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41.
Hideyuki Higashimura Kiyoshi Fujisawa Shuhei Namekawa Masaaki Kubota Akinobu Shiga Yoshihiko Moro‐Oka Hiroshi Uyama Shiro Kobayashi 《Journal of polymer science. Part A, Polymer chemistry》2000,38(Z1):4792-4804
Various effects on the coupling selectivity of the oxidative polymerization of 4‐phenoxyphenol catalyzed by (1,4,7‐triisopropyl‐1,4,7‐triazacyclononane)copper(II) halogeno complex [Cu(tacn)X2] are described. With respect to the amount of the catalyst and the nature of the halide ion (X) of Cu(tacn)X2, the coupling selectivity hardly changed. The Cu(tacn) catalyst possessed a turnover number greater than 1860. As the temperature of the reaction and the polarity of the reaction solvent were elevated, the C O coupling at the o‐position increased, but the C C coupling was not involved. For the polymerization in toluene at 80 °C, poly(1,4‐phenylene oxide), obtained as a methanol‐insoluble part, showed the highest number‐average molecular weight of 4000 with a melting point (Tm) of 195 °C. Only a slight change in the coupling selectivity was observed in the presence or absence of hindered amines as the base. Surprisingly, however, the C O selectivity decreased from 100 to 24% with less hindered amines, indicating that the selectivity drastically changed from a preference for C O coupling to a preference for C C coupling. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4792–4804, 2000 相似文献
42.
Motoyuki Shiga Fumihiko Aiga Kotoku Sasagane 《International journal of quantum chemistry》1999,71(3):251-271
As a formulation for calculating the dynamic polarizabilities and hyperpolarizabilities, two different types of the time‐dependent Møller–Plesset perturbation theory (MPPT) are presented: the MPPT in the quasienergy derivative method (QED–MPPT) and the MPPT in the energylike derivative method (ELD–MPPT). The explicit expressions for the response properties in each of these MPPT up to the quadratic response [μ, α(−ω1, ω1), β(−ωσ, ω1, ω2)] at an arbitrary correlated order are given. Calculations of the dynamic polarizabilities and hyperpolarizabilities dependent on one frequency at the second‐order MPPT (MP2), in the QED method (QED–MP2) and in the ELD method (ELD–MP2), are examined for 10‐electron systems: hydrogen fluoride and neon. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 71: 251–271, 1999 相似文献
43.
Jinfeng Yang Koichi Kan Nobuyasu Naruse Yoichi Yoshida Katsumi Tanimura Junji Urakawa 《Radiation Physics and Chemistry》2009,78(12):1106-1111
A near-relativistic 100-fs MeV electron beam is developed by using a photocathode rf gun for revealing the hidden ultrafast dynamics of intricate molecular and atomic processes in materials through experimentation of ultrafast time-resolved electron diffraction (UED). The transverse and longitudinal dynamics of femtosecond electron beam in the rf gun were studied theoretically by particle simulation. The growths of the emittance, bunch length and energy spread due to the rf and space charge effects were investigated by changing the laser parameters, field gradient and electron charge. The theoretical studies indicate that a 100-fs MeV electron beam with the transverse emittance of 0.1 mm mrad and the relative energy spread of 10−3–10−4 at bunch charge of 0.1–2 pC (106–107 electrons per pulse) is achievable for UED, in which the intensity is three orders of magnitude higher than that produced by the conventional dc or pulsed guns. 相似文献
44.
In order to investigate the HD isotope effect on a dihydrogen bonded cation system, we have studied NH+4...BeH2 and its isotopomers by ab initio path integral molecular dynamics. It is found that the dihydrogen bond can be exchanged by NH+(4) rotation. The deuterated isotopomer (ND+(4)...BeD(2); DD) can exchange the dihydrogen bond more easily than other isotopomers such as (NH+4...BeH2; HH). This unusual isotope effect is ascribed to the "quantum localization" which occurs when the effective energy barrier for the rotational mode becomes higher by the zero point energy of other modes. We also found that the binding energy of dihydrogen bonds for DD species is the smallest among the isotopomers. 相似文献
45.
Summary We consider two classes of measure-valued diffusion processes; measure-valued branching diffusions and Fleming-Viot diffusion
models. When the basic space is R
1, and the drift operator is a fractional Laplacian of order 1<α≦2, we derive stochastic partial differential equations based
on a space-time white noise for these two processes. The former is the expected one by Dawson, but the latter is a new type
of stochastic partial differential equation. 相似文献
46.
M. Mekata T. Asano H. Nakamura M. Shiga K. Kojima G.M. Luke A. Keren W.D. Wu Y.J. Uemura S. Dunsinger M. Gingras 《Hyperfine Interactions》1997,104(1-4):337-342
The relaxation rate of muon polarization of Y0.97Sc0.03Mn2 with a magnetic lattice composed of corner‐shared tetrahedrons shows a broad peak around 2.5 K indicating a random spin freezing
at low temperatures. The substitution by nonmagnetic Al atoms for 10% Mn atoms raises the spin freezing temperature to 45
K. The present work shows clearly that due to the strong geometrical frustration, the ground state of the system is singlet
tetrahedrons mixed with frozen paramagnetic tetrahedrons.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
47.
Finite and Infinite Systems of Interacting Diffusions: Cluster Formation and Universality Properties
We study some aspects of the relationship between the long time behaviour of systems with a finite but large number of components and their idealizations with countably many components. The following class of models is considered in detail, which contains examples occuring in population growth and population genetic models. 相似文献
48.
To investigate the proton/deuteron geometrical isotope effect of positively and negatively charged water complexes, H5O2+ and H3O2-, we have carried out accurate ab initio path integral simulations considering the electron correlation effect. It has been found that the isotope effect on the hydrogen bond is different between these two species in that the oxygen separation becomes shorter in H5O2+ while longer in H3O2- by deuteron substitution. This behavior is ascribed to the change in the quantum effect of hydrogen bonds whether the shared hydrogen is on a single or double well potential surface. 相似文献
49.
Nobuyasu Itoh Takamitsu Otake Yoshie Aoyagi Mayumi Matsuo Takashi Yarita 《Chromatographia》2009,70(7-8):1073-1078
We applied liquid chromatography-dopant-assisted atmospheric pressure photoionization-mass spectrometry to quantify four distinct pesticides (isoprothiolane, fenitrothion, fthalide, and ethophenprox) in unpolished rice flour. Although the effect of acetone as a dopant on enhancement of ionization differed among the pesticides, the analytical results by LC-DA-APPI-MS with a dopant flow rate of 50 μL min?1 were not only repeatable (relative SD < 9%, n = 3) but also comparable to those by gas chromatography–mass spectrometry. 相似文献
50.