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831.
We describe and test a method for identifying alluvial fans likely to be affected by debris flows. It is based on identifying
catchment parameters by geographical information system interrogation of a digital elevation model, using the Melton ratio
as the discriminating parameter. The method was calibrated using data from debris-flow-generating catchments in Coromandel
and the adjacent Kaimai Ranges, North Island, NZ, and tested against data from the rest of New Zealand. The procedure is remarkably
(but not completely) reliable for identifying debris-flow-capable catchments, and thus fans, across the wide range of climates
and lithologies in New Zealand mountains. A case study illustrates the potential of the method for avoiding future hazards
and emphasises the need for a precautionary approach when field investigations do not detect evidence for past debris flows. 相似文献
832.
András A. Sipos Gábor Domokos Andrew Wilson Niels Hovius 《Mathematical Geosciences》2011,43(5):583-591
We use a simple, collision-based, discrete, random abrasion model to compute the profiles for the stoss faces in a bedrock
abrasion process. The model is the discrete equivalent of the generalized version of a classical, collision based model of
abrasion. Three control parameters (which describe the average size of the colliding objects, the expected direction of the
impacts and the average volume removed from the body due to one collision) are sufficient for realistic predictions. 相似文献
833.
Kirstin Dobbs Jon Day Hilary Skeat John Baldwin Fergus Molloy Laurence McCook Margaret Johnson Bruce Elliot Andrew Skeat Karen Vohland David Wachenfeld Richard Kenchington 《Marine Policy》2011
The Great Barrier Reef Outlook Report 2009 was the first produced in response to a newly legislated requirement for five-yearly reports on the status of and outlook for the Great Barrier Reef. It adopted an ecosystem approach, assessing all habitats and species, ecosystem processes and major uses. By then considering the factors affecting the ecosystem, coupled with an assessment of management effectiveness, it provided a risk-based forward-looking projection for the ecosystem. Rarely has such a comprehensive, ecosystem-based report been produced to guide government action. With no pre-determined path to follow for interpreting the legislative requirements, the Great Barrier Reef Marine Park Authority (GBRMPA) developed a repeatable structure and method for Great Barrier Reef Outlook Reports that impartially and consistently considers the evidence and clearly presents the findings. The GBRMPA worked closely with relevant Australian and Queensland Government agencies as well as researchers, industry representatives and the community while developing the report. That such a report must be produced every five years allows an overview of the effectiveness of management responses to be regularly assessed. It also provides a transparent means of highlighting and tracking emerging risks facing the Great Barrier Reef. 相似文献
834.
Climate Dynamics - We assess the impact of split-flow blocking in the Australian region on global ocean wind waves using 30 years of high-resolution wave data from the CAWCR wave model... 相似文献
835.
Steven P. Hamburg Matthew A. Vadeboncoeur Andrew D. Richardson Amey S. Bailey 《Climatic change》2013,116(3-4):457-477
Observing the full range of climate change impacts at the local scale is difficult. Predicted rates of change are often small relative to interannual variability, and few locations have sufficiently comprehensive long-term records of environmental variables to enable researchers to observe the fine-scale patterns that may be important to understanding the influence of climate change on biological systems at the taxon, community, and ecosystem levels. We examined a 50-year meteorological and hydrological record from the Hubbard Brook Experimental Forest (HBEF) in New Hampshire, an intensively monitored Long-Term Ecological Research site. Of the examined climate metrics, trends in temperature were the most significant (ranging from 0.7 to 1.3 °C increase over 40–50 year records at 4 temperature stations), while analysis of precipitation and hydrologic data yielded mixed results. Regional records show generally similar trends over the same time period, though longer-term (70–102 year) trends are less dramatic. Taken together, the results from HBEF and the regional records indicate that the climate has warmed detectably over 50 years, with important consequences for hydrological processes. Understanding effects on ecosystems will require a diversity of metrics and concurrent ecological observations at a range of sites, as well as a recognition that ecosystems have existed in a directionally changing climate for decades, and are not necessarily in equilibrium with the current climate. 相似文献
836.
A favoured method of assimilating information from state-of-the-art climate models into integrated assessment models of climate impacts is to use the transient climate response (TCR) of the climate models as an input, sometimes accompanied by a pattern matching approach to provide spatial information. More recent approaches to the problem use TCR with another independent piece of climate model output: the land-sea surface warming ratio (φ). In this paper we show why the use of φ in addition to TCR has such utility. Multiple linear regressions of surface temperature change onto TCR and φ in 22 climate models from the CMIP3 multi-model database show that the inclusion of φ explains a much greater fraction of the inter-model variance than using TCR alone. The improvement is particularly pronounced in North America and Eurasia in the boreal summer season, and in the Amazon all year round. The use of φ as the second metric is beneficial for three reasons: firstly it is uncorrelated with TCR in state-of-the-art climate models and can therefore be considered as an independent metric; secondly, because of its projected time-invariance, the magnitude of φ is better constrained than TCR in the immediate future; thirdly, the use of two variables is much simpler than approaches such as pattern scaling from climate models. Finally we show how using the latest estimates of φ from climate models with a mean value of 1.6—as opposed to previously reported values of 1.4—can significantly increase the mean time-integrated discounted damage projections in a state-of-the-art integrated assessment model by about 15 %. When compared to damages calculated without the inclusion of the land-sea warming ratio, this figure rises to 65 %, equivalent to almost 200 trillion dollars over 200 years. 相似文献
837.
