全文获取类型
收费全文 | 87篇 |
免费 | 45篇 |
国内免费 | 33篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 19篇 |
地球物理 | 73篇 |
地质学 | 26篇 |
海洋学 | 17篇 |
天文学 | 16篇 |
综合类 | 1篇 |
自然地理 | 1篇 |
出版年
2024年 | 3篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 9篇 |
2012年 | 7篇 |
2011年 | 7篇 |
2010年 | 9篇 |
2009年 | 8篇 |
2008年 | 6篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 11篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1989年 | 2篇 |
1985年 | 4篇 |
1982年 | 2篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1968年 | 1篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1961年 | 2篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1943年 | 4篇 |
1942年 | 2篇 |
1940年 | 1篇 |
1938年 | 1篇 |
1937年 | 4篇 |
排序方式: 共有165条查询结果,搜索用时 0 毫秒
61.
62.
正 DIAGNOSIS: Test fusiform, slightly rounded at the ends; about 11.2 mm. long, 3.7 mm. wide, giving an axial ratio of about 1:3; whorl 9 to 10, the first three or four volutions closely coiled thence gradually evolute; spiral wall increases in thickness as the test grows, being 0.016 mm. in the firs 相似文献
63.
64.
观测表明,大陆地区存在很多传统均衡模型无法解释的现象,其根本原因在于传统均衡理论中没有考虑地幔岩石圈部分由于热结构差异导致密度差异的影响.本文基于岩石圈尺度的质量平衡模型研究了中国大陆20个构造单元地壳及地幔岩石圈对地形海拔的贡献,以及各块体的均衡状态.计算结果表明,在一些地区,如塔里木盆地、北山和柴达木盆地,尽管岩石圈均衡模型和Airy模型得到了一致的海拔值,但岩石圈均衡模型更能体现均衡过程的物理本质;除青藏高原造山带外的多数块体,岩石圈均衡模型的计算结果更接近观测海拔和地表垂直运动状态;总体上,考虑地幔岩石圈热结构影响后,中国大陆各地区的均衡结果普遍优于传统的均衡模型.通过对均衡状态分析,我们得到以下主要结论:(1)构造稳定地区均衡程度较高;(2) 青藏高原及周边造山带现今地壳运动主要为区域构造过程及深部动力学过程所控制,均衡调整过程不是主要控制因素;(3) 现今地壳垂直运动比较明显的块体处于均衡调整阶段,地表垂直运动的大小反映了该区所受的均衡力作用的程度;(4) 构造稳定地区基于岩石层均衡的理论计算海拔与观测海拔之差值和现今地壳垂直运动速率有较好的相关性,据此我们可以通过均衡分析研究构造块体的运动趋势和动力学性质;(5) 地幔热结构对现今地形、海拔及地壳垂直运动有显著影响,在处理均衡问题时,地幔岩石圈热结构是我们必须考虑的重要因素. 相似文献
65.
66.
Abstract— Electron and ion microprobe measurements of major, minor, and trace element concentrations were made in individual grains of pyroxene, plagioclase, and Ca phosphates in Pomozdino and Peramiho, two eucrites previously classified as anomalous. Although Pomozdino pyroxene is highly magnesian, minor and trace element concentrations in both pyroxene and plagioclase of this meteorite are similar to those in other noncumulate eucrites. High incompatible element concentrations (similar to those in Stannern) coupled with mg# typical of cumulate eucrites confirm the anomalous character of this meteorite but do not allow us to distinguish unequivocally between different possible modes of origin. Peramiho has mg# and trace element concentrations similar to main group eucrites, indicating that this meteorite most probably belongs to this group. A previously reported low incompatible element concentration for Peramiho may be due to a sampling problem. 相似文献
67.
Abstract— Here we report the petrography, mineralogy, and bulk compositions of Ca,Al‐rich inclusions (CAIs), amoeboid olivine aggregate (AOA), and Al‐rich chondrules (ARCs) in Sayh al Uhaymir (SaU) 290 CH chondrite. Eighty‐two CAIs (0.1% of the section surface area) were found. They are hibonite‐rich (9%), grossite‐rich (18%), melilite ± spinel‐rich (48%), fassaite ± spinel‐rich (15%), and fassaite‐anorthite‐rich (10%) refractory inclusions. Most CAIs are rounded in shape and small in size (average = 40 μm). They are more refractory than those of other groups of chondrites. CAIs in SaU 290 might have experienced higher peak heating temperatures, which could be due to the formation region closer to the center of protoplanetary disk or have formed earlier than those of other groups of chondrites. In SaU 290, refractory inclusions with a layered texture could have formed by gas‐solid condensation from the solar nebula and those with an igneous texture could have crystallized from melt droplets or experienced subsequent melting of pre‐existing condensates from the solar nebula. One refractory inclusion represents an evaporation product of pre‐existing refractory solid on the basis of its layered texture and melting temperature of constituting minerals. Only one AOA is observed (75 μm across). It consists of olivine, Al‐diopside, anorthite, and minor spinel with a layered texture. CAIs and AOA show no significant low‐temperature aqueous alteration. ARCs in SaU 290 consist of diopside, forsterite, anorthite, Al‐enstatite, spinel, and mesostasis or glass. They can be divided into diopside‐rich, Al‐enstatite‐rich, glass‐rich, and anorthite‐rich chondrules. Bulk compositions of most ARCs are consistent with a mixture origin of CAIs and ferromagnesian chondrules. Anorthite and Al‐enstatite do not coexist in a given ARC, implying a kinetic effect on their formation. 相似文献
68.
69.
70.