全文获取类型
收费全文 | 568篇 |
免费 | 73篇 |
国内免费 | 100篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 126篇 |
地球物理 | 131篇 |
地质学 | 246篇 |
海洋学 | 136篇 |
天文学 | 50篇 |
综合类 | 24篇 |
自然地理 | 19篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 11篇 |
2021年 | 14篇 |
2020年 | 13篇 |
2019年 | 21篇 |
2018年 | 28篇 |
2017年 | 30篇 |
2016年 | 33篇 |
2015年 | 25篇 |
2014年 | 34篇 |
2013年 | 48篇 |
2012年 | 25篇 |
2011年 | 36篇 |
2010年 | 41篇 |
2009年 | 39篇 |
2008年 | 22篇 |
2007年 | 29篇 |
2006年 | 34篇 |
2005年 | 33篇 |
2004年 | 23篇 |
2003年 | 25篇 |
2002年 | 19篇 |
2001年 | 11篇 |
2000年 | 13篇 |
1999年 | 17篇 |
1998年 | 14篇 |
1997年 | 17篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有741条查询结果,搜索用时 484 毫秒
51.
对宁夏20个测站1961—2004年的冬季负积温EOF分析表明,冬季的冷趋势具有明显的大尺度特征,在近40 a逐渐变暖。据累积距平显示,l986年出现了突变,之前,冬季气温偏低,具体表现为冷冬年全部分布在此时段,之后偏暖,90年代以后出现暖冬的频次明显增加。≤0℃持续日数具有明显的年代际变化,2001—2004年比60年代平均减少了13.5 d。在80%保证率下,全区≤0℃持续日数和负积温依地势自北向南增多,引黄灌区最少,中部干旱带次之,南部黄土丘陵区相对最多。 相似文献
52.
Jialin Zhou Xin Zhang Lin Zhang Fang Dong Erwin Oh 《Geomechanics and Geoengineering》2020,15(3):159-171
ABSTRACT This paper describes compressive static load tests of concrete driven piles confined by Carbon Fibre Reinforced Polymer (CFRP). The tested piles include one concrete pipe pile and one concrete rectangular pile which are all partially confined by CFRP, and other two piles with the same dimensions without CFRP application. Tests program was performed to obtain the behaviours of these composite piles. Four Static Loading Tests (SLTs) were conducted and the results shown that those two types of composite pile demonstrate less vertical displacement with the same loading of traditional concrete piles. Furthermore, the traditional methods of Load-settlement (Q-s) curves, Settlement-lg (Load) (s-lgQ) curves and Settlement-lg (Time) curves are analysed. Due to un-plunging condition, the interpretation methods of Davisson’s, DeBeers, Double-Tangent as well as Chin’s methods are demonstrated for the ultimate bearing capacity of these four piles. It is concluded that the CFRP confinement increased the ultimate bearing capacity and this composite material can be perfectly applied in geotechnical condition. 相似文献
53.
54.
Green and Vernon (1974) have experimentally determined a divariant field of cordierite-orthoamphibole-kyanite-quartz with a slope of 12±4 bars per °C occurring between 8.0 and 10.4 kbar at 750° C and between 9.5 and 11.3 kbar at 850° C. However, the writers' thermodynamic calculation of the divariant band indicates a more limited range of 0.65 and 0.7 kbar at 750° C and 850° C respectively, with an estimated error of ±0.2 kbar. 相似文献
55.
V andB observations of V711 Tauri (HR 1099) for the year 1982–1983 are presented. The light curves made with the data of this season are compared with those of the previous observations of the 1981–1982 season. The single-peaked maximum light had shifted slightly and the peak amplitude had decreased to 0.04 mag. inV. No clear sign of colour,B–V, variation in comparison with the low temperature dark-spot is detected.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
56.
Hans-Uwe Dahms Hyoung-Min Joo Jae Hyung Lee Mi Sun Yun So Hyun Ahn Sang Heon Lee 《Ocean Science Journal》2015,50(4):639-648
Demersally drifting organisms were collected at Ny Ålesund (Svalbård–Arctic Ocean) to study the taxon composition and relative abundances in the Arctic summer. Catch potentials of two collection devices for demersal drift were compared. A lowvolume submersible drift-pump and a drift-net unit were employed for the collection of demersally drifting biota, particularly for shallow aquatic habitats. With the exception of Appendicularia, Chaetognatha, Coelenterata, and Ctenophora, which were damaged at times, the pump catches were in good condition and sufficient for identification and quantification of less mobile fauna. A comparison of the two devices revealed that the drift-pump collected more specimens than the drift-net. However, the drift-net may have caused an underestimation of the abundances of invertebrates. No differences in identified taxon number and indices of richness, evenness and diversity were found. However, the proportion of invertebrate animals in the two devices was different for the three groups: zooplankton, macrofauna and meiofauna. At Svalbård, zooplankton, larvae of macrofauna, and meiofauna were successfully collected by the two collecting devices. However, the catchibility of the two devices in collecting various invertebrate taxa was different and, therefore, a sound ‘Device Effect’ was revealed. 相似文献
57.
Natural disasters as the end of the insurance industry? Scalar competitive strategies, Alternative Risk Transfers, and the economic crisis 总被引:1,自引:0,他引:1
The aftermath of Hurricane Katrina has piqued interest in the insurance industry, and this scrutiny has led to assumptions that the industry has become unstable and unprofitable with the increased incidence of disasters in highly-insured regions of the world. This paper challenges that assumption by arguing that the insurance industry has responded by spreading risk through scaled and networked recovery schemes. We found that because of competitive strategies of risk-spreading and displacement arrangements, the industry has actually profited as a whole. Regional insurance companies have always relied on the higher financial scales of the reinsurance industry in Munich, Zurich, and London. But with claims reaching into the billions of dollars, the reinsurance industry itself has raised premiums, spread risk farther afield, and jumped scale by spreading risk to futures markets called Alternative Risk Transfers (ARTs). However, the recession beginning in 2008 has called into question the viability of using futures markets as insurance. It is shown through a media analysis of four major business publications (The Economist, The New York Times, The Financial Times and The Wall Street Journal) how the industry responded to the costs of the 2004, 2005, and 2006 hurricane seasons. Because geography is rather new to this literature, this paper also offers a broad review of the insurance industry. 相似文献
58.
59.
采用高压超临界CO2地球化学反应器对CO2在煤储层中的地质埋藏进行模拟,利用电感耦合等离子体发射光谱仪(ICP-OES)以及电感耦合等离子体质谱(ICP-MS)分别对淋滤液和煤样中的10种微量元素进行测试,对煤中微量元素在CO2的地质埋藏过程中的迁移进行了实验研究。结果表明:在CO2的地质埋藏过程中对煤的有机组成和无机矿物等均具有改造作用,从而影响到煤中微量元素的赋存和迁移特征,Cr、Zn、Cu等元素迁移能力相对较强,而Co、Ba、V等元素相对较弱;元素迁移能力大小顺序为:CrZnCuNiCdMnCoBaV。 相似文献
60.
In this study, the electrical resistivity of soil having different chemical weathering index (CWI) was measured, and the correlation
between CWI and the electrical resistivity was estimated. The electrical resistivity of soil varies with CWI of soil. The
difference in the electrical resistivities of soils having different weathering degrees is clear at lower water contents.
At the volumetric water contents estimated in this study, CWI could be described by a linear equation of electrical resistivity
with the constants related to the volumetric water content. The findings in this study suggest that the electrical resistivity
could be used as an effective alternative for estimating the weathering degree of soil. 相似文献