全文获取类型
收费全文 | 764篇 |
免费 | 10篇 |
国内免费 | 4篇 |
专业分类
安全科学 | 59篇 |
废物处理 | 42篇 |
环保管理 | 137篇 |
综合类 | 67篇 |
基础理论 | 230篇 |
环境理论 | 1篇 |
污染及防治 | 154篇 |
评价与监测 | 61篇 |
社会与环境 | 23篇 |
灾害及防治 | 4篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 9篇 |
2016年 | 17篇 |
2015年 | 13篇 |
2014年 | 19篇 |
2013年 | 76篇 |
2012年 | 23篇 |
2011年 | 46篇 |
2010年 | 31篇 |
2009年 | 26篇 |
2008年 | 28篇 |
2007年 | 31篇 |
2006年 | 50篇 |
2005年 | 21篇 |
2004年 | 18篇 |
2003年 | 26篇 |
2002年 | 33篇 |
2001年 | 23篇 |
2000年 | 27篇 |
1999年 | 12篇 |
1998年 | 15篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1969年 | 3篇 |
排序方式: 共有778条查询结果,搜索用时 281 毫秒
141.
142.
Abayomi A Nimmo M Williams C Olayinka KO Osuntogun B Alo B Worsfold PJ 《Journal of environmental monitoring : JEM》2011,13(7):1884-1889
Roadside soils were sampled from the Lagos Lagoon catchment during the wet and dry seasons over the period 2005-2009. Lagoon sediment samples were also collected within the same period. All samples were digested with aqua regia to determine total phosphorus and extracted with 0.5 M sodium bicarbonate to determine the bioavailable fraction (Olsen-P). A segmented flow analyser method was used for analysis and good accuracy was demonstrated for two reference soils (SO-2 from CCMET and SRM 2711 from NIST). The Lagos Lagoon is a hypereutrophic water body (1270 ± 1170 μg P L(-1)), with significant areas of anoxia and water hyacinth growth. The total phosphorus concentrations in roadside soils (16 sites; mean ± 2 S.D.) were 285 ± 279 mg kg(-1) in the wet season and 424 ± 629 mg kg(-1) in the dry season, indicating that rainwater leaching is a major source of phosphorus in the lagoon. The bioavailable fractions were 5.17 ± 3.47 mg kg(-1) (2.1 ± 1.5% of the total) in the wet season and 13.0 ± 8.7 mg kg(-1) (4.3 ± 4.5% of the total) in the dry season. 相似文献
143.
Cindy E. Hauser Katherine M. Giljohann Michael A. McCarthy Georgia E. Garrard Andrew P. Robinson Nicholas S. G. Williams Joslin L. Moore 《Conservation biology》2022,36(3):e13888
Surveys aimed at finding threatened and invasive species can be challenging due to individual rarity and low and variable individual detection rates. Detection rate in plant surveys typically varies due to differences among observers, among the individual plants being surveyed (targets), and across background environments. Interactions among these 3 components may occur but are rarely estimated due to limited replication and control during data collection. We conducted an experiment to investigate sources of variation in detection of 2 Pilosella species that are invasive and sparsely distributed in the Alpine National Park, Australia. These species are superficially similar in appearance to other yellow-flowered plants occurring in this landscape. We controlled the presence and color of flowers on target Pilosella plants and controlled their placement in plots, which were selected for their variation in cover of non-target yellow flowers and dominant vegetation type. Observers mimicked Pilosella surveys in the plots and reported 1 categorical and 4 quantitative indicators of their survey experience level. We applied survival analysis to detection data to model the influence of both controlled and uncontrolled variables on detection rate. Orange- and yellow-flowering Pilosella in grass- and heath-dominated vegetation were detected at a higher rate than nonflowering Pilosella. However, this detection gain diminished as the cover of other co-occurring yellow-flowering species increased. Recent experience with Pilosella surveys improved detection rate. Detection experiments are a direct and accessible means of understanding detection processes and interpreting survey data for threatened and invasive species. Our detection findings have been used for survey planning and can inform progress toward eradication. Interaction of target and background characteristics determined detection rate, which enhanced predictions in the Pilosella eradication program and demonstrated the difficulty of transferring detection findings into untested environments. 相似文献
144.
