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排序方式: 共有222条查询结果,搜索用时 265 毫秒
1.
Alexander Ya. Kruger 《Set-Valued Analysis》2006,14(2):187-206
The paper continues investigations of stationarity and regularity properties of collections of sets in normed spaces. It contains
a summary of different characterizations (both primal and dual) of regularity and a list of sufficient conditions for a collection
of sets to be regular. 相似文献
2.
Krishna Bisetty Francesc J. Corcho Josep Canto Hendrik G. Kruger Juan J. Perez 《Journal of Molecular Structure》2006,770(1-3):221-228
In this paper, we report on the conformational profile of the pentacyclo-undecane (PCU) cage tripeptide carried out by molecular dynamics (MD) simulation using water as an explicit solvent. The MD solution phase studies carried on the model peptide analogues (A)=Ac–Ala–Ala–Ala–NHMe; (B)=Ac–Cage–Cage–Cage–NHMe; (C)=Ac–Ala–Cage–Ala–NHMe and (D)=Ac–Ala–Pro–Ala–NHMe, are used as a complimentary technique to the corresponding gas phase simulated annealing (SA) study previously carried out in our laboratory. No significant structural changes were observed over the MD trajectories. However, the results reported here provide further evidence that the (PCU) cage amino acid exhibits C7eq, C7aq, R and L conformations, and the theoretical results suggest that the PCU cage amino acid is a strong β-turn inducer. These results support the prediction that when the PCU cage residues are in the (i) and (i+2) positions, the β-turn can be extended in either direction to form anti-parallel β-pleated sheets, thereby forming the basis of the mechanism for the folding back of the chain in a cross-β-turn structure. 相似文献
3.
Whereas the complex [Ru(phen)2Medpq]2+(phen=1,10-phenanthroline; Medpq=2-methyldipyrido[3,2-f:2',3'-h]-quinoxaline) is luminescent in both aqueous and nonaqueous solutions, [Ru(phen)2dpqa]2+(2-pentylamidodipyrido[3,2-f:2',3'-h]-quinoxaline) does not emit in water but does so strongly in organic solvents or when bound to DNA--suggesting its use as a photochemical and photophysical probe for nucleic acids. 相似文献
4.
Tynan E Jensen P Kelly NR Kruger PE Lees AC Moubaraki B Murray KS 《Dalton transactions (Cambridge, England : 2003)》2004,(21):3440-3447
We report herein the single crystal structures of four metal-organic framework complexes incorporating the 4,4'-dicarboxy-2,2'-bipyridine ligand, H(2)dcbp: alpha-[Co(dcbp)(H(2)O)(2)], 1; beta-[Co(dcbp)(H(2)O)(2)], 2, [Ni(dcbp)(H(2)O)(2)], and [[Mn(dcbp)].1/2DEF], 4 (DEF = diethylformamide). In each complex the ligand is deprotonated giving neutral species with 1:1 stoichiometry that form three-dimensional coordination polymers. Supramolecular isomerism (polymorphism) in 1 and 2 arises from the different ligand connectivity around the octahedral Co(II) centres. The two coordinated water molecules in 1 occupy cis positions, which are trans to the chelating bipyridine nitrogen atoms, leaving the carboxylate oxygen atoms in axial trans positions. In 2 all like donors occupy cis positions. Different modes of carboxylate coordination in 1 and 2 give dissimilar network topologies. A rare example of two interpenetrating 6(4)8(2)-b (quartz-like) chiral networks in 1 results from both dcbp carboxylate groups coordinating in a monodentate fashion to adjacent Co(II) centres, whereas in 2 only one carboxylate group bridges between adjacent Co(II) centres giving rise to a single chiral (10,3)-a net. In 1 and 2 the coordinated water molecules hydrogen bond to the non-coordinated carboxylate oxygen atoms. These interactions give rise to water-carboxylate double helices in , and support the coordination network in 2. Strikingly for a pair of dimorphs the crystal densities of 1 and 2 differ by ca. 0.3 g cm(-3)(1.654 vs. 1.940 g cm(-3), respectively). Compound 3 is isomorphous with 1 and likewise features two chiral interpenetrating nets of quartz topology. In 4, chelating bipyridine nitrogen atoms and four carboxylate oxygen atoms from a total of five adjacent dcbp ligands provide distorted octahedral geometry around Mn(II). The carboxylate groups bridge adjacent Mn(II) centres to produce bis-carboxylato chains which cross-link and generate a 3D network that is perforated with channels. The channels are occupied with disordered DEF molecules. The network topology in 4 is quite different to 1-3 and has a (4.6(2))(4(2).6)(4(3).6(6).8(6)) Schlafli notation. Magnetic susceptibility studies performed on 1, 2, [[Mn(dcbp)].1/2DMF] 5 (DMF = dimethylformamide) and [[Mn(dcbp)].2H(2)O] 6 reveal very weak antiferromagnetic coupling between the metal centres in each case. 相似文献
5.
