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141.
The foundation of provenance studies of ceramics is the regional geology. Unfortunately, archaeologists often depend on regional geologic maps for comparative information. In many areas the scale of maps is too small to determine the lithological variation, which is necessary information for a robust provenance study of ceramic materials. Accurate determination requires geologic field mapping and analysis of the lithologies and clay-rich sediments present. In this provenance study of prehistoric ceramics from southwest Ecuador, we have established the lithological variation of both rocks and clay-rich sediments through geological survey. Petrographic analysis of geological samples and ancient ceramic materials determined the variation in both populations and established cases of significant correlation as well as noncorrelation between objects and local materials. Ceramic production at the Ecuadorian sites was complex and involved local production of domestic wares as well as importation of tempering materials and vessels and adoption of foreign decorative motifs. © 1997 John Wiley & Sons, Inc. 相似文献
142.
143.
There is increasing concern over the consequences of global warming for the food security and livelihoods of the world's 36 million fisherfolk and the nearly 1.5 billion consumers who rely on fish for more than 20% of their dietary animal protein. With mounting evidence of the impacts of climate variability and change on aquatic ecosystems, the resulting impacts on fisheries livelihoods are likely to be significant, but remain a neglected area in climate adaptation policy. Drawing upon our research and the available literature, and using a livelihoods framework, this paper synthesizes the pathways through which climate variability and change impact fisherfolk livelihoods at the household and community level. We identify current and potential adaptation strategies and explore the wider implications for local livelihoods, fisheries management and climate policies. Responses to climate change can be anticipatory or reactive and should include: (1) management approaches and policies that build the livelihood asset base, reducing vulnerability to multiple stressors, including climate change; (2) an understanding of current response mechanisms to climate variability and other shocks in order to inform planned adaptation; (3) a recognition of the opportunities that climate change could bring to the sector; (4) adaptive strategies designed with a multi-sector perspective; and (5) a recognition of fisheries potential contribution to mitigation efforts. 相似文献
144.
东南极Princess Elizabeth冰盖近地层大气参数的年变化特征 总被引:4,自引:0,他引:4
利用2002年东南极Princess Elizabeth冰盖自动气象梯度观测点获得的近地层气象资料,分析了冰盖上的感热通量、潜热通量、大气稳定度、整体输送系数及有关气象要素特征,并与中山站同期的的气象要素进行了对比分析.结果表明,由于两站的海拔高度及地理位置的差异,LGB69站的年平均气温为-25.6℃,比中山站低16.4℃,进入内陆每10km,海拔高度上升约110m,温度下降约1℃.南极内陆冰盖的湍流热通量具有明显的年变化,感热通量年平均值为-17.9W/m2,潜热通量为-0.9W/m2,年平均冷源强度(Qh+Qe)为-18.8W/m2,表明地表从大气吸收热量.LGB69站近地层大气以近中性层结为主,中性层结下的整体输送系数为2.6×10-3,当风速大于8m/s后,整体输送系数趋于常数.LGB69站是南极地区典型下降风区,年平均风速比中山站大2.0m/s,其下降风出现的风向频和风速均大于中山站. 相似文献
145.
Results are presented of a sequence of laboratory tests undertaken to elucidate the behaviour of deep-seated landslides. In deep-seated failures deformation has been reported at depths of up to 250 m. In the movement zone, owing to the weight of the overburden and the surrounding stress environment, conventional soil mechanics cannot be used to explain effectively associations between the landslip activity and the deformation mechanisms operating within the moving mass. A series of experiments has been undertaken on London Clay using a high pressure, servohydraulically controlled triaxial deformation system, to replicate the stresses acting at the base of a large, deep-seated landslide. A number of tests were undertaken, the most significant focusing on the transition between ductile and brittle behaviour. Although sediments usually behave in a brittle manner at low effective stresses (common to many geomorphological studies) and in a ductile manner at high effective stresses, the results presented here identify for the first time in mudrocks a transitional phase of behaviour in which creep-like movement will manifest itself at the base of a deep-seated landslide as the growth of microcracks. The microcracks may eventually coalesce to form a shear surface, a consequence of which is likely to be sudden failure. The results thus have important implications in the understanding of movement mechanisms in large, deep-seated failures, rates of displacement and how they may change through time. © 1997 by John Wiley & Sons, Ltd. 相似文献
146.
Paul G. Matson Louise M. Stevenson Natalie A. Griffiths Christopher R. DeRolph R. Trent Jett Allison M. Fortner Michael W. Jones Nikki J. Jones Teresa J. Mathews 《水文研究》2021,35(9):e14340
Human activities can be powerful drivers of ecosystem change within catchments. While most long-term catchment studies have been conducted at pristine sites, such studies are less common from sites more impacted by human activity. The Oak Ridge National Laboratory's Biological Monitoring and Abatement Program (BMAP) was developed in the mid-1980s to (1) assess compliance with environmental regulations, (2) identify causes of adverse ecological impacts, (3) provide data for human and ecological risk assessments, and (4) evaluate the effectiveness of remedial actions taken to mitigate the impacts of contaminants in soils, groundwater, and surface water by documenting ecological recovery on the Oak Ridge Reservation (ORR), a federally owned 33 476-acre site in eastern Tennessee, managed by the US Department of Energy. The ORR is composed of multiple watersheds containing many small to mid-size streams. BMAP uses an integrated approach for determining stream health; its databases include long-term seasonal records of contaminant concentrations in water and biota, data from aquatic toxicity testing, and surveys of macroinvertebrate and fish assemblages from impacted and reference streams. These long-term data provide valuable records of degradation and recovery in catchment ecosystems. Our objective here is to describe our study system and data series in order to increase awareness of the availability of these long-term data to the catchment science community. 相似文献
147.
