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131.
A novel micro force balance (MFB) is used to investigate the rupture energy of a silicon oil liquid bridge formed in water between two glass particles of either the same or dissimilar surface energy. Rupture energies are integrated from force curves and compared with the models proposed by Simons et al. (Chem. Eng. Sci. 49 (1994) 2331) and Pitois et al. (Eur. Phys. J. B 23 (2001) 79). The latter showed slightly better agreement to the experimental data. Glass ballotini ( approximately 100 microm diameter) are either silanized, in order to increase their wettability toward the oil binder, or kept untreated. Results showed how the interaction between the binder and the particle influences the geometry, the capillary pressure, the force, and the rupture energy of the liquid bridge. Higher values of force and liquid bridge energy were measured between particles characterized by higher interaction (silanized-silanized configuration). A thermodynamic approach to the evaluation of the energy stored in a liquid bridge is also proposed. The mechanical work done to stretch apart the liquid bridge is evaluated as the difference of internal and hysteresis energy between the initial and the rupture configuration of the bridge. This approach showed good agreement with the experimental data only for liquid bridges formed between silanized and untreated glass particles. 相似文献
132.
133.
The vibroluminescence of N2O excited by activated nitrogen is studied under high resolution using a SISAM spectrometer in the 4.7 μ region. For the first time a Treanor-type distribution is applied to the vibrational population of the ν3 mode which shows a non-Boltzmann distribution. 相似文献
134.
Emission spectra of CO2 vibrationally excited by a dc electric discharge were recorded under Doppler-limited resolution, using the high information interferometer of Laboratoire d'Infrarouge Orsay, France, in the spectral region 4–5 μm. Sixteen bands with Δv3 = 1 of 12C16O2 involving the Fermi dyads (100v3, 020v3)I and II and (111v3, 031v3)I and II have been studied. The band centers and the spectroscopic constants for all the vibrational levels involved are given. They reproduce the experimental wavenumbers with a rms of the order of 4 × 10?5 cm?1 for the best vibrational transition and always less than 3 × 10?4 cm?1 for the others. These results are compared with laser measurements for the (1000, 0200) dyad. 相似文献
135.
Emission spectra of six isotopic species of CO2 excited by dc discharge were recorded under Doppler limited resolution using the Fourier transform spectrometer of the Laboratoire d'Infrarouge in the 4.5-μm region. In this paper, the results concerning 12C16O18O are given. The band centers and the spectroscopic constants for 19 levels involved in vibrational transitions Δv3 = 1 are reported. They reproduce 853 experimental wavenumbers with a RMS of the order of 2 × 10?5 cm?1 for the best vibrational transition, less than 1 × 10?4 cm?1 for most of the others. From experimental wavenumbers, to determine molecular parameters, it is shown that it is impossible to include in the same fit all the transitions Σ-Σ until v3 = 10 using a polynomial representation of the rovibrational energy, the responsible phenomenon being the small Fermi resonance which occurs on Σ levels. Nevertheless, the 321 wavenumbers belonging to the first four vibrational transitions are satisfactorily reproduced by the model. 相似文献
136.
Burman R Herrmann A Tran R Kivelä JE Lomize A Gullbo J Göransson U 《Organic & biomolecular chemistry》2011,9(11):4306-4314
The cyclotides are a family of circular and knotted proteins of natural origin with extreme enzymatic and thermal stability. They have a wide range of biological activities that make them promising tools for pharmaceutical and crop-protection applications. The cyclotides are divided into two subfamilies depending on the presence (M?bius) or absence (bracelet) of a cis-Pro peptide bond. In the current work we report a series of experiments to give further insight into the structure-activity relationship of cyclotides in general, and the differences between subfamilies and the role of their hydrophobic surface in particular. Selective chemical modifications of Glu, Arg, Lys and Trp residues was tested for cytotoxic activity: derivatives in which the Trp residue was modified showed low effect, demonstrating the existence of a connection between hydrophobicity and activity. However, over the full set of cyclotides examined, there was no strong correlation between the cytotoxic activity and their hydrophobicity. Instead, it seems more like that the distribution of charged and hydrophobic residues determines the ultimate degree of potency. Furthermore, we found that while the Glu residue is very important in maintaining the activity of the bracelet cyclotide cycloviolacin O2, it is much less important in the M?bius cyclotides. Despite these differences between cyclotide subfamilies, a systematic test of mixtures of cyclotides revealed that they act in an additive way. 相似文献
137.
The physical-chemical properties of some nanostructured perovskite-like catalysts of general formula La(1-x)M(x)MnO(3+δ) (M = Ce, Sr) have been investigated, in particular by using the electron paramagnetic resonance (EPR) technique. We show that the interplay between the -O-Mn(3+)-O-Mn(4+)-O- electron double-exchange and the electron mobility is strictly dependent on the dopant nature and the annealing conditions in air. A relationship between the observed properties of these samples and their activity in the methane flameless catalytic combustion is proposed. 相似文献
138.
