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71.
The methyl esters of the cytochrome P-450 epoxygenase metabolites 11(S),12(R)-and 14(R),15(S)-epoxyeicosatrienoic acid and some analogues were prepared enantiospecifically from 15(S)-HETE derived precursors. 相似文献
72.
Basuli F Bailey BC Tomaszewski J Huffman JC Mindiola DJ 《Journal of the American Chemical Society》2003,125(20):6052-6053
One-electron oxidation of the beta-diketiminate titanium(III) bis-neopentyl complex (Nacnac)Ti(CH2tBu)2 (Nacnac = [Ar]NC(Me)CHC(Me)N[Ar], Ar = 2,6-(CHMe2)2C6H3) promotes alpha-abstraction to afford the rare and terminal four-coordinate neopentylidene (Nacnac)Ti=CHtBu(OTf), which was structurally characterized. Alkylidene (Nacnac)Ti=CHtBu(OTf) reacts cleanly with benzophenone and the imine functionality of the Nacnac ligand to afford the corresponding Wittig-type products. 相似文献
73.
N. Sukumar 《International journal of quantum chemistry》1994,52(4):809-816
The first discussion of the dynamics of Jahn–Teller systems in terms of the electronic density as the fundamental variable was given by W.J. Clinton in 1960, where the degenerate electronic configuration of a Jahn–Teller molecule was interpreted in terms of the infinite number of ways in which the charge distribution can be oriented for the same energy. The moving nuclear framework serves as the perturbation necessary to define the orientation of the charge density, with no activation energy required to put the charge cloud into motion. Recently, this notion of the electronic charge cloud in a Jahn–Teller molecule sweeping out the potential surface over which the nuclei move has found mathematical expression in our work in terms of a generalized electronic current density in nuclear-coordinate space [N. Sukumar and B.M. Deb, Int. J. Quantum Chem. 40 , 501 (1991)]. The introduction of the electronic phase as a function of both electronic and nuclear coordinates, in addition to the electronic density, is a crucial component of this formulation. In the present work, the density-based treatment is extended to the nonadiabatic situation, with the Born couplings interpreted as nonadiabatic currents in parameter space. Abelian and non-Abelian gauge transformations of these currents are discussed. © John Wiley & Sons, Inc. 相似文献
74.
S. S. Rayalu A. K. Bansiwal S. U. Meshram Nitin Labhsetwar Sukumar Devotta 《Catalysis Surveys from Asia》2006,10(2):74-88
Fly ash is combustion residue from burning of pulverised coal in electric utility generating stations. The annual production of fly ash in India is around 100 MTPA and is responsible for several environmental hazards, which is quite well documented. There are stringent norms for its land disposal and hence utilisation of fly ash is imperative. Fly ash has more than 85% of SiO2 and Al2O3 content and is therefore a tailor made raw material for production of zeolite. An innovative process has been developed for synthesis of zeolites using fly ash as a substitute for conventional raw materials viz. sodium silicate and aluminate. The process consists of three major steps viz. fusion of caustic soda and fly ash for optimal extraction of silicate and aluminate, aging step which provides time for formation of nuclei and hydrothermal crystallization resulting in activation of nuclei into well defined crystals. Low temperature operation, simplicity of process and optimal recycling of unused reactants and process water are special features of these processes. Zeolites have high internal and external surface areas and also exhibit high exchange capacities, which makes them versatile materials for targeting wide range of pollutants, ranging from cationic to anionic and hydrophilic to hydrophobic molecules. The major uses of zeolites are in adsorption, ion exchange and as catalysts. The use of zeolites in environmental remediation is restricted due to procurement problem and prohibitive cost, which can be overcome by using low cost fly ash based zeolites (FAZs). The synthesis of FAZ-A and FAZ-Y and their modifications either by transition metal incorporation or by surfactant treatment for various environmental applications in air, water and soil remediation are addressed in this review. 相似文献
75.
Sabyasachi Sinha Ray Achintya K. Kundu Malay Ghosh Sukumar Maiti 《Journal of polymer science. Part A, Polymer chemistry》1986,24(4):603-612
A comparative evaluation of triphenylphosphine–polyhalocompound-activated polycondensation of amino carboxylic acid as well as amino carboxylic acid containing an imidogroup with thionyl chloride activated polycondensation of the above two types of acids has been discussed. The role of different polyhalocompounds, acid acceptors, sequence of addition of reactants, temperature of reaction, etc. has been studied. It was observed that the molecular weight of the polyamide and polyamideimide, as evident from their inherent viscosity data, is generally higher, but the yield is lower than those obtained by thionyl chloride method. The reaction by the former method appears to be faster than the latter. The influence of various reaction conditions and possible mechanism of the polycondensation have been discussed. 相似文献
76.
