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101.
102.
Ultrafine amorphous alloy particles of (Fe1-x Cox)60B40 with x=0.1, 0.3, 0.5, 0.7, and 0.9 have been prepared by reduction of the metal ions using KBH4 in aqueous solution. electron microscopy shows that the particle size is of the order of 20 nm. Mössbauer spectroscopy has been used to elucidate the magnetic properties of the particles. 相似文献
103.
104.
Samples of two types of natural basalt were equilibrated over a range of oxygen pressures at four different temperatures, and then quenched to room temperature. Except at the lowest temperature, where magnetic crystals formed under the most oxidizing conditions, totally amorphous samples were obtained. The Mössbauer spectra of 45 samples of the quenched basaltic melts were measured at room temperature. The relationship obtained between the oxidation state and oxygen fugacity differs to some extent from those relations previously described in the literature, in not yielding a linear relationship between log(farric/ferrous) and log(fo2). This might indicate a more involved redox process than that described by a simple reaction between oxides and/or the influence of the cation composition in the process of glass formation. An investigation was made of the kinetics of the redox process. For the experimental setup used, redox equilibrium would be reached within three hours. Finally, three naturally quenched basalt glasses were analyzed for comparison; two showed lower oxidation states than previously found in Icelandic rocks. 相似文献
105.
Samples of human faeces from patients suffering from intestinal bleeding have been studied by use of Mössbauer spectroscopy. It is shown that it is possible to follow the degradation of blood in the digestive tract. 相似文献
106.
Morten B. Madsen Steen Mørup Christian J. W. Koch Gertrud Lindemann 《Hyperfine Interactions》1986,29(1-4):1431-1434
The nature of the iron-containing phase in the dental enamel of sump beaver incisors has been studied by use of Mössbauer spectroscopy. All iron atoms are found to be trivalent and to be present in particles exhibiting superparamagnetic relaxation. The iron-containing phase has Mössbauer parameters similar to those of ferritin. 相似文献
107.
108.
Vase KH Holm AH Pedersen SU Daasbjerg K 《Langmuir : the ACS journal of surfaces and colloids》2005,21(18):8085-8089
A new versatile method has been developed for the electrochemically assisted grafting of carbon materials. The approach is based on the reduction of iodonium salts and allows the immobilization not only of aryl groups, such as phenyl or nitrophenyl, but also of alkynyl groups under mild conditions. In particular, the immobilization of alkynyl groups is important because such grafting cannot be accomplished using any other known reductive procedure. The electrochemical properties of the grafted surfaces with estimated coverages of (4-6) x 10(-)(10) mol cm(-)(2) are investigated against the ferrocene and Fe(CN)(6)(3)(-) solution probes. The analysis of the surfaces is carried out by means of cyclic voltammetry and X-ray photoelectron spectroscopy. 相似文献
109.
Herman Zagppey Roel H. Fokkens Steen Ingemann Nico M. M. Nibbering Helena Florencio 《Journal of mass spectrometry : JMS》1991,26(6):587-594
The regioselectivity of methyl cation transfer from (CH3)2F+, (CH3)2Cl+ and (CH3)3O+ to 1-phenyl-2-aminopropane was studied by Fourier transform ion cyclotron resonance in combination with collision-induced dissociation and neutralization-reionization mass spectrometry of the stable [M + CH3]+ ions formed in a chemical ionization source. The (CH3)2F+ ion transfers a methyl cation to the NH2 group and the phenyl ring with almost equal probability. Predominant CH3+ transfer to the NH2 group is observed for the (CH3)2Cl+ ion whereas the (CH3)3O+ ion reacts almost exclusively at the amino group. The preference for methylation at NH2 is discussed in terms of a lower methyl cation affinity of the phenyl ring than of the amino group and the existence of an energy barrier for methylation of the phenyl moiety. 相似文献
110.
van Beelen ES Molenaar-Langeveld TA Ingemann S 《Journal of the American Society for Mass Spectrometry》2003,14(10):1166-1176
The mechanism of propene loss from the metastable [M + D](+) ions of isomeric 2-, 3-, and 4-n-propoxypyridines and the related isopropoxypyridines has been examined by chemical ionization (CI) and tandem mass spectrometry in combination with deuterium labeling. The [M + D](+) ions were generated with CD(3)OD, CD(3)CN, (CD(3))(2)CO, or pyrrole-D(5) (listed in order of increasing proton affinity) as the CI reagent. The results reveal that the deuteron added in the CI process is not interchanged with the hydrogen atoms of the propyl group prior to propene loss from the metastable [M + D](+) ions of the propoxypyridines. The site selective labeling of the alpha-, beta-, or gamma-position of the propyl group indicates that the [M + D](+) ions of 2-n-propoxypyridine expel propene with formation of an ion-neutral complex composed of a propyl carbenium ion and 2-pyridone. By contrast, the [M + D](+) ions of 3-n-propoxypyridine expel propene by: (1) Formation of ion-neutral complexes, and (2) a conventional 1,5-hydride shift from the beta-position of the n-propyl group to the ring and/or a 1,2-elimination type process. For the 4-isomer, the results suggest the occurrence of propene loss by a 1,2-elimination in addition to the intermediate formation of ion-neutral complexes. Loss of propene with one deuterium atom is the only reaction of the [M + D](+) ions of the isopropoxypyridines labeled at the alpha-position of the isopropyl group. The results for the isopropoxypyridines labeled with three deuterium atoms at the beta-position are consistent with: (1) The loss of propene by ion-neutral complex formation and the occurrence of a substantial isotope effect in the subsequent proton/deuteron transfer within the complex, and/or (2) the loss of propene by a 1,2-elimination type reaction. 相似文献