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A. F. J. Levi 《国外科技新书评介》2005,(6):16-16
本书是为电工和力学工程师、材料科学家和应用物理学家而编写的。书中材料虽取自量子力学理论书,但应用于实际,采用了实际工程的例子、练习和工作解法。内容从经典力学和电磁学出发,发展到现代量子力学及其应用。 相似文献
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Isotopic evidence for the moisture origin and composition of surface runoff in the headwaters of the Heihe River basin 总被引:5,自引:0,他引:5
LiangJu Zhao Li Yin HongLang Xiao GuoDong Cheng MaoXian Zhou YongGang Yang CaiZhi Li Jian Zhou 《科学通报(英文版)》2011,56(4-5):406-415
We investigated the moisture origin and contribution of different water sources to surface runoff entering the headwaters of the Heihe River basin on the basis of NECP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) re-analysis data and variations in the stable hydrogen and oxygen isotope ratios (?? D and ?? 18O) of precipitation, spring, river, and melt water. The similar seasonality in precipitation ?? 18O at different sites reveals the same moisture origin for water entering the headwaters of the Heihe River basin. The similarity in the seasonality of ?? 18O and d-excess for precipitation at Yeniugou and Urumchi, which showed more positive ?? 18O and lower d-excess values in summer and more negative ?? 18O and higher d-excess values in winter, indicates a dominant effect of westerly air masses in summer and the integrated influence of westerly and polar air masses in winter. Higher d-excess values throughout the year for Yeniugou suggest that in arid inland areas of northwestern China, water is intensively recycled. Temporal changes in ?? 18O, ??D, and d-excess reveal distinct contributions of different bodies of water to surface runoff. For example, there were similar trends for ?? D, ?? 18O, and d-excess of precipitation and river water from June to September, similar ?? 18O trends for river and spring water from December to February, and similar trends for precipitation and runoff volumes. However, there were significant differences in ?? 18O between melt water and river water in September. Our results show that the recharge of surface runoff by precipitation occurred mainly from June to mid-September, whereas the supply of surface runoff in winter was from base flow (as spring water), mostly with a lower runoff amount. 相似文献
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GAO Yan ZHANG Liang PAN YongHe WANG GuoDong XU Yang ZHANG WenHua ZHU JunFa 《科学通报(英文版)》2011,56(6):502-507
Ordered epitaxial ZrO2 films were grown on Pt(111) and characterized by low energy electron diffraction (LEED), synchrotron radiation photoemission spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS). The films were prepared by vapor deposition of zirconium in an O2 atmosphere followed by annealing under ultra high vacuum. At low coverages, the films grew as discontinuous two-dimentional islands with ordered structures. The size and structure of these islands were dependent on the coverage of Zr... 相似文献
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Natural selection has a critical role in the diversity of morphological traits. However, the genetic basis underlying the
evolution and diversity of morphological characteristics, particularly in the context an organism’s behavior, lifestyle, and
environment, is not well understood. The discovery of nasal chemoreceptors in mammals provided an opportunity to address this
question. Here, we identify 4 nasal chemoreceptor gene families (V1R, V2R, OR, and TAAR) from horse, guinea pig, marmoset and orangutan genome sequences, respectively. Together with previously described mammalian
nasal chemoreceptor gene repertoires, we found a significant positive correlation between functional gene number and morphological
complexity, both in the main olfactory system and the vomeronasal system. The combined analysis of morphological data, behavioral
data, and gene repertoires suggests that nocturnal mammals tend to possess more species-specific chemoreceptor genes and more
complicated olfactory organs than diurnal mammals. Moreover, analysis of evolutionary forces revealed the existence of positive
selection on the species-specific genes, likely reflecting the species-specific detection of odors and pheromones. Taken together,
these results reflect a rare case of adaptation to circadian rhythm activity at the genome scale, and strongly suggest that
the complexity of morphological olfactory organs and the diversification of nasal chemoreceptors in nocturnal mammals are
under selection for the ability to perceive the variety of odors that nocturnal mammals may encounter in their particular
dark environments. 相似文献
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Rao ZhiGuo Zhu ZhaoYu Jia GuoDong Chen FaHu Barton Loukas Zhang JiaWu Qiang MingRui 《科学通报(英文版)》2010,55(18):1931-1936
