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11.
Mínguez-Vega G Lancis J Caraquitena J Torres-Company V Andrés P 《Optics letters》2006,31(17):2631-2633
We report spatial and temporal dispersion compensation for fan-out of femtosecond pulses with a low-frequency diffraction grating by means of a hybrid diffractive-refractive lens triplet. In this way, we achieve a multifocal light structure with nearly diffraction-limited light spots even for 20 fs pulse duration. The spatial chromatic compensation, which drastically reduces the lateral walk-off of the various spectral components, also allows us to improve the available bandwidth at the dispersion-compensated diffraction orders. In fact, the temporal width of the output pulse is essentially limited by the group-delay dispersion term, which is shown to be small. The high spatiotemporal resolution provided by our proposal permits parallel multifocal processing of materials with femtosecond pulses. 相似文献
12.
R. Ian Fryer Rudolph F. Lauer Eugene J. Trybulski Stephen Vitone Armin Walser Gladys Zenchoff 《Journal of heterocyclic chemistry》1983,20(6):1605-1608
A facile synthesis of the 4H-imidazo[5,1-c][1,4]benzothiazine ring system is described. The synthesis utilized the annulation of an imidazole ring onto a 2H-1,4-benzothiazin-3(4H)-one via the addition of the anion of ethyl isocyanoacetate. Methods for the functionalization of the 1-, 3-, 4-, and 5-positions of the ring system are presented. 相似文献
13.
The lipopolysaccharide (LPS)-rich outer membrane of gram-negative bacteria provides a protective barrier that insulates these organisms from the action of numerous antibiotics. Breach of the LPS layer can therefore provide access to the cell interior to otherwise impermeant toxic molecules and can expose vulnerable binding sites for immune system components such as complement. Inhibition of LPS biosynthesis, leading to a truncated LPS molecule, is an alternative strategy for antibacterial drug development in which this vital cellular structure is weakened. A significant challenge for in vitro screens of small molecules for inhibition of LPS biosynthesis is the difficulty in accessing the complex carbohydrate substrates. We have optimized an assay of the enzymes required for LPS heptose biosynthesis that simultaneously surveys five enzyme activities by using commercially available substrates and report its use in a small-molecule screen that identifies an inhibitor of heptose synthesis. 相似文献
14.
McDonough MJ Reynolds AJ Lee WY Jolliffe KA 《Chemical communications (Cambridge, England)》2006,(28):2971-2973
A cyclic peptide based receptor, bearing two dipicolylamino arms complexed to zinc(II) ions, binds pyrophosphate ions with high affinity and selectivity in aqueous solution as determined using an indicator displacement assay. 相似文献
15.
Joe M Sun D Taha H Completo GC Croudace JE Lammas DA Besra GS Lowary TL 《Journal of the American Chemical Society》2006,128(15):5059-5072
Mycobacteria produce a cell-surface glycoconjugate, lipoarabinomannan (LAM), which has been shown to be a potent modulator of the immune response that arises from infection by these organisms. Recently, LAM from the human pathogens Mycobacterium tuberculosis and M. kansasii has been shown to contain an unusual 5-deoxy-5-methylthio-xylofuranose (MTX) residue as well as its corresponding oxidized counterpart, 5-deoxy-5-methylsulfoxy-xylofuranose (MSX). To date, the absolute configuration of these residues and their linkage position to the polysaccharide are unknown, as is their biological role. Through the combined use of chemical synthesis and NMR spectroscopy, we have established that the MTX/MSX residues in these glycoconjugates are of the d-configuration and that they are linked alpha-(1-->4) to a mannopyranose residue in the mannan portion of the glycan. Conformational analysis of the MTX/MSX residue using NMR spectroscopy showed differences in ring conformation and as well as in the rotamer populations about the C-4-C-5 bond, as compared to the parent compound, methyl alpha-d-xylofuranoside. Two of the synthesized disaccharides, 3 and 34, were tested in cytokine induction assays, and neither led to the production of TNF-alpha or IL-12p70. In contrast, both demonstrated modest inhibitory properties when these same cytokines were induced using a preparation of Interferon-gamma and Staphylococcus aureus Cowan strain (SAC/IFN-gamma). These latter observations suggest that this motif may play a role in the immune response arising from mycobacterial infection. 相似文献
16.
