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131.
Mircea V. Diudea 《Journal of mathematical chemistry》2009,45(2):354-363
Operations on maps are topological-geometrical tools used for transforming a given polyhedral tessellation. Investigation
of fullerene structure often needs information on the original map which transformed into a larger molecular structure. Operations
leading to the previous, smaller structures are called Retro-operations. They appear particularly useful in studies of structure
elucidation or stability of series of fullerenes. The paper presents the first structure affiliation of the well-known C60 fullerene to a family of Leapfrog fullerenes with relatedness being established by map operation. Thus, the tessellation
of C60 is described as an Archimedean, joint Sumanene-hexagon covering, in tetrahedral disposition. The other members of family
show essentially the same covering and predicted good stability. Related Leapfrog fullerenes showing a disjoint Sumanene covering
are also given. 相似文献
132.
The effect of a layer of electrochemically grafted 4‐diazo‐N,N‐diethylaniline (DEA) groups on the electron transfer kinetics of redox systems, displaying fast and slow heterogeneous electron transfer rate constants at edge and basal planes of carbon, was investigated. The properties of the modified electrode were characterized by cyclic voltammetry using four different inorganic redox systems (Fe(CN) , Co(phen) , Ru(NH3) , and IrCl in acidic, neutral, and basic media. Two distinct blocking behaviors and electrostatic effects were observed. More precisely, a strong blocking effect of the grafted layer on Fe(CN) and Co(phen) was found, whereas Ru(NH3) and IrCl showed to be rather unaffected by the presence of the DEA grafted layer. 相似文献
133.
Alexandru T. Balaban Mircea D. Gheorghiu Teodor Silviu Balaban 《Journal of mass spectrometry : JMS》1983,18(10):433-437
Electron impact mass spectra of 3,5,7-trisubstituted 4H-1,2-diazepines indicate that aryl substituents lead to N2 expulsion while alkyl substitutents do not. A common fragmentation pattern is observed and discussed for all alkyldiazepines, most of which are newly reported compounds. Assignments are based on electron impact mass spectra of deuteriated substrates and high resolution mass spectra. A previous interpretation of N2 expulsion is corrected. 相似文献
134.
Fullerene polyhedra of icosahedral symmetry have the midpoints of their 12 pentagonal faces at the vertices of a macroicosahedron and can be characterized by the patterns of their hexagonal faces on the (triangular) macrofaces of this macroicosahedron. The numbers of the vertices in fullerene polyhedra of icosahedral symmetry satisfy the Goldberg equation v=20(h
2+hk+k
2), where h and k are two integers and 0 <h≥ k≥ 0 and define a two-dimensional Goldberg vector G = (h, k). The known tripling (leapfrog), quadrupling (chamfering), and septupling (capra) transformations correspond to the Goldberg vectors (1, 1), (2, 0), and (2, 1), respectively. The tripling and quadrupling transformations applied to the regular dodecahedron generate achiral fullerene polyhedra with the full I
h
point group. However, the septupling transformation destroys the reflection operations of the underlying icosahedron to generate chiral fullerene polyhedra having only the I icosahedral rotational point group. Generalization of the quadrupling transformation leads to the fundamental homologous series of achiral fullerene polyhedra having 20 n
2 vertices and Goldberg vectors (n, 0). A related homologous series of likewise achiral fullerene polyhedra having 60 n
2 vertices and Goldberg vectors (n, n) is obtained by applying the tripling transformation to regular dodecahedral C20 to give truncated icosahedral C60 followed by the generalized operations (as in the case of quadrupling) for obtaining homologous series of fullerenes. Generalization of the septupling (capra) transformation leads to a homologous series of chiral C20m
fullerenes with the I point group and Goldberg vectors G=(h, 1) where m=h
2+h+1. 相似文献
135.
Amina Amassad Meir Shillor Mircea Sofonea 《Mathematical Methods in the Applied Sciences》1999,22(3):267-284
We consider a mathematical model which describes the bilateral quasistatic contact of a viscoelastic body with a rigid obstacle. The contact is modelled with a modified version of Coulomb's law of dry friction and, moreover, the coefficient of friction is assumed to depend either on the total slip or on the current slip. In the first case, the problem depends upon contact history. We present the classical formulations of the problems, the variational formulations and establish the existence and uniqueness of a weak solution to each of them, when the coefficient of friction is sufficiently small. The proofs are based on classical results for elliptic variational inequalities and fixed point arguments. We also study the dependence of the solutions on the perturbations of the friction coefficient and obtain a uniform convergence result. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
136.
Krzysztof Matyjaszewski Mircea Teodorescu Peter J. Miller Matthew L. Peterson 《Journal of polymer science. Part A, Polymer chemistry》2000,38(13):2440-2448
Poly(ethylene‐g‐styrene) and poly(ethylene‐g‐methyl methacrylate) graft copolymers were prepared by atom transfer radical polymerization (ATRP). Commercially available poly(ethylene‐co‐glycidyl methacrylate) was converted into ATRP macroinitiators by reaction with chloroacetic acid and 2‐bromoisobutyric acid, respectively, and the pendant‐functionalized polyolefins were used to initiate the ATRP of styrene and methyl methacrylate. In both cases, incorporation of the vinyl monomer into the graft copolymer increased with extent of the reaction. The controlled growth of the side chains was proved in the case of poly(ethylene‐g‐styrene) by the linear increase of molecular weight with conversion and low polydispersity (Mw /Mn < 1.4) of the cleaved polystyrene grafts. Both macroinitiators and graft copolymers were characterized by 1H NMR and differential scanning calorimetry. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2440–2448, 2000 相似文献
137.
138.
A new method is presented for fluorescent detection of amino-acids separated on silica gel R plates, by spraying with a 0.1% solution of 9-isothiocyanatoacridine derivatives in dichloromethane or benzene, heating and examining in ultraviolet light at 254 and 336 nm. This method is useful for routine analysis owing to its selectivity and sensitivity. 相似文献
139.
Paula Obreja Dana Cristea Elena Budianu Roxana Rebigan Victor Kuncser Mircea Bulinski George Filoti 《Progress in Solid State Chemistry》2006,34(2-4):103-109
This paper presents experimental results concerning the influence of the additives on the physical properties of polymer films. Metal oxides/inorganic salts were used as additives in vinyl-polymers solutions. The physical properties of the metal doped polymer films can be significantly modified by the composition of the doping elements and the curing conditions of the polymer. Morphologic, electronic, magnetic and optic properties of the doped polymers were analysed by AFM, SEM, Mössbauer spectroscopy and optical measurements. The film composition and the deposition processes were optimized to allow a better control of the optical parameters (refractive index, transmission), to reduce the processing temperatures and to improve the chemical sensitivity of the films for sensor applications. These compounds can be easily spin coated onto a variety of directly patterned semiconductor substrates. 相似文献
140.
Mircea Martin 《Proceedings of the American Mathematical Society》1998,126(10):2863-2871
A generalization to higher dimensions of a classical inequality due to Ahlfors and Buerling is proved. As a consequence, an extension of Alexander's quantitative version of Hartogs-Rosenthal Theorem is derived. Both results are stated and proved within the framework of Clifford analysis.