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181.
Charmaine van Blerk Gert J. Kruger 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(10):o537-o542
The redetermined crystal structures of hexane‐1,6‐diammonium dichloride, C6H18N22+·2Cl−, (I), hexane‐1,6‐diammonium dibromide, C6H18N22+·2Br−, (II), and hexane‐1,6‐diammonium diiodide, C6H18N22+·2I−, (III), are described, focusing on their hydrogen‐bonding motifs. The chloride and bromide salts are isomorphous, with both demonstrating a small deviation from planarity [173.89 (10) and 173.0 (2)°, respectively] in the central C—C—C—C torsion angle of the hydrocarbon backbone. The chloride and bromide salts also show marked similarities in their hydrogen‐bonding interactions, with subtle differences evident in the hydrogen‐bond lengths reported. Bifurcated interactions are exhibited between the N‐donor atoms and the halide acceptors in the chloride and bromide salts. The iodide salt is very different in molecular structure, packing and intermolecular interactions. The hydrocarbon chain of the iodide straddles an inversion centre and the ammonium groups on the diammonium cation of the iodide salt are offset from the planar hydrocarbon backbone by a torsion angle of 69.6 (4)°. All three salts exhibit thermotropic polymorphism, as is evident from differential scanning calorimetry analysis and variable‐temperature powder X‐ray diffraction studies. 相似文献
182.
Oluseye K. Onajole Patrick Govender Thavendran Govender Glenn E. M. Maguire Hendrik G. Kruger 《Structural chemistry》2009,20(6):1067-1076
The synthesis and NMR elucidation of eight novel pentacyclo-undecane (PCU) diamine compounds are reported. These ligands are
potential anti-inflammatory agents to be used against rheumatoid arthritis (RA). One-dimensional NMR techniques (1H and 13C spectra) show major overlapping of methine resonances of the “cage” (PCU) thereby making it extremely difficult to assign
all NMR signals. This overlapping occurs as a result of the substitutions made at the quaternary carbons (C-8/C-11) of the
cage. Two-dimensional NMR techniques proved to be a useful tool in overcoming this problem. 相似文献
183.
Doyle RP Julve M Lloret F Nieuwenhuyzen M Kruger PE 《Dalton transactions (Cambridge, England : 2003)》2006,(17):2081-2088
The reaction of copper(II) hydroxide with 2,2'-bipyridine (bipy) (1 : 1) in alkaline aqueous solution (pH 14) at room temperature affords the alternating carbonate/hydroxo-bridged copper(II) polymeric chain compound {[Cu3(bipy)3(mu-OH)2(mu-CO3)2].11H2O}n, 1, as determined by single-crystal X-ray diffraction. The structure of 1 is built up from two similar centro-symmetric dinuclear [(bipy)Cu(mu-OH)]2 cores which link together via bridging carbonate groups to mononuclear [(bipy)Cu] fragments to form the chain. Interdigitation of adjacent chains through pi-pi interactions, which involve each bipy ligand, forms sheets that are separated by the water molecules of crystallisation. Variable-temperature magnetic susceptibility measurements have shown that 1 behaves as an isolated spin doublet with two non-interacting spin triplets with the magnetic coupling through the bis-mu-hydroxo bridges being strongly ferromagnetic in nature. The hydrothermal reaction of copper(II) hydroxide, bipy and ammonium hydrogenphosphate (pH 8) yields a dinuclear copper(II) complex of formula {[Cu2(bipy)2(mu-OH)2(HPO4)(H2O)].4H2O}, 2, as determined by single-crystal X-ray diffraction. The structure of consists of an asymmetric dinuclear bis-mu-hydroxo copper(II) core with a monodentate hydrogenphosphate dianion coordinating to one copper(II) atom (above) and a water molecule to the other (below). Intra- and inter-molecular hydrogen bond interactions involving the hydrogenphosphate, water molecules and bis-mu-hydroxo groups link adjacent dinuclear fragments into chains, which interdigitate to form sheets that are separated by the water molecules of crystallisation. The investigation of the magnetic properties of 2 showed that the strength of the ferromagnetic interaction through the bis-mu-hydroxo bridges is influenced by the significant out-of-plane displacement of the hydrogen atom of the hydroxo groups, brought about through hydrogen bonding to the hydrogenphosphate ligand, and yielded the strongest ferromagnetic coupling yet reported for the bis-mu-hydroxo copper(II) core. 相似文献
184.
