全文获取类型
收费全文 | 1357篇 |
免费 | 44篇 |
国内免费 | 14篇 |
专业分类
测绘学 | 29篇 |
大气科学 | 105篇 |
地球物理 | 351篇 |
地质学 | 570篇 |
海洋学 | 111篇 |
天文学 | 148篇 |
综合类 | 5篇 |
自然地理 | 96篇 |
出版年
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 26篇 |
2017年 | 29篇 |
2016年 | 45篇 |
2015年 | 29篇 |
2014年 | 33篇 |
2013年 | 80篇 |
2012年 | 47篇 |
2011年 | 73篇 |
2010年 | 74篇 |
2009年 | 77篇 |
2008年 | 61篇 |
2007年 | 62篇 |
2006年 | 58篇 |
2005年 | 82篇 |
2004年 | 62篇 |
2003年 | 42篇 |
2002年 | 44篇 |
2001年 | 41篇 |
2000年 | 22篇 |
1999年 | 30篇 |
1998年 | 24篇 |
1997年 | 10篇 |
1996年 | 21篇 |
1995年 | 16篇 |
1994年 | 17篇 |
1993年 | 12篇 |
1992年 | 19篇 |
1991年 | 11篇 |
1990年 | 17篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 16篇 |
1985年 | 17篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 16篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 4篇 |
1974年 | 13篇 |
1973年 | 6篇 |
1963年 | 4篇 |
排序方式: 共有1415条查询结果,搜索用时 375 毫秒
821.
Current activities and recent progress on constructive approximation and numerical analysis in physical geodesy are reported
upon. Two major topics of interest are focused upon, namely trial systems for purposes of global and local approximation and
methods for adequate geodetic application. A fundamental tool is an uncertainty principle, which gives appropriate bounds
for the quantification of space and momentum localization of trial functions. The essential outcome is a better understanding
of constructive approximation in terms of radial basis functions such as splines and wavelets.
Received: 4 May 1999 / Accepted: 21 May 1999 相似文献
822.
Jean-Jacques Schott Michel Roussignol Michel Menvielle & Flavien R. Nomenjahanary 《Geophysical Journal International》1999,138(3):769-783
In this paper, we will report on the application of Bayesian inference to DC resistivity inversion for 1-D multilayer models. The posterior probability distribution is explored through a Markov process based upon a Gibbs's sampler. The process would lead to unrealistic estimates without additional prior information, which takes the form of a second Markov chain where the transition kernel corresponds to a smoothness constraint. The outcomes are posterior marginal probabilites for each parameter, as well as, if required, joint probabilities for pairs of parameters. We will discuss the main properties of the method in the light of a theoretical example and illustrate its capabilities with some field examples taken from various contexts. 相似文献
823.
Vincent Bichet Michel Campy Jean-Franois Buoncristiani Christian Digiovanni Michel Meybeck Herv Richard 《Quaternary Research》1999,51(3):267
The Upper Doubs River Valley is a 910-km2watershed feeding into Lake Chaillexon. The lake was formed by a natural rockfall at the end of the Bølling Chronozone (around 14,250 cal yr B.P.) and since then has trapped material eroded from the watershed. The filling process and variations in sediment yield have been investigated by mechanical coring, seismic surveys, and electric soundings. The detrital sediment yield of the upstream watershed can be calculated by quantifying the sedimentary stocks for each climatic stage of the Late-Glacial period and Holocene Epoch and estimating the lake's entrapment capacity. This enables us to determine the intensity of the erosion processes in relation to climate and environmental factors. The Bølling–Allerød Interstade produced the greatest yields with mean values of 19,500 metric tons per calendar year (t/yr). The Younger Dryas Chronozone saw a sharp fall (8900 t/yr) that continued into the Preboreal (2100 t/yr). Clastic supply increased during the Boreal (4500 t/yr) before declining again in the Early Atlantic (2400 t/yr). Since then, yields have risen from 4500 t/yr in the Late Atlantic to 6800 t/yr in the Subboreal and 11,100 t/yr in the Subatlantic. Comparison of quantitative data with the qualitative analysis of the deposits and with the paleohydrologic curve of the watershed based on level fluctuations in lakes around Chaillexon shows that climate was the controlling factor of sediment yield until the Late Atlantic. From the Late Atlantic–Subboreal around 5400 cal yr B.P. (470014C yr B.P.) and especially from the end of the Subboreal Chronozone and during the Subatlantic Chronozone (2770 cal yr B.P./270014C yr B.P.–present) climatic constraints have been compounded by human activity related to forest clearing and land use. 相似文献
824.
Plomerová Jaroslava Granet Michel Judenherc Sebasten Achauer Ulrich Babuška Vladislav Jedlička Petr Kouba Daniel Vecsey Luděk 《Studia Geophysica et Geodaetica》2000,44(2):195-209
We present the first results of a comparison of deep lithosphere structure of three Variscan massifs - the Armorican Massif, French Massif Central and Bohemian Massif, as revealed by recent tomographic studies of seismic anisotropy. The data originate from several field measurements made in temporary arrays of stations equipped with both short-period and broadband seismometers with digital recording. The study is based on teleseismic body waves and a joint inversion of anisotropic data (P-residual spheres, the fast shear-wave polarizations and split times) and demonstrates that the three Variscan massifs appear to consist of at least two parts with different orientation of large-scale fabric derived from seismic anisotropy. The boundaries of anisotropic lithospheric domains are related to prominent tectonic features recognised on the surface as sutures, shear zones or transfer fault zones, as well as grabens, thus indicating that some of them extend deep through the entire lithosphere. 相似文献
825.
