全文获取类型
| 收费全文 | 320篇 |
| 免费 | 6篇 |
专业分类
| 化学 | 212篇 |
| 晶体学 | 5篇 |
| 力学 | 28篇 |
| 数学 | 27篇 |
| 物理学 | 54篇 |
出版年
| 2025年 | 1篇 |
| 2024年 | 11篇 |
| 2023年 | 8篇 |
| 2022年 | 15篇 |
| 2021年 | 26篇 |
| 2020年 | 13篇 |
| 2019年 | 16篇 |
| 2018年 | 12篇 |
| 2017年 | 7篇 |
| 2016年 | 13篇 |
| 2015年 | 11篇 |
| 2014年 | 15篇 |
| 2013年 | 22篇 |
| 2012年 | 28篇 |
| 2011年 | 15篇 |
| 2010年 | 11篇 |
| 2009年 | 6篇 |
| 2008年 | 10篇 |
| 2007年 | 9篇 |
| 2006年 | 7篇 |
| 2005年 | 6篇 |
| 2004年 | 11篇 |
| 2003年 | 4篇 |
| 2002年 | 9篇 |
| 2001年 | 6篇 |
| 2000年 | 2篇 |
| 1999年 | 3篇 |
| 1998年 | 1篇 |
| 1997年 | 1篇 |
| 1996年 | 4篇 |
| 1994年 | 7篇 |
| 1993年 | 3篇 |
| 1992年 | 1篇 |
| 1991年 | 1篇 |
| 1988年 | 1篇 |
| 1987年 | 2篇 |
| 1986年 | 1篇 |
| 1985年 | 3篇 |
| 1984年 | 1篇 |
| 1983年 | 1篇 |
| 1980年 | 1篇 |
| 1979年 | 1篇 |
排序方式： 共有326条查询结果，搜索用时 0 毫秒
51.
The effect of an externally applied electric field on the stability of a thin fluid film over an inclined porous plane is analyzed using linear and non-linear stability analysis in the long wave limit. The principle aim of this study is to illustrate the influence of electric field on the non-linear stability of a thin liquid layer flow down incline substrate when the plane is porous. The driving force for the instability under an electric field is an electrostatic force exerted on the free charges accumulated at the dividing interface. The coupled non-linear evolution equations for the local film thickness and the interfacial charge for two-dimensional disturbances are derived to analyze the effect of long-wave instabilities. The method of multiple scales is applied to obtain approximate solutions and analyze the stability criteria. Numerical simulations of this system of non-linear evolution equations are performed. It is found that the permeability parameter as well as the inclination of the plane plays a destabilizing role in the stability criteria, while the damping influence is observed for increasing of the electrical conductivity in both linear and non-linear behavior. 相似文献
52.
Enhancement of the surface properties of a material by means of laser radiation has been amply demonstrated previously. In this work a comparative study for the surface modification of nylon 6,6 has been conducted in order to vary the wettability characteristics using CO2 and excimer lasers. This was done by producing 50 μm spaced (with depths between 1 and 10 μm) trench-like patterns using various laser parameters such as varying the laser power for the CO2 laser and number of pulses for the excimer laser. Topographical changes were analysed using optical microscopy and white light interferometry which indicated that both laser systems can be implemented for modifying the topography of nylon 6,6. Variations in the surface chemistry were evaluated using energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analysis which showed that the O2 increased by up to 1.5 at% and decreased by up to 1.6 at% for the CO2 and F2 laser patterned samples, respectively. Modification of the wettability characteristics was quantified by measuring the advancing contact angle, which was found to increase in all instances for both laser systems. Emery paper roughened samples were also analysed in the same manner to determine that the topographical pattern played a major role in the wettability characteristics of nylon 6,6. From this, it is proposed that the increase in contact angle for the laser processed samples is due to a mixed intermediate state wetting regime owed to the periodic surface roughness brought about by the laser-induced trench-like topographical patterns. 相似文献
53.
