全文获取类型
收费全文 | 2679篇 |
免费 | 125篇 |
国内免费 | 13篇 |
专业分类
测绘学 | 221篇 |
大气科学 | 185篇 |
地球物理 | 722篇 |
地质学 | 908篇 |
海洋学 | 142篇 |
天文学 | 473篇 |
综合类 | 31篇 |
自然地理 | 135篇 |
出版年
2024年 | 12篇 |
2023年 | 24篇 |
2022年 | 24篇 |
2021年 | 50篇 |
2020年 | 67篇 |
2019年 | 47篇 |
2018年 | 155篇 |
2017年 | 115篇 |
2016年 | 186篇 |
2015年 | 158篇 |
2014年 | 178篇 |
2013年 | 208篇 |
2012年 | 172篇 |
2011年 | 170篇 |
2010年 | 146篇 |
2009年 | 149篇 |
2008年 | 109篇 |
2007年 | 84篇 |
2006年 | 83篇 |
2005年 | 55篇 |
2004年 | 74篇 |
2003年 | 57篇 |
2002年 | 51篇 |
2001年 | 49篇 |
2000年 | 31篇 |
1999年 | 23篇 |
1998年 | 48篇 |
1997年 | 29篇 |
1996年 | 18篇 |
1995年 | 23篇 |
1994年 | 22篇 |
1993年 | 10篇 |
1992年 | 18篇 |
1991年 | 13篇 |
1990年 | 21篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1985年 | 13篇 |
1984年 | 4篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1972年 | 9篇 |
1965年 | 3篇 |
1950年 | 4篇 |
排序方式: 共有2817条查询结果,搜索用时 15 毫秒
51.
Ramón Piedrafita Rubén Béjar Rubén Blasco Alvaro Marco F. Javier Zarazaga-Soria 《International Journal of Digital Earth》2018,11(8):761-782
In the current world, it is easy to listen that everybody and everything is connected. Over this connected world, the concept of location-based services has grown in order to provide digital services in everyplace and at every time. Nevertheless, this is not 100% true because the connection is not guaranteed for many people and in many places. These are the Degraded Communications Environments (DCE), environments where the availability of high-speed communications is not guaranteed in at least the 75% of the time. This paper works over the experience of a previous work in developing light protocols that do not need broadband for communication. This work provides an extension of these protocols for the inclusion of mobile devices as elements of the communication process and a set of libraries to allow the development of applications in DCE. The work done has involved the development of two frameworks: an Android framework that makes the incorporation of Android devices easier and a server-based framework that provides the server side for the development of the referred applications. A use case that uses these two frameworks has been developed. Finally, all technology developed is available throw a public Git repository. 相似文献
52.
Paola Tuccimei Michele Soligo Joaquin Ginés Angel Ginés Joan Fornós Jan Kramers Igor Maria Villa 《地球表面变化过程与地形》2010,35(7):782-790
Phreatic overgrowths on speleothems (POS) are carbonate formations deposited at the water table of caves in unique karstic coastal settings having morphologies that can be directly related to sea level at the time of formation. The U‐Th ages of calcite and aragonite overgrowths collected from the modern water table in coastal caves on Mallorca (Cova de Cala Varques A and Cova des Pas de Vallgornera) were determined using high‐precision MC‐ICPMS techniques. U‐Th ages indicate that phreatic carbonate deposition occurred between ca 2·8 and at least 0·6 ka BP and are in accord with an archeologically estimated age of 3·7–3·0 ka BP for a drowned prehistoric construction at a depth of 1 m below current sea level in a cave from the same area. Speleothem δ13C and δ18O and chemical composition of cave pools provide supportive evidence that POS reflect mixing between seawater and brackish water table. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
53.
We consider the advantages of a formalism based on concept of the asymmetric continuum and we present some equivalence theorems
relating it to the asymmetric elasticity and to micropolar and micromorphic theories as founded by Nowacki, Cosserats and
Eringen.
We consider the basic processes in an asymmetric continuum which could be reduced to the point basic motions/deformations.
The co-action of spin and shear motions is assumed to play the main role in fracturing process, while the constitutive relation
between the antisymmetric stresses and rotations replaces the friction constitutive law. 相似文献
54.
