全文获取类型
收费全文 | 7918篇 |
免费 | 1484篇 |
国内免费 | 1708篇 |
专业分类
测绘学 | 536篇 |
大气科学 | 348篇 |
地球物理 | 621篇 |
地质学 | 6283篇 |
海洋学 | 1026篇 |
天文学 | 15篇 |
综合类 | 767篇 |
自然地理 | 1514篇 |
出版年
2024年 | 27篇 |
2023年 | 112篇 |
2022年 | 247篇 |
2021年 | 340篇 |
2020年 | 289篇 |
2019年 | 374篇 |
2018年 | 283篇 |
2017年 | 273篇 |
2016年 | 350篇 |
2015年 | 363篇 |
2014年 | 485篇 |
2013年 | 424篇 |
2012年 | 445篇 |
2011年 | 525篇 |
2010年 | 457篇 |
2009年 | 503篇 |
2008年 | 467篇 |
2007年 | 518篇 |
2006年 | 580篇 |
2005年 | 474篇 |
2004年 | 475篇 |
2003年 | 406篇 |
2002年 | 377篇 |
2001年 | 366篇 |
2000年 | 313篇 |
1999年 | 285篇 |
1998年 | 259篇 |
1997年 | 202篇 |
1996年 | 187篇 |
1995年 | 136篇 |
1994年 | 127篇 |
1993年 | 105篇 |
1992年 | 73篇 |
1991年 | 67篇 |
1990年 | 48篇 |
1989年 | 34篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 14篇 |
1984年 | 15篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
261.
262.
GEOCHEMICAL CHARACTERISTICS OF GRANITES AND ITS STRUCTURAL GENETIC ENVIRONMENT IN THE NANDAN-HECHI METALLOGENETIC BELT, NORTHWEST GUANGXI 总被引:3,自引:0,他引:3
The Nandan-Hechi metallogenetic belt is the most important tin-polymetallic producing district in China, and is the location of the Dachang super-large tin deposit. Based on the detailed field investigation and isotopic data, the stages of magmatic activity in the Nandan-Hechi metallogenetic belt have been lined out in this paper. Through the study about the geochemical characteristics of different granites, and by using ω(Al2O3)-ω(SiO2), ω(TFeO)/[ω(TFeO) ω(MgO)]-ω(SiO2), AFM, ACF and Rb-Yb Ta, Rb-Y Nb,Ta-Yb, Nb-Y discrimination diagrams in combination with regional geological setting analysis, the authors carried out analyses about the structural environment for the formation of the granites, and discussed the structural environment and dynamic setting for the large scale mineralization in this area. Our study indicates that the majority of the granites in Nandan-Hechi metallogenetic belt belong to the POG type,while the later stage alaskite belongs to the RRG CEUG type. The granites were formed at the stage of structural transformation from postorogenic phase to intraplate setting. But the major structural environment is characterized by steady regional extension. The formation age for the granites coincides with the time for this transformation, and this translation environment is favored for large-scale metallogenesis. 相似文献
263.
开滦矿区煤系地层上覆由于防水煤柱留设过大,造成了大量的煤炭储量呆滞。为了提高煤炭资源回收率,确保安全生产,开滦林南仓矿在西二采区进行了工作面采后的导高观测试验研究,测量导水裂隙带岩层的漏失情况,为提高开采上限提供了地质依据,防水煤柱由原来的65m缩小到53m,成功地在1221上工作面进行了试验开采。 相似文献
264.
根 据 某露 天 煤 矿 非工 作 帮 移 动监 测 的 多 年资 料 ,总 结 出 露 天矿 非 工 作 帮的 监 测 方 法,并 初 步探 讨 了 露 天 矿非 工作 帮 移动 滑坡 的 规律 性。 相似文献
265.
Lijiang-Daju fault, the seismogenic fault of the 1996 Lijiang M=7.0 earthquake, can be divided into Lijiang-Yuhu segment in the south and Yuhu-Daju segment in the north. The two segments show clear difference in geological tectonics, but have the similar dynamic features. Both normal dip-slip and sinistral strike-slip coexist on the fault plane. This kind of movement started at the beginning of the Quaternary (2.4~2.5 Ma B.P.). As to the tectonic types, the detachment fault with low angle was developed in the Early Pleistocene and the normal fault with high angle only after the Mid-Pleistocene (0.8 Ma B.P.). Based on the horizontal displacements of gullies and the vertical variance of planation surfaces cross the Lijiang-Daju fault at east piedmont of Yulong-Haba range, the average horizontal and vertical slip rates are calculated. They are 0.84 mm/a and 0.70 mm/a since the Quaternary and 1.56 mm/a and 1.69 mm/a since the Mid-Pleistocene. The movements of the nearly N-S-trending Lijiang-Daju fault are controlled not only by the regional stress field, but also by the variant movement between the Yulong-Haba range and Lijiang basin. The two kinds of dynamic processes form the characteristics of seismotectonic environment of occurring the 1996 Lijiang earthquake. 相似文献
266.
Problem on development control of marine source bed hold in Chinese petroleum industry progression. The Hongshuizhuang Formation,Tieling Formation and Xiamaling Formation in the Middle and Upper Proterozoic are important hydrocarbon source beds in northern North China, and investigation of their sedimentary environments and the controls has great significance for petroleum exploration in North China. Based on sedimentology (sequence stratigraphy), palaeoecology, sedimentary geochemistry, and sedimentary palaeogeography, their development pattern is discussed. All these studies indicate that the development controls of the hydrocarbon source beds include a favorite palaeogeographic location, exceeding propagation of biomes in low and middle latitudes, anoxic environments, enrichment of phosphorus element and the adsorption of clay minerals during the preservation of organic matter in the marine carbonates. 相似文献
267.
At 19:33 p. m on September 27, 2003, an earthquake with M7.9 occurred in the RussiaMongolia-China boundary Region. It was strongly felt in the Altay region of Xinjiang. The losses caused by the earthquake was 76 million yuan (RMB). Some information about the earthquake was outlined, including basic parameters, focal mechanism, evaluation of earthquake disaster losses and so on. The satellite remote sensing information worked initial analysis for deformation of ground and failure phenomenon. 相似文献
268.
269.
270.