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11.
RIVLIN T. J.; RUSCHEWEYH ST.; SHAFFER D.; WIRTHS K. J. 《IMA Journal of Numerical Analysis》1983,3(3):327-332
Given (1, 0), n N, we discuss the optimal recoveryof (), for analytic and bounded in < 1, from the knowledge of the values of at n points z1,.zm[0,l),where these points are chosen to produce the least possibleintrinsic error. The optimal algorithms are explicitly determined. 相似文献
12.
A. S. Abdel-Halim E. Metwally M. M. El-Dessouky 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(1):123-124
Neutron activation analysis is one of the most extensively used methods for environmental studies due to its high sensitivity, precision, versatility and multielemental character. Cement factories at Helwan, south of Cairo, contribute substantially to environmental pollution. Determination of minor and trace-elements in dust particulates from the cement industrial areas has been performed to assess the air quality from an environmental and human health point of view. Soil-7 standard reference material from IAEA and SRM-1571 from NBS were used for quality assurance testing. The data obtained indicate there is an indication that the pollution could be hazardous to people living in and around the area surveyed. 相似文献
13.
A FORTRAN computer program for automatic neutron activation analysis is presented. The program locates and identifies peaks
in a gamma-ray spectrum, calculates peak areas and the concentrations of the elements of interest in the sample. This program
was specifically designed for the SLOWPOKE reactor, it uses a semi-absolute method and does not need standards or flux monitors.
The program was written so as to minimize the computation time, and a typical 4096-channel spectrum is processed in five seconds
by an IBM 360/75 computer. 相似文献
14.
M. Dülk ST. Fischer M. Bitter M. Caraccia W. Vogt E. Gini H. Melchior W. Hunziker A. Buxens H.N. Poulsen A.T. Clausen 《Optical and Quantum Electronics》2001,33(7-10):899-906
A monolithically integrated and fully packaged Mach–Zehnder interferometer with semiconductor optical amplifiers (MZI-SOA) is demonstrated as polarisation-independent high-speed demultiplexer for up to 160 Gbit/s optical time division multiplexed (OTDM) data streams. 相似文献
15.
Musa I. El-Barghouthi Hamzeh M. Abdel-Halim Feryal J. Haj-Ibrahim Khaleel I. Assaf 《Supramolecular chemistry》2013,25(1-2):80-89
Molecular dynamics (MD) simulations were performed for cucurbit[6]uril (CB6) methyl and cyclohexyl derivatives in aqueous solutions. Furthermore, MD simulations have been conducted to study the inclusion complexes between each CB6 derivative with α,ω-pentane diammonium ion (NH3+(CH2)5NH3+) to estimate the binding free energies, the complex geometries and the intermolecular forces responsible for complex formation. Results show a complete inclusion of the guest molecule in the cavity of the host for all complexes. Results also indicate that the guest dynamics inside the cavity of the substituted host is similar to that for the unsubstituted host. This demonstrates that the molecular recognition of the host is not affected by the alkyl substitution at the equator. Also, there is an insignificant conformational change of the macrocyclic structure upon inclusion of the guest. Molecular mechanics/Poisson Boltzmann surface area method was used to estimate the binding free energy of each complex. Results indicate that host–guest electrostatic interactions make the largest contribution to the complex binding free energy. Moreover, van der Waals interactions add significantly to the complex stability. The guest molecules show more or less similar binding free energies with the substituted CB6 that exhibits slightly more negative values than unsubstituted CB6 which is proved also by umbrella sampling. 相似文献
16.
Results of DSC under isothermal conditions on the chalcogenide glass Bi10Se70In20 are reported and discussed. The Johnson-Mehl-Avrami equation was used to evaluate the crystallization activation energy (E
a) and the crystallization mechanism was studied. The results indicate that the crystallization mechanism involves one dimensional and surface processes for Bi10Se70In20. The average calculated value ofE
a for Bi10Se70In20 is 34.38±1.46 kcal/mol.
The authors are grateful to Dr. N. Afify for many helpful discussions. This work was partly supported by a Grant-in-Aid for Scientific Research from the Deutsche Gesellschaft für Technische Zussammenarbeit (G.T.Z.) and D.A.A.D., Germany 相似文献
Zusammenfassung Die Ergebnisse von isothermen DSC-Untersuchungen an dem Chalkogenglas Bi10Se70In20 wurden beschrieben und diskutiert. Die AktivierungsenergieE a der Kristallisierung wurde mit Hilfe der Johnson-Mehl-Avrami-Gleichung ermittelt und der Kristallisierungsmechanismus untersucht. Die Ergebnisse zeigen, da\ der Kristallisierungsmechanismus von Bi10Se70In20 eindimensionale und OberflÄchenvorgÄnge beinhaltet. Der errechnete mittlere Wert vonE a betrÄgt für Bi10Se70In20 34.38±1.46 kcal/mol.
