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91.
Pawel Uznanski Agnieszka Walkiewicz-Pietrzykowska Krzysztof Jankowski Joanna Zakrzewska Aleksander M. Wrobel Jacek Balcerzak Jacek Tyczkowski 《应用有机金属化学》2020,34(8):e5674
Amorphous silicon oxycarbide (a-SiOC:H) films produced by remote plasma RPCVD from diethoxymethylsilane (DEMS) were characterized in terms of their basic properties related to the coatings deposited using conventional plasma enhanced PECVD method. The effect of substrate temperature (TS) on the growth rate, chemical composition, structure, and properties of resulting a-SiOC:H films is reported. Film growth is an adsorption-controlled process, wherein two mechanisms can be distinguished with a transition at about TS=70°C. Depending on the temperature, films of different nature can be obtained, from polymer-like to highly crosslinked material with C-Si-O network. The chemical structure of a-SiOC:H films was characterized by FTIR, 13C and 29Si solid-state NMR, and X-ray photoelectron spectroscopes. The a-SiOC:H films were also characterized in terms of their density, refractive index, surface morphology, conformality of coverage, hardness, adhesion to a substrate, and friction coefficient. The films were found to be morphologically homogeneous materials exhibiting good conformality of coverage and small surface roughness. Their refractive index exhibits anomalous effect revealing a minimum value at TS=125°C. Due to their exceptional physical properties a-SiOC:H films produced by RPCVD from DEMS precursor seems to be useful as potential dielectric materials or coatings for various encapsulation applications. 相似文献
92.
93.
94.
On Cubic Graphs Admitting an Edge-Transitive Solvable Group 总被引:2,自引:2,他引:0
Aleksander Malnič Dragan Marušič Primož Potočnik 《Journal of Algebraic Combinatorics》2004,20(1):99-113
Using covering graph techniques, a structural result about connected cubic simple graphs admitting an edge-transitive solvable group of automorphisms is proved. This implies, among other, that every such graph can be obtained from either the 3-dipole Dip3 or the complete graph K
4, by a sequence of elementary-abelian covers. Another consequence of the main structural result is that the action of an arc-transitive solvable group on a connected cubic simple graph is at most 3-arc-transitive. As an application, a new infinite family of semisymmetric cubic graphs, arising as regular elementary abelian covering projections of K
3,3, is constructed. 相似文献
95.
For 1/2<<1 fixed, letE
(T) denote the error term in the asymptotic formula for
. We obtain some new bounds forE
(T), and an _-result which is the analogue of the strongest _-result in the classical Dirichlet divisor problem. 相似文献
96.
Aleksander Simonic 《Transactions of the American Mathematical Society》1996,348(3):975-995
The aim of this work is to generalize Lomonosov's techniques in order to apply them to a wider class of not necessarily compact operators. We start by establishing a connection between the existence of invariant subspaces and density of what we define as the associated Lomonosov space in a certain function space. On a Hilbert space, approximation with Lomonosov functions results in an extended version of Burnside's Theorem. An application of this theorem to the algebra generated by an essentially self-adjoint operator yields the existence of vector states on the space of all polynomials restricted to the essential spectrum of . Finally, the invariant subspace problem for compact perturbations of self-adjoint operators acting on a real Hilbert space is translated into an extreme problem and the solution is obtained upon differentiating certain real-valued functions at their extreme.
97.
Wojciech P. Ozimi
ski Jan Cz. Dobrowolski Aleksander P. Mazurek 《Journal of Molecular Structure》2004,680(1-3):107-115
DFT (B3LYP/6-311++G**, B3PW91/6-311++G**) Gibbs free energy and single point CCSD(T)/6-311++G**//DFT total energy calculations were performed to investigate stability and tautomerism of C5-substituted 1,2,4-triazoles. Three different tautomers are possible for the substituted 1,2,4-triazoles: N1–H, N2–H, and N4–H. Unlike for the 1,2,3-triazoles, where the most stable is the N2–H tautomer regardless of substituent applied, for the 1,2,4-triazoles, the electron donating substituents (–OH, –F, –CN, –NH2, and –Cl) and the C5-cation stablize the N2–H tautomer, whereas the electron withdrawing substituents (–CONH2, –COOH, –CHO, –BH2, and –CFO) and the C5-anion stablize the N1–H tautomer. Except for the C5-anion and C5-cation, the N4–H form is the least stable tautomer. The relative stability of the C5-substituted 1,2,4-triazole tautomers is strongly influenced by attractive and/or repulsive intramolecular interactions between substituent and electron donor or electron acceptor centres of the triazole ring. 相似文献
98.
