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51.
Qiang Zhang Chong-Yu Xu Zengxin Zhang Yongqin David Chen Chun-ling Liu Hui Lin 《Journal of Hydrology》2008,353(3-4):215-227
This study investigated spatial and temporal patterns of trends of the precipitation maxima (defined as the annual/seasonal maximum precipitation) in the Yangtze River basin for 1960–2005 using Mann–Kendall trend test, and explored association of changing patterns of the precipitation maxima with large-scale circulation using NCEP/NCAR reanalysis data. The research results indicate changes of precipitation maxima from relative stable patterns to the significant increasing/decreasing trend in the middle 1970s. With respect to annual variability, the rainy days are decreasing and precipitation intensity is increasing, and significant increasing trend of precipitation intensity was detected in the middle and lower Yangtze River basin. Number of rain days with daily precipitation exceeding 95th and 99th percentiles and related precipitation intensities are in increasing tendency in summer. Large-scale atmospheric circulation analysis indicates decreasing strength of East Asian summer monsoon during 1975–2005 as compared to that during 1961–1974 and increasing geopotential height in the north China, South China Sea and west Pacific regions, all of which combine to negatively impact the northward propagation of the vapor flux. This circulation pattern will be beneficial for the longer stay of the Meiyu front in the Yangtze River basin, leading to more precipitation in the middle and lower Yangtze River basin in summer months. The significant increasing summer precipitation intensity and changing frequency in the rain/no-rain days in the middle and lower Yangtze River basin have potential to result in higher occurrence probability of flood and drought hazards in the region. 相似文献
52.
热带海洋珍珠贝类立克次体病研究 Ⅳ.组织细胞病理学研究 总被引:4,自引:0,他引:4
类立克次体(RLO)对大珠母贝和合浦珠母贝具有强烈的致病性,引起基本一致的病理变化.在急性坏死破坏期内,RLO导致外套膜、鳃、消化管、肝胰腺、生殖腺腺管及全身血管内皮系统等多器官组织的变性坏死,使器官组织结构的完整性遭到破坏,破坏程度与RLO包涵体的数目密切相关,而细胞的破坏与细胞内RLO的生长发育及繁殖到大量数目密切相关.鉴于此,将RLO引起的珍珠贝病称为类立克次体病(RLO病).RLO病呈急性变质性炎症和慢性增生性炎症病理,在前者细胞呈现崩解性坏死、溶解性坏死和退变性坏死;在后者存在实质细胞增生和纤维母细胞增生为纤维细胞并形成纤维化.根据炎症病理的发展过程,RLO病可分为急性坏死破坏期和慢性增生修复期. 相似文献
53.
Waldmeier effect [Waldmeier M., 1955. Ergebnisse und Probleme der Sonnenforschung. Second Ed., Leipzig, p. 154] states that the rise-time of a cycle depends upon a single parameter, namely the sunspot number Rz(max) at the maximum. Strong cycles have a steeper rise, while moderate cycles rise more slowly. In this paper, using the past data for sunspot cycles 1–23, these aspects are re-examined. It was noticed that the inverse relationship between Rz(max) and rise-time is discernable only when average patterns obtained by superposition of several cycles (separately for strong and weak cycles) are compared. In individual cycles, considerable deviations from the average patterns can occur (several tens of units of Rz and several months of rise-time). For a study of the relationship of Rz(max) with features in the early part of a cycle, the features chosen were Ro (i.e., Rz(min)) and Rz values Ra, Rb, and Rc, 12, 24 and 36 months, respectively, later than Ro (only 12-monthly running means were used). Ro had a moderate correlation (<0.6) with Rz(max), but Ra, Rb, Rc had better correlations. For hindsight predictions for cycles 18–23, the predictions for cycle 19 was grossly erroneous (observed value almost double of the predicted value). For other cycles, the errors were within 25%. For cycle 24, the Rz monthly values up to March 2008 give 12-month running means centered in June, July, August, September 2007 as 7.6, 6.5, 5.8, 6.1. Thus, though we cannot be absolutely sure yet that Rz(min) for cycle 24 has occurred, a tentative, provisional prediction using Rz(min) (i.e., Ro) as 5.8 is Rz(max)=113±19, i.e., in the range 94–132. This is an upper limit, as Ro value may reduce further in coming months, but most probably not very much. For Ro=5.0, the prediction would be Rz(max)= 109±17, while in the extreme hypothetical case of Ro=0.0, the prediction would be Rz(max)=79±14. 相似文献
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本研究以经2代家系选育的速生长系施氏獭蛤(Lutrariasieboldii)为亲本,通过巢式平衡设计构建了30个全同胞家系,以未经选育个体的同期子代作为对照,分析各家系及对照组不同阶段生长和存活差异。实验结果显示, 3月、9月和15月龄的施氏獭蛤全同胞家系生长性状均高于对照组(P0.05), 3月龄的家系壳长、壳高和体质量分别相对提高1.33%~9.33%、0.83%~15.83%和0.74%~25.19%,9月龄的家系壳长、壳高和体质量分别相对提高1.83%~10.46%、3.95%~12.45%和6.01%~20.60%,15月龄的家系壳长、壳高和体质量分别相对提高2.45%~25.62%、2.62%~15.01%和7.00%~28.73%,15月龄累积壳长、壳高和体质量生长量前3家系均值分别比家系平均提高9.38%、5.07%、9.34%;幼体期(1 d~30 d)、培育期(30 d~90 d)和养成期(90 d~450 d)各家系的存活率均值低于对照组5.61%、2.45%、2.08%,累积存活率均值低于对照组9.08%,但存活率排名前三的家系均值要高于对照组22.52%;根据全同胞家系生长和存活数据比较,家系A5、A12、A15于不同时期均表现出稳定优异的生长性状,家系A8、A15、A14于不同阶段均具有稳定的存活性状。以上结果表明,经选育施氏獭蛤家系的生长性状具有明显优势,其中,兼具有高生长和存活性状的家系A15可优先作为良种培育材料。 相似文献
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59.
William Earl Bardsley 《水文研究》2016,30(20):3730-3732
Multicomponent probability distributions such as the two‐component Gumbel distribution are sometimes applied to annual flood maxima when individual floods are seen as belonging to different classes, depending on physical processes or time of year. However, hydrological inconsistencies may arise if only nonclassified annual maxima are available to estimate the component distribution parameters. In particular, an unconstrained best fit to annual flood maxima may yield some component distributions with a high probability of simulating floods with negative discharge. In such situations, multicomponent distributions cannot be justified as an improved approximation to a local physical reality of mixed flood types, even though a good data fit is achieved. This effect usefully illustrates that a good match to data is no guarantee against degeneracy of hydrological models. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
60.
引进印度尼西亚大珠母贝人工育苗试验 总被引:2,自引:0,他引:2
在雷州半岛海域水温24.0~30.0℃、盐度30.8~32.5、pH8.0~8.3条件下,以牟氏角毛藻,亚心形扁藻,牟氏角毛藻、亚心形扁藻和小球藻,天然混合藻等4种饵料,进行印度尼西亚产大珠母贝亲贝促熟培育试验。结果表明:不同饵料组合在亲贝促熟百分率、排精产卵率和受精率之间差异不显著(P>0.05);阴干温差流水刺激可以有效诱导亲贝排精产卵,优选幼虫和投放合适的采苗器可以提高幼虫的变态率。 相似文献