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141.
142.
V S K Balagurusamy S Krishna Prasad S Chandrasekhar Sandeep Kumar M Manickam C V Yelamaggad 《Pramana》1999,53(1):3-11
We have studied the electrical conductivity of well aligned samples of hexahexylthiotriphenylene (HHTT) in the pure as well
as doped states. The dopant used was a small concentration (0.62 mole %) of the electron acceptor trinitrofluorenone (TNF).
In the columnar phases, doping causes the AC(1 kHz) conductivity along the columnar axis (σ
‖) to increase by a factor of 107 or more relative to that in undoped samples; σ
‖ attains a value of 10−2S/m, which was the maximum measurable limit of our experimental set up. On the other hand, in the isotropic phase doping makes
hardly any difference to the conductivity. The frequency dependence of the conductivity has been investigated. The DC conductivity
of doped samples exhibits an enormous anisotropy, σ
‖/σ
⊥ ≥ 1010, which is 7 orders higher than that reported for any liquid crystalline system, and, to our knowledge, the largest observed
in an organic conductor.
We also report the first thermoelectric power studies on these ‘molecular wires’. The sign of the thermoelectric power is
in conformity with the expected nature of the charge carriers, namely, holes. 相似文献
143.
144.
P. Sambasiva Rao T. M. Rajendiran R. Venkatesan N. Madhu A. V. Chandrasekhar B. J. Reddy Y. P. Reddy R. V. S. S. N. Ravikumar 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2001,57(14):285-2787
Single crystal electron paramagnetic resonance (EPR) studies on Cu(II) doped zinc potassium phosphate hexahydrate (ZPPH) were carried out at room temperature. The angular variation spectra in the three orthogonal planes indicate that the paramagnetic impurity has entered the lattice substitutionally in place of Zn(II) and the spin Hamiltonian parameters calculated from these spectra are g(xx) = 2.188, g(yy) = 2.032, g(zz) = 2.373, Axx = 50 G, Ayy = 65.0 G and Azz = 80 G. The g and A tensors were coincident and these values matched fairly well with the values obtained from powder spectrum. The bonding parameters have also been calculated. 相似文献
145.
Robert R. Holmes Roberta O. Day V. Chandrasekhar Soheila Shafeizad John J. Harland Denise N. Rau 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):91-98
Abstract The synthesis of [PhSn(O)O2CC6H11]6 represents the first example of tin(IV) in a drum-shaped molecule. The formation of the dimeric composition, [(MeSn(O)O2CC6H11)2(MeSn(O2CC6H11)3]2, appears to be an intermediate hydrolysis product on the way to the drum composition. The X-ray structure reveals an “unfolded” drum array. The distannoxane unit which is represented as the sides of the drum is found in additional new dimeric compositions, [(SCH2CH2O)2SnCl]2[H][Et4N], [((CN)2C2S2)2SnOH]2, and [BuSnCl2(OH) · H2O]2. These all have six-coordinated tin atoms which contrasts to the dimeric aryl distannoxanes recently isolated, [Ph2(Cl)SnOSnPh2(X)]2, X = OH, Cl, containing five-coordinated tin. Also isolated are the new ring containing, five-coordinated tin derivatives, [(SCH2CH2S)2Sn]2[SCH2CH2S][Et3NH]2 and [(SC(CN)C(CN)S)2SnMe][Et4N]. The former has two trigonal bipyramidal tin atoms while the latter composition has a square pyramidal geometry. Related ring systems of new five-coordinated derivatives of silicon, germanium, arsenic, and antimony that span the range between the two ideal five-coordinated geometries also have been structurally characterized. 相似文献
146.
An inexpensive and safer reagent system comprising of PMHS and ZnCl2 has been developed for the selective reduction of carbonyl compounds to corresponding alcohols. 相似文献
147.
