排序方式： 共有47条查询结果，搜索用时 15 毫秒
1.
研究了半枝莲Scutellaria barbata D.Don的化学成分。利用硅胶色谱、Sephadex LH-20凝胶色谱、HPLC等手段对化学成分进行分离纯化;通过理化性质、波谱分析方法结合文献对照,鉴定了化合物的结构。从半枝莲甲醇提取物中,共分离鉴定了10个单体化合物:齐墩果酸(1)、熊果酸(2)、反式-4-甲基肉桂酸(3)、金色酰胺醇酯(4)、对羟基苯甲醛(5)、对羟基苯乙酮(6)、5-羟基-7,3′,4′,5′-四甲氧基黄酮(7)、芹菜素(8)、5,7,4′-三羟基-8-甲氧基黄酮(9)、5,7,4′-三羟基-6-甲氧基黄酮(10)。化合物1、3、7为首次从该植物中分离得到。 相似文献
2.
建立药用耐盐植物盐地碱蓬(Suaeda salsa)的HPLC指纹图谱。运用DAD-Agilent 1100高效液相色谱仪,色谱条件:Agilent Zorbax XDB C18柱(4.6 mm×250 mm;5.0μm)色谱柱,1.0 mL.min-1流速,320 nm检测波长,360 nm参比波长,10μL进样量,30℃柱温,乙腈(A)-0.1%磷酸水(B)梯度洗脱。建立了盐地碱蓬的HPLC指纹图谱,包含16个共有峰,指纹图谱特征明显,化学信息完整。方法的系统适应性测定结果符合指纹图谱的技术规范。结论:首次建立的盐地碱蓬HPLC参考指纹图谱可用于盐地碱蓬的快速真伪鉴别。 相似文献
3.
鼎湖山常绿针阔叶混交林CO2通量估算 总被引：1，自引：0，他引：1
鼎湖山通量站是中国通量网络(ChinaFLUX)中4个森林站之一,采用开路涡度相关方法,对南亚热带常绿针阔叶混交林进行生态系统尺度的CO2通量长期定位观测．利用2003,2004年2整年观测资料,分析该生态系统CO2通量时间变化特征及其受环境因子的制约关系．通过坐标转换、WPL订正和质量控制后,发现本通量站存在明显的夜间泄漏问题,因此采用Michaelis- Menten模型,利用白天(PAR>1．0μmol-1 Photons·m-2·s-1)湍流充分条件-F(u*>0．2 m·s-1)的通量资料,逐月拟合净生态系统CO2交换NEE对光合有效辐射PAR的响应,利用拟合Michaelis-Menten方程得到的生态系统呼吸Reco,建立Reco与5 cm土壤温度的指数关系,借此反演夜间呼吸．主要结论包括:(i)逐月拟合的光能利用效率a平均为0．0027(±0．0011)mgCO2·μmol-1 Photons,最大光合速率Amax平均为1．102(±0．288)mgCO2·m-2·s-1,a与Amax季节性变化规律均不明显,表明林内旱季没有明显的缺水和低温胁迫存在,这与南亚热带常绿混交林叶面积指数(LAI)季节性变化较小的特点是一致的．（ii）生态系统呼吸月总量平均为95.3（±21．1）gC·mm-2month-1，约占生态系统总初级生产力GPP的68％．NEE月总量平均为-43．2（±29．6）gC·m-2·month-1，大部分月份NEE为负号，表明该生态系统全年均具有较强的碳汇功能．估算得到2003，2004年NEE总量分别为-563，-441．2gC·m-2·a-1，占GPP的32％． 相似文献
4.
The paper introduces the tectonic background,focal mechanism and distribution of aftershock of the Wenchuan earthquake on May 12,2008. The earthquake is considered to be the result of long-term interaction between the eastward movement of the Bayan Har Block and the Sichuan Basin. Most of the earthquake energy was released in an area (the seismic source body) 330km long,52km wide and 20km deep over 100s. Energy release in the source body was extremely uneven,and strong ground motion in the epicenter area shows obvious asymmetrical character in the time and space scale. The high-intensity area is distributed along the source body,and the intensity distribution bears an obvious anomalous characteristic. The investigation results indicate that more than 90 percent of casualties caused by this earthquake were in the areas of intensity IX or above. Houses,schools and hospitals etc. suffered serious damage. Lifelines such as transportation,water conservation etc. also suffered significant damage. Besides,earthquake-triggered avalanches,landslides,mud-rock flows and so on were extremely serious. The tremendous earthquake disaster highlighted the deficiencies in disaster prevention and mitigation management,scientific earthquake research,technology and application of earthquake disaster prevention,and publicity of earthquake preparedness and disaster reduction. 相似文献
5.
The temporal and spatial distribution characteristics of earthquakes in the Ordos block are studied by using historical earthquake data,instrument data of the regional seismic network around the Ordos block and the historical felt earthquake data,and the relationship between seismicity in the Ordos block and seismicity around the Ordos block is discussed. The result shows that the Ordos block is a typical moderate-strong earthquake active region where many M_S≥5.0 destructive earthquakes have occurred. The temporal and spatial distribution of earthquakes in the Ordos block is asymmetrical. The temporal distribution of earthquakes shows a periodic characteristic and the activity of earthquakes in the southeastern Ordos block is higher than in the northwest Ordos block. The M_S≥5.0 moderate size earthquakes in the Ordos block are controlled by the M_S≥6.0 earthquake around the Ordos block. 相似文献
6.
