全文获取类型
收费全文 | 120篇 |
免费 | 8篇 |
专业分类
化学 | 69篇 |
力学 | 4篇 |
数学 | 12篇 |
物理学 | 43篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 11篇 |
2012年 | 3篇 |
2011年 | 8篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 12篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 5篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1975年 | 1篇 |
1930年 | 1篇 |
排序方式: 共有128条查询结果,搜索用时 15 毫秒
111.
Silver doped indium oxide (In2−x Agx O3−y) thin films have been prepared on glass and silicon substrates at room temperature (300 K) by reactive DC magnetron sputtering technique using an alloy target of pure indium and silver (80: 20 atomic %. The magnetron power (and hence the metal atom sputter flux) is varied in the range 40-80 W. The energy dispersive analysis of X-ray (EDAX) results show that the silver content in the film decreases with increasing magnetron power. The grain size of these films is of the order of 100 nm. The resistivity of these films is in the range 10−2-10−3 Ω cm. The work function of the silver-indium oxide films (by Kelvin Probe) are in the range: 4.64-4.55 eV. The refractive index of these films (at 632.8 nm) varies in the range: 1.141-1.195. The optical band gap of indium oxide (3.75 eV) shrinks with silver doping. Calculations of the partial ionic charge (by Sanderson's theory) show that silver doping in indium oxide thin films enhance the ionicity. 相似文献
112.
113.
In this paper the optimal performance of time modulated nine-ring concentric circular antenna array with isotropic elements has been studied based on an evolutionary optimization algorithm hybridized with local heuristic search called memetic firefly algorithm (MFA). The firefly algorithm has been applied followed by Nelder–Mead simplex method for the local heuristic search to achieve the optimal fine tuning. Other algorithms like real coded genetic algorithm (RGA) and particle swarm optimization (PSO) have been used for the comparison purpose. The comparisons among the algorithms have been made with two case studies as Case-1 and Case-2, and with two different fitness functions \((f_{{ fitness}1}, f_{{ fitness}2})\) and three control parameters like inter-element uniform/non-uniform spacing in rings, inter-ring radii and the switching-on times of rings. The simulation results show that the MFA outperforms RGA and PSO for both the cases Case-1, Case-2 and \(f_{{ fitness}1}\), \(f_{{ fitness}2}\), respectively with respect to better side lobe level (SLL). The fitness function \(f_{{ fitness}2}\) is better than the \(f_{{ fitness}1}\) with respect to sideband level. Apart from this, powers radiated at the centre/fundamental frequency and the first two sideband frequencies, and dynamic efficiency have been computed. It is found that power radiated by any sideband frequency is much less as compared to the power radiated at the centre frequency. It has been observed that as the sideband frequency increases, SBL decreases to the greater extent as compared to SLL. As per authors’ knowledge there is a little research contribution by any other previous researcher regarding numerical computation of radiation characteristics as SBLs, powers radiated at the fundamental frequency and its two sideband frequencies, directivity, and dynamic efficiency for time-modulated CCAA. 相似文献
114.
Samik Gupta Sachindranath Pal Anil Kumar Barik Arijit Hazra Somnath Roy Tarak Nath Mandal Shie-Ming Peng Gene-Hsiang Lee M. Salah El Fallah Javier Tercero Susanta Kumar Kar 《Polyhedron》2008
Three binuclear Cu(II) complexes of two pyrimidine derived Schiff base ligands, 2-S-methyl-6-methyl-4-formyl pyrimidine-N(4)-ethyl thiosemicarbazone (HL1) and salicyl hydrazone of 2-hydrazino-4,6-dimethylpyrimidine (HL2), have been prepared. HL1 produces a bis(μ-thiolato) Cu(II) complex co-crystallizing with its mononuclear analog, [Cu2(L1)2(NO3)2][Cu(L1)(NO3)] (1). On the other hand HL2 shows versatility by producing two different classes of binuclear Cu(II) complexes, a bis(μ-phenoxo) complex [Cu2(L2)2(NO3)2] (2) and another a (μ-4,4′-bipyridyl) complex, [Cu2(L2)2(μ-4,4′-bipyridyl)(NO3)2] (3) under suitable conditions. All the three complexes show distorted square pyramidal geometry around each Cu atom but to a varied extent. Magnetic behavior of complex 1 shows that it is strongly ferromagnetic in nature whereas compounds 2 and 3 are weakly antiferromagnetic in nature. A magnetostructural correlation study combined with molecular modelling on complexes 1 and 2 has thrown light on the difference on magnetic interaction between the Cu atoms in these two complexes. Various factors that may be responsible for such differences are also explored. A novel and potentially useful pH dependant conversion of 3 to 2 has also been noticed. 相似文献
115.
