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排序方式: 共有141条查询结果,搜索用时 31 毫秒
51.
V. Rizzi G. Viesti D. Bazzacco A. Algora-Pineda D. Appelbe G. de Angelis N. Belcari M. Cinausero M. De Poli T.E. Drake A. Gadea A. Galindo-Uribarri N. Gelli D. Fabris E. Farnea E. Fioretto W. Krolas T. Kroll F. Lucarelli S. Lunardi M. Lunardon T. Martinez R. Menegazzo B.K. Nayak G. Nebbia D.R. Napoli B. Nyakó C. Petrache Zs. Podolyák G. Prete C. Rossi Alvarez A. Samant P. Spolaore C. Ur K. Zuber 《The European Physical Journal A - Hadrons and Nuclei》2000,7(3):299-301
The ridge structure with ΔEγ=±30 keV, observed in the past in coincidence with protons emitted in the reaction 187 MeV 37Cl +120Sn and attributed to an hyperdeformed nuclear shape in 152Dy, has been studied in a new experiment performed with the EUROBALL III array. The ridge is now observed in coincidence with
transitions in the yrast superdeformed band of 152Dy but no discrete rotational bands have been identified.
Received: 7 February 2000 相似文献
52.
A.M. Samant S. Kailas A. Chatterjee A. Shrivastava A. Navin P. Singh 《The European Physical Journal A - Hadrons and Nuclei》2000,7(1):59-64
The fission fragment angular distributions have been measured for the system 19F +209Bi over a range of bombarding energies from 88.0 MeV to 125.6 MeV. The measured fission fragment anisotropies are in agreement
with the saddle point statistical model calculations in the above energy range. Combining these data with those available
for 11B, 12C, 14N, 16O and 18O +209Bi, 208Pb systems, it is concluded that the spherical target plus projectile systems behave “normal” from near- to above – barrier
energies. This observation is in contrast to the “anomalous” anisotropies exhibited by the deformed actinide target – projectile
systems at near – barrier energies.
Received: 5 May 1999 / Revised version: 25 July 1999 相似文献
53.
The oxidation of ethylenediamine by diperiodatoargentate (III) ion has been studied by stopped‐flow spectrophotometry. Kinetics of this reaction involves two steps. The first step is the complexation of silver (III) with the substrate and is over in about 10 ms. This is followed by a redox reaction in the second step that occurs intramolecularly from the substrate to the silver (III) center. The rate of reduction of silver (III) species by ethylenediamine, ethanolamine, and 1,2‐ethanediol were observed to be 1.2 × 104, 1.1 × 102, and 0.14 dm3 mol−1 s−1, respectively, at 20°C. The reaction rate shows an inverse dependence on [IO] and [OH−] in the low concentration range (≤1 × 10‐3 mol dm−3). At higher [OH−] (>1 × 10−3 mol dm−3) the rate of reaction starts increasing and attains a limiting value at very high [OH−]. The rate of deamination of ethylenediamine is enhanced by its complexation with silver (III). The involvement of [AgIII(H2IO6) (H2O)2] and [AgIII(H2IO6) (OH)2]2− are suggested as the reactive silver (III) species kinetically in mild basic and basic conditions, respectively. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 286–293, 2000 相似文献
54.
55.
David P. Young Robin G. Melvin Michael B. Bieterman Forrester T. Johnson Satish S. Samant 《国际流体数值方法杂志》1990,11(8):1075-1095
In computational fluid dynamics, non-linear differential equations are essential to represent important effects such as shock waves in transonic flow. Discretized versions of these non-linear equations are solved using iterative methods. In this paper an inexact Newton method using the GMRES algorithm of Saad and Schultz is examined in the context of the full potential equation of aerodynamics. In this setting, reliable and efficient convergence of Newton methods is difficult to achieve. A poor initial solution guess often leads to divergence or very slow convergence. This paper examines several possible solutions to these problems, including a standard local damping strategy for Newton's method and two continuation methods, one of which utilizes interpolation from a coarse grid solution to obtain the initial guess on a finer grid. It is shown that the continuation methods can be used to augment the local damping strategy to achieve convergence for difficult transonic flow problems. These include simple wings with shock waves as well as problems involving engine power effects. These latter cases are modelled using the assumption that each exhaust plume is isentropic but has a different total pressure and/or temperature than the freestream. 相似文献
56.
