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排序方式: 共有177条查询结果,搜索用时 31 毫秒
31.
32.
M. Oshima B.B. Pate Z.M. Lu P.J. Jupiter I. Lindau W.E. Spicer 《Solid State Communications》1983,46(11):815-818
The alloy formation and oxidation of a Nb-rich Nb-Al alloy has been studied using core level photoemission in combination with synchroton radiation as a surface sensitive probe. Exactly the same chemical shifts were observed from both the Nb-Al alloy and an Al-evaporated Nb surface, indicating similar structural arrangements. It is found that the oxidation rate of Nb in these structures is drastically decreased in comparison to either pure Nb metal or Nb3Sn. Two stages in the oxidation of the Nb-Al alloy are clearly distinguished by chemical shifts of the Al2p, Nb4p and O2p levels. 相似文献
33.
I. Lindau P. Pianetta W.E. Spicer P.E. Gregory C.M. Garner P.W. Chye 《Journal of Electron Spectroscopy and Related Phenomena》1978,13(3):155-160
The surface electronic structure of cleaved GaAs (110) is found to be very sensitive to small amounts of adsorbed oxygen. For example, adsorbing oxygen on only a few percent of the surface Ga or As atomic sites can produce changes of a factor of two in the surface electronic structure. Thus, long range effects must be involved, and these are associated with rearrangement of the surface atoms. 相似文献
34.
M. B. Tsetlin A. A. Zakharov A. P. Menushenkov A. A. Ivanov M. N. Mikheeva I. Lindau 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2008,2(6):928-930
The surface of epitaxial Nd1.85Ce0.15CuO4 ? y (001) (NCCO) film has been studied by low energy electron diffractometry (LEED) and photoelectron spectroscopy. Ar+ ion etching of a surface with subsequent annealing in oxygen at atmosphere pressure has been found to lead to the ordered structure restoration of surface layers with the symmetry type and lattice parameters corresponding to the NCCO phase. Annealing in vacuum at temperatures close to the boundary of thermodynamic phase stability results in the formation of epitaxial Ce0.5Nd0.5O1.75 phase on a surface that is indicated in the LEED pattern as additional spots corresponding to the surface lattice (√2 × √2)R45°. 相似文献
35.
Competition between lipases and monoglycerides at interfaces 总被引:3,自引:0,他引:3
Reis P Holmberg K Miller R Krägel J Grigoriev DO Leser ME Watzke HJ 《Langmuir : the ACS journal of surfaces and colloids》2008,24(14):7400-7407
Tensiometry (the pendant drop technique), interfacial shear rheology, and ellipsometry have been used to study the effect of polar lipids that are generated during fat digestion on the behavior of lipases at the oil-water interface. Both Sn-1,3 regiospecific and nonregiospecific lipases have been used, and a noncatalytically active protein, beta-lacloglobulin, has been used as reference in the interfacial shear rheology experiments. The results from the pendant drop measurements and the interfacial rheology studies were in agreement with each other and demonstrated that the Sn-2 monoglyceride, which is one of the lipolysis products generated when a Sn-1,3 regiospecific lipase catalyzes triglyceride hydrolysis, is very interfacially active and efficiently expels the enzyme from the interface. Ellipsometry conducted at the liquid-liquid interface showed that the lipase forms a sublayer in the aqueous phase, just beneath the monoglyceride-covered interface. Sn-1/3 monoglycerides do not behave this way because they are rapidly degraded to fatty acid and glycerol and the fatty acid (or the fatty acid salt) does not have enough interfacial activity to expel the lipase from the interface. Since the lipases present in the gastrointestinal tract are highly Sn-1,3 regiospecific, we believe that the results obtained can be transferred to the in vivo situation. The formation of stable and amphiphilic Sn-2 monoglycerides can be seen as a self-regulatory process for fat digestion. 相似文献
36.
Krejci Pavel; Rocca Elisabetta; Sprekels Jurgen 《Journal London Mathematical Society》2007,76(1):197-210
We propose a model for non-isothermal phase transitions withnon-con-served order parameter driven by a spatially non-localfree energy with respect to both the temperature and the orderparameter. The resulting system of equations is shown to bethermodynamically consistent and to admit a strong solution. 相似文献
37.
