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901.
DONG Rui-Xin YAN Xun-Ling YANG Bing 《理论物理通讯》2008,50(8):532-536
A double helix model of charge transport in DNA molecule is given and the transmission spectra off our DNA sequences are obtained. The calculated results show that the transmission characteristics of DNA are not only related to the longitudinal transport but also to the transverse transport of molecule. The periodic sequence with the same composition has stronger conduction ability. With the increasing of bases composition, the conductive ability reduces, but the weight of θ direction rises in charge transfer. 相似文献
902.
903.
The frequency‐dependent hyperpolarizabilities of chelidamic acid complexes Mm(C7H3O5N)n (M?Cu, Ag) were investigated under the time dependent density functional theory (TDDFT) combined with the sum‐over‐states method (SOS). The relationship between molecular orbitals and nonlinear optical (NLO) properties has been explored. The results show that the charge transitions of π‐π* and 3dM‐π* are very important to the second‐order polarizabilities, and the largest component of dynamic β is 3.84×10?25 cm5·esu?1 at 0.74 eV for Ag2Cu2(C7H3O5N)4. The charge transition between π‐π* is also highly crucial to the third‐order polarizabilities, and the largest component of dynamic γ is ?4.46×10?29 esu at 0.50 eV for Ag2Cu2(C7H3O5N)4. The central Cu ion, as electron bridge, extends the range of delocalization and leads to an interesting phenomenon of spiroconjugation. 相似文献
904.
Giuseppe Melacini Robert Kaptein Rolf Boelens 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,136(2):214
An experimental approach for the editing of exchange-relayed NOEs in water-selective NOE experiments is presented. The proposed pulse sequence is based on the application during the NOE mixing time of continuous wave irradiation, which saturates resonances of relaying labile protons in slow chemical exchange with water. The technique can efficiently reduce the contributions of exchange-relayed NOE peaks that often crowd the water-selective NOE spectra and hide direct intermolecular NOEs between water and protein protons. The present approach opens new opportunities for the characterization of hydration by NMR, even in the proximity of polar labile groups. 相似文献
905.
A kinetic investigation of removal of chromium from aqueous solutions with a strong cation exchange resin 总被引:1,自引:0,他引:1
A kinetic investigation was performed with an ion exchange resin for chromium. A strong cation exchange resin (Amberlite IR
120) was used for removal of chromium. The effects of concentration, resin amount, and stirring speed on kinetics were investigated.
The metal concentration range studied was between 5 to 160 mg/dm3 (the amount of solution was 4 dm3), the resin amount range was between 5 to 20 mg, and the stirring speed range was between 1000 to 3500 rpm. Equilibrium experiments
were performed for calculation of separation factor. Kinetic studies were done using a Kressman-Kitchener stirrer reactor system and the results were compared with existing kinetic models. Two models, Nernst-Plank film diffusion control model (fdc) and solid phase diffusion control model (pdc), respectively were identified, and the dependence
of the rate on parameters such as solution concentration, resin amount, stirring speed, etc. was examined for each of them. The interpretation of these data shows that the system is probably controlled by both film
and particle diffusion.
Correspondence: Sevgi Kocaoba, Department of Chemistry, Faculty of Art and Science, Yildiz Technical University, Davutpasa
Cad. No: 127, 34210 Davutpasa-Istanbul, Turkey. 相似文献
906.
907.
M. S. Batista M. A. Morales E. Baggio-Saitovich E. A. Urquieta-González 《Hyperfine Interactions》2001,134(1):161-166
The Fe species present in Fe/ZSM-5 catalysts prepared by ionic exchange in aqueous solution or in the solid state are investigated. The samples were characterized by XRD, EPR, Mössbauer Spectroscopy (MOS-S) and chemical analysis. XRD showed that the peak intensity decreased with the increase in Fe content in the samples. EPR and MOS-S showed that the Fe atoms in all the activated samples appear as Fe+3, independently of the method used in the catalyst preparation. The MOS-S data also showed that Fe/ZSM-5, prepared by ion exchange in the solid state presented lower hematite content and more Fe species in charge-compensation sites, the responsible for the catalytic activity, as confirmed by the behavior in the propane oxidation. 相似文献
908.
A novel organic electron acceptor, N,N′-dipyrimidinyl-3,4,9,10-perylene-tetracarboxylic diimide (DMP), was designed and synthesized. The molecular structure was
characterized by FTIR spectrum and elemental analysis. By cyclic voltammetry measurements, DMP was found to possess a lower
LUMO energy level than N,N′-diphenyl-3,4,9,10-perylene-tetracarboxylic diimide due to the stronger electron-withdrawing pyrimidinyl group than the phenyl
group. Fluorescence quenching is observed in a dual-layer film consisting of a DMP layer and a C60 layer and was attributed to the charge transfer at the interface due to the energy level offset between DMP and C60.
Supported by the National Natural Science Foundation of China (Grant Nos. 50433020, 50520150165 & 50403022) 相似文献
909.
In this paper, using the exit-time statistic, we study the structure of the price variations for the high-frequency data set of the bid–ask Deutschemark/US dollar exchange rate quotes registered by the inter-bank Reuters network over the period October 1, 1992 to September 30, 1993. Having rejected random-walk models for the returns, we propose a Markovian model which reproduce the available information of the financial series. Besides the usual correlation analysis we have verified the validity of this model by means of other tools all inspired by information theory. These techniques are not only severe tests of the approximation but also evidence of some aspects of the data series which have a clear financial relevance. 相似文献
910.
S. P. Gromov E. N. Ushakov A. I. Vedernikov L. G. Kuz’mina M. V. Alfimov 《Theoretical and Experimental Chemistry》2009,45(1):3-11
A universal approach to the molecular design of light-sensitive nanodimensional systems with specific characteristics was
developed on the basis of unsaturated and macrocyclic compounds. It was possible to construct various nanodimensional systems
within the scope of a single class of compound using a limited number of components. The use of photostructural transformations
to control complex formation and mechanical movements in molecular devices and machines is discussed.
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 1, pp. 1–7, January-February, 2009. 相似文献