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221.
Dr. Rhodri E. Owen Dr. Fernando Cortezon-Tamarit Dr. David G. Calatayud Enid A. Evans Samuel I. J. Mitchell Dr. Boyang Mao Dr. Francisco J. Palomares Dr. John Mitchels Dr. Pawel Plucinski Prof. Davide Mattia Prof. Matthew D. Jones Prof. Sofia I. Pascu 《ChemistryOpen》2020,9(2):242-252
We report on the design and testing of new graphite and graphene oxide-based extended π-conjugated synthetic scaffolds for applications in sustainable chemistry transformations. Nanoparticle-functionalised carbonaceous catalysts for new Fischer Tropsch and Reverse GasWater Shift (RGWS) transformations were prepared: functional graphene oxides emerged from graphite powders via an adapted Hummer's method and subsequently impregnated with uniform-sized nanoparticles. Then the resulting nanomaterials were imaged by TEM, SEM, EDX, AFM and characterised by IR, XPS and Raman spectroscopies prior to incorporation of Pd(II) promoters and further microscopic and spectroscopic analysis. Newly synthesised 2D and 3D layered nanostructures incorporating carbon-supported iron oxide nanoparticulate pre-catalysts were tested, upon hydrogen reduction in situ, for the conversion of CO2 to CO as well as for the selective formation of CH4 and longer chain hydrocarbons. The reduction reaction was also carried out and the catalytic species isolated and fully characterised. The catalytic activity of a graphene oxide-supported iron oxide pre-catalyst converted CO2 into hydrocarbons at different temperatures (305, 335, 370 and 405 °C), and its activity compared well with that of the analogues supported on graphite oxide, the 3-dimensional material precursor to the graphene oxide. Investigation into the use of graphene oxide as a framework for catalysis showed that it has promising activity with respect to reverse gas water shift (RWGS) reaction of CO2 to CO, even at the low levels of catalyst used and under the rather mild conditions employed at atmospheric pressure. Whilst the γ-Fe2O3 decorated graphene oxide-based pre-catalyst displays fairly constant activity up to 405 °C, it was found by GC-MS analysis to be unstable with respect to decomposition at higher temperatures. The addition of palladium as a promoter increased the activity of the iron functionalised graphite oxide in the RWGS. The activity of graphene oxide supported catalysts was found to be enhanced with respect to that of iron-functionalised graphite oxide with, or without palladium as a promoter, and comparable to that of Fe@carbon nanotube-based systems tested under analogous conditions. These results display a significant step forward for the catalytic activity estimations for the iron functionalised and rapidly processable and scalable graphene oxide. The hereby investigated phenomena are of particular relevance for the understanding of the intimate surface morphologies and the potential role of non-covalent interactions in the iron oxide-graphene oxide networks, which could inform the design of nano-materials with performance in future sustainable catalysis applications. 相似文献
222.
Rendiconti del Circolo Matematico di Palermo Series 1 - 相似文献
223.
Pablo G. Del Rosso Marcela F. Almassio Mattia Bruno Raúl O. Garay 《Tetrahedron letters》2010,51(51):6730-6733
A mild selective protocol was used to prepare tetrakis(2-chlorophenylthio)anthracene from tetrabromoanthracene and sodium 2-chlorobenzenethiolate avoiding the thiolate self-attack. The uncatalyzed nucleophilic substitution of a series of mono-, di-, and tetrabrominated arenes by arylthiolate ions was attempted in mild conditions to investigate the scope of the substitution reaction regarding the size of the aromatic system as well as the number of bromine atoms. Successful reactions afforded only the persubstituted products in good purity and yield after a simple workup and chemoselectivity of Br versus Cl substituents was achieved for the tetrabromide. 相似文献
224.
Rendiconti del Circolo Matematico di Palermo Series 1 - 相似文献
225.
