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11.
《Analytical letters》2012,45(10):769-776
Abstract A method is reported for the determination of Ni, Co, Bi, Al, V, Ti, Cu, Si, Pb, Cr, Mg, Sn, and Fe in molybdenum metal by optical emission spectrography. The procedure consists of dissolving the metal in HNO3 and HCl, evaporating to dryness, and igniting at 500–550°C to MoO3. The MoO3 is mixed with an equal weight of GeO2, which acts as an inert collector, and ignited at 700–750°C to volatilize the MoO3. This double ignition method concentrates the impurities on the GeO2 thereby placing the trace elements within the range of the spectrograph. The residue is excited in a d c are at 10 amps and the spectra are recorded on a photographic emulsion. 相似文献
12.
Sandra Chouzier Tivadar Czeri Magalie Roy-Auberger Christophe Pichon Christophe Geantet Michel Vrinat Pavel Afanasiev 《Journal of solid state chemistry》2011,184(10):2668-2677
Decomposition of ammonium heptamolybdate–hexamethylentetramine (HMTA) complex (HMTA)2(NH4)4Mo7O24·2H2O was studied as a function of treatment conditions in the range 300–1173 K. The evolution of solid products during decomposition was studied by thermal analysis and in situ EXAFS. Depending on the nature of the gas used for treatment, single phases of highly dispersed nitrides Mo2N, carbide Mo2C, or oxide MoO2 can be obtained. The nature of the products obtained was explained by qualitative thermodynamical considerations. Morphology of the solids considerably depends on such preparation parameters as temperature and mass velocity of the gas flow. For the nitride-based materials, catalytic activity was evaluated in the model thiophene HDS reaction. It was demonstrated that NH3-treated samples showed better catalytic activity than N2-treated ones due to cleaner surface and better morphology. Transmission microscopy, XRD and XPS studies showed that MoS2 is formed on the surface during HDS reaction or sulfidation with H2S. Optimized nitride-derived catalysts showed mass activity several times higher than unsupported MoS2 or MoS2/Al2O3 reference catalyst. 相似文献
13.
The reaction of the thiocarbamoyl‐molybdenum complex [Mo(CO)2(η2‐SCNMe2)(PPh3)2Cl] 1 , with EtOCS2K and C4H8NCS2NH4 in dichloromethane at room temperature yielded the seven coordinated ethyldithiocarbonate thiocarbamoyl‐molybdenum complex [Mo(CO)2(η2‐S2COEt)(η2‐SCNMe2)(PPh3)] 2 , and the dithiocarbamate thiocarbamoyl‐molybdenum complex [Mo(CO)2(η2‐S2CNC4H8)(η2‐SCNMe2)(PPh3)] 3 . The geometry around the metal atom of compounds 2 and 3 are capped octahedrons as revealed by X‐ray diffraction analyses. The thiocarbamoyl and ethyldithiocarbonate or pyrrolidinyldithiocarbamate ligands coordinate to the molybdenum metal center through the carbon and sulfur and two sulfur atoms, respectively. Structure parameters, NMR, IR and Mass spectra are in agreement with the crystal chemistry of the two compounds. 相似文献
14.
Attempts to synthesize complexes of group 6 carbonyl compounds [M(CO)6] (M = Cr, Mo, W) with the carbone C(PPh3)2 ( 1 ) via the photo chemically created adducts [(CO)5M(THF)] lead to quantitative formation of the salts [HC(PPh3)2]2[M2(CO)10] ( 2 , Cr; 3 , Mo; 4 , W). Alternatively, a long-time thermal reaction of [Mo(CO)6] performed with 1 in THF generates a series of products initiated by a Wittig-type reaction. In addition to 3 , minor amounts of [(CO)5MoCCPPh3] ( 8 ), [(CO)5MoO2CC{PPh3}2] ( 5 ), and the carbonate complexes [HC(PPh3)2]2[(CO)5Mo(CO3)Mo(CO)4] ( 6 ) and [HC(PPh3)2]2[(CO)4Mo(CO3)Mo(CO)4] ( 7 ) were found. Compounds 2 , 3 , 5 , 6 , and 7 were characterized by X-ray analyses, 31P NMR, and IR spectroscopy. The water, necessary for the formation of the carbonate, stems from decomposition of THF. 相似文献
15.
16.
