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261.
高福晖 《中国人口.资源与环境》1992,(4)
经过六年多的研究,笔者认为:三峡工程对生态环境的影响有有利影响和不利影响两个方面。对不利影响只要认真对待,采取措施,可以减少到最小程度,所以生态环境问题不是三峡工程决策的制约因素。 相似文献
262.
城镇用地扩张的影响分析 总被引:8,自引:0,他引:8
杨钢桥 《中国人口.资源与环境》2004,14(4):75-79
社会经济条件的变化是推动城镇用地扩张的重要力量。城镇用地规模不断扩大,不仅促进了城镇本身功能的完善、经济实力的提高,带动了周围农村地区社会经济的发展。而且,城镇用地大量、快速向外扩张也给城镇本身及其周围农村带来了较大的负面影响。 相似文献
263.
新排污收费条例对燃煤电厂的影响探析 总被引:1,自引:0,他引:1
《排污费征收和管理条例》(简称新《条例》)的实施是我国排污收费制度的重大变革,对相关行业将产生不同程度的影响。着重分析了新《条例》的实施对燃煤电厂的不利影响,以及对企业增加环保投入治理污染的推动作用。 相似文献
264.
265.
266.
ABSTRACT A major barrier to realising biofuels’ climate change mitigation potential is uncertainty concerning carbon emissions from indirect land use change (ILUC). Central to this uncertainty is the extent to which yields can respond dynamically to increased demand for agricultural commodities. This study examines the elasticity of soybean and corn yields in the USA for 1990–2017 using Bayesian network models to robustly quantify uncertainty. The central finding is that a single parameter value for yield elasticity does not adequately represent the effects of technology, policy and price pressures through time. The models demonstrate the limiting role of technological progress as well as farmers’ capital investment in response to system shocks. Results suggest evaluation of parameter uncertainty alone is unlikely to capture a full range of future ILUC scenarios and reiterate the need for ILUC studies to use probabilistic approaches as standard to robustly inform climate change mitigation policies. 相似文献
267.
268.
Graphical models (alternatively, Bayesian belief networks, path analysis models) are increasingly used for modeling complex
ecological systems (e.g., Lee, In: Ferson S, Burgman M(eds) Quantative methods for conservation biology. Springer, Berlin
Heilin Heideslperk New York, pp.127–147, 2000; Borsuk et al., J Water Res Plann Manage 129:271–282, 2003). Their implementation
in this context leverages their utility in modeling interrelationships in multivariate systems, and in a Bayesian implementation,
their intuitive appeal of yielding easily interpretable posterior probability estimates. However, methods for incorporating
correlational structure to account for observations collected through time and/or space—features of most ecological data—have
not been widely studied; Haas et al. (AI Appl 8:15–27, 1994) is one exception. In this paper, an “isomorphic” chain graph
(ICG) model is introduced to account for correlation between samples by linking site-specific Bayes network models. Several
results show that the ICG preserves many of the Markov properties (conditional and marginal dependencies) of the site-specific
models. The ICG model is compared with a model that does not account for spatial correlation. Data from several stream networks
in the Willamette River valley, Oregon (USA) are used. Significant correlation between sites within the same stream network
is shown with an ICG model. 相似文献
269.
Carin Magnhagen 《Behavioral ecology and sociobiology》2007,61(4):525-531
The connection between risk-taking behaviour and exploratory behaviour in young-of-the-year perch (Perca fluviatilis) was studied in aquarium experiments to see whether individual behaviour patterns could be identified in this species and
also to investigate how individual behaviour is influenced by their social environment. Risk-taking was defined as the time
spent foraging in an open area vs hiding in the vegetation in the presence of a piscivore. Explorative behaviour was measured
as latency to enter a passage leading to an unknown area. Groups of four fish were used for the observations, and both behaviours
measured were positively correlated with the mean scores of these behaviours in the other group members. Risk-taking and explorative
behaviours were correlated only when data was adjusted for the behaviour of the other group members. Individuals that spent
more time in the open than their companions also tended to be faster than the others to enter the passage to the unknown area
and vice versa. The results indicate that there are consistent individual differences in boldness in perch, but also that
behaviour could be modified according to the behaviour of group members. 相似文献
270.
Haolan Lu Cavan S. Reilly Sudipto Banerjee Bradley P. Carlin 《Environmental and Ecological Statistics》2007,14(4):433-452
Recently, public health professionals and other geostatistical researchers have shown increasing interest in boundary analysis, the detection or testing of zones or boundaries that reveal sharp changes in the values of spatially oriented variables.
For areal data (i.e., data which consist only of sums or averages over geopolitical regions), Lu and Carlin (Geogr Anal 37: 265–285,
2005) suggested a fully model-based framework for areal wombling using Bayesian hierarchical models with posterior summaries
computed using Markov chain Monte Carlo (MCMC) methods, and showed the approach to have advantages over existing non-stochastic
alternatives. In this paper, we develop Bayesian areal boundary analysis methods that estimate the spatial neighborhood structure
using the value of the process in each region and other variables that indicate how similar two regions are. Boundaries may then be determined by the posterior distribution
of either this estimated neighborhood structure or the regional mean response differences themselves. Our methods do require
several assumptions (including an appropriate prior distribution, a normal spatial random effect distribution, and a Bernoulli
distribution for a set of spatial weights), but also deliver more in terms of full posterior inference for the boundary segments
(e.g., direct probability statements regarding the probability that a particular border segment is part of the boundary).
We illustrate three different remedies for the computing difficulties encountered in implementing our method. We use simulation
to compare among existing purely algorithmic approaches, the Lu and Carlin (2005) method, and our new adjacency modeling methods.
We also illustrate more practical modeling issues (e.g., covariate selection) in the context of a breast cancer late detection
data set collected at the county level in the state of Minnesota. 相似文献