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121.
K.J. Rawlings B.J. Hopkins S.D. Foulias 《Journal of Electron Spectroscopy and Related Phenomena》1980,18(2):213-225
The low-energy Auger spectrum of tungsten, induced by electron bombardment, has been studied. The second-derivative detection mode was employed to improve the resolution of fine structure. A comparison of N(E) spectra and yield curves with theoretical Auger rates and line energies showed that N4,5N6,7X processes dominate the spectrum, where X denotes N6,7 or O2,3. The core—core—valence (X = O4,5) processes occur with low probability. The N4N5V transition appears to be energetically allowed in tungsten, and to occur at a sufficiently high rate to alter the initial N5 : N4 hole-states ratio for the above Coster—Kronig and super-Coster—Kronig processes. For primary excitation energies above 425 eV, there is also a small contribution (about 12% at maximum) from N3N5V processes, which occurs around 166 eV. 相似文献
122.
123.
In a conducting system consisting of a short fine wire carrying a current between two larges masses of the same metal, the maximum temperature attained depends only upon the properties of the material and the applied potential difference, provided the heat lost from the surface of the wire is negligible compared with that conducted. Measurement of the maximum temperature as a function of the potential difference allows the ratio of the thermal conductivityλ to the electrical conductivityχ, and hence the Lorenz numberλ/χ T whereT is the absolute temperature, to be determined over a wide range of temperature. Experiments with platinum in various gases at atmospheric pressure and also at low gas pressures to test the effect of heat losses due to the surrounding gas are described. Under the conditions of the experiments, these losses are very small except in the case of hydrogen, the results agreeing among themselves and with those previously published. Values of the Lorenz number for palladium from 1000 to 1550? C are given. 相似文献
124.
125.
B. Hopkins 《Optics & Laser Technology》1977,9(2):93-94
126.
Both “as-grown” and “real” etched prism and (000) oxygen surfaces have been studied by LEED and Auger electron spectroscopy. Heat treatment up to 800 K was sufficient to remove impurities other than calcium on all surfaces and potassium on the polar “real” surface. These could only be removed by ion bombardment. The Ca was associated with a (3 × 1) superstructure on the prism surface and a on the polar surface. On the “as-grown” polar surface it was also possible to see (3 × 3) structure associated with reduced amounts of Ca. The especially strong binding of the electropositive elements on the negative oxygen polar surface is due to charge transfer, i.e. impurity stabilisation, this in turn can lead to chemical shifts in some of the Zn Auger transitions and to changes in the oxygen peak shape. 相似文献
127.
The characterisation of the Cs/ZnO system using LEED and AES, results in the observation of new superstructures on the (000)—O polar surface, a (2 × 2) structure and a combined (2 × 2) and (√3 × √3) configuration. A possible explanation is proposed for the existence of these superstructures in terms of electrostatic energy calculations. 相似文献
128.
The peptide sequence YIGSR, a segment of the basement membrane matrix glycoprotein laminin, has been identified as a key component in tumor cell invasion. Guided by extensive NMR work and de novo design algorithms, a nonpeptide mimetic of this pentapeptide was identified as a lead candidate for synthesis. The target displays the key amino acid side chains from a novel tricyclic scaffold. The first synthesis of this unique scaffold is completed in 11 steps and 7% overall yield. 相似文献
129.
An improved, more general method for performing multicentred integrated QM/QM calculations is presented. The new approach allows the multicentred approximation to be extended to overlapping model systems, removing a significant limitation of the original approach. The usefulness and numerical accuracy of the equations presented are confirmed via some applications to dipole–dipole, charge–dipole and charge–charge complexes. The method performs well for all of these complexes, which range from very weakly to very strongly bound and in which non-additivity effects on interaction energies range from 0.2 to 17kcalmol?1. 相似文献
130.
Hopkins WS Woodham AP Plowright RJ Wright TG MacKenzie SR 《The Journal of chemical physics》2011,134(9):094311
The photodissociation dynamics of Au-Xe leading to Xe(+) formation via the Ξ(1∕2)-X(2)Σ(+) (v('), 0) band system (41?500-41?800 cm(-1)) have been investigated by velocity map imaging. Five product channels have been indentified, which can be assigned to photoinduced charge transfer followed by photodissociation in either the neutral or the [Au-Xe](+) species. For the neutral species, charge transfer occurs via a superexcited Rydberg state prior to dissociative ionization, while single-photon excitation of the gold atom in Au(+)-Xe accesses an (Au(+))?-Xe excited state that couples to a dissociative continuum in Au-Xe(+). Mechanisms by which charge transfer occurs are proposed, and branching ratios for Xe(+) formation via the superexcited Rydberg state are reported. The bond dissociation energy for the first excited state of Au(+)-Xe is determined to be ~9720 ± 110 cm(-1). 相似文献