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排序方式: 共有101条查询结果,搜索用时 46 毫秒
81.
Dr. Ludovic Castro Dr. Yat-Ming So Chang-woo Cho Prof. Dr. Rolf Lortz Kai-Hong Wong Dr. Kai Wang Prof. Dr. Polly L. Arnold Dr. Ka-Chun Au-Yeung Dr. Herman H.-Y. Sung Prof. Dr. Ian D. Williams Prof. Dr. Wa-Hung Leung Prof. Dr. Laurent Maron 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10834-10839
A combined experimental and theoretical investigation on the cerium(IV) oxo complex [(LOEt)2Ce(=O)(H2O)] ⋅ MeC(O)NH2 ( 1 ; LOEt−=[Co(η5-C5H5){P(O)(OEt)2}3]−) demonstrates that the intermediate spin-state nature of the ground state of the cerium complex is responsible for the versatility of its reactivity towards small molecules such as CO, CO2, SO2, and NO. CASSCF calculations together with magnetic susceptibility measurements indicate that the ground state of the cerium complex is of multiconfigurational character and comprised of 74 % of CeIV and 26 % of CeIII. The latter is found to be responsible for its reductive addition behavior towards CO, SO2, and NO. This is the first report to date on the influence of the multiconfigurational ground state on the reactivity of a metal–oxo complex. 相似文献
82.
Katarina Topalov P. David Polly Peter E. Sauer Suresh Viswanathan 《Isotopes in environmental and health studies》2019,55(2):129-149
2H/1H ratios in animal biomass reflect isotopic input from food and water. A 10-week controlled laboratory study raised 48 mice divided in two generations (8 mothers Mus musculus and their offspring). The mice were divided into four groups based on the combination of 2H, 13C, 15N-enriched and non-enriched food and water. Glycine, the most common amino acid in bone collagen, carried the 2H, 13C, 15N-isotopic spike in food. ANOVA data analysis indicated that hydrogen in food accounted for ~81?% of the hydrogen isotope inventory in collagen whereas drinking water hydrogen contributed ~17?%. Air humidity contributed an unspecified amount. Additionally, we monitored 13C and 15N-enrichment in bone collagen and found strong linear correlations with the 2H-enrichment. The experiments with food and water indicate two biosynthetic pathways, namely (i) de novo creation of non-essential amino acids using hydrogen from water, and (ii) the integration of essential and non-essential amino acids from food. The lower rate of isotope uptake in mothers’ collagen relative to their offspring indicates incomplete bone collagen turnover after ten weeks. The variance of hydrogen stable isotope ratios within the same cohort may limit its usefulness as a single sample proxy for archaeological or palaeoenvironmental research. 相似文献
83.
Polly L. Arnold Prof. Dr. Jean‐Charles Buffet Robert Blaudeck Slawomir Sujecki Dr. Claire Wilson Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(33):8241-8250
The reaction of a chiral racemic bidentate ligand HL1 (tBu2P(O)CH2CH(tBu)OH) with mid to late trivalent lanthanide cations affords predominantly homochiral lanthanide complexes (RRR)‐[Ln(L1)3] and (SSS)‐[Ln(L1)3]. A series of reactions are reported that demonstrate that the syntheses are under thermodynamic control, and driven by a ligand ‘self‐recognition’ process, in which the large asymmetric bidentate L1 ligands pack most favourably in a C3 geometry around the lanthanide cation. The synthesis of bis(L1) adducts [Ln(L1)2X] (X=N(SiMe3)2, OC6H3tBu‐2,6) is also reported. Analysis of the diastereomer mixtures shows that homochiral (L1)2 complexes are favoured but to a lesser extent. The complexes Ln(L1)3 and [Ln(L1)2(OC6H3tBu‐2,6)] have been studied as initiators for the polymerization of ε‐caprolactone and its copolymer with lactide, glycolide and its copolymer with lactide, and ε‐caprolactam. 相似文献
84.
85.
Polly L. Arnold Micha S. Dutkiewicz Markus Zegke Olaf Walter Christos Apostolidis Emmalina Hollis Anne‐Frderique Pcharman Nicola Magnani Jean‐Christophe Griveau Eric Colineau Roberto Caciuffo Xiaobin Zhang Georg Schreckenbach Jason B. Love 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(41):12989-12993
A dramatic difference in the ability of the reducing AnIII center in AnCp3 (An=U, Np, Pu; Cp=C5H5) to oxo‐bind and reduce the uranyl(VI) dication in the complex [(UO2)(THF)(H2L)] (L=“Pacman” Schiff‐base polypyrrolic macrocycle), is found and explained. These are the first selective functionalizations of the uranyl oxo by another actinide cation. At‐first contradictory electronic structural data are explained by combining theory and experiment. Complete one‐electron transfer from Cp3U forms the UIV‐uranyl(V) compound that behaves as a UV‐localized single molecule magnet below 4 K. The extent of reduction by the Cp3Np group upon oxo‐coordination is much less, with a NpIII‐uranyl(VI) dative bond assigned. Solution NMR and NIR spectroscopy suggest NpIVUV but single‐crystal X‐ray diffraction and SQUID magnetometry suggest a NpIII‐UVI assignment. DFT‐calculated Hirshfeld charge and spin density analyses suggest half an electron has transferred, and these explain the strongly shifted NMR spectra by spin density contributions at the hydrogen nuclei. The PuIII–UVI interaction is too weak to be observed in THF solvent, in agreement with calculated predictions. 相似文献
86.
