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排序方式: 共有159条查询结果,搜索用时 15 毫秒
111.
Dr. Elie Geagea Ali Hamadeh Judicaël Jeannoutot Prof. Dr. Frank Palmino Nicolas Breault Prof. Dr. Alain Rochefort Dr. Samar Hajjar-Garreau Prof. Dr. Carmelo Pirri Prof. Dr. Christophe M. Thomas Dr. Frédéric Chérioux 《Chemphyschem》2023,24(15):e202300182
We demonstrate that the strong N2 bond can be efficiently dissociated at low pressure and ambient temperature on a Si(111)-7x7 surface. The reaction was experimentally investigated by scanning tunnelling microscopy and X-ray photoemission spectroscopy. Experimental and density functional theory results suggest that relatively low thermal energy collision of N2 with the surface can facilitate electron transfer from the Si(111)-7x7 surface to the π*-antibonding orbitals of N2 that significantly weaken the N2 bond. This activated N2 triple bond dissociation on the surface leads to the formation of a Si3N interface. 相似文献
112.
Samar Jyoti Kalita 《Applied Surface Science》2011,257(9):3985-3997
Friction stir welding is a promising solid state joining process for high strength aluminum alloys. Though friction stir welding eliminates the problems of fusion welding as it is performed below melting temperature (Tm), it creates severe plastic deformation. Friction stir welds of some aluminum alloys exhibit relatively poor corrosion resistance. This research enhanced the corrosion properties of such welds through diode laser surface melting.A friction stir weld of aluminum alloy 2024 T351 was laser melted using a 1 kW diode laser. The melt-depth and microstructure were investigated using optical and scanning electron microscopy. The melt zone exhibited epitaxially grown columnar grains. At the interface between the melted and the un-melted zone, a thick planar boundary was observed. Energy dispersive spectroscopy analyzed the redistribution of elemental composition. The corrosion properties of the laser melted and native welds were studied in aqueous 0.5 M sodium chloride solution using open circuit potential and cyclic potentiodynamic polarization. The results show noticeable increase in the pit nucleation resistance (390 mV) after the laser surface treatment. The repassivation potential was nobler to the corrosion potential after the laser treatment, which confirmed that the resistance to pit growth was improved. 相似文献
113.
Sarma M Chatterjee T Vindhya H Das SK 《Dalton transactions (Cambridge, England : 2003)》2012,41(6):1862-1866
Anionic metathesis reaction between the perchlorate salt of a copper-tetraazamacrocycle complex and the tetrabutylammonium salt of Lindqvist-type isopolyoxometalates in acetonitrile leads to the formation of two new inorganic-organic hybrid solids formulated as [Cu(L)(MeCN)][W(6)O(19)] (1) and [Cu(L)(MeCN)][Mo(6)O(19)] (2). Interestingly, both ion-pair complexes crystallize in a chiral space group P2(1)2(1)2(1). Crystallographic analysis of the obtained compounds reveals the occurrence of spontaneous resolution during crystallization. Both the enantiomorphs of compound 1 have been structurally characterized, whereas the resolution of compound 2 is rather poor. 相似文献
114.
Erdem Kilic Sadia Samar Ali Gerhard Wilhelm Weber Rameshwar Dubey 《Optimization》2014,63(12):1805-1816
No equipment (system) can be perfectly reliable in spite of the utmost care and best efforts on the part of the designer, decision-maker and manufacturer. The two sides of maintenance are corrective and preventive maintenance. It is generally assumed that a preventive maintenance action is less costly than a repair maintenance action. We examine this proposition in detail on the basis of a failure-time model that relates conformance quality to reliability. Illustratively, we present reliability in the context of contracts with asymmetric information. The model shows how to overcome information rents through price distortions and quantity rationing. The paper ends with a conclusion and an outlook to future studies. 相似文献
115.