Judith Sippel Aline Saintot Michel Heeremans Magdalena Scheck-Wenderoth 《Marine and Petroleum Geology》2010
The geodynamic history of a region is archived in its geologic record which, in turn, may reflect deformation patterns that causally can be related to certain configurations of paleostresses. In the Oslo Region, the exposed geological record ranges from Precambrian high-grade metamorphic rocks through Cambro-Silurian sedimentary rocks to Permo-Carboniferous sedimentary and magmatic rocks, the latter being related to the development of the Oslo rift system. We investigate the kinematics of outcrop-scale faults to derive the diversity of paleostress states responsible for the observed strain. For this purpose, we combine different graphical and numerical approaches to separate heterogeneous fault-slip data sets and estimate the associated reduced stress tensors. A reduced stress tensor consists of the directions of the three principal stress axes with σ1 ≥ σ2 ≥ σ3 and the ratio of principal stress differences, R = (σ2 − σ3)/(σ1 − σ3). 相似文献
826.
Succint results of recent geomorphological research conducted by a Canadian team from Université Laval (Quebec city) in the Khabur valley of northeastern Syria confirms the hypothesis put forward by one of the authors concerning the function of the tell 'Atij site during the Early Bronze Age period (3000–2500 B. C.). The detailed study of a stratigraphically controlled cross section of 25 m × 6 m, on the abrupt western side of the main tell of the site, combined with observations made in a trench linking the principal tell to the secondary one showed that these two tells, now forming 'Atij, were small islands on the ancient Khabur River. At the time of their occupation, i. e., the first half of the 3rd millenium, the Khabur was wider, deeper and navigable. Another investigation trench, 400 m N. E. of the main tell, disproved the suggested existence of an ancient irrigation canal in the area. © 1994 John Wiley & Sons, Inc. 相似文献
827.
Valérie Ballu Jérome Ammann Olivier Pot Olivier de Viron Glenn S. Sasagawa Gilles Reverdin Marie-Noelle Bouin Mathilde Cannat Christine Deplus Sébastien Deroussi Marcia Maia Michel Diament 《Journal of Geodesy》2009,83(2):147-159
Decades of cruise-based exploration have provided excellent snapshots of the structure of mid-ocean ridges and have revealed
that accretion is a mixture of steady-state and quantum events. Observatory-type studies are now needed to quantify the temporal
evolution of these systems. A multi-disciplinary seafloor observatory site is currently being set up at the Lucky Strike volcano,
in the axial valley of the slow spreading Mid-Atlantic ridge as a part of the MoMAR (monitoring of the Mid-Atlantic Ridge)
initiative. The aim of this observatory is to better understand the dynamics of the volcano and the hydrothermal vents hosted
at its summit as well as their plumbing systems. In August 2006, the GRAVILUCK cruise initiated an experiment to monitor the
deformation of Lucky Strike volcano. A geodetic network was installed, and seafloor pressure, gravity and magnetic data were
collected. In this paper, we present the method used to monitor volcanic deformation, which involves measuring relative depth
difference between points within a seafloor geodesy network. We show that, taking into account oceanographic variability and
measurement noise, the network should be able to detect vertical deformations of the order of 1 cm. 相似文献
828.
829.
Previous field and laboratory studies have identified the alga Lobophora variegata as a good candidate for biomonitoring metal contamination in the New Caledonia lagoon which is subjected to intensive and extensive metal inputs from land-based mining activities. The aim of this work was to further assess the bioindicative potential of this species by investigating, in the field, its bioaccumulation capacity for local key contaminants, i.e. Ag, As, Cd, Co, Cr, Cu, Mn, Ni and Zn. Algae from clean and contaminated sites were cross-transplanted for a period of three months in order to determine the in situ uptake and depuration kinetics of the nine elements. Results indicate that algae transplanted to the contaminated site displayed a significant linear increase in concentration with time for Ag, As, Cd, Co, Cr, Cu, Mn and Ni. In contrast, algae transplanted to the clean site did not show major depuration of these elements, except for Co. Overall, L. variegata showed a rapid temporal response in metal uptake, especially for the elements intensively released into the coastal environment of New Caledonia (viz., Co, Cr, Mn and Ni). This species appears therefore as an excellent bioindicator species of metal contamination in this area. Our results also provide background information necessary for using L. variegata under in situ experimental conditions so as to provide better quantitative information on ambient metal contamination levels. The wide distribution of L. variegata in tropical areas further enhances its potential as a bioindicator species of metal contamination in other tropical coastal environments. 相似文献
830.
膜蛋白是生物领域研究中的热点和难点。在光合作用研究中,对于藻类个体发育过程中光合膜蛋白结构和功能的变化所知甚少,其中的一个限制因素是能否纯化得到大量高活性的稳定且均一的光合膜蛋白。作者从条斑紫菜(Porphyra yezoensis)孢子体和配子体中分离纯化得到光合系统(PSⅡ)复合物,并研究了其完整性和放氧活性。结果表明,孢子体和配子体的PSⅡ复合物,在4℃条件下保存比在-80℃下保存放氧活性高,稳定性高。配子体PSⅡ复合物,在-80℃保存第6天就已经没有放氧活性,而孢子体PSⅡ复合物仍有放氧活性。对4℃下保存的PSII复合物进行分子筛柱层析,室温吸收光谱测定以及放氧活性测定,发现随着放氧活性逐渐降低,蛋白大分子有聚合现象。室温吸收光谱表明经过长期的保存,吸收峰向短波长方向偏移,叶绿素易降解成为脱镁叶绿素 相似文献