Samik Gupta Bijan Kumar Paul Anil Kumar Barik Tarak Nath Mandal Somnath Roy Nikhil Guchhait Ray J. Butcher Susanta Kumar Kar 《Polyhedron》2009,28(16):3577-3585
Dioxomolybdenum(VI) complexes [MoO2(B1)H2O] (1), [MoO2(B2)EtOH] (2), [MoO2(B3)EtOH] (3) and [MoO2(B4)EtOH] (4) were synthesized using the Schiff base ligands H2B1(previously reported), H2B2, H2B3 and H2B4, respectively. These ligands were prepared by condensation of 1-(2-pyridyl) 5-methyl 3-pyrazole carbohydrazide with salicylaldehyde, o-hydroxy acetophenone, 5-bromo salicylaldehyde and 5-nitro salicylaldehyde respectively. Due to the presence of a substituted 1-(2-pyridyl) pyrazole unit, ligands H2B1, H2B2 and H2B3 exhibit fluorescent emissions, and the most intense emission was obtained for H2B3. H2B4 is incapable of showing fluorescence emission. As the ligands are capable of using different binding modes, according to the demands of the guest metal ions, their emission properties also change accordingly. The dioxomolybdenum(VI) complex of the ligand H2B1, i.e. complex 1, shows quenched emission compared to H2B1. Again when Cu2+, Co2+ or Ni2+ ions are added to a solution of 1, in each case a new complex of Cu2+ Co2+ or Ni2+ is formed in solution and further quenching was observed. However, with Zn2+ input to a solution of 1, fluorescence recovery was observed up to the level of the free ligand. The copper(II) complex of H2B1 (complex 5), produced by adding equivalent amount of Cu2+ salt to a solution of 1, was isolated and characterized. One of the dioxomolybdenum(VI) complexes, 3, when subjected to an oxo-transfer reaction with PPh3 produces complex [MoO(B3)CH3CN] (6). Complex 6 shows reduced fluorescence emissions compared to 3 in the solid phase. These observations open up the possibilities for these ligands to work as fluorescent signaling system with different metal ion inputs. All the complexes are characterized by elemental analyses, electronic spectra, IR, 1H NMR, magnetic measurements, EPR and by cyclic voltammetry. Complexes 1 and 5, as well as the ligands H2B2 and H2B3, have been crystallographically characterized. 相似文献
116.
Several properties of octet baryons such as (i) the magnetic moment, (ii) (GA/Gv)n for neutron β-decay and (iii) the charge radius of the proton have been calculated in a simple independent-quark model under the assumption that the individual constituent quarks are confined, in first approximation, by a relativistic power-law potential Vq(r)=(1+β)(av+1rv+V0) with a, v>0. In view of the simplicity of the model, the results obtained are quite encouraging. 相似文献
117.
An effective power-law potential of the form V(r) = 6.08 r0.106?6.41 is found to describe satisfactorily the gross features of the mass spectra and the leptonic width ratios of the c and b systems in a flavour-independent manner. 相似文献
118.
Incorporating the lowest-order pionic correction, the magnetic moments of the nucleon octet have been calculated in a chiral
potential model. The potential, representing phenomenologically the nonperturbative gluon interactions including gluon self-couplings,
is chosen with equally mixed scalar and vector parts in a power-law form. The results are in reasonable agreement with experiment. 相似文献
119.
Based on a quantum Langevin equation and its corresponding Hamiltonian within a c-number formalism we calculate the vibrational dephasing rate of a cubic oscillator. It is shown that leading order quantum correction due to anharmonicity of the potential makes a significant contribution to the rate and the frequency shift. We compare our theoretical estimates with those obtained from experiments for small diatomics N(2), O(2), and CO. 相似文献
120.
Sachindranath Pal Anil Kumar Barik Prahlad Aich Shie-Ming Peng Gene-Hsiang Lee Susanta Kumar Kar 《Structural chemistry》2007,18(2):149-155
Iron(III) and cobalt(III) complexes of types [Fe(LEt)2]ClO4·3/2C6H6 (1) and [Co(LEt)2]ClO4·2CH2Cl2 (2) with a new pyrimidine-derived thiosemicarbazone ligand, 2-S-methyl-6-methyl-4-formylpyrimidine-N(4)-ethylt-hiosemicarbazone (HLEt), having N, N, S donor centers have been synthesized and characterized by X-ray crystallography. The structural study shows distorted octahedral
geometry for both 1 and 2 with MN4S2 chromophores. The space group of 1 is C2/c (monoclinic) and that of 2 is P212121 (orthorhombic). The electrochemical electron transfer study in MeCN solutions shows a one-electron reductive response presumably
due to a metal(III)–metal(II) couple. 相似文献