全文获取类型
收费全文 | 157篇 |
免费 | 9篇 |
专业分类
化学 | 117篇 |
晶体学 | 4篇 |
力学 | 2篇 |
综合类 | 1篇 |
数学 | 17篇 |
物理学 | 25篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 10篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 22篇 |
2012年 | 12篇 |
2011年 | 8篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 7篇 |
2007年 | 4篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1977年 | 2篇 |
排序方式: 共有166条查询结果,搜索用时 31 毫秒
51.
Nur Fairuz Rostan Suhaila Sepeai Rozan Mohamad Yunus Norasikin Ahmad Ludin Mohd Asri Mat Teridi Mohd Adib Ibrahim Kamaruzzaman Sopian 《Surface and interface analysis : SIA》2020,52(7):422-432
Silicon (Si) solar cell has low optical absorption because of the low and indirect bandgap of Si, and the efficiency was trapped at 25% for 15 years. Si solar cell is able to achieve efficiency up to 30% by adding perovskite as multiple bandgap material through tandem formation. In this paper, the Si/perovskite interface layer was characterized to study the compatibility of perovskite on fluorine-doped tin oxide (FTO) glass and p-type Si wafer (p-Si). The single solution deposition step of methyl ammonium lead iodide, CH3NH3PbI3 (MAPbI3) perovskite film, was spin-coated at different concentration. The physical properties of the MAPbI3/FTO and MAPbI3/p-Si were obtained by profilometer, atomic force microscope, X-ray diffraction, and Raman spectroscopy. The optical properties were analyzed by ultraviolet-visible spectroscopy, photoluminescence, and infrared transmission. Then the electrical properties were measured by Hall effect. From the measurement, it is observed that 1.2M concentration of MAPbI3 thin film has the highest thickness, smoothest film surface, and largest crystallite size compared with 0.8M and 1.0M. It is found that there is an interaction in perovskite/Si interface and caused in a low-wavelength shift, and the increase in concentration of MAPbI3 helped in intensifying the Raman signal produced. 1.2M MAPbI3 thin film had the highest enhancement in light trapping property rather than 0.8M and 1.0M. The bulk concentration and conductivity of 1.2M perovskite were higher, but the resistivity was lower than 0.8M MAPbI3 because of more CH3NH3I and PbI2 concentration within MAPbI3 perovskite compound. 相似文献
52.
A multiwalled carbon nanotube disk was used for the SPE of some toxic heavy metals from environmental samples. Metal ions were adsorbed on the disk as 8-hydroxquinoline complexes, then quantitatively desorbed from the disk by using 10 mL 2 M HNO3. The effects of analytical parameters, including pH, sample volume, and flow rates, on the recoveries of Cd(II), Co(II), Ni(II), Pb(II), Fe(III), Cu(II), and Zn(II) were investigated. The influences of some 1A and 2A group elements and some other ions as concomitant ions on the recoveries of analyte ions were also examined. The LODs of the presented preconcentration-separation system for the analyte ions were found to be in the range of 1.0-5.2 microg/L. In order to validate the procedure, SRM 1577B Bovine Liver, IAEA 336 Lichen, and HR-1 Humber river sediment certified reference materials were analyzed. The proposed method has been applied to the determination of understudy elements in some pharmaceutical samples and natural water samples from different sites in Turkey. 相似文献
53.
Namik Özdemi̇r Bi̇lge Eren Muharrem Di̇nçer Yunus Bekdemi̇r 《International journal of quantum chemistry》2011,111(12):3112-3124
The title molecule, 2‐(4‐chlorophenyl)‐1‐methyl‐1H‐benzo[d]imidazole (C14H11ClN2), was prepared and characterized by 1H NMR, 13C NMR, IR, and single‐crystal X‐ray diffraction. The molecular geometry, vibrational frequencies, and gauge including atomic orbital (GIAO) 1H and 13C NMR chemical shift values of the title compound in the ground state have been calculated by using the Hartree‐Fock (HF) and density functional theory (DFT/B3LYP) method with 6‐31G(d) basis sets, and compared with the experimental data. The calculated results show that the optimized geometries can well reproduce the crystal structural parameters, and the theoretical vibrational frequencies and GIAO 1H and 13C NMR chemical shifts show good agreement with experimental values. The energetic behavior of the title compound in solvent media has been examined using B3LYP method with the 6‐31G(d) basis set by applying the Onsager and the polarizable continuum model (PCM). Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis, and nonlinear optical (NLO) properties of the title compound were investigated by theoretical calculations. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
54.
“Graph-directed” fractals are collections of metric spaces, each of which can be expressed as a union of several scaled copies of spaces from the collection. They give rise to weighted, directed graphs where the term comes from. We show in this note that any (finite) weighted, directed graph (with weights between 0 and 1) can be realized in a Euclidean space in the sense that, starting from the graph one can define a system of similitudes (with the similarity ratios being the given weights) on an appropriate Euclidean space. The point is that these maps satisfy a certain property (called the open set condition) so that the theory of Mauldin–Williams can be applied to compute the dimension of the emerging fractals. Additionally, we give a novel example of a system of graph-directed fractals. 相似文献
55.
56.