E. E. Ebenso Kripasindhu Sardar M. Chandrasekhar A. R. Raju C. N. R. Rao 《Solid State Sciences》2000,2(8)
Thin films of La1−xSrxCoO3, Nd0.5Sr0.5CoO3, Gd0.5Sr0.5CoO3 and SrRuO3 have been deposited on Si(100), LaAlO3(100) and SrTiO3(100) single crystal substrates by nebulized spray pyrolysis. The films deposited on Si are generally polycrystalline, but they are highly oriented on the oxide substrates. The cobaltate films are generally not metallic, but exhibit low resistivity specially when x=0.3 and 0.5, the latter also exhibiting ferromagnetic characteristics. Films of La0.7Sr0.3CoO3 show negative magnetoresistance of 35% around 180 K. Films of SrRuO3 are metallic on Si and LaAlO3 substrates but show an insulator–metal transition on SrTiO3 around 130 K, around which temperature negative magnetoresistance is observed. 相似文献
148.
Dr. Joydeb Goura Jamie Brambleby Dr. Paul Goddard Prof. Dr. Vadapalli Chandrasekhar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):4926-4930
We report a CoIII2DyIII complex, which shows single‐ion‐magnet behaviour. AC susceptibility data of this compound reveals the presence of slow relaxation of the magnetization in zero‐field below 15 K. The relaxation barrier is 88 K. 相似文献
149.
The solubilities of two fatty acids, namely hexadecanoic acid (palmitic acid) and octadecanoic acid (stearic acid) in supercritical carbon dioxide (SCCO2), were determined at T = (328 and 338) K from 12.8 MPa to 22.6 MPa. Three models, namely a thermodynamic model based on the Peng–Robinson equation of state with Kwak and Mansoori mixing rules, a model based on dilute solution theory proposed by Mendez-Santiago and Teja and a new reformulated Chrastil equation model, were used to correlate the solubilities. In all the models, the correlation constants are temperature independent. All the models successfully correlated the experimental results for the solubilities of hexadecanoic acid within 3%. 相似文献
150.
Hexakis(2-pyridyloxy)cyclotriphosphazene (L) is an efficient multisite coordination ligand which binds with transition metal ions to produce dinuclear (homo- and heterometallic) complexes [L(CuCl)(CoCl3)], [L(CuCl)(ZnCl3)], [L(CoCl)(ZnCl3)], and [L(ZnCl2)2]. In these dinuclear derivatives the cyclophosphazene ligand utilizes from five to six nitrogen coordination sites out of the maximum of nine available sites. Further, the spacer oxygen that separates the pyridyl moiety from the cyclophosphazene ring ensures minimum steric strain to the cyclophosphazene ring upon coordination. This is reflected in the near planarity of the cyclophosphazene ring in all the dinuclear derivatives. In the dinuclear heterobimetallic derivatives one of the metal ions [Cu(II) or Co(II)] is hexacoordinate and is bound by the cyclophosphazene in a eta5-gem-N5 mode. The other metal ion in these heterobimetallic derivatives [Co(II) or Zn(II)] is tetracoordinate and is bound in an eta(1)-N(1) fashion. In the homobimetallic derivative, [L(ZnCl2)2], one of the zinc ions is five-coordinate (eta3-nongem-N3), while the other zinc ion is tetracoordinate(eta2-gem-N2). The reaction of L with CuCl2 followed by Co(NO3)2.6H2O yields a trinuclear heterobimetallic complex [{(L'CuCl)2Co(NO3)}Cl] [L' = N3P3(OC5H4N)5(O)]. In the formation of this compound an unusual P-O bond cleavage involving one of the phosphorus-pyridyloxy bonds is observed. The molecular structure of [{(L'CuCl)2Co(NO3)}Cl] [L' = N3P3(OC5H4N)5(O)] reveals that each of the two the P-O-cleaved L' ligands is involved in binding to Cu(II) to generate the motif L'CuCl. Two such units are bridged by a Co(II) ion. The coordination environment around the bridging Co(II) ion contains four oxygen (two P-O units, one chelating nitrate) and two nitrogen atoms (pyridyloxy nitrogens). 相似文献