A. Hamid Othman Zuriati Zakaria Seik Weng Ng 《Journal of chemical crystallography》1993,23(12):921-923
The title structure, which belongs to the triclinicP¯1 space group witha=13.901(4),b=10.732(1),c=10.570(8)Å=109.14(4),=96.17(4), =90.34(2)°, is refined toR=0.052 for 2985I3(I) reflections. The structure consists of a non-interacting 1,2,4,6-tetraphenylpyridinium and tetrahedral tetrabromoferrate (III) ions. 相似文献
54.
Ikram Dhouib Zakaria Elaoud Tahar Mhiri Abdelaziz Daoud 《Journal of chemical crystallography》2012,42(5):513-518
Abstract
The salt bis benzyl ammonium monohydrogentetraoxoarsenate(V) monohydrate [C6H5CH2NH3 +]2HAsO4 2−·H2O, M = 373.92, Triclinic, P−1. a = 6.514(1), b = 8.910(2), c = 15.061(3) ?, α = 99.26(2), β = 93.93(1), γ = 97.64(1)°, V = 851.5(3), Z = 2, D x = 1.460, λ (MoKα) = 0.71073 ?, μ = 0.99 mm−1, F(000) = 126, T = 20(2) °C, final R = 0.673 for 5488 unique reflections. Planes of HAsO4 2− alternate with planes of C6H5CH2NH3 + groups. The structure consists of infinite parallel two-dimensional planes built of mutually connected ions and water molecules by strong O–H···O and N–H···O hydrogen bonding. There are no contacts other than van der Waals interactions between the layers. Differential scanning calorimetry study on bis benzyl ammonium monohydrogentetraoxoarsenate(V) monohydrate was carried out. The infrared of polycrystalline samples of this compound have been recorded at room temperature. 相似文献55.
Rana M. El-Masry Hanan H. Kadry Azza T. Taher Sahar M. Abou-Seri 《Molecules (Basel, Switzerland)》2022,27(9)
The bioisosteres of 1,3,4-oxadiazoles and 1,3,4-thiadiazoles are well-known pharmacophores for many medicinally important drugs. Throughout the past 10 years, 1,3,4-oxa-/thiadiazole nuclei have been very attractive to researchers for drug design, synthesis, and the study of their potential activity towards a variety of diseases, including microbial and viral infections, cancer, diabetes, pain, and inflammation. This work is an up-to-date comparative study that identifies the differences between 1,3,4-thiadiazoles and 1,3,4-oxadiazoles concerning their methods of synthesis from different classes of starting compounds under various reaction conditions, as well as their biological activities and structure–activity relationship. 相似文献
56.
57.
Nur Farisya Shamsudin Qamar Uddin Ahmed Syed Mahmood Syed Adnan Ali Shah Alfi Khatib Sayeed Mukhtar Meshari A. Alsharif Humaira Parveen Zainul Amiruddin Zakaria 《Molecules (Basel, Switzerland)》2022,27(4)
According to the latest report released by the World Health Organization, bacterial resistance to well-known and widely available antibacterial drugs has become a significant and severe global health concern and a grim challenge to tackle in order to cure infections associated with multidrug-resistant pathogenic microorganisms efficiently. Consequently, various strategies have been orchestrated to cure the severe complications related to multidrug-resistant bacteria effectively. Some approaches involved the retardation of biofilm formation and multidrug-resistance pumps in bacteria as well as the discovery of new antimicrobial agents demonstrating different mechanisms of action. In this regard, natural products namely alkaloids, terpenoids, steroids, anthraquinone, flavonoids, saponins, tannins, etc., have been suggested to tackle the multidrug-resistant bacterial strains owing to their versatile pharmacological effects. Amongst these, flavonoids, also known as polyphenolic compounds, have been widely evaluated for their antibacterial property due to their tendency to retard the growth of a wide range of pathogenic microorganisms, including multidrug-resistant bacteria. The hydroxylation of C5, C7, C3′, and C4′; and geranylation or prenylation at C6 have been extensively studied to increase bacterial inhibition of flavonoids. On the other hand, methoxylation at C3′ and C5 has been reported to decrease flavonoids’ antibacterial action. Hence, the latest information on the antibacterial activity of flavonoids is summarized in this review, with particular attention to the structure–activity relationship of this broad class of natural compounds to discover safe and potent antibacterial agents as natural products. 相似文献
58.