Masahiro Nakaoka Masatoshi Matsumasa Tetsuhiko Toyohara Susan L. Williams 《Marine Biology》2008,153(4):589-598
Eelgrass, Zostera marina, produces two types of shoots: morphologically simple vegetative shoots and highly branched flowering (reproductive) shoots,
the latter found only in summer months. We examined whether the abundance and diversity of mobile epifaunal assemblage are
affected by the presence of flowering shoots in an eelgrass meadow of Otsuchi Bay, northeastern Japan. Comparisons of epifauna
in natural vegetation revealed that density and species richness did not differ significantly between sites consisting of
both flowering and vegetative shoots, and those only of vegetative shoots. A transplant experiment, conducted to examine the
colonization rates of epifauna to defaunated eelgrass planted with different combination of vegetative and flowering shoots,
showed no obvious variation in abundance and species richness. At species level, the density of some species such as a tanaid
Zeuxo sp. and a polychaete Platynereis sp. was higher at sites and/or treatments with flowering shoots, whereas that of some gastropods, such as Lirularia iridescens and Siphonacmea oblongata was higher at sites without flowering shoots. The species-specific response led to dissimilarity of epifaunal assemblage
between sites and among treatments with different densities of vegetative and flowering shoots. Similar patterns observed
for natural vegetation and the transplant experiment suggest that the variation in assemblage structure is caused by habitat
selection of each species, for example, the utilization of flowering shoots as feeding ground and nursery by Zeuxo sp. 相似文献
145.
Christopher J. Williams Patricia J. Heglund 《Environmental and Ecological Statistics》2009,16(4):495-513
Habitat association models are commonly developed for individual animal species using generalized linear modeling methods
such as logistic regression. We considered the issue of grouping species based on their habitat use so that management decisions
can be based on sets of species rather than individual species. This research was motivated by a study of western landbirds
in northern Idaho forests. The method we examined was to separately fit models to each species and to use a generalized Mahalanobis
distance between coefficient vectors to create a distance matrix among species. Clustering methods were used to group species
from the distance matrix, and multidimensional scaling methods were used to visualize the relations among species groups.
Methods were also discussed for evaluating the sensitivity of the conclusions because of outliers or influential data points.
We illustrate these methods with data from the landbird study conducted in northern Idaho. Simulation results are presented
to compare the success of this method to alternative methods using Euclidean distance between coefficient vectors and to methods
that do not use habitat association models. These simulations demonstrate that our Mahalanobis-distance-based method was nearly
always better than Euclidean-distance-based methods or methods not based on habitat association models. The methods used to
develop candidate species groups are easily explained to other scientists and resource managers since they mainly rely on
classical multivariate statistical methods. 相似文献
146.
L. Richard Little André E. Punt Bruce D. Mapstone Gavin A. Begg Barry Goldman Ashley J. Williams 《Ecological modelling》2009
Individual transferable quotas (ITQs) are increasingly seen as a way to make fisheries more profitable and halt over-capitalisation. ITQs allocate to users of a resource a share of a total allowable catch (TAC) which they are free to use, lease, or sell. We outline an approach to modelling the effect of an ITQ system in a multi-species, multi-sector fishery and apply it to the Coral Reef Fin Fish Fishery (CRFFF) in Queensland, Australia. An ITQ model, based on the assumption that operators seek to maximize profits, simulates the use of tradeable quota units by operators in the fishery, taking account of the initial quota allocation to operators, seasonal fish prices and individual operator variable costs, their fishing efficiency and experience, and constraints on vessel movements. Rationalization of the fishery is predicted to occur under an ITQ system for the CRFFF, which will lead to reductions in effort, increases in profits, and changes over time in quota prices. The ecological consequences of transferable quota in the multi-species fishery are seen in the catch and discard levels of the less profitable species, even though a TAC was set. This had flow-on effects on biomass. For example, simulations showed that the TAC for the primary target species, coral trout, was used more fully than that for a less valuable target species, red throat emperor, and that this was achieved through increased discarding of red throat emperor. Catches of both coral trout and red throat emperor that were derived from the model were higher than those recently observed in the fishery. The effort predicted by the model, however, closely approximated the actual effort observed in the fishery following implementation of ITQ management. 相似文献
147.
148.
