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991.
Coastal erosion and control 总被引:2,自引:0,他引:2
L.C. van Rijn 《Ocean & Coastal Management》2011,54(12):867-887
Coastal erosion is a problem at many coastal sites caused by natural effects as well as human activities. This paper explores the coastal cell concept to deal with coastal erosion by identifying and analysingthe sediment volumes accumulated in large-scale and small-scale coastal cells at various sites. Mechanisms causing chronic erosion and episodic erosion related to coastal variability are identified and discussed. The effectiveness of soft and hard remedial measures for sandy beaches are assessed based on laboratory, field and modelling experiences. 相似文献
992.
Ecosystem-based marine spatial management: Review of concepts, policies, tools, and critical issues 总被引:1,自引:0,他引:1
Stelios Katsanevakis Vanessa Stelzenmüller Andy South Thomas Kirk Sørensen Peter J.S. Jones Sandy Kerr Fabio Badalamenti Christos Anagnostou Patricia Breen Guillem Chust Giovanni D’Anna Mike Duijn Tatiana Filatova Fabio Fiorentino Helena Hulsman Kate Johnson Aristomenis P. Karageorgis Ingrid Kröncke Simone Mirto Carlo Pipitone Susan Portelli Wanfei Qiu Henning Reiss Dimitris Sakellariou Maria Salomidi Luc van Hoof Vassiliki Vassilopoulou Tomás Vega Fernández Sandra Vöge Anke Weber Argyro Zenetos Remment ter Hofstede 《Ocean & Coastal Management》2011,54(11):807-820
Conventional sectoral management and piecemeal governance are considered less and less appropriate in pursuit of sustainable development. Ecosystem based marine spatial management (EB-MSM) is an approach that recognizes the full array of interactions within an ecosystem, including human uses, rather than considering single issues, species, or ecosystem services in isolation. Marine spatial planning and ocean zoning are emerging concepts that can support EB-MSM. EB-MSM is driven by high-level goals that managers aim to achieve through the implementation of measures. High-level goals and objectives need to be translated into more operational objectives before specific targets, limits and measures can be elaborated.Monitoring, evaluation and adaptation are necessary to ensure that marine management measures are both effective and efficient. Solid monitoring frameworks are the foundation of adaptive management, as they provide the necessary information to evaluate performance and the effectiveness of management actions. Marine protected areas (MPAs) - possibly set up in networks - constitute a key component in EB-MSM policies and practises and have been applied as a cornerstone in conservation of marine biodiversity, management of fish populations, development of coastal tourism, etc. Moreover, MPA experiences have provided methods and concepts (such as zoning) to a wider EB-MSM context. The assignment of values to biophysical features of the marine environment allows the direct assessment of related management choices and may assist EB-MSM.A range of monetary valuation techniques have been proposed to reduce attributes of goods and services to a single metric. However, in the marine environment such an approach is often over simplistic, and thus less reductive techniques may be necessary. Rather than producing a single metric, the results of non-monetary assessments guide policy allowing weight to be given as necessary to potential areas of conflict and consensus.Strategies to take into account climate change effects and geohazard risks in EB-MSM have been applied or proposed worldwide. EB-MSM regimes must be alert to such risks and flexible to account for changes. 相似文献
993.
