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1.
福建柏属的起源与分布   总被引:3,自引:0,他引:3  
福建柏属植物约起源于晚侏罗纪,起源中心在东亚环太平洋地区,第四纪冰期后仅福建柏1种残存中国南方和越南北方,形成残遗中心。据史料分析,福建柏历史上分布较现代广泛,自中国东部福建沿海至云贵高原东南部沿南岭山脉纬度一线基本呈连续分布。现代中心分布区在东经110°~119°,北纬24°30′~26°30′,呈间断分布;垂直分布海拔500~1800m,往西、往北分布海拔较高,往东、往南分布海拔较低;分布区属中亚热带湿润气候。福建柏为浅根性树种,树冠承雪量大,易遭大风和冰冻危害,成为其向高海拔地区发展的限制因素。  相似文献   

2.
对1990~1991年在江苏海州湾水域(119°10'~120°10'E,34°0'~35°10'N)采集的标本进行鉴定,共有18种,隶属12科14属.其中水螅水母类16种,栉水母类2种.其种类组成以暖温带近岸低盐种为主.在海州湾四个季度均有水母出现,分布范围较广,遍布本次调查海区各个站位,密集区位于119°20'~119°30'E,34°40'~35°00'N之间的海域.分布面以5月和8月最广,密集度也高,尤以5月的个体生物最最高,8月次之,11月和2月较少.  相似文献   

3.
ZnCl2与POM的合成和结构   总被引:1,自引:0,他引:1  
ZnCl2与POM生成1:2加成物「Zn(POM)2Cl2」,C12H12Cl2N4O6Zn,晶体必三科晶系,空间群为P1,晶胞系数为a=11.755(11)×10^-10m,b=12.3574(7)×10^-10m,c=6.592(4)×10^-10m,a=102。732(5)°,β=92.074(6)°,γ=110.124(60°,V=876.2×10^-30m,MR=444.53,z=2,d  相似文献   

4.
天然气氦同位素分布与大地构造环境   总被引:2,自引:0,他引:2  
根据中国大陆主要含油气盆地天然气的^3He/^4He数据,首次系统研究了天然气中氦同位素空间分布与中国大地构造环境的关系。中国东部滨太平区^3He/^4He平均值R=2.08×10^-5>Ra,为含幔源氦的二元混合型氦;中西部区的R=4.96×10^-8,基本为地壳一元放射型氦;华北-中原区的R=8.00×10^-7,为介于东与中西部之间的过渡型氦。整体而言,^3He/^4He值呈自东而西随远离西  相似文献   

5.
1.制造简单,修整方便,容易掌握。 2.断屑范围广,并且可靠。 3.硬质合金磨去量少,刀片利用率高。 4.切屑向待加工面排除,保证加工质量,便于操作。 三角形平面上几何参数的合理值力:a=1—2毫米。γθ=0°,λθ=-5°-10°。塑性材 料λθ取大值。适用的切削用量范围力:t=l—5毫米,S≥0.25毫米,试验和实践证明, 几何参数──三角形断屑法是一种有实际意义和有发展前途的方法。  相似文献   

6.
标题化合物Yb(Pi)_3(Bl5C5)_2·2H_2O·CH_3CN(I)及Y(Pi)_3(Bl5C5)_2·2H_2O·CH_3CN(Ⅱ)为同晶结构,均为3斜晶系,空间群为P-对晶体(I),a=12.753(1)A,b=13.810(2)A.c=19.609(2)A,α=81.37(3)°,β=71.58(3)°,γ=70.71(2)°,Z=2.D_c=1.468g·cm ̄(-3),μ=15.928cm ̄(-1)(MoKα),M_r=1471,04,F(000)=745,R=0.031,R_w=0.039;对晶体(Ⅱ),α=12.785(1)A,b=13.850(3)A,c=19.571(2)A,α=81.05(3)°,β=70.92(2)°,γ=70.62(3)°,Z=2,Dc=l.485g·cm ̄(-3),μ=10.441cm ̄(-1)(MoKα),M_r=1386.9l,F(000)=7l4,R=0.065,R_w=0.078.测定结果表明,中心稀土离子Yb ̄(3+)(或Y ̄(3+)直接与3个苦味酸阴离子和2个水分子配位,此水化镱(或钇)苦味酸盐通过水桥氢键与冠醚Bl5C5相联而形成一个大的疏水性  相似文献   

