全文获取类型
收费全文 | 366篇 |
免费 | 20篇 |
国内免费 | 8篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 30篇 |
地球物理 | 77篇 |
地质学 | 95篇 |
海洋学 | 114篇 |
天文学 | 3篇 |
综合类 | 4篇 |
自然地理 | 63篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 15篇 |
2016年 | 12篇 |
2015年 | 14篇 |
2014年 | 14篇 |
2013年 | 30篇 |
2012年 | 12篇 |
2011年 | 16篇 |
2010年 | 18篇 |
2009年 | 15篇 |
2008年 | 28篇 |
2007年 | 30篇 |
2006年 | 26篇 |
2005年 | 21篇 |
2004年 | 13篇 |
2003年 | 12篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 16篇 |
1999年 | 15篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有394条查询结果,搜索用时 265 毫秒
161.
162.
S. Ceramicola M. Stoker D. Praeg P.M. Shannon L. De Santis R. Hoult B.O. Hjelstuen S. Laberg A. Mathiesen 《Marine and Petroleum Geology》2005,22(9-10):1045
Two-dimensional flexural backstripping and thermal modelling (assuming uniform stretching and cooling) is applied to four interpreted, depth-converted seismic profiles across the Rockall, Faroe–Shetland and Vøring basins, along 1600 km of the Atlantic continental margin of NW Europe. The results reveal a significant discrepancy between the modelled palaeo-depths for the base of the Cenozoic succession and those proven by geological evidence at control points (subaerial conditions or depositional depth ranges in wells). The discrepancy is of Rm-scale, much larger than the possible range of parameter error determined by sensitivity tests (up to 0.5 km). Assuming a Cretaceous rift episode (100 Ma), the discrepancy is at least 1.7 km in the Rockall Basin, up to 2.1 km in the Faroe–Shetland Basin and at least 1 km in the Vøring Basin (which also contains evidence of kilometre-scale uplift of the inner margin). Assuming (unproven) a second rift in the early Cenozoic (60 Ma), the discrepancy remains of kilometre-scale in the Rockall and Faroe–Shetland basins. The restorations also provide evidence of uplift, both above compressive structures and across the modelled profiles as seaward rotations of palaeo-bathymetric records. The palaeo-bathymetric discrepancy corresponds to an anomaly in subsidence that is the cumulative product of all the tectonic episodes that have affected the NW European margin, and may incorporate both permanent effects of the last episode of lithospheric extension and transient responses to the interaction of the margin with mantle convective flow. Any explanation must accommodate both the large magnitude of anomalous subsidence along the margin and evidence of its episodic character. 相似文献
163.
Induction of cytochrome P4501A in fish is a well-known indicator of exposure to polycyclic aromatic hydrocarbons (PAHs) and determination of PAH metabolites in bile by fixed wavelength fluorescence (FF) or synchronous fluorescence spectroscopy (SFS), has become an useful method in monitoring programs. In this work the relationship between cytochrome P4501A (EROD activity) and levels of biliary PAH metabolites was measured in the European eel Anguilla anguilla, in both field and laboratory conditions: organisms were sampled on a seasonal basis from the Orbetello lagoon (Tuscany) to characterize the natural variability of these biological parameters, while in laboratory eels were intraperitoneally injected with benzo[a]pyrene to investigate temporal and dose-dependent induction patterns. Results showed that induction of cytochrome P450 and accumulation of PAHs metabolites in bile are not necessarily correlated either in field, or in laboratory investigations; different seasonal changes were measured in natural conditions and slight variations in dose and time response patterns were also obtained in laboratory exposures. 相似文献
164.
165.
166.
本文初步概述饲养欧洲鳗鲡(Anguillaanguilla)的食性特征,对蛋白质的表现消化率和日粮蛋白质的需求量、驯饵、饲料形态、给饲率以及实用的欧鳗配合饲料。建议采用膨化颗粒饲料,制订欧级饲料实验方法和条件的规范。 相似文献
167.
Ledgers and landscapes: Indicators of rural landscape change in southern New Zealand, 1878–1919
下载免费PDF全文
![点击此处可从《New Zealand geographer》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Our objective was to develop and calibrate numerical measures to represent the timing and magnitude of landscape change between 1878, and 1919 using information in a stock and station agency's ledgers. Relative expenditures on fencing materials peaked in the 1880s, were lowest in the early 1900s, and rose to one‐fifth of annual expenditures from 1914 onwards. In contrast, relative expenditures on soil preparation, cropping and harvesting grew steadily after 1879, peaked in 1900, and declined from then until 1919. This research found that periods of intensive landscape investment between 1878 and 1919 were separated by longer intervals of landscape maintenance. 相似文献
168.
169.
Aiming to analyze the site conditions of treeline trees at the highest elevations, we investigated 360 km of treelines in the Upper Valtellina, Italian Alps. We analyzed approximately five trees per km and determined the environmental factors limiting treeline elevation by distinguishing between geomorphologic constraints (mean elevation 2355 m), climatic constraints (2530 m), and human impacts (2335 m). Up to 82% of the 1814 analyzed treeline trees were influenced by geomorphological constraints, whereas human impacts influenced only 3% of the trees. Climatic treelines (15% of trees) were most common in the western sector. Moreover we analyzed the frequency distributions of elevation, slope, and aspect. Elevation was the most important variable that was also strongly associated with climatic treelines. The slope variable was more strongly associated with treelines limited by geomorphology than by climate. By reconstructing the altitudinal dynamics at the Mt. Confinale study site, we found rates of an ongoing treeline upward shift of up to 2.6 m/y in the period 2000–2009. Our results indicate that climatic conditions related to the ongoing air temperature rise in this region will likely enhance the treeline shift, especially at high elevations (>2400 m a.s.l.) and on non-extreme slopes (<45°). 相似文献
170.
Kees Terlouw 《GeoJournal》2008,73(2):103-116
Subsidizing cross-border regions is a method to close the gap between citizens and the European Union. This analysis of PAMINA,
a cross-border region in the Rhine Valley near Karlsruhe, discusses some of the difficulties of this policy. There are structural
mismatches between the scales of different cross-border relations. These vertical mismatches are linked to the differences
in the horizontal logics of economic and administrative cross-border relations. Especially cross-border commuting, made possible
by European economic integration, has improved the daily life of many inhabitants of this region. Paradoxically this regional
success of European economic integration is disconnected from the EU funded cross-border region. They not only relate to different
scales, but the same spatial asymmetry generating this cross-border behaviour hinders administrative cross-border cooperation
in PAMINA.
相似文献
Kees TerlouwEmail: |