Sicard S Bérubé JF Samar D Messaoudi A Fortin D Lebrun F Fortin JF Decken A Harvey PD 《Inorganic chemistry》2004,43(17):5321-5334
The 1:1 reaction between the d(9)-d(9) Pd(2)(dmb)(2)Cl(2) complex (dmb = 1,8-diisocyano-p-menthane) and the diphosphine ligands (diphos) bis(diphenylphosphino)butane (5, dppb), bis(diphenylphosphino)pentane (6, dpppen), bis(diphenylphosphino)hexane (7, dpph), and bis(diphenylphosphino)acetylene (8, dpa) in the presence of LiClO(4) leads to the [[Pd(2)(dmb)(2)(diphos)](ClO(4))(2)](n) polymers. These new materials are characterized by NMR ((1)H, (13)C, (31)P), IR, Raman, and UV-vis spectroscopies (466 < lambda(max)(dsigma-dsigma*) < 480 nm), by ATG, XRD, and DSC methods, and by the capacity to make stand-alone films. From the measurements of the intrinsic viscosity in acetonitrile, the M(n) ranges from 16000 to 18400 (12 to 16 units). The dinuclear model complex [Pd(2)(dmb)(2)(PPh(3))(2)](ClO(4))(2) (4) is prepared and investigated as well. The molecular dynamic of the title polymers in acetonitrile solution is investigated by means of (13)C spin-lattice relaxation time (T(1)) and nuclear Overhauser enhancement methods (NOE). The number of units determined by T(1)/NOE methods is 3 to 4 times less than that found from the measurements of intrinsic viscosity, and is due to flexibility in the polymer backbone, even for bridging ligands containing only one (dmb) or two C-C single bonds (dpa). During the course of this study, the starting material Pd(2)(dmb)(2)Cl(2) was reinvestigated after evidence for oligomers in the MALDI-TOF spectrum was noticed. In solution, this d(9)-d(9) species is a binuclear complex (T(1)/NOE). This result suggests that the structure of the title polymers in solution and in the solid state may not be the same either. Finally, these polymers are strongly luminescent in PrCN glasses at 77 K, and the photophysical data (emission lifetimes, 1.50 < tau(e) < 2.75 ns; quantum yields, 0.026 < Phi(e) < 0.17) are presented. X-ray data for [Pd(2)(dppe)(2)(dmb)(2)](PF(6))(4): monoclinic, space group C2/c, a = 24.3735 A, b = 21.8576(13) A, c = 18.0034(9) A, b = 119.775(1) degrees, V = 8325.0(8) A(3), Z = 4. 相似文献
116.
Ishaque Khan M Ayesh S Doedens RJ Yu M O'Connor CJ 《Chemical communications (Cambridge, England)》2005,(37):4658-4660
A new type of mixed-valence polyoxoanionic cluster, [V(V)13V(IV)3O42(Cl)]8-, composed of 14 {VO5} square pyramids and 2 {VO4} tetrahedral units, hosting a chloride ion has been synthesized and characterized. 相似文献
117.
The synthesis, structural characterization, and properties of a new series of asymmetrically substituted bis(dithiolene) nickel(III) compounds [Bu4N][Ni(Phdt)2] (1) (Phdt = 2-Phenyl-1,2-dithiolate), [Bu4N][Ni(NO2Phdt)2] (2) (NO2Phdt = 2-( p-nitrophenyl)-1,2-dithiolate), [Bu4N][Ni(FPhdt)2] (3) (FPhdt = 2-( p-fluorophenyl)-1,2-dithiolate), [Bu4N][Ni(ClPhdt)2] (4) (ClPhdt = 2-( p-chlorophenyl)-1,2-dithiolate), and [Bu4N][Ni(BrPhdt)2] (5) (BrPhdt = 2-( p-bromophenyl)-1,2-dithiolate) have been described. All complexes 1- 5 exhibit absorptions in the near-infrared region; the shift of these absorption bands can be tuned by the choice of the substituents on the relevant dithiolene moieties. The substituents on the dithiolene moiety are also responsible for their structural diversities. The nature of the substituents on the dithiolene moiety play an important role in tuning the redox potentials along this series. The nitro derivative (compound 2) exhibits several redox couples in its cyclic voltammogram in contrast to the other compounds in this series. The synthesis and characterization of two asymmetrically halogen substituted tetrathiafulvalene (TTF) derivatives 4,4'-bis(4-chlorophenyl)-tetrathiafulvalene ClPhTTF (6) and 4,4'-bis(4-bromophenyl)-tetrathiafulvalene (BrPhTTF) (7) have been described. One of these compounds has been structurally characterized. Iodine treatment of the monoanionic Ni(III) compound [Bu4N][Ni(ClPhdt)2] (4) results in the formation of a neutral Ni(IV) complex [Ni(ClPhdt)2] (8). All monoanionic compounds 1- 5 are Ni(III) complexes, as evidenced by electron spin resonance spectroscopy. Interestingly, strong Cl...Cl interactions are observed in the solid state structures of the chlorinated compounds 6 and 8. Finally, the structural features of compound [Ni(ClPhdt)2] (8) and the TTF derivative ClPhTTF (6) are compared based on their enormous structural similarities, and the neutral compound [Ni(ClPhdt)2] (8) is classed as the "an inorganic counterpart of TTF". 相似文献
118.
