全文获取类型
收费全文 | 332篇 |
免费 | 50篇 |
国内免费 | 54篇 |
专业分类
测绘学 | 14篇 |
大气科学 | 20篇 |
地球物理 | 43篇 |
地质学 | 157篇 |
海洋学 | 16篇 |
天文学 | 162篇 |
综合类 | 12篇 |
自然地理 | 12篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 11篇 |
2015年 | 12篇 |
2014年 | 16篇 |
2013年 | 13篇 |
2012年 | 30篇 |
2011年 | 10篇 |
2010年 | 30篇 |
2009年 | 11篇 |
2008年 | 42篇 |
2007年 | 12篇 |
2006年 | 41篇 |
2005年 | 20篇 |
2004年 | 7篇 |
2003年 | 25篇 |
2002年 | 28篇 |
2001年 | 22篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 14篇 |
1997年 | 18篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有436条查询结果,搜索用时 15 毫秒
381.
采用X射线CT技术无损探测岩石内部结构和裂纹演化过程 ,起源于 2 0世纪 80年代后期 ,由最初对CT图像的认识逐步深化为对岩石裂纹演化规律的分析和应用研究。基于室内岩石试件扫描断面的CT图像 ,目前在岩石变形破坏过程的实时监测、加荷条件多样化、裂纹演化规律性、裂纹宽度的定量测量、岩石裂纹三维图像重建、损伤演化与损伤变量分析、CT成果应用研究等方面取得了一系列进展。岩石CT面临的主要问题是如何获得各种试验条件下精确的CT图像及其成果的应用研究。岩石CT的生命力在于自身理论、技术发展和在相关领域的应用程度 相似文献
382.
X射线荧光光谱法直接测定地质样品中多种痕量元素 总被引:2,自引:0,他引:2
采用低压聚乙烯镶边垫底的粉末压饼法制样,X射线荧光光谱法直接测定了地质样品中痕量元素As、Ga、Sc、La、Y、Ce、W、Mo、Sn、Co和Pb。讨论了背景校正、谱线重叠校正、基体效应校正和仪器漂移校正等问题。利用理论α系数代替经验系数,使方法具有较高的准确度和较低的检出限。所测11个元素的检出限在(0.30~2.02)×10-6水平,精度(RSD,n=11)在0.95%~13.0%。方法经国家一级标准物质分析验证,结果与标准值相符。 相似文献
383.
对混合相中硅线石和莫来石的X射线衍射定性,定量分析表明,选取硅线石的d(332)S峰,莫来石的d(331)M峰或硅线石的d(220)S峰,莫来石的d(220)M峰放慢扫描速度,可定性分析硅线石和莫来石;选取硅线石的d(332)S峰,莫来石的d(331)M峰,采用计算机拟合分峰改进自清洗法,可定量分析硅线石和莫来石。经电子探针验证,实验方法准确,可行。 相似文献
384.
385.
386.
387.
388.
L. Paul Bédard 《Geostandards and Geoanalytical Research》2008,32(4):399-403
These mature analytical techniques do not show any change in publication level from the previous two years and AAS remains dominant in terms of the number of publications. The last two years have seen fewer technical improvements than in the previous review period. Some interesting papers dealing with uncertainty and quality assurance in INAA were published during 2006–2007. It is suggested that photon activation should be reconsidered because the source of electron accelerators has recently improved. A technique to preconcentrate Se for INAA determination has also been proposed. In the case of AAS, papers on analyte preconcentration continue to be more abundant than those relating to instrumental modification. Sample preparation for AAS is also active and ultrasound‐assisted leaching shows some promising applications. There were an unusual number of reviews concerned with AAS and those important to geological samples are cited here. A technique to preconcentrate Cr in water is presented and a new device to determine As and Se is showing some potential uses. Confocal X‐ray mapping continues to show interesting developments. One group developed a technique to perform XRF inside an oyster and an interesting application of μ‐XRF mapping of sediments is presented. Determination of platinum‐group elements (at μg g1 concentrations) can be carried out very quickly with an improved XRF technique. 相似文献
389.
D. M. Alexander 《Astronomische Nachrichten》2008,329(2):127-130
We review some recent results on the identification and characterisation of Active Galactic Nuclei (AGN) obtained by cross correlating X‐ray surveys with infrared and submillimetre surveys. We also look toward the scientific gains that could be achieved from an XMM‐Newton survey of the medium‐deep legacy fields that are being observed at ≈ 1–850 μm. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
390.
G. Pühlhofer 《Astronomische Nachrichten》2008,329(2):186-190
Very high energy (VHE) γ‐ray observations have proven to be very successful in localizing Galactic acceleration sites of VHE particles. Observations of shell‐type supernova remnants have confirmed that particles are accelerated to VHE energies in supernova blast waves; the interpretation of the γ‐ray data in terms of hadronic or leptonic particle components in these objects relies nevertheless strongly on input from X‐ray observations. The largest identified Galactic VHE source class consists of pulsar wind nebulae, as detected in X‐rays. Many of the remaining VHE sources remain however unidentified until now. With X‐ray observations of these enigmatic “dark” objects one hopes to solve the following questions: What is the astrophysical nature of these sources? Are they predominantly electron or hadron accelerators? And what is their contribution to the overall cosmic ray energy budget? The paper aims to provide an overview over the identification status of the Galactic VHE source population. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献