At the dissolution of anhydrous bismuth(III) trifluoromethanesulfonate in N,N-dimethylthioformamide (DMTF) a deep red-orange complex, lambda(max) = 457 nm, is formed. Bismuth(III) is reduced by the solvent to a low-valent oxidation state stabilized by the sulfur-coordinating solvent DMTF. The obtained complex is weakly solvated seen by a low EXAFS amplitude and a slightly higher absorption energy of the L(III) edge than of the DMTF-solvated bismuth(III) ion. The EXAFS data reveal a dimeric bismuth complex solvated by a single DMTF molecule, which sulfur atom bridges the bismuth atoms. The Bi-S bond distance is 2.543(2) A, and the Bi...Bi distance is 3.929(7) A giving a Bi-S-Bi angle of 101.2(4) degrees. The very low number of coordinated solvent molecule shows that the lone electron pairs of the reduced bismuth ions are stereochemically active. Cyclic voltammetry investigations provide evidence that at least one bismuth atom in the dimer exists in an oxidation state lower than +III, seen by two peaks at approximately -0.36 and -0.57 V in the reduction half-cycle. The absence of EPR signals excludes the presence of bismuth(II) radicals. 相似文献
99.
Dominiak PM Filarowski A Hansen PE Woźniak K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(16):4758-4766
We have analyzed deuterium isotope effects on (13)C chemical shifts in a series of o-hydroxy Schiff bases by applying factor analysis. Two orthogonal factors were obtained that explain about 80 and 10 % of the variance of the data. The numerical values of these factors can be related to 1H NMR chemical shifts of the proton involved in the intramolecular bonds delta(XH) (X = O or N). Such a relation allows one to identify clusters of compounds with different tautomeric forms of hydrogen bonding. Application of a similar approach to solution 13C NMR chemical shifts produces three important factors, which have a different structure to factors describing isotope effects. This illustrates well the different nature of chemical shifts and isotope effects. The three factors explain about 54, 15, and 13 % of variance. They can be rationalized and are strongly related to the electronic properties and location of substituents. 相似文献
100.
Tat''yana V. Baukova Lyudmila G. Kuz''mina Natal''ya A. Oleinikova Dmitrii A. Lemenovskii Aleksander L. Blumenfel''d 《Journal of organometallic chemistry》1997,530(1-2):27-38
Two organogold derivatives of diphenylmethane and diphenylethane, Ph3PAu(o-C6H4)CH2(C6H4-o)AuPPh3 (1) and Ph3PAu(o-C6H4)(CH2)2(C6H4-o)AuPPh3 (2), have been synthesized by the reaction of ClAuPPh3 with Li(o-C6H4)CH2(C6H4-o)Li and Li(o-C6H4)(CH2)2(C6H4-o)Li respectively. The interaction of 1 with dppe results in the replacement of the two PPh3 groups to give a macrocyclic compound (3) that includes an Au Au bond. Compounds 1 and 2 react with one or two equivalents of [Ph3PAu]BF4 to form new types of cationic complex [CH2(C6H4-o)2(AuPPh3)3]BF4 (4), [CH2(C6H4-o)2(AuPPh3)4](BF4)2 (5), and [(CH2)2(C6H4-o)2(AuPPh3)4](BF4)2 (6). Complexes 1–6 have been characterized by X-ray diffraction studies, FAB MS, and IR as well as by 1H and 31P NMR spectroscopy. A complicated system of Au H-C agostic interactions, involving the bridging alkyl groups (—CH2— and CH2-CH2—) of diphenylmethane and diphenylethane ligands, has been found to occur in complexes 1–3 and 6. 相似文献