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81.
Sol M. Gerchakov 《光谱学快报》2013,46(12):403-409
Dual wavelength ultraviolet spectrophotometry was utilized for the determination of 1,2,4-benzenetricarboxylic and benzenepentacarboxylic acids in their simultaneous solution. 相似文献
82.
D. Kasprowicz T. Runka A. Speghini D. Falcomer J. García Solé M. Bettinelli 《Journal of luminescence》2008,128(5-6):985-987
Vibrational Raman spectra have been measured for strontium barium niobate (Sr0.5Ba0.5Nb2O6, SBN50) single crystals and nanopowders doped with 1 mol% of the luminescent ions Eu3+ and Er3+. The nanocrystalline materials show slightly broader spectra with respect to the single crystals with the same composition. The presence of the Eu3+ and Er3+ ions at the 1 mol% doping level, and the present particle size (200 nm) do not appear to affect the ferro-to-paraelectric phase transition temperature typical of undoped SBN50 single crystals, as detected from anomalies in the dependence of the position of the Raman peak around 635 cm?1 as a function of the temperature. 相似文献
83.
84.
Structural and morphological studies on the deformation behavior of polypropylene/multi‐walled carbon nanotubes nanocomposites prepared through ultrasound‐assisted melt extrusion process 下载免费PDF全文
José M. Mata‐Padilla Carlos A. Ávila‐Orta Francisco J. Medellín‐Rodríguez Ernesto Hernández‐Hernández Rosa M. Jiménez‐Barrera Víctor J. Crúz‐Delgado Janett Valdéz‐Garza Silvia G. Solís‐Rosales Adriana Torres‐Martínez Myriam Lozano‐Estrada Enrique Díaz‐Barriga Castro 《Journal of Polymer Science.Polymer Physics》2015,53(7):475-491
Structural and morphological behavior under stress–strain of polypropylene/multi‐walled carbon nanotubes (PP/MWCNTs) nanocomposites prepared through ultrasound‐assisted melt extrusion process was studied by means of optical microscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, small angle X‐ray scattering (SAXS), and wide angle X‐ray scattering (WAXS). A high ductile behavior was observed in the PP/MWCNT nanocomposites with low concentration of MWCNTs. This was related to an energy‐dissipating mechanism, achieved by the formation of an ordered PP‐CNTs interphase zone and crystal oriented structure in the undeformed samples. Different strain‐induced‐phase transformations were observed by ex situ SAXS/WAXS, characterizing the different stages of structure development during the deformation of PP and PP/MWCNTs nanocomposites. The high concentration of CNTs reduced the strain behavior of PP due to the agglomeration of nanoparticles. A structural pathway relating the deformation‐induced phase transitions and the dissipation energy mechanism in the PP/MWCNTs nanocomposites at low concentration of nanoparticles was proposed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 475–491 相似文献
85.
Mathias Kersemans Wim Van Paepegem Koen Van Den Abeele Lincy Pyl Filip Zastavnik Hugo Sol Joris Degrieck 《Ultrasonics》2014
The ultrasonic polar scan (UPS), either in transmission, reflection or backscatter mode, is a promising non-destructive testing technique for the characterization of composites, providing information about the mechanical anisotropy, the viscoelastic damping, the surface roughness, and more. At present, the technique is merely being used for qualitative purposes. The limited quantitative exploration and use of the technique can be primarily ascribed to limitations of current theoretical models as well as the difficulty to perform accurate, and more importantly, reproducible UPS experiments. Over the last years, we have identified several potential pitfalls in the experimental implementation of the technique which severely deteriorate the accurateness and reproducibility of a UPS. In this paper, we make an inventory of the most important difficulties, illustrate each of them by a real experiment and present a feasible mediation, either numerical or experimental in nature. Once the experimental set-up is fine-tuned to overcome these pitfalls, it is expected that the recording of high-level UPS experiments, in combination with numerical computations, will facilitate the technique to become a fully quantitative non-destructive characterization method. 相似文献
86.
Sol Schwartzman 《Proceedings of the American Mathematical Society》1997,125(2):427-431
Let be a locally finite simplicial complex of finite topological dimension. Assume further that is a space where is a group whose only abelian subgroups are infinite cyclic. We prove that a Bohr almost periodic map of the real line into is uniformly homotopic to a periodic map. As a consequence we show that a Bohr almost periodic geodesic on a compact Riemannian manifold of everywhere negative curvature is necessarily periodic.
87.
The AlCl3-catalyzed acetylation of 1,2-hydrophenylated [60]fullerenes, HC60-Ar, proceeded via a sequential manner involving the acetylation at the hydrogenated fullerene carbon, the following intramolecular cyclization with the adjacent aryl group, the facile loss of water, and the second acetylation of the generated indenylidene double bond. However, the similar reaction of the hydrobiphenylated analogue brought about the normal acetylation at the terminal aromatic ring prior to the same sequential reactions as did hydrophenylated fullerenes. 相似文献
88.
The behaviour of enaminomalonates and their deprotection to amines under various reductive conditions is described. A new synthetic approach to N-aryl-N-acetyl-β-amino acids using heterogeneous catalytic hydrogenation has been discovered. 相似文献
89.
In the present work, we analyze the pi-electronic delocalization in a series of annulenes and their dications and dianions by using electron delocalization indices calculated in the framework of the quantum theory of atoms in molecules. The aim of our study is to discuss the Hückel's 4n + 2 rule from the viewpoint of pi-electronic delocalization. Our results show that there is an important increase of electronic delocalization (of about 1 e) when going from antiaromatic 4n pi systems to aromatic (4n + 2)pi systems. Less clear is the change in pi-electronic delocalization when we move from a (4n + 2)pi-aromatic to a 4n pi-antiaromatic species by adding or removing a pair of electrons. 相似文献
90.
Sala X Poater A von Zelewsky A Parella T Fontrodona X Romero I Solà M Rodríguez M Llobet A 《Inorganic chemistry》2008,47(18):8016-8024
A new set of Ru-Cl complexes containing either the pinene[5,6]bpea ligand (L1) or the C3 symmetric pinene[4,5]tpmOMe (L2) tridentate ligand in combination with the bidentate (B) 2,2'-bipyridine (bpy) or 1,2-diphenylphosphinoethane (dppe) with general formula [RuCl(L1 or L2)(B)](+) have been prepared and thoroughly characterized. In the solid state, X-ray diffraction analysis techniques have been used. In solution, cyclic voltammetry (CV) and 1D and 2D NMR spectroscopy have been employed. DFT calculations have been also performed on these complexes and their achiral analogues previously reported in our group, to interpret and complement experimental results. Whereas isomerically pure complexes ([Ru(II)Cl(L2)(bpy)](BF4), 5 and [Ru(II)Cl(L2)(dppe)](BF4), 6) are obtained when starting from the highly symmetric [Ru(III)Cl3(L2)], 2, isomeric mixtures of cis, fac-[Ru(II)Cl(L1)(bpy)](BF4) (3b/3b'), trans,fac- (3a) and up/down,mer- (3c, 3d) isomers are formed when bpy is added to the less symmetric [Ru(III)Cl3(L1)], 1, in contrast to the case of the bulky dppe ligand that, upon coordination to 1, leads to the trans,fac-[Ru(II)Cl(L1)(dppe)](BF4) (4a) complex as a sole isomer due to steric factors. 相似文献