全文获取类型
收费全文 | 1073篇 |
免费 | 426篇 |
国内免费 | 135篇 |
专业分类
测绘学 | 24篇 |
大气科学 | 13篇 |
地球物理 | 67篇 |
地质学 | 746篇 |
海洋学 | 32篇 |
天文学 | 690篇 |
综合类 | 43篇 |
自然地理 | 19篇 |
出版年
2024年 | 6篇 |
2023年 | 5篇 |
2022年 | 22篇 |
2021年 | 27篇 |
2020年 | 23篇 |
2019年 | 37篇 |
2018年 | 29篇 |
2017年 | 39篇 |
2016年 | 47篇 |
2015年 | 41篇 |
2014年 | 51篇 |
2013年 | 45篇 |
2012年 | 61篇 |
2011年 | 66篇 |
2010年 | 62篇 |
2009年 | 123篇 |
2008年 | 79篇 |
2007年 | 97篇 |
2006年 | 123篇 |
2005年 | 92篇 |
2004年 | 89篇 |
2003年 | 83篇 |
2002年 | 62篇 |
2001年 | 60篇 |
2000年 | 59篇 |
1999年 | 58篇 |
1998年 | 38篇 |
1997年 | 24篇 |
1996年 | 18篇 |
1995年 | 15篇 |
1994年 | 19篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 9篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有1634条查询结果,搜索用时 265 毫秒
991.
地震测井是求取地震波在地层中的传播速度的一种有效的方法,其主要用途是标定地震地质层位,判定终孔深度.该技术在龙家堡南部地区准确地标定了TY1、TY地震地质层位,确定了M12的终孔深度. 相似文献
992.
为了解决在煤矿瓦斯抽放长钻孔施工中由于冲洗介质对孔壁的冲刷作用而出现塌孔、埋钻等难题,采用泡沫增压技术通过提供高压泡沫流压力来解决。论述了应用泡沫增压技术解决煤矿瓦斯抽放长钻孔施工问题的可行性和经济性。 相似文献
993.
E. rmkov 《Astronomische Nachrichten》2005,326(9):835-837
All normal modes of oscillations of slender tori have been expressed analytically in the classic work by Blaes (1985). We adopt his approach in order to calculate the eigenfunctions and eigenfrequencies of a particular class of epicyclic modes for slightly non‐slender tori, and present results of our numerical simulation of torus epicyclic modes of oscillations, which will be compared with the analytical results. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
994.
A. Müller 《Astronomische Nachrichten》2006,327(10):1024-1027
We study and quantify gravitational redshift by means of relativistic ray tracing simulations of emission lines. The emitter model is based on thin, Keplerian rotating rings in the equatorial plane of a rotating black hole. Emission lines are characterised by a generalized fully relativistic Doppler factor or redshift associated with the line core. Two modes of gravitational redshift, shift and distortion, become stronger with the emitting region closer to the Kerr black hole. Shifts of the line cores reveal an effect at levels of 0.0015 to 60% at gravitational radii ranging from 105 to 2. The corresponding Doppler factors range from 0.999985 to 0.4048. Line shape distortion by strong gravity, i.e. very skewed and asymmetric lines occur at radii smaller than roughly ten gravitational radii. Gravitational redshift decreases with distance to the black hole but remains finite due to the asymptotical flatness of black hole space–time. The onset of gravitational redshift can be tested observationally with sufficient spectral resolution. Assuming a resolving power of ∼100000, yielding a resolution of ≈0.1 Å for optical and near‐infrared broad emission lines, the gravitational redshift can be probed out to approximately 75000 gravitational radii. In general, gravitational redshift is an indicator of black hole mass and spin as well as for the inclination angle of the emitter, e.g. an accretion disk. We suggest to do multi‐wavelength observations because all redshifted features should point towards the same central mass. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
995.
基于光照水电站坝基水文地质条件及坝体渗透特性的研究,建立了大坝三维有限元模型,模型较详细地考虑了坝体大坝不防渗结构和排水系统及坝基地质和防排渗结构。分析研究了薄层单元、排水孔幕的模拟方法,采用合适的方法计算了同条件下的渗控情况。通过综合对比分析,对该坝的渗流规律及相应渗控措施进行了初步地探讨。 相似文献
996.
经过对不同时期洪积物的成因、物质组成、结构、构造等的分析,以及对第一期洪积物内能否成洞的试验性模拟开挖、观察、分析,并在大量室内外物理力学性质试验的基础上,分析、量化出洪积物内成洞工程地质特性参数。在精心设计和施工下,深厚洪积物内开挖大跨度洞室顺利成功。 相似文献
997.
998.
999.
1000.
Zexia Qiu Hangzhou Wang Tao Li Hong Song Yuanqian Wu Tingting Yan Ying Chen 《海洋学报(英文版)》2021,40(3):134-141
An irradiance profile measurement approach and profiling system were developed to measure the solar irradiance profile of the Arctic sea ice using fiber optic spectrometry. The approach involved using a miniature spectrometer to sense light signals collected and transmitted from a fiber probe. The fiber probe was small, and could thus move freely in inclined bore holes drilled in sea ice with its optical entrance pointing upward. The input-output relationship of the system was analyzed and built. Influence factors that determined the system output were analyzed. A correctional system output approach was proposed to correct the influence of these factors, and to obtain the solar irradiance profile based on the measurements outputted by this system. The overall performance of the system was examined in two ice floes in the Arctic during the 9 th Chinese National Arctic Research Expedition. The measured solar irradiance profiles were in good agreement with those obtained using other commercially available oceanographic radiometers. The derived apparent optical properties of sea ice were comparable to those of similar sea ice measured by other optical instruments. 相似文献