全文获取类型
收费全文 | 328篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 26篇 |
地球物理 | 81篇 |
地质学 | 92篇 |
海洋学 | 10篇 |
天文学 | 109篇 |
综合类 | 1篇 |
自然地理 | 14篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 14篇 |
2015年 | 17篇 |
2014年 | 6篇 |
2013年 | 17篇 |
2012年 | 9篇 |
2011年 | 20篇 |
2010年 | 15篇 |
2009年 | 29篇 |
2008年 | 15篇 |
2007年 | 17篇 |
2006年 | 19篇 |
2005年 | 18篇 |
2004年 | 10篇 |
2003年 | 16篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 11篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1973年 | 2篇 |
1971年 | 3篇 |
1960年 | 1篇 |
排序方式: 共有341条查询结果,搜索用时 359 毫秒
91.
92.
Karel Šilhán Rudolf Brázdil Tomáš Pánek Petr Dobrovolný Lucie Kašičková Radim Tolasz Ondřej Turský Marek Václavek 《地球表面变化过程与地形》2011,36(14):1898-1909
Rockfall is an important process in the final sculpturing of escarpments and scree slopes that originate in bedrock landslides in the Flysch Carpathians. The spatio‐temporal characteristics of rockfall activity were studied at four localities representative of old landslides in the highest part of the Czech Flysch Carpathians (Moravskoslezské Beskydy Mountains). Historical activity, chronology, and spatial context of rockfall activity were reconstructed using dendrogeomorphic techniques and rockfall rate index (RR). A total of 1132 increment cores from 283 trees growing in the rockfall transport and accumulation zones enabled the dating of 989 rockfall events. Reconstruction of a 78‐year‐long RR chronology suggests similar rockfall histories and trends at all study sites, indicating the existence of major common factors driving rockfall dynamics in the region. Temporal analysis and correlation of the RR series obtained with monthly mean temperatures, numbers of days with temperature transitions through 0 °C and monthly precipitation totals show that meteorological characteristics have evident but variable influence on rockfall activity. The most important factor is the effect of freeze–thaw cycles throughout the year, supplemented by low temperatures, especially during autumn. The influence of precipitation totals is of lesser importance. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
93.
Thomas Leipe Franz Tauber Henry Vallius Joonas Virtasalo Szymon U?cinowicz Nicole Kowalski Sven Hille Susanna Lindgren Tero Myllyvirta 《Geo-Marine Letters》2011,31(3):175-188
In this study, particulate organic carbon (POC) contents and their distribution pattern in surficial sediments of the Baltic
Sea are presented for 1,471 sampling stations. POC contents range from approx. 0.1% in shallow sandy areas up to 16% in deep
muddy basins (e.g. Gotland Basin). Some novel relationships were identified between sediment mass physical properties (dry
bulk density (DBD), grain size) and POC levels. Notably, the highest POC concentrations (about 10–17 mg cm–3) occur in sandy mud to mud (60–100% mud content) with intermediate POC contents of about 3–7% and DBDs of 0.1–0.4 g cm–3. Areas with this range in values seem to represent the optimum conditions for POC accumulation in the Baltic Sea. The maximum
POC contents (8–16%) are found in fluid mud of the central Baltic Sea characterized by extremely low DBDs (<0.1 g cm–3) and moderate POC concentrations (4–7 mg cm–3). Furthermore, sediment mass accumulation rates (MAR), based on 210Pb and 137Cs measurements and available for 303 sites of the Baltic Sea, were used for assessing the spatial distribution of POC burial
rates. Overall, these vary between 14 and 35 g m–2 year–1 in the mud depositional areas and, in total, at least 3.5 (±2.9) Mt POC are buried annually. Distribution patterns of POC
contents and burial rates are not identical for the central Baltic Sea because of the low MAR in this area. The presented
data characterize Baltic Sea sediments as an important sink for organic carbon. Regional differences in organic carbon deposition
can be explained by the origin and transport pathways of POC, as well as the environmental conditions prevailing at the seafloor
(morphology, currents, redox conditions). These findings can serve to improve budget calculations and modelling of the carbon
cycle in this large brackish-water marginal sea. 相似文献
94.
