全文获取类型
收费全文 | 286篇 |
免费 | 34篇 |
国内免费 | 66篇 |
专业分类
测绘学 | 22篇 |
大气科学 | 55篇 |
地球物理 | 104篇 |
地质学 | 113篇 |
海洋学 | 55篇 |
天文学 | 5篇 |
综合类 | 10篇 |
自然地理 | 22篇 |
出版年
2022年 | 11篇 |
2021年 | 11篇 |
2020年 | 6篇 |
2019年 | 20篇 |
2018年 | 19篇 |
2017年 | 23篇 |
2016年 | 21篇 |
2015年 | 17篇 |
2014年 | 25篇 |
2013年 | 12篇 |
2012年 | 18篇 |
2011年 | 26篇 |
2010年 | 22篇 |
2009年 | 11篇 |
2008年 | 21篇 |
2007年 | 10篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 8篇 |
2002年 | 2篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1962年 | 1篇 |
1941年 | 1篇 |
排序方式: 共有386条查询结果,搜索用时 15 毫秒
381.
Stability analysis of the dam is important for disaster prevention and reduction. The dam's geometry plays an important role in understanding its stability. This study develops a rapid landslide dam geometry assessment method for both earthquake-induced and rainfall-induced landslide dams based on nine real cases collected in Chinese Taipei and 214 cases collected worldwide. For simplification purposes, a landslide dam is classified into triangular or trapezoidal. The rapid landslide dam geometry assessment method in this paper uses only satellite maps and the topographic maps to get landslide area, and then analyze the dam geometry. These maps are used to evaluate the area of the landslide and the slope of the river bed. Based on the evaluation information, the proposed method can calculate dam height, the length of the dam, and the angles of the dam in both upstream and downstream directions. These geometry parameters of a landslide dam provide important information for further dam stability analysis. The proposed methodology is applied to a real landslide dam case at Hsiaolin Village. The result shows that the proposed method can be used to assess the landslide dam geometry. 相似文献
382.
西藏甲玛超大型铜多金属矿床的钼资源量大于100万吨,辉钼矿是最主要的钼矿物。本文应用电感耦合等离子体质谱法(ICP-MS)分析了不同期次辉钼矿,研究其稀土元素和微量元素的地球化学特征,以指示成矿流体的来源与性质,探讨其成矿机制。结果表明,辉钼矿的稀土元素总量(39.34~168.1μg/g)与斑岩、矽卡岩的稀土元素总量相似,富集轻稀土,且从早到晚总量增加,指示流体源自于岩浆。辉钼矿具有明显的Eu、Ce负异常和Sm正异常,其中Eu负异常指示流体的还原性质;Cu、Pb、Zn等成矿元素含量较高,指示流体中成矿元素的富集。 相似文献
383.
正 Erhtsun is a small village about 22 km northwest of Kunming.It liesin the valley dissected by the Shalangho~2 flowing from southeast to northwest 相似文献
384.
385.
The impact of Global Positioning System data on the prediction of an extratropical cyclone: an observing system simulation experiment 总被引:1,自引:0,他引:1
In this paper, we report a series of observing system simulation experiments that we conducted to assess the potential impact of Global Positioning System/meteorology (GPS/MET) refractivity data on short-range numerical weather prediction. We first conducted a control experiment using the Penn State/NCAR mesoscale model MM5 at 90-km resolution on an extratropical cyclone known as the ERICA (Experiment on Rapidly Intensifying Cyclones over the Atlantic) IOP 4 storm. The results from the control experiment were then used to simulate GPS/MET refractivity observations with different spatial resolution and measurement characteristics. The simulated refractivity observations were assimilated into an 180-km model during a 6-h period, which was followed by a 48-h forecast integration. Key findings can be summarized as follows:
- • The assimilation of refractivity data at the 180-km resolution can recover important atmospheric structures in temperature and moisture fields both in the upper and lower troposphere, and, through the internal model dynamical processes, also the wind fields. The assimilation of refractivity data led to a considerably more accurate prediction of the cyclone.
- • Distributing the refractivity randomly in space and applying a line averaging did not alter the results significantly, while reducing the spatial resolution from 180 km to 360 km produced a moderately degraded result. Even at the 360-km resolution, the GPS-type refractivity data still have a notable positive impact on cyclone prediction.
- • Restricting the refractivity data to altitude 3 km and above considerably degraded its impact on cyclone prediction. This degradation was greater than the combined effects of distributing the refractivity data randomly, performing line averaging, and reducing the resolution to 360 km.
386.
为探究菲律宾蛤仔(Ruditapes philippinarum)筏式养殖模式可行性,在我国黄海北部首次开展了菲律宾蛤仔"斑马蛤2号"新品种的筏式与底播养殖模式对比试验。采用平均壳长为2.37 cm,平均全湿重为2.99 g规格的"斑马蛤2号"苗种为试验材料,对两种养殖方式的"斑马蛤2号"生长、存活、营养成分进行比较分析,结果表明,筏式养殖"斑马蛤2号"夏季(4-7月)壳长、壳宽、壳高、全湿重、软体重的相对生长速率分别比底播养殖"斑马蛤2号"快149.54%、100.61%、116.30%、152.25%、132.58%(P<0.05)。筏式养殖"斑马蛤2号"存活率为90%以上,显著高于底播养殖(P<0.05)。两种养殖方式的"斑马蛤2号"水分、灰分、粗蛋白、糖原、脂肪酸等营养成分季节变化规律基本一致。筏式养殖"斑马蛤2号"冬季糖原、单不饱和脂肪酸含量明显高于底播养殖"斑马蛤2号"(P<0.05)。研究表明,当年10月采用多层聚乙烯网笼按密度为150-200粒/层放养菲律宾蛤仔"斑马蛤2号"大规格苗种(平均壳长为2.37 cm,平均全湿重为2.99 g),可于翌年的4月、7月、10月收获平均壳长为3.03、3.36、3.51 cm的市场规格产品。筏式养殖模式具有存活率高的优点。"斑马蛤2号"筏式养殖模式试验的成功为蛤仔健康养殖提供了新途径。 相似文献