Jill Peloquin Julie HallKarl Safi Walker O. Smith Jr.Simon Wright Rick van den Enden 《Deep Sea Research Part II: Topical Studies in Oceanography》2011,58(6):808-823
Areas of high nutrients and low chlorophyll a comprise nearly a third of the world’s oceans, including the equatorial Pacific, the Southern Ocean and the Sub-Arctic Pacific. The SOLAS Sea-Air Gas Exchange (SAGE) experiment was conducted in late summer, 2004, off the east coast of the South Island of New Zealand. The objective was to assess the response of phytoplankton in waters with low iron and silicic acid concentrations to iron enrichment. We monitored the quantum yield of photochemistry (Fv/Fm) with pulse amplitude modulated fluorometry, chlorophyll a, primary productivity, and taxonomic composition. Measurements of Fv/Fm indicated that the phytoplankton within the amended patch were relieved from iron stress (Fv/Fm approached 0.65). Although there was no significant difference between IN and OUT stations at points during the experiment, the eventual enhancement in chlorophyll a and primary productivity was twofold by the end of the 15-day patch occupation. However, no change in particulate carbon or nitrogen pools was detected. Enhancement in primary productivity and chlorophyll a were approximately equal for all phytoplankton size classes, resulting in a stable phytoplankton size distribution. Initial seed stocks of diatoms were extremely low, <1% of the assemblage based on HPLC pigment analysis, and did not respond to iron enrichment. The most dominant groups before and after iron enrichment were type 8 haptophytes and prasinophytes that were associated with ∼75% of chlorophyll a. Twofold enhancement of biomass estimated by flow cytometry was detected only in eukaryotic picoplankton, likely prasinophytes, type 8 haptophytes and/or pelagophytes. These results suggest that factors other than iron, such as silicic acid, light or physical disturbance limited the phytoplankton assemblage during the SAGE experiment. Furthermore, these results suggest that additional iron supply to the Sub-Antarctic under similar seasonal conditions and seed stock will most likely favor phytoplankton <2 ??m. This implies that any iron-mediated gain of fixed carbon will most likely be remineralized in shallow water rather than sink and be sequestered in the deep ocean. 相似文献
994.
A. Reisinger P. Havlik K. Riahi O. van Vliet M. Obersteiner M. Herrero 《Climatic change》2013,117(4):677-690
100-year Global Warming Potentials (GWPs) are used almost universally to compare emissions of greenhouse gases in national inventories and reduction targets. GWPs have been criticised on several grounds, but little work has been done to determine global mitigation costs under alternative physics-based metrics . We used the integrated assessment model MESSAGE to compare emission pathways and abatement costs for fixed and time-dependent variants of the Global Temperature Change Potential (GTP) with those based on GWPs, for a policy goal of limiting the radiative forcing to a specified level in the year 2100. We find that fixed 100-year GTPs would increase global abatement costs (discounted and aggregated over the 21st century) under this policy goal by 5–20 % relative to 100-year GWPs, whereas time-varying GTPs would reduce costs by about 5 %. These cost differences are smaller than differences arising from alternative assumptions regarding agricultural mitigation potential and much smaller than those arising from alternative radiative forcing targets. Using the land-use model GLOBIOM, we show that alternative metrics affect food production differently in different world regions depending on regional characteristics of future land-use change to meet growing food demand. We conclude that under scenarios of complete participation, the choice of metric has a limited impact on global abatement costs but could be important for the political economy of regional and sectoral participation in collective mitigation efforts, in particular changing costs and gains over time for agriculture and energy-intensive sectors. 相似文献
995.
Bastien Girod Detlef P. van Vuuren Maria Grahn Alban Kitous Son H Kim Page Kyle 《Climatic change》2013,118(3-4):595-608
Transportation contributes to a significant and rising share of global energy use and GHG emissions. Therefore modeling future travel demand, its fuel use, and resulting CO2 emission is highly relevant for climate change mitigation. In this study we compare the baseline projections for global service demand (passenger-kilometers, ton-kilometers), fuel use, and CO2 emissions of five different global transport models using harmonized input assumptions on income and population. For four models we also evaluate the impact of a carbon tax. All models project a steep increase in service demand over the century. Technology change is important for limiting energy consumption and CO2 emissions, the study also shows that in order to stabilise or even decrease emissions radical changes would be required. While all models project liquid fossil fuels dominating up to 2050, they differ regarding the use of alternative fuels (natural gas, hydrogen, biofuels, and electricity), because of different fuel price projections. The carbon tax of 200 USD/tCO2 in 2050 stabilizes or reverses global emission growth in all models. Besides common findings many differences in the model assumptions and projections indicate room for further understanding long-term trends and uncertainty in future transport systems. 相似文献
996.
