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41.
Slavica Marinović Marko Krištović Branka Špehar Vinko Rukavina Ante Jukić 《Journal of Analytical Chemistry》2012,67(12):939-949
Partial least squares regression (PLS) calibration models based on Fourier transform infrared (FTIR-ATR) and Raman spectra (FT-Raman) were applied to the rapid and accurate simultaneous determination of the main properties of diesel fuels. Training sets were composed of over ninety commercial diesel fuel samples. The methods use baseline-uncorrected, raw FTIR-ATR and FT-Raman spectra. Two spectral regions were studied: full spectral region and “fingerprint” region. The models were validated using the cross-validation process. Based on the correlation coefficient and root mean square error of cross validation (RMSECV) values the both developed calibration models, PLS/FTIR-ATR and PLS/FT-Raman, were very accurate and comparable with standard testing methods. The following diesel fuel properties may be confidently estimated: cetane number, cetane index, density, viscosity, distillation temperatures at 10% (T10), 50% (T50) and 90% (T90) recovery, as well as the contents of total aromatics and polycyclic aromatic hydrocarbons. As compared to the “fingerprint” spectral region, the PLS/FTIR-ATR model using full spectral region displayed slightly better performances with the most of the correlation coefficient values above 0.98. 相似文献
42.
Five cellulase components were identified and purified in one step from Streptomyces strain A20 using electroendosmotic preparative electrophoresis. By this procedure up to 18 mg of protein mixture could be loaded on the column, with an estimated recovery of 60-70% of total activity; activity and protein recovery could be estimated 32% and 47% respectively, if only activity peaks were considered. In comparison to other purification methods, this technique results in high protein recovery and resolution of applied samples. 相似文献
43.
The lithium–aluminum–silver ternary system has been investigated and two new phases Li6.98Al4.15Ag0.87 and LiAlAg2 were characterized using both powder and single crystal X-ray diffraction techniques. These phases crystallize in the cubic system, space group (a=6.344(1), 6.3124(5) Å), they, respectively, display the Pearson's cF12- and cF16-type structural arrangements. Compared to Li2AlAg, the only phase in the system reported so far, the structure of Li6.98Al4.15Ag0.87 is disordered owing to atomic substitutions and contains a full site vacancy. Band structures and densities of states of Li6.98Al4.15Ag0.87, LiAlAg2 and Li2AlAg have been calculated by a first principle pseudopotential method using the plane-wave basis CASTEP package. 相似文献
44.
Li13Cu6Ga21 crystallizes in a cubic structure, space group Im3, with a = 13.568(2) Å, Z = 4. Diffraction data were collected on a NONIUS CAD 4 diffractometer in the range 4 ≤ 2θ ≤ 50° (MoKα radiation). The structure was solved by direct methods and refined by full-matrix least-squares to a final R(F) = 0.033 for 346 independent reflections with I> 3σ(I). Li13Cu6Ga21 presents an interesting structure composed of Samson's polyhedral clusters (104 atoms) linked to each other through smaller junction polyhedral clusters (truncated tetrahedra and hypho-13-vertex polyhedra) containing lithium atoms in their centers. 相似文献
45.
Branko Kozuilić Ivančica Leuštek Branka Pavlović Pavao Mildner Slobodan Barbarić 《Applied biochemistry and biotechnology》1987,15(3):265-278
Each of the three high-mannose type glycoproteins studied, acid phosphatase, invertase, and glucose oxidase, could be specifically
cross-linked through its carbohydrate chains. The procedure involves periodate oxidation of carbohydrate residues followed
by reaction of the generated aldehyde groups with adipic acid dihydrazide as a cross-linker. The amount and size as well as
solubility of the formed polymers could be efficiently controlled by varying the reaction conditions, i.e., the oxidation
degree and the concentrations of glycoproteins, cross-linker, and hydrogen ions during the cross-linking reaction. It was
found that the quantity and size of polymers increased with oxidation degree and protein concentration and by lowering the
pH. When the protein concentration was above and pH below certain values, depending on the glycoenzyme, insoluble polymers
formed. The soluble cross-linked polymers retained a high level of original activity, and the minor decrease in specific activity
noticed was shown to occur during the periodate oxidation step. The cross-linked glycoenzymes are much more resistant to denaturation
by high temperature and by changes in pH, demonstrating the usefulness of this method in preparation of the stabilized glycoprotein
derivatives. 相似文献
46.