Samar Beaini Glen B. Deacon Craig M. Forsyth Peter C. Junk Prof. 《无机化学与普通化学杂志》2008,634(15):2903-2906
The complex [Yb(Ph2pz)3(LiOBu)]2 ( 1 ) (Ph2pz = 3,5‐diphenylpyrazolate), fortuitously obtained from reaction of Yb metal with a lithium containing sample of [SnMe3(Ph2pz)] at elevated temperatures forms a centrosymmetric butoxy‐ and pyrazolate‐bridged open box structure. Each ytterbium atom is eight coordinate with one chelating Ph2pz ligand, one μ‐η2:η2 bridging pyrazolate, one μ‐η2(Yb):η4(Li) Ph2pz group and two bridging butoxide ligands. Each lithium atom is unsymmetrically chelated by an η2‐Ph2pz group, η4(N,C(pz)C2(Ph)) bonded by another pyazolate group, and bridged through a butoxide oxygen atom to two ytterbium atoms. The type of η4‐pyrazolate coordination is unprecedented and is the first observation of interactions to a metal by the Ph rings of the Ph2pz ligand. The complex [Li(dme)3][Eu(Ph2pz)3(dme)] ( 2 ) obtained from reaction of Eu metal with the same sample of [SnMe3(Ph2pz)] in dme at room temperature is a charged separated species with the first anionic pyrazolatolanthanoidate(II) complex in which europium is eight coordinate with three chelating Ph2pz ligands and a chelating dme. 相似文献
119.
Suzana Samaržija-Jovanović Vojislav Jovanović Sandra Konstantinović Gordana Marković Milena Marinović-Cincović 《Journal of Thermal Analysis and Calorimetry》2011,104(3):1159-1166
The thermal stability of pure urea–formaldehyde resin (PR) and modified urea–formaldehyde (UF) resins with hexamethylenetetramine-HMTA
(Resin 1), melamine-M (Resin 2), and ethylene urea (EU, Resin 3) including nano-SiO2 was investigated by non-isothermal thermo-gravimetric analysis (TG), differential thermal gravimetry (DTG), and differential
thermal analysis (DTA) supported by data from IR spectroscopy. Possibility of combining inorganic filler in a form of silicon
dioxide with UF resins was found investigated and percentage of free formaldehyde was determined. The shift of DTG peaks to
a high temperature indicates the increase of thermal stability of modified UF resin with EU (Resin 3) which is confirmed by
data obtained from the FTIR study. The minimum percentage (6%) of free formaldehyde was obtained in Resin 3. 相似文献
120.
A Mononuclear CoII Coordination Complex Locked in a Confined Space and Acting as an Electrochemical Water‐Oxidation Catalyst: A “Ship‐in‐a‐Bottle” Approach 下载免费PDF全文
Paulami Manna Dr. Joyashish Debgupta Dr. Suranjana Bose Prof. Samar K. Das 《Angewandte Chemie (International ed. in English)》2016,55(7):2425-2430
Preparing efficient and robust water oxidation catalyst (WOC) with inexpensive materials remains a crucial challenge in artificial photosynthesis and for renewable energy. Existing heterogeneous WOCs are mostly metal oxides/hydroxides immobilized on solid supports. Herein we report a newly synthesized and structurally characterized metal–organic hybrid compound [{Co3(μ3‐OH)(BTB)2(dpe)2} {Co(H2O)4(DMF)2}0.5]n?n H2O ( Co‐WOC‐1 ) as an effective and stable water‐oxidation electrocatalyst in an alkaline medium. In the crystal structure of Co‐WOC‐1 , a mononuclear CoII complex {Co(H2O)4(DMF)2}2+ is encapsulated in the void space of a 3D framework structure and this translationally rigid complex cation is responsible for a remarkable electrocatalytic WO activity, with a catalytic turnover frequency (TOF) of 0.05 s?1 at an overpotential of 390 mV (vs. NHE) in 0.1 m KOH along with prolonged stability. This host–guest system can be described as a “ship‐in‐a‐bottle”, and is a new class of heterogeneous WOC. 相似文献