全文获取类型
收费全文 | 863篇 |
免费 | 197篇 |
国内免费 | 175篇 |
专业分类
测绘学 | 43篇 |
大气科学 | 191篇 |
地球物理 | 250篇 |
地质学 | 472篇 |
海洋学 | 48篇 |
天文学 | 14篇 |
综合类 | 97篇 |
自然地理 | 120篇 |
出版年
2024年 | 3篇 |
2023年 | 15篇 |
2022年 | 54篇 |
2021年 | 53篇 |
2020年 | 40篇 |
2019年 | 40篇 |
2018年 | 63篇 |
2017年 | 52篇 |
2016年 | 59篇 |
2015年 | 44篇 |
2014年 | 61篇 |
2013年 | 52篇 |
2012年 | 47篇 |
2011年 | 53篇 |
2010年 | 48篇 |
2009年 | 45篇 |
2008年 | 50篇 |
2007年 | 40篇 |
2006年 | 45篇 |
2005年 | 46篇 |
2004年 | 30篇 |
2003年 | 29篇 |
2002年 | 14篇 |
2001年 | 13篇 |
2000年 | 22篇 |
1999年 | 24篇 |
1998年 | 31篇 |
1997年 | 23篇 |
1996年 | 25篇 |
1995年 | 17篇 |
1994年 | 17篇 |
1993年 | 14篇 |
1992年 | 20篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 1篇 |
1986年 | 7篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有1235条查询结果,搜索用时 15 毫秒
921.
922.
Preface to the special issue on recent advances of deep structure,seismic anisotropy and seismotectonics in China 下载免费PDF全文
<正>A workshop on crustal structure and seismotectonics was held on the Chinese Teacher's Day,the September 10th of 2011,in the city Lanzhou,China.Scientists and graduate students from Chinese Academy of Sciences,China 相似文献
923.
为获得矿山深部开采和设计所需要的地应力基础资料,中国地质科学院地质力学研究所于2012—2013年在冀东地区滦县—乐亭大断裂附近开展了3个钻孔水压致裂的应力测量工作,钻孔孔深为500—1 000 m.地应力测量结果初步揭示了研究区地壳浅表层现今地应力的分布规律.实测结果表明:现今研究区域应力场优势方向为NW70°;3个测点的最大剪切应力与平均应力的比值um范围为0.24—0.48,平均值分别为0.30,0.40和0.30,均未达到地壳应力摩擦极限状态(um=0.6)的水平,而唐山大地震后不久研究区浅层获得的um则较大,个别点大于0.6,平均值为0.44,表明唐山大地震后研究区应力积累程度较低,应力释放较为充分;依据断层摩擦准则及拜尔利定律可知,研究区发生较大地震活动的危险性较低. 相似文献
924.
925.
926.
以百合品种“西伯利亚”为材料,研究了低温和赤霉素(GA3)处理对百合鳞茎休眠解除过程中形态和碳水化合物含量的影响,以及不同温度条件下鳞茎不同部位内源GA3含量的变化。结果表明:低温(5℃)和0.15 g·L-1 GA3处理35 d时芽长与鳞茎高比值为67.954%,芽生长点位于鳞茎直立高度约2/3处,解除休眠所需天数最少;鳞茎在0~14 d时淀粉降解最快,第35天时可溶性总糖和还原糖含量最高。低温处理的内层鳞片和芽内源GA3含量变化显著,且温度越低,变化越明显。低温条件下内层鳞片和芽的内源GA3含量较高,上升趋势最为明显;而外层鳞片和根的GA3含量水平较低,变化趋势较小。可见,顶芽和内层鳞片可能为整个鳞茎休眠解除活动的中心。 相似文献
927.
应急避难场所建设适宜与否,能否在灾时和灾后及时发挥应急避难功能,将直接决定居民的生命安全和财产损失情况。基于抗震防灾规划标准,本文以石家庄为例,从有效性、可达性、安全性三个层面构建了石家庄市应急避难场所适宜性评价指标体系。以GIS软件为数据处理平台,运用熵值权重法结合灰色关联分析的评价模型,对石家庄市应急避难场所进行适宜性评价。结果表明:石家庄市应急避难场所中有3处达到适宜等级,2处达到一般适宜等级,4处是不适宜等级。最后依据评价结果提出建设性建议。结果可检验石家庄已建成应急避难场所的布局合理性,为石家庄市新增避难场所的规划建设提供建议。 相似文献
928.
929.
The Eighth International Symposium on Permafrost Engineering was held in Xi’an,China,October 2009.The major topics discussed in the symposium included:permafrost engineering (involving design,construction and evaluation);mitigation of frost hazards in the regions affected by seasonally frozen ground;properties of frozen soils,model development and their applications;frost hazards and periglacial environments in mountain and plateau regions;climatic,environmental and cryospheric changes;and permafrost hydrology,cold regions water resources and land uses.The papers submitted to the symposium and lectures during the meeting represented some new developments of research on cold region engineering and environment.Here we summarized the works of the symposium in topics including:Permafrost engineering;General geocryology;Properties of frozen soils:model development and their applications;And climatic,environmental and cryospheric changes.During the symposium,the attendees pointed out that future studies should pay more attention to theoretical study and engineering mechanism study,and also on interaction between climate change and cold region environments and their engineering affects. 相似文献
930.
Since the implementation of the economic reform and opening up policy in 1978,China has miraculously created long-term high-speed economic growth,but has also had to face the problem of excessive consumption of resources as well as an intensification of en-vironmental pollution.As a result,China is now facing a slowdown in development.China must maintain a certain speed of development to realize its goal of being a powerful nation,and becoming a developed country by 2050.To this end,China is facing a transformation of its economic development.There is a need to agree on an expected economic growth rate,along with the corresponding development modes or means of regulation in the medium-and long-term periods.This study developed a systematic-dynamic model to simulate the cou-pling relationship between economic growth,development modes,and the environmental supply system,and explored the possible options for future economic growth as well as the resource use and environmental protection requirements (the main factors).The results showed that to achieve the development goal of becoming a developed country by 2050,while maintaining a good ecological environment,the suitable growth rate for China's econ-omy is 3.8%-6.3%.Within this range,a growth rate of 3.8%-4.4% was found to be relatively safe,while a growth rate of 4.4%-6.3% required further technical progress.This study pro-vides an early warning in regard to China's environmental and development status.The study was a response to the "Future Earth" framework document and,in terms of development speed,it developed a theoretical system for the determination of resource and environmental carrying capacity (RECC). 相似文献