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81.
Soltzberg LJ Slinker JD Flores-Torres S Bernards DA Malliaras GG Abruña HD Kim JS Friend RH Kaplan MD Goldberg V 《Journal of the American Chemical Society》2006,128(24):7761-7764
We have used matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and micro-Raman spectroscopy to identify a quenching species that is formed during operation of [Ru(bpy)3]2+ electroluminescent devices. We identify this performance-degrading product to be the oxo-bridged dimer [(bpy)2(H2O)RuORu(OH2)(bpy)2]4+ and show this dimer to be an effective quencher of device luminescence. This work is the first to detect a specific chemical degradation product formed during iTMC OLED operation. 相似文献
82.
Armengol Gasull Hector Giacomini Maite Grau 《Journal of Applied Analysis & Computation》2017,7(4):1549-1569
This paper deals with the problem of location and existence of limit cycles for real planar polynomial differential systems. We provide a method to construct Poincar\''e--Bendixson regions by using transversal curves, that enables us to prove the existence of a limit cycle that has been numerically detected. We apply our results to several known systems, like the Brusselator one or some Li\''{e}nard systems, to prove the existence of the limit cycles and to locate them very precisely in the phase space. Our method, combined with some other classical tools can be applied to obtain sharp bounds for the bifurcation values of a saddle-node bifurcation of limit cycles, as we do for the Rychkov system. 相似文献
83.
Hector R. Guzmn-Carrillo Alejandro Manzano-Ramírez Ines Garcia Lodeiro Ana Fernndez-Jimnez 《Molecules (Basel, Switzerland)》2020,25(23)
This paper reports an Alkali-Activated Materials (AAM) using two different precursors, metakaolin and a metallurgical slag with photocatalytic zinc oxide nanoparticles, as novel photocatalytic composites. The photodegradation performance of the composites using methylene blue (MB) dye as a wastewater model was investigated by ultraviolet radiations (UV-vis) spectroscopy. Adsorption in dark conditions and photodegradation under UV irradiation are the mechanisms for removing MB dye. The pseudo-first-order kinetic and pseudo-second-order kinetic models were employed, and the experimental data agreed with the pseudo-second-order model in both cases with UV and without UV irradiations. As new photocatalytic materials, these composites offer an alternative for environmental applications. 相似文献
84.
Carlos Alberto Camacho Olguin Arturo Garcia-Borquez Carlos Alberto González-Rodríguez Jose Antonio Loran-Juanico Hector Cruz-Mejía 《辐射效应与固体损伤》2013,168(6):519-527
Diluted alloys of the binary system Ni–Si have been used as target of beam of ions, electrons, neutrons and so on because in this kind of alloy occurs transformations order–disorder, when the temperature is raised. This fact has permitted to evaluate the phenomena associated with the damage induced by irradiation (DII). The results of these works have been employed to understand the behavior under irradiation of complex alloys and to evaluate the reliability of the results of mathematical simulation of the evolution of the DII. The interest in the alloy system Ni-Si has been reborn due to the necessity of developing materials, which have better resistance against the corrosion on more aggressive environments such as those generated on the nuclear power plants or those that exist out of the Earth's atmosphere. Now, a growing interest to use concentrated alloys of this binary system on diverse fields of the materials science has been taking place because up to determined concentration of silicon, a regular eutectic is formed, and this fact opens the possibility to develop lamellar composite material by directional solidification. However, nowadays, there is a lack of fundamental knowledge about the behavior of this type of lamellar structure under aggressive environments, like those mentioned before. Hence, the task of this work is to evaluate the effect that has the irradiation over the microstructure of the concentrated alloy Ni22at%Si. The dendritic region of the hypereutectic alloy consists of an intermetallic phase Ni3Si, whereas the interdendritic region is formed by the alternation of lamellas of solid solution α-Ni and intermetallic phase Ni3Si. Such kind of microstructure has the advantage to get information of the DII over different phases individually, and at the same time, about of the microstructure influence over the global damage in the alloy. The hypereutectic Ni22at%Si alloy was irradiated perpendicularly to its surface, with 3.66?MeV – Ni ions up to 380?dpa at 650°C in a Tandetron linear accelerator. The level of irradiation dose was chosen similar to the irradiation conditions of the next-generation nuclear reactors. The theoretical maximum depth of the DII (maximum depth of damage (MDD)) was calculated as 1.35?µm using the SRIM-2013 program; the laminar microstructure of the eutectic was simulated using the lattice parameters of the eutectic before irradiation. The experimental MDD was 1.47?µm, as determined through transmission electron microscope (TEM) images and the DII was characterized using µX-ray diffraction and TEM. The elimination of cubic phase of the intermetallic Ni3Si, the suppression of lamellae of the α-Ni phase, the generation of dislocation loops and lines, all of these changes generated by the irradiation are clear evidences that the DII was severe. Based on theoretical and experimental evidence, we propose that the amount of phases, alternate of lamellae with different chemical concentrations of silicon and lamellae spatial distribution have a direct relation with the severe evolution of the DII. 相似文献
85.
