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41.
The mid-IR, far-IR, and Raman spectra of piperidine-3-carboxylic acid were measured and interpreted with support of the MP2 and B3LYP/6-311++G(d, p) calculated harmonic vibrational spectra. 10 stable piperidine-3-carboxylic acid tautomers/isomers were found after B3LYP, calculations. The experimental absorption bands of carboxylate (COO?) group show that the free piperidine-3-carboxylic acid molecule exists in zwitterionic form and the most stable tautomer (NAT-1) can be stabilized by an intramolecular N-H...O hydrogen bond. All vibrational frequencies of NAT-1 assigned in detail with the help of total energy distribution (TED). The experimental vibrational wave numbers were compared with the calculated data. 相似文献
42.
Saeid Zamiri Bernhard Reitinger Engelbert Portenkirchner Thomas Berer Enrique Font-Sanchis Peter Burgholzer Niyazi Serdar Sariciftci Siegfried Bauer Fernando Fernández-Lázaro 《Applied physics. B, Lasers and optics》2014,114(4):509-515
We present two laser ultrasonic receivers based on organic photorefractive polymer composites with 2-[4-bis(2-methoxyethyl)aminobenzylidene]malononitrile (AODCST) or 2-dicyanomethylen-3-cyano-5,5-dimethyl-4-(4′-dihexylaminophenyl)-2,5-dihydrofuran nonlinear optical chromophores. Experimental results show sensitivities of the ultrasonic receivers of ~9.5 × 10?8 nm (W/Hz)0.5 for both composites, and a faster response time (~60 ms) for the AODCST-based laser ultrasonic receiver. We show that such LUS detectors are highly suitable for contactless thickness measurements of aluminum, steel sheets and defect detection with an accuracy of 100 μm. 相似文献
43.
Y.G. Celebi R.L. Lichti B.B. Baker P.W. Mengyan H.N. Bani-Salameh E. Catak 《Physica B: Condensed Matter》2012,407(15):2879-2882
The motional and electrical properties of positively charged muonium (Mu+) centers in single crystal β-Ga2O3 are investigated via zero field muon spin relaxation (ZF-MuSR). Below room temperature we find two distinct shallow muonium centers with ionization energies of 7 and 16 meV. Above room temperature, at least three different Mu+ signals are resolved; two of these are metastable while the third shows characteristics of a stable ground state. As the temperature is elevated, metastable centers undergo several transitions. We obtain the relevant barrier energies associated with these site-change transitions. By 700 K, most muons occupy the mobile ground state, and an activation energy of about 1.65 eV is inferred for Mu+ diffusion from the hop rates obtained for this state. 相似文献
44.
B.B. Baker R.L. Lichti Y.G. Celebi P.W. Mengyan H.N. Bani-Salameh 《Physica B: Condensed Matter》2012,407(15):2864-2866
We report on a study of the motional characteristics of positively charged muonium defect centers in ZnO as an analog for H+ behavior. Muon spin depolarization measurements at zero applied magnetic field were completed from 20 K to 400 K, with preliminary results to 750 K. Results at the lower temperatures imply that Mu+ occupied two sites, and indicate local motion as thermally assisted tunneling with a characteristic energy of ∼60 meV, as well as a site change transition above 200 K with barrier energy ∼440 meV. Based on theoretical results, we have tentatively assigned these features to tunneling among three equivalent oxygen anti-bonding sites (AB⊥) and a transition to a lower-energy bond-centered site (BC‖) oriented along the c-axis. Preliminary fits suggest that global diffusion of muonium occurs above 400 K, with a diffusion barrier energy of ∼0.7 eV. 相似文献
45.
We demonstrate chip-scale flat-top filters at near-IR wavelengths using negative index photonic crystal based Mach-Zehnder interferometers. Supported by full three-dimensional numerical simulations, we experimentally demonstrate a new approach for engineering high-pass, low-pass, bandpass, and band-reject filters, based on designing the photonic band diagram both within the bandgap frequency region and away from it. We further show that our approach can be used to design filters that have tunable multilevel response for different sections of the spectrum and for different polarizations. This configuration enables deterministic control of the bandwidth and the rejection ratio of filters for integrated photonic circuits. 相似文献
46.
