全文获取类型
收费全文 | 178篇 |
免费 | 16篇 |
国内免费 | 5篇 |
专业分类
化学 | 119篇 |
综合类 | 2篇 |
数学 | 4篇 |
物理学 | 74篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 10篇 |
2020年 | 13篇 |
2019年 | 8篇 |
2018年 | 18篇 |
2017年 | 4篇 |
2016年 | 12篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 14篇 |
2012年 | 9篇 |
2011年 | 14篇 |
2010年 | 9篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 3篇 |
2006年 | 4篇 |
2005年 | 7篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有199条查询结果,搜索用时 250 毫秒
191.
Investigations of the half-metallic behavior and the magnetic and thermodynamic properties of half-Heusler CoMnTe and RuMnTe compounds: A first-principles study
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
T.Djaafri A.Djaafri A.Elias G.Murtaza R.Khenata R.Ahmed S.Bin Omran D.Rached 《中国物理 B》2014,(8):444-451
First-principles spin-polarized density functional theory (DFT) investigations of the structural, electronic, magnetic, and thermodynamics characteristics of the half-Heusler, CoMnTe and RuMnTe compounds are carried out. Calculations are accomplished within a state of the art full-potential (FP) linearized (L) augmented plane wave plus a local orbital (APW + lo) computational approach framed within DFT. The generalized gradient approximation (GGA) parameterized by Perdew, Burke, and Ernzerhof (PBE) is implemented as an exchange correlation functional as a part of the total energy calculation. From the analysis of the calculated electronic band structure as well as the density of states for both compounds, a strong hybridization between d states of the higher valent transition metal (TM) atoms (Co, Ru) and lower valent TM atoms of (Mn) is observed. Furthermore, total and partial density of states (PDOS) of the ground state and the results of spin magnetic moments reveal that these compounds are both stable and ideal half-metallic ferromagnetic. The effects of the unit cell volume on the magnetic properties and half-metaliicity are crucial. It is worth noting that our computed results of the total spin magnetic moments, for CoMnTe equal to 4 ~tB and 3 p-B per unit cell for RuMnTe, nicely follow the rule μ2tot = Zt - 18. Using the quasi-harmonic Debye model, which considers the phononic effects, the effecs of pressure P and temperature T on the lattice parameter, bulk modulus, thermal expansion coefficient, Debye temperature, and heat capacity for these compounds are investigated for the first time. 相似文献
192.
Monitoring extracellular metabolites of bacteria is very useful for not only metabolomics research but also for assessment of the effects of various chemicals, including antimicrobial agents and drugs. Herein, we describe the automated headspace solid-phase microextraction (HS-SPME) method coupled with gas chromatography–mass spectrometry (GC–MS) for the qualitative as well as semi-quantitative determination of metabolic responses of Escherichia coli to an antimicrobial agent, cinnamaldehyde. The minimum inhibitory concentration of cinnamaldehyde was calculated to be 2 g L−1. We found that cinnamaldehyde was an important factor influencing the metabolic profile and growth process. A higher number of metabolites were observed during the mid-logarithmic growth phase. The metabolite variations (types and concentrations) induced by cinnamaldehyde were dependent on both cell density and the dose of cinnamaldehyde. Simultaneously, 25 different metabolites were separated and detected (e.g., indole, alkane, alcohol, organic acids, esters, etc.) in headspace of complex biological samples due to intermittent addition of high dose of cinnamaldehyde. The study was done using an automated system, thereby minimizing manual workup and indicating the potential of the method for high-throughput analysis. These findings enhanced the understanding of the metabolic responses of E. coli to cinnamaldehyde shock effect and demonstrated the effectiveness of the SPME–GC–MS based metabolomics approach to study such a complex biological system. 相似文献
193.
N. L. Tsintsadze L. N. Tsintsadze A. Hussain G. Murtaza 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,64(2-3):447-452
A general quantum dispersion equation for electron-positron(hole)-ion quantum plasmas is derived and studied for some interesting cases. In an electron-positron-ion degenerate Fermi gas, with or without the Madelung term, a new type of zero sound waves are found. Whereas in an electron-hole-ion plasmas a new longitudinal quantum waves are revealed, which have no analogies in quantum electron-ion plasmas. The excitation of these quantum waves by a low-density monoenergetic straight electron beam is examined. Furthermore, the Korteweg-de Vries (KdV) equation for novel quantum waves is derived and the contribution of the Madelung term in the formation of the KdV solitons is discussed. 相似文献
194.