Gladys Chalom 《代数通讯》2013,41(9):4321-4354
It is known that, given a tame algebra Λ, the Tits form qΛ is weakly non negative Moreover, the converse has been shown for some families of algebras, but it is not true in general. The purpose of this work is to show that for certain wild vectorspace categories K = Hom(M,B - mod) where B is tame and M is an indecomposable B-module, we have qB[M] strongly indefinite. This gives partial converses of the above theorem. 相似文献
17.
Luis E. Elizalde Gladys de los Santos Aída E. García Diana I. Medellín Ricardo Acosta 《合成通讯》2013,43(24):3087-3097
The synthesis of four novel derivatives of 1′,3′,3′‐trimethylspiro‐[2H‐1]‐benzopyran‐6‐benzyloxo‐2,2′‐indoline is reported. The synthetic approach to these compounds involves the preparation of the key compound, 3‐formyl‐4‐hydroxybenzophenone, by means of the Reimer–Tiemann reaction. The photochromic compounds were isolated and characterized by 1H and 13C NMR as well as FT‐IR and UV‐VIS spectrometry. Comparative studies performed in these compounds showed a higher molar extinction coefficient and red shift of maximum absorption wavelength when the benzyloxo group is introduced in the spirobenzopyran molecule. 相似文献
18.
Ysa��as J. Alvarado Joanna Baricelli Jos�� Caldera-Luzardo N��stor Cubill��n Gladys Ferrer-Amado Yovani Marrero-Ponce Victoria Mancilla Miguel A. Rocafull Jos�� Ojeda-Andara Luz E. Thomas Joan Vera-Villalobos Miguel Morales-Toyo 《Journal of solution chemistry》2011,40(1):26-39
The solubilities in water (W) and in 3 mol?L?1 aqueous acetonitrile at 298.15 K of thiophene-2-, furan-2- and pyrrole-2-carboxaldehyde phenylhydrazone along with their nitro and 2,4-dinitro derivatives, referred to as PCT, PCF, PCP, NPCT, NPCF, NPCP, DPCT, DPCF and DPCP, respectively, are reported. The standard Gibbs energy of transfer from W to solvent mixtures ( $\Delta G^{\mathrm{transf}}_{\mathrm{W-mix}}$ ) was estimated for each solute. The results indicate that the transfer process for all systems is a spontaneous process. Calculations under the scaled-particle theory suggest that the work of cavity creation (????G c), which is associated with the transfer of the phenylhydrazone from W to mix, dominates the magnitude of $\mathrm {\Delta} G^{\mathrm{transf}}_{\mathrm{W-mix}}$ . UV spectroscopic measurements suggest that these compounds bind calf thymus(CT)-DNA via intercalation mode in a buffer?C3 mol?L?1 acetonitrile solution. The binding constant (K b) depends on the nitro-substitution on the phenyl moiety and the electronegativity of the heteroatom in the heterocyclic ring. The corresponding Gibbs energy of binding ( $\Delta G_{\mathrm{DNA-B}}^{0}$ ) of phenylhydrazone derivatives to CT-DNA shows a marked dependence with ????G c. The anticancer activity on human breast cancer cell lines MDA-231, MDA-435 and HT-29 human colon adenocarcinoma cell line was evaluated for the compounds NPCT, NPCF, DPCT and PCT. 相似文献
19.
The dissociation behaviour and valence-electronic structure of water adsorbed on clean and oxygen-covered Ru{0001}, Rh{111}, Pd{111}, Ir{111} and Pt{111} surfaces has been studied by high-resolution X-ray photoelectron spectroscopy with the aim of identifying similarities and trends within the Pt-group metals. On average, we find higher reactivity for the 4d metals (Ru, Rh, Pd) as compared to 5d (Ir, Pt), which is correlated with characteristic shifts in the 1b(1) and 3a(1) molecular orbitals of water. Small amounts of oxygen (< 0.2 ML) induce dissociation of water on all five surfaces, for higher coverages (> 0.25 ML) only intact water is observed. Under UHV conditions these higher coverages can only be reached on the 4d metals, the 5d metals are, therefore, not passivated. 相似文献
20.