (MFI) instrument, and the viscosity average molecular mass (M v) of the powders was tested by a viscometer. Kinetic evaluations were performed by Friedman and Kissinger analysis methods and apparent activation energy for the overall degradation of the powders was determined. The effects of molecular mass, MFI, MFR, and particle size on the degradation TG curve, derivative thermogravimetry curve breadth, and activation energy of thermal degradation were considered. The results showed that the M v of EX5 pipe grade produced by two serial reactors is increased by increasing of the particle size and, MFI is decreased with a little deviation by particle size increasing. The particle size has no obvious effect on the melt flow rate (MFR), and MFR as function of molecular mass distribution does not change very much. The results showed that the powder with bigger particles and higher molecular mass moderately increases the activation energy and shifts the degradation curve to the higher temperatures. 相似文献
83.
Mehrdad Pourayoubi Maryam Toghraee Ray J. Butcher Vladimir Divjakovic 《Structural chemistry》2013,24(4):1135-1144
The phosphoryl donor ligand (tBuNH)3PO (PO) was used for preparation of new tin(IV), Cl2Ph2Sn(PO)2 (1), and iron(III), Fe(PO)2(NO3)3 (2), complexes. These complexes are the first examples of using a phosphoric triamide containing a secondary nitrogen atom, [RNH]3P(O), for preparation of an organotin(IV) complex of the type ([RNH]3P(O))2X2Ph2Sn, X = halide, and an iron(III) complex. In 1, the Sn coordination geometry is octahedral with the pair of similar ligands in a trans orientation. The Fe center in 2 is seven-coordinated with the two phosphoramide ligands in a trans fashion, too. This article also reviews the structures of analogous complexes with phosphoric triamide ligands, deposited in the CSD, aiming to classify hydrogen bond patterns in this category of compounds. Moreover, it is tried to find a relationship between the H-bond patterns in complexes and the related free ligands. 相似文献
84.
In this paper, we have used the finite-difference time-domain (FDTD) method to analyze the optical pulse propagation in a nonlinear, one-dimensional photonic crystal (1DPC). Hyperbolic secant pulses with various carrier wavelengths are utilized in this study. In a nonlinear regime, a 1DPC introduces a photonic band-gap whose central wavelength and width depend on the input pulse intensity. In the present work, three different cases are considered. These correspond to the carrier wavelengths of the incident pulses being out of, near to, and partially in the band-gap. For each case, the effect of nonlinearity on pulse propagation is investigated. Also, we have analyzed the two-frequency regime, in which each of the two pulses has a different carrier frequency (wavelength). This kind of study can be done directly with FDTD without any further computational burden but it is somewhat complicated using nonlinear coupled-mode equations (NLCME) and nonlinear Schrödinger equation (NLSE), which require separate treatments for each carrier wavelength. 相似文献
85.
Zarghi A Hajimahdi Z Mohebbi S Rashidi H Mozaffari S Sarraf S Faizi M Tabatabaee SA Shafiee A 《Chemical & pharmaceutical bulletin》2008,56(4):509-512
A new series of 2-substituted-5-[2-(2-halobenzyloxy)phenyl]-1,3,4-oxadiazoles was designed and synthesized as anticonvulsant agents. Electroshock and pentylenetetrazole-induced lethal convulsion tests showed that the introduction of an amino group at position 2 of 1,3,4-oxadiazole ring and a fluoro substituent at ortho position of benzyloxy moiety had the best anticonvulsant activity. Our results showed that this effect is mediated through benzodiazepine receptors mechanism. 相似文献
86.
Arsou Arimi Mehrdad Farhadian Ali Reza Solaimany Nazar Maryam Homayoonfal 《Research on Chemical Intermediates》2016,42(5):4021-4040
In the current study, a nanophotocatalyst doped with of TiO2 and Fe2O3 nanoparticles supported on Iranian clinoptilolite was synthesized and characterized by XRD, XRF, SEM, and EDX analyses. The results suggested the successful loading of TiO2 and Fe2O3 nanoparticles onto the surface of clinoptilolite. The SEM images confirmed the average size of nanoparticles deposited on zeolite, which was about 20–40 nm. Furthermore, application of the synthesized photocatalyst in photocatalytic degradation of Acid Black 172 dye was studied using the Taguchi method and the chosen parameters were as follows: pH (2–7), dye concentration (50–200 mg/l), irradiation time (30–120 min), and catalyst dosage (0.5–1.5 g/l). The results indicate that dye concentration, pH, and irradiation time are respectively the most effective factors in these experiments while with the minimum dosage of the catalyst (0.5 g/l), up to 90 % removal efficiency could be achieved. The optimum value for each parameter was pH = 2, dye concentration = 50 mg/l, catalyst dosage = 1 g/l and irradiation time = 60 min, and the dye removal efficiency reached up to 100 % at these optimal conditions. Furthermore, after five-times recycling and reusing the catalyst, the efficiency of the photocatalytic degradation was reduced from 91.5 to 65.9 %, which is still an acceptable value. 相似文献
87.
Effect of nano‐modified SiO2/Al2O3 mixed‐matrix micro‐composite fillers on thermal,mechanical, and tribological properties of epoxy polymers
下载免费PDF全文
![点击此处可从《先进技术聚合物》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sadasivan S. Vaisakh Abdul Azeez Peer Mohammed Mehrdad Hassanzadeh Jean F. Tortorici Renaud Metz Solaiappan Ananthakumar 《先进技术聚合物》2016,27(7):905-914
Thermo‐mechanically durable industrial polymer nanocomposites have great demand as structural components. In this work, highly competent filler design is processed via nano‐modified of micronic SiO2/Al2O3 particulate ceramics and studied its influence on the rheology, glass transition temperature, composite microstructure, thermal conductivity, mechanical strength, micro hardness, and tribology properties. Composites were fabricated with different proportions of nano‐modified micro‐composite fillers in epoxy matrix at as much possible filler loadings. Results revealed that nano‐modified SiO2/Al2O3 micro‐composite fillers enhanced inter‐particle network and offer benefits like homogeneous microstructures and increased thermal conductivity. Epoxy composites attained thermal conductivity of 0.8 W/mK at 46% filler loading. Mechanical strength and bulk hardness were reached to higher values on the incorporation of nano‐modified fillers. Tribology study revealed an increased specific wear rate and decreased friction coefficient in such fillers. The study is significant in a way that the design of nano‐modified mixed‐matrix micro‐composite fillers are effective where a high loading is much easier, which is critical for achieving desired thermal and mechanical properties for any engineering applications. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
88.
89.
90.
Particle swarm optimization (PSO) is an evolutionary, easy-to-implement technique to design optical diffraction gratings. Design of reflection and transmission guided-mode resonance (GMR) grating filters using PSO is reported. The spectra of the designed filters are in good agreement with the design targets in a reasonable computation time. Also, filters are designed with a genetic algorithm (GA) and the results obtained by the GA and PSO are compared. 相似文献