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51.
Canal JP Jennings M Yap GP Pomeroy RK 《Dalton transactions (Cambridge, England : 2003)》2008,(10):1375-1382
A synthetic route to [Os4(mu-H)(mu-OH)(mu-CO)(CO)12] ( 1) has been devised through the activation of [Os4(CO)14] with Me3NO. The pyrolysis and photolysis of the reactant in the presence of a trace amount of water produces 1 in low yield. The solid-state structure of [Os4(mu-H)(mu-OH)(mu-CO)(CO)12 x H2O] (1 x H2O) reveals a butterfly Os4 skeleton with bridging H, OH and CO ligands as well as hydrogen-bonded molecules of water in the crystal lattice. A low-temperature 13C{1H} NMR spectroscopic study revealed a merry-go-round exchange of CO ligands around the Os3 plane containing the asymmetric bridging CO. The exposure of 1 x H2O to D2O yielded [Os4(mu-H)(mu-OD)(mu-CO)(CO)12]2. Although the solid-state, intramolecular structure of 2 closely matched that of 1 x H2O, the intermolecular structure did not: its crystal lattice contained no water of crystallization, a previously unreported crystallographic isotope effect. 相似文献
52.
Copper (I) guanidinate dimers were generated by a salt metathesis route and structurally characterized. The guanidinates differed from the known amidinate dimers because of a large torsion of the dimer ring. This had a direct effect on their thermal chemistry. The thermal reactivity was investigated by several methods, including a novel temperature-resolved, gas-phase method that was monitored by mass spectrometry. The copper guanidinates underwent carbodiimide deinsertion to produce copper metal at temperatures between 225 -and 250 degrees C in the gas phase and at 125 degrees C in solution. The amidinate investigated also showed copper deposition at 190 degrees C in the gas phase, and 135 degrees C in solution, but without carbodiimide deinsertion. The guanidinate compounds deposited crystalline copper at 225 degrees C in a simple chemical vapor deposition experiment. 相似文献
53.
Activation of elemental sulfur by the monovalent nickel complex [PhTt (tBu)]Ni(CO) [PhTt(tBu)=phenyl{tris[(tert-butylmethyl)thio]methyl}borate] generates the disulfidodinickel(II) complex 2. This species is alternatively accessible via thermal decomposition of [PhTt (tBu)]Ni(SCPh3). Spectroscopic, magnetic, and X-ray diffraction studies establish that 2 contains a mu-eta(2):eta(2)-S2 ligand that fosters antiferromagnetic exchange coupling between the Ni (II) ions. This observation is in contrast to the lighter congener, oxygen, which strongly favors the bis(mu-oxo)dinickel(III) structure. 2 oxidizes PPh 3 to SPPh3 and reacts with O2, generating several products, one of which has been identified as [(PhTt (tBu))Ni]2(mu-S) (3). 相似文献
54.
55.
Ultra-performance liquid chromatography/time-of-flight mass spectrometry based metabolomics of raw and steamed Panax notoginseng 总被引:4,自引:0,他引:4
Chan EC Yap SL Lau AJ Leow PC Toh DF Koh HL 《Rapid communications in mass spectrometry : RCM》2007,21(4):519-528
At present, metabolite profiling is of growing importance in herbal medicine fields such as breeding, formulation, quality control and clinical trials. This preliminary study indicated that ultra-performance liquid chromatography/time-of-flight mass spectrometry (UPLC/TOFMS)-based metabolomics allows direct detection of down-stream derivatives of metabolites, arising from the herbal formulation process. This analytical approach allows the discrimination and tentative authentication of unique biomarkers related to different herbal extracts using unsupervised multivariate principal component analysis (PCA). The tentative identification of biomarkers is complemented significantly by the accurate mass measurement of TOFMS and the high resolution and high retention time reproducibility rendered by UPLC. The application of this approach in herbal extract discrimination and ginsenoside biomarker discovery of raw and steamed Panax notoginseng (Burk.) F.H. Chen is demonstrated and discussed. 相似文献
56.
