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991.
Chemical characterisation has been carried out on 25 quarry marbles collected from Marmara, Aegean and Thrace regions of Turkey. Ten elements were determined by capillary electrophoresis (CE). Principal component analysis and cluster analysis techniques were utilised to define grouping of different marble samples. These techniques showed that the analysed marbles were differentiable mainly by provenance. Experimental conditions such as pH, applied voltage and concentration of α-hydroxyisobutyric acid (HIBA) were optimised to achieve the best separation of metal ions using central composite design. The optimum pH 3.7, applied voltage 15 kV and concentration of HIBA 10 mM were found to provide the best separation for all metal ions investigated. 相似文献
992.
Sintering behavior and bioactivity of diopside, CaMgSi2O6, prepared by a coprecipitation process were examined for its biomedical applicability. As-prepared powder was synthesized by adding aqueous ammonia to an ethanol solution containing Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, and Si(OC2H5)4 and characterized by means of TG–DTA, XRD, and TG–MS. The dried powder was X-ray amorphous and crystallized into diopside at 845.5 °C. The glass network formation by SiO4 tetrahedra was almost completed below 800 °C. The bioactivity of the diopside prepared by sintering the compressed powder at 1100 °C for 2 h was evaluated by immersion of the sintered body in a simulated body fluid (SBF) at 36.5 °C. Leaf-like apatite particles were found to be formed on the surface of the sintered body and grew with passage of soaking time. This apatite-forming behavior in the SBF is related to the dissolution of Ca(II) ions from the sintered body in the early stage of immersion. Thus, diopside prepared by the coprecipitation process using the metal alkoxide and the metal salts was found to have an apatite-forming ability. 相似文献
993.
Silicon (Si) is a prime candidate for manufacturing water-splitting photoelectrochemical cells, however, the stability of this material remains a serious bottleneck. This is particularly true for the photoanode, subject to severe deactivation mechanisms. So far, thin film homogeneity has been the paradigm in the quest for stable and efficient Si-based photoanodes, which involved the use of vapor deposition methods to produce conformal thin films ensuring Si protection and efficient catalysis during operation. Conversely, recent reports on n-Si/metal thin film junctions have highlighted the benefits of the junction heterogeneity, generated in situ. In addition, results obtained from n-Si photoanodes partially covered with discontinuous films of Co and Ni nanoparticles lately suggested that homogeneity is not a prerequisite to reach efficiency and stability. Such findings may open new protection routes for Si-based photoanodes, breaking with classical strategies and allowing the use of liquid phase modification methods such as electrodeposition. 相似文献
994.
Oxymethylcrowned spirobenzopyran 1 and pyrenylspirobenzopyran 2 were synthesized, and fluorescence emission of their corresponding merocyanine form was examined in the presence of metal ions. For 2, fluorescence emission derived from the pyrene moiety was completely quenched by photoinduced electron transfer (PET) of the nitrogen atom when the merocyanine form was not produced, namely, without metal ions. However, when 2 was converted to the merocyanine form by the complexation of its crown ether with a metal ion, fluorescence resonance energy transfer (FRET) from the pyrene to the merocyanine moieties took place to produce fluorescence emission. This result demonstrates that the spirobenzopyran isomerization can function as a fluorescence emission switch. Fluorescence quantum yield measurement for 1 and 2 showed that fluorescence emission depends on the binding metal ion in which the fluorescence quantum yield generally increased with the increase of metal ion radius. 相似文献
995.
Strictly size-controlled metal nanoclusters of palladium(0) and gold(0) can be easily formed in the organic component of an
organic-inorganic composite between a gel-type resin (DV44) and silica. To this purpose, silica is impregnated at incipient
wetness with a solution of the required co-monomers (N,N-dimethylacrylamide, 4-vinylpyridine and N,N′-methylene-bis-acrylamide), which are co-polymerized to give the composite. The silica-supported polymeric framework is then
loaded with palladium(II) or gold(III) precursors. Their chemical reduction with aqueous solutions of sodium boronhydride
yields the metal nanoclusters. Their size is controlled by the nanomorphology of the polymeric framework, which acts as a
template during the nanocluster growth (Template Controlled Synthesis). Upon thermal decomposition of the polymeric template
at 600°C under nitrogen, the nanostructured metals are deposited onto the silica surface. In the case of palladium the final
step occurs with retention of the original size of the nanoclusters. 相似文献
996.
