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91.
92.
S. A. Liebman D. H. Ahlstrom W. H. Starnes JR. F. C. Schilling 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):935-950
This study compares the use of pyrolysis hydrogenation gas chromatography (PHGC) and 13C Fourier transform nuclear magnetic resonance (FTNMR) methods for the analysis of reference polyethylene (PE) samples, ethylene-α-olefin copolymers, and specially prepared poly(vinyl chloride) (PVC) samples which were reduced to their PE skeletal structures. The nature and relative quantities of the short branches along the polymer chains were determined using both techniques. Improved high-resolution PHGC data, obtained with a fused silica capillary separation column, gave results which were in satisfactory agreement with the 13C FTNMR data. This approach confirms that detailed microstructural information can be obtained with these methods by using carefully controlled experimental conditions and appropriate reference systems. 相似文献
93.
The tentative identification of the reactive species in the condensation of Cp2 TiCl2 with salts of diacids to form titanium polysters is made. The reactive species are believed to be the same for both aqueous solution and interfacial systems, i.e., R -CO2 ? and Cp2 Ti2+ with reaction occurring in the aqueous phase. The condensation of Cp2 TiCl2 with disodium terephthalate in interfacial systems occurs via a pseudo-first-order reaction: Rate = K[Cp2 TiCl2] The rate-determining step (s) is believed to be diffusion of CP2 TiCl2 into the aqueous layer and/or hydrolysis of Cp2 TiCl2 相似文献
94.
Simple analytical expansions are given for the recoilless fraction in Mössbauer spectroscopy, the Debye-Waller factor in X-ray scattering, and the lattice energy and heat capacity of solids. While this problem has been discussed in an earlier paper [1], computer technology has now advanced to the point that direct evaluations of the simple expansions of these quantities are useful for quick curve fitting to experimental data at any desired temperature, and these expansions are easier to evaluate than using graphs to estimate recoilless fractions and Debye temperatures. We compare this approach with a polynomial expansion in terms of Bernoulli numbers, which has only a limited domain of convergence. We explicitly evaluate the convergence of these Debye integral expansions as a function of the number of terms used and the time required.This work was prepared with the support of the U.S. Department of Energy, Grant No. DE-FG02-85 ER 45199. 相似文献
95.
OVERSTREET GEORGE A. JR; BREDLEY EDWIN L. JR 《IMA Journal of Management Mathematics》1996,7(4):291-311
Although credit-scoring models represent a widely used managerialaid for large financial intermediaries, the vast majority ofU.S. credit unionsrelatively small cooperatively ownedretail intermediaries, constrained by sample and funding limitationshaveyet to adopt such techniques. Lovie & Lovie (1986) havetheorized that the flat-maximum effect or curve of insensitivityassociated with linear scoring models could be advantageousin areas of applied prediction such as credit scoring. In thiscontext, we reported the relative predictive power of genericcredit-scoring models versus customized models in an earlierpaper (Overstreet et al. 1992). Unfortunately, these findingswere not readily adaptable to the credit-union industry dueto a dated sample with incomplete credit-bureau information.Consequently, from 1988 to 1991, we gathered a refined databasefrom which to further develop and field-test generic scoringmodels in the credit-union environment. The results reportedherein not only confirm, but amplify, the relative predictivepower of such models found earlier. Relative costs and benefitsof generic versus customized models are modelled for a representativecredit union. Future research directions are set forth in theconclusions. 相似文献
96.
P.W. Heitman L.A. Shepard T.H. Courtney 《Journal of the mechanics and physics of solids》1973,21(2):75-89
The effect of brittle intermetallic compounds at the fiber-matrix interface on the deformation characteristics of molybdenum-aluminum fiber composites was investigated. If the filament is ductile and notch-insensitive, then composite strength degradation is relatively minor and composite strength can be predicted by a modified mixture-rule which neglects the strength contribution of the brittle compound. For the case of notch-sensitive filaments, severe filament degradation occurs upon compound formation. The degradation was shown to result from cracks formed during deformation at the roots of compound nodules. The presence of 10 per cent compound by volume results in a 50 per cent decrease in tensile strength, but larger amounts of compound cause little additional strength reduction. At filament volume fractions of 25 and 34 per cent and compound volume fractions less than 10 per cent, composite fracture occurs by the statistical accumulation of fiber necks or fractures depending on the notch sensitivity of the fiber. At high fiber or compound volume fractions, composite failure occurs upon the first or the second filament fracture. 相似文献
97.
98.
We construct the optimally-weighted dispersion relation and extrapolation error for an amplitude with unequal, possibly correlated, errors in the experimental boundary values of its real and imaginary parts. The uniqueness of the optimally-weighted dispersion relation is demonstrated. 相似文献
99.
100.
Ron Shepard Scott R. Brozell Gergely Gidofalvi 《Journal of computational chemistry》2020,41(2):129-135
The Shavitt graph is a visual representation of a distinct row table (DRT) within the graphical unitary group approach. The DRT is a compact representation of the entire configuration state function expansion space within a molecular electronic structure calculation. Each node of the graph is associated with an integer triple (a k,b k,c k). These integers may be mapped to other quantum numbers, including the number of orbitals, number of electrons, and spin quantum number, and used to display Shavitt graphs in various ways that emphasize different aspects of the expansion space or that reveal different aspects of computed wave functions. The features of several graph density plots are discussed, including electron–hole symmetries and the bonding–antibonding wave function character. © 2019 Wiley Periodicals, Inc. 相似文献