Jernigan FE Sieracki NA Taylor MT Jenkins AS Engel SE Rowe BW Jové FA Yap GP Papish ET Ferrence GM 《Inorganic chemistry》2007,46(2):360-362
The recently synthesized 3-tert-butyl-5-methyl-1,2,4-triazole reacted with KBH4 to give the new potassium tris(3-tert-butyl-5-methyl-1,2,4-triazolyl)borate K(Ttz(tBu,Me)) ligand. Ttz(tBu,Me) formed a four-coordinate (Ttz(tBu,Me))CoCl complex and five-coordinate (Ttz(tBu,Me))CoNO3 and (Ttz(tBu,Me))ZnOAc complexes. When these complexes were compared to their Tp(tBu,Me) analogues, it was found that Ttz(tBu,Me) resulted in negligible steric differences. K(Ttz(tBu,Me)) is more water-soluble than K(Tp(tBu,Me)), so bulky tris(triazolyl)borate ligands should lead to functional models for enzyme active sites in an aqueous environment and the creation of water-soluble analogues of Tp catalysts. 相似文献
57.
Let S
ni be a star of size n
i and let S=S
n1∪…∪S
nk≠S
2n−3∪S
1 or S
2∪S
2 be a spanning star-forest of the complete graph K
2n. We prove that K
2n has a proper (2n−1)-edge-colouring such that all the edges of S receive distinct colours. This result is very useful in the study of total-colourings of graphs.
Received: March 8, 1995 / Revised: May 16, 1997 相似文献
58.
Maryam Tayebani Sandro Gambarotta Glenn P. A. Yap 《Angewandte Chemie (International ed. in English)》1998,37(21):3002-3005
A nitrogen center was abstracted from a pyrrolyl ring to form the dinuclear nitrido- and dienyl-bridged complex 1 during the reaction of [{(tmeda)NbIICl}2(μ-Cl)3Li(tmeda)] with the lithium salt of 2,5-dimethylpyrrole (tmeda=N,N,N′,N′-tetramethylethylenediamine). A second product from this reaction is the amido-carbene-hydride niobium complex 2 , which likewise forms under C−N bond cleavage. 相似文献
59.
Wesley H. Monillas Glenn P. A. Yap Klaus H. Theopold 《Journal of chemical crystallography》2011,41(3):415-418
Abstract
The complex (bis(2,6-diisopropylphenyl)pentane-2,4-ketiminato)(9,10-dihydro-9,10-(ethenediolato)anthracene)(tetrahydrofuran)chromium(III) (1) has been synthesized and structurally characterized. Complex 1 crystallizes in the spacegroup Cc with the crystal cell parameters a = 22.285 (3) ?, b = 9.3317 (13) ?, c = 40.782 (6) ?, β = 99.338 (3)°, V = 8369 (2) ?3, and Z = 8. Two symmetry unique complex molecules were located in the asymmetric unit making Z′ = 2. The chromium atoms display square pyramidal coordination with THF located in the axial position. The previously neutral α-diketone moiety has been reduced by two electrons to an enediolate group with a corresponding increase of oxidation state of the chromium center. 相似文献60.
Papish ET Taylor MT Jernigan FE Rodig MJ Shawhan RR Yap GP Jové FA 《Inorganic chemistry》2006,45(5):2242-2250
Ligands of intermediate steric bulk were designed to mimic metalloenzymes with histidine and carboxlyate binding sites. The reaction between tris(3-isopropylpyrazolyl)methane and butyllithium followed by SO3NMe3 in THF yielded the new ligand lithium tris(3-isopropylpyrazolyl)methane sulfonate (LiTpmsiPr). Various metal salts reacted with LiTpmsiPr to give the octahedral complexes M(TpmsiPr)2 (M = Zn, Cu, Ni, Co, Fe) in which each ligand has N,N,O binding to the metal. In the reaction between LiTpmsiPr and ZnCl2, in addition to the major product Zn(TpmsiPr)2, [LiTpmsiPrZnCl2].2THF was also formed as a minor product with a tetrahedral zinc atom coordinated to either N,N,Cl,Cl in the solid phase or N,N,N,Cl in acetonitrile solution. Although TpmsiPr is coordinatively flexible and can act as a bipodal or tripodal ligand, it appears to favor the formation of octahedral L2M complexes. 相似文献