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141.
Neng Liu Walid M. Hassen Jan J. Dubowski 《Applied Physics A: Materials Science & Processing》2014,117(1):37-41
Silicon (Si) wettability is one of the important parameters in the development of Si-based biosensing and lab-on-chip devices. We report on UV laser induced hydrophobicity of Si (001) wafers immersed in methanol during the irradiation with an ArF excimer laser. The irradiation with 800 pulses of the laser operating at 65 mJ/cm2 allowed to significantly increase the hydrophobicity of investigated samples as characterized by the static contact angle change from 77° to 103°. Owing to the irradiation with relatively low laser fluence, no measurable change in surface morphology of the irradiated samples has been observed with atomic force microscopy measurements. The nature of the hydrophobic surface of investigated samples is consistent with X-ray photoelectron spectroscopy analysis that indicates formation of Si–O–CH3 bonds on the surface of the laser-irradiated material. 相似文献
142.
Jaafar H Vileno B Thibon A Mandon D 《Dalton transactions (Cambridge, England : 2003)》2011,40(1):92-106
We report that the oxygen sensitivity of some Fe(II) complexes with tripodal ligands can be used, with benefit, in the oxidation of cyclohexane under mild conditions. Depending on the solvent, two very different reaction pathways are involved, which share the coordination of O(2) to the metal as the common initial step. We have synthesized a series of α-chlorinated tripods in the tris(2-pyridylmethyl)amine series Cl(n)TPA (n = 1-3) and fully characterized the corresponding FeX(2) complexes (X = Cl, CF(3)SO(3)). The single-crystal X-ray structure analyses of the FeCl(2) complexes are reported. In CH(3)CN, the FeCl(2) complexes react smoothly with O(2), whereas the Fe(CF(3)SO(3))(2) complexes are non-sensitive. In CH(3)CN, the reaction of the oxygen-sensitive Cl(n)TPAFeCl(2) (n = 0-3) with O(2), acetic acid and zinc amalgam, in the presence of cyclohexane, affords a mixture of cyclohexanol/one in an ≈ ol/one ratio of 3.1 and a selectivity of the C3°/C2° in the adamantane conversion that is consistent with a metal-oxo based oxidation. Limited efficiency (≈ 2 TON) was observed for the parent TPAFeCl(2) complex and Cl(1)TPAFeCl(2), whereas both other complexes turned out to be poorly active. The TPAFeCl(2) complex was used to address mechanistic questions: when the reaction was carried out in pyridine, the ol/one ratio shifted to 0.15 while efficiency was improved by 7-fold. In pyridine and in the presence of a spin trap (DMPO), the radical-based character of the reaction was definitely established, by contrast with acetonitrile, where no oxygenated radicals were detected. Thus, the reactivity differences arise from involvement of two distinct active species. The dichotomous radical/biomimetic pathway is discussed to interpret these results. 相似文献
143.
Tchicama Mella Mamane Zied Hassen Béchir Hajjem 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2854-2864
The cyanomethylphosphonates 1 and the ethyl phosphoacetates 2 were reacted with some fluorophenylisothiocyanates to give the 2-thioxoethylphosphonates 3 in tautomeric equilibrium with the corresponding 2-mercaptovinylphosphonates 3 ′ and the 2-phosphoryl-3-thioxopropanoates 4 , respectively. Reaction of the cyanomethylphosphonates 1 with fluorophenylisothiocyanates in presence of methyliodide furnished the 2- thiometylvinylphosphonates 5 . The 2-mercaptovinylphosphonates 3 ′ reacted with ethyl chloroacetate in refluxing ethanol in the presence of triethylamine to give S-substitued derivatives 6 . 相似文献
144.
