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101.
102.
Titze Daniel Beletsky Dmitry Feyen Jesse Saunders William Mason Lacey Kessler James Chu Philip Lee Deborah 《Ocean Dynamics》2023,73(5):231-248
Ocean Dynamics - In response to record-breaking flooding on Lake Champlain in 2011, the International Joint Commission launched a 5-year study to explore solutions to flooding in the binational... 相似文献
103.
Water Resources - This study explores the statistical relationship between spectral reflectance and hydraulic conductivity (K) of fluvial sediments in two Nebraska rivers. The spectral reflectance... 相似文献
104.
H.Jesse Walker 《Geoforum》1984,15(3):395-417
Man evolved late in terms of geologic history, yet he has become a major geomorphologic agent despite his short tenure on Earth. His ability to alter the materials, processes and forms along the world's shorelines are manifested in a variety of ways. Beginning with the indirect changes that resulted from early agriculture and animal husbandry, he progressed to direct modification through reclamation and harbor construction. Today, in the name of shoreline stabilization, thousands of kilometers of natural shoreline have been modified by the addition of artificial structures. 相似文献
105.
Summary Discontinuities in a rock mass can intersect an excavation surface to form discrete blocks (keyblocks) which can be unstable. Once a potentially unstable block is identified, initial normal and shear stresses on each block face are calculated using elastic theory, and are then modified by discontinuity deformations as the keyblock displaces. The modified stresses are summed into resultant forces to evaluate block stability. Since the resultant forces change with displacement, successive increments of block movement are examined to see whether the block ultimately becomes stable or fails. Calculated keyblock stability increases with larger in situ stress magnitudes, larger lateral stress ratios, and larger shear strengths. Discontinuity stiffness controls block displacement more strongly than it does stability itself. Large keyblocks are less stable than small ones, and stability increases as blocks become more slender. 相似文献
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Pavel Ya. Groisman Boris G. Sherstyukov Vyacheslav N. Razuvaev Richard W. Knight Jesse G. Enloe Nina S. Stroumentova Paul H. Whitfield Eirik Frland Inger Hannsen-Bauer Heikki Tuomenvirta Hans Aleksandersson Anna V. Mescherskaya Thomas R. Karl 《Global and Planetary Change》2007,56(3-4):371
Significant climatic changes over Northern Eurasia during the 20th century have been reflected in numerous variables of economic, social, and ecological interest, including the natural frequency of forest fires. For the former USSR, we are now using the Global Daily Climatology Network and a new Global Synoptic Data Network archive, GSDN, created jointly by U.S. National Climatic Data Center and Russian Research Institute for Hydrometeorological Information. Data from these archives (approximately 1500 of them having sufficiently long meteorological time series suitable for participation in our analyses) are employed to estimate systematic changes in indices used in the United States and Russia to assess potential forest fire danger. We use four indices: (1) Keetch–Byram Drought Index, (KBDI; this index was developed and widely used in the United States); (2) Nesterov, (3) Modified Nesterov, and (4) Zhdanko Indices (these indices were developed and widely used in Russia). Analyses show that after calibration, time series of the days with increased potential forest fire danger constructed using each of these three indices (a) are well correlated and (b) deliver similar conclusions about systematic changes in the weather conditions conducive to forest fires. Specifically, over the Eastern half of Northern Eurasia (Siberia and the Russian Far East) statistically significant increases in indices that characterize the weather conditions conducive to forest fires were found. These areas coincide with the areas of most significant warming during the past several decades south of the Arctic Circle. West of the Ural Mountains, the same indices show a steady decrease in the frequency of “dry weather summer days” during the past 60 yr. This study is corroborated with available statistics of forest fires and with observed changes in drought statistics in agricultural regions of Northern Eurasia. 相似文献
109.
The effectiveness of coastal management in developing countries is widely perceived to be inhibited by a lack of scientific data on the coastal zone. To try to fill this need for information, donors and big international non-governmental organizations are increasingly initiating large-scale, science-driven conservation programs, with the goal of creating and using management relevant transdisciplinary datasets. In Oceania, these programs are entering a context where local ecological knowledge is already informing existing community-based approaches to coastal management. This paper examines two large-scale programs in Fiji, the Marine Management Area Science initiative and the Vatu-i-Ra and Cakau Levu Reefs Seascape Project, and offers insight relevant to the planning and implementation of similar programs where local management systems are already in place. Research methods used to examine the programs included document analysis, direct observation, and semi-structured interviews with key stakeholders over multiple field visits to Fiji in 2009 and 2010. Results suggest that as donors, non-governmental organizations, and partners move forward in implementing these programs, there must be active steps taken to bridge boundaries between disciplines and among knowledge systems, evaluate the added value of science for all stakeholder groups, and build opportunities for datasets to be used after donor funding ends. 相似文献
110.
Empirical models for describing recent sedimentation rates in lakes distributed across broad spatial scales 总被引:1,自引:0,他引:1
Soren Brothers Jesse C. Vermaire Irene Gregory-Eaves 《Journal of Paleolimnology》2008,40(4):1003-1019
Over the last 20 years there has been a surge of interest in paleolimnology and as a result a large accumulation of lake sedimentation
records. This emerging archive has allowed us to develop empirical models to describe which variables explain significant
variation in sedimentation rates over the past ∼150 years across large spatial scales. We hypothesized that latitude would
be a significant explanatory variable of profundal zone lake sedimentation rates across a temperate to polar gradient. We
further hypothesized that along a more longitudinally-constrained dataset (i.e. east coast of North America), latitude would
explain a greater proportion of the variance. To test these hypotheses, we collated data from 125 natural, average-sized lakes
(with surface area <500 km2) by recording authors’ estimates of sedimentation rates (measured as mm/year) or by digitizing recent sediment profiles and
calculating sedimentation rates over the past ∼150 years. We found that, at both scales, latitude was the strongest predictor
of lake sedimentation rates (full dataset: r
2 = 0.28, P = 0.001, n = 125; east coast dataset: r
2 = 0.58, P < 0.001, n = 43). By conducting a multiple linear regression analysis, we found that 70% of the variance in sedimentation rates from
the east coast transect was explained by latitude and elevation alone. This latter model is of sufficient strength that it
is a robust predictive tool. Given that climate and land-use strongly co-vary with latitude and that both of these factors
have previously been shown to influence lake sedimentation rates, it appears that latitude is a surrogate measure for climate
and land-use changes. We also show support for land-use as an important variable influencing sedimentation rates by demonstrating
large increases in recent versus Holocene accumulation rates. These results indicate that it is possible to make generalizations
about sedimentation rates across broad spatial scales with even limited geographic data. 相似文献