全文获取类型
收费全文 | 370篇 |
免费 | 78篇 |
国内免费 | 71篇 |
专业分类
测绘学 | 26篇 |
大气科学 | 53篇 |
地球物理 | 88篇 |
地质学 | 212篇 |
海洋学 | 34篇 |
天文学 | 22篇 |
综合类 | 23篇 |
自然地理 | 61篇 |
出版年
2023年 | 3篇 |
2022年 | 15篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 17篇 |
2018年 | 14篇 |
2017年 | 11篇 |
2016年 | 20篇 |
2015年 | 17篇 |
2014年 | 19篇 |
2013年 | 34篇 |
2012年 | 21篇 |
2011年 | 39篇 |
2010年 | 27篇 |
2009年 | 27篇 |
2008年 | 21篇 |
2007年 | 23篇 |
2006年 | 26篇 |
2005年 | 19篇 |
2004年 | 14篇 |
2003年 | 15篇 |
2002年 | 22篇 |
2001年 | 17篇 |
2000年 | 13篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有519条查询结果,搜索用时 31 毫秒
51.
准中4区块侏罗系头屯河组滩坝及风暴沉积特征 总被引:1,自引:1,他引:0
在准噶尔盆地中部(简称准中)4区块侏罗系岩心观察的基础上,考虑粒度分析、薄片镜下观察及古气候恢复成果,认为该区头屯河组沉积时期发育滨浅湖滩坝沉积;以典型风暴沉积构造的识别为基础,提出一种与滩坝相伴生出现的新的风暴岩类型——滨浅湖风暴岩,并建立理想垂向序列模型,自下至上依次为:递变、块状层段(Sa),平行层段、冲洗交错层段(Sb),波状层段(Sc);断续纹层段(Sd)和滨浅湖泥岩段(Se).该类风暴岩发育在正常浪基面之上的滨浅湖地区,与半深湖风暴岩相比,更易遭受后期波浪改造而难以完整保存;因其发育的平面位置不同,滨浅湖风暴岩序列顶底的沉积物可以是氧化色调的滨浅湖泥坪沉积物或是正常的滨浅湖滩坝沉积物.滨浅湖风暴岩的提出完善了滨浅湖滩坝沉积体系,为研究区古地理、古气候特征的恢复提供线索,为滩坝的成因和沉积环境研究提供思路,对准噶尔盆地隐蔽油气藏的勘探具有一定指导意义. 相似文献
52.
《Geoforum》2017
This paper uses a Swedish micro-dataset containing 2,696,909 hires during the period 2002–2006 to assess the impact of job-related mobility on plant-level performance. The analysis classifies new recruits according to their work experience and level of formal qualification, as well as by the region of origin and of destination. New hires are divided into graduates and experienced workers and between high- and low-educated. The results point towards the importance of acknowledging both the experience and the skills of new recruits. The greatest benefits are related to hiring new workers from outside the region where the plant is located. The analysis also stresses the importance of geography, with plants in metropolitan regions gaining the most from labour mobility, while the benefits of mobility for plants in smaller, more peripheral regions are more diverse and dependent on both the type and origin of new workers. 相似文献
53.
选用福建地震台网"十五"观测系统正式运行以来记录的台湾地区M≥4.0地震资料,以中国地震台网给出的震级为标准震级,进行了震级偏差统计分析,初步得出震级校正值。并分析了震级差异形成原因,为福建地震台网测定台湾地震震级偏差改正提供参考。 相似文献
54.
我国“十一五”期间的岩溶研究进展与重要活动 总被引:12,自引:11,他引:1
“十一五”期间,国际岩溶中心在我国桂林成立,岩溶研究在理论上与实践应用上取得了显著进展。理论上,运用地球系统科学的观点和现代自动化测试手段发展了岩溶动力学;新的学科生长点岩溶生态学不但揭示了西南岩溶生态系统的脆弱性、土壤质量变化与某些土壤营养元素形态的初步规律,而且选育了大量适合岩溶地区的名特优植物物种;全球变化研究探讨了岩溶水循环中溶解无机碳形式对全球碳汇的贡献,从多种气候替代指标深化了洞穴石笋的古环境记录研究;用新技术探索了岩溶地下水水质和水量的有效评价方法。应用上,形成的西南岩溶水、石漠化和水土流失调查区域性资料在国家目标和干旱找水重大社会需求中发挥重要作用,岩溶地区油气勘察形成典型地质模式,中国南方喀斯特自然遗产申报成功,岩溶塌陷监测与预警新技术成功用于工程建设区塌陷的防治。 相似文献
55.
56.
57.
东营凹陷古近系沙河街组碳酸盐岩的成因一直存在湖相与海相之争。沙四段碳酸盐岩呈厚薄不等的夹层赋于陆相碎屑岩中。本文对研究区代表性碳酸盐岩样品稀土元素地球化学特征的分析表明:东营凹陷古近系沙四段碳酸盐岩的∑LREE〉∑MREE〉∑HREE,MREE相对于HREE富集;不具备Ce/Ce*负异常特征;Y/Ho值为25.5~34.1,La/La*值为0.99~1.21;Y/Ho—La/La*呈负相关关系。所有这些特征均与湖相成因碳酸盐岩一致,沙四段碳酸盐岩的形成应为湖相成因。 相似文献
58.
59.
Within the confines of Earth Observation Scientific Knowledge and Technology Transfer in Hungary (EKAT) titled ESA PECS project we gained forum for utilization of our earth observation (EO) knowledge and possibility for further development of experiences. The project aims the horizontal preparation of Hungary for ESA membership – for a dynamically developing sphere in the common part of science, technology and business. For the efficient transfer and dissemination, we preconceived target groups and principles to reach main take-up points and to open new forums of information exchange. Nowadays, user-friendly service, complex supply and real-validation process all have great importance. Joining units of suitable data choice, entire ingestion–processing chains and ergonomic interfaces can only offer a timely and professional solution for the challenges of industry and business sectors. It has to be clearly seen, that information and communication technologies (ICT) and information control becomes a more and more significant part of EO services. 相似文献
60.
This research tests the casual link from political ideology to national greenhouse gas emissions by utilizing multinational panel data covering 98 countries during the period 1990–2016. Overall, the baseline results and robustness tests show a political divide on national greenhouse gas emissions, whereby compared to right-wing governments, left-wing governments are more likely to exhibit less carbon dioxide emissions. We further explore this topic from the perspectives of energy efficiency and education. Three-stage OLS regressions suggest that leftist parties increase energy efficiency and spend more on secondary education, which lead to less greenhouse gas emissions. We also introduce the interaction between political ideology and economic performance as well as globalization to test the moderating effects of economic performance and globalization. The study further looks into the interaction effects of political ideology and democracies on greenhouse gas emissions by dividing the whole sample into two sub-samples. The results indicate that the ideology effect on greenhouse gas emissions varies among countries with different economic performances or different degrees of political globalization, as well as between democracies and non-democracies. 相似文献