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111.
112.
113.
Eliette Pinel Marie‐France Barthe Jrmie De Baerdemaeker Rgis Mercier Sylvie Neyertz N. Dominique Albrola Corine Bas 《Journal of Polymer Science.Polymer Physics》2003,41(23):2998-3010
The microstructures of a series of copolyimide films were characterized with different experimental methods such as density measurements, X‐ray diffraction, ultraviolet‐visible spectrophotometry, positron annihilation spectroscopy, and dynamic mechanical analysis. The experimental data were linked to the chemical structures of the polymers and especially the alicyclic and fluorinated monomers. Some analysis responses were directly dependent on the fluorine atoms and, therefore, did not provide clear information about the microstructures. The chain organization in the amorphous films appeared to be significantly dependent on the effect of the casting solvent. The influence of the alicyclic group content was quite significant for a nonsubstituted diamine but was strongly attenuated with a fluorinated diamine. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2998–3010, 2003 相似文献
114.
Z. Yu U. Yahsi J. D. McGervey A. M. Jamieson R. Simha 《Journal of Polymer Science.Polymer Physics》1994,32(16):2637-2644
Positron annihilation lifetime measurements are reported for four monodisperse polystyrenes with molar mass M = 4,000, 9,200, 25,000, and 400,000. The temperature dependences of orthopositronium (o-Ps) lifetime (τ3) and intensity (I3) were measured from 5°C to Tg + 30°C for each sample. From these data, the free volume hole size, 〈vf(τ3)〉, and fractional free volume hps=CI3〈vf(τ3)〉 were calculated. The temperature dependences of τ3, 〈vf(τ3)〉 and hps show a discrete change in slope at an effective glass transition temperature, Tg,ps, which is measurably below the conventional bulk Tg. This suggests that τ3 is sensitive to large holes which retain their liquid-like mobility in the glassy state. Good agreement was found for T > hg,ps between hps and the theoretical free volume fraction hth deduced from experimental P-V-T data for polystyrene using the statistical mechanical theory of Simha and Somcynsky. Below Tg,ps, deviations between hps and hth are observed, hps falling increasingly below hth as temperature decreases. Whereas hps and hth depend strongly on M in the melt, each essentially independent of M in the glass. A free volume quantity, computed from the bulk volume, which is in good numerical agreement with the Simha-Somcynsky h-function in the melt, gives improved agreement with hps in the glassy state. © 1994 John Wiley & Sons, Inc. 相似文献
115.
We have tested the trapping model by comparing the temperature dependence of the peak and the tail of the angular correlation
curve from single crystal aluminum. The integral over the tail decreased as the integral over the peak increased with temperature,
in such a way that the same vacancy formation energy could be deduced from both integrals.
Paper B6 presented at 3rd Internat'l Conf. Positron Annihilation, Otaniemi, Finland (August 1973).
Case Western Reserve University, Cleveland, Ohio, USA 相似文献
116.
Alberto Chamorro 《Pramana》1978,10(1):83-88
It is shown, by providing a general method for the construction that any Fock space linear operator defined on the dense linear
manifold spanned by the particle number representation basis can be represented in terms of the annihilation and creation
operators. The normal form of the representation is unique. 相似文献
117.
D. H. D. West V. J. McBrierty C. F. G. Delaney 《Applied Physics A: Materials Science & Processing》1975,7(3):171-174
The decay time τl ofo-Ps by the electron pickoff process has been measured in polystyrene as a function of molecular weight. For samples below
their glass transition temperature τl is essentially independent of
. In the low molecular weight region,
, τl increased with decreasing
in line with earlier theoretical predictions. The overall behaviour reflects closely the dependence of free volume on
. The effects of molecular motion on τl are examined and it is concluded that the decay time is insensitive to such motions in polystyrene below the melting point,
in contrast to what is observed in polytetrafluoroethylene. 相似文献
118.
Annihilation of the contribution of one chemical component from the original data matrix is a general method in rank annihilation factor analysis (RAFA). However, RAFA is not applicable for studying the protonation equilibria of multiprotic acids. In this work, a two-rank annihilation factor analysis (TRAFA) method was proposed for determination of the acidity constants of diprotic acids. After recording the electronic absorbance spectra of the acids at different pH, the contributions of both H2A and A2− were annihilated from the absorbance data, which made feasible the determination of two successive acidity constants. The method was validated by analysis of simulated data and its application to the determination of the acidity constants of calmagite, as a reference compound. A close agreement was obtained between the resulted values by TRAFA and the declared values. Indeed, the method was used for determination of the acidity constants of two new chromenone derivatives in binary solvents mixtures of methanol and water. The effects of changing solvent composition on acidity constant data were explained by linear solvation free energy relationships (LSFER) utilizing solvatochromic parameters. 相似文献
119.
A. Uedono R. Suzuki T. Ohdaira T. Mikado S. Tanigawa M. Ban M. Kyoto T. Uozumi 《Journal of Polymer Science.Polymer Physics》2000,38(1):101-107
Open spaces and relaxation processes in the subsurface region of isotactic polypropylene were investigated by monoenergetic positron beams. From measurements of the lifetime spectra of positrons, the size of the open spaces in the subsurface region (≤ 0.2 μm) was found to be larger than that in the bulk; their differences were estimated as 20% at 295 K and 10% at 395 K. From conventional positron annihilation experiments, the glass‐transition temperatures, Tg (upper)and Tg(lower) were determined as 306 K and 278 K, respectively. These transition temperatures were associated with the onset temperatures of the molecular motions under the constraint imposed by crystalline regions and those free from the constraint, respectively. In the subsurface region, although the onset temperatures of the molecular motions were close to those in the bulk, the molecular motions above Tg (lower) were found to be suppressed. The annihilation characteristics of positrons with different implantation energies were also discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 101–107, 2000 相似文献
120.
Hidetsugu Ikegami 《International journal of quantum chemistry》1999,71(1):83-99
The remarkable coherent features are indicated for the positronium molecules Psn, which are the lightest molecular system in the universe. The majority of Psn molecules undergo the coherent annihilation of all constituent Ps atoms yielding the coherent n‐pair photons which provide a unique method for observing Psn with identifying the order of clustering n. This leads to a new microscopy [scanning clustering microscopy (SCM)] in which Psn molecules are formed from surface positrons and Ps swarmed around a fine tip of a probe electrically biased with respect to a contacting matter surface to be investigated. It would open up new broad fields to study dynamical aspects of surface layer such as the catalytic activity on a subatomic scale. A method based on the Hunbury Brown–Twiss effect is also presented to determine the dimensions of Psn. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 71: 83–99, 1999 相似文献