全文获取类型
收费全文 | 875篇 |
免费 | 10篇 |
国内免费 | 15篇 |
专业分类
安全科学 | 51篇 |
废物处理 | 20篇 |
环保管理 | 125篇 |
综合类 | 140篇 |
基础理论 | 220篇 |
环境理论 | 1篇 |
污染及防治 | 222篇 |
评价与监测 | 79篇 |
社会与环境 | 34篇 |
灾害及防治 | 8篇 |
出版年
2023年 | 7篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 14篇 |
2016年 | 18篇 |
2015年 | 24篇 |
2014年 | 15篇 |
2013年 | 99篇 |
2012年 | 35篇 |
2011年 | 59篇 |
2010年 | 41篇 |
2009年 | 44篇 |
2008年 | 54篇 |
2007年 | 44篇 |
2006年 | 34篇 |
2005年 | 30篇 |
2004年 | 27篇 |
2003年 | 26篇 |
2002年 | 33篇 |
2001年 | 16篇 |
2000年 | 17篇 |
1999年 | 6篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 11篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1971年 | 4篇 |
1969年 | 4篇 |
1960年 | 4篇 |
1956年 | 3篇 |
排序方式: 共有900条查询结果,搜索用时 15 毫秒
111.
Frank C. Curriero Michael E. Hohn Andrew M. Liebhold Subhash R. Lele 《Environmental and Ecological Statistics》2002,9(1):89-110
Geostatistics is a set of statistical techniques that is increasingly used to characterize spatial dependence in spatially referenced ecological data. A common feature of geostatistics is predicting values at unsampled locations from nearby samples using the kriging algorithm. Modeling spatial dependence in sampled data is necessary before kriging and is usually accomplished with the variogram and its traditional estimator. Other types of estimators, known as non-ergodic estimators, have been used in ecological applications. Non-ergodic estimators were originally suggested as a method of choice when sampled data are preferentially located and exhibit a skewed frequency distribution. Preferentially located samples can occur, for example, when areas with high values are sampled more intensely than other areas. In earlier studies the visual appearance of variograms from traditional and non-ergodic estimators were compared. Here we evaluate the estimators' relative performance in prediction. We also show algebraically that a non-ergodic version of the variogram is equivalent to the traditional variogram estimator. Simulations, designed to investigate the effects of data skewness and preferential sampling on variogram estimation and kriging, showed the traditional variogram estimator outperforms the non-ergodic estimators under these conditions. We also analyzed data on carabid beetle abundance, which exhibited large-scale spatial variability (trend) and a skewed frequency distribution. Detrending data followed by robust estimation of the residual variogram is demonstrated to be a successful alternative to the non-ergodic approach. 相似文献
112.
Frank Götmark 《Behavioral ecology and sociobiology》1997,40(1):41-49
Conspicuous color patterns in birds may lead to increased risk of predation. Alternatively, bright birds may be aposematic
or unprofitable prey, which leads to decreased predation. During four autumns, I examined whether the black-and-white plumage
of (stuffed) magpies Pica pica increases or reduces the risk of attack by migrating goshawks Accipiter gentilis. Attack risk was higher for normal magpies than for cryptic, brown magpies whether the mounts were placed near one another
or far apart. However, the brown magpie may have been avoided because of its novelty. For magpies and cryptic jays Garrulus glandarius exposed together, the attack risk was similar. In 2 years, magpie and jay mounts were also exposed far apart. In 1994, with
an invasion of migrating jays, attack risk was much higher for jays than for magpies. In 1995, with a normal density of jays,
hawks attacked the magpies more often. The results demonstrate frequency-dependent prey selection by goshawks, which would
influence any predation cost of bright plumage. The attacks on normally colored magpie mounts suggest that magpies are not
aposematic. Trials with photographs and human observers indicated that normal magpies were somewhat easier to detect than
jays. The plumage of the magpie possibly increases the risk of predation, but may be favoured by sexual or social selection.
Received: 18 January 1996 / Accepted after revision: 6 October 1996 相似文献
113.
114.
115.
