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排序方式: 共有313条查询结果,搜索用时 15 毫秒
71.
工业测量中两测角装置间起始方向线的定向方法 总被引:5,自引:0,他引:5
分析了用于工业测量中的6种定向方法,这些方法或可直接应用,或可为仪器制造厂家参考。提出了这些方法的操作步骤,指出了使用常规测角仪器在工业测量时应注意的一些技术细节。 相似文献
72.
脾脏肿瘤的CT表现及鉴别诊断 总被引:5,自引:0,他引:5
目的:探讨脾脏肿瘤的CT表面及其诊断价值。材料与方法:搜集22例经病理和临床证实的脾脏肿瘤的CT资料,包括脾血管瘤2例,脾淋巴这瘤1例,脾错构瘤1例,恶性淋巴脾侵润4例,脾转移瘤14例,均行平扫加强化,对其CT表现进行回顾性分析。结果CT对脾脏肿瘤检出率高,对病变大小,形态,密度及脾周围组织器官的显示较其它影像学检查更准确。结论 CT可作为首选的影像学检查手段,对其定性诊断有较高价值。 相似文献
73.
Tourism is often considered as one of the dynamic conservation and adaptive management approaches in Agricultural Heritage Sites. It has been over 15 years since the GIAHS programme was initiated in China, and tourism developed quickly in the Agricultural Heritage Sites, to some extent because many researchers consider tourism as a significant engine of the local economy. However, this is contrary to the original intention of agricultural heritage tourism as it was proposed in the first place. Apparently, there are some overt problems during the tourism development process, which are mainly as follows: Some threats to Agricultural Heritage Systems are ubiquitous; The tourism development mode in Agricultural Heritage Sites is questionable; Community involvement is difficult to implement; And the negative environmental impacts are easy to overlook. Under the context of global development, the UNWTO sustainable tourism criteria provide some guidance for agricultural heritage tourism. Based on the Global Sustainable Tourism Criteria, combined with previous survey experiences and related researches, this paper analyzes the tourism sustainability of all the 15 GIAHS sites in China, and explores the current sustainable tourism development level. On this basis, an agricultural heritage sustainable tourism development framework was built in an attempt to find the road to sustainability for agricultural heritage tourism. The framework in the global and local contexts is trying to connect all the important elements related to agricultural heritage tourism according to the UNWTO sustainable tourism criteria. 相似文献
74.
Based on the basic selection criteria of Globally Important Agricultural Heritage Systems (GIAHS) and food and livelihood security research trends, this paper established an evaluation framework and indicator system for food and livelihood security in GIAHS and selected the first GIAHS site in the Qinghai-Tibet Plateau as a case for empirical evaluation. The results demonstrate that the food and livelihood security of farmers at this site was at a medium level, with an average evaluation value of 2.91, which still lagged behind the level of better food and livelihood security. Specifically, the average values of farmers’ evaluation of food security and livelihood security were 1.43 and 1.48, respectively, which show that farmers’ food security in the study area was at a medium level and that of livelihood security was relatively good. Simultaneously, the more simple a farmers’ economic activities (i.e., agriculture-oriented economic activities or non-agriculture-oriented economic activities), the worse their food and livelihood security; while the more diversified the economic activities (i.e., engaged in part-time economic activities), the better the food and livelihood security. 相似文献
75.
Agricultural biodiversity has a high importance in social-cultural, economic, and environmental aspects, and can help in adapting to and withstanding climate change. Conserving the GIAHS sites and the important components within them can help conserve the agricultural biodiversity and traditional agricultural culture of the whole country. This study considered Ifugao Rice Terraces, Dong’s Rice-Fish-Duck System, and Hani Rice Terraces System as three examples which show that traditional culture can be used to protect agricultural biodiversity, while as a carrier of traditional culture, agricultural biodiversity also conveys and protects the traditional culture of the nation. According to the analyses, through several years of efforts, the status of agricultural biodiversity and traditional culture in them has improved. Then, to further promote agricultural biodiversity conservation and traditional culture protection, several suggestions are made, such as establishing community seed banks; documenting and preserving traditional farming methods, techniques, and tools and developing participatory activities which encourage more farmers to participate in the protection work. 相似文献
76.
77.
本利用山东,江苏省地震台网的资料,对苍山5.2级地震前沂沭带南段地震活动性参 的变化特征进行了分析研究。发现苍山5.2级地震前沂沭带南段3、4级地震活动增强,应变能释放速率加速,地震波速比的时空变化,震前出现明显的低值异常时段和低值异常区。据比异常变化曾在震前提出过预报意见。 相似文献
78.
大别山北麓侏罗系大理岩砾石的碳—氧同位素组成及地质意义 总被引:16,自引:2,他引:14
在大别山北麓、合肥盆地南缘侏罗系三尖铺组和凤凰台组地层中含有大理岩砾石, 属山麓冲积扇环境沉积。它们的δ13 C数值范围为- 1.7‰~1.3‰, 大多数近于零值, 它们的δ18O数值从6.5‰~23.0‰。大别地块佛子岭群大理岩的δ13C数值为- 2.0‰~- 2.5‰, δ18O数值范围从6.3‰~13.1‰。大别地块高压和超高压变质岩带的大理岩的δ13 C数值为1‰~6‰,δ18O数值为5‰~23‰。碳同位素组成的明显差别表明现今大别地块佛子岭群和高压、超高压变质岩不是合肥盆地南缘侏罗系大理岩砾石的来源区。由于δ13C的数值不随δ18O值的降低而变化, 且分布在一个狭窄的范围, 合肥盆地南缘侏罗系大理岩砾石的碳同位素组成代表了它的原岩在沉积时海水的同位素记录。 相似文献
79.
采用叠加、互相关、插值拟合等方法对祁连山气枪主动源台网数据进行处理,针对2016年1月21日青海门源6.4级地震前后气枪激发地震P波、S波震相的走时变化特征进行了分析,结果表明,地震前约6个月时,震中附近3个台站的相对走时出现下降变化(走时减少),至震前约3个月时低值异常恢复正常,之后再次出现走时下降变化,地震即发生于走时变化恢复过程中。S波走时变化最大下降幅度达18ms,震后走时变化逐渐恢复正常,且3个台站变化趋势较为一致,其中,距震中最近的台站的S波走时变化最明显(ZDY38台),较远台站的走时变化幅度较小,其变化特征与震源区位置有关。走时缩短意味着速度增加,可能与区域应力积累间存在一定的关系。 相似文献