全文获取类型
收费全文 | 1646篇 |
免费 | 365篇 |
国内免费 | 202篇 |
专业分类
测绘学 | 91篇 |
大气科学 | 238篇 |
地球物理 | 204篇 |
地质学 | 821篇 |
海洋学 | 249篇 |
天文学 | 7篇 |
综合类 | 226篇 |
自然地理 | 377篇 |
出版年
2024年 | 7篇 |
2023年 | 24篇 |
2022年 | 57篇 |
2021年 | 70篇 |
2020年 | 50篇 |
2019年 | 65篇 |
2018年 | 51篇 |
2017年 | 71篇 |
2016年 | 52篇 |
2015年 | 71篇 |
2014年 | 102篇 |
2013年 | 86篇 |
2012年 | 111篇 |
2011年 | 136篇 |
2010年 | 120篇 |
2009年 | 110篇 |
2008年 | 106篇 |
2007年 | 135篇 |
2006年 | 94篇 |
2005年 | 104篇 |
2004年 | 80篇 |
2003年 | 75篇 |
2002年 | 64篇 |
2001年 | 77篇 |
2000年 | 49篇 |
1999年 | 55篇 |
1998年 | 43篇 |
1997年 | 29篇 |
1996年 | 22篇 |
1995年 | 28篇 |
1994年 | 17篇 |
1993年 | 18篇 |
1992年 | 15篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有2213条查询结果,搜索用时 609 毫秒
311.
平度市国土资源局全面推进“双保”行动的探索 总被引:1,自引:1,他引:0
为应对国际金融危机,平度市国土资源局积极响应国土资源部在全国范围内部署开展的"保增长、保红线"双保行动,立足部门职能,扎实工作,加强和改善土地宏观调控新机制,有效保障扩大内需,保障重点项目用地,促进经济平稳较快发展。 相似文献
312.
313.
2006年,国土资源部确定在全国范围内开展基本农田保护示范区建设,济南市每年设立1 333.33 hm2(2万亩)市级基本农田保护示范区,进行田、水、路、林、村综合整治。通过科学选定项目、明确建设任务、完善建设标准,逐步实现基本农田建设标准化、基础工作规范化、保护责任社会化,促进农业增产、农村增效、农民增收。 相似文献
314.
HUANG Song 《地理学报》2010,20(3):357-374
The geological heritage protection and its development at home and abroad reflect the progress in the aspect from the single protection to the coordination between protection and exploitation. The geopark established by UNESCO has closely combined the protection of geological heritages with the promotion of sustainable development of local economy, which has become the best way to protect geological heritages. The geological heritages in Xinjiang, China, are characterized by their large quantity, rich variety and high grade. The complicated geologic-geomorphic environment in Xinjiang contributes to the creation of various geological heritage types and their spatial distribution, and at the same time makes them under control. The main types of the geological heritages in Xinjiang are the geologic- geomorphic landscapes and the water landscapes. The spatial distribution can be divided into five geological heritage districts: Altay, Junggar, Tianshan, Tarim and Kunlun-Altun, among which Tianshan and Kunlun-Altun are most important. Based on the first systematic investigation of the geological heritages in Xinjiang, it is confirmed that the insufficient coordination between protection and exploitation is the primary cause for the backward situation in the geological heritage protection. To solve the problem, this paper proposes 6 major protection steps—from determining the protection types, the protection forms, the protection modes, the protection grades, the protection sequences to determining the protection zones, brings forward the idea of optimal-selection which integrates geoparks with geological heritage protection areas and other protection areas as well as 5 corresponding modes, and makes a protection and exploitation reserve list for 209 important geological heritages in Xinjiang. 相似文献
315.
316.
317.
桂林甑皮岩洞穴遗址地下水示踪及污染来源分析 总被引:7,自引:7,他引:0
桂林甑皮岩遗址周围地带地下水中污染物的种类及来源复杂。为了查明地下水系统的结构特征,分析地下水的污染物运移路径和追溯污染源,采用在线高分辨率示踪技术与人工采样相结合的方法。选取荧光素钠和罗丹明B两种示踪剂,在桂林甑皮岩遗址周围进行了三次示踪试验。根据试验结果分析地下水流场,计算地下水平均流速。结果表明地下水流速在1.6~33.91 m/d,平均值为12.92 m/d。流场内岩溶以溶蚀裂隙为主,且裂隙发育呈网络式,存在西北向东南方向的主径流带,但大型岩溶管道存在的可能性小。三次示踪试验结果均显示,投放点所在的污染源区与遗址周围地下水存在水力联系,因此,遗址附近的居民小区、学校、原砖厂等污染源对遗址下部的地下水存在潜在污染,需更大程度地划分遗址的保护范围。特别是甑皮岩景区化粪池密闭情况较差,严重危害遗址环境,必须对化粪池进行防渗处理。 相似文献
318.
Assessment of effectiveness of nature reserves on the Tibetan Plateau based on net primary production and the large sample comparison method 总被引:4,自引:2,他引:2
Yili Zhang Zhongjun Hu Wei Qi Xue Wu Wanqi Bai Lanhui Li Mingjun Ding Linshan Liu Zhaofeng Wang Du Zheng 《地理学报(英文版)》2016,26(1):27-44
Twenty-one typical coupled large samples were chosen from areas within and surrounding nature reserves on the Tibetan Plateau using the large sample comparison method (LSCM). To evaluate the effectiveness of the nature reserves in protecting the ecological environment, the alpine grassland net primary production (NPP) of these coupled samples were compared and the differences between them before and after their establishment as protected areas were analyzed. The results showed that: (1) With respect to the alpine grassland NPP, the ecological and environmental conditions of most nature reserves were more fragile than those of the surrounding areas and also lower than the average values for the Tibetan Plateau. (2) Of the 11 typical nature reserves selected, the positive trend in the NPP for Manzetang was the most significant, whereas there was no obvious trend in Taxkorgan. With the exception of Selincuo, the annual NPP growth rate in the nature reserves covered by alpine meadow and wetland was higher than that in nature reserves consisting of alpine steppe and alpine desert. (3) There were notable findings in 21 typical coupled samples: (a) After the establishment of the nature reserves, the annual rate of increase in the NPP in 76% of samples inside nature reserves and 82% of samples inside national nature reserves was higher than that of the corresponding samples outside nature reserves. (b) The effectiveness of ecological protection of the Mid-Kunlun, Changshagongma, Zoige and Selincuo (Selin Co) nature reserves was significant; the effectiveness of protection was relatively significant in most parts of the Sanjiangyuan and Qiangtang nature reserves, whereas in south-east Manzetang and north Taxkorgan the protection effectiveness was not obvious. (c) The ecological protection effectiveness was significant in nature reserves consisting of alpine meadow, but was weak in nature reserves covered by alpine steppe. This study also shows that the advantage of large sample comparison method in evaluating regional ecology change. Careful design of the samples used, to ensure comparability between the samples, is crucial to the success of this LSCM. 相似文献
319.
320.