F. J. Himpsel H. Akatsu J. A. Carlisle D. G. J. Sutherland I. Jimenez L. J. Terminello J. J. Jia T. A. Callcott M. G. Samant J. Sthr D. L. Ederer R. C. C. Perera W. Tong D. K. Shunh 《Progress in Surface Science》1995,50(1-4):37-51
A third generation of synchrotron radiation facilities is coming on line worldwide, whose brilliance exceeds previous ultraviolet and x-ray light sources by four orders of magnitude. The capabilities at second and third generation light sources are discussed, using examples in surface and interface chemistry and magnetic nanostructures. The authors' experience at the IBM-Tennessee-Tulane-LLNL-LBL undulator beam line will serve as a hands-on guide for work at one of the new facilities. 相似文献
57.
Elastic and inelastic scatterings cross-sections of12C+12C in the energy range 11–24 MeV/n have been analyzed within the coupled channels framework including appropriate symmetrization. The set obtained withr 0=1.01 fm,r I =0.86 fm for seven incident energies gave the best agreement with the data and could be, therefore, considered as really significant when compared with other sets. Coupled channels calculations have been made to fit the data and it has been found that they require a reduction of the imaginary potential. The total reaction cross-sectionσ R (E) determined from this analysis is in good agreement with a direct and recent measurement of σ R . Quadrupole deformation parameterβ 2 has been extracted and compared with those obtained for proton and alpha scatterings. Some small energy dependence of β2 over this energy range has been found, ¦β 2¦ ~0.39–0.47. Finally, these calculations further confirm that β2 depends on the probe used in the various scattering experiments. For composite projectile such asα or12C,β 2 is clearly smaller than that one for nucleon as projectile. 相似文献
58.
59.
Vaishali Samant Ajay K. Singh Tulsi Mukherjee Dipak K. Palit 《Radiation Physics and Chemistry》2005,72(6):711-722
Electron pulse radiolysis of four differently substituted amino derivatives of fluorenone, namely, 1-amino-, 2-amino- 3-amino-, and 4-aminofluorenone, has been carried out to study the effect of structure on the spectroscopic and kinetic characteristics of the triplet excited states as well as the transient free radical intermediates formed under reducing and oxidizing conditions. The triplet states of these compounds have been generated in benzene by pulse radiolysis and in other solvents by flash photolysis technique and their spectral and kinetic properties have been investigated. Hydrated electron (eaq−) has been found to react with these fluorenone derivatives to form the anion radical species with a diffusion-controlled rate constant. The spectral and kinetic properties of the transient ketyl and anion radicals have been studied by generating them in aqueous solutions of suitable pH. The pKa values of ketylanion radical equilibria are in the range of 6.8–7.7 for these derivatives. The oxidized species have been generated by reaction with the azide radical. Hydrogen atom adducts as well as the cation radicals of these derivatives have also been generated by pulse radiolysis and characterized. 相似文献
60.
Self-assembling, cystine-derived, fused nanotubes based on spirane architecture: design, synthesis, and crystal structure of cystinospiranes 总被引:1,自引:0,他引:1
A novel family of cystine-based spirobicyclic peptides (cystinospiranes) has been synthesized by a single-step procedure involving condensation of pentaerythritol-derived tetrachloride with either the simple L-cystine dimethyl ester or its C,C'-extended bispeptides leading to a variety of 19-membered spirobicyclic peptides or its N,N'-extended bispeptides affording the ring-expanded 25-membered cystinospiranes. The design is flexible with respect to the ring size that can be adjusted depending upon the length of the N,N'-extended cystine bispeptide, and the choice of an amino acid, as illustrated here with the preparation of a large number of cystinospiranes containing a wide variety of amino acids. X-ray crystal structure of the parent spirane (5a) revealed nanotube formation by vertical stacking of relatively flat spirobicyclic molecules through contiguous NH- - -O==C hydrogen bonding. The fused pair of parallel nanotubes is open-ended, hollow, and extends to infinity. Crystallographic parameters are the following: C(33)H(52)N(4)O(16)S(4), space group C2, a = 42.181(3) A, b = 5.1165(7) A, c = 11.8687(9) A, beta = 106.23(1) degrees. 相似文献