The use of SSA fractionation to detect changes in the molecular structure of model ethylene-butene copolymers modified by peroxide crosslinking 总被引:1,自引:0,他引:1
Claudio J. Pérez N. Villarreal M.D. Failla J.M. Carella 《Polymer Degradation and Stability》2009,94(10):1639-1645
Four model ethylene-butene copolymers of different molecular weights modified with various concentrations of peroxide were analyzed by a DSC based successive self annealing method. The original copolymers had the same intra and intermolecular homogeneous branching distribution along the linear chains with approximately 2.4% mol of ethyl branches. The copolymers with average molecular weights of 29,000, 45,000, 81,000 and 125,000 g/mol were modified with different amounts of 2,5-dimethyl-2,5-di(tert-butyl peroxy)-hexane (DBPH) as a crosslinking initiator. The molecular changes induced by the reaction with the peroxide affect the semicrystalline structure of the material. Variations in the crystal thickness distributions of the material as a consequence of the modification are related to the peroxide induced free radical reactions. 相似文献
226.
We consider a class of hyperbolic 3-orbifoldsO(α/β); the underlying topological space of such an orbifold is the 3-sphere and the singular set is obtained by adding the two
standard (upper and lower) unknotting tunnels to a 2-bridge linkL(α/β) (and associating branching order two to both unknotting tunnels). These 3-orbifolds are extremal with respect to the notion
of Heegaard genus or Heegaard number of 3-orbifolds; it is to be expected that they are also extremal with respect to the
volume, that is the smallest volume hyperbolic 3-orbifolds should belong to this or some closely related class. We show that
an orbifoldO(α/β) has a uniqueD
2-covering by an orbifoldℒ
n(α/β) wose space is the 3-sphere and whose singular set is the same 2-bridge linkL(α/β) used for the construction ofO(α/β); moreoverO(α/β) is hyperbolic if and only ifℒ
n(α/β) is hyperbolic. As the volumes of the orbifoldsℒ
n(α/β) are known resp. can be computed, this allows to compute the volumes of the orbifoldsO(α/β). The problem of computation of volumes remains open for some closely related classes of 3-orbifolds which are also extremal
with respect to the Heegaard genus (for example associating a branching order bigger than two to one or both unknotting tunnels). 相似文献
227.
228.
A simple, one‐step, stereoconservative synthesis of diamine‐based peptidomimetics is described, by split‐Ugi multicomponent reaction, involving chiral N‐protected amino acids and α‐substituted isocyanoacetate. In particular, piperazine and bispidine (3,7‐diazabicyclo[3.3.1]nonane) are exploited as diamine components, bispidine being the first example of a sterically demanding bicyclic system employed in a split‐Ugi reaction. 相似文献
229.
230.
Soft,Oxidative Stripping of Alkyl Thiolate Ligands from Hydroxyapatite‐Supported Gold Nanoclusters for Oxidation Reactions 下载免费PDF全文
Bin Zhang Prof. Dr. Jun Fang Jingguo Li Jun Jie Lau Prof. Dr. Davide Mattia Dr. Ziyi Zhong Prof. Dr. Jianping Xie Prof. Dr. Ning Yan 《化学:亚洲杂志》2016,11(4):532-539
A strategy for the mild deprotection of alkyl‐thiolated (6‐mercaptohexanoic acid, MHA, and 3‐mercaptopropanoic acid, MPA) gold nanoclusters (Au NCs) supported on hydroxyapatite (HAP) has been developed by employing a peroxide (tert‐butyl hydroperoxide, TBHP, or hydrogen peroxide, H2O2) as an oxidant. The thiol ligands on the supported Au NCs were removed after oxidation, and the size and integrity of the supported clusters were well‐preserved. The bare gold clusters on HAP after removal of the ligands were catalytically effective for the epoxidation of styrene and the aerobic oxidation of benzyl alcohol. These two reactions were also investigated on calcined Au NCs that were supported on HAP for comparison, and the resulting Au NCs that were prepared by using this new strategy showed superior catalytic activity. 相似文献