7.
提出用波束等价和采样合成定理对参差宽带阵列进行阵元布阵和波束优化设计的方法.给出根据这一方法进行模拟实验的结果.结果表明,通过等价模拟可得到合理的布阵方案和最优波束分布.在±20°范围内,模拟精度在1%以内;在主瓣范围±5°以内,实验结果与模拟结果吻合较好.  相似文献   

8.
论述了去污上光剂的去污上光原理,配方的选择以及主要技术指标的测定方法。结果表明,去污上光剂表面张力为24.3×10-3N/m,5min后润湿面为14.1°~12.9°  相似文献   

9.
氧方酸制备方法的改进及其晶体结构   总被引:7,自引:0,他引:7  
改进了以全氯代-1,3-丁二烯为原料制备氧方酸的方法,收率为65%~68%.测定了氧方酸的晶体结构;三斜晶系,空间群P_1,α=5.0741(6)nm,b=5.0715(5)nm,c=5.2912(8)nm,β=58.57(1)°,z=1,Dc=1.915g·cm ̄(-3),Vc=0.99115nm ̄3,R_w=0.0258.其电子云密度图表明四碳环内存在一缺电空间或为1电子陷阱,四个碳碳键键长平均化.  相似文献   

10.
讨论了10°.s^-2和5°.s^-2强度旋转运动后豚鼠脑组织乙酰胆碱酯酶及乳酸脱氢酶的活性变化,随着训练AchE活性先下降后上升,而LDH活性则先上升后下降。  相似文献   

11.
本文从植物种群个体分布格局在时空系列上动态变化规律的研究,探讨植物种群结构的演变特点。种群分布格局与种群数量动态密切相关,种群数量的消长造成了种群分布格局类型(typc),格局规模(scale)、格局强度(intensity)、格局纹理(grain)的相应变化。在时间,空间梯度系列上,随着环境旱化程度的加强。旱中、中旱生类型的种群或消失,或种群分布格局的规模逐浙缩小,格局强度加强,格局纹理变粗;早生类型的种群分布格局观模则有扩大的趋势,格局强度减弱,格局纹理变细,可见,环境因子的改变,特别是水分状况的改变,是种群分布格局变化的主要影响因素。  相似文献   

12.
通过研究松嫩草原羊草可燃物含水率的变化,揭示羊草可燃物燃烧性的变化规律.结果表明,在羊草枯死过程中,其燃烧性呈上升趋势,10月末达到最高值;在枯草期,其燃烧性变化不显著.雨后羊草可燃物燃烧性降低,经过7~8 h恢复到雨前水平.另外,可燃物燃烧性的变化规律与气象因子密切相关.  相似文献   

13.
根据考察中国著名自然风景区的分布规律,发现其分布有很强的边缘效应,为量度其起边程度,建立了地理点的趋向指数,并以此进一步考察比较各区域自然风景区的边缘效应程度,最后,以区域系统观点说明自然风景区等地理点分布的趋边效应与区域自然地理熵有直接关系.  相似文献   

14.
中国南海北部新生代古环境的变迁   总被引:2,自引:0,他引:2  
为了解中国南海北部新生代古环境的变迁,在分析参考相关科学成果的基础上,综述该区域的古环境的变迁。早第三纪珠江口盆地以陆相、河湖相沉积为主,气温凉爽,属暖温带至北亚热带环境;晚第三纪,从晚渐新世到上新世晚期,该区域由淡水湖泊沉积环境,逐渐过渡到海、陆交互环境、潮问带或浅水滨海沉积环境、浅海环境等,气候也演变成潮湿的热带、亚热带气候。第四纪,随着冰期、间冰期的波动,沉积环境也分别呈近岸陆面剥蚀环境一浅水滨海沉积环境或浅海环境的交替。香港地区“岗岭山坡”区段属陆面风化剥蚀环境,而在“河谷平原”则由陆面风化剥蚀环境演变为陆面河、湖相或沼泽沉积环境。古环境的变迁主要受太阳幅射脉动状态等综合因素的影响。  相似文献   

