全文获取类型
收费全文 | 4056篇 |
免费 | 69篇 |
国内免费 | 41篇 |
专业分类
安全科学 | 187篇 |
废物处理 | 155篇 |
环保管理 | 706篇 |
综合类 | 688篇 |
基础理论 | 932篇 |
环境理论 | 3篇 |
污染及防治 | 1020篇 |
评价与监测 | 240篇 |
社会与环境 | 189篇 |
灾害及防治 | 46篇 |
出版年
2023年 | 33篇 |
2022年 | 41篇 |
2021年 | 51篇 |
2020年 | 50篇 |
2019年 | 50篇 |
2018年 | 98篇 |
2017年 | 118篇 |
2016年 | 133篇 |
2015年 | 136篇 |
2014年 | 142篇 |
2013年 | 226篇 |
2012年 | 175篇 |
2011年 | 296篇 |
2010年 | 221篇 |
2009年 | 228篇 |
2008年 | 235篇 |
2007年 | 243篇 |
2006年 | 209篇 |
2005年 | 137篇 |
2004年 | 164篇 |
2003年 | 133篇 |
2002年 | 134篇 |
2001年 | 113篇 |
2000年 | 68篇 |
1999年 | 48篇 |
1998年 | 49篇 |
1997年 | 43篇 |
1996年 | 48篇 |
1995年 | 50篇 |
1994年 | 45篇 |
1993年 | 25篇 |
1992年 | 36篇 |
1991年 | 36篇 |
1990年 | 25篇 |
1989年 | 24篇 |
1988年 | 17篇 |
1987年 | 20篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 17篇 |
1983年 | 10篇 |
1982年 | 23篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 17篇 |
1970年 | 11篇 |
1969年 | 7篇 |
1967年 | 7篇 |
1965年 | 9篇 |
1960年 | 6篇 |
排序方式: 共有4166条查询结果,搜索用时 375 毫秒
351.
To aid in the management and conservation of Southwestern Willow Flycatcher (Empidonax traillii extimus, hereafter “Flycatcher”), we developed numerous models of flycatcher breeding habitat at Roosevelt Lake, AZ. For model development and testing, we compiled 10 years of flycatcher territory data that were obtained from intensive fieldwork between 1996 and 2005. We identified riparian vegetation annually in the project area from Landsat Thematic Mapper images, and extracted floodplain features from a digital elevation model. We created a novel class of temporal (i.e., multiyear) variables by characterizing the stability and variability in breeding habitat over a 6-year time interval. We used logistic regression to determine associations between environmental variables and flycatcher territory occurrence, and to test specific hypotheses. We mapped the probability of territory occurrence with a GIS and determined model accuracies with a classification table and a 10-year population database. Environmental features that were associated with breeding flycatchers included floodplain size, proximity to water, and the density, heterogeneity, age and stability of riparian vegetation. Our best model explained 79% of the variability in the flycatcher breeding population at Roosevelt Lake. The majority of predicted flycatcher habitat formed between 1996 and 2004 on an exposed lakebed ~3 years after water levels receded during a prolonged drought. A high correlation between annual reservoir levels and predicted breeding habitat (r = ?0.82) indicates that we can create and manage habitat for conservation purposes. Our predictive models quantify and assess the relative quality of flycatcher breeding habitat remotely, and can be used to evaluate the effectiveness of habitat restoration activities. Numerous techniques we developed can be used to characterize riparian vegetation and patch dynamics directly off of satellite imagery, thereby increasing its utility for conservation purposes. 相似文献
352.
M.J. Metzger R.G.H. Bunce M. van Eupen M. Mirtl 《Journal of environmental management》2010,91(6):1357-1365
Integration of European long term ecosystem research (LTER) would provide important support for the management of the pan-European environment and ecosystems, as well as international policy commitments. This does require appropriate coverage of Europe and standardised frameworks and research methods between countries. Emerging interest in socio-ecological systems prompted the present assessment of the distribution of LTER activities across European socio-ecological gradients. This paper presents a European stratification with a 1 km2 resolution, delineating 48 broad socio-ecological regions. The dataset is based on an existing biogeophysical stratification constructed using multivariate clustering of mainly climatic variables and a newly developed socio-economic stratification based on an economic density indicator. The coverage of European LTER facilities across the socio-ecological gradients is tested using this dataset. The analysis shows two strong biases in the present LTER effort. Firstly, urban and disturbed regions are consistently under-represented, illustrating a bias for traditional ecological research away from human activity. Secondly, the Mediterranean, for which some of the most extreme global change impacts are projected, is receiving comparatively little attention. Both findings can help guide future investment in the European LTER network – and especially in a Long Term Socio-Ecological Research (LTSER) component– to provide a more balanced coverage. This will provide better scientific understanding of pan-European environmental concerns and support the management of natural resources and international policy commitments in the European Union. 相似文献
353.