Raymond J. Haines Michael Laing Elsie Meintjies Polly Sommerville 《Journal of organometallic chemistry》1981,215(1):C17-C19
[{Rh(CO)(MeO)2PNEtP(OMe)2Cl)}2], synthesised by reaction of [{Rh(CO)2Cl)}2] with (MeO)2PNEtP(OMe)2, has an unusual asymmetric structure in which one carbonyl group adopts a terminal position while the other is bridging; the two chlorines are both terminal. 相似文献
87.
An analytical system was developed for detection of antibiotic residues in bovine milk. The method is based on competitive fluorescent immunoassays in glass capillary tubes (U.S. Patent No. 5,624,850). The system consists of an assay cartridge containing 4 glass capillaries, a reagent tray with 4 wells of dried reagents, and a Parallux processor, which processes the assay, reads fluorescent output, and reports test results. Minimum sensitivity for detection of 6 beta-lactam antibiotics in bovine milk was determined to be penicillin-G, 3.2 ppb; ampicillin, 2.9 ppb; amoxicillin, 3.6 ppb; cloxacillin, 7.4 ppb; cephapirin, 16.3 ppb; and ceftiofur, 33.7 ppb. The assay system was also specific and sensitive for detection of incurred residues at U.S. Food and Drug Administration tolerance levels: penicillin-G, 5 ppb; ampicillin, 10 ppb; amoxicillin, 10 ppb; cloxacillin, 10 ppb; cephapirin, 20 ppb; and ceftiofur, 50 ppb. There was no interference in detection of minimum sensitivity levels of antibiotic by the presence of somatic cells at approximately 1 x 10(6) cells/mL. Milk containing 3 x 10(6) cells/mL bacteria commonly found in mastitic milk also showed no interference when tolerance levels of antibiotic were present. There was no detectable interference on results by a wide variety of non-beta-lactam drugs. 相似文献
88.
Arnold PL Rodden M Davis KM Scarisbrick AC Blake AJ Wilson C 《Chemical communications (Cambridge, England)》2004,(14):1612-1613
A one-pot synthesis of a wide range of bidentate, alkoxide-N-heterocyclic carbene ligands provides new lithium alkoxy-carbenes and a range of covalently bound organometallic Cu(II) carbene complexes, which are catalytically active, in some cases enantioselectively, for conjugate addition reactions. 相似文献
89.
Natrajan LS Blake AJ Wilson C Weinstein JA Arnold PL 《Dalton transactions (Cambridge, England : 2003)》2004,(21):3748-3755
A series of trivalent mono- and tris(ligand) lanthanide complexes of a sulfur-bridged binaphthol ligand [1,1'-S(2-HOC(10)H(4)Bu(t)(2)-3,6)(2)] H(2)L(SN), have been prepared and characterised both structurally and photophysically. The H(2)L(SN) ligand provides an increased steric bulk and offers an additional donor atom (sulfur) as compared with 1,1'-binaphthol (BINOL), a ligand commonly used to complex Lewis acidic lanthanide catalysts. Reaction of the diol H(2)L(SN) with [Sm[N(SiMe(3))(2)](3)] affords silylamido- and amino- derivatives [Sm(L(SN))[N(SiMe(3))(2)][HN(SiMe(3))(2)]] and the crystallographically characterised [Sm(L(SN))[N(SiMe(3))(2)](thf)(2)] with different degrees of structural rigidity, depending on the presence of coordinating solvents. The binaphthyl groups of the L(SN) ligand act as sensitisers of the metal centred emission, which is observed for the Eu(III) and Sm(III) complexes studied. We have therefore sought to use emission spectroscopy as a non-invasive technique to monitor a monomer-dimer equilibrium in these complexes. A dramatic difference between the emission properties of the unreactive dimeric Sm(III) aryloxide complex, the solvated monomeric analogues and the amido adduct demonstrated the potential use of such a technique. For a few representative lanthanides (Ln = Sm, Eu and Y) the reaction of the dilithium salt Li(2)L(SN) with either [Ln[N(SiMe(3))(2]3)] or [LnCl(3)(thf)(3)] affords only the homoleptic complex [Li(S)(3)][LnL(SN)(3)](S = thf or diethyl ether); we report the structural characterisation of the Sm complex. However, the reactions of this dipotassium salt K(2)L(SN) with [Sm[N(SiMe(3))(2)](3)] or [SmCl(3)(thf)(3)] give only [SmL(SN)N(SiMe(3))(2)], or intractable mixtures respectively, in which no (tris)binaphtholate is observed. The only isolable lanthanide-L(SN) halide adduct so far is [YbL(SN)I(thf)]. 相似文献
90.
Nicholas Lowther Polly Crook Dennis Hall 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):405-408
Abstract Kinetic data on the formation, hydrolysis and thermolysis of acyclic phosphoranes is reported and the mechanism of each reaction is discussed. 相似文献