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41.
T. T. Bowman 《Semigroup Forum》1972,5(1):331-339
For a compact totally ordered space X, K. H. Hofmann and P. S. Mostert constructed a topological semigroup Irr (X)0 such that every compact irreducible semigroup with idempotents X is a surmorphic image of Irr (X)0 [2]. J. H. Carruth and M. Mislove pointed out that Irr (X)0 was in general not a compact semigroup. In this paper a compact connected hormos will be constructed which contains Irr (X)0 as a dense subsemigroup and for which every compact irreducible semigroup with idempotents X is a surmorphic image. This
leads to a new proof of the existence of generators for the category of compact irreducible semigroups with idempotents X.
It will then be shown that Irr (X)0 contains generators for the category. 相似文献
42.
Tien-Sung Lin Michael K. Bowman James R. Norris Gerhard L. Closs 《Chemical physics letters》1981,78(2):283-286
ENDOR frequencies of randomly oriented triplets have been measured from the fast Fourier transform of electron spin echo envelope modulation. Important experimental conditions are low temperatures, high microwave power and long phase memory time in a proper form of solvent. The technique is exemplified by using diphenylmethylenes in rigid glasses, polycrystalline forms and single crystals of benzophenones. 相似文献
43.
M.K. Bowman J.R. Norris M.C. Thurnauer J. Warden S.A. Dikanov Yu.D. Tsvetkov 《Chemical physics letters》1978,55(3):570-574
The electron spin echo envelope modulation of the chlorophyll a radical cation has been examined for radicals containing 14N and 15N. The modulation is found to be due primarily to the nitrogen nuclei in the heterocycle and the nuclear quadrupole interaction plays a large part in determining the modulation from 14N. The modulation from 15N allows limits to be set on the isotropic and anisotropic hyperfine interactions. 相似文献
44.
An analysis is given for the expansion (60 terms) of a gamma function ratio discussed by Stieltjes and others. A Stieltjes continued fraction is derived, affording lower and upper bound (but lacking a rigorous proof), along with continued fraction for the odd and even series. 相似文献
45.
46.
Kodibagkar VD Browning CD Tang X Wu Y Bowman RC Conradi MS 《Solid state nuclear magnetic resonance》2003,24(4):254-262
Powders of three hexagonal metal-hydrides or -deuterides are found to align in 4.4–8.3 T magnetic fields used for NMR. The field-alignment is unexpected, since all three systems have very small susceptibilities, as demonstrated by sharp NMR lines. The extent of alignment runs from nearly complete to barely detectable in ZrBe2(H,D)x, LuD3, and YD3, respectively. The preferred alignment direction in ZrBe2(H,D)x is with the crystallites’ c-axis perpendicular to B, while the c-axis and B tend to be parallel in LuD3 and YD3. The susceptibilities χ|| and χ are determined from bulk magnetization measurements in aligned ZrBe2H1.4 powder. The alignment must be considered for proper analysis of NMR spectra in these and related materials. 相似文献
47.
S.S. Roy C. Morros R.M. Bowman J.M. Gregg 《Applied Physics A: Materials Science & Processing》2005,81(4):881-885
Strongly oriented thin films of lead zinc niobate (PZN)–lead zirconium titanate (PZT) with (La,Sr)CoO3 lower electrodes were grown on MgO {001} substrates by pulsed laser deposition. The films were perovskite-dominated with strong in-plane and out-of-plane orientations. Room-temperature functional characterisation indicated that the films were ferroelectric, with dielectric constant ∼550 and loss tangent ∼0.08 at 1 kHz. The crystallographic strain, as a function of applied dc field, was monitored by in situ X-ray diffraction. The maximum electric-field-induced crystallographic strain (∼0.22%) was comparable to that observed in bulk, but at significantly greater field (∼150 kV cm-1). The effective d33 value obtained from the crystallographic strain data was around 150 pm V-1, which is high for ferroelectric thin films 400 nm in thickness. The local polarisation-switching properties of the films were investigated using a piezo-response atomic force microscope. Domain maps for a 5×5 μm2 region of material were recorded as a function of dc bias, and confirmed the ferroelectric switching behaviour. PACS 81.05.Je; 81.40.Vw; 68.37.Lp 相似文献
48.
Harini Kilambi Sirish K. Reddy Lauren Schneidewind Jeffrey W. Stansbury Christopher N. Bowman 《Journal of polymer science. Part A, Polymer chemistry》2009,47(19):4859-4870
The impact of secondary functionalities on the radical‐vinyl chemistry of monoacrylates characterized by secondary functionalities that dramatically enhance their polymerization rate was elucidated utilizing experimental and computational techniques. Firstly, bulk interactions affecting the acrylate reactivity towards photopolymerization were removed by polymerizing at 5 wt % monomer in 1,4‐dioxane. Following deconvolution of bulk interactions impacting reactivity towards photopolymerization, a linear correlation between average polymerization rates and Michael addition reaction rate constants was observed on a logarithmic scale. This result indicates that the presence of the secondary functionality intramolecularly alters the monomer chemistry in a manner which impacts both of these distinct reaction types in a similar manner. These monomers exhibited reduced activation energies in both Michael addition and photopolymerization reactions as compared to hexyl acrylate. Reduction up to 20 ± 8 kJ mole?1was observed for Michael addition reactions and 12 ± 1 kJ mole?1 for photopolymerization reactions, thereby explaining the higher reactivity of the acrylates characterized by the secondary functionalities. Cyclic voltammetry experiments conducted to investigate the nature of the acrylic double bonds indicated that the rapidly polymerizing acrylates are more readily reduced as compared to traditional acrylates. Further, a distinct monotonic correlation of the irreversible cathodic peak potentials of the (meth)acrylates to photopolymerization and Michael addition reactivity was observed. The computationally estimated acrylic LUMO energies characterized by the secondary functionalities (?2.3 eV to ?2.7 eV) were also found to be lower relative to hexyl acrylate (?2.2 eV). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4859–4870, 2009 相似文献
49.
Venkatesh Vasudevan Robert D. Cook Ronald K. Hanson Craig T. Bowman David M. Golden 《国际化学动力学杂志》2008,40(8):488-495
The reaction between methyl and hydroxyl radicals has been studied in reflected shock wave experiments using narrow‐linewidth OH laser absorption. OH radicals were generated by the rapid thermal decomposition of tert‐butyl hydroperoxide. Two different species were used as CH3 radical precursors, azomethane and methyl iodide. The overall rate coefficient of the CH3 + OH reaction was determined in the temperature range 1081–1426 K under conditions of chemical isolation. The experimental data are in good agreement with a recent theoretical study of the reaction. The decomposition of methanol to methyl and OH radicals was also investigated behind reflected shock waves. The current measurements are in good agreement with a recent experimental study and a master equation simulation. © 2008 Wiley Periodicals, Inc. 40: 488–495, 2008 相似文献
50.