全文获取类型
收费全文 | 509篇 |
免费 | 20篇 |
国内免费 | 19篇 |
专业分类
测绘学 | 15篇 |
大气科学 | 53篇 |
地球物理 | 160篇 |
地质学 | 151篇 |
海洋学 | 130篇 |
天文学 | 11篇 |
综合类 | 8篇 |
自然地理 | 20篇 |
出版年
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 22篇 |
2017年 | 21篇 |
2016年 | 33篇 |
2015年 | 28篇 |
2014年 | 29篇 |
2013年 | 39篇 |
2012年 | 31篇 |
2011年 | 43篇 |
2010年 | 35篇 |
2009年 | 31篇 |
2008年 | 30篇 |
2007年 | 29篇 |
2006年 | 19篇 |
2005年 | 29篇 |
2004年 | 15篇 |
2003年 | 15篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1998年 | 5篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1992年 | 5篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1970年 | 1篇 |
1958年 | 1篇 |
1955年 | 1篇 |
1951年 | 4篇 |
1950年 | 1篇 |
1949年 | 2篇 |
1948年 | 3篇 |
排序方式: 共有548条查询结果,搜索用时 15 毫秒
211.
Gernot Arp Andreas Reimer Klaus Simon Sebastian Sturm Jakob Wilk Corina Kruppa Lutz Hecht Bent T. Hansen Jean Pohl Wolf Uwe Reimold Thomas Kenkmann Dietmar Jung 《Meteoritics & planetary science》2019,54(10):2448-2482
The 26 km diameter Nördlinger Ries is a complex impact structure with a ring structure that resembles a peak ring. A first research drilling through this “inner crystalline ring” of the Ries was performed at the Erbisberg hill (SW Ries) to better understand the internal structure and lithology of this feature, and possibly reveal impact‐induced hydrothermal alteration. The drill core intersected the slope of a 22 m thick postimpact travertine mound, before entering 42 m of blocks and breccias of crystalline rocks excavated from the Variscan basement at >500 m depth. Weakly shocked gneiss blocks that show that shock pressure did not exceed 5 GPa occur above polymict lithic breccias of shock stage Ia (10–20 GPa), with planar fractures and planar deformation features (PDFs) in quartz. Only a narrow zone at 49.20–50.00 m core depth exhibits strong mosaicism in feldspar and {102} PDFs in quartz, which are indicative of shock stage Ib (20–35 GPa). Finally, 2 m of brecciated Keuper sediments at the base of the section point to an inverse layering of strata. While reverse grading of clast sizes in lithic breccias and gneiss blocks is consistent with lateral transport, the absence of diaplectic glass and melt products argues against dynamic overthrusting of material from a collapsing central peak, as seen in the much larger Chicxulub structure. Indeed, weakly shocked gneiss blocks are rather of local provenance (i.e., the transient crater wall), whereas moderately shocked polymict lithic breccias with geochemical composition and 87Sr/86Sr signature similar to Ries suevite were derived from a position closer to the impact center. Thus, the inner ring of the Ries is formed by moderately shocked polymict lithic breccias likely injected into the transient crater wall during the excavation stage and weakly shocked gneiss blocks of the collapsing transient crater wall that were emplaced during the modification stage. While the presence of an overturned flap is not evident from the Erbisberg drilling, a survey of all drillings at or near the inner ring point to inverted strata throughout its outer limb. Whether the central ring of the Ries represents remains of a collapsed central peak remains to be shown. Postimpact hydrothermal alteration along the Erbisberg section comprises chloritization, sulfide veinlets, and strong carbonatization. In addition, a narrow zone in the lower parts of the polymict lithic breccia sequence shows a positive Eu anomaly in its carbonate phase. The surface expression of this hydrothermal activity, i.e., the travertine mound, comprises subaerial as well as subaquatic growth phases. Intercalated lake sediments equivalent to the early parts of the evolution of the central crater basin succession confirm a persistent impact‐generated hydrothermal activity, although for less time than previously suggested. 相似文献
212.
The change of hydrological regimes may cause impacts on human and natural system. Therefore, investigation of hydrologic alteration induced by climate change is essential for preparing timely proper adaptation to the changes. This study employed 24 climate projections from the Coupled Model Intercomparison Project Phase 5 (CMIP5) under Representative Concentration Pathway (RCP) 4.5 scenario. The climate projections were downscaled at a station‐spacing for seven Korean catchments by a statistical downscaling method that preserves a long‐term trend in climate projections. Using an ensemble of future hydrologic projections simulated by three conceptual rainfall‐runoff models (GR4J, IHACRES, and Sacramento models), we calculated Hydrologic Alteration Factors (HAFs) to investigate degrees of variations in Indicators of Hydrologic Alteration (IHAs) derived from the hydrologic projections. The results showed that the seven catchments had similar trend in terms of the HAFs for the 24 IHAs. Given that more frequent severe floods and droughts were projected over Korean catchments, sound water supply strategies are definitely required to adapt to the alteration of streamflow. A wide range of HAFs between rainfall‐runoff models for each catchment was detected by large variations in the magnitude of HAFs with the hydrologic models and the difference could be the hydrologic prediction uncertainty. There were no‐consistent tendency in the order of HAFs between the hydrologic models. In addition, we found that the alterations of hydrologic regimes by climate change are smaller as the size of catchment is larger. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
213.
