全文获取类型
收费全文 | 172篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 19篇 |
地球物理 | 59篇 |
地质学 | 54篇 |
海洋学 | 13篇 |
天文学 | 32篇 |
自然地理 | 15篇 |
出版年
2023年 | 1篇 |
2021年 | 10篇 |
2020年 | 14篇 |
2019年 | 16篇 |
2018年 | 7篇 |
2017年 | 17篇 |
2016年 | 13篇 |
2015年 | 14篇 |
2014年 | 13篇 |
2013年 | 14篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 8篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1997年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有196条查询结果,搜索用时 31 毫秒
21.
Global climate negotiations have been characterized by a divide between developed and developing nations – a split which has served as a persistent barrier to international agreement within the United Nations Framework Convention on Climate Change process. Notable progress in bridging this division was achieved at the 21st Conference of the Parties meeting in Paris through the introduction of Intended Nationally Determined Contributions (INDCs). However, the collective ambition of submitted INDCs falls short of a global 2°C target, requiring an effective ratchet mechanism to review and increase national commitments. Inequitable distribution of additional responsibilities risks re-opening historic divisions between parties. This article presents a flexible ratchet framework which shares mitigation commitments on the basis of per capita equity in line with emerging requirements for a 2°C target. The framework has been designed through convergence between developed and developing nations; developed nation targets are based on an agreed standardized percentage reduction wherever emissions are above per capita equity; developing nations are required to peak emissions at or below per capita equity levels by an agreed convergence date. The proposed framework has the flexibility to be integrated with current INDCs and to evolve in line with shifting estimates of climate sensitivity.Policy relevanceThe outcome of the 21st Conference of the Parties (COP21) negotiations in Paris offered mixed results in terms of level of ambition and submitted national commitments. A global agreement to keep average global temperature rise below two degrees was maintained; however, current pledged Intended Nationally Determined Contributions (INDCs) are projected to result in an average warming of close to three degrees. The implementation of a global ratchet mechanism to scale-up national commitments will remain key to closing this ambition gap to reach this two degree target. How this upscaling of responsibility is shared between parties will be a defining discussion point within future negotiations. This study presents a standardized, equity-based framework for how this ratchet mechanism can be implemented – a framework designed to be flexible for evolution in line with better understanding of climate sensitivity, and adaptable for integrations with current INDC proposals. 相似文献
22.
In this paper, we investigate the energy spectra produced by a simple test particle X-point model of a solar flare for different
configurations of the initial electromagnetic field. We find that once the reconnection electric field is larger than 1 Vm-1 the particle distribution transits from a heated one to a partially accelerated one. As we close the separatrices of the
X-point and the angle in the inflow direction widens we find that more particles are accelerated out of the thermal distribution
and this power–law component extends to lower energies. When we introduce a guiding magnetic field component we find that
more particles are energised, but only up to a maximum energy dictated primarily by the reconnection electric field. Despite
being able to accelerate particles to observable energies and demonstrate behaviour in the energy spectra that is consistent
with observations, this single X-line model can only deliver the number fluxes required for microflares. 相似文献
23.
A. Rob MacKenzie Stefan Krause Kris M. Hart Richard M. Thomas Phillip J. Blaen R. Liz Hamilton Giulio Curioni Susan E. Quick Angeliki Kourmouli David M. Hannah Sophie A. Comer-Warner Nicolai Brekenfeld Sami Ullah Malcolm C. Press 《水文研究》2021,35(3):e14096
The ecosystem services provided by forests modulate runoff generation processes, nutrient cycling and water and energy exchange between soils, vegetation and atmosphere. Increasing atmospheric CO2 affects many linked aspects of forest and catchment function in ways we do not adequately understand. Global levels of atmospheric CO2 will be around 40% higher in 2050 than current levels, yet estimates of how water and solute fluxes in forested catchments will respond to increased CO2 are highly uncertain. The Free Air CO2 Enrichment (FACE) facility of the University of Birmingham's Institute of Forest Research (BIFoR) is the only FACE in mature deciduous forest. The site specializes in fundamental studies of the response of whole ecosystem patches of mature, deciduous, temperate woodland to elevated CO2 (eCO2). Here, we describe a dataset of hydrological parameters – seven weather parameters at each of three heights and four locations, shallow soil moisture and temperature, stream hydrology and CO2 enrichment – retrieved at high frequency from the BIFoR FACE catchment. 相似文献
24.
