全文获取类型
收费全文 | 53篇 |
免费 | 7篇 |
国内免费 | 9篇 |
专业分类
大气科学 | 6篇 |
地球物理 | 2篇 |
地质学 | 7篇 |
海洋学 | 38篇 |
综合类 | 8篇 |
自然地理 | 8篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 4篇 |
2012年 | 4篇 |
2011年 | 6篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 3篇 |
2007年 | 6篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2002年 | 3篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
排序方式: 共有69条查询结果,搜索用时 31 毫秒
61.
从采自海南东寨港的红树林卤蕨(Acrostichum aureum Linn.)中分离得到的一株内生真菌Cladosporium perangustum MA-318,对其次级代谢产物进行了研究。利用反相硅胶柱层析、正相硅胶柱层析以及葡聚糖凝胶Sephadex LH-20柱层析等分离手段获得一个单体化合物。通过波谱数据分析(HRESIMS、1D NMR、2D NMR)鉴定该化合物为新的链烯酸酐,其结构为methyl(E)-3-(4-(2-((4-(but-1-en-1-yl)-2,5-dioxo-2,5-dihydrofuran-3-yl)methyl)butyl)-2,5-dioxo-2,5-dihydrofuran-3-yl)propanoate,命名为methylate cordyanhydride A。抗菌实验表明该化合物对藤黄微球菌(Micrococcus luteus)表现出一定的抑制作用。 相似文献
62.
【目的】黑木耳作为剑河县发展战略和特色农业,木耳的产量、质量与本县经济发展息息相关,本文旨在研究出剑河县黑木耳高产的气象条件指标及灾害性天气指标,以期为剑河县黑木耳的产业发展提供科学的气候依据。【方法】以黑木耳为试材,在剑河县气象局内建立黑木耳微型模拟观测站,本文分析数据主要源于实验过程中木耳生育期、产量、同期气象要素值等资料。【结论】当平均温度在13.2~17.1℃间,气温越高,耳芽生长周期越短,林下温差刺激、光照刺激较坝区小,出芽率低于坝区,但林下耳片质量更好。木耳最适宜生长温度条件为:气温22.0~22.5℃,草温24.4~31.1℃;适宜湿度条件:相对湿度>70%。当日最高气温>32.1℃、相对湿度≥69%,会产生高温灾害,易造成木耳流耳,气温日较差越小,流耳情况越严重;生长环境温度低于10℃时,抑制耳片生长。 相似文献
63.
BarnaBahadur THAPA Saroj PANTHI Rajesh KumarRAI UttamBabu SHRESTHA Achyut ARYAL Sabina SHRESTHA Bhushan SHRESTHA 《山地科学学报》2014,11(2):555-562
Yarsagumba (Ophiocordyceps sinensis), an endemic species to the Himalayas and Tibetan Plateau, is one of the most valuable medicinal mushrooms in the world. In Nepal, it is distributed largely in isolated patches of alpine grasslands of 3,000-5,000 m elevation. Although it is reported from 27 northernmost districts of Nepal, the local distribution pattern of this species is largely unknown. Furthermore, the collection system and local management regime of this species are not well documented. We conducted a field survey at Dhorpatan Hunting Reserve (DHR) among the different stakeholders in January-June 2012 to assess collection sites, patterns and trends and to understand the management regime. We estimated that about 75 kg of Yarsagumba is collected every year from DHR and the amount has been declining since 2008. To manage the resource, locals have initiated regulating the collection by issuing permits, taxing to the collectors, and monitoring the activities of harvesters with the help of park authorities. The revenue generated at local level from the permits has been used for community developmental activities. 相似文献
64.
Uttam Babu Shrestha Sujata Shrestha Shivaraj Ghimire Kamal Nepali Bharat Babu Shrestha 《社会与自然资源》2014,27(12):1242-1256
The Chinese caterpillar fungus is famous for its high market value, unusual life history, and significant medicinal uses. It is harvested by very poor communities and sold for an extraordinarily high price. Most of the studies on this species are focused on therapeutic uses, chemical analyses, ecology, and trade. However, harvesting techniques and intensity of the harvests remain undocumented. We document harvesting techniques, trends of harvest, and perceptions of the Chinese caterpillar fungus harvesters in Dolpa, Nepal, based on surveys, focus-group discussions, and direct observations. Along with increasing market value, intensity of the harvest has been increasing. The Chinese caterpillar fungus harvest has now become the second most important livelihood strategy for the local communities, after agriculture. Reported per-capita harvest based on the first day of collection has declined over the last 4 years, apparently because of the decline in the stock and the increasing number of harvesters. 相似文献
65.