溶胶凝胶合成锰掺杂ZnO的室温磁性行为 总被引:2,自引:0,他引:2
通过溶胶凝胶自燃法合成锰掺杂氧化锌纳米晶体, 研究了Mn掺杂ZnO稀磁半导体(简称DMS)的性质.X射线衍射光谱表明,锰掺杂氧化锌保留纤锌矿型状氧化锌六角晶体结构.采用能量色散X射线能谱和扫描电子显微镜分别对成分和形态进行研究.温度依赖的电阻率显示了DMS的半导体材料行为.振动样品磁强计测定的室温磁性行为,揭示了锰掺杂氧化锌的铁磁性和反磁性特性. 相似文献
195.
By employing the separated spin evolution quantum hydrodynamic model, non-linear evolution of obliquely propagating spin electron acoustic wave (SEAW) is presented. The solitary structures of SEAW is investigated through the Korteweg–de Vries (KdV) equation derived using reductive perturbation method. From the first order perturbations we derive the dispersion relation of SEAW and find that both the spin polarization and the propagation angle reduce the phase velocity while the electron streaming enhances it. Using small amplitude approximation, the solitary structure of SEAW is analyzed and the effects of spin polarization, propagation angle and electron streaming on the SEA soliton are studied. Our numerical results demonstrate that the spin polarization and the propagation angle play a balancing act on the soliton structures. The possible applications of our investigation to the astrophysical environments like white dwarfs is also discussed. 相似文献
196.
197.
Ghulam Murtaza Majid Khan Saba Farooq M. Iqbal Choudhary Sammer Yousuf 《Acta Crystallographica. Section C, Structural Chemistry》2023,79(6):237-248
Many heterocycles have been developed as drugs due to their capacity to interact productively with biological systems. The present study aimed to synthesize cocrystals of the heterocyclic antitubercular agent pyrazinamide ( PYZ , 1 , BCS III) and the commercially available anticonvulsant drug carbamazepine ( CBZ , 2 , BCS class II) to study the effect of cocrystallization on the stability and biological activities of these drugs. Two new cocrystals, namely, pyrazinamide–homophthalic acid (1/1) ( PYZ:HMA , 3 ) and carbamazepine–5-chlorosalicylic acid (1/1) ( CBZ:5-SA , 4 ), were synthesized. The single-crystal X-ray diffraction-based structure of carbamazepine–trans-cinnamic acid (1/1) ( CBZ:TCA , 5 ) was also studied for the first time, along with the known cocrystal carbamazepine–nicotinamide (1/1) ( CBZ:NA , 6 ). From a combination drug perspective, these are interesting pharmaceutical cocrystals to overcome the known side effects of PYZ ( 1 ) therapy, and the poor biopharmaceutical properties of CBZ ( 2 ). The purity and homogeneity of all the synthesized cocrystals were confirmed by single-crystal X-ray diffraction, powder X-ray diffraction and FT–IR analysis, followed by thermal stability studies based on differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Detailed intermolecular interactions and the role of hydrogen bonding towards crystal stability were evaluated quantitatively via Hirshfeld surface analysis. The solubility of CBZ at pH 6.8 and 7.4 in 0.1 N HCl and H2O were compared with the values of cocrystal CBZ:5-SA ( 4 ). The solubility of CBZ:5-SA was found to be significantly improved at pH 6.8 and 7.4 in H2O. All the synthesized cocrystals 3 – 6 exhibited a potent urease inhibition (IC50 values range from 17.32 ± 0.89 to 12.3 ± 0.8 µM), several times more potent than standard acetohydroxamic acid (IC50 = 20.34 ± 0.43 µM). PYZ:HMA ( 3 ) also exhibited potent larvicidal activity against Aedes aegypti. Among the synthesized cocrystals, PYZ:HMA ( 3 ) and CBZ:TCA ( 5 ) were found to possess antileishmanial activity against the miltefosine-induced resistant strain of Leishmania major, with IC50 values of 111.98 ± 0.99 and 111.90 ± 1.44 µM, respectively, in comparison with miltefosine (IC50 = 169.55 ± 0.20 µM). 相似文献
198.
Zakir O. Ait-Karra A. Idouhli R. Khadiri M. Dikici B. Aityoub A. Abouelfida A. Outzourhit A. 《Journal of Solid State Electrochemistry》2023,27(9):2289-2307
Journal of Solid State Electrochemistry - In the field of nanotechnology, titanium dioxide nanotubes (TiO2 NTs) are one of the most valued inventions. They were discovered in 1996, and have since... 相似文献
199.
Ait-karra A. Zakir O. Ait baha A. Lasri M. Idouhli R. Elyaagoubi M. Abouelfida A. Khadiri M. Benzakour J. 《Journal of Solid State Electrochemistry》2023,27(8):2051-2065
Journal of Solid State Electrochemistry - Copper sulfide (CuS) thin film was electrodeposited onto stainless steel (SS 316L) substrate under pulse potential control, from an aqueous acidic solution... 相似文献