The Sr/Ca of aragonitic coral skeletons is a commonly used palaeothermometer. However skeletal Sr/Ca is typically dominated by weekly-monthly oscillations which do not reflect temperature or seawater composition and the origins of which are currently unknown. To test the impact of transcellular Ca2+ transport processes on skeletal Sr/Ca, colonies of the branching coral, Pocillopora damicornis, were cultured in the presence of inhibitors of Ca-ATPase (ruthenium red) and Ca channels (verapamil hydrochloride). The photosynthesis, respiration and calcification rates of the colonies were monitored throughout the experiment. The skeleton deposited in the presence of the inhibitors was identified (by 42Ca spike) and analysed for Sr/Ca and Mg/Ca by secondary ion mass spectrometry. The Sr/Ca of the aragonite deposited in the presence of either of the inhibitors was not significantly different from that of the solvent (dimethyl sulfoxide) control, although the coral calcification rate was reduced by up to 66% and 73% in the ruthenium red and verapamil treatments, respectively. The typical precision (95% confidence limits) of mean Sr/Ca determinations within any treatment was <±1% and differences in skeletal Sr/Ca between treatments were correspondingly small. Either Ca-ATPase and Ca channels transport Sr2+ and Ca2+ in virtually the same ratio in which they are present in seawater or transcellular processes contribute little Ca2+ to the skeleton and most Ca is derived from seawater transported directly to the calcification site. Variations in the activities of Ca-ATPase and Ca-channels are not responsible for the weekly-monthly Sr/Ca oscillations observed in skeletal chronologies, assuming that the specificities of Ca transcellular transport processes are similar between coral genera. 相似文献
148.
RCP4.5: a pathway for stabilization of radiative forcing by 2100 总被引:3,自引:2,他引:1
Allison M. Thomson Katherine V. Calvin Steven J. Smith G. Page Kyle April Volke Pralit Patel Sabrina Delgado-Arias Ben Bond-Lamberty Marshall A. Wise Leon E. Clarke James A. Edmonds 《Climatic change》2011,109(1-2):77-94
Representative Concentration Pathway (RCP) 4.5 is a scenario that stabilizes radiative forcing at 4.5?W?m?2 in the year 2100 without ever exceeding that value. Simulated with the Global Change Assessment Model (GCAM), RCP4.5 includes long-term, global emissions of greenhouse gases, short-lived species, and land-use-land-cover in a global economic framework. RCP4.5 was updated from earlier GCAM scenarios to incorporate historical emissions and land cover information common to the RCP process and follows a cost-minimizing pathway to reach the target radiative forcing. The imperative to limit emissions in order to reach this target drives changes in the energy system, including shifts to electricity, to lower emissions energy technologies and to the deployment of carbon capture and geologic storage technology. In addition, the RCP4.5 emissions price also applies to land use emissions; as a result, forest lands expand from their present day extent. The simulated future emissions and land use were downscaled from the regional simulation to a grid to facilitate transfer to climate models. While there are many alternative pathways to achieve a radiative forcing level of 4.5?W?m?2, the application of the RCP4.5 provides a common platform for climate models to explore the climate system response to stabilizing the anthropogenic components of radiative forcing. 相似文献
149.
Natalie K. Karouna-Renier Richard A. Snyder Ted Lange Suzanne Gibson Jeffrey G. Allison Matthew E. Wagner K. Ranga Rao 《Marine environmental research》2011,72(3):96-104
The health benefits of regular consumption of fish and seafood have been espoused for many years. However, fish are also a potential source of environmental contaminants that have well known adverse effects on human health. We investigated the consumption risks for largemouth bass (Micropterus salmoides; n = 104) and striped mullet (Mugil cephalus; n = 170), two commonly harvested and consumed fish species inhabiting fresh and estuarine waters in northwest Florida. Skinless fillets were analyzed for total mercury, inorganic arsenic, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F), polychlorinated biphenyls (PCBs), and organochlorine pesticides. Contaminant levels were compared to screening values (SV) calculated using U.S. Environmental Protection Agency (EPA) recommendations for establishing consumption advisories. Largemouth bass were found to contain high levels of total mercury at all sampling locations (0.37–0.89 ug/g) and one location exhibited elevated total PCBs (39.4 ng/g). All of the samples exceeded Florida fish consumption advisory trigger levels for total mercury and one location exceeded the U.S. EPA SV for total PCBs. As a result of the high mercury levels, the non-cancer health risks (hazard index–HI) for bass were above 1 for all locations. Striped mullet from several locations with known point sources contained elevated levels of PCBs (overall range 3.4–59.3 ng/g). However, total mercury levels in mullet were low. Eight of the 16 mullet sampling locations exceeded the U.S. EPA SV for total PCBs and two locations exceeded an HI of 1 due to elevated PCBs. Despite the elevated levels of total PCBs in some samples, only two locations exceeded the acceptable cancer risk range and therefore cancer health risks from consumption of bass and mullet were determined to be low at most sampling locations. 相似文献
150.
Recharge to the Quaternary aquifers beneath the Northern Adelaide Plains was estimated to be 3.9 x 106 m3/year using the environmental tritium concentration of water samples taken from suitably sited boreholes. Recharge to the Tertiary aquifers was estimated to be 0.4 x 106m3/year, by the same isotopic techniques. These results may be compared with a total recharge by leakage through the beds of streams which cross the plain, estimated by the South Australian Department of Mines to be 6.4 x 106 m3/year. 相似文献