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31.
Trujillo C Lamsabhi AM Mó O Yáñez M Salpin JY 《Organic & biomolecular chemistry》2008,6(20):3695-3702
The structures and relative stabilities of the complexes formed by uracil and its sulfur derivatives, namely, 2-thio-, 4-thio, and 2,4-dithio-uracil when interacting with Ca(2+) in the gas phase have been analyzed by means of density functional theory (DFT) calculations carried out at the B3LYP/6-311++G(3df,2p)//B3LYP/6-31+G(d,p) level. For uracil and 2,4-dithiouracil, where the two basic sites are the same, Ca(2+) attachment to the heteroatom at position 4 is preferred. However, for the systems where both types of basic centers, a carbonyl or a thiocarbonyl group, are present, Ca(2+)-oxygen association is favored. The most stable complexes correspond to structures with Ca(2+) bridging between the heteroatom at position 2 of the 4-enol (or the 4-enethiol) tautomer and the dehydrogenated ring nitrogen, N3. The enhanced stability of these enolic forms is two-fold, on the one hand Ca(2+) interacts with two basic sites and on the other triggers a significant aromatization of the ring. Besides, Ca(2+) association has a clear catalytic effect on the tautomerization processes which connect the oxo-thione forms with the enol-enethiol tautomers. Hence, although the enol-enethiol tautomers of uracil and its thio derivatives should not be observed in the gas phase, the corresponding Ca(2+) complexes are the most stable species and should be accessible, because the tautomerization barriers are smaller than the Ca(2+) binding energies. 相似文献
32.
Thomas Sephton Anastasios Charitou Dr. Cristina Trujillo Dr. Jonathan M. Large Dr. Sam Butterworth Prof. Michael F. Greaney 《Angewandte Chemie (International ed. in English)》2023,62(49):e202310583
Anilines are potentially high-value arylating agents, but are limited by the low reactivity of the strong C−N bond. We show that the reactive intermediate benzyne can be used to both activate anilines, and set-up an aryl transfer reaction in a single step. The reaction does not require any transition metal catalysts or stoichiometric organometallics, and establishes a metal-free route to valuable biaryl products by functionalizing the aniline C−N bond. 相似文献
33.
Gregory F. Lawler José A. Trujillo Ferreras 《Transactions of the American Mathematical Society》2007,359(2):767-787
The Brownian loop soup introduced by Lawler and Werner (2004) is a Poissonian realization from a -finite measure on unrooted loops. This measure satisfies both conformal invariance and a restriction property. In this paper, we define a random walk loop soup and show that it converges to the Brownian loop soup. In fact, we give a strong approximation result making use of the strong approximation result of Komlós, Major, and Tusnády. To make the paper self-contained, we include a proof of the approximation result that we need.
34.
Jose G. Trujillo‐Ferrara Efrn V. García‐Bez Itzia I. Padilla‐Martínez Francisco J. Martínez‐Martínez Norberto Farfan‐García 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(6):o427-o430
In exo‐2‐(3,5‐dioxo‐10‐oxa‐4‐azatricyclo[5.2.1.02,6]dec‐8‐en‐4‐yl)phenyl acetate, C16H13NO5, the plane of the acetoxy group lies almost perpendicular to that of the phenyl ring [dihedral angle = 89.8 (1)°], in contrast with the smaller deviations found in the para isomer exo‐4‐(3,5‐dioxo‐10‐oxa‐4‐azatricyclo[5.2.1.02,6]dec‐8‐en‐4‐yl)phenyl acetate, C16H13NO5, these being 63.6 (1) and 37.0 (1)° for the two crystallographically independent molecules. Irrespective of the position of the acetoxy group, both compounds pack through soft C—H⋯X (X is O or phenyl) interactions, forming interlinked centrosymmetric tetramers in the bc plane. 相似文献
35.