Future surface mass balance of the Antarctic ice sheet and its influence on sea level change, simulated by a regional atmospheric climate model 总被引:1,自引:1,他引:0
S. R. M. Ligtenberg W. J. van de Berg M. R. van den Broeke J. G. L. Rae E. van Meijgaard 《Climate Dynamics》2013,41(3-4):867-884
A regional atmospheric climate model with multi-layer snow module (RACMO2) is forced at the lateral boundaries by global climate model (GCM) data to assess the future climate and surface mass balance (SMB) of the Antarctic ice sheet (AIS). Two different GCMs (ECHAM5 until 2100 and HadCM3 until 2200) and two different emission scenarios (A1B and E1) are used as forcing to capture a realistic range in future climate states. Simulated ice sheet averaged 2 m air temperature (T2m) increases (1.8–3.0 K in 2100 and 2.4–5.3 K in 2200), simultaneously and with the same magnitude as GCM simulated T2m. The SMB and its components increase in magnitude, as they are directly influenced by the temperature increase. Changes in atmospheric circulation around Antarctica play a minor role in future SMB changes. During the next two centuries, the projected increase in liquid water flux from rainfall and snowmelt, together 60–200 Gt year?1, will mostly refreeze in the snow pack, so runoff remains small (10–40 Gt year?1). Sublimation increases by 25–50 %, but remains an order of magnitude smaller than snowfall. The increase in snowfall mainly determines future changes in SMB on the AIS: 6–16 % in 2100 and 8–25 % in 2200. Without any ice dynamical response, this would result in an eustatic sea level drop of 20–43 mm in 2100 and 73–163 mm in 2200, compared to the twentieth century. Averaged over the AIS, a strong relation between $\Updelta$ SMB and $\Updelta\hbox{T}_{2{\rm m}}$ of 98 ± 5 Gt w.e. year?1 K?1 is found. 相似文献
997.
The origin of the so-called “fairy circles” has not yet been established. Carbon monoxide (as an indicator of a natural gas microseep) was monitored inside and outside of the selected fairy circles in the Namib, Namibia, Southern Africa. Hydrocarbons were extracted from the soil by a novel method for trapping analytes onto silicone rubber designed for thermal desorption into a gas chromatograph-mass spectrometer (GC-MS). Unresolved complex mixtures with resolvable alkanes were detected in soil collected from two newly formed circles. Alkenes, the microbial degradation product of alkanes (microbial food source), were more abundant in the circles compared to the levels of alkenes detected in the matrix between circles. Results show a microseepage of gases and hydrocarbons which is expressed at the surface as a geobotanical anomaly of barren circles and circles of altered vegetation. In addition, this finding may suggest a new approach to the origin of the mima mounds (heuweltjies) of the Western Cape in South Africa. 相似文献
998.
C. H. Mandrini F. A. Nuevo A. M. Vásquez P. Démoulin L. van Driel-Gesztelyi D. Baker J. L. Culhane G. D. Cristiani M. Pick 《Solar physics》2014,289(11):4151-4171
Recent studies show that active-region (AR) upflowing plasma, observed by the EUV-Imaging Spectrometer (EIS) onboard Hinode, can gain access to open-field lines and be released into the solar wind (SW) via magnetic-interchange reconnection at magnetic null-points in pseudo-streamer configurations. When only one bipolar AR is present on the Sun and is fully covered by the separatrix of a streamer, such as AR 10978 in December 2007, it seems unlikely that the upflowing AR plasma can find its way into the slow SW. However, signatures of plasma with AR composition have been found at 1 AU by Culhane et al. (Solar Phys. 289, 3799, 2014) that apparently originated west of AR 10978. We present a detailed topology analysis of AR 10978 and the surrounding large-scale corona based on a potential-field source-surface (PFSS) model. Our study shows that it is possible for the AR plasma to move around the streamer separatrix and be released into the SW via magnetic reconnection, which occurs in at least two main steps. We analyse data from the Nançay Radioheliograph (NRH) in a search for evidence of the chain of magnetic reconnections that we propose. We find a noise storm above the AR and several varying sources at 150.9 MHz. Their locations suggest that they might be associated with particles accelerated during the first-step reconnection process at a null point well outside of the AR. We find no evidence of the second reconnection step in the radio data, however. Our results demonstrate that even when it appears highly improbable for the AR plasma to reach the SW, indirect channels involving a sequence of reconnections can make it possible. 相似文献
999.