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991.
采用水生毒理联合效应相加指数法,比较了久效磷、辛硫磷、敌敌畏以及对硫磷的单剂和混合剂对扁藻的急性毒性和联合毒性。结果表明:久效磷和辛硫磷的联合毒性为协同作用;久效磷和敌敌畏的联合毒性为拮抗作用;久效磷和敌敌畏和对硫磷的48h联合毒性为协同作用,72h、96h则为拮抗作用。 相似文献
992.
993.
本文研究了精子入卵过程中太平洋牡蛎精子超微结构的变化规律。研究表明 ,精子入卵过程分为 4个时期 :顶体反应期、穿卵前期、穿卵期和融合期。顶体反应期 ,精子顶体物质释放 ,顶体致密部分向外延伸 ,形成 1层保护膜 ,亚顶体腔开始向顶端突起 ;穿卵前期 ,亚顶体腔前突形成顶体锥 ,并向卵膜释放亚顶体物质 ,精子外膜后移 ;穿卵期 ,精子核及线粒体进入卵膜形成的受精锥 ,线粒体数量减少 ,顶体突消失 ,精子外膜和尾部脱落 ;融合期 ,精子核进入卵内与质膜融合 ,核解体。 相似文献
994.
Uma?Shankar Babita?Sinha N.?K.?ThakurEmail author Ramesh?Khanna 《Marine Geophysical Researches》2005,26(1):29-35
Velocity analysis of multi-channel seismic (MCS) data and amplitude-versus-offset (AVO) modeling provides an efficient way
of identifying gas hydrate and free gas, and therefore the nature of the bottom-simulating reflector (BSR). Additionally,
AVO modeling also yields estimates of the hydrate concentration and free gas saturation across the BSR in terms of velocity
distribution. In the present study, we apply directivity correction in order to accentuate the AVO behavior. Modeling for
AVO pattern of the observed BSR over the Kerala–Konkan Offshore Basin may provide the probable velocity distribution across
the BSR and thereby infer whether hydrate or hydrate/free gas model governs the AVO observations. Initial results indicate
the possible presence of free gas underlying the gas hydrates-saturated sediments in this region. 相似文献
995.
Morphological features of two-ribbon flares have been studied, using simultaneous ISEE-3 hard X-ray records and high-resolution Big Bear H movies for more than 20 events. Long-lasting and complex hard X-ray bursts are almost invariably found associated with flares of the two-ribbon type. We find at least three events, namely March 31, 1979, April 10, 1980, and July 1, 1980, where the occurrence of individual spikes in hard X-ray radiation coincides with suddenly enhanced H emission covering the sunspot penumbra. There definitely exist important ( 1B) two-ribbon H flares without significant hard X-ray emission. 相似文献
996.
Z. Švestka H. W. Dodson-Prince S. F. Martin O. C. Mohler R. L. Moore J. T. Nolte R. D. Petrasso 《Solar physics》1982,78(2):271-285
We present revised values of temperature and density for the flare loops of 29 July 1973 and compare the revised parameters with those obtained aboard the SMM for the two-ribbon flare of 21 May 1980. The 21 May flare occurred in a developed sunspot group; the 29 July event was a spotless two-ribbon flare. We find that the loops in the spotless flare extended higher (by a factor of 1.4–2.2), were less dense (by a factor of 5 or more in the first hour of development), were generally hotter, and the whole loop system decayed much slower than in the spotted flare (i.e. staying at higher temperature for a longer time). We also align the hot X-ray loops of the 29 July flare with the bright H ribbons and show that the H emission is brightest at the places where the spatial density of the hot elementary loops is enhanced.presently at Big Bear Solar Observatory, Caltech, California, U.S.A.presently at The Marshall Space Flight Center, Huntsville, Alabama, U.S.A. 相似文献
997.
998.
This article focuses on post-1945 land-use development in the Sudetenland region. The wider historical and political consequences are discussed in the beginning as well as the methodical tools used in long-term land-use research in the Czech Republic so far. The important cleavage between borderland and inland is shown in regard to the different land use and land exploitation. Different parts of the borderland are examined in closer detail and the dissimilarity between areas in the western frontier and Northern Bohemia is explained, including the iron curtain effect. 相似文献
999.
TheUBV photometry of the detached F-type eclipsing binary BK Pegasi is presented. The light curve solution by a simple spherical model assumption suggests that a slightly hotter, larger and more luminous primary was eclipsed during the primary minimum. Combined with the radial velocity curves in Popper (1983), it was used to determine anew the system's parameters. The age and the metal abundance of the system were estimated as (3.3 ± 0.2) × 109 yr andz = 0.028 ± 0.003 from a comparison with the new grids of stellar models and the isochrones by Schalleret al. (1993). The distance of the system was estimated as 290 pc. 相似文献
1000.
利用北部湾海域浮标站20152018年的海浪观测资料,对北部湾海域的灾害性海浪特征及影响天气系统进行了分析,结果表明:北部湾海域灾害性海浪平均每年出现2.5次,最多年出现4次(2016年);10月出现的灾害性海浪最多,8月的次之;灾害性海浪的最大有效波高3.0~5.0m,波向以N和NW方位最多,分别占30%;灾害性海浪过程持续时间最长为1190min,最短为20min;台风和冷空气是引发灾害性海浪的主要天气系统,台风引发的占60%,冷空气引发的占40%。其中以台风引发的灾害性海浪过程最多、海浪最高、持续时间最长。引发灾害性海浪的台风移动路径绝大部分经过北部湾;东路和中路冷空气更有利于北部湾灾害性海浪形成,灾害性海浪形成时常有一个冷高压位于四川盆地到江汉平原一带,中心气压在1030hPa以上,北海与海口的最大海平面气压差在4.3hPa以上。 相似文献