József Ádám 《Journal of Geodesy》1982,56(3):180-195
The Euclidean spaces with their inner products are used to describe methods of least squares adjustment as orthogonal projections
on finite-dimensional subspaces. A unified Euclidean space approach to the least squares adjustment methods “observation equations”
and “condition equations” is suggested. Hence not only the two adjustment solutions are treated from the view-point of Euclidean
space theory in a unified frame but also the existing duality relation between the methods of “observation equations” and
“condition equations” is discussed in full detail. Another purpose of this paper is to contribute to the development of some
familiarity with Euclidean and Hilbert space concepts. We are convinced that Euclidean and Hilbert space techniques in least
squares adjustment are elegant and powerful geodetic methods. 相似文献
55.
R. Bachiller V. Bujarrabal J. Martín-Pintado R. Planesas J. Gómez-González 《Astrophysics and Space Science》1990,171(1-2):195-198
We review our recent results concerning the molecular gas content of young planetary nebulae NGC 2346, M 2–9, and NGC 6720 (the Ring Nebula in Lyra).Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
56.
57.
58.
Hydrogeology and sustainable future groundwater abstraction from the Agua Verde aquifer in the Atacama Desert,northern Chile 总被引:1,自引:0,他引:1
Javier Urrutia Jorge Jódar Agustín Medina Christian Herrera Guillermo Chong Harry Urqueta José A. Luque 《Hydrogeology Journal》2018,26(6):1989-2007
The hyper-arid conditions prevailing in Agua Verde aquifer in northern Chile make this system the most important water source for nearby towns and mining industries. Due to the growing demand for water in this region, recharge is investigated along with the impact of intense pumping activity in this aquifer. A conceptual model of the hydrogeological system is developed and implemented into a two-dimensional groundwater-flow numerical model. To assess the impact of climate change and groundwater extraction, several scenarios are simulated considering variations in both aquifer recharge and withdrawals. The estimated average groundwater lateral recharge from Precordillera (pre-mountain range) is about 4,482 m3/day. The scenarios that consider an increase of water withdrawal show a non-sustainable groundwater consumption leading to an over-exploitation of the resource, because the outflows surpasses inflows, causing storage depletion. The greater the depletion, the larger the impact of recharge reduction caused by the considered future climate change. This result indicates that the combined effects of such factors may have a severe impact on groundwater availability as found in other groundwater-dependent regions located in arid environments. Furthermore, the scenarios that consider a reduction of the extraction flow rate show that it may be possible to partially alleviate the damage already caused to the aquifer by the continuous extractions since 1974, and it can partially counteract climate change impacts on future groundwater availability caused by a decrease in precipitation (and so in recharge), if the desalination plant in Taltal increases its capacity. 相似文献
59.
Túri Marianna Hubay Katalin Molnár Mihály Braun Mihály László Elemér Futó István Palcsu László 《Journal of Paleolimnology》2021,66(3):229-248
Journal of Paleolimnology - We measured stable isotopes (δ18O and δ13C) in Sphagnum cellulose that was extracted from a long peat core drilled in the ombrotrophic Mohos peat bog, Ciomadul... 相似文献
60.
U. J. López-Chuken U. López-Domínguez R. Parra-Saldivar E. Moreno-Jiménez L. Hinojosa-Reyes J. L. Guzmán-Mar E. Olivares-Sáenz 《International Journal of Environmental Science and Technology》2012,9(1):69-77
Chloride salinity has been strongly related to enhanced cadmium (Cd) uptake by plants due to increased solubility in the soil solution, even in agricultural soil with very low levels of cadmium. This finding is relevant because the cadmium content of food crops is an important concern for human health. Therefore, the aim of this study was to predict and discuss the chlorine-enhanced uptake of cadmium by two common crops: maize and tobacco under ??non-saline?? (1?mM) and ??very strongly saline?? (200?mM) scenarios using a modified ??biotic ligand model?? and datasets from a set of soil and hydroponic experiments. Results indicated that predicted cadmium uptake rates (expressed as cadmium in plant ??mol?m?2 root) by maize and tobacco plants were consistently higher (54 and 15%, respectively) assuming conditions of ??very strong salinity?? soil compared to the simulated ??non-saline?? soil. In the light of the results of the present research, valuable information is given on modeled cadmium phytoavailability as an indication of the potential risk due to increased cadmium uptake by crops under saline conditions, especially as the enhancement of cadmium uptake in the presence of Cl? salinity may be a general trend that occurs in many edible crops. The biotic ligand model parameterization applied in the present study attempted to simulate conditions commonly found in natural cadmium and salt-affected soils. However, caution is needed to extrapolate results obtained from these models to real soil conditions. 相似文献