15.
Climate change is considered a top threat to biodiversity, but the relative roles of contemporary climate versus the rate of climate change in determining spatial patterns of biodiversity are far from clear. China has a very diverse flora and harbors a high percentage of endemic species, but the mechanisms underlying spatial patterns of plant endemism are poorly understood. This study explores the geographical patterns of a representative sample of 555 endemic seed plant species at the scale of 0.5° latitude × 0.5°longitude. Ordinary least squares and spatial autoregressive models were compared to assess the relationship between richness of endemics and the rate of climate change in the past century, as well as a group of contemporary climate variables. In China, a high level of endemism was associated with high elevation and low rate of climate change. However, contemporary climate had a stronger impact than climate change velocity in the past century on endemic species richness patterns. Specifically,mean annual precipitation and annual range of temperature were important contemporary climatic factors. The rate of change of annual mean temperature, but not that of annual precipitation, also significantly contributed to the spatial pattern of plant endemic species richness. We found no significant relationship between topographic variation and endemic species richness, while temperature variability at multiple time scales was strongly correlated with the species richness pattern. Future work should consider the direction of climate change and incorporate higher-resolution data.  相似文献   

16.
整合闽清县的气象、地形、污染源等数据,综合运用分数偏差与参数估计最优化方法研究反照率、波文比及地表粗糙度3个地表参数设置对AERMOD模式预测结果的影响程度及趋势,并在地表参数率定的基础上建立县域尺度上的AERMOD模型.此外利用AERMOD模型模拟闽清县的SO_2污染现状并作出SO_2空间分布图,结合闽清县大气污染防治规划提出煤改天然气措施并进行情景模拟,以期为模型运用、大气环境评价及污染防控提供一定参考.  相似文献   

17.
研究了27个鹅掌楸交配组合种子饱满度、生活力、发芽力等性状的变异.结果表明:中国鹅掌楸、北美鹅掌楸、杂种鹅掌楸平均种子饱满度、平均种子生活力分别为9.00%、5.11%,17.57%、10.76%和29.44%、16.95%.鹅掌楸种子活力种间差异明显,变异趋势为:杂种鹅掌楸>北美鹅掌楸>中国鹅掌楸;同时,同一种源不同个体间种子活力差异明显;不同交配类型种子活力差异显著,控制授粉明显优于自由授粉.  相似文献   

18.
研究了松嫩草原羊草可燃物含水率的变化规律,结果表明,在枯死过程中,植物含水率呈下降趋势,10月末达到此期的最低值,在30%;在枯草期,植物含水率变化不显著,在10%波动,雨后羊草可燃物含水率升高,但经过7-8h就恢复到雨前水平。另外,可燃物含水率的变化、雨后可燃物含水率的变化与气象因子之间具有一定的相关关系。  相似文献   

19.
Carpenter SJ  Erickson JM  Holland FD 《Nature》2003,423(6935):70-74
Late Cretaceous sediments from the Western Interior of North America yield exceptionally well preserved fossils that serve as proxies for the rapidly changing climate preceding the Cretaceous/Tertiary boundary (about 67-65 Myr ago). Here we reconstruct the ontogenetic history of a Maastrichtian-age fish, Vorhisia vulpes, by using the carbon, oxygen and strontium isotope ratios of four aragonite otoliths collected from the Fox Hills Formation of South Dakota. Individuals of V. vulpes spawned in brackish water (about 70-80% seawater) and during their first year migrated to open marine waters of the Western Interior Seaway, where they remained for 3 years before returning to the estuary, presumably to spawn and die. The mean delta(18)O from the marine growth phase of V. vulpes yields a seawater temperature of 18 degrees C, which is consistent with leaf physiognomy and general-circulation-model temperature estimates for the Western Interior during the latest Maastrichtian.  相似文献   

20.
 Analyzing the characteristics of the Tethyantectonic field, the authors think that the Tethyan tectonicfield underwent three evolutional stages: closing of Pa-leo-Tethys and rifting of Neo-Tethys from early Permian tolate Triassic, subduction of Neo-Tethys and collision betweenthe Indian plate and the Eurasia plate from Jurassic to earlyof low Tertiary, and collision between the Arab plate and theEurasia plate and the A-type subduction of Indian plate fromlate of low Tertiary to the present. Combining the evolutionof the Tethyan orogenic belt with the characteristics of theNorthern Margin basin, it is suggested that the sedimentaryand tectonic characteristics and types of the Northern Mar-gin basin are controlled by the formation and evolution ofthe Tethyan orogenic belt and the ingression of Tethys. Theevolution of Northern Margin basin can be divided into threedevelopment stages: back-arc foreland basin from late Per-mian to Triassic, the back-arc fault subsidence and depres-sion from Jurassic to the early of low Tertiary, and the reac-tive foreland basin from the late of low Tertiary to the pre-sent. The Northern Margin basin in the Tethyan tectonicfield is an important region for natural gas accumulation,and the Tarim Basin is a part of this region.  相似文献   

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