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61.
Constanze Müller Inga Dietz Dimitrios Tziotis Franco Moritz Jan Rupp Philippe Schmitt-Kopplin 《Analytical and bioanalytical chemistry》2013,405(15):5119-5131
Infections with Chlamydia pneumoniae cause several respiratory diseases, such as community-acquired pneumonia, bronchitis or sinusitis. Here, we present an integrated non-targeted metabolomics analysis applying ultra-high-resolution mass spectrometry and ultra-performance liquid chromatography mass spectrometry to determine metabolite alterations in C. pneumoniae-infected HEp-2 cells. Most important permutations are elaborated using uni- and multivariate statistical analysis, logD retention time regression and mass defect-based network analysis. Classes of metabolites showing high variations upon infection are lipids, carbohydrates and amino acids. Moreover, we observed several non-annotated compounds as predominantly abundant after infection, which are promising biomarker candidates for drug-target and diagnostic research. 相似文献
62.
Wiederhold 《Fresenius' Journal of Analytical Chemistry》1864,3(1):232-233
Ohne Zusammenfassung 相似文献
63.
Dr. Ph. Wiederhold 《Mathematische Annalen》1875,8(4):444-452
Ohne Zusammenfassung 相似文献
64.
65.
M. Burstyn Gustav Merz Wiederhold H. Hager und E. Geissler 《Fresenius' Journal of Analytical Chemistry》1878,17(1):387-393
Ohne Zusammenfassung 相似文献
66.
The wet chemical etching of silicon by concentrated HF-HNO3 mixtures in solar and semiconductor wafer fabrication requires the strict control of the etching conditions. Surface morphology and etch rates are mainly affected by the amount of dissolved silicon, that is continuously enriched in the etching solution with each etching run. A fast and robust method for the titrimetric determination of the total dissolved silicon content out of the concentrated etching solution is presented. This method is based on the difference between the two equivalence points of the total amount of acid and the hydrolysis of the hexafluorosilicic anion. This approach allows a silicon determination directly from the etching process in spite of the presence of dissolved nitric oxides in the etching solution. The influences of different acid mixing ratios and of the etching solution density depending on the silicon content is considered and discussed in detail. 相似文献
67.
Klemm C Otto S Wolf C Haseloff RF Beyermann M Krause E 《Journal of mass spectrometry : JMS》2006,41(12):1623-1632
The affinity of titanium dioxide for phosphate groups has been successfully used for enrichment of phosphopeptides from complex mixtures. This paper reports the relationship between the occurrence of some amino acids and the phospho-specific and nonspecific binding of peptides that occurs during titanium dioxide enrichment. In order to perform a systematic study, two well-characterized peptide mixtures consisting of either 33 or 8 synthetic phosphopeptides and their nonphosphorylated analogs, which differed in charge and hydrophobicity, were synthesized and analyzed by ESI-MS and MALDI-MS. The titanium dioxide procedure was also evaluated for comprehensive detection of phosphopeptides in phosphoproteomics. In summary, our results clearly confirm the high selectivity of titanium dioxide for phosphorylated sequences. Drastically reduced recovery was observed for phosphopeptides with multiple basic amino acids. Nonspecific binding of nonphosphorylated peptides and sample loss of phosphopeptides must also be taken into account. 相似文献
68.
Wolfgang Holzer Constanze Kautsch Rosa M. Claramunt Ibon Alkorta José Elguero 《Tetrahedron》2004,60(32):6791-6805
The tautomerism of pyrazolones unsubstituted at position 3(5) has been investigated by 13C- and 1H NMR spectroscopic methods. Apart from chemical shift considerations and NOE effects the magnitude of the geminal 2J[pyrazole C-4,H3(5)] spin coupling constant permits the unambiguous differentiation between 1H-pyrazol-5-ol (OH) and 1,2-dihydro-3H-pyrazol-3-one (NH) forms. Whereas 1H-pyrazol-5-ols and 2,4-dihydro-3H-pyrazol-3-ones (CH-form) exhibit 2J values of approximately 9-11 Hz, in 1,2-dihydro-3H-pyrazol-3-ones this coupling constant is considerably reduced to 4-5 Hz. This can be mainly attributed to the removal of the lone-pair at pyrazole N−1 in the latter due to protonation or alkylation. According to the data obtained, 2-substituted 4-acyl-1,2-dihydro-3H-pyrazol-3-ones exist predominantly as pyrazol-5-ols in CDCl3 or benzene-d6 solution, whereas in DMSO-d6 also minor amounts of NH tautomer may contribute to the tautomeric composition. 2,4-Dihydro-2-phenyl-3H-pyrazol-3-one (1-phenyl-2-pyrazolin-5-one) exists in benzene-d6 solely in the CH-form, in CDCl3 as a mixture of CH and OH-form, whereas in DMSO-d6 a fast equilibrium between OH and NH isomer (with the former far predominating) is probable. For 11 compounds, including neutral and protonated molecules, we have calculated at the B3LYP/6-311++G** level, the 2J(1H,13C) coupling constants which are in good agreement with those measured experimentally. 相似文献
69.
Hans-Dieter Martin Constanze Heller Edwin Haselbach Zuzana Lanyjova 《Helvetica chimica acta》1974,57(2):465-472
The photoelectron spectra of quadricyclane ( 3 ) and 3-methylidene quadricyclane ( 4 ) have been measured. The results served as a basis for the elucidation of the electronic structure of these compounds, which agreed with theoretical calculations. It is found that the symmetry of the HOMO of 3 is different when compared to that of its valence isomer norbornadiene ( 1 ). The results also indicate that the structure of the highest occupied orbitals cannot be derived by only considering the Walsh-orbitals of the two three-membered rings. In addition one of the Walsh-components of the four-memebered ring has to be taken into account. 相似文献
70.