Ribet JP Pena R Maurel JL Belin C Tillard M Vacher B Bonnaud B Colpaert F 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(1-3):353-363
{[1-(3-Chloro-4-fluorobenzoyl)-4-fluoropiperidin-4yl]methyl}[(5-methylpyridin-2-yl)methyl]amine, fumaric acid salt (C(20)H(22)ClF(2)N(3)O, C(4)H(4)O(4)) (1) was synthesized and characterized by the complete (1)H, (13)C and (19)F NMR analyses. The conformation of the piperidin ring, in the solution state, was particularly studied from the coupling constants determined by recording a double-quantum filtered COSY experiment in phase-sensitive mode. (1)H NMR line-shape analysis was used, at temperatures varying between -5 and +60 degrees C, to determine the enthalpy of activation of the rotational barrier around the CN bond. Compound 1 crystallizes in the triclinic space group P1 with a=8.517(3) Angstrom, b=12.384(2) Angstrom, c=12.472(3) Angstrom, alpha=70.88(2) degrees, beta=82.04(2) degrees, gamma=83.58(2) degrees. The results strongly indicate that the solid and solution conformations are similar. Thermal stability and phases transitions were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Furthermore polymorphism screening was studied from recrystallization of 1 performed in seven solvents and by slurry conversion in water. The X-ray powder diffraction (XRPD) and differential scanning calorimetry results suggested that 1 crystallizes into one crystalline form which melts at 157 degrees C (DeltaH=132 J g(-1)). 相似文献
47.
The molecular and electronic structure of eight substituted quinolines has been investigated by HeI/HeII photoelectron spectroscopy, Green's function calculations, and comparison with the spectra of related compounds. The correlation between nitrogen lone pair ionization energies and basicity in 18 substituted quinolines is discussed. The influence of different substituents has been quantified via the scheme that is based on experimental energy shifts. The relationships between nitrogen ionization energies, pK(a) values, and medicinal activity are also discussed. 相似文献
48.
49.
The electronic structures of yttrium(III), gadolinium(III) and ytterbium(III) tris-2,2,6,6-tetramethyl-3,5-heptanedione (tmhd) complexes have been investigated by HeI and HeII photoelectron spectroscopy (UPS), UDFT and OVGF calculations. We discuss metal-ligand bonding in the series of metal β-diketonato complexes on the basis of empirical arguments. The photoionization cross-sections and orbital energies of metal atoms must both be taken into account in order to rationalize changes in relative band intensities of the HeI/HeII spectra. 相似文献
50.
Branka Vranei Jelka Tomai Stainslav Smerdel Darko Kantoci Fabio Benedetti 《Helvetica chimica acta》1993,76(4):1752-1758
A novel type of compound that contains a peptide specific for bacterial peptidoglycans (immunomodulatory activity) and an adamantyl residue (antiviral activity) was synthesized. Thus, L -Ala-D -γGln was linked to DL -Gly(Ada) yielding two diasteroisomers 3a and 3b , i.e. ambo-Gly(Ada)-L -Ala-D -γGln (γGln = isoglutamine-4-amino-4-carbamoylbutanoic acid; Ada = adamantyl). The diastereoisomers were easily separated by column chromatography (silica gel) and characterized, but only the use of a stereospecific enzyme led to the assignment of the configuration of the Gly(Ada) moiety in the two diastereoisomers. The cytotoxic effect and antiviral activity of the novel adamantyltripeptides 3a and 3b , observed as the cell survival and the infectivity reduction of the influenza A virus H1N1 and H3N2 strains, respectively, were studied on MDCK cells in vitro. Both 3a and 3b exhibited low cytotoxicity for MDCK cells and reduced the infectivity of the influenza A virus strains, but to a different extent on different Strain. 相似文献