Clayane Carvalho dos Santos Marcelo de Assis Thales Rafael Machado Paula Fabiana dos Santos Pereira Gladys Minguez‐Vega Eloisa Cordoncillo Hector Beltran‐Mir Carlos Doate‐Buendía Juan Andrs Elson Longo 《Particle & Particle Systems Characterization》2019,36(6)
In this work, for the first time, the instantaneous nucleation and growth processes of Ag nanoparticles on Ag3PO4 mediated by femtosecond laser pulses are reported and analyzed. The investigated samples are pure Ag3PO4 sample, electron‐irradiated Ag3PO4 sample, and laser‐irradiated sample. Complete characterization of the samples is performed using X‐ray diffraction (XRD), Rietveld refinements, field emission scanning electron microscopy, and energy dispersive spectroscopy (EDS). XRD confirms that the irradiated surface layer remains crystalline, and according to EDS analysis, the surface particles are composed primarily of Ag nanoparticles. This method not only offers a one‐step route to synthesize Ag nanoparticles using laser‐assisted irradiation with particle size control, but also reports a complex process involving the formation and subsequent growth of Ag nanoparticles through an unexpected additive‐free in situ fabrication process. 相似文献
86.
Simona E. Hunyadi Murph Catherine J. Murphy Hector R. Colon-Mercado Ricardo D. Torres Katie J. Heroux Elise B. Fox Lucas B. Thompson Richard T. Haasch 《Journal of nanoparticle research》2011,13(12):6347-6364
In this article, we report the precise control of the size, shape, and surface morphology of Au–Pt nanocatalysts (cubes, blocks,
octahedrons, and dogbones) synthesized via a seed-mediated approach. Gold “seeds” of different aspect ratios (1–4.2), grown
by a silver-assisted approach, were used as templates for high-yield production of novel Au–Pt nanocatalysts at a low temperature
(40 °C). Characterization by electron microscopy (SEM, TEM, HRTEM), energy dispersive X-ray analysis, UV–Vis spectroscopy,
zeta-potential (surface charge), atomic force microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma
mass spectrometry were used to better understand their physico-chemical properties, preferred reactivities and underlying
nanoparticle growth mechanism. A rotating disk electrode was employed to evaluate the Au–Pt nanocatalysts electrochemical
performance in the oxygen reduction reaction (ORR) and the methanol oxidation reaction of direct methanol fuel cells. The
results indicate the Au–Pt dogbones are partially and in some cases completely unaffected by methanol poisoning during the
evaluation of the ORR. The ORR performance of the octahedron particles in the absence of MeOH is superior to that of the Au–Pt
dogbones and Pt-black; however, its performance is affected by the presence of MeOH. 相似文献
87.
NbCl5 has been employed as promoter of a novel rearrangement to afford chiral N-substituted 1,3-thiazine-2,4-diones with one or two new stereogenic centers from di- and trisubstituted N-enoyl oxazolidinethiones. The trisubstituted E-isomers provide the anti-diastereomers mainly. 相似文献
88.
Eduardo Dfaz Hector Barrios Jose Luis Nava Raul G. Enriquez Angel Guzmn Len G. Leticia Jose Fernando Fuentes Fuentes B. Aidee Angelina Quintero Jose Dolores Solano 《Journal of heterocyclic chemistry》1997,34(3):1037-1041
The Stereoselective addition of the pyrimidine derivative 1 to the exocyclic methylene of the α,β unsaturated dehydrocostus lactone 2, Ivalin acetate 3 and Zaluzanin A diacetate 4, was achieved resulting in a new C-C bond formation. In the cases of compounds 3 and 4, after the addition, the lactone was cleaved followed by reclosure into a lactam ring system. 相似文献
89.
90.
Max Chacn Hector Rojas-Pescio Sergio Pealoza Jean Landerretche 《Entropy (Basel, Switzerland)》2022,24(3)
The mechanism of cerebral blood flow autoregulation can be of great importance in diagnosing and controlling a diversity of cerebrovascular pathologies such as vascular dementia, brain injury, and neurodegenerative diseases. To assess it, there are several methods that use changing postures, such as sit-stand or squat-stand maneuvers. However, the evaluation of the dynamic cerebral blood flow autoregulation (dCA) in these postures has not been adequately studied using more complex models, such as non-linear ones. Moreover, dCA can be considered part of a more complex mechanism called cerebral hemodynamics, where others (CO2 reactivity and neurovascular-coupling) that affect cerebral blood flow (BF) are included. In this work, we analyzed postural influences using non-linear machine learning models of dCA and studied characteristics of cerebral hemodynamics under statistical complexity using eighteen young adult subjects, aged 27 ± 6.29 years, who took the systemic or arterial blood pressure (BP) and cerebral blood flow velocity (BFV) for five minutes in three different postures: stand, sit, and lay. With models of a Support Vector Machine (SVM) through time, we used an AutoRegulatory Index (ARI) to compare the dCA in different postures. Using wavelet entropy, we estimated the statistical complexity of BFV for three postures. Repeated measures ANOVA showed that only the complexity of lay-sit had significant differences. 相似文献