全文获取类型
收费全文 | 9033篇 |
免费 | 1229篇 |
国内免费 | 2045篇 |
专业分类
测绘学 | 1749篇 |
大气科学 | 1132篇 |
地球物理 | 1825篇 |
地质学 | 4467篇 |
海洋学 | 1025篇 |
天文学 | 470篇 |
综合类 | 638篇 |
自然地理 | 1001篇 |
出版年
2024年 | 28篇 |
2023年 | 106篇 |
2022年 | 214篇 |
2021年 | 341篇 |
2020年 | 325篇 |
2019年 | 421篇 |
2018年 | 313篇 |
2017年 | 483篇 |
2016年 | 433篇 |
2015年 | 473篇 |
2014年 | 513篇 |
2013年 | 735篇 |
2012年 | 497篇 |
2011年 | 539篇 |
2010年 | 434篇 |
2009年 | 545篇 |
2008年 | 631篇 |
2007年 | 624篇 |
2006年 | 633篇 |
2005年 | 528篇 |
2004年 | 516篇 |
2003年 | 440篇 |
2002年 | 387篇 |
2001年 | 325篇 |
2000年 | 321篇 |
1999年 | 267篇 |
1998年 | 227篇 |
1997年 | 211篇 |
1996年 | 134篇 |
1995年 | 138篇 |
1994年 | 122篇 |
1993年 | 88篇 |
1992年 | 66篇 |
1991年 | 42篇 |
1990年 | 42篇 |
1989年 | 26篇 |
1988年 | 34篇 |
1987年 | 19篇 |
1986年 | 18篇 |
1985年 | 24篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1954年 | 3篇 |
1877年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 718 毫秒
91.
92.
93.
94.
The Baimazhai nickel deposit, Yunnan Province, China, is located in the southern part of the Sanjiang (Tri-river) alkali-rich intrusive rock belt (Sanjiang ARIR). In this paper was conducted ^40Ar-^39Ar dating of two phlogopites in lamprophyres which are, as dikes, widely distributed in the orefield, and two plateau ages were acquired, i.e., 32.46±0.62 Ma and 32.01±0.60 Ma, respectively (averaging 32.23±0.60 Ma). The ages are obviously younger than those of the ore-hosted complex and mineralization of the Baimazhai nickel deposit. In combination with the characteristics, it is indicated that lamprophyres in the orefield and those in the Sanjiang ARIR are similar in tectonic setting, mineral assemblage and geochemistry. It is considered that lamprophyres in the orefield are the important component of the Sanjiang ARIR, and the lamprophyres and ore-hosted complex in the orefield represent the products of two times of different magmatic activity from different mantle sources. On the other hand, the age of lamprophyres in the orefield is older than that of the strike-slip shearing of the Ailaoshan-Honghe fault belt, suggesting that the strike-slip shearing of the Ailaoshan-Honghe fault belt is not the factor leading to magmatic activity of lamprophyres in the orefield, while it is more possible that magmatic activity of the Sanjiang ARIR promoted strike-slip shearing of the fault belt. 相似文献
95.
Late Cenozoic Stratigraphy and Paleomagnetic Chronology of the Zanda Basin, Tibet, and Records of the Uplift of the Qinghai-Tibet Plateau 总被引:1,自引:0,他引:1
MENG Xiangang ZHU Dagang SHAO Zhaogang YANG Chaobin HAN Jianen YU Ji MENG Qingwei LU Rongping 《《地质学报》英文版》2008,82(1):63-72
The characteristics of Late Cenozoic tectonic uplift of the southern margin of the Qinghai- Tibet Plateau may be inferred from fluvio-lacustrine strata in the Zanda basin, Ngari, Tibet. Magnetostratigraphic study shows that the very thick fluvio-lacustrine strata in the basin are 5.89- 0.78 Ma old and that their deposition persisted for 5.11 Ma, i.e. starting at the end of the Miocene and ending at the end of the early Pleistocene, with the Quaternary glacial stage starting in the area no later than 1.58 Ma. Analysis of the sedimentary environment indicates that the Zanda basin on the southern Qinghai-Tibet Plateau began uplift at -5.89 Ma, later than the northern Qinghai-Tibet Plateau. Presence of gravel beds in the Guge and Qangze Formations reflects that strong uplift took place at -5.15 and -2.71 Ma, with the uplift peaking at -2.71 Ma. 相似文献
96.
97.
98.
内蒙古兴安盟杜尔基岩体位于大兴安岭中南段,岩性主要为中—细粒二长花岗(斑)岩、中—粗粒二长花岗岩、细粒二长花岗岩。岩石化学分析结果属于碱性岩系列,具有高硅、高钾、富碱、过铝、贫铁、镁、钙特征。稀土元素总量平均值为112.43μg/g,球粒陨石标准化曲线整体平缓右倾,具有Eu负异常;微量元素蛛网图解表现为“W”型形态.具有明显的Sr、Ba、Ti负异常,反映了强烈的分离结晶作用存在。4个样品K-Ar全岩法测年结果为100.15-120.29Ma,说明岩体形成于早白垩世。反映杜尔基地区在早自垩世可能处于相对稳定的拉张环境。 相似文献
99.
地理信息服务中数据传输性能分析 总被引:2,自引:0,他引:2
地理信息服务系统具有数据密集型和计算密集型的特点,对网络环境的设置有着特殊的需求。本文从地理信息服务系统中对数据传输应用的角度出发,从网络数据传输协议的传输层和应用层两个层次分析地理信息服务系统应用的特殊性,并根据系统应用的特殊需求提出相应的解决方案,提高整个应用系统中各类数据传输的效率、性能和系统运行的稳定性,提高地理信息服务系统为多用户提供地图服务、位置服务以及各种应用服务的综合能力。提高系统适应多用户并发访问海量数据的地图服务作业和频繁访问实效性很强的位置服务作业的能力。 相似文献
100.
The 40Ar/39Ar method using a laser probe opened the door to microscale measurements and diffusion profiles frozen in samples. In the first decade since the initial application of a laser for 40Ar/39Ar dating in 1973, practical applications have been few. This is due not only to the fact that the laser and vacuum technologies were immature but that mass spectrometry was also in its infancy. In those days, the sensitivity of a mass spectrometer was generally insufficient to measure the small amount of argon degassed from a geological sample by a laser. These problems have subsequently been solved by new technologies. To understand their current status, a brief history of their development is outlined. This outline focuses on the required detection limit in micro scale measurement, practical approaches for accurate measurement are explained through examples in our laboratory specifically relating to the technical aspects of 40Ar/39Ar dating. 相似文献