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101.
Assessment of patch quality by ladybirds: relative response to conspecific and heterospecific larval tracks a consequence of habitat similarity? 总被引:2,自引:0,他引:2
Alexandra Magro Joseph N. Téné Nicolas Bastin Anthony F. G. Dixon Jean-Louis Hemptinne 《Chemoecology》2007,17(1):37-45
Summary. Aphid colonies can reach high levels of abundance but last for short periods of time. The larvae of aphidophagous ladybirds
(Coleoptera: Coccinellidae) that feed on these colonies might therefore suffer from starvation, which favours the occurrence
of cannibalism and intraguild predation. Thus, the assessment of patch quality becomes crucial and it has been shown that
female ladybirds refrain from laying eggs in the presence of an oviposition deterring semiochemical deposited by their larvae.
Adalia bipunctata (L.), Adalia decempunctata (L.) and Coccinella septempunctata L. are 3 sympatric species of ladybirds, which can co-occur in aphid colonies. As a consequence, their eggs and larvae are
under threat, not only from cannibalism but also intraguild predation. Females should, therefore, also use the tracks deposited
by heterospecific larvae to assess the quality of aphid colonies as oviposition sites. The expectation is that: 1- the strength
of the reaction to each other’s larval tracks should be correlated with percentage habitat overlap and that 2- the reaction
to conspecific larval tracks should be stronger than to heterospecific tracks. In order to test these hypotheses, females’
oviposition behaviour was analysed and a chemical analysis of the tracks of their larvae undertaken.
The results show that oviposition behaviour is not related to habitat overlap. Both species of Adalia react to tracks of their own larvae and those of C. septempunctata, but A. decempunctata reacted more strongly than A. bipunctata. C. septempunctata reacted very slightly to its own tracks but not to those of either species of Adalia.
The larval tracks are mainly composed of alkanes. Those of the two species of Adalia are qualitatively 100% similar and 60% so when the quantitative results are compared. They are, however, only 24–29% similar
to those of Coccinella septempunctata. 相似文献
102.
Although most long-term studies of consumer-resource (e.g., predator-prey) interactions select species showing cyclic population dynamics, strong consumer-resource interactions can also produce irregular, noncyclic dynamics. Here, we present a case in which a seed predator, the tephritid fruit fly Euphranta connexa, shows fluctuations in density of more than two orders of magnitude over a 22-year period. To explain these fluctuations, we analyzed a stage-specific data set to quantify the density-dependent and density-independent components of larval survivorship and realized fecundity. Both larval survivorship and realized fecundity were strongly density dependent. Larval survivorship dropped from 0.62 at low larval density to 0.081 at high larval density, whereas fecundity dropped from 84.3 to 0.32 eggs per individual, more than a 100-fold decrease. We divided density-independent variation in E. connexa population dynamics into components for variability in (1) larval survivorship, (2) realized fecundity, and (3) annual fruit abundance. Of these components, 96% of the density-independent variance in per capita population growth rates was caused by fluctuations in fruit abundance. This highlights the importance of the strong consumer-resource interactions in driving fluctuations in E. connexa abundance. It also demonstrates that E. connexa dynamics are remarkably simple, and aside from the 4% of unexplained variance in per capita population growth rates, our understanding of E. connexa dynamics is remarkably complete. 相似文献
103.
The influence of successional processes and disturbance on the structure of Tsuga canadensis forests
Old-growth forests are valuable sources of ecological, conservation, and management information, yet these ecosystems have received little study in New England, due in large part to their regional scarcity. To increase our understanding of the structures and processes common in these rare forests, we studied the abundance of downed coarse woody debris (CWD) and snags and live-tree size-class distributions in 16 old-growth hemlock forests in western Massachusetts. Old-growth stands were compared with eight adjacent second-growth hemlock forests to gain a better understanding of the structural differences between these two classes of forests resulting from contrasting histories. In addition, we used stand-level dendroecological reconstructions to investigate the linkages between disturbance history and old-growth forest structure using an information-theoretic model selection framework. Old-growth stands exhibit a much higher degree of structural complexity than second-growth forests. In particular, old-growth stands had larger overstory trees and greater volumes of downed coarse woody debris (135.2 vs. 33.2 m3/ha) and snags (21.2 vs. 10.7 m3/ha). Second-growth stands were characterized by either skewed unimodal or reverse-J shaped diameter distributions, while old-growth forests contained bell-shaped, skewed unimodal, rotated sigmoid, and reverse J-shaped distributions. The variation in structural attributes among old-growth stands, particularly the abundance of downed CWD, was closely related to disturbance history. In particular, old-growth stands experiencing moderate levels of canopy disturbance during the last century (1930s and 1980s) had greater accumulations of CWD, highlighting the importance of gap-scale disturbances in shaping the long-term development and structural characteristics of old-growth forests. These findings are important for the development of natural disturbance-based silvicultural systems that may be used to restore important forest characteristics lacking in New England second-growth stands by integrating structural legacies of disturbance (e.g., downed CWD) and resultant tree-size distribution patterns. This silvicultural approach would emulate the often episodic nature of CWD recruitment within old-growth forests. 相似文献
104.
"二噁英"是指具有相似化学结构和生物特征的一族化合物,分别属于三大类别:多氯代二苯并二噁英(PC-DDs),多氯代二苯并呋喃(PCDFs)以及多氯联苯(PCBs).PCDDs和PCDFs无商业目的性生产,而是在大量的人类活动中产生的.自然过程也可以产生PCDDs和PCDFs.在过去的十年里,环境立法机构和企业一起致力于减少二噁英的排放. 相似文献
105.