The living polymerization of p‐tert‐butoxystyrene (tBuOS) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) 60/40 v/v solvent mixture at –80°C. The model initiator 1,1,‐ditolylethylene (DTE) capped 2‐chloro‐2,4,4‐trimethylpentane (TMPCl) was formed in situ in conjunction with TiCl4. Lowering the Lewis acidity by the addition of Ti(OIp)4 was necessary to induce a rapid and controlled polymerization of tBuOS. Well‐defined polymers with controlled molecular weights, however, were only obtained at a narrow [Ti(OIp)4]/[TiCl4]=0.83–0.86 ratio. Above this ratio, the polymerization of tBuOS was slow and became absent at [Ti(OIp)4]/[TiCl4]≥1.18. At ratios lower than 0.83, the polymerization was too rapid and the initiator efficiency was lower than 100%. The living polymerization of tBuOS was also studied with SnBr4 as Lewis acid. After capping TMPCl with DTE, Ti(OIp)4 was added to reach [Ti(OIp)4]/[TiCl4]=1.2, followed by the addition of tBuOS and SnBr4. SnBr4 induced a well‐controlled living polymerization approximately first order in [SnBr4], and the polymers exhibited close to theoretical M ns and low polydispersity indices (PDI<1.2). The success of the method was also demonstrated by the clean synthesis of poly(isobutylene‐b‐p‐tert‐butoxystyrene) PIB‐b‐PtBuOS diblock copolymers. PtBuOS‐b‐PIB‐b‐PtBuOS triblock copolymer thermoplastic elastomers were prepared by employing 5‐tert‐butyl‐1,3‐bis(1‐methoxy‐1‐methylethyl)benzene (DCE) as a difunctional initiator for the living polymerization of IB followed by capping with DTE and substitution of TiCl4 with SnBr4 for the polymerization of tBuOS. Deprotection of the triblock copolymer in the presence of catalytic amount of HCl yielded poly(p‐hydroxystyrene‐b‐isobutylene‐b‐p‐hydroxystyrene) (PHOS‐b‐PIB‐b‐PHOS). PHOS‐b‐PIB‐b‐PHOS with 39.3 wt% p‐hydroxystyrene content exhibited typical characteristic of a thermoplastic elastomers (TPEs) with tensile strength of 18 MPa and ultimate elongation of 300%. 相似文献
145.
Sabri Messaoudi Bechir Bejaoui Fourat Akrout Malika Bel Hassen Cherif Sammari 《International journal of quantum chemistry》2013,113(11):1633-1640
The heterogeneous uptake of N2O5 on mineral dust particles may play an important role in the removal of nitrogen oxides from the atmosphere. However, the reaction of N2O5 with the mineral particles is not well understood. The reaction of N2O5 with two Si(OH)4 monomers is explored using theoretical methods. This study represents a first step towards understanding the interaction of N2O5 with the hydroxyl groups of silica particles. Energies are calculated using MP2 single point calculations on the B3LYP optimized geometries and including B3LYP thermodynamic corrections. Four mechanisms are considered for the formation of two HNO3 and one H6Si2O7. The rate limiting activation barrier of the most favorable path is found to be 12.5 kcal mol?1. This reaction appears to be more favorable than the hydrolysis of N2O5 with one water molecule. These results are in agreement with experimental observations, which show that N2O5 reacts with OH groups of Saharan dust to form nitrate. © 2012 Wiley Periodicals, Inc. 相似文献
146.
The reaction of 3,3-dimethyl-7-nitro-3,4-dihydroisoquinoline 1 with m-chloroperbenzoic acid (m-CPBA) mainly yielded oxaziridine and nitrone, with their selectivities being dependent on the solvents. The reaction with 2.5 equivalents of m-CPBA gave small amounts of oxaziridines and hydroxamic acids as well as isolated O-acylhydroxamate compounds. 相似文献
147.
148.
S. Hamdi S. Ouni H. Chaker J. Rohlicek R. Ben Hassen 《Journal of solid state chemistry》2011,184(11):2897-2901
A new compound DySr5Ni2.4Cu0.6O12−δ has been prepared by sol gel method and annealed at 1473 K in 1 atm of Ar gas flow. The X-ray diffraction (XRD) is used for phase identification. The sample shows to adopt the K2NiF4-type structure based on tolerance factor calculation. XRD analysis using the Rietveld method was carried out and it was found that DySr5Ni2.4Cu0.6O12−δ (Dy0.33Sr1.67Ni0.8Cu0.2O4−δ′) compound crystallizes in tetragonal symmetry with space group I4/mmm (Z=2). The lattice parameters are found to be at room temperature a=3.7696(5) Å and c=12.3747(2) Å. The final reliability indices were: RB=5.219% and χ2=3.47. Four probe electrical resistivity measurements were performed versus temperature in the range 294–579 K. A semiconducting behaviour over the whole range of temperature, with a conductivity maximum of 0.4 S cm−1 is observed at 510 K. 相似文献
149.
Samia Yahyaoui Rached Ben Hassen Vaclav Petí
ek Michal Duek Abdelhamid Ben Salah 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(3):i24-i26
The ternary system SrBr2–CdBr2–H2O was investigated at room temperature. The title phase, SrCd2Br6·8H2O, has been isolated from this system and its structure determined by single‐crystal X‐ray diffraction. The structure consists of infinite double chains of CdBr6 octahedra and chains of Sr(H2O)9 polyhedra packed along the b axis. The interaction between these two isolated chains occurs through O—H⃛O and O—H⃛Br hydrogen bonds. The structure is compared with that of SrCd2Cl6·8H2O. 相似文献
150.