Katrin Palitzsch Sabine Göllner Kristina Lupa Jörg Matschullat Corinna Messal Kirsten Pleßow Mandy Schipek Ivonne Schnabel Christian Weller Frank Zimmermann 《Environmental Sciences Europe》2005,17(4):231-241
The trend of rising ozone concentrations in forest ecosystems and the phytotoxicity of ozone demand a realistic risk assessment according to an internationally accepted and flux-based quality standard. Ozone fluxes within the canopy are influenced by chemical gas-phase reactions with nitrogen oxide and biogenic hydrocarbons and by surface deposition processes. Therefore, a differentiation of the ozone flux within the canopy is needed between stomatal uptake and other transport pathways. The Eddy Covariance technique is the method of choice for the determination of trace gas fluxes relevant for ozone chemistry. This method is also used for stomatal conductance measurements based on evapotranspiration fluxes and for emission measurements of biogenic hydrocarbons by PTR-MS. Although considerably research efforts were directed to canopy measurements in recent years, the underlying processes are not fully understood yet. Thus, major differences occur in the ratios of stomatal ozone uptake, non-stomatal deposition and gas-phase chemistry between different studies. Furthermore, the vertical concentration gradients within the canopy measured at several forest sites are rather inconsistent and the existing deposition models do rarely account for chemical transformation and detoxification processes. Only a simultaneous measurement of all photochemically relevant trace gases, plant physiological parameters at different sites and forest species over entire vegetation periods, and model parameterization according to the measurement results from the experimental sites will contribute to the clarification of the canopy processes and will ensure realistic risk assessments. 相似文献
116.
Allogeneic assays were conducted in situ on the Red Sea hydrocoral Millepora dichotoma. Forty-five pairwise combinations among ten colonies and ten control isografts were set up in four replicates each (180 and 40 pairs, respectively) and followed for up to 8 mo in the Gulf of Eilat, Red Sea in 1992–1993. In 42 allogeneic combinations we recorded a reproducible and unilateral tissue and skeleton overgrowth which developed within the first 10 wk up to 20 mm. Following the development of these primary overgrowths, four types of secondary responses were observed among most incompatible combinations: reversals in overgrowth directionality, tissue necroses, stand-offs and abnormal growth patterns. Secondary responses within a given set of replicates of most allogeneic combinations were characterized by high variability in type and intensity of response. Based on the outcomes of primary overgrowths, a complex nontransitive hierarchy was constructed for the ten colonies. All isografts and three allogeneic combinations fused within 3 wk. Fusion pattern between the three allogeneic combinations was nontransitive: one M. dichotoma colony repeatedly fused with two other colonies (four assays each). However, these two colonies not only did not fuse with each other, but one of them repeatedly overgrew its confrére. In the third compatible combination, the most superior and the most inferior colonies in the network of hierarchies among the ten colonies, fused in all tested assays. These results are compared with allogeneic outcomes in other enidarians, where nontransitive fusion between allogenic colonies have never been recorded. 相似文献
117.
Malte Andersson Frank Götmark Christer G. Wiklund 《Behavioral ecology and sociobiology》1981,9(3):199-202
Summary The information-centre hypothesis suggests that bird colonies function as sources of information about good feeding sites, to which unsuccessful birds may follow foragers. One assumption of the hypothesis is that unusually successful foragers are followed by other colony members when returning to a newly found, rich food source. We tested this assumption in a colony of Black-headed Gulls (Larus ridibundus). Parents feeding their young from a rich, artificial food source were observed on their return trips to the feeding site. In none of 50 cases did other colony members follow them to the newly found food. However, the gulls were attracted to groups of foraging conspecifics. In experiments with paired food piles and a group of model gulls at one pile in each pair, Black-headed Gulls always alighted first at the piles with models. Hence the information-centre mechanism was refuted, but the gulls did acquire food information from each other in another way. 相似文献
118.
成百上千的活性物质正被用于人药和兽药处方中.由于药物的广泛应用,它们的残留物可通过多种途径进入环境.虽然主要通过尿和粪便的排泄,但是药品生产中的排放也应被考虑.当抗生素用于水产业,就会产生更直接的影响.污水处理设备不能完全除去药物,因此药物会出现在地表和地下水样品中.近年来,人们对环境中药物的兴趣正在增加,需要建立一种快速、灵敏、有选择性的方法来分析水样. 相似文献
119.
Palaeobiological evidence indicates that gymnosperms were wind-pollinated and that insect pollination began in angiosperms in the Lower Cretaceous (ca. 135 mya) leading to close associations between higher plants and their pollinators. Cycads, which were widespread and pervasive throughout the Mesozoic (250-65 mya) are among the most primitive living seed-plants found today. Because pollination by beetles and by thrips has now been detected in several modern cycads, it is attractive to speculate that some insects and cycads had already developed similar mutualistic interactions in the Triassic (250-205 mya), long before the advent of angiosperms. We also draw attention to another key factor in this insect-plant relationship, namely secondary, defensive plant substances which must always have controlled interspecific interactions. Cycads mainly produce toxic azoglucosides and neurotoxic non-protein amino acids (e.g. BMAA), which apparently are crucial elements in the development and maintenance of mutualism (pollination) and parasitism (herbivory) by cycad-linked herbivores. We now add new results on the uptake and storage of the main toxin, cycasin, of the Mexican cycad Zamia furfuracea by its pollinator, the weevil Rhopalotria mollis, and by a specialist herbivore of Zamia integrifolia, the aposematic Atala butterfly Eumaeus atala. 相似文献
120.