David L. McCollum Volker Krey Keywan Riahi Peter Kolp Arnulf Grubler Marek Makowski Nebojsa Nakicenovic 《Climatic change》2013,119(2):479-494
This paper assesses three key energy sustainability objectives: energy security improvement, climate change mitigation, and the reduction of air pollution and its human health impacts. We explain how the common practice of narrowly focusing on singular issues ignores potentially enormous synergies, highlighting the need for a paradigm shift toward more holistic policy approaches. Our analysis of a large ensemble of alternate energy-climate futures, developed using MESSAGE, an integrated assessment model, shows that stringent climate change policy offers a strategic entry point along the path to energy sustainability in several dimensions. Concerted decarbonization efforts can lead to improved air quality, thereby reducing energy-related health impacts worldwide: upwards of 2–32 million fewer disability-adjusted life years in 2030, depending on the aggressiveness of the air pollution policies foreseen in the baseline. At the same time, low-carbon technologies and energy-efficiency improvements can help to further the energy security goals of individual countries and regions by promoting a more dependable, resilient, and diversified energy portfolio. The cost savings of these climate policy synergies are potentially enormous: $100–600 billion annually by 2030 in reduced pollution control and energy security expenditures (0.1–0.7 % of GDP). Novel aspects of this paper include an explicit quantification of the health-related co-benefits of present and future air pollution control policies; an analysis of how future constraints on regional trade could influence energy security; a detailed assessment of energy expenditures showing where financing needs to flow in order to achieve the multiple energy sustainability objectives; and a quantification of the relationships between different fulfillment levels for energy security and air pollution goals and the probability of reaching the 2 °C climate target. 相似文献
95.
This paper presents a new method which allows for the automatic extraction and tracking of the evolution of filaments in solar images. Series of Hα full-disk images are taken in regular time intervals to observe the changes of the solar disk features. In each picture, the solar chromosphere filaments are identified for further evolution examination. Two alternative preprocessing techniques converting grayscale images into black-and-white pictures with enhanced chromosphere granularity are examined: local thresholding based on median values and global thresholding with brightness and area normalization. The next step employs morphological closing operations with multi-directional linear structuring elements to extract elongated shapes in the image. After logical intersection of directional filtering results, remaining noise is removed from the final outcome using morphological dilation and erosion with a circular structuring element. Experimental results show that the developed technique can achieve excellent results in detecting large filaments and good detection rates for small filaments. 相似文献
96.
97.
Nonstandard theories of fundamental interactions typically predict the existence of new kinds of weakly interacting particles.
These can escape freely from stellar interiors and act as additional source of cooling. Considerable agreement of a variety
of astrophysical observations with standard physics can serve as a source of constraints on non-standard ideas. In this paper
we consider G117-B15A pulsating white dwarf for which the secular rate, at which the period of its fundamental mode increases,
has been accurately measured. This star has been claimed the most stable oscillator ever recorded in the optical band. Because
an additional channel of energy loss would speedup the cooling rate, one is able to use this stability to derive a bound on
axion mass and on theories with large extra dimensions. We also point to the possibility of using similar arguments to constrain
supersymmetric paticles.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
98.
Pavel Mayer Marek Wolf P. G. Niarchos K. D. Gazeas V. N. Manimanis Drahomír Chochol 《Astrophysics and Space Science》2006,304(1-4):39-41
New precise times of minimum light for several early-type eclipsing binaries were obtained at three observatories. The changes of period of the following measured binaries are discussed: V1182 Aql, LY Aur, SZ Cam, FZ CMa, QZ Car, LZ Cen, V606 Cen, AH Cep and TU~Mus. 相似文献
99.
100.