全文获取类型
收费全文 | 3226篇 |
免费 | 126篇 |
国内免费 | 19篇 |
专业分类
测绘学 | 114篇 |
大气科学 | 359篇 |
地球物理 | 662篇 |
地质学 | 1020篇 |
海洋学 | 347篇 |
天文学 | 612篇 |
综合类 | 4篇 |
自然地理 | 253篇 |
出版年
2023年 | 10篇 |
2022年 | 12篇 |
2021年 | 33篇 |
2020年 | 47篇 |
2019年 | 47篇 |
2018年 | 91篇 |
2017年 | 67篇 |
2016年 | 119篇 |
2015年 | 67篇 |
2014年 | 103篇 |
2013年 | 151篇 |
2012年 | 146篇 |
2011年 | 180篇 |
2010年 | 147篇 |
2009年 | 215篇 |
2008年 | 199篇 |
2007年 | 165篇 |
2006年 | 141篇 |
2005年 | 120篇 |
2004年 | 130篇 |
2003年 | 121篇 |
2002年 | 105篇 |
2001年 | 81篇 |
2000年 | 90篇 |
1999年 | 78篇 |
1998年 | 92篇 |
1997年 | 56篇 |
1996年 | 52篇 |
1995年 | 34篇 |
1994年 | 30篇 |
1993年 | 37篇 |
1992年 | 25篇 |
1991年 | 37篇 |
1990年 | 15篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1987年 | 23篇 |
1986年 | 11篇 |
1985年 | 23篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 14篇 |
1975年 | 14篇 |
1973年 | 9篇 |
排序方式: 共有3371条查询结果,搜索用时 31 毫秒
1.
Hydrological trends and the evolution of catchment research in the Alptal valley,central Switzerland
Manfred Stähli Jan Seibert James W. Kirchner Jana von Freyberg Ilja van Meerveld 《水文研究》2021,35(4):e14113
When the observation of small headwater catchments in the pre-Alpine Alptal valley (central Switzerland) started in the late 1960s, the researchers were mainly interested in questions related to floods and forest management. Investigations of geomorphological processes in the steep torrent channels followed in the 1980s, along with detailed observations of biogeochemical and ecohydrological processes in individual forest stands. More recently, research in the Alptal has addressed the impacts of climate change on water supply and runoff generation. In this article, we describe, for the first time, the evolution of catchment research at Alptal, and present new analyses of long-term trends and short-term hydrologic behaviour. Hydrometeorological time series from the past 50 years show substantial interannual variability, but only minimal long-term trends, except for the ~2°C increase in mean annual air temperature over the 50-year period, and a corresponding shift towards earlier snowmelt. Similar to previous studies in larger Alpine catchments, the decadal variations in mean annual runoff in Alptal's small research catchments reflect the long-term variability in annual precipitation. In the Alptal valley, the most evident hydrological trends were observed in late spring and are related to the substantial change in the duration of the snow cover. Streamflow and water quality are highly variable within and between hydrological events, suggesting rapid shifts in flow pathways and mixing, as well as changing connectivity of runoff-generating areas. This overview illustrates how catchment research in the Alptal has evolved in response to changing societal concerns and emerging scientific questions. 相似文献
2.
3.
4.
5.
Anita Enmark Thomas Berkefeld Oskar von der Lühe Torben Andersen 《Experimental Astronomy》2006,21(2):87-99
A simulation model of the adaptive optics of the German Vacuum Tower Telescope (VTT), Observatorio del Teide, Tenerife, is
presented. The model uses modules from the integrated model of the Euro50 extremely large telescope, and includes submodels
of a Shack-Hartmann wavefront sensor, a de-formable mirror, a tip-tilt mirror, high-voltage amplifier low-pass filters, a
reconstructor and a controller. We investigate the impact on the closed loop bandwidth of changes in controller configuration
and certain system parameters, such as low pass filter bandwidth and camera integration and readout time. Control strategies
were tested on simple models before implementation on the full VTT model. Using the models, different control strategies are
compared. 相似文献
6.
7.
8.
9.
Jaap Tinbergen 《Astrophysics and Space Science》2003,288(1-2):3-14
Measurement of circular polarization is mostly looked upon as a specialist craft, applied by polarization freaks to answer uninteresting questions. This paper attempts to correct that view: some important questions can only be tackled by circular polarimetry, there is nothing very special about Stokes V and its measurement is entirely analogous to that of Q and U.Radio and optical polarimetry are covered, using both single telescopes and interferometers. 相似文献
10.
Andrew Mennim Richard A. Battye Carsten van de Bruck 《Astrophysics and Space Science》2003,283(4):633-638
We discuss the problems faced in trying to deduce the evolution of cosmological perturbations in brane-world models. There
are two natural ways to formulate the problem: one which makes the equations of motion simple and the other which makes the
boundary condition simple. Unfortunately the problem is difficult to solve, even numerically, in either formalism. We present
a more phenomenological approach which, while it does not solve the problem for any given model, illustrates some generic
features one might expect to see in the tensor part of the cosmic microwave background power spectrum. We find that the observed
scale invariance of the cosmic microwave background provides bounds on brane world models.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献