C. Santhi J. G. Arnold J. R. Williams W. A. Dugas R. Srinivasan L. M. Hauck 《Journal of the American Water Resources Association》2001,37(5):1169-1188
ABSTRACT: The State of Texas has initiated the development of a Total Maximum Daily Load program in the Bosque River Watershed, where point and nonpoint sources of pollution are a concern. Soil Water Assessment Tool (SWAT) was validated for flow, sediment, and nutrients in the watershed to evaluate alternative management scenarios and estimate their effects in controlling pollution. This paper discusses the calibration and validation at two locations, Hico and Valley Mills, along the North Bosque River. Calibration for flow was performed from 1960 through 1998. Sediment and nutrient calibration was done from 1993 through 1997 at Hico and from 1996 through 1997 at Valley Mills. Model validation was performed for 1998. Time series plots and statistical measures were used to verify model predictions. Predicted values generally matched well with the observed values during calibration and validation (R2≥ 0.6 and Nash‐Suttcliffe Efficiency ≥ 0.5, in most instances) except for some underprediction of nitrogen during calibration at both locations and sediment and organic nutrients during validation at Valley Mills. This study showed that SWAT was able to predict flow, sediment, and nutrients successfully and can be used to study the effects of alternative management scenarios. 相似文献
149.
Steven J Phillips Paul Williams Guy Midgley Aaron Archer 《Ecological applications》2008,18(5):1200-1211
We introduce a new way of measuring and optimizing connectivity in conservation landscapes through time, accounting for both the biological needs of multiple species and the social and financial constraint of minimizing land area requiring additional protection. Our method is based on the concept of network flow; we demonstrate its use by optimizing protected areas in the Western Cape of South Africa to facilitate autogenic species shifts in geographic range under climate change for a family of endemic plants, the Cape Proteaceae. In 2005, P. Williams and colleagues introduced a novel framework for this protected area design task. To ensure population viability, they assumed each species should have a range size of at least 100 km2 of predicted suitable conditions contained in protected areas at all times between 2000 and 2050. The goal was to design multiple dispersal corridors for each species, connecting suitable conditions between time periods, subject to each species' limited dispersal ability, and minimizing the total area requiring additional protection. We show that both minimum range size and limited dispersal abilities can be naturally modeled using the concept of network flow. This allows us to apply well-established tools from operations research and computer science for solving network flow problems. Using the same data and this novel modeling approach, we reduce the area requiring additional protection by a third compared to previous methods, from 4593 km2 to 3062 km , while still achieving the same conservation planning goals. We prove that this is the best solution mathematically possible: the given planning goals cannot be achieved with a smaller area, given our modeling assumptions and data. Our method allows for flexibility and refinement of the underlying climate-change, species-habitat-suitability, and dispersal models. In particular, we propose an alternate formalization of a minimum range size moving through time and use network flow to achieve the revised goals, again with the smallest possible newly protected area (2850 km2). We show how to relate total dispersal distance to probability of successful dispersal, and compute a trade-off curve between this quantity and the total amount of extra land that must be protected. 相似文献
150.
Jonathan P. Williams Larry G. Allen Mark A. Steele Daniel J. Pondella II 《Marine Biology》2007,152(1):193-200
Studies of the impact of El Niño periods on marine species have usually focused on negative, highly visible effects, e.g., decreasing growth rates or increasing mortality due to a decline in primary productivity in typically nutrient rich upwelling zones; but positive effects related to elevated water temperature are also known. This study examined how the growth rate of juvenile white seabass, Atractoscion nobilis, responded to changes in ocean temperature in an El Niño period (1997–1998) in the northern portion of the Southern California Bight, USA. Growth rates of juvenile white seabass during their first 4 years of life were estimated as the slopes of linear relationships between body mass and age (from otoliths) of 800 fish collected at 11 stations throughout the bight. Growth rates differed significantly among cohorts hatched in 1996–2001. Specifically, white seabass that hatched in 1996 and 1997 grew significantly faster than those that hatched in 1998, 1999, and 2001. These differences in growth rates of cohorts appeared to be driven by variation in sea-surface temperature (SST). Growth rates averaged over the first three or 4 years of life were significantly positively correlated to average daily SST during the first 1–4 years of life. Increased growth of juvenile white seabass during the warm El Niño period likely provided a number of benefits to this warm-temperate species. This study demonstrated that some species will benefit from these warm-water periods despite reduced system-wide primary production. 相似文献