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81.
82.
The application of high-field Fourier transform nuclear magnetic resonance (NMR) spectroscopy to the analysis of biological fluids such as urine, plasma and bile is described. Applications include areas such as clinical chemistry, experimental and clinical toxicology and drug metabolism studies. In the case of proton NMR some means of attenuating or eliminating the interference due to water protons is required and suitable strategies for achieving this are discussed. The use of 2-dimensional NMR or solid-phase extraction/chromatography to enable the identification of unknowns is discussed and the potential usefulness of 19F NMR for studying the metabolism of fluorinated xenobiotics is highlighted. 相似文献
83.
84.
J.P. Nicholson 《Optics Communications》1979,29(1):49-50
Fabry-Perot frequency measurements of FIR superradiant emission from D2O at 99 μm are reported. Several Fabry-Perot scans at different frequency settings of the CO2 pump laser show a shift in the FIR output spectrum equal, within experimental error, to the shift in input frequency of the CO2 pump. The “superradiant” emission therefore of the D2O 101,10(010) → 90,9(010) transition at 99 μm contains a strong Raman component. 相似文献
85.
The Shelton retarding field method has been employed to determine the thermionic constants of the (100) surface of tantalum in the temperature range 1500 to 1730 K: φ* = = 4.16 ± 0.05 V, dφdT= 56 ± 5 μ V/K, and AR = 122 ± 26 A/cm2K2.φ = 4.24 ± 0.05 V at300 K. A refined analysis of the Shelton method shows the importance of four reflection coefficients, because of which, AR cannot be identified unambiguously as the preexponental constant appearing in the Richardson equation. The dependence on incident energy of the electron reflection coefficient of Ta(100) was observed in the range 0–100 eV. The positions at 4.5, 8.0, 11.3, and 17.0 eV of relative reflection maxima agree closely with those observed by others for W(100). Advances are described in instrumentation, in experimental technique, and in acquisition and analysis of data. 相似文献
86.
R.T. Poole J.A. Nicholson J.G. Jenkin R.C.G. Leckey J.B. Peel J. Liesegang 《Journal of Electron Spectroscopy and Related Phenomena》1979,15(1):91-94
A photoelectron study of the outermost bands of solid-phase SnCl2 and SnBr2 using 40.81 eV photons is reported. The main features of the spectra are successfully interpreted in terms of molecular orbital theory for the appropriate isolated molecules. 相似文献
87.
K β′-alumina is unstable at >1300°C. Mixed alkali β′-alumina has a variable stability depending on the alkali ratio, [K+]/([Na+]+[K+]). For f(β)<[K+]/([Na+]+[K+]), the β′-Al2O3 phase decomposes to Kβ-Al2O3 0997 0815 V 3 and a solid solution of Na β′-Al2O3 and K β′-Al2O3. For f(β)=[K+]/([Na+]+[K+], the ceramic consists of K β-Al2O3 and Naβ′-Al2O3 and for f(β)>[K+]/([Na+]+[K+]), the excess Na+ after Na β′-Al2O3 dissolves in the β phase, giving Na β-Al2O3/K β-Al2O3 solid solution and Na β′-Al2O3. These sequences were confirmed by measuring the dependence of the c-axis lattice parameters of β- and β′-Al2O3 phases on the f(β), and the change of these parameters during the ion-exchange of Na+ and K+ ions. 相似文献
88.
The stationary response of a broad class of combined linear systems to stationary random excitation is determined by the normal mode method. The systems are characterized by a viscously damped simple beam (or string, membrane, thin plate or shell, etc.) connected at discrete points to a multiplicity of viscously damped linear oscillators and/or masses. The solution of the free vibration problem by way of Green functions and the deterministic forced vibration problem by modal analysis for both proportional and non-proportional damping is reviewed. The orthogonality relation for the natural modes of vibration is used to derive a unique relationship between the cross-spectral density functions of the applied forces and the cross-spectral density functions of the generalized forces. Finally, the response spectral density functions and the mean square responses of the beam and oscillators are derived in closed form, exact for the proportionally damped system and approximate for the non-proportionally damped system. 相似文献
89.
LetR be an associative ring with identity which satisfies the identities(xy)
k
=(yx)
k
and(xy)
l
=(yx)
l
, wherek andl are relatively prime positive integers, depending onx andy. ThenR is commutative. Moreover, examples are given which show thatR need not be commutative if either of the above identities is dropped. This theorem is also true for groups.
Presented by N. S. Mendelsohn. 相似文献
90.