The authors are grateful to Dr. N. Afify for many helpful discussions. This work was partly supported by a Grant-in-Aid for Scientific Research from the Deutsche Gesellschaft für Technische Zussammenarbeit (G.T.Z.) and D.A.A.D., Germany 相似文献
17.
A new naturally occurring ent-kaurane diterpenoid dimer, 15β, 15′β-oxybis (ent-kaur-16-en-19-oic acid) (1) along with six known compounds, 15β-hydroxy-ent-kaur-16-en-19-oic acid (2), 15β-hydroxy-ent-kaur-16-en-19-oate-β-d-glucopyranoside (3), 6-hydroxykaempferol-3, 7-dimethyl ether (4), quercetagetin 3, 7, 3′-trimethyl ether (5), β-sitosterol (6) and β-sitosterol glucoside (daucosterol) (7) were isolated from the aerial parts of Pulicaria inuloides DC. Compounds 2–5 were isolated for the first time from genus Pulicaria. The structures of compounds 1–7 were established on the basis of extensive 1D and 2D NMR spectroscopic techniques in combination with ESI-MS. The antimicrobial activity of the isolated compounds was evaluated against Staphylococcus aureus, Escherichia coli and Candida albicans. Sulphorhodamine B cytotoxic assay against HepG2 (liver cancer) cell line and ABTS antioxidant assay were carried out. 相似文献
18.
Issa A. A. Abdel-Halim H. M. Al-Degs Y. S. Al-Masri H. A. 《Research on Chemical Intermediates》2017,43(1):523-544
Research on Chemical Intermediates - The competitive adsorption of two common colorants (brilliant blue and brilliant black) by activated kaolinite was investigated after fast quantification of... 相似文献
19.
A theoretical study of the 21Ag ← 11Ag two-photon transition and its vibronic band in trans-stilbene
JONNA STÅLRING LAURA GAGLIARDI PER-ÅKE MALMQVIST ROLAND LINDH 《Molecular physics》2013,111(11):1791-1796
The two-photon spectrum of the 21Ag ← 11Ag transition in trans-stilbene has been calculated at the complete active space self-consistent field (CASSCF) level of theory. Energies were obtained at the complete active space second-order perturbation (CASPT2) level of theory, while the geometries of both the initial and final states were optimized at the CASSCF level. The energy and the geometry optimizations were performed using an active space of 14 electrons in 14 active π orbitals. The vibrational frequencies of both states and the two-photon transition (TPT) cross-section were calculated with a smaller active space where the two lowest π orbitals were kept inactive. A newly implemented algorithm, in the quantum chemical package Molcas was used to determine the two-photon transition intensity. This method requires only the linear response of the CASSCF wavefunction. Furthermore, the vibronic structure of this TPT was studied. The Franck-Condon factors were obtained by calculating the overlap between the vibrational states involved, which were determined from the force fields of both the initial and final states, at the CASSCF level of theory. The results are in agreement with experiment. 相似文献
20.
JONNA STÅLRING MARTIN SCHÜTZ ROLAND LINDH GUNNAR KARLSTRÖM PER-OLOF WIDMARK 《Molecular physics》2013,111(21):3389-3399
The low-energy region of the intermolecular potential energy hypersurface (PES) of the ammonia dimer was studied at the level of second-order Moller-Plesset perturbation theory (MP2) using a very large basis set. Individual minima were located on the PES employing the counterpoise (CP) correction to account for the basis set superposition error (BSSE). Apart from these canonical MP2 calculations local MP2 (LMP2) calculations were performed. For the latter the BSSE at the correlated level is inherently absent by virtue of the local truncation of the virtual space. Results from canonical and local MP2 calculations are compared and the reliability of the LMP2 method for intermolecular complexes and clusters is discussed. The canonical MP2 calculations predicted five minimum structures, the four most stable ones lying energetically very close. For these four structures single point MP2 energy calculations with a further extended basis set (1024 functions for the ammonia dimer) were performed. The equilibrium dissociation energies so obtained are close to the one-particle basis set limit, as illustrated by a remaining BSSE of less than 0.2 kJ mol?1. The geometry optimizations at the LMP2 level, using the three most stable canonical MP2 structures as initial geometries, all collapsed to a single minimum corresponding to an asymmetric structural arrangement. A canonical MP2 single point calculation, at that geometry, revealed that the LMP2 minimum structure is virtually as stable as the lowest minima on the canonical MP2 PES. Based on these calculations the global minimum of the ammonia dimer was assigned to a part of the PES represented by an asymmetric structure with an equilibrium dissociation energy of 13.5±0.3 kJ mol?1 相似文献