Conerney B Jensen P Kruger PE MacGloinn C 《Chemical communications (Cambridge, England)》2003,(11):1274-1275
The synthesis and structural characterisation of a novel C3-symmetric tris-bidentate ligand, L, featuring a triphenylamine core appended by pyridylimine coordination sites is reported: 1H NMR compleximetric titration studies with Ag(I) and ESMS indicate the presence of [Ag3L2]3+ species in solution, consistent with the formation of a trinuclear double helicate complex: the Trinity helix. 相似文献
6.
Hui Yang Xing Chen Guoxiang Hu Wan-Ting Chen Siobhan J. Bradley Weijie Zhang Gaurav Verma Thomas Nann De-en Jiang Paul E. Kruger Xiangke Wang He Tian Geoffrey I. N. Waterhouse Shane G. Telfer Shengqian Ma 《Chemical science》2020,11(13):3523
Optimizing interfacial contacts and thus electron transfer phenomena in heterogeneous electrocatalysts is an effective approach for enhancing electrocatalytic performance. Herein, we successfully synthesized ultrafine β-Mo2C nanoparticles confined within hollow capsules of nitrogen-doped porous carbon (β-Mo2C@NPCC) and found that the surface layer of molybdenum atoms was further oxidized to a single Mo–O surface layer, thus producing intimate O–Mo–C interfaces. An arsenal of complementary technologies, including XPS, atomic-resolution HAADF-STEM, and XAS analysis clearly reveals the existence of O–Mo–C interfaces for these surface-engineered ultrafine nanostructures. The β-Mo2C@NPCC electrocatalyst exhibited excellent electrocatalytic activity for the hydrogen evolution reaction (HER) in water. Theoretical studies indicate that the highly accessible ultrathin O–Mo–C interfaces serving as the active sites are crucial to the HER performance and underpinned the outstanding electrocatalytic performance of β-Mo2C@NPCC. This proof-of-concept study opens a new avenue for the fabrication of highly efficient catalysts for HER and other applications, whilst further demonstrating the importance of exposed interfaces and interfacial contacts in efficient electrocatalysis.Ultrafine β-Mo2C nanostructures encapsulated in N-doped carbon capsules featuring O–Mo–C interfaces as the active sites for HER have been unveiled. 相似文献
7.
Sai Kumar Chakka Zamani E.D. Cele Sphelele C. Sosibo Vivian Francis Per I. Arvidsson Hendrik G. Kruger Glenn E.M. Maguire Thavendran Govender 《Tetrahedron: Asymmetry》2012,23(8):616-622
A series of novel TIQ based N,N′-oxide ligands were synthesised and screened for their catalytic activity in the enantioselective conjugate addition of thioglycolate to chalcones. Bulky groups on the side chain of the TIQ backbone provided the highest enantioselectivity of up to 88% with 10 mol % catalyst loading. It was also observed that these reactions proceeded optimally in the presence of dichloromethane as a solvent. Screening of various metals emphasized La(OTf)3 as the ideal pre-catalyst for this particular reaction. 相似文献
8.
9.
Wolfgang Reich Terry S. Bright Wolfgang Malisch Carl Kruger 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract The reaction of the metal phosphorus double bonded species Cp(CO)2M=PR2 (M = Mo, W; R = aryl, alkyl) (1)1) with diverse diazoalkanes, alkenes, alkines and dienes results in the facile formation of the [2+1]-, [2+2]1- and [2+4]-cycloaddition products 2a-c. 相似文献
10.
Omar R. Musaev Eli A. Sutter Jerzy M. Wrobel Michael B. Kruger 《Journal of nanoparticle research》2012,14(2):654-6
A eutectic AuGe target immersed in distilled water was ablated by pulsed ultraviolet laser light. The structure of the ablated
material was investigated by high-resolution transmission electron microscopy (HRTEM). The images show formation of nanowire
structures of AuGe up to 100 nm in length, with widths of 5–10 nm. These nanostructures have Ge content significantly lower
than the target material. Electron diffraction demonstrates that they crystallize in the α-AuGe structure. For comparison,
laser ablation of pure Au and pure Ge targets was also performed under the same conditions. HRTEM shows that Ge forms spherical
nanoparticles with a characteristic size of ~30 nm. Au forms spherical nanoparticles with diameters of ~10 nm. Similar to
AuGe, it also forms chainlike structures with substantially lower aspect ratio. 相似文献