Zolfigol MA Khazaei A Moosavi-Zare AR Zare A Kruger HG Asgari Z Khakyzadeh V Kazem-Rostami M 《The Journal of organic chemistry》2012,77(7):3640-3645
3-Methyl-1-sulfonic acid imidazolium nitrate ([Msim]NO(3)) as a new Br?nsted acidic ionic liquid and nitrating agent was prepared and used for the efficient nitration of aromatic compounds (even aniline derivatives). The dramatic effect of this reagent by in situ generation of nitrogen dioxide as a radical on aromatic compounds to give nitroarenes has been studied. 相似文献
185.
Alexander Y. Kruger Marco A. López 《Journal of Optimization Theory and Applications》2012,154(2):339-369
This article investigates extremality, stationarity, and regularity properties of infinite collections of sets in Banach spaces. Our approach strongly relies on the machinery developed for finite collections. When dealing with an infinite collection of sets, we examine the behavior of its finite subcollections. This allows us to establish certain primal-dual relationships between the stationarity/regularity properties some of which can be interpreted as extensions of the Extremal principle. Stationarity criteria developed in the article are applied to proving intersection rules for Fréchet normals to infinite intersections of sets in Asplund spaces. 相似文献
186.
The acceleration of13C nmr relaxation rates by oxygen or by nitroxide radical was determined for representative perfluorohexane-heptane mixtures. In the 90:10 (v/v) solution, oxygen is found to affect perfluorohexane, but on the other hand, nitroxide affects the alkane the more strongly. In 15:85 solutions, little differentiation was noticeable although the data are less secure. In the former solution, domains are believed to exist, which are similar to the pure solvent in ability to dissolve paramagnetic relaxants. Force field calculations on the shape of fluorocarbon molecules are reviewed. 相似文献
187.
R.A. Kruger R.M. Bombelka K. Laqua 《Spectrochimica Acta Part B: Atomic Spectroscopy》1980,35(10):589-599
The magnetic field glow-discharge source (MFGDS) has been evaluated in the analysis of mild and alloyed steels. Its performance, as described by precision, line—background intensity ratio and the quality of calibration curves, was compared to results obtainable with the conventional Grimm glow-discharge source (GDS). The analytical performance was found to be comparable in the analysis of mild steels but difficulties, exhibiting themselves as the splitting of calibration curves, were encountered in the analysis of alloyed steels on account of their differing magnetic properties. 相似文献
188.
R.A. Kruger R.M. Bombelka K. Laqua 《Spectrochimica Acta Part B: Atomic Spectroscopy》1980,35(10):581-587
The fundamental characteristics of a new type of glow discharge source as designed by Grimm are described. The source incorporates a permanent magnet which causes the electrons in the plasma to execute a spiral motion about the lines of force of the electric field leading to enhanced collisional excitation, sputtering and light output as compared to the conventional source. The performance of the magnetic field glow discharge source in the analysis of mild and stainless steels is evaluated. 相似文献
189.
190.
R.K. Hanson J.P. Monat C.H. Kruger 《Journal of Quantitative Spectroscopy & Radiative Transfer》1976,16(8):705-713
Absorption of CO i.r. laser radiation by NO has been studied over the temperature range 300°–4000°K using a grating-tunable CO laser in conjunction with a room-temperature absorption cell and a shock tube. The CO laser line with strongest absorption at elevated temperatures was determined to be the V = 7 → 6, J = 12 → 13 line at 1935.4817 cm-1, which is nearly coincident with the 2ΠV = 0 → 1, J = 37/2 → 39/2 transition in NO. The absorption cell measurements (300°K) were used to infer the position of the NO absorption line (a Λ-doublet at 1935.492 and 1935.497 cm-1) as well as collision-broadening parameters in pure NO and NO dilute in foreign gases: 2γ° (collision-broadened full width at half maximum in cm-1 atm-1 at 300°K) = 0.110, NO-NO; 0.072, NO in Ar; 0.069, NO in Kr; 0.109, NO in N2. Calculations of the NO absorption coefficient at 1935.4817 cm-1 are presented for a range of conditions applicable to current studies in combustion and NOx kinetics. Shock tube measurements (630°–4000°K) supporting these calculations are also reported. 相似文献