全文获取类型
收费全文 | 858篇 |
免费 | 107篇 |
国内免费 | 132篇 |
专业分类
测绘学 | 150篇 |
大气科学 | 59篇 |
地球物理 | 143篇 |
地质学 | 551篇 |
海洋学 | 48篇 |
天文学 | 7篇 |
综合类 | 57篇 |
自然地理 | 82篇 |
出版年
2024年 | 5篇 |
2023年 | 7篇 |
2022年 | 13篇 |
2021年 | 21篇 |
2020年 | 26篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 20篇 |
2016年 | 39篇 |
2015年 | 37篇 |
2014年 | 53篇 |
2013年 | 45篇 |
2012年 | 58篇 |
2011年 | 71篇 |
2010年 | 50篇 |
2009年 | 79篇 |
2008年 | 50篇 |
2007年 | 69篇 |
2006年 | 57篇 |
2005年 | 52篇 |
2004年 | 43篇 |
2003年 | 55篇 |
2002年 | 36篇 |
2001年 | 24篇 |
2000年 | 19篇 |
1999年 | 36篇 |
1998年 | 21篇 |
1997年 | 17篇 |
1996年 | 16篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
排序方式: 共有1097条查询结果,搜索用时 15 毫秒
1.
介绍试用1:33000比例尺航测资料,在JX-3解析测图仪上高倍放大航测1:1000比例尺地形图的成图方案和应采取的技术措施,运用 解析法模型绝对定向的原理,在全野布点时采用两种方案对照比较,进行理论和试验精度的分析,并给出试验结果。 相似文献
2.
雅砻江畔雅江县城区地质灾害特征及其防治对策 总被引:1,自引:0,他引:1
四川省雅江县城座落于雅砻江河畔。在城区0.84km^2范围内发育有城南滑坡,城区斜 地面变形、城东危岩和城北滑坡四大地质灾害单元,构成了较为罕见的雅江县城独特的地质灾害特征。论述了雅江县城稆种地质这为害的特征及危害性,并对各咱地质灾害单元按其轻重缓解提出相的防治措施和对策。 相似文献
3.
Field vibration mitigation by honeycomb WIB for pile foundations of a high-speed train viaduct 总被引:5,自引:0,他引:5
Environmental vibrations from recent high-speed trains are becoming a special concern in the civil and environmental engineering field since they can give detrimental effects to residents, sensitive equipments and high-tech production facilities in the vicinity of train tacks. Herein, aiming at the vibration mitigation for a specific high-tech industrial area, the low-frequency vibrations from a train viaduct are targeted over an anticipated range. A theoretically designed innovative countermeasure, called honeycomb wave impeding barrier (WIB) for a wave impeding barrier, is introduced and its effects are investigated by computer simulation. The present WIB is based on the wave dispersion phenomenon that can modulate the incoming wavelengths into the shorter wavelengths, creating an apparent wave cut-off characteristic in the wave field across WIB installation area. The shorter wavelengths are further impeded due to the impedance ratio of the WIB walls and in-fill materials and absorbed by the in-fills more. The three-dimensional FEM simulation demonstrates a dramatic reduction effect that is difficult to achieve by conventional measures. 相似文献
4.
5.
针对面要素几何匹配算法,提出反映距离、尺寸、方向、形状4种主要几何度量指标的多算子加权匹配方法,建立了质心距离、Hausdorff距离、面积重叠度、对称差、轮廓紧致度和正切空间的量化算子,对量化结果进行加权评分计算总相似度确定面要素匹配值。运用多版本实测数字线划图数据进行匹配实验,结果表明该方法匹配结果可靠,并且通过算子权重和匹配阈值的调节设置可以筛选受关注度量指标的高匹配结果。 相似文献
6.
Sanjeev Sharma Jagdish C. Kuniyal J. C. Sharma 《山地科学学报》2007,4(3):221-236
Mountain ecosystem,on the earth,has plenty of natural resources. In Himachal Pradesh all the rivers are snowfed and therefore rich in water resources. These resources have been supporting enough for the generation of electricity through introducing hydropower projects since the last decade. However,every developmental activity has its own negative impacts on the surrounding environment. Due to the fragile nature of topography and delicacy of ecology of the Himalaya,it results in lot of disturbances because of high degree of human interferences like construction of major hydropower projects. The increased extent of geological hazards,such as landslides,rock fall and soil erosion,have mainly due to alike developmental interventions in the natural ecosystem. So understanding and analysing such impacts of the hydropower projects have mainly been on the environment in various forms but natural hazards have been frequent ones. The present study,therefore,focuses mainly on the Parbati Stage Ⅱ (800 MW) and the Parbati Stage Ⅲ (520 MW) hydropower projects; both of which fall within the Kullu district of Himachal Pradesh. Based on the perception survey of the local communities,the existing land use pattern,status of total acquired land of the residents by hydropower projects,frequent natural hazards and resultant loss to the local communities due to upcoming construction of hydropower projects surrounding to the Parbati Stage Ⅱ and Ⅲ have been analysed in the paper. Also,the preventive measures to mitigate these adverse impacts have been suggested to strengthen these projects in eco-friendly manner in the mountain context. 相似文献
7.
8.
宽甸县处于新构造运动强烈上升区,境内峰峦叠嶂,山势陡峻,沟深谷狭,暴雨频繁,地质环境十分脆弱;加之森林大量砍伐,陡坡开荒严重,垦植指数过高,超载养蚕放牧,滥采乱挖猖獗,使生态环境遭到严重破坏,水土流失程度日益加剧。严重的水土流失,导致水库淤积,河道堵塞,土层变薄,地力下降,洪水泛滥,灾害频繁,给国民经济和社会发展造成巨大损失。本文阐述了宽甸山区水土流失的形成因素和危害现状,并因地制宜提出了水土流失灾害的防治对策 相似文献
9.
王生全 《地球科学与环境学报》2001,23(1):16-19
煤系介质条件作为构造形成和发育的的物质基础,必然影响断层的发育。以陕西下峪口煤矿2号煤层为对象,研究了煤层围岩介质参数与煤层小断层间的关系,确定了控制2号煤层小断层发育的4个主要因素,并据此建立了预测小断层发育程度的数学模型。 相似文献
10.
通过采用地面物探、钻探和井下巷探、钻探相结合的综合勘探方法,对鲁村井田深部进行了补充勘探,并对井田以往地质资料进行了重新对比分析,发现该井田-400~-1 300 m的埋深范围内不但存在以往认为已被剥蚀缺失的太原组上部地层,还保存了较完整的山西组,尤其是在该段地层中新发现了5个局部可采煤层,为井田增加了资源储量、延长了服务年限。填补了沂源煤田太原组上部和山西组含煤地层资料的空白。 相似文献