Jurgen Lange Natalia Davidenko Roberto Sastre 《Macromolecular theory and simulations》2009,18(9):511-527
Mathematical modeling of the thermopolymerization of FM and CMFMA was carried out using a cross‐linked kinetic model proposed for the photo‐initiated polymerization of acryl‐furanic compounds. In this model, the photochemical initiation step was substituted by a thermal one and it was assumed that the constant of radical termination was time‐dependent, which allowed the gel effect (Trommsdorff) at high monomer conversion to be simulated. Optimization of all kinetic constants was achieved and the results of simulation suitably fitted the experimental data of the monomer conversion. The contribution of each step in the mechanism and its dependence on the experimental conditions were estimated by a sensitivity analysis technique.
38.
M. B. Tsetlin A. A. Zakharov K. I. Maslakov M. N. Mikheeva I. Lindau 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2009,3(5):752-755
The process of an ultrahigh vacuum annealing of a diamond-like carbon film deposited on a silicon substrate has been studied
in situ using a photoemission microscope mounted at the MAX-lab synchrotron’s radiation source. After the annealing the film
was examined ex situ using an atomic force microscope. It is revealed that the graphitization of the film occurs and round
formations of several microns in size with a core of ∼0.2 μm in size appear on its surface at the temperature exceeding 1000°C.
Photoemission images of these formations have shown the presence of silicon on their surface. Apparently, the interaction
between the carbon film and silicon substrate begins in the middle of the formation and spreads to the adjacent region at
the following stage. 相似文献
39.
Christoph Behrendt Jurgen Heck Michael J. McGlinchey 《Journal of organometallic chemistry》2006,691(6):1183-1196
The aldol condensation reaction between [Co(η4-C4Ph4){η5-C5H4C(O)CH3}] and a range of aromatic aldehydes [RCHO] and [RCHCH-CHO] gives a series of α,β-unsaturated ketones [Co(η4-C4Ph4){η5-C5H4C(O)CHCH-R}] and [Co(η4-C4Ph4){η5-C5H4C(O)CHCH-CHCH-R}] (3). The reaction is promoted by various bases: NaH proved to be the most effective whilst nBuLi gave [Co(η4-C4Ph4){η5-C5H4C(OH)(nBu)CH3}] as the major product. NaOH was ineffective, perhaps indicating that that the methyl protons in [Co(η4-C4Ph4){η5-C5H4C(O)CH3}] are less acidic than those in [Fe(η5-C5H5){η5-C5H4C(O)CH3}]. Compounds 3 were characterised spectroscopically. Their 1H NMR spectra are consistent with a trans configuration about their CC bond, and this was confirmed by X-ray crystallography in five cases, which showed that all have the same basic structure with parallel cyclobutadiene and cyclopentadienyl ligands, but they are not identical. The C5H4C(O)(CHCH)n-R (n = 1 or 2) moieties show little evidence for delocalisation and often deviate from planarity. The UV/Vis spectra of those 3 with smaller aromatic rings (R = C6H5, 4-C6H4NMe2, 2-C4H3S and 1-C10H7) suggest that these are donor-π-acceptor systems, but as the annellation of R increases (R = 9-C14H9, 1-C16H9 and 1-C20H11) the spectra increasingly resemble those of the parent polycyclic aromatic hydrocarbon, RH. Reduction of [Co(η4-C4Ph4){η5-C5H4C(O)CHCH-C10H7-1}] with DIBAL gives a mixture of [Co(η4-C4Ph4){η5-C5H4C(O)CH2CH2-C10H7-1}] and [Co(η4-C4Ph4){η5-C5H4CH(OH)CHCH-C10H7-1}]. A minor product from the preparation of [Co(η4-C4Ph4){η5-C5H4C(O)CH3}] was shown by X-ray crystallography to be the η4-butadiene complex [Co{η4-Ph(H)CC(Ph)-C(Ph)C(H)Ph}{η5-C5H4C(O)CH3}]. 相似文献
40.
D. D. Sarma F. U. Hillebrecht M. Campagna C. Carbone J. Nogami I. Lindau T. W. Barbee L. Braicovich I. Abbati B. De Michelis 《Zeitschrift für Physik B Condensed Matter》1985,59(2):159-165
We present X-ray absorption spectra (XAS) obtained with synchrotron radiaton at the PdL
2,3 edges of Pd–Al alloys and Bremsstrahlung Isochromat Spectra (BIS) at 1,486.7 eV of Pd–Al alloys and of Pd2Si. The XAS and BIS results for the alloys are very similar indicating that the effect of the core potential (e.g. many-body, electronhole excitation) is negligible. The BIS results on Pd2Si show differences with respect to Pd–Al due to the more localized bonds. The comparison between XAS and BIS data in Pd2Si is still an open problem and might indicate a more subtle role of the core-hole potential. 相似文献