Diatom assemblages in recent versus pre-industrial sediments were examined in 40 relatively undisturbed lakes from the Experimental
Lakes Area (ELA). The ELA region of northwestern Ontario receives low amounts of acidic deposition and the lakes have been
minimally disturbed by watershed development or other human activities. Consequently, this region represents an important
location to detect possible changes in lakes due to climate change. In over half of the lakes, planktonic taxa (especially
Discostella stelligera) increased between 10 and 40% since pre-industrial times. Changes in diatom assemblages are consistent with taxa that would
benefit from enhanced stratification and a longer ice-free season. We hypothesized that there should be a relationship between
stratification and measured chemical and physical characteristics of the study lakes. Multiple correlation analysis was undertaken
to see the relationship between planktonic taxa and D. stelligera since pre-industrial times and the physical and chemical characteristics of the study lakes. Lake depth was consistently
identified as an important variable. The timing of the increase in planktonic taxa within cores from these lakes will be needed
to rule out other possible regional changes that may also be occurring in the ELA region. 相似文献
838.
Andrew A. Skabar 《Natural Resources Research》2011,20(3):143-155
Assuming a study region in which each cell has associated with it an N-dimensional vector of values corresponding to N predictor variables, one means of predicting the potential of some cell to host mineralization is to estimate, on the basis
of historical data, a probability density function that describes the distribution of vectors for cells known to contain deposits.
This density estimate can then be employed to predict the mineralization likelihood of other cells in the study region. However,
owing to the curse of dimensionality, estimating densities in high-dimensional input spaces is exceedingly difficult, and
conventional statistical approaches often break down. This article describes an alternative approach to estimating densities.
Inspired by recent work in the area of similarity-based learning, in which input takes the form of a matrix of pairwise similarities
between training points, we show how the density of a set of mineralized training examples can be estimated from a graphical
representation of those examples using the notion of eigenvector graph centrality. We also show how the likelihood for a test
example can be estimated from these data without having to construct a new graph. Application of the technique to the prediction
of gold deposits based on 16 predictor variables shows that its predictive performance far exceeds that of conventional density
estimation methods, and is slightly better than the performance of a discriminative approach based on multilayer perceptron
neural networks. 相似文献
839.
Ryan E. Sherrill Andrew J. Sinclair S. C. Sinha T. Alan Lovell 《Celestial Mechanics and Dynamical Astronomy》2014,119(1):55-73
The relative motion of chief and deputy satellites in close proximity with orbits of arbitrary eccentricity can be approximated by linearized time-periodic equations of motion. The linear time-invariant Hill–Clohessy–Wiltshire equations are typically derived from these equations by assuming the chief satellite is in a circular orbit. Two Lyapunov–Floquet transformations and an integral-preserving transformation are here presented which relate the linearized time-varying equations of relative motion to the Hill–Clohessy–Wiltshire equations in a one-to-one manner through time-varying coordinate transformations. These transformations allow the Hill–Clohessy–Wiltshire equations to describe the linearized relative motion for elliptic chief satellites. 相似文献
840.
Philipp R. Heck Frank J. Stadermann Dieter Isheim Orlando Auciello Tyrone L. Daulton Andrew M. Davis Jeffrey W. Elam Christine Floss Jon Hiller David J. Larson Josiah B. Lewis Anil Mane Michael J. Pellin Michael R. Savina David N. Seidman Thomas Stephan 《Meteoritics & planetary science》2014,49(3):453-467
Atom‐probe tomography (APT) is currently the only analytical technique that, due to its spatial resolution and detection efficiency, has the potential to measure the carbon isotope ratios of individual nanodiamonds. We describe three different sample preparation protocols that we developed for the APT analysis of meteoritic nanodiamonds at sub‐nm resolution and present carbon isotope peak ratios of meteoritic and synthetic nanodiamonds. The results demonstrate an instrumental bias associated with APT that needs to be quantified and corrected to obtain accurate isotope ratios. After this correction is applied, this technique should allow determination of the distribution of 12C/13C ratios in individual diamond grains, solving the decades‐old question of the origin of meteoritic nanodiamonds: what fraction, if any, formed in the solar system and in presolar environments? Furthermore, APT could help us identify the stellar sources of any presolar nanodiamonds that are detected. 相似文献