Using −24‰ and −14‰ as the endpoints of stable carbon isotopic composition of total organic carbon (δ13CTOC) of surface soil under pure C3 and C4 vegetation, and surface soil δ13CTOC data from eastern China, Australia and the Great Plains of North Amer- ica, we estimate the relative abundance of C3/C4 plants (i.e., the ratio of C3 or C4 biomass to local primary production) in modern vegetation for each region. The relative abundance of modern C3/C4 vegetation from each region is compared to the corresponding climatic parameters (mean annual temperature and precipitation) to explore the relationship between relative C4 abundance and climate. The results indicate that temperature controls the growth of C4 plants. However, even where temperature is high enough for the growth of C4 plants, they will only dominate the landscape when precipitation declines as temperatures increase. Our results are consistent with those of other investigations of the geographic distribution of modern C4 plant species. Therefore, our results provide an important reference for interpretation of past C3/C4 relative abundance records in these three regions. 相似文献
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ZHAO LiangJu YIN Li XIAO HongLang CHENG GuoDong ZHOU MaoXian YANG YongGang LI CaiZhi & ZHOU Jian Key Laboratory of Ecohydrology of Inl River Basin Cold Arid Regions Environmental Engineering Research Institute Chinese Academy of Sciences Lanzhou China State Key Laboratory of Frozen Soil Engineering Heihe Upstream Watershed Ecology-Hydrology Experimental... 《科学通报(英文版)》2011,(Z1)
We investigated the moisture origin and contribution of different water sources to surface runoff entering the headwaters of the Heihe River basin on the basis of NECP/NCAR(National Centers for Environmental Prediction/National Center for Atmospheric Research) re-analysis data and variations in the stable hydrogen and oxygen isotope ratios(δ D and δ 18O) of precipitation,spring,river,and melt water. The similar seasonality in precipitation δ 18O at different sites reveals the same moisture origin for water ... 相似文献
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HENDERSON Andrew 《科学通报(英文版)》2011,56(16):1714-1720
The molecular distribution of long-chain n-alkanes in 62 soil samples collected from diverse locations across eastern China was analyzed.The long-chain n-alkanes were mostly dominated by n-C29 or n-C31,regardless of the overlying vegetation type at each site.The results were compared with those summarized from the literature,covering more than 100 soil samples within China and more than 300 genera of modern plants distributed worldwide.There were similar n-alkane distribution patterns for most genera, with no clear differences among grasses,shrubs,and trees.The evidence from analyses of surface soils and modern plants indicates that the relationship between the molecular distribution of long-chain n-alkanes of surface soils and source vegetation is highly complex,and is influenced by many factors.Further,it is suggested that source vegetation types should not be simply inferred from distribution patterns of long-chain n-alkanes in sediments. 相似文献
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Surface soil samples collected over a high spatial resolution in eastern China were analyzed for carbon isotope composition (δ^13C) of total organic carbon (TOC) and higher plant-derived long-chain n-alkanes, with the latter reported as weighted mean values. The two sets of δ^13C values are significantly correlated and show similar trends in spatial variation. The spatial distribution of δ^13C shows less negative values in the mid-latitudes between 31°N and 40°N and more negative ones at higher and lower latitudes. This is consistent with previously reported carbon isotope data from surface soil phytoliths in the same region and suggests that the mid-latitude area provides relatively favorable growing condi- tions for C4 plants. Furthermore, δ^13C values of both TOC and long-chain n-alkanes from 12 surface soil samples collected from a small grassland in north China displayed similar carbon isotope values and the difference between paired δ^13C of a soil samples remains relatively constant. Our data demonstrate that in eastern China, soil δ^13C composition of both TOC and long-chain n-alkanes is effective indicators of C3/C4 ratios of the prevailing vegetation. This work suggests that -22‰ and -32‰ are good es- timated end members for the weighted mean δ^13C values of long-chain n-alkanes (C27, C29 and C31 n-alkanes) from soils under dominant C4 or C3 vegetation, allowing us to reconstruct paleovegetation trends. 相似文献
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