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71.
A synthetic approach for the preparation of 17β-acetamido-3-aza-A-homo-4α-androsten-4-one is described. 相似文献
72.
Dimitrios Kallias C. I. Stassinopoulou Panayotis Catsoulacos 《Journal of heterocyclic chemistry》1980,17(5):1045-1047
The reaction of 16α-bromoketosteroids, 2α-bromoketosteroids and 21-bromoketosteroids with thiosemi-carbazide in 2-propanol produces the corresponding 2′-amino-1′,3′,4′-thidiazinosteroids. Acetylation of the 2′-aminothiadiazino-compounds led to the diacetamidothiadiazinosteroids. The title compounds prepared were substantiated by examination of infrared and nuclear magnetic resonance spectra. 相似文献
73.
Konstantinos A. Chatziapostolou Alexios Grigoropoulos Aris Terzis Panayotis Kyritsis Georgios Pneumatikakis 《Journal of organometallic chemistry》2007,692(19):4129-4138
The complexes [Rh(CO)(PPh3){Ph2PNP(O)Ph2-P,O}] (3), [Rh(CO)2{Ph2P(Se)NP(Se)Ph2-Se,Se′}] (5), and [Rh(CO)(PPh3){Ph2P(Se)NP(Se)Ph2-Se,Se′}] (6), were synthesised by stepwise reactions of CO and PPh3 with [Rh(cod){Ph2PNP(O)Ph2-P,O}] (2) and [Rh(cod){Ph2P(Se)NP(Se)Ph2-Se,Se′}] (4), respectively. The complexes 3, 5 and 6 have been studied by IR, as well as 1H and 31P NMR spectroscopy. The ν(CO) bands of complexes 3 and 6 appear at approximately 1960 cm−1, indicating high electron density at the RhI centre. The structure of complexes 3 and 6 has been determined by X-ray crystallography, and the 31P NMR chemical shifts have been resolved via low temperature NMR experiments. Both complexes exhibit square planar geometry around the metal centre, with the five-membered ring of complex 3 being almost planar, and the six-membered ring of complex 6 adopting a slightly distorted boat conformation. The C-O bond of the carbonyl ligand is relatively weak in both complexes, due to strong π-back donation from the electron rich RhI centre. The catalytic activity of the complexes 2, 3 and 6 in the hydroformylation of styrene has been investigated. Complexes 2 and 3 showed satisfactory catalytic properties, whereas complex 6 had effectively no catalytic activity. 相似文献
74.
The gas-phase reaction of bornyl acetate (bicyclo[2,2,1]-heptan-2-ol-1,7,7-trimethyl-acetate) with hydroxyl radical has been studied. A relative method was used to determine the rate constant for this reaction, with n-octane as reference compound. Methyl nitrite photolysis experiments were carried out in an environmental smog chamber at atmospheric pressure and (294±2) K. The rate constant determined for bornyl acetate is k=(13.9±2.2)×10−12 cm3 molecule−1 s−1. The experimental rate constant has been compared with the rate constants calculated with the structure-activity relationship (SAR) and with the evolution trend of the acetate rate constants. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 497–502, 1998 相似文献
75.
We study analytically and numerically a class of traveling and standing waves in a model of weakly non-linear gravity water waves on the sphere. These waves are ‘near-monochromatic’ in space, i.e. their amplitude consists of one spherical harmonic plus small corrections, and we see numerically that they retain this property for long time. A main feature of the model we consider is that it possesses a Hamiltonian structure. This structure is preserved by our numerical implementation, and we use formal and rigorous arguments from classical perturbation theory to understand the numerical observations. 相似文献
76.
Integrated Deadenylase Genetic Association Network and Transcriptome Analysis in Thoracic Carcinomas
Athanasios Kyritsis Eirini Papanastasi Ioanna Kokkori Panagiotis Maragozidis Demetra S. M. Chatzileontiadou Paschalina Pallaki Maria Labrou Sotirios G. Zarogiannis George P. Chrousos Dimitrios Vlachakis Konstantinos I. Gourgoulianis Nikolaos A. A. Balatsos 《Molecules (Basel, Switzerland)》2022,27(10)
77.