Hye-Jin Kim Kyung-Suk Cho Mark N. Goltz Jee-Hyeong Khim Jae Young Kim 《Journal of the Air & Waste Management Association (1995)》2013,63(8):1237-1244
ABSTRACT To test the possible use of composted food waste and wastewater sludge as biofilters to treat gas-phase volatile organic compounds (VOCs), batch experiments were conducted with an isolated strain that could degrade aromatic compounds under aerobic conditions. A benzene and trichloroethylene (TCE) mixture was used as the gas-phase pollutant in experiments with composted food waste, sludge, and soil. Under aerobic conditions, benzene was degraded as a primary substrate and TCE was degraded cometabolically, with water contents varying from 6 to 60% (volume of water added/volume of solid). Optimal water content for VOC removal was 12% for the soil, 36% for the composted food waste, and 48% for the sludge. The extent of VOC sorption and biodegradation at the optimal water content was different for each material. With the same initial VOC concentration, more VOCs were removed by sorption onto the composted food waste and the sludge, while less VOCs were biodegraded in comparison with the results using soil. The reason the biodegradation in the soil was greater may be partly attributed to the fact that, due to less sorption, the aqueous-phase concentration of VOCs, which microorganisms could utilize as a carbon source or cometabolize, was higher. We also speculate that the distribution of microorganisms in each medium affects the rate of biodegradation. A large number of microorganisms were attached to the composted food waste and sludge. Mass transfer of VOCs and oxygen to these microorganisms, which appear to have been heterogeneously distributed in clusters, may have been limited, resulting in hindered biodegradation. 相似文献
354.
Characterizing sources of nitrate leaching from an irrigated dairy farm in Merced County, California
Martin L. van der Schans Thomas Harter Anton Leijnse Marsha C. Mathews Roland D. Meyer 《Journal of contaminant hydrology》2009,110(1-2):9-21
Dairy farms comprise a complex landscape of groundwater pollution sources. The objective of our work is to develop a method to quantify nitrate leaching to shallow groundwater from different management units at dairy farms. Total nitrate loads are determined by the sequential calibration of a sub-regional scale and a farm-scale three-dimensional groundwater flow and transport model using observations at different spatial scales. These observations include local measurements of groundwater heads and nitrate concentrations in an extensive monitoring well network, providing data at a scale of a few meters and measurements of discharge rates and nitrate concentrations in a tile-drain network, providing data integrated across multiple farms. The various measurement scales are different from the spatial scales of the calibration parameters, which are the recharge and nitrogen leaching rates from individual management units. The calibration procedure offers a conceptual framework for using field measurements at different spatial scales to estimate recharge N concentrations at the management unit scale. It provides a map of spatially varying dairy farming impact on groundwater nitrogen. The method is applied to a dairy farm located in a relatively vulnerable hydrogeologic region in California. Potential sources within the dairy farm are divided into three categories, representing different manure management units: animal exercise yards and feeding areas (corrals), liquid manure holding ponds, and manure irrigated forage fields. Estimated average nitrogen leaching is 872 kg/ha/year, 807 kg/ha/year and 486 kg/ha/year for corrals, ponds and fields respectively. Results are applied to evaluate the accuracy of nitrogen mass balances often used by regulatory agencies to assess groundwater impacts. Calibrated leaching rates compare favorably to field and farm scale nitrogen mass balances. These data and interpretations provide a basis for developing improved management strategies. 相似文献
355.
356.
William A. McClenny S. Mark Schmidt Keith G. Kronmiller 《Journal of the Air & Waste Management Association (1995)》2013,63(1):64-69
ABSTRACT Dalton's law of partial pressures and the hypothesis that water vapor equilibrium in a canister is identical to that established above liquid water are used to predict the variation of the percent relative humidity (%RH) of air released from canisters used in ambient air sampling, typically 6-L canisters pressurized with 18 L of air. When (and if) the water vapor partial pressure in a canister exceeds its saturation vapor pressure, water vapor condensation begins and the condensation rate equals the sampling rate of water vapor into the canister. Under constant temperature conditions, the air subsequently released from the canister is less humid than the original sample, following the relationship %RH = 100% (6 L/Vs) for Vs> Vr, where Vs is the residual air volume (referenced to atmospheric pressure), and Vr is shown to depend on the %RH of the ambient air sample. Vr is the residual air volume at which water is completely removed (except for adsorbed water vapor) from the canister wall. For Vs < Vr, the predicted %RH is constant and equal to its value at Vr. Experimental values agree reasonably well with predictions at both high (90%) and low (34%) RH. However, experimental values are often slightly displaced (usually towards lower values of %RH) for mid-range %RH (61%) and variations in %RH near Vr change from canister to canister. 相似文献
357.
