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171.
Paola Manca Maria I. Pilo Giovanni Casu Serafino Gladiali Gavino Sanna Roberta Scanu Nadia Spano Antonio Zucca Chiara Zanardi Diego Bagnis Luca Valentini 《Journal of polymer science. Part A, Polymer chemistry》2011,49(16):3513-3523
A novel polythiophene bearing a pendant terpyridine moiety has been synthesized by electrochemical polymerization of a new thiophene monomer, namely 4′‐(2,2′:5′,2″‐terthien‐3′‐ethynyl)‐2,2′:6′,2″‐terpyridine (TAT). The insertion of a conjugated ethynyl spacer between the terthiophene and the terpyridine fragments provides for an effective extension of the delocalization of electrons within the structural unit and the polymer as a whole. The synthesis and characterization of the relevant monomer, the electrosynthesis of the corresponding polymer and its electrochemical, UV–visible spectroelectrochemical and IR characterization are described. Finally, a comparison between the electrochemical, spectroscopic, and spectroelectrochemical properties of PTAT and the analogue, saturated‐spacer PTTT (TTT = 4′‐[(2,2′:5′,2″‐terthien‐3′‐yl)methoxy]‐2,2′:6′,2″‐terpyridine) polymer is discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
172.
173.
New models for the steric environment of Ti isospecific polymerization sites for poly(propylene) on MgCl2 microcrystals are proposed. They directly involve a donor molecule in order to obtain isospecific activable Ti atoms otherwise belonging to isolated adsorbed TiCl4 molecules or Ti2Cl8 dimers which are lacking of the required chirality for stereocontrol. The donor molecules able to attain at best this effect keep to some peculiar conformational rules settled by the authors in a previous theoretical-correlative study on highly active Lewis bases. The new 1,3-dimethoxypropane series suggested by the authors and recently patented by Montell has been examined in detail. Essentially three different types of closeness between Ti atoms and donor molecules can take place, in which different moieties of the diether compound help to build the ‘right’ steric environment in the site's neighbouring. In the three proposed models S1, S2, S3 the stereocontrol is attained through, respectively, one of the methoxy moieties, one of the methyls, and one of the central carbon atom substituents. New hypotheses on the role of Lewis bases in the preparation of isospecific heterogeneous Ziegler-Natta catalysts are discussed. 相似文献
174.
New models for steric environment of Ti isospecific polymerization sites on MgCl2 microcrystals are presented. They directly involve the presence of a donor molecule in order to obtain chiral activable Ti atoms otherwise belonging to isolated adsorbed TiCl4 molecules or Ti2Cl8 dimers which are lacking the required symmetry. The most important steric features of donor molecules have been obtained through structure-activity relationships and molecular comparisons, while their adsorption on MgCl2 faces lateral to (001) has been studied through a conformational analysis approach. 相似文献
175.
As part of a study of the RR spectra of different manganates, the spectra of RbMnO4, CsMnO4, AgMnO4, Sr(MnO4)2.3H2O and La(MnO4)3.nH2O were obtained and interpreted in comparison with those of other permanganates previously reported. The analysis of the corresponding X11 anharmonicity constants and full-widths at half maxima of the members of the vν1 progressions allowed a wider insight into the effects of the countercations on the vibrational properties of the MnO?4 ion. 相似文献
176.
De Angelis F Ceci R Quaresima R Reale S Di Tullio A 《Rapid communications in mass spectrometry : RCM》2003,17(6):526-531
Lichens are ubiquitous organisms formed by symbiotic associations of fungal hyphas and algae that also grow under often extreme environmental conditions. They produce secondary metabolites, the so-called lichen substances, whose structural characterization can give an important contribution to lichen taxonomy. Lichens are also widely employed as biomonitors of atmospheric pollution; being epiphyte organisms they tend, in fact, to accumulate exogenous compounds. Moreover, it could be questioned if the environmental stress alters their secondary metabolites production. Therefore, a new strategy for the analysis of the organic substances absorbed or metabolized by lichens has been developed. This method exploits the dry solid-phase microextraction (SPME) headspace technique coupled with gas chromatography/mass spectrometry (GC/MS). Lichens coating the stone surfaces of monuments, located in small towns between high mountains and far away from urban environments, have been investigated. In the field of cultural heritage, this study can contribute to the knowledge of the state of conservation of outdoor exposed historical monuments. 相似文献
177.
Brinchi L Germani R Savelli G Spreti N 《Journal of colloid and interface science》2004,274(2):701-705
A new class of cationic surfactants containing the heterocyclic piperazinium ring in their covalent structure was prepared; cetyldialkylpiperazinium halides, CRPX, with alkyl=Me (CMPX), Et (CEPX), n-Pr (CPPX), and with halide=Br and Cl. They were characterized by measures of critical micellar concentration, cmc, and ionization degree, alpha, and also by use of the decarboxylation of 6-nitrobenzisoxazole-3-carboxylate as a kinetic probe to investigate the properties of the microinterface they provide in aqueous solutions. The pseudophase kinetic treatment fails to fit the data at high [surfactant], which show anomalies with abrupt increase in k(obs), especially for CEPX and CPPX. Data can be fitted up to [surfactant] ca. 0.1 M, and 0.2 M in some cases. Compared with cetyltrialkylammonium halides, values of k'(M) indicate a water-richer microenvironment and less important interface property changes with increasing head group bulk. The reaction could be studied both in the presence and in the absence of NaOH; comparison shows that NaOH affects only the shape of the kinetic profile at low [surfactant], without affecting the microenvironment provided by mature micelles. 相似文献
178.
Summary Interactions of tetrakis--acetato-dirhodium(II) with purine-derived ligands of biological interest such as the cytokinins 6-furfurilaminopurine (K), 6-benzylaminopurine (BAP), 6-furfurilaminopurine riboside (KR) and 6-benzylaminopurine riboside (BAPR) have been studied by means of magnetic susceptibility measurements at room temperature, i.r. and electronic spectroscopy and thermogravimetric analysis 11 metal:ligand adducts were obtained with all ligands; in addition 12 adducts were obtained with KR and BAPR. The most plausible structure for the 11 adducts is a polymeric bridging one, involving both axial positions of the RhII dimer and two N-sites of the purine moiety; for the 12 adducts only one N-site is involved. 相似文献
179.
In this paper, we assume that the log return of the underlying asset follows a semi-Markov process, then from the knowledge of the kernel we derive an explicit expression for the value of the option and for the bare risk in the case of the European call (put) option and, by means of a recursive system, we derive the value and the bare risk in the case of the American option. The prices and risks we obtained depend explicitly on the waiting-time distributions of the asset and they are duration dependent. The link with models based on Markov Chains and Continuous Time Random Walks is debated. 相似文献
180.
The original article to which this Erratum refers was published in Applied Stochastic Models in Business and Industry 2005; 21 (3):241–249 相似文献