E. Ivanov R. Kotsilkova E. Krusteva E. Logakis A. Kyritsis P. Pissis C. Silvestre D. Duraccio M. Pezzuto 《Journal of Polymer Science.Polymer Physics》2011,49(6):431-442
We report on the effect of processing conditions on rheology, thermal and electrical properties of nanocomposites containing 0.02–0.3 wt % multiwall carbon nanotubes in an epoxy resin. The influence of the sonication, the surface functionalization during mixing, as well as the application of external magnetic field (EMF) throughout the curing process was examined. Rheological tests combined with optical microscopy visualization are proved as a very useful methodology to determine the optimal processing conditions for the preparation of the nanocomposites. The Raman spectra provide evidence for more pronounced effect on the functionalized with hardener compositions, particularly by curing upon application of EMF. Different chain morphology of CNTs is created depending of the preparation conditions, which induced different effects on the thermal and electrical properties of the nanocomposites. The thermal degradation peak is significantly shifted towards higher temperatures by increasing the nanotube content, this confirming that even the small amount of carbon nanotubes produces a strong barrier effect for the volatile products during the degradation. The ac conductivity measurements revealed lower values of the percolation threshold (pc) in the range of 0.03–0.05 wt %. CNTs for the nanocomposites produced by preliminary dispersing of nanotubes in the epoxy resin, compared to those prepared by preliminary functionalization of the nanotubes in the amine hardener. This is attributed to the higher viscosity and stronger interfacial interactions of the amine hardener/CNT dispersion which restricts the reorganization of the nanotubes. The application of the EMF does not influence the pc value but the dc conductivity values (σdc) of the nanocomposites increased at about one order of magnitude due to the development of the aforementioned chain structure. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献
78.
Panayotis Panayotaros 《Physics letters. A》2009,373(10):957-963
We consider real breather solutions of the discrete cubic nonlinear Schrödinger equation near the limit of vanishing coupling between the lattice sites and present leading order asymptotics for the eigenvalues of the linearization around the breathers. The expansion is given in fractional powers of the intersite coupling parameter and determines the linear stability of the breathers. The method we use relies on normal form ideas and applies to one and higher-dimensional lattices. We also present some examples. 相似文献
79.
We consider a diatomic chain with nearest neighbors connected by phase-transforming springs. Assuming a piecewise linear interaction
force, we use the Fourier transform to construct exact traveling wave solutions representing a moving phase-transition front
and examine their stability through numerical experiments. We find that the identified traveling wave solutions may be stable
in some velocity intervals. We show that the kinetic relation between the driving force on the phase boundary and its velocity
is significantly affected by the ratio of the two masses. When the ratio is small enough, the relation may become multivalued
at some velocities, with the two solutions corresponding to the different orders in which the two springs in a dimer cell
change phase. The model bears additional interesting waveforms such as the so-called twinkling phase, which is also briefly
discussed and compared to its monatomic analog. 相似文献
80.
Maganas D Staniland SS Grigoropoulos A White F Parsons S Robertson N Kyritsis P Pneumatikakis G 《Dalton transactions (Cambridge, England : 2003)》2006,(19):2301-2315
The S/Se-containing bidentate ligands LH of the type R2P(E)NHP(E)R'2, E = S, Se and R, R' = Ph or iPr have been employed to synthesize ML2 (M = Mn, Co) complexes which contain the biologically important MS4 core. Theoretical calculations on the LH and L- forms of the ligands probe the geometric and electronic changes induced by the deprotonation of the LH form, which are correlated with structural data from X-ray crystallography. These results reflect the flexibility of the ligands, which enables them to be rather versatile with respect to the formation of ML2 complexes with varied geometries and MEPNPE metallacycle conformations. A series of old and new ML2 complexes have been synthesized and their structural, spectroscopic and magnetic properties characterized in detail. The nephelauxetic ratio beta of the CoL2 complexes provides evidence of covalent interactions, whereas the EPR properties of the MnL2 complexes are interpreted on the basis of predominant ionic interactions, between the metal center and the ligands, respectively. Additional evidence for the existence of covalent interactions in the CoL2 complexes (R = Ph, iPr, or mixed Ph/iPr), is offered by comparisons between their 31P NMR. The aforementioned notations are supported by extensive theoretical calculations on the ML2 (E = S, R = Me) modelled structures, which probe the covalent and ionic character of the M-S bonds when M = Co or Mn. Wider implications of the findings of the present study on the M-S covalency and its importance in the active sites of various metalloenzymes are also discussed. 相似文献