Anthony D. Patrick Pamela Williams Estela Blaisten-Barojas 《Journal of Molecular Structure》2007,824(1-3):39-47
Small carbon clusters C, C2 and C3 metallized with beryllium were studied by first principles within the hybrid density functional approach with generalized gradient correction. Cluster isomer structures for the ground state and several excited states where systematically calculated for CxBey with x = 1–3 and y = 1–4 including the vibrational analysis of all states. Ionization potentials and electron affinities are calculated for the ground state cluster isomers. The thermal stability of the ground state isomers was verified within the harmonic approximation of the Helmholtz free energy up to temperatures of about 1000 K. Within the family of clusters studied, C2Be3 undergoes a solid-like structural transition at about 260 K changing from a planar structure at low temperatures to a linear isomer at high temperatures. 相似文献
997.
998.
The synthesis and structure of a chiral 1D aluminophosphate chain compound: d-Co(en)3[AlP2O8]·6.5H2O
A new chiral one-dimensional (1D) aluminophosphate chain compound [d-Co(en)3][AlP2O8]·6.5H2O (designated AlPO-CJ22) has been hydrothermally synthesized by using the optically pure d-Co(en)3I3 complex as the template. Single-crystal structural analysis reveals that its structure is built up from alternating connection of AlO4 and PO2(=O2) tetrahedra to form corner-shared Al2P2 four-membered ring (4-MR) chains. The d-Co(en)33+ complex cations extended along the 21 screw axis interact with the inorganic chains through hydrogen-bonds of N?O atoms in a helical fashion. Optical rotation measurement shows that AlPO-CJ22 is chiral as with d-Co(en)33+ complex cations. Crystal data: orthorhombic, I212121, , , , Z=8, R1=0.067, wR2=0.1291, and Flack parameter: −0.02(3). CCDC number: 254179. 相似文献
999.
Mohammad H.?HabibiEmail author A.?Zeini Isfahani A.?Mohammadkhani M.?Montazerozohori 《Monatshefte für Chemie / Chemical Monthly》2004,135(9):1121-1127
Summary. Photooxidation of ethylbenzene with oxygen to give ethylbenzene hydroperoxide has been achieved in a stirred photochemical reactor that was cooled by a water system by irradiation with a 400W high-pressure mercury lamp and using TiO2 powder and metal coated TiO2. The effects of the amount of copper or silver coated on TiO2 and of the temperature on the rate of oxidation have been investigated. It is suggested that thermal cleavage of the O–O bond and photochemically generated singlet oxygen should be considered as the initiating step in a radical chain mechanism. An optimum loading of 6% Ag or 4–5% Cu was observed for photooxidation of ethylbenzene. 相似文献
1000.
Pedro Oliver Dunstan 《Thermochimica Acta》2004,409(1):19-24
The compounds [MBr2(pyNO)n] (where M: Mn, Fe, Co, Ni, Cu or Zn; pyNO is pyridine N-oxide and n=2, 3 or 6) were synthesized and characterized by melting points, elemental analysis, thermal analysis and electronic and IR spectroscopy. The enthalpies of dissolution of the adducts, metal(II) bromides and pyNo in methanol were measured and by using thermochemical cycles, the following thermochemical parameters for the adducts have been determined: the standard enthalpies for the Lewis acid/base reactions (ΔrHθ), the standard enthalpies of formation (ΔfHθ), the standard enthalpies of decomposition (ΔDHθ), the lattice standard enthalpies (ΔMHθ) and the standard enthalpies of the Lewis acid/base reactions in the gaseous phase (ΔrHθ(g)). The mean bond dissociation enthalpies of the M(II)-oxygen bonds () have been estimated. 相似文献