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341.
By using a megacycle-frequency oscillator to follow the reaction, the Lewis acid, stannic chloride, can be titrated with nitrogen bases in acetonitrile as solvent and with oxygen bases in benzene as solvent with an error of 0.5–4%; reverse-order titrations were equally successful. The characteristic maxima and minima in the titration curves indicate that in acetonitrile stannic chloride probably forms AB, A3B4 and A4B3 adducts with piperidine, and AB and A4B3 adducts with pyridine; no adduct was indicated for diphenylamine. In benzene solution, stannic chloride forms (a) AB2 adducts with MeOH, EtOH, n-PrOH, iso-PrOH, n-BuOH, sec.-BuOH and iso-BuOH, (b) AB and AB2 adducts with acetone and tetrahydrofuran, and (c) an AB adduct with dioxane; the stoichiometry for a group of ethers is less decisive. The presence of the 1:1 tetrahydrofuran-stannic chloride adduct in benzene supports the belief that pentacoordinate tin exists in certain adducts with oxygen bases. The megacycle-frequency oscillator was also applied to the estimation of the relative base strength of Lewis bases toward a given Lewis acid by assuming that the instrument response increase, as an ether or alcohol was added to stannic chloride in benzene, is due to the formation of the new coordinate bond. Agreement of the data obtained with the limited existing data on relative base strengths of ethers is good in those cases where comparable steric factors are involved. 相似文献
342.
The U(III) mixed-sandwich compound [U(eta-Cp)(eta-C(8)H(4)[Si(i)Pr(3)-1,4](2))] 1 may be prepared by sequential reaction of UI(3) with KCp followed by K(2)[C(8)H(4)[Si(i)Pr(3)-1,4](2)], and has been crystallographically characterized. 1 reacts reversibly with dinitrogen to afford dimeric [[U(eta-Cp)(eta-C(8)H(4)[Si(i)Pr(3)-1,4](2))](2)(mu-eta(2):eta(2)-N(2))] 2, whose X-ray crystal structure reveals a sideways-bound, bridging diazenido (N(2)(2-)) ligand. 相似文献
343.
Antolini F Gehrhus B Hitchcock PB Lappert MF Slootweg JC 《Dalton transactions (Cambridge, England : 2003)》2004,(20):3288-3294
The thermally stable silylene Si[(NCH(2)Bu(t))(2)C(6)H(4)-1,2] 1 undergoes oxidative addition reactions with the alkali metal silylamides MN(SiMe(3))(2)(M = Li, Na or K) to afford the new alkali metal amides MN(SiMe(3))[(1)SiMe(3)][M = Li (2), Na (3) or K (4)]. Reaction of two equivalents of 1 with LiN(R)(SiMe(3)) leads in a two-step process to the compound LiN[(1)R][(1)SiMe(3)][R = SiMe(2)Ph (5) or SiMe(3) (6)]. Alternatively, 1 reacts with 3 to afford NaN[(1)SiMe(3)](2) (7). The structures of 2-5 and are presented and the formation of 2-7 is discussed. 相似文献
344.
The synthesis and structure of copper(I) complexes supported by N-substituted bicyclic guanidines is described. The N-methyl-substituted bicyclic guanidine 1,3,4,6,7,8-hexahydro-1-methyl-2H-pyrimido[1,2-a]pyrimidine (hppMe) reacted with copper(I) chloride to afford the ion-pair [Cu(hppMe)(2)][CuCl(2)] (1), a rare example of a compound containing an unsupported Cu...Cu interaction. The analogous reaction with CuI, however, afforded the molecular mu,mu-dihalo-bridged dimer [CuI(hppMe)](2) (2). Inclusion of a trimethylsilyl substituent at nitrogen provided a sufficiently sterically encumbered environment to support a two coordinate copper center in CuCl(hppSiMe(3)) (3). Compounds 1-3 have been fully characterized, including single-crystal X-ray diffraction studies. 相似文献
345.
Synthetic procedures to high oxidation-state complexes of niobium incorporating the bicyclic guanidinate 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate, [hpp]−, are described. The ligand source was either the N-trimethylsilylated guanidine or the lithium guanidinate and the reaction proceeded via elimination of trimethylsilylchloride or transmetallation from NbCl5, respectively. A 1:1 ratio of reagents afforded the mono-ligand product, Nb(hpp)Cl4 (1) and crystallisation from acetonitrile afforded the solvated species Nb(hpp)Cl4(MeCN) (1a), demonstrating the ability of the metal centre in 1 to bind small substrate molecules. A 2:1 ratio of lithium guanidinate to NbCl5 resulted in formation of the seven-coordinate, bis-ligand compound, Nb(hpp)2Cl3 (2). These products represent the first examples of guanidinate compounds in which niobium is stable in the +5 oxidation-state, believed to result from enhanced electron donation caused by the bicyclic framework of the ligand. The molecular structures of 1, 1a and 2 are reported, presenting for the first time an opportunity to describe bonding parameters within compounds of this type. 相似文献
346.
David M. Casper George P. Nora Jennifer R. Blackburn Jeromy T. Bentley Deanna C. Taylor Shawn R. Hitchcock 《Journal of heterocyclic chemistry》2002,39(4):823-828
[1,3,4]‐Oxadiazinan‐2‐ones bearing substitution at the N4‐position have been synthesized from norephedrine in good yield via N‐alkylation, nitrosation, reduction and cyclization. 相似文献
347.
348.
349.
B. Cetinkaya P.B. Hitchcock M.F. Lappert S. Torroni J.L. Atwood W.E. Hunter M.J. Zaworotko 《Journal of organometallic chemistry》1980,188(3):C31-C35
The 2,6-di-t-butyl-4-methylphenoxo ligand (ArO?) is ambidentate, giving rise to the O-bonded 15-electron d1 [Ti(η-C5H5)2OAr] and the η5 -[C(2)-C(6)]-bonded 18-electron d8 complex [Rh(ArO-η5)(PPh3)2], obtained from [{Ti(η-C5H5)2Cl}2]-LiO Ar and [Rh{N(SiMe3)2}(PPh3)2]-ArOH, respectively; the average TiC(η) distance is 2.362(10) Å, TiO 1.892(2) Å, and O:C(of Ar) 1.352(3) Å, and TiOC 142.3(2)°; in the RhI complex, C(2)C(6) are coplanar (with CC(av.) 1.38(2) Å). C(1)O 1.28 Å, and Rh to C(2) C(6) bond lengthsare in the range 2.19–2.65 Å. 相似文献
350.
The activated beta-lactam aldehydes 37, 41 and 57 were synthesised. Aldehydes 37 and 57 proved to be more versatile substrates for our "ring switching" strategy to homochiral glutamate antagonists than the corresponding compounds in the pyroglutamate or 6-oxopipecolinate series had been. Substantial libraries of homochiral heteroaromatic glycine derivatives with potential for activity at specific glutamate receptor sub-types were prepared from these aldehydes. The aldehyde 41, containing an additional anion stabilising group, underwent a retro-aldol process under "ring switching" conditions. 相似文献