Leonardo Di G. Sigalotti Antonio Mejias Leonardo Trujillo 《Chaos, solitons, and fractals》2009,42(5):3177-3178
In a previous note, we have provided a formal derivation of the transverse Doppler shift of special relativity from the generalization of El Naschie’s complex time. Here, we show that the relativistic energy–momentum equation, and hence the Klein–Gordon equation, are also natural consequences of the complex time generalization. 相似文献
36.
H. D. Colorado J. S. Trujillo Hernandez G. A. Pérez Alcázar Alberto Bolaños 《Hyperfine Interactions》2014,224(1-3):171-178
In this work the Cu0.91Fe0.09O nanocrystalline system was prepared via the co-precipitation method. Using Mössbauer Spectrometry, X-Ray Diffraction, Vibrating Sample Magnetometry, Thermogravimetry and Differential Scanning Calorimetry, we study the magnetic behavior, and the structural and calorimetric properties of this system. X-ray diffraction shows only the presence of the CuO structural monoclinic phase, suggesting that Cu atoms are substituted by Fe ones. This hypothesis was confirmed by Mössbauer spectrometry at room temperature, because it shows that the spectrum is formed by two doublets, which correspond to Fe?+?2 and Fe?+?3 sites. Hysteresis cycles obtained by vibrating sample magnetometry detect a soft ferromagnetic behavior at room temperature with coercive fields between 8 and 20 Oe. At T = 20 K the sample shows a hard-magnetic behavior. The thermogravimetry results show a Néel temperature (T N > 440 °C). The differential scanning calorimetry curve show two endothermic peaks in the 90–120 °C range. 相似文献
37.
M. Benhaliliba C.E. Benouis A. Tiburcio-Silver F. Yakuphanoglu A. Avila-García A. Tavira R.R. Trujillo Z. Mouffak 《Journal of luminescence》2012,132(10):2653-2658
In this paper, we studied the photoluminescence (PL), the morphological, electrical and optical properties of pure and copper-doped cadmium oxide. CdO films were grown by a facile sol–gel spin coating process at 1200 rpm, and doped with copper at 2 and 3%. A (1 1 1)-oriented cubic structure with a lattice parameter of a=4.69 Å was confirmed by X-ray diffraction. Copper was shown to improve the optical transmittance in the short wavelength range of the visible spectrum. The optical band gap of CdO ranged between 2.49 and 2.62 eV as a result of Cu content. At room temperature, resistance fell drastically with Cu doping levels. AFM analysis of samples exhibited nano-mounts and nanowires. Finally, PL results showed a strong blue–violet emission peak at 2.80 eV. 相似文献
38.
We present a hydrodynamic theoretical model for “Brazil nut” size segregation in granular materials. We give analytical solutions for the rise velocity of a large intruder particle immersed in a medium of monodisperse fluidized small particles. We propose a new mechanism for this particle size-segregation due to buoyant forces caused by density variations which come from differences in the local “granular temperature”. The mobility of the particles is modified by the energy dissipation due to inelastic collisions and this leads to a different behavior from what one would expect for an elastic system. Using our model we can explain the size ratio dependence of the upward velocity. 相似文献
39.
The first synthesis of justicidone (4-(1',3'-Benzodioxol-5'-yl)-6-methoxynaphtho[2,3-c]furan-1,5,8(3H)-trione) was carried out from piperonal, as a starting compound, through a lineal process using well known reactions. 相似文献
40.
M. Jose Martin Luis A. Trujillo M. Carmen Garcia Jose Muñoz 《Journal of Dispersion Science and Technology》2018,39(11):1627-1634
The objective of this work was to formulate and to further improve the stability of emulsions based on thyme essential oil. Several nonionic surfactants of different nature and with different hydrophilic?lipophilic balance (HLB) values were investigated. The surfactant with optimal HLB found for the thyme essential oil was Appyclean 6548 (HLB: 9-9.5). Afterwards, stabilizing biopolymers were added in order to improve emulsion stability. Properties of emulsions were evaluated in terms of droplet size and physical stability. Thyme essential oil/W emulsions formulated with a new biodegradable emulsifier (alkyl polypentoside) and welan gum as stabilizer were obtained with high shelf-life. 相似文献