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排序方式: 共有170条查询结果,搜索用时 17 毫秒
161.
S. C. Agarwala E. J. Hewitt 《The Journal of Horticultural Science and Biotechnology》2013,88(4):291-300
The behaviour of two clones of Williams’ Bon Chretien pear was compared when grafted on to Quince A rootstocks. One clone made strong unions with Quince A ; the other made weak unions and produced smaller trees than the compatible clone. Various graft combinations of the compatible and incompatible clones of Williams’ and of Beurre Hardy pear provided evidence that the structural weakness of the pear/quince unions was not caused by virus infection, and that the unions between the compatible Williams’ and Quince A were as good as those between the compatible pear variety Beurré Hardy and Quince A.The compatible Williams’ was infected with vein yellows and bark necrosis viruses; these have now been eliminated by a combination of heat treatment and propagation of young shoot tips. This healthy material will be available for distribution to commercial propagators if the crop yields of this clone are satisfactory. 相似文献
162.
Lawrence CR Schneider DP Schmidt M Bennett CL Hewitt JN Burke BF Turner EL Gunn JE 《Science (New York, N.Y.)》1984,223(4631):46-49
A new gravitational lens system, the triple radio source MG2016+112, has been discovered. Five emission lines at a redshift of 3.2733+/-0.0014 have been identified in the spectra of two stellar objects of magnitude 22.5 coincident with radio components 3.4 arc seconds apart. The lines are the narrowest ever observed in objects at such a large redshift. The redshift of a 23rd-magnitude extended optical object coincident with the third radio component has not been determined spectroscopically, but its known optical properties are consistent with those of a giant elliptical galaxy with a redshift of about 0.8. 相似文献
163.
Couse JF Hewitt SC Bunch DO Sar M Walker VR Davis BJ Korach KS 《Science (New York, N.Y.)》1999,286(5448):2328-2331
Mice lacking estrogen receptors alpha and beta were generated to clarify the roles of each receptor in the physiology of estrogen target tissues. Both sexes of alphabeta estrogen receptor knockout (alphabetaERKO) mutants exhibit normal reproductive tract development but are infertile. Ovaries of adult alphabetaERKO females exhibit follicle transdifferentiation to structures resembling seminiferous tubules of the testis, including Sertoli-like cells and expression of Müllerian inhibiting substance, sulfated glycoprotein-2, and Sox9. Therefore, loss of both receptors leads to an ovarian phenotype that is distinct from that of the individual ERKO mutants, which indicates that both receptors are required for the maintenance of germ and somatic cells in the postnatal ovary. 相似文献
164.
Berrettini W Bierut L Crowley TJ Cubells JF Frascella J Gelernter J Hewitt JK Kreek MJ Lachman H Leppert M Li MD Madden P Miner C Pollock JD Pomerleau O Rice JP Rutter JL Shurtleff D Swan GE Tischfield JA Tsuang M Uhl GR Vanyukov M Volkow ND Wanke K 《Science (New York, N.Y.)》2004,304(5676):1445-7; author reply 1445-7
165.
Y Xia E Kim XM Zhao JA Rogers M Prentiss GM Whitesides 《Science (New York, N.Y.)》1996,273(5273):347-349
Complex, optically functional surfaces in organic polymers can be fabricated by replicating relief structures present on the surface of an elastomeric master with an ultraviolet or thermally curable organic polymer, while the master is deformed by compression, bending, or stretching. The versatility of this procedure for fabricating surfaces with complex, micrometer- and submicrometer-scale patterns was demonstrated by the production of (i) diffraction gratings with periods smaller than the original grating; (ii) chirped, blazed diffraction gratings (where the period of a chirped grating changes continuously with position) on planar and curved surfaces; (iii) patterned microfeatures on the surfaces of approximately hemispherical objects (for example, an optical surface similar to a fly's eye); and (iv) arrays of rhombic microlenses. These topologically complex, micropatterned surfaces are difficult to fabricate with other techniques. 相似文献
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Gas-liquid scattering experiments provide direct observations of the fate of hydrogen-bonding molecules striking the surfaces of acidic liquids. Collisions of gaseous formic acid with concentrated sulfuric acid show that impinging monomers (HCOOH and DCOOD) scatter inelastically from the interface or become trapped by surface H2SO4. Most trapped DCOOD molecules undergo proton exchange before desorbing from the acid, indicating that gas-surface accommodation almost always leads to reaction with H2SO4 molecules. This proton transfer is not inhibited by dimerization of the formic acid: The dimers readily undergo intramolecular hydrogen bond cleavage and D-H exchange before desorbing from the acid. 相似文献
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