Alistair J. Wilson Mark Dean James P. Higham 《Behavioral ecology and sociobiology》2013,67(9):1399-1415
Over the last few decades the animal communication community has become increasingly aware that much communication occurs using multiple signals in multiple modalities. The majority of this work has been empirical, with less theoretical work on the advantages conferred by such communication. In the present paper, we ask: Why should animals communicate with multiple signals in multiple modalities? To tackle this question we use game theoretic techniques, and highlight developments in the economic signaling literature that might offer insight into biological problems. We start by establishing a signaling game, and investigate signal honesty under two prevailing paradigms of honest communication – costly signaling and cheap talk. In both paradigms, without further constraint, it is simple to show that anything that can be achieved with multiple signals can be achieved with one. We go on to investigate different sets of possible constraints that may make multiple signals and multimodal signals in particular more likely to evolve. We suggest that constraints on cost functions and bandwidths, orthogonal noise across modalities, strategically distinct modes, multiple qualities, multiple signalers, and multiple audiences, all provide biologically plausible scenarios that theoretically favor multiple and multimodal signaling. 相似文献
358.
Kees van Leeuwen 《Environmental management》1990,14(6):779-792
In a recently published annex to the National Environmental Policy Plan of the Netherlands (1989), attention was paid to ecotoxicological
effects assessment. The proposed procedure was based on the advice of the Health Council of the Netherlands (1989) on risk
assessment of toxic chemicals for ecosystems. The various extrapolation methods described by the Health Council are critically
discussed in this paper. The extrapolation method of Van Straalen and Denneman (1989) is evaluated for eight chemicals and
11 aquatic species. Conclusions are drawn about the quality and quantity of the ecotoxicological data needed for aquatic effects
assessment. For the soil—a compartment that is often at risk—ecotoxicological effects assessment is not possible because suitable
ecotoxicological test methods still have to be developed. 相似文献
359.
The premise of this article is that the planning and design of new rest camps in conservation areas should be based on ecological
principles in such a way that the plant ecology within the camp be an integral part and extension of the natural ecology of
its immediate vicinity. This is desirable so that visitors to the camp will be provided not only with facilities for resting,
eating, and sleeping, but also be able to enjoy and study the natural environment in a relaxed atmosphere. The Berg-en-Dal
rest camp, which was established in Kruger National Park, was planned in such a way and designed according to the principles
outlined by the authors in a companion article.
The planning included six zones: a control zone, day visitor zone, overnight visitor zone, staff accommodation zone, recreation
zone, and service zone. The point is stressed that plant species selected to be used as additional vegetation to those already
growing in the camp were endemic to the nine landscape facets identified in the camp. The design allowed for separation of
the various land-use zones in such a way that they would complement each other rather than be a hindrance to each other. The
camp has been built according to the plans included in this article and has proved to be a great success. The conclusion is
drawn that the planning principles are sound and should be used in the future for the planning and design of rest camps for
conservation areas in South Africa. 相似文献
360.
Gregory J. McCabe David M. Wolock Lauren E. Hay Mark A. Ayers 《Journal of the American Water Resources Association》1990,26(4):633-643
ABSTRACT: The Thornthwaite moisture index is a useful indicator of the supply of water (precipitation) in an area relative to the demand for water under prevailing climatic conditions (potential evapotranspiration). This study examines the effects of changes in climate (temperature and precipitation) on the Thornthwaite moisture index in the conterminous United States. Estimates of changes in mean annual temperature and precipitation for doubled-atmospheric CO2 conditions derived from three general circulation models (GCMs) are used to study the response of the moisture index under steady-state doubled-CO2 conditions. Results indicate that temperature and precipitation changes under doubled-CO2 conditions generally will cause the Thornthwaite moisture index to decrease, implying a drier climate for most of the United States. The pattern of expected decrease is consistent among the three GCMs, although the amount of decrease depends on which GCM climatic-change scenario is used. Results also suggest that changes in the moisture index are related mainly to changes in the mean annual potential evapotranspiration as a result of changes in the mean annual temperature, rather than to changes in the mean annual precipitation. 相似文献