Shady Nada Mohamed Hagar Omaima Farahat Ahmed A. Hasanein Abdul-Hamid Emwas Abeer Ali Sharfalddin Mariusz Jaremko Mohamed A. Zakaria 《Molecules (Basel, Switzerland)》2022,27(7)
Three rings 2-hydroxypyridine liquid crystalline compounds have been prepared and fully characterized. The mesomorphic behavior of the prepared compounds has been investigated in terms of differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Moreover, a comparative study between the prepared compounds and previously reported analogs has been discussed in terms of the orientation and position of the mesogenic core, in addition to the direction of the terminal alkyl chains. Furthermore, a detailed computational approach has been studied to illustrate the effect of geometrical and dimensional parameters on the type of the enhanced texture and the mesomorphic range and stability. The results of the DFT study revealed that the orientation of the mesogen could affect the mesomorphic behavior and this has been attributed in terms of the degree of the polarizability of the linking groups. This result has been confirmed by calculation of the net dipole moment and the molecular electrostatic potential that show how the mesogen orientation and position could impact the molecular charge separation. Finally, the effect of the pyridyl group has been also investigated in terms of the calculated aromaticity index and the π-π stacking. 相似文献
59.
Zuriati Zakaria 《中国化学会会志》2020,67(12):2241-2245
This article reflects on the Federation of Asian Chemical Societies (FACS) Citation Award Lecture delivered in the Industrial Technology Research Institute Symposium on CO2 Utilization and Green Technology during the 18th Asian Chemical Congress held in Taipei, December 12, 2019. Malaysia produces sizable amounts of palm oil and palm kernel oil, with palm fronds and tree trunks as the main waste. At the Malaysia Japan International Institute of Technology, the biomass was decomposed to produce fine chemicals, used as substrate for mushroom growth, and converted to bio-coke for heat energy. A notable difference has been found regarding the emission of greenhouse gases from a natural peat forest and those from the oil palm plantation converted from peatlands, where in the palm plantation, water table is lowered and aerobic processes occurs, resulting in more CO2 being released compared to CH4. The introduction of fertilizers to the plantation resulted in more N2O being released. The team has also pioneered a project to plant temperate vegetables. Cooling pipes (16–18°C with circulating water cooled by chiller) were embedded within each thermal conditioning soil plot. Lettuce and radish, the experimental plants, showed good growth in the thermal conditioning soil due to nitrogen-fixing bacteria, which were destroyed at a higher temperature. 相似文献
60.
Based on a modified-Darcy-Maxwell model, two-dimensional, incompressible and heat transfer flow of two bounded layers, through electrified Maxwell fluids in porous media is performed. The driving force for the instability under an electric field, is an electrostatic force exerted on the free charges accumulated at the dividing interface. Normal mode analysis is considered to study the linear stability of the disturbances layers. The solutions of thelinearized equations of motion with the boundary conditions lead to an implicit dispersion relation between the growth rate and wave number. These equations are parameterized by Weber number, Reynolds number, Marangoni number, dimensionless conductivities, and dimensionless electric potentials. The case of long waves interfacial stability has been studied. The stability criteria are performed theoretically in which stability diagrams are obtained. Inthe limiting cases, some previously published results can be considered as particular cases of our results. It is found that the Reynolds number plays a destabilizing role in the stability criteria, while the damping influence is observed for the increasing of Marangoni number and Maxwell relaxation time. 相似文献