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Tadashi Sugano Mohamedally KurmooStephen J. Blundell William HayesSerge Vilminot 《Polyhedron》2011,30(18):3202-3205
Three divalent transition-metal (Co, Ni and Cu) complexes with the organic anion, 1,2,4-triazolato (tr), as a ligand molecule were prepared by means of hydrothermal syntheses and their magnetic properties were investigated by SQUID magnetometry. The Co(tr)2 and Cu(tr)2 complexes exhibit long range ordering below 8 and 30 K, respectively, while the Ni(tr)2 complex does not show any magnetic phase transition down to 1.8 K. The magnetization isotherms of Co(tr)2 and Cu(tr)2 measured at 2.0 K show hysteresis loops with the coercive fields of 0.5 and 4.7 kOe, respectively. At temperatures higher than about 50 K, the temperature dependence of the magnetic susceptibility of Co(tr)2, Ni(tr)2 and Cu(tr)2 follows the Curie-Weiss law with the Curie constants of 2.95, 0.945 and 0.420 emu K mol−1 and the Weiss temperatures of −62, −74 and −97 K, respectively. These results suggest that the magnetically ordered phases observed in Co(tr)2 and Cu(tr)2 at low temperatures come from antiferromagnetic interactions resulting in canted arrangements of magnetic moments of the transition-metal cations. We discuss here the magnetic interactions in these transition-metal complexes by referring the results of the magnetization measurements. 相似文献
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T. Williams D. J. Blundell A. Keller I. M. Ward 《Journal of Polymer Science.Polymer Physics》1968,6(9):1613-1619
This paper describes the application of gel permeation chromatography to the morphology of polymer single crystals. Various types of single crystals of polyethylene were etched with fuming nitric acid, and the molecular weight distributions of the degraded fragments determined. The crystal preparations studied were monolayer crystals grown from xylene solution at 85°C and multilayer crystals grown at 84°C and 70°C. In all cases peaks in the molecular weight distribution were observed corresponding to single and double transverses of the molecular chains through the lamellae. By using the chromatograph calibration described in a previous paper, the position of these peaks were compared and correlated with previous estimates of lamellar thickness from low-angle x-ray measurements. The relative positions of the peaks provide information regarding the nature of the fold surface. The results are found to be consistent with a model in which the majority of the molecules are tightly folded. 相似文献
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The paper demonstrates the potentiality of the self-seeding technique [3] for the growing of single crystals of polyethylene. It is shown that with appropriate measures, uniform single-layer crystals of strictly controlled habit can be obtained. Concrete recipes are given for the growing technique. The habit features are systematized as functions of crystallization temperature and concentration. Novel twin formations with coincident centers arising from this work are described and analyzed. Their origin is correlated with the result suggested by an associated investigation that the nuclei have a multicomponent structure [4]. The advantages of the new crystal-growing technique for other lines of work are pointed out. 相似文献
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Summary We describe an approach to protein structure comparison designed to detect distantly related proteins of similar fold, where the procedure must be sufficiently flexible to take into account the elasticity of protein folds without losing specificity. Protein structures are represented as a series of secondary structure elements, where for each element a local environment describes its relations with the elements that surround it. Secondary structures are then aligned by comparing their features and local environments. The procedure is illustrated with searches of a database of 468 protein structures in order to identify proteins of similar topology to porcine pepsin, porphobilinogen deaminase and serum amyloid P-component. In all cases the searches correctly identify protein structures of similar fold as the search proteins. Multiple cross-comparisons of protein structures allow the clustering of proteins of similar fold. This is exemplified with a clustering of /- and -class protein structures. We discuss applications of the comparison and clustering of three-dimensional protein structures to comparative modelling and structure-based protein design. 相似文献
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K.H. Chow Th. Jestädt S.J. Blundell S.R. Dunsiger W. Hayes B. Hitti M.A. Green R.F. Kiefl J.E. Millburn P.A. Pattenden F.L. Pratt M.J. Rosseinsky 《Hyperfine Interactions》1997,104(1-4):55-60
We report μSR measurements on a series of compounds with composition La2-xSrxNiO4+\delta where the net hole concentration x+2\delta is greater than 0.4. A magnetic transition is found in all the samples studied
which occurs at a composition‐dependent temperature TM. Below TM, clear precession signals are observed in zero applied magnetic field. The possible muon sites are discussed within the context
of dipole‐field calculations.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献