This paper reports the development of a molecular fluorescence spectroscopy-based approach for the determination of cadmium in seawater. Anthrylazamacrocycle derivatives—the fluorescence of which is enhanced when chelated to zinc or cadmium—are used as chemosensors. A detection limit of 5 nM has been found at pH 10 for both metals, and spectral shifts allow simultaneous Cd(II)/Zn(II) determination using multiwavelength analysis. While cadmium emission behavior is similar at pH 13, zinc is not detected anymore. This enables the selective detection of cadmium even at a high Zn(II)/Cd(II) ratio. The detection limit is 1 nM. Interferent removal and preconcentration have been developed using a Dowex resin, with a view to determine cadmium in seawater. A global procedure including interferent elimination, cadmium preconcentration (30 fold), and fluorescence detection at pH 13 has been evaluated on certified reference material SLEW-2. 相似文献
57.
Mohd Heikal Mohd Yunus Zahra Rashidbenam Mh Busra Fauzi Ruszymah Bt Hj Idrus Aminuddin Bin Saim 《Molecules (Basel, Switzerland)》2021,26(21)
The normal function of the airway epithelium is vital for the host’s well-being. Conditions that might compromise the structure and functionality of the airway epithelium include congenital tracheal anomalies, infection, trauma and post-intubation injuries. Recently, the onset of COVID-19 and its complications in managing respiratory failure further intensified the need for tracheal tissue replacement. Thus far, plenty of naturally derived, synthetic or allogeneic materials have been studied for their applicability in tracheal tissue replacement. However, a reliable tracheal replacement material is missing. Therefore, this study used a tissue engineering approach for constructing tracheal tissue. Human respiratory epithelial cells (RECs) were isolated from nasal turbinate, and the cells were incorporated into a calcium chloride-polymerized human blood plasma to form a human tissue respiratory epithelial construct (HTREC). The quality of HTREC in vitro, focusing on the cellular proliferation, differentiation and distribution of the RECs, was examined using histological, gene expression and immunocytochemical analysis. Histological analysis showed a homogenous distribution of RECs within the HTREC, with increased proliferation of the residing RECs within 4 days of investigation. Gene expression analysis revealed a significant increase (p < 0.05) in gene expression level of proliferative and respiratory epithelial-specific markers Ki67 and MUC5B, respectively, within 4 days of investigation. Immunohistochemical analysis also confirmed the expression of Ki67 and MUC5AC markers in residing RECs within the HTREC. The findings show that calcium chloride-polymerized human blood plasma is a suitable material, which supports viability, proliferation and mucin secreting phenotype of RECs, and this suggests that HTREC can be a potential candidate for respiratory epithelial tissue reconstruction. 相似文献
58.
Nur Hidayah Zulaikha Othman Zailani Normawati M. Yunus Asyraf Hanim Ab Rahim Mohamad Azmi Bustam 《Molecules (Basel, Switzerland)》2022,27(3)
Ionic liquids, which are extensively known as low-melting-point salts, have received significant attention as the promising solvent for CO2 capture. This work presents the synthesis, thermophysical properties and the CO2 absorption of a series of ammonium cations coupled with carboxylate anions producing ammonium-based protic ionic liquids (PILs), namely 2-ethylhexylammonium pentanoate ([EHA][C5]), 2-ethylhexylammonium hexanoate ([EHA][C6]), 2-ethylhexylammonium heptanoate ([EHA][C7]), bis-(2-ethylhexyl)ammonium pentanoate ([BEHA][C5]), bis-(2-ethylhexyl)ammonium hexanoate ([BEHA][C6]) and bis-(2-ethylhexyl)ammonium heptanoate ([BEHA][C7]). The chemical structures of the PILs were confirmed by using Nuclear Magnetic Resonance (NMR) spectroscopy while the density (ρ) and the dynamic viscosity (η) of the PILs were determined and analyzed in a range from 293.15K up to 363.15K. The refractive index (nD) was also measured at T = (293.15 to 333.15) K. Thermal analyses conducted via a thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC) indicated that all PILs have the thermal decomposition temperature, Td of greater than 416K and the presence of glass transition, Tg was detected in each PIL. The CO2 absorption of the PILs was studied up to 29 bar at 298.15 K and the experimental results showed that [BEHA][C7] had the highest CO2 absorption with 0.78 mol at 29 bar. The CO2 absorption values increase in the order of [C5] < [C6] < [C7] anion regardless of the nature of the cation. 相似文献
59.
Yunus Akcamur Behzat Altural Emin Saripinar Gert Kollenz Oliver Kappe Karl Peters Eva-Maria Peters Hans-Georg Von Schnering 《Journal of heterocyclic chemistry》1988,25(5):1419-1422
The furan-2,3-dione 1 and the thiosemicarbazones 2 combine with loss of carbon dioxide and water yielding the 1-methylenaminopyrimidine-2-thione derivatives 3 in moderate yields (30–60%). Their molecular skeleton is confirmed with aid of an X-ray structure determination of 3c . Hydrolysis of 3 leads to the 1-aminopyrimidine-2-thione 5 . 相似文献
60.
The competitive transport of Fe(III) and Ti(IV) ions and the effect of chelating agents on separation from binary mixture solutions through charged polysulfone cation-exchange membrane (SA3S) has been studied under Donnan dialysis conditions. The amount of chelating agent was taken as an equimolar of Fe(III) ion in the feed phase. In this process, the membrane separated two electrolyte solutions: the feed solution, initially containing metal salts (Fe, Ti), or metal salts solution, containing a chelating agent, and the other side (receiver solution) being HCl solution. An external potential field is not applied. It was observed that the chelating agents affect the metal transport; the transport of Fe(III) is decreased and the transport of Ti(IV) is increased. 相似文献