Hannu Marttila Annalea Lohila Pertti Ala-Aho Kashif Noor Jeffrey M. Welker Danny Croghan Kaisa Mustonen Leo-Juhani Meriö Anna Autio Filip Muhic Hannah Bailey Mika Aurela Jussi Vuorenmaa Timo Penttilä Valtteri Hyöky Eric Klein Anton Kuzmin Pasi Korpelainen Timo Kumpula Anssi Rauhala Bjørn Kløve 《水文研究》2021,35(9):e14350
Subarctic ecohydrological processes are changing rapidly, but detailed and integrated ecohydrological investigations are not as widespread as necessary. We introduce an integrated research catchment site (Pallas) for atmosphere, ecosystems, and ecohydrology studies in subarctic conditions in Finland that can be used for a new set of comparative catchment investigations. The Pallas site provides unique observational data and high-intensity field measurement datasets over long periods. The infrastructure for atmosphere- to landscape-scale research in ecosystem processes in a subarctic landscape has recently been complemented with detailed ecohydrological measurements. We identify three dominant processes in subarctic ecohydrology: (a) strong seasonality drives ecohydrological regimes, (b) limited dynamic storage causes rapid stream response to water inputs (snowmelt and intensive storms), and (c) hydrological state of the system regulates catchment-scale dissolved carbon dynamics and greenhouse (GHG) fluxes. Surface water and groundwater interactions play an important role in regulating catchment-scale carbon balances and ecosystem respiration within subarctic peatlands, particularly their spatial variability in the landscape. Based on our observations from Pallas, we highlight key research gaps in subarctic ecohydrology and propose several ways forward. We also demonstrate that the Pallas catchment meets the need for sustaining and pushing the boundaries of critical long-term integrated ecohydrological research in high-latitude environments. 相似文献
25.
Shaun Cole John Helly Carlos S. Frenk Hannah Parkinson 《Monthly notices of the Royal Astronomical Society》2008,383(2):546-556
We present a comparison of the statistical properties of dark matter halo merger trees extracted from the Millennium Simulation with Extended Press–Schechter (EPS) formalism and the related galform Monte Carlo method for generating ensembles of merger trees. The volume, mass resolution and output frequency make the Millennium Simulation a unique resource for the study of the hierarchical growth of structure. We construct the merger trees of present-day friends-of-friends groups and calculate a variety of statistics that quantify the masses of their progenitors as a function of redshift, accretion rates, and the redshift distribution of their most recent major merger. We also look in the forward direction and quantify the present-day mass distribution of haloes into which high-redshift progenitors of a specific mass become incorporated. We find that the EPS formalism and its Monte Carlo extension capture the qualitative behaviour of all these statistics, but as redshift increases they systematically underestimate the masses of the most massive progenitors. This shortcoming is worst for the Monte Carlo algorithm. We present a fitting function to a scaled version of the progenitor mass distribution and show how it can be used to make more accurate predictions of both progenitor and final halo mass distributions. 相似文献
26.
Svetlana S. Kostrova Hanno Meyer Hannah L. Bailey Anna V. Ludikova Raphael Gromig Gerhard Kuhn Yuri A. Shibaev Anna V. Kozachek Alexey A. Ekaykin Bernhard Chapligin 《Boreas: An International Journal of Quaternary Research》2019,48(2):361-376
This article presents a new comprehensive assessment of the Holocene hydrological variability of Lake Ladoga, northwest Russia. The reconstruction is based on oxygen isotopes of lacustrine diatom silica (δ18Odiatom) preserved in sediment core Co 1309, and is complemented by a diatom assemblage analysis and a survey of modern isotope hydrology. The data indicate that Lake Ladoga has existed as a freshwater reservoir since at least 10.8 cal. ka BP. The δ18Odiatom values range from +29.8 to +35.0‰, and relatively higher δ18Odiatom values around +34.7‰ between c. 7.1 and 5.7 cal. ka BP are considered to reflect the Holocene Thermal Maximum. A continuous depletion in δ18Odiatom since c. 6.1 cal. ka BP accelerates after c. 4 cal. ka BP, indicating Middle to Late Holocene cooling that culminates during the interval 0.8–0.2 cal. ka BP, corresponding to the Little Ice Age. Lake‐level rises result in lower δ18Odiatom values, whereas lower lake levels cause higher δ18Odiatom values. The diatom isotope record gives an indication for a rather early opening of the Neva River outflow at c. 4.4–4.0 cal. ka BP. Generally, overall high δ18Odiatom values around +33.5‰ characterize a persistent evaporative lake system throughout the Holocene. As the Lake Ladoga δ18Odiatom record is roughly in line with the 60°N summer insolation, a linkage to broader‐scale climate change is likely. 相似文献
27.