The reaction of ketene OCCPh(2) with the four-coordinate titanium(IV) imide (L(1))Ti[double bond]NAr(OTf) (L(1)(-) = [Ar]NC(CH(3))CHC(CH(3))N[Ar], Ar = 2,6-[CH(CH(3))(2)](2)C(6)H(3)) affords the tripodal dimine-alkoxo complex (L(2))Ti[double bond]NAr(OTf) (L(2)(-) = [Ar]NC(CH(3))CHC(O)[double bond]CPh(2)C(CH(3))N[Ar]). Complex (L(2))Ti[double bond]NAr(OTf) forms from electrophilic attack of the beta-carbon of the ketene on the gamma-carbon of the Nacnac(-) NCC(gamma)CN ring. On the contrary, nucleophiles such as LiR (R(-) = Me, CH(2)(t)Bu, and CH(2)SiMe(3)) deprotonate cleanly in OEt(2) the methyl group of the beta-carbon on the former Nacnac(-) backbone to yield the etherate complex (L(3))Ti[double bond]NAr(OEt(2)), a complex that is now supported by a chelate bis-anilido ligand (L(3)(2)(-) = [Ar]NC(CH(3))CHC(CH(2))N[Ar]). In the absence of electrophiles or nucleophiles, the robust (L(1))Ti[double bond]NAr(OTf) template was found to form simple adducts with Lewis bases such as CN(t)Bu or NCCH(2)(2,4,6-Me(3)C(6)H(2)). Complexes (L(2))Ti[double bond]NAr(OTf), (L(3))Ti[double bond]NAr(OEt(2)), and the adducts (L(1))Ti[double bond]NAr(OTf)(XY) [XY = CN(t)Bu and NCCH(2)(2,4,6-Me(3)C(6)H(2))] were structurally characterized by single-crystal X-ray diffraction studies. 相似文献
77.
An intramolecular Passerini reaction between 3,4-methylenedioxyphenethylisocyanide and opianic acid is applied in a total synthesis of hydrastine, a phthalideisoquinoline alkaloid. 相似文献
78.
Mandal Suman Kumar Saha Pinaki Munshi Parthapratim Sukumar N. 《Structural chemistry》2017,28(5):1537-1552
Structural Chemistry - Two different scoring functions, Hirshfeld fingerprint-based scoring (HFBS) and molecular operating environment (MOE), and the kernel energy method (KEM) along with... 相似文献
79.
80.
Fatkhulla K. Tadjimukhamedov John A. Stone Dimitris Papanastasiou Jaime E. Rodriguez Wolfgang Mueller Harikrishnan Sukumar Gary A. Eiceman 《International Journal for Ion Mobility Spectrometry》2008,11(1-4):51-60
Chlorophenols (CPs) as a mixture of fourteen congeners from mono- to pentachlorophenol were determined using liquid chromatography/electrospray ionization/ion mobility spectrometry (LC/ESI/IMS) to describe the response and analytical performance of a mobility spectrometer as a detector for liquid chromatography. The mobility spectrometer was equipped with an interface so that flows from a large bore column could be electrosprayed directly into the drift tube at flow rates up to 500 μL/min without splitting of flow. A linear gradient of the mobile phase from 40% to 90% methanol and 60% to 10% acetic acid (AcOH)–ammonium acetate buffer solution over 40 min with a C18 column provided baseline separations though mobility spectra for CPs were influenced by mobile phase composition. Product ions formed from CPs with ESI included phenoxide anions CPO?, AcOH·CPO?, CPOH·CPO?, and Na+·(CPO?)2 and were found to be governed by the drift gas temperature. Ions were identified using LC/ESI/mass spectrometry (MS) and supported by results from computational modeling. Quantitative response was affected by congener structure through the acidities of the OH moiety and by the composition of the mobile phase. Limits of detection ranged from 0.135 mg/L for 2,3,5-trichlorophenol and pentachlorophenol to 2.23 mg/L for 2-chlorophenol; corresponding linear ranges were 20 and 70. 相似文献