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排序方式: 共有407条查询结果,搜索用时 15 毫秒
401.
AF Goncharov VV Struzhkin MS Somayazulu RJ Hemley HK Mao 《Science (New York, N.Y.)》1996,273(5272):218-220
Protonated and deuterated ices (H2O and D2O) compressed to a maximum pressure of 210 gigapascals at 85 to 300 kelvin exhibit a phase transition at 60 gigapascals in H2O ice (70 gigapascals in D2O ice) on the basis of their infrared reflectance spectra determined with synchrotron radiation. The transition is characterized by soft-mode behavior of the nu3 O-H or O-D stretch below the transition, followed by a hardening (positive pressure shift) above it. This behavior is interpreted as the transformation of ice phase VII to a structure with symmetric hydrogen bonds. The spectroscopic features of the phase persisted to the maximum pressures (210 gigapascals) of the measurements, although changes in vibrational mode coupling were observed at 150 to 160 gigapascals. 相似文献
402.
MJ Yoo TA Fulton HF Hess RL Willett LN Dunkleberger RJ Chichester LN Pfeiffer KW West 《Science (New York, N.Y.)》1997,276(5312):579-582
A single-electron transistor scanning electrometer (SETSE)-a scanned probe microscope capable of mapping static electric fields and charges with 100-nanometer spatial resolution and a charge sensitivity of a small fraction of an electron-has been developed. The active sensing element of the SETSE, a single-electron transistor fabricated at the end of a sharp glass tip, is scanned in close proximity across the sample surface. Images of the surface electric fields of a GaAs/AlxGa1-xAs heterostructure sample show individual photo-ionized charge sites and fluctuations in the dopant and surface-charge distribution on a length scale of 100 nanometers. The SETSE has been used to image and measure depleted regions, local capacitance, band bending, and contact potentials at submicrometer length scales on the surface of this semiconductor sample. 相似文献
403.
M. M. KASSEM P. C. THOMAS D. G. CHAMBERLAIN S. ROBERTSON 《Grass and Forage Science》1987,42(2):175-183
Three change-over experiments were conducted to determine the effect on ad libitum silage intake and milk production in dairy cows of treatment of barley supplements with an acid-formaldehyde reagent designed to reduce the rate of starch and protein digestion in the rumen. In Experiment 1 there were six dietary treatments consisting of silage with supplements of 4·0,6·5 and 9·0 kg d-1 of barley given untreated or treated with formaldehyde reagent (8·1 t-1). In Experiment 2 there were four dietary treatments consisting of silage with supplements of barley (7·0 kg d-1) or barley and fishmeal (6·0 kg d-1 plus 1·0 kg d-1), with the barley untreated or treated with formaldehyde reagent (15·1t-1). In Experiment 3 there were four dietary treatments consisting of silage given alone or with supplements of barley (9·0 kg d-1). Treated barley (15·1 t-1, 9·0 kg d-1) and barley plus sodium bicarbonate (9·0 kg d-1 plus 25·0 g d-1). Treatment of the barley supplement with formaldehyde reagent had no effect on silage intake or milk production in Experiment 1 where the rate of application of the reagent was low and the basal silage-barley diet was limiting in rumendegradable nitrogen. However, in Experiments 2 and 3 treated barley supplements were associated with improvements in silage intake and milk production. As compared with corresponding control diets containing untreated barley, increases in silage intake ranged from 0 to 0·16 of the control value, whilst associated increases in the yields of milk, milk fat, milk protein and lactose were 0·077–0·089, 0·016–0·026, 0·092–0·118 and 0·080–0·092 of the control value. These responses are discussed in relation to the increases in silage intake and milk production observed with fishmeal supplementation of the diet in Experiment 2 and inclusion of sodium bicarbonate in Experiment 3. 相似文献
404.
Terminology and definitions in studies of grassland plants 总被引:2,自引:0,他引:2
HENRY THOMAS 《Grass and Forage Science》1980,35(1):13-23
405.
Two selection lines of Lolium perenne , which had different leaf lamina osmotic potential (Ψs ) when droughted in controlled environments, were grown as vegetative simulated swards in containers of soil 1·0 × 1·3 × 0·9 m deep in the glasshouse. Water was withheld during July, August and September.
Under irrigation the low-ψs line had leaf lamina and leaf base ψs 0·06 MPa lower than the high-ψs line. Under drought, the two lines did not differ significantly in lamina ψs but leaf base ψs was 0·16 MPa lower in the low line than in the high line. Upon rewatering, most of the osmotic adjustment in the leaf bases was lost within 2 d, but that in the laminae was more stable.
Herbage growth under irrigation was similar in the two lines until September, when it was greater in the highψs line. Drought reduced herbage growth, and also regrowth rates following rewatering, but the two lines did not differ in their sensitivity to drought.
Selection for low ψs also increased leaf extension rates, and reduced tillering and leaf water conductance of irrigated plants.
The results are discussed in relation to selecting for improved drought resistance on the basis of physiological characters. 相似文献
Under irrigation the low-ψ
Herbage growth under irrigation was similar in the two lines until September, when it was greater in the highψ
Selection for low ψ
The results are discussed in relation to selecting for improved drought resistance on the basis of physiological characters. 相似文献
406.
407.
选择长江流域油菜主产区望江县研究安徽省土壤有效S状况和油菜施用S肥的效应.结果表明,望江县土壤有效S平均含量15.31 mg/kg,缺S状况较为严重,缺S土壤所占比例高达61.29%,潜在性缺S土壤所占比例为35.48%.主要土壤类型中灰潮土缺S状况最为严重,有效S不足的土壤所占比例高达80%.在有效S极为缺乏的灰潮土上,油菜施用S肥具有极为显著的增产效果,与施尿素的对照相比,盆钵栽培增产1O.89%~26.21%,田间试验产量提高9.42%~16.43%,平均增产15.80%和13.29%. 相似文献