全文获取类型
收费全文 | 1387篇 |
免费 | 488篇 |
国内免费 | 466篇 |
专业分类
测绘学 | 190篇 |
大气科学 | 112篇 |
地球物理 | 372篇 |
地质学 | 1182篇 |
海洋学 | 239篇 |
天文学 | 75篇 |
综合类 | 71篇 |
自然地理 | 100篇 |
出版年
2024年 | 10篇 |
2023年 | 30篇 |
2022年 | 50篇 |
2021年 | 78篇 |
2020年 | 103篇 |
2019年 | 94篇 |
2018年 | 68篇 |
2017年 | 98篇 |
2016年 | 102篇 |
2015年 | 95篇 |
2014年 | 138篇 |
2013年 | 122篇 |
2012年 | 122篇 |
2011年 | 99篇 |
2010年 | 125篇 |
2009年 | 123篇 |
2008年 | 75篇 |
2007年 | 92篇 |
2006年 | 94篇 |
2005年 | 71篇 |
2004年 | 70篇 |
2003年 | 75篇 |
2002年 | 58篇 |
2001年 | 55篇 |
2000年 | 49篇 |
1999年 | 49篇 |
1998年 | 29篇 |
1997年 | 41篇 |
1996年 | 24篇 |
1995年 | 27篇 |
1994年 | 34篇 |
1993年 | 17篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有2341条查询结果,搜索用时 15 毫秒
101.
102.
孵漂石地层大口径钻头与钻进工艺的选择 总被引:2,自引:1,他引:2
根据工程实例,通过钻头和钻进工艺的对比试验,得出了利用大直径滚刀钻头,在致密卵漂石地层施工中大口径桩孔,能大幅度提高钻进效率。 相似文献
103.
For data treatment of phytoplankton countings in the Lower Rhine the specific biovolume was calculated. The used computer-aided method is described, and the correlation between phytoplankton biomass, cell number and chlorophyll a is presented. 相似文献
104.
Nicholas P. Wallerstein Carlos V. Alonso Sean J. Bennett Colin R. Thorne 《地球表面变化过程与地形》2001,26(12):1265-1283
This paper presents the results of a movable‐boundary, distorted, Froude‐scaled hydraulic model based on Abiaca Creek, a sand‐bedded channel in northern Mississippi. The model was used to examine the geomorphic and hydraulic impact of simplified large woody debris (LWD) elements. The theory of physical scale models is discussed and the method used to construct the LWD test channel is developed. The channel model had bed and banks moulded from 0·8 mm sand, and flow conditions were just below the threshold of motion so that any sediment transport and channel adjustment were the result of the debris element. Dimensions and positions of LWD elements were determined using a debris jam classification model. Elements were attached to a dynamometer to measure element drag forces, and channel adjustment was determined through detailed topographic surveys. The fluid drag force on the elements decreased asymptotically over time as the channel boundary eroded around the elements due to locally increased boundary shear stress. Total time for geomorphic adjustment computed for the prototype channel at the Q2 discharge (discharge occurring once every two years on average) was as short as 45 hours. The size, depth and position of scour holes, bank erosion and bars created by flow acceleration past the elements were found to be related to element length and position within the channel cross‐section. Morphologies created by each debris element in the model channel were comparable with similar jams observed in the prototype channel. Published in 2001 John Wiley & Sons, Ltd. 相似文献
105.
以往整治滑坡,较多地使用大口径挖孔桩或钻孔灌注抗滑桩,周期长、成本高。川地208队在治理重庆制药五厂已处于危急态势的滑坡中,采用“天平式”控制、勘治结合、快速抢险,用三排小径密抗桩(300mm口径)整治,取得明显成效。实践表明:浅层滑坡采用较小口径的密抗桩,并辅以排水,能达到事半功倍的效果。 相似文献
106.
107.
108.
不同类型的射电望远镜阵的分辨率差异甚大,用它们的数据进行图像处理后所得到的源结构的尺度也不一样。为了得到中间尺度的结构信息,有时我们需要把不同类型的射电望远镜阵的观测数据结合起来再进行图像处理。本文阐述我们把不同类型阵的数据结合时所用的方法;也给出我们使用的方法所获得的结果的实际例子。 相似文献
109.
110.
Pristine river corridors were characterized by island and floodplain development driven by the inter‐play of flows, sediments and woody vegetation. Here we explore these relationships within topographically controlled settings within the upper, middle and lower reaches of a large, semi‐natural alpine to mediterranean river. These reaches have expanding or contracting valley floors within which we show that there are more or less predictable patterns of stream power and rates of vegetation growth, reflecting water availability during dry periods and also the availability of sand and finer sediment. We relate these to the pattern of island distribution that is repeated within the three reaches and is indicative of the engineering role of riparian trees. Islands are shown to develop within thresholds defined by stream power, rates of woody vegetation growth and rates of sedimentation, and to develop most quickly where riparian species include those capable of sprouting from driftwood. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献