Wenjuan Yan Mengyuan Liu Jinyao Wang Jian Shen Shuxia Zhang Xiaoqiang Xu Shuaishuai Wang Jie Ding Xin Jin 《Chemical record (New York, N.Y.)》2020,20(3):230-251
Molybdenum complexes are versatile and efficient for liquid phase olefin epoxidation reactions. Rational design of catalysts is critical to achieve high atom efficiency during epoxidation processes. Although liquid phase epoxidation has been a popular topic for decades, three key issues, (a) rational control of morphology of molybdenum nanoparticles, (b) manipulating metal‐support interaction and (c) altering electronic configuration at molybdenum center remains unsolved in this area. Therefore, in this paper, we have critically revised recent research progress on heterogeneous molybdenum catalysts for facile liquid phase olefin epoxidation in terms of catalyst synthesis, surface characterization, catalytic performance and structure‐function relationship. Furthermore, plausible reaction mechanisms will be systematically discussed with the aim to provide insights into fundamental understanding on novel epoxidation chemistry. 相似文献
17.
Imran Murtaza Ibrahim Qazi Khasan S. Karimov Muhammad H. Sayyad 《Physica B: Condensed Matter》2011,406(3):533-536
We use experimental results of direct current and low signal impedance spectroscopy to investigate the conduction mechanism in organic semiconductor ZnPc. The experimental results demonstrate an increase in current and holes mobility by the introduction of a thin MoO3 film at the ITO/ZnPc interface. This significantly improves the device performance. The improvement is explained in terms of the reduction in the effective barrier for charge transfer from ZnPc to ITO. 相似文献
18.
The quadruply bonded Mo24+ complex Mo2(DAniF)3(OOCC6F5) ( 1 ) [DAniF = N,N′‐bis(4‐methoxyphenyl)formamidinate] was synthesized. The solvate Mo2(DAniF)3(OOCC6F5) · (C6H6) ( 2 ) and co‐crystal Mo2(DAniF)3(OOCC6F5) · (C10H8) ( 3 ) complexes were obtained by self‐assembly of crystals of 1 with benzene and naphthalin, respectively. Compounds 1 , 2 , and 3 were structurally characterized by single‐crystal X‐ray diffraction. In monomer 1 , the Mo–Mo bond length of 2.0874(6) Å is typical for dimolybdenum quadruple bonds. The solvate complex 2 was stabilized by weak π–π stacking interactions between the benzene molecule and the pentafluorophenyl ring (as indicated by a center‐to‐center distance of 3.838(10) Å and a center‐to‐plane distance of 3.712(4) Å between phenyl and pentafluorophenyl ring) and intermolecular C–H ··· F–C interactions (the shortest F ··· H distance is 2.560(2) Å). In complex 3 , a one‐dimensional chain was formed by C–H ··· F–C interactions between the hydrogen atoms in naphthalin and the fluorine atoms in the monomer (H ··· F distances of 2.582(2) Å). Information on the structures in solution of the three crystals was obtained by 1H NMR spectroscopy. 相似文献
19.
The haptotropic migration of Cr(CO)3, Mo(CO)3 and W(CO)3 moieties on a substituted phenanthrene has been studied theoretically using gradient-corrected density functional theory. The stationary points (minima and transition states) on the energy hypersurface characterizing the migrating process of the metal fragment over the aromatic system have been located. Furthermore, the energetic and structural differences between complexes of the three metals Cr, Mo and W and the effect of a high substitution of one arene ring on the reaction energy profile have been analyzed. The possibility to design a molecular switch based on the substituent pair R = O−/OH is investigated. It is concluded that the Mo and W complexes undergo a haptotropic migration more easily than the corresponding Cr system. 相似文献
20.
Acetato-bis(pyrazole) complexes [Mo(η3-methallyl)(O2CMe)(CO)2(pz∗H)2], (methallyl = CH2C(CH3)CH2) and fac-[M(O2CMe)(CO)3(pz∗H)2], (pz∗H = pyrazole or 3,5-dimethylpyrazole, dmpzH; M = Mn, Re) are obtained from [Mo(η3-methallyl)Cl(CO)2(NCMe)2] or fac-[MBr(CO)3(NCMe)2] [M = Mn (synthesized in situ), Re], 2 equiv. of pyrazole, and 1 equiv. of sodium acetate for Mo complexes, or silver acetate for Mn or Re complexes. The chlorido-complexes [Mo(η3-methallyl)Cl(CO)2L2] (L = pzH, dmpzH), obtained from the same starting material by substitution of MeCN by pzH or dmpzH, are also described. The crystal structures of the fac-acetato-bis(dimethylpyrazole) complexes present the same pattern of intramolecular hydrogen bonds between the acetate and the dimetylpyrazole ligands, whereas the crystal structures of the fac-acetato-bis(pyrazole) complexes show different hydrogen bonds patterns, with intermolecular interactions. NMR data indicate that these interactions are not maintained in solution. 相似文献