全文获取类型
收费全文 | 3139篇 |
免费 | 522篇 |
国内免费 | 897篇 |
专业分类
测绘学 | 220篇 |
大气科学 | 606篇 |
地球物理 | 854篇 |
地质学 | 1633篇 |
海洋学 | 394篇 |
天文学 | 105篇 |
综合类 | 363篇 |
自然地理 | 383篇 |
出版年
2024年 | 15篇 |
2023年 | 53篇 |
2022年 | 176篇 |
2021年 | 187篇 |
2020年 | 168篇 |
2019年 | 175篇 |
2018年 | 229篇 |
2017年 | 187篇 |
2016年 | 186篇 |
2015年 | 166篇 |
2014年 | 204篇 |
2013年 | 229篇 |
2012年 | 195篇 |
2011年 | 205篇 |
2010年 | 203篇 |
2009年 | 205篇 |
2008年 | 156篇 |
2007年 | 174篇 |
2006年 | 121篇 |
2005年 | 91篇 |
2004年 | 100篇 |
2003年 | 86篇 |
2002年 | 73篇 |
2001年 | 80篇 |
2000年 | 114篇 |
1999年 | 114篇 |
1998年 | 79篇 |
1997年 | 87篇 |
1996年 | 99篇 |
1995年 | 78篇 |
1994年 | 72篇 |
1993年 | 65篇 |
1992年 | 43篇 |
1991年 | 23篇 |
1990年 | 29篇 |
1989年 | 22篇 |
1988年 | 17篇 |
1987年 | 13篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1936年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有4558条查询结果,搜索用时 31 毫秒
11.
Maggie Cusack Yannicke Dauphin Jean-Pierre Cuif Murielle Salom Andy Freer Huabing Yin 《Chemical Geology》2008,253(3-4):172-179
Biominerals are natural composite materials comprising organic and inorganic components. Detailed knowledge of the nature and distribution of both components is a crucial requirement in order to advance our understanding of biomineral formation, their material properties and preservation potential as well as the interpretation of environmental data. Detailed chemical data are essential for our understanding of the nature and distribution of such components. Micro-XANES mapping at the sulphur K-edge reveals that, in the brachiopod Terebratulina retusa, the sulphate concentration is higher in the outer (primary) layer than in the calcite fibres of the secondary layer. This is co-incident with a higher magnesium concentration. In contrast, the sheaths surrounding the calcite fibres contain sulphur as thiol, confirming the presence of protein while, the sulphur within the fibres themselves, occurs as sulphate. Micro-XANES analysis of the insoluble organic extract from T. retusa indicates the presence of organic sulphate while Micro-Raman spectroscopy confirms that structurally substituted sulphate (SSS) is also present although semi-quantitative Raman spectroscopy carried out in this spectral region (wavenumbers 900–1200) indicates that the sulphate present is at the threshold of detection by Raman spectroscopy. The distribution of phosphorus in the shell of T. retusa correlates well with that of protein indicating the presence of phosphorylated proteins in the periostracum, the sheaths surrounding the calcite fibres and the interface between the primary and secondary layer. 相似文献
12.
Controlling of landsides safely and economically is a great challenge to mine operators because landslides are major geological
problems especially in open-pit mines. In this paper, a case history at Panluo open-pit mine is presented in detail to share
the experiences and lessons with mine operators. Panluo open-pit mine is located in the southwestern Fujian province of China.
It is the largest open-pit iron mine in the Fujian province and was planned in 1965 and is in full operation from 1978. In
July 1990, an earthquake of magnitude 5.3 in Taiwan Strait and big rainstorms impacted the mine slope, causing tension cracks
and rather large-scale failures, and forming a U-shaped landslide. Total potential volume was estimated to be up to 1.0 × 106 m3. This directly threatened the mine production. In order to protect the mine production and the dwellers’ safety around, a
dynamic comprehensive method was implemented including geotechnical investigations, in-situ testing and monitoring, stability
analysis, and many mitigation and preventive measures. These measures slowed down the development and further occurrence of
the landslide. The results showed that the landslides were still active, it was slowed with the control measures and moved
rapidly with rainfall and mining down. However, no catastrophic accidents occurred and the pit mining was continued till it
was closed at the elevation of 887 m in 2000. As a successful case of landslide control at an open-pit mine for 10 years,
this paper reports the controlling measures in details. These experiences of landslide control may be beneficial to other
similar mines for landslide control. 相似文献
13.