Joshua Fisher Hannah Stutzman Mariana Vedoveto Debora Delgado Ramon Rivero Walter Quertehuari Dariquebe 《社会与自然资源》2020,33(4):538-553
AbstractGiven the linkages between natural resources and social conflicts, evidence increasingly shows that successful natural resource management requires conflict mitigation and prevention. However, there may be a gap in practice between knowing what processes and tools need to be used to manage conservation conflicts and how to actually implement them. We present learning from a practice-based case study of conflict management in the Amarakaeri Communal Reserve in the Peruvian Amazon that aimed to develop natural resource governance institutions and build stakeholder capacity, including of indigenous groups, to navigate existing conflict resolution mechanisms. Through applying good practices in conservation conflict management and collaborative governance, we generated important lessons on the practical considerations involved in collaborative conservation. These lessons, while specific to our case, could be applied to a variety of protected areas facing complex social-ecological systems dynamics and wicked problems. 相似文献
28.
Max Nielsen-Pincus Patricia Sussman Drew E. Bennett Hannah Gosnell Robert Parker 《社会与自然资源》2017,30(12):1423-1441
Sense of place, including an individual’s attitudes toward specific geographic settings, is generally predicted to influence willingness to engage in place-protective behaviors. Relatively little research, however, has empirically examined the influence of people’s attitudes toward a place on their willingness to pay for environmental protection. Using the example of a payment for ecosystem services (PES) initiative in the McKenzie River watershed, Oregon, USA, we found that place attitudes were a significant predictor of respondents’ willingness to pay for a program designed to benefit drinking water quality. These results suggest that connecting conservation actions to landscapes that are meaningful to people may increase their financial support for PES and other conservation programs. While program managers have little or no influence over stakeholders’ political ideology, gender, or income, managers may be able to influence prospective PES buyers’ awareness and attitudes through targeted communications, thereby potentially increasing support for place-based conservation efforts. 相似文献
29.
Ignazio Giuntoli Gabriele Villarini Christel Prudhomme David M. Hannah 《Climatic change》2018,150(3-4):149-162
Projections of runoff from global multi-model ensembles provide a valuable basis for the estimation of future hydrological extremes. However, projections suffer from uncertainty that originates from different error sources along the modeling chain. Hydrological impact studies have generally partitioned these error sources into global impact and global climate model (GIM and GCM, respectively) uncertainties, neglecting other sources, including scenarios and internal variability. Using a set of GIMs driven by GCMs under different representative concentration pathways (RCPs), this study aims to partition the uncertainty of future flows coming from GIMs, GCMs, RCPs, and internal variability over the CONterminous United States (CONUS). We focus on annual maximum, median, and minimum runoff, analyzed decadally over the twenty-first century. Results indicate that GCMs and GIMs are responsible for the largest fraction of uncertainty over most of the study area, followed by internal variability and to a smaller extent RCPs. To investigate the influence of the ensemble setup on uncertainty, in addition to the full ensemble, three ensemble configurations are studied using fewer GIMs (excluding least credible GIMs in runoff representation and GIMs accounting for vegetation and CO2 dynamics), and excluding intermediate RCPs. Overall, the use of fewer GIMs has a minor impact on uncertainty for low and medium flows, but a substantial impact for high flows. Regardless of the number of pathways considered, RCPs always play a very small role, suggesting that improvement of GCMs and GIMs and more informed ensemble selections can yield a reduction of projected uncertainties. 相似文献
30.
Lee Hannah Marc Steele Emily Fung Pablo Imbach Lorriane Flint Alan Flint 《Climatic change》2017,140(1):63-77
Improved cookstoves have been identified in Mexico as a key opportunity to advance sustainable local development priorities in disadvantaged regions while mitigating climate change. This paper reviews the Patsari Cookstove Project initiated in 2003 by an NGO, Interdisciplinary Group on Appropriate Rural Technology (GIRA). The project applied an interdisciplinary and participative user-centered approach to disseminate improved cookstoves in rural Mexico, with a special focus on indigenous and poor rural communities. To date, GIRA and the Patsari Network have disseminated thousands of stoves using a “training to trainers” model. Benefits from the project include tangible improvements in users’ health, as well as savings in time and money expended on fuelwood procurement and use. The project has also documented substantive environmental benefits from significant mitigation of greenhouse gas (GHG) emissions associated with traditional open fires. To sustain scaling up efforts over the long-term, two networks have been created: The Patsari Network, which includes several organizations promoting Patsari stoves for household users, and the Tsiri Network, which supports local food security and the empowerment of indigenous women through the promotion of institutional cookstoves. Through appropriately designed and implemented local interventions, the project demonstrates that the goals of advancing sustainable local development in rural areas and climate change mitigation may not be contradictory, and may in fact reinforce one another. 相似文献