Daniel Ayuk Mbi Egbe Le Huong Nguyen Harald Hoppe David Mühlbacher Niyazi Serdar Sariciftci 《Macromolecular rapid communications》2005,26(17):1389-1394
Summary: The electrochemical behaviour of four types of (phenylene ethynylene)‐alt‐(phenylene vinylene) hybrid polymers, 1 , 2 , 3 , and 4 have been investigated with respect to the influence of the grafted alkoxy side chains. In the case of the fully substituted polymers 2 , 3 , and 4 , the strong insulating nature of longer linear octadecyl or bulky branched 2‐ethylhexyl side chains lowers the HOMO levels of the polymers thereby increasing the discrepancy, ΔEg, between the electrochemical, Eequation/tex2gif-stack-1.gif, and the optical, Eequation/tex2gif-stack-2.gif, bandgap energies. Thus it is not possible to establish a direct correlation between the open circuit voltage, VOC, of bulk heterojunction solar cell devices of the configuration glass substrate/ITO/PEDOT:PSS/polymer 3 :PCBM(1:3, w/w)/LiF/Al and the HOMO energy levels of polymer 3 solely, as postulated in the literature. The photovoltaic (PV) parameters greatly depend on the grafted side chains.
47.
Phenol degradation was carried out in acidic aqueous solution on different crystal structures of PbO2 surfaces at room temperature. Phenol, benzoquinone and maleic acid concentrations were monitored during the electrolysis process. It was determined that β surfaces have higher performance than surfaces on phenol degradation. Then, the effect of crystallinities of pure β-PbO2 surfaces was investigated and found that higher crystallinity increased the efficiency of the phenol degradation process. 相似文献
48.
Helmut Neugebauer N. Serdar Sariciftci Hans Kuzmany Adolf Neckel 《Mikrochimica acta》1988,94(1-6):265-268
The structure and the electrochemical oxidation reactions of polyaniline in an organic electrolyte are studied usingin-situ FTIR spectroscopy. In the first oxidation process a decrease of the N-H absorption band is observed, indicating a loss of hydrogen atoms. In the second oxidation step anion intercalation occurs. A broad absorption band at 4000 cm–1 is assigned to free carrier transitions in the conducting form of polyaniline. 相似文献
49.
Mojtaba Bagherzadeh Reyhaneh Kaveh Saim Ozkar Serdar Akbayrak 《Research on Chemical Intermediates》2018,44(10):5953-5979
In this paper, CdS nanoparticles as a visible light active photocatalyst were coupled by NiFe2O4 and reduced graphene oxide (rGO) to form CdS–NiFe2O4/rGO nanocomposite by facile hydrothermal methods. The CdS–NiFe2O4/rGO nanocomposite shows enhanced photocatalytic activity for the degradation of methylene blue (MB) under visible light illumination. In addition to improved photocatalytic performance, this prepared nanocomposite shows increased photostability and is magnetically separable from the aqueous media. The degradation rate constant (kapp) of the optimized photocatalyst, i.e. CdS–NiFe2O4 (0.05)/rGO 25 wt% nanocomposite, was higher than the corresponding CdS and NiFe2O4 nanoparticles by factors of 11.1 and 8.9, respectively. The synergistic interactions between CdS, NiFe2O4 and rGO lead to enhanced surface area, reduced aggregation of the nanoparticles, decreased the recombination of photogenerated electron–hole pairs, and increased the charge separation efficiency and effective electron–hole generation transfer. According to the obtained results, a proposed mechanism of the photodegradation of MB under visible light irradiation is finally mentioned. 相似文献
50.
Murat Çelik Cemalettin Alp M. Serdar Gültekin Metin Balci 《Tetrahedron letters》2006,47(22):3659-3663
1,2- and 1,3-Bis(trifluoroacetoxy) alcohols are easily obtained from the one-pot reaction of alkenes with phenyliodine(III) bis(trifluoroacetate) (PIFA) in the absence of any additive or catalyst. The products were converted into the corresponding diols by ammonolysis. The use of bicyclic alkenes has shown that rearranged 1,3-diacetoxy alcohols are mostly formed as the major products. 相似文献