Recently, some results have been acquired with the Monte- Carlo statistical experiments in the design of ocean en gineering. The results show that Monte-Carlo statistical experiments can be widely used in estimating the parameters of wave statistical distributions, checking the probability model of the long- term wave extreme value distribution under a typhoon condition and calculating the failure probability of the ocean platforms. 相似文献
14.
大西洋中脊TAG热液活动区中热液沉积物的稀土元素地球?… 总被引:15,自引:0,他引:15
用ICP-MS对TAG热液活动区表层热液沉积物中6个块状硫化物样品进行了稀土元素分析。所有样品均表现出正Eu异常和LREE相对富集的球粒陨石标准化配分模式,热液沉积物样品中稀土元素组成的变化是由于海底热液循环体系中热液流体和涨水不同程度混合作用的结果, 相似文献
15.
Variation of reactivity of particulate and sedimentary organic matter along the Zhujiang River Estuary 总被引:3,自引:0,他引:3
To investigate organic matter source and reactivity in the Zhujiang River (Pearl River)Estuary and its adjacent areas, particulate organic carbon (POC), particulate hydrolysable amino acids (PHAA), and Chl a during two cruises in July 1999 and July 2000 were measured. The highest POC and PHAA concentration was observed in the waters with maximum Chl a. The spectra distribution,relative content (dry weight in milligram per gram), PHAA-C% POC and other indicators such as the ratios of amino acids vs. amino sugars (AA/AS) and glucosamine vs. galactosamine (Glum/Gal) suggested that particulate amino acids in the water column and sediments in the Zhujiang River Estuary were mainly derived from biogenic processes rather than transported from terrestrial erosion. In inner estuary where high turbidity was often observable, organic matter was mainly contributed by re-suspension of bottom sediments with revealed zooplankton, microbial reworked characteristics, which suggest that these organic matters were relatively “old“. In the estuarine brackish region, organic matter in water column is mainly contributed by relatively fresh, easily degradable phytoplankton derived organic matter.During physical - biological processes within the eastuary, organic matter derived from phytoplankton was subjected to alteration by zooplankton grazing and bacterial reworking. 相似文献
16.
冰心中的气候环境记录与全球变化研究 总被引:1,自引:0,他引:1
冰心是高分辨地记录全球变化的主要信息载体之一。本文总结了冰心中提取古气候和古环境信息的系列记录,包括同位素、微量气体、阴阳离子、微粒、生物和有机质等。着重讨论了由这些记录提取的古气候和古环境变化方面的研究进展,并提出了今后的研究重点。 相似文献
17.
18.
东海陆架北部表层细粒级沉积物的级配及意义 总被引:3,自引:3,他引:3
本文依据东海陆架北部 2 3个表层沉积物样品的粒度分析资料 ,就东海陆架北部表层细粒级沉积物的级配及意义进行了研究。结果表明 ,研究区表层沉积物中细粒级部分以 <0 .0 16 mm为优势粒级 ,可占到总细粒级沉积物的 75 %以上。济州岛西南泥质区以细于 0 .0 0 8mm粒级的沉积物占据优势 ,长江口泥质区则以 <0 .0 16 mm粒级的沉积物为主 ,两泥质区细粒级沉积物的级配很不相同 相似文献
19.
20.
Gene specific primers and DNA probe were designed based on the sequence of 18S rDNA cloned from the red tide alga Thalassiosira rotula. A real-time fluorescent quantitative PCR (RFQ-PCR) method was developed for quantitative detection of T.rotula. The RFQ-PCR assay data showed that the results obtained with the RFQ-PCR quite good agreement with those with the light microscope (LM) counting method, which suggested that the RFQ-PCR could be a useful method for red tide alga detection. 相似文献