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51.
52.
Protonated threonine and its allo diastereomer exhibit different proportions of collisionally activated dissociation (CAD) product ions. N-Methylation attenuates these differences. Water loss from protonated allo-threonine gives protonated trans-3-methylaziridinecarboxylic acid via an internal S(N)2 pathway, rather than protonated vinylglycine. 相似文献
53.
The title compound was obtained through a seven steps sequence and using - dimethyl L-tartrate as the starting material (30% overall yield). The system 2,3-dideoxy-L-threo-hex-2-enono-1,5-lactone is present in several natural compounds. 相似文献
54.
MM. D. Letouz J. Duflos G. Queguiner P. Pastour 《Journal of heterocyclic chemistry》1973,10(6):1075-1076
This communication describes the synthesis of 7-one (7H) cyclohepta[b]pyridine and some derivatives (6,8-dimethyl; 8-methyl; 8-ethyl….). These compounds have been obtained by condensation of ketones with 2,3-diformylpyridine. 相似文献
55.
Serafin Fraga 《Journal of computational chemistry》1982,3(3):329-334
The coefficients of a 1/R expansion (containing long-range electrostatic interaction, medium-range electrostatic-induced dipole attraction, short-range dispersive attraction, and very short overlap interaction terms) have been determined, within a semiempirical approach, from the results of a priori calculations. The formulation has been applied to the study of the stable conformations of benzene complexes. 相似文献
56.
LetX
1 andX
2 be two mixing Markov shifts over finite alphabet. If the entropy ofX
1 is strictly larger than the entropy ofX
2, then there exists a finitary homomorphism ϕ:X
1→X
2 such that the code length is anL
p
random variable for allp<4/3. In particular, the expected length of the code ϕ is finite.
Research supported by KBN grant 2 P03A 039 15 1998–2001. 相似文献
57.
Complex Fluorides of Palladium(II) – A Short Survey Fluorine and its compounds in some respects take over a certain exceptional position which is in many cases different from heavy homologous and respectively their compounds. On the one hand this applies to the different stability of comparable oxidation states (as far as they are accessible) and on the other hand it applies to the commonly observed compositions or structures of the particular compounds, as well. This concerns the compounds of the binary as well as those of the ternary and the even more complex systems. Besides its to a large extent ionic bond character (at least at lower oxidation states), the marginal size (F? is the smallest elementary charged anion) and sometimes its minor ligand field force plays an essential role by the constitution of ligands (coordination sphere), anyway by transition metal complexes. One of the most distinctive examples for this purpose are the PdII–fluorides, the following short survey deals with. 相似文献
58.
The objective of this study was to determine if topical anesthesia to the larynx and pharynx affects vocal fold motion during dynamic voice evaluation with transnasal flexible endoscopy. Transnasal dynamic laryngeal examinations of 10 patients with no voice complaints were evaluated by five blinded fellowship-trained laryngologists. Each patient was examined before and after application of topical anesthetic. Reviewers rated briskness of right and left vocal fold movement and longitudinal tension on a visual analogue scale. Statistical comparisons were made between individual subject scores before and after anesthetic application. Inter-rater reliability was also assessed. No statistical difference was observed between subject scores before and after anesthetic application. Average intraclass correlation coefficients were 0.643 and 0.591 for pre- and postanesthesia scores, respectively. Application of topical anesthesia to the larynx and pharynx does not affect vocal fold motion. 相似文献
59.
Florian Kraus Sergei I. Ivlev Jascha Bandemehr Malte Sachs Clemens Pietzonka Matthias Conrad Michael Serafin Bernd G. Müller 《无机化学与普通化学杂志》2020,646(18):1481-1489
The crystal structure of β-MnF4 has finally been elucidated. It crystallizes in the non-centrosymmetric space group R3c, no. 161, hR360, with the lattice parameters a = 19.390(3), c = 12.940(3) Å, V = 4213.3(14) Å3, Z = 72, T = 100 K. It is a 4a × 4a superstructure of the VF3 (FeF3) structure type. The Mn atoms are coordinated octahedron-like by F atoms, of which two are bound terminal, while the other act as μ-bridging F atoms to other Mn atoms forming a three-dimensional infinite network structure which can be described by the Niggli formula 3∞[MnF4/2F2/1]. Voids on the metal sites, which are occupied in the VF3 structure, are grouped together in the shape of a “star” with approximate D3h symmetry. We prepared β-MnF4 photochemically according to the literature and obtained a phase-pure powder as evidenced by X-ray diffraction at room temperature. The lattice parameters are a = 19.566(3), c = 12.984(2) Å, V = 4304(1) Å3. IR and Raman spectra recorded on the powder show that β-MnF4 has also been obtained free of moisture, HF, and O2+ containing compounds, however MnF3 is likely present as a magnetic impurity. We observe thermal decomposition of MnF4 to MnF2 and not MnF3. 相似文献
60.
Joscha Breibeck Adam Serafin Andreas Reichert Stefan Maier Bernhard Küster Arne Skerra 《Journal of the American Society for Mass Spectrometry》2014,25(8):1489-1497
We describe the design, preparation, and mass-spectrometric characterization of a new recombinant peptide calibration standard with uniform biophysical and ionization characteristics for mass spectrometry. “PAS-cal” is an artificial polypeptide concatamer of peptide cassettes with varying lengths, each composed of the three small, chemically stable amino acids Pro, Ala, and Ser, which are interspersed by Arg residues to allow site-specific cleavage with trypsin. PAS-cal is expressed at high yields in Escherichia coli as a Small Ubiquitin-like MOdifier (SUMO) fusion protein, which is easily purified and allows isolation of the PAS-cal moiety after SUMO protease cleavage. Upon subsequent in situ treatment with trypsin, the PAS-cal polypeptide yields a set of four defined homogeneous peptides in the range from 2 to 8 kDa with equal mass spacing. ESI-MS analysis revealed a conveniently interpretable raw spectrum, which after deconvolution resulted in a very simple pattern of four peaks with similar ionization signals. MALDI-MS analysis of a PAS-cal peptide mixture comprising both the intact polypeptide and its tryptic fragments revealed not only the four standard peptides but also the singly and doubly charged states of the intact concatamer as well as di- and trimeric adduct ion species between the peptides, thus augmenting the observable m/z range. The advantageous properties of PAS-cal are most likely a result of the strongly hydrophilic and conformationally disordered PEG-like properties of the PAS sequences. Therefore, PAS-cal offers an inexpensive and versatile recombinant peptide calibration standard for mass spectrometry in protein/peptide bioanalytics and proteomics research, the composition of which may be further adapted to fit individual needs. Figure
? 相似文献