Ellen Denise P. Almeida Adjane A. Costa Mairim R. Serafini Fábia C. Rossetti Juliana M. Marchetti Victor Hugo V. Sarmento Rogéria de S. Nunes Mário Ernesto G. Valerio Adriano A.S. Araújo Ana Amélia M. Lira 《Journal of Thermal Analysis and Calorimetry》2012,108(1):191-196
Solid lipid nanoparticles (SLN) without drug and SLN loaded with chloroaluminum phthalocyanine (AlClPc) were prepared by solvent
diffusion method in aqueous system and characterized by thermal analyses and X-ray diffraction (XRD) in this study. Determination
of particle size, zeta potential (ZP), and encapsulation efficiency were also evaluated. SLN containing AlClPc of nanometer
size with high encapsulation efficiency and ZP were obtained. The results indicated that the size of SLN loaded with AlClPc
is larger than that of the inert particle, but ZP is not changed significantly with incorporation of the drug. In differential
scanning calorimetry (DSC) curves, it was observed that the melting point of stearic acid (SA) isolated and in SLN occurred
at 55 and 64 °C, respectively, suggesting the presence of different polymorphs. DSC also shows that the crystallinity state
of SLN was much less than that of SA isolated. The incorporation of drug in SLN may have been favored by this lower crystallinity
degree of the samples. XRD techniques corroborated with the thermal analytic techniques, suggesting the polymorphic modifications
of stearic acid. 相似文献
139.
Latronico M Mastrorilli P Gallo V Dell'Anna MM Creati F Re N Englert U 《Inorganic chemistry》2011,50(8):3539-3558
The protonation of the phosphinito-bridged Pt(I) complex [(PHCy(2))Pt(μ-PCy(2)){κ(2)P,O-μ-P(O)Cy(2)}Pt(PHCy(2))](Pt-Pt) (1) by aqueous HBF(4) or hydrofluoric acid leads selectively to the hydrido-bridged solvento species syn-[(PHCy(2))(H(2)O)Pt(μ-PCy(2))(μ-H)Pt(PHCy(2)){κP-P(OH)Cy(2)}](Y)(2)(Pt-Pt) ([2-H(2)O]Y(2)) {Y = BF(4), F(HF)(n)} when an excess of acid was used. On standing in halogenated solvents, complex [2-H(2)O](BF(4))(2) undergoes a slow but complete isomerization to [(PHCy(2))(2)Pt(μ-PCy(2))(μ-H)Pt{κP-P(OH)Cy(2)}(H(2)O)](BF(4))(2)(Pt-Pt) ([4-H(2)O][BF(4)](2)) having the P(OH)Cy(2) ligand trans to the hydride. The water molecule coordinated to platinum in [2-H(2)O][BF(4)](2) is readily replaced by halides, nitriles, and triphenylphosphane, and the acetonitrile complex [2-CH(3)CN][BF(4)](2) was characterized by XRD analysis. Solvento species other than aqua complexes, such as [2-acetone-d(6)](2+) or [2-CD(2)Cl(2)](2+) were obtained in solution by the reaction of excess etherate HBF(4) with 1 in the relevant solvent. The complex [2-H(2)O](Y)(2) [Y = F(HF)(n)] spontaneously isomerizes into the terminal hydrido complexes [(PHCy(2))Pt(μ-PCy(2)){κ(2)P,O-μ-P(O)Cy(2)}Pt(H)(PHCy(2))](Y)(Pt-Pt) ([6](Y)). In the presence of HF, complex [6](Y) transforms into the bis-phosphanido-bridged Pt(II) dinuclear complex [(PHCy(2))(H)Pt(μ-PCy(2))(2)Pt{κP-P(OH)Cy(2)}](Y)(Pt-Pt) ([7](Y)). When the reaction of 1 with HF was carried out with diluted hydrofluoric acid by allowing the HF to slowly diffuse into the dichloromethane solution, the main product was the linear 60e tetranuclear complex [(PHCy(2)){κP-P(O)Cy(2)}Pt(1)(μ-PCy(2))(μ-H)Pt(2)(μ-PCy(2))](2)(Pt(1)-Pt(2)) (8). Insoluble compound 8 is readily protonated by HBF(4) in dichloromethane, forming the more soluble species [(PHCy(2)){κP-P(OH)Cy(2)}Pt(1)(μ-PCy(2))(μ-H)Pt(2)(μ-PCy(2))](2)(BF(4))(2)(Pt(1)-Pt(2)) {[9][BF(4)](2)}. XRD analysis of [9][BF(4)](2)·2CH(2)Cl(2) shows that [9](2+) is comprised of four coplanar Pt atoms held together by four phosphanido and two hydrido bridges. Both XRD and NMR analyses indicate alternate intermetal distances with peripheral Pt-Pt bonds and a longer central Pt···Pt separation. DFT calculations allow tracing of the mechanistic pathways for the protonation of 1 by HBF(4) and HF and evaluation of their energetic aspects. Our results indicate that in both cases the protonation occurs through an initial proton transfer from the acid to the phosphinito oxygen, which then shuttles the incoming proton to the Pt-Pt bond. The different evolution of the reaction with HF, leading also to [6](Y) or 8, has been explained in terms of the peculiar behavior of the F(HF)(n)(-) anions and their strong basicity for n = 0 or 1. 相似文献
140.