214.
215.
Jin Koo Kim Jeong -Ho Park Jung Hwa Choi Kwang Ho Choi Yeong Min Choi Dae Soo Chang Young Seop Kim 《Ocean Science Journal》2007,42(2):61-67
Three barracudina fishes (Paralepididae) were newly recorded from the southern sea of Korea. Lestidium prolixum is characterized
by a single band of luminous ducts on the midventral line and absence of a papilla anterior to the eye. Lestrolepis intermedia
and L. japonica are similar in having a black papilla immediately in front of the eye and two bands of luminous ducts on the
midventral line. However, the dorsal fin of L. intermedia is located more posterior along the body than that of L. japonica,
and L. intermedia have larger number of anal fin rays 42 (vs. 36–40) and vertebrae 95 (vs. 86–87) than L. japonica. 相似文献
216.
217.
Calibration and Validation of Direction-Finding High-Frequency Radar Ocean Surface Current Observations 总被引:1,自引:0,他引:1
Jeffrey D. Paduan Kyung Cheol Kim Michael S. Cook Francisco P. Chavez 《Oceanic Engineering, IEEE Journal of》2006,31(4):862-875
This paper focuses on the validation of remotely sensed ocean surface currents from SeaSonde-type high-frequency (HF) radar systems. Hourly observations during the period July 22, 2003 through September 9, 2003 are used from four separate radar sites deployed around the shores of Monterey Bay, CA. Calibration of direction-finding techniques is addressed through the comparisons of results obtained using measured and ideal (i.e., perfect) antenna patterns. Radial currents are compared with observations from a moored current meter and from 16 surface drifter trajectories. In addition, four overwater baselines are used for radar-to-radar comparisons. Use of measured antenna patterns improves system performance in almost all cases. Antenna-pattern measurements repeated one year later at three of the four radar locations exhibit only minor changes indicating that pattern distortions are stable. Calibrated results show root-mean-square (rms) radial velocity differences in the range of 9.8-13.0 cm/s, which suggest radar observation error levels in the range of 6.9-9.2 cm/s. In most cases, clear evidence of bearing errors can be seen, which range up to 30deg for uncalibrated radar-derived radial currents and up to 15deg for currents obtained using measured antenna patterns. Bearing errors are not, however, constant with angle. The results recommend use of measured antenna patterns in all SeaSonde-type applications. They also recommend an expanded simulation effort to better describe the effects of antenna-pattern distortions on bearing determination under a variety of ocean conditions 相似文献
218.
A technique is developed to separate the incident and reflected waves propagating on a known current in a laboratory wave–current flume by analyzing wave records measured at two or more locations using a least squares method. It can be applied to both regular and irregular waves. To examine its performance, numerical tests are made for waves propagating on quiescent or flowing water. In some cases, to represent the signal noise and measurement error, white noise is superimposed on the numerically generated wave signal. For all the cases, good agreement is observed between target and estimation. 相似文献
219.
Jung Hoon Han 《The Australian geographer》2017,48(2):255-272
This paper takes a new approach to investigating people who age in place. It provides an explanation for why people age in a place that can be useful in government and corporate planning. Our research investigates the principal factors that drive the decision of a rising number of older Australians to age in place. Many older people wish to age in place rather than move in with their children or be institutionalised. They wish to continue to be active in their local communities and maintain their existing social ties. The concept of ageing in place covers two distinct groups: those who are able to stay in their current dwellings and age in home and those who move house but remain in their local community and age in neighbourhood. Age-friendly home modification is a response to ageing in home, whereas the provision of institutional healthcare and the provision of age-suitable housing to facilitate downsizing are associated with ageing in neighbourhood. Using Household, Income and Labour Dynamics in Australia (HILDA) survey data, this research examines the mobility decisions of older Australians and identifies the major determinants of a decision to age in place. This research argues for a better understanding of ageing in place, differentiating between those ageing in home and those ageing in neighbourhood. 相似文献
220.
We investigated the biogenic components (biogenic opal, calcium carbonate, and organic carbon) of the marine sediments in core TY99PC18 recovered from the southeastern part of the Ulleung Basin, East Sea (Japan Sea). Our results indicate that primary productivity by diatoms increased after the last glaciation (15,000 14C years b.p.) probably because of the onset of vertical mixing of seawater and nutrient supply from the deep water. Between 5,000 and 10,000 14C years b.p. a shift in the dominant primary producer, i.e. from diatoms to coccolithophores, coincides with decreased productivity, which could be related to the influx of warm, low-nutrient waters at that time. During the late Holocene (after 5,000 14C years b.p.) the productivity of diatoms increased once more probably due to renewed ventilation and vertical mixing. 相似文献