The M8.0 Wenchuan earthquake occurred on the Longmenshan fault zone. Based on field investigation of the surface rupture and focal mechanism study of the aftershocks, we discuss the geological relationship of the main, secondary and triggered ruptures. The main rupture is about 200km long and can be divided into the south part and the north part. The south part consists of two parallel fault zones characterized by reverse faulting, with several parallel secondary ruptures on the hanging wall of the main fault, and the north part is a single main fault zone characterized by lateral strike-slip and reverse faulting. Compared to a 300km long aftershock distribution, the surface rupture only occupies 200km, and the remaining 100km on the northeast of the main rupture was triggered by aftershocks. Study on the ruptures of this earthquake will be useful for studying the earthquake risk evolution on the Longmenshan fault system. 相似文献
7.
Leaf carbon content(LCC) is widely used as an important parameter in estimating ecosystem carbon(C) storage,as well as for investigating the adaptation strategies of vegetation to their environment at a large scale.In this study,we used a dataset collected from forests(5119 plots) and shrublands(2564 plots) in China,2011–2015.The plots were sampled following a consistent protocol,and we used the data to explore the spatial patterns of LCC at three scales:plot scale,eco-region scale(n = 24),and eco-region scale(n = 8).The average LCC of forests and shrublands combined was 45.3%,with the LCC of forests(45.5%) being slightly higher than that of shrublands(44.9%).Forest LCC ranged from 40.2% to 51.2% throughout the 24 eco-regions,while that of shrublands ranged from 35% to 50.1%.Forest LCC decreased with increasing latitude and longitude,whereas shrubland LCC decreased with increasing latitude,but increased with increasing longitude.The LCC increased,to some extent,with increasing temperature and precipitation.These results demonstrate the spatial patterns of LCC in the forests and shrublands at different scales based on field-measured data,providing a reference(or standard) for estimating carbon storage in vegetation at a regional scale. 相似文献
8.
应用静态箱／气象色谱法对南亚热带3种森林土壤地表CO2排放通量的季节动态及其对环境变化的响应规律进行了2年的连续观测,结果表明:季风常绿阔叶林、针阔叶混交林和马尾松针叶林(S L)CO2年排放总量分别为3942．2,3422．36和2163．02 gCO2．m-2·a-1,并且3种林分具有相同的季节性变化特征,排放高峰均出现在6～8月,这期间的土壤CO2排放量占全年排放总量的35．9％,38．1％和40．2％:不同森林土壤CO2排放过程对环境变化的响应有明显差异,具体体现在针叶林(PF)对温度变化的响应较阔叶林(BF)和混交林(MF)敏感,Q10值较大,而且CO2排放通量的季节变化幅度较大,表明结构单一的森林生态系统抗干扰能力较差;3种森林土壤CO2排放通量与土壤温度(Ts)、土壤含水量(Ms)和空气压力(Pa)均呈显著相关;但多元回归分析表明,空气压力对森林土壤CO2排放通量的影响并不显著;基于经验模型,以土壤5 cm处温度和土壤含水量两个指标可以分别说明阔叶林、混交林和针叶林土壤CO2排放通量变异的75．7％,77．8％和86．5％,该模型可以较好地描述受水分胁迫的土壤或干旱或半干旱土壤CO2的排放过程． 相似文献
9.
南亚热带森林土壤CO2排放的季节动态及其对环境变化的响应 总被引：1，自引：0，他引：1
应用静态箱／气象色谱法对南亚热带3种森林土壤地表CO2排放通量的季节动态及其对环境变化的响应规律进行了2年的连续观测,结果表明:季风常绿阔叶林、针阔叶混交林和马尾松针叶林(S+L)CO2年排放总量分别为3942．2,3422．36和2163．02 gCO2．m-2·a-1,并且3种林分具有相同的季节性变化特征,排放高峰均出现在6～8月,这期间的土壤CO2排放量占全年排放总量的35．9％,38．1％和40．2％:不同森林土壤CO2排放过程对环境变化的响应有明显差异,具体体现在针叶林(PF)对温度变化的响应较阔叶林(BF)和混交林(MF)敏感,Q10值较大,而且CO2排放通量的季节变化幅度较大,表明结构单一的森林生态系统抗干扰能力较差;3种森林土壤CO2排放通量与土壤温度(Ts)、土壤含水量(Ms)和空气压力(Pa)均呈显著相关;但多元回归分析表明,空气压力对森林土壤CO2排放通量的影响并不显著;基于经验模型,以土壤5 cm处温度和土壤含水量两个指标可以分别说明阔叶林、混交林和针叶林土壤CO2排放通量变异的75．7％,77．8％和86．5％,该模型可以较好地描述受水分胁迫的土壤或干旱或半干旱土壤CO2的排放过程． 相似文献
10.
By combining conventional grey correlation analysis,grey clustering method and grey forecasting methods with our multi-goal forecast thoughts and the techniques of grey time series processing,we develop six different grey earthquake forecast models in this paper,Using the record of major earthquakes in Japan from 1872 to 1995,we forecast future earthquakes in Japan.We develop an earthquake forecast model.By using the major earthquakes in Japan from 1872 to 1984,we forecast earthquakes from 1985 to 1995 and check the precision of the grey earthquake models.We find that the grey system theory can be applied to earthquake forecast.We introduce the above analysis methods and give a real example to evaluate and forecast.We also further discuss the problems of how to improve the precision of earthquake forecast and how to strengthen the forecast models in future research. 相似文献