《African Journal of Marine Science》2013,35(2):221-229
Kelp forests are believed to host a large biomass of epiphytic fauna and flora, including diatoms, which constitute the base of aquatic food webs and play an important role in the transfer of energy to higher trophic levels. Epiphytic diatom assemblages associated with two common species of South African kelps, Ecklonia maxima and Laminaria pallida, were investigated in this study. Primary blades of adult and juvenile thalli of both kelp species were sampled at False Bay in July 2017 and analysed using scanning electron microscopy. Our findings showed that both kelp species hosted relatively low densities of diatoms (ranging from 7 [SD 5] cells mm?2 on adult specimens of L. pallida to 43 [SD 66] cells mm?2 on blades of juvenile E. maxima), with Amphora and Gomphoseptatum reaching the highest absolute abundances. Although non-metric multidimensional scaling showed overlapping and largely scattered sample sets, a significant relationship between the diatom communities and the species and age of the host macroalga was detected by two-way PERMANOVA. In general, more abundant and diverse diatom communities were observed on juvenile thalli than on adult thalli, with species belonging to Navicula and Rhoicosphenia contributing significantly to the observed dissimilarity. Due to a significant interaction between species and age effects, however, the overall ability of kelp species, their age, and their interaction to explain the variation in diatom community structure was limited. We suggest that the low densities of epiphytic diatoms were directly related to the sloughing of epithelial cells observed in both kelp species. We further speculate that on such unstable substrata some diatom taxa might adapt to an endophytic life to avoid the antifouling mechanisms developed by their hosts. 相似文献
66.
在对低温型食用菌生活条件和三明市低温型食用菌气候资源分析的基础上,确定了三明市低温型食用菌的气候指标,并建立气候模式.根据气候模式、地理信息系统、经济效益及交通状况等,综合评价了三明市低温型食用菌的资源状况,并以此为依据,利用GIS软件将三明市分为4个栽培区,即经济效益较低区、适宜栽培区、最适宜发展区和反季节栽培区. 相似文献
67.
海绵来源真菌Aspergillus sp BH4次级代谢产物的初步研究 总被引:1,自引:0,他引:1
研究1株来源于海绵的真菌Aspergillus sp BH4的次级代谢产物,该菌的发酵产物具有细胞毒活性。采用硅胶柱色谱、制备薄层色谱及重结晶方法,对其活性组分一乙酸乙酯提取物的化学成分进行分离纯化,结合文献及NMR,MS波谱数据确定了4个单体化合物的结构。 相似文献
68.
鸭毛藻内生真菌Hypocreales sp.的化学成分研究 总被引:2,自引:0,他引:2
从采自大连近海的红藻鸭毛藻(Symphyocladia latiuscula)中分离到一株肉座菌目真菌(Hypocreales sp.),对其发酵代谢产物的化学成分进行了研究。利用正相硅胶柱层析、葡聚糖凝胶Sephadex LH-20柱层析、制备薄层层析(PTLC)以及重结晶等分离手段,并通过一维、二维核磁共振技术、质谱技术等从该菌发酵液中分离鉴定了10个化舍物:双酚A(1);邻羟基苯甲酸(2);吲哚甲酸(3);吲哚乙酸(4);N-乙酰色胺(5);(22E,24R)-麦角甾-7,9,22三烯-3β-醇(6);过氧化麦角甾醇(7);(22E,24R)-5α,6α-环氧麦角甾-8,22-二烯-3β,7α-二醇(8);(22E,24R)-麦角甾-7,22-二烯-6β-甲氧基-3β,5α-二醇(9);啤酒甾醇(10)。这些化合物均为首次从该菌中分离得到,其中化合物1为首次作为天然产物分离得到。 相似文献
69.