全文获取类型
收费全文 | 725篇 |
免费 | 30篇 |
国内免费 | 12篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 63篇 |
地球物理 | 124篇 |
地质学 | 228篇 |
海洋学 | 74篇 |
天文学 | 118篇 |
综合类 | 2篇 |
自然地理 | 151篇 |
出版年
2021年 | 6篇 |
2020年 | 14篇 |
2019年 | 10篇 |
2018年 | 19篇 |
2017年 | 23篇 |
2016年 | 27篇 |
2015年 | 18篇 |
2014年 | 25篇 |
2013年 | 29篇 |
2012年 | 29篇 |
2011年 | 37篇 |
2010年 | 36篇 |
2009年 | 30篇 |
2008年 | 36篇 |
2007年 | 45篇 |
2006年 | 39篇 |
2005年 | 27篇 |
2004年 | 35篇 |
2003年 | 23篇 |
2002年 | 16篇 |
2001年 | 11篇 |
2000年 | 20篇 |
1999年 | 25篇 |
1998年 | 24篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 13篇 |
1980年 | 6篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1970年 | 2篇 |
1967年 | 3篇 |
排序方式: 共有767条查询结果,搜索用时 15 毫秒
71.
Two-phase flow in fractured rock is an important phenomenon for a range of practical problems, not the least of which is
non-aqueous phase liquid (NAPL) contamination of groundwater. Although multiphase systems have long been studied in the petroleum
field, in the hydrogeological field progress has only just reaches the point where models are being developed. Scale effect
is one of the main issues of concern. Although models presented in this paper have the potential to provide useful predictions,
they can only be used to investigate a variety of possible scenarios with parameters being specified in the form of distribution
of values. The calibration and validation of all but the simplest of these models poses a formidable task, with great demands
on hydrogeologists and geophysicists to provide adequate data.
Received: 20 May 1996 · Accepted: 19 August 1996 相似文献
72.
73.
74.
Simon Johnston Roger W. Romani 《Monthly notices of the Royal Astronomical Society》2002,332(1):109-115
We have carried out a survey for 'giant pulses' in six young, Vela-like pulsars. In no cases did we find single pulses with flux densities more than 10 times the mean flux density. However, in PSR B1706–44 we have detected giant micro-pulses very similar to those seen in the Vela pulsar. In PSR B1706–44 these giant micro-pulses appear on the trailing edge of the profile and have an intrinsic width of ∼1 ms. The cumulative probability distribution of their intensities is best described by a power law. If the power law continues to higher intensities, then 3.7×106 rotations are required to obtain a pulse with 20× the mean pulse flux. This number is similar to the giant pulse rate in PSR B1937+21 and PSR B1821–24 but significantly higher than that for the Crab. 相似文献
75.
76.
Probabilistic estimates of future changes in California temperature and precipitation using statistical and dynamical downscaling 总被引:1,自引:0,他引:1
David W. Pierce Tapash Das Daniel R. Cayan Edwin P. Maurer Norman L. Miller Yan Bao M. Kanamitsu Kei Yoshimura Mark A. Snyder Lisa C. Sloan Guido Franco Mary Tyree 《Climate Dynamics》2013,40(3-4):839-856
Sixteen global general circulation models were used to develop probabilistic projections of temperature (T) and precipitation (P) changes over California by the 2060s. The global models were downscaled with two statistical techniques and three nested dynamical regional climate models, although not all global models were downscaled with all techniques. Both monthly and daily timescale changes in T and P are addressed, the latter being important for a range of applications in energy use, water management, and agriculture. The T changes tend to agree more across downscaling techniques than the P changes. Year-to-year natural internal climate variability is roughly of similar magnitude to the projected T changes. In the monthly average, July temperatures shift enough that that the hottest July found in any simulation over the historical period becomes a modestly cool July in the future period. Januarys as cold as any found in the historical period are still found in the 2060s, but the median and maximum monthly average temperatures increase notably. Annual and seasonal P changes are small compared to interannual or intermodel variability. However, the annual change is composed of seasonally varying changes that are themselves much larger, but tend to cancel in the annual mean. Winters show modestly wetter conditions in the North of the state, while spring and autumn show less precipitation. The dynamical downscaling techniques project increasing precipitation in the Southeastern part of the state, which is influenced by the North American monsoon, a feature that is not captured by the statistical downscaling. 相似文献
77.
Research on geoengineering – deliberate management of the Earth’s climate system – is being increasingly discussed within the science and policy communities. While justified as necessary in order to expand the range of options available to policy makers in the future, geoengineering research has already engendered public controversy. Proposed projects have been protested or cancelled, and calls for a governance framework abound. In this paper, we consider the reasons why geoengineering research might be subject to additional governance and suggest mechanisms that might be usefully applied in developing such a framework. We consider criteria for governance as raised by a review of the growing literature on geoengineering and other controversial scientific topics. We suggest three families of concern that any governance research framework must respond to: the direct physical risks of the research; the transparency and responsibility in decision making for the research; and the larger societal meanings of the research. We review what mechanisms might be available to respond to these three families of concern, and consider how these might apply to geoengineering research. 相似文献
78.
79.
80.