Increasing abundance of geese in North America and Europe constitutes a major conservation success, but has caused increasing conflicts with economic, health and safety interests, as well as ecosystem impacts. Potential conflict resolution through a single, ‘one size fits all’ policy is hindered by differences in species’ ecology, behaviour, abundance and population status, and in contrasting political and socio-economic environments across the flyways. Effective goose management requires coordinated application of a suite of tools from the local level to strategic flyway management actions. The European Goose Management Platform, established under the Agreement on the Conservation of African-Eurasian Migratory Waterbirds, aims to harmonise and prioritise management, monitoring and conservation efforts, sharing best practice internationally by facilitating agreed policies, coordinating flyway efforts, and sharing and exchanging experiences and information. This depends crucially upon adequate government financing, the collection of necessary monitoring data (e.g., on distribution, abundance, hunting bags, demography, ecosystem and agricultural damage), the collation and effective use of such data and information, as well as the evaluation of outcomes of existing management measures. 相似文献
106.
Influence of Riparian Seepage Zones on Nitrate Variability in Two Agricultural Headwater Streams 下载免费PDF全文
Mark R. Williams Anthony R. Buda Herschel A. Elliott Kamini Singha James Hamlett 《Journal of the American Water Resources Association》2015,51(4):883-897
Riparian seeps have been recognized for their contributions to stream flow in headwater catchments, but there is limited data on how seeps affect stream water quality. The objective of this study was to examine the effect of seeps on the variability of stream NO3‐N concentrations in FD36 and RS, two agricultural catchments in Pennsylvania. Stream samples were collected at 10‐m intervals over reaches of 550 (FD36) and 490 m (RS) on 21 occasions between April 2009 and January 2012. Semi‐variogram analysis was used to quantify longitudinal patterns in stream NO3‐N concentration. Seep water was collected at 14 sites in FD36 and 7 in RS, but the number of flowing seeps depended on antecedent conditions. Seep NO3‐N concentrations were variable (0.1‐29.5 mg/l) and were often greater downslope of cropped fields compared to other land uses. During base flow, longitudinal variability in stream NO3‐N concentrations increased as the number of flowing seeps increased. The influence of seeps on the variability of stream NO3‐N concentrations was less during storm flow compared to the variability of base flow NO3‐N concentrations. However, 24 h after a storm in FD36, an increase in the number of flowing seeps and decreasing streamflow resulted in the greatest longitudinal variability in stream NO3‐N concentrations recorded. Results indicate seeps are important areas of NO3‐N delivery to streams where targeted adoption of mitigation measures may substantially improve stream water quality. 相似文献
107.
Keri L. Christensen Anthony P. Gallacher Lizzie Martin Desmond Tong Mark A. Elgar 《Die Naturwissenschaften》2010,97(10):941-944
The geometric framework model predicts that animal foraging decisions are influenced by their dietary history, with animals targeting a combination of essential nutrients through compensatory foraging. We provide experimental confirmation of nutrient-specific compensatory foraging in a natural, free-living population of social insects by supplementing their diet with sources of protein- or carbohydrate-rich food. Colonies of the ant Iridomyrmex suchieri were provided with feeders containing food rich in either carbohydrate or protein for 6 days, and were then provided with a feeder containing the same or different diet. The patterns of recruitment were consistent with the geometric framework: while feeders with a carbohydrate diet typically attracted more workers than did feeders with protein diet, the difference in recruitment between the two nutrients was smaller if the colonies had had prior access to carbohydrate than protein. Further, fewer ants visited feeders if the colony had had prior access to protein than to carbohydrates, suggesting that the larvae play a role in worker foraging behaviour. 相似文献
108.
传统的土地利用变化监测方法已无法完全满足当前经济的快速发展和城市急剧扩张的要求,利用光学遥感数据对地观测也受到天气和云层覆盖等诸多因素的限制。而Radarsat-1等雷达遥感数据可以在"全天候"的条件下对地表进行观测。论文以Radarsat-1图像获取的24 d时间周期为最短时间间隔,分析了24 d、48 d和72 d时间间隔下的土地利用变化监测,对短时间间隔内的土地利用变化监测的结果进行了总结。监测的结果需要在精度与时间间隔之间做出取舍。对于大部分的情况,24 d的时间间隔已可以得到60%以上精度的结果,部分月份的监测需要48 d的监测时间间隔。若需要更高的精度,则需要72 d甚至更长。 相似文献
109.
Ángel F. Herrera-Ulloa Anthony T. Charles Salvador E. Lluch-Cota Hermán Ramirez-Aguirre Sergio Hernández-Váquez Alfredo Ortega-Rubio 《国际发展与全球生态学杂志》2013,20(4):353-360
Sustainable development, as a multi-dimensional concept, is difficult to measure. Some efforts using indicators and indices have appeared in recent years, but most were developed on a national scale. Use of sustainability indicators has proven valuable for attaining better management of the environment by minimizing information gaps and maximizing community capabilities in terms of economic, social, environmental, and institutional sustainability dimensions. However, at least in the case of developing countries, the potential exists that national sustainability measures, based on national level indicators, may mask problems in sub-national zones with highly unsustainable conditions. This paper proposes a methodology to evaluate sustainable development at a local level, the use of which could be helpful in comparing different regions within a country or even among different countries. National sustainability indicators should result from a combination (whether additive or proportional) of regional sustainability indicators, as developed in this paper. 相似文献
110.
Hosein Ghaedi Payam Kalhor Ming Zhao Peter T. Clough Edward J. Anthony Paul S. Fennell 《Frontiers of Environmental Science & Engineering》2022,16(7):92