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Coal companies are reluctant to include wetland development in reclamation plans partly due to a lack of information on the
resulting characteristics of such sites. It is easier for coal companies to recreate terrestrial habitats than to attempt
experimental methods and possibly face significant regulatory disapproval. Therefore, we studied a young (10 years) wetland
on a reclaimed surface coal mine in southern Illinois so as to ascertain soil and water characteristics such that the site
might serve as a model for wetland development on surface mines. Water pH was not measured because of equipment problems,
but evidence (plant life, fish, herpetofauna) suggests suitable pH levels. Other water parameters (conductivity, salinity,
alkalinity, chloride, copper, total hardness, iron, manganese, nitrate, nitrite, phosphate, and sulfate) were measured, and
only copper was seen in potentially high concentrations (but with no obvious toxic effects). Soil variables measured included
pH, nitrate, nitrite, ammonia, potassium, calcium, magnesium, manganese, aluminum, iron, sulfate, chloride, and percent organic
matter. Soils were slightly alkaline and most parameters fell within levels reported for other studies on both natural and
manmade wetlands. Aluminum was high, but this might be indicative more of large amounts complexed with soils and therefore
unavailable, than amounts actually accessible to plants. Organic matter was moderate, somewhat surprising given the age of
the system. 相似文献
334.
P. Steven Porter Robert C. Ward 《Journal of the American Water Resources Association》1991,27(4):687-700
ABSTRACT: The statistical analysis of data which have trace level measurements has traditionally been a two-step process in which data are first censored using criteria based on measurement precision, and then analyzed with statistical methods for censored data. The process might be more informative if data were left uncensored. In this paper, information loss attributable to censoring and measurement noise are assessed by comparing the sample mean and median of uncensored measurements with a log regression mean and median based on censored data. Measurements are derived from lognormal parent distributions which have random variability characteristic of trace level measurement. The relative performance of estimators used with error-free samples and with samples having measurement noise can be explained by differences between the probability distributions of parents and measurements. Measurement introduces bias and dispersion and transforms lognormal parent distributions toward greater symmetry. Estimates using uncensored data are less biased and more accurate than the log regression mean and median when censoring exceeds about 50 percent, and are not much worse at any fraction censored. For data with many (80 percent) results below the limit of detection, bias may be quite severe. 相似文献
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Precopulatory sexual cannibalism (predation of a potential mate prior to copulation) offers an extreme example of intersexual conflict, a current focus in behavioral ecology. The aggressive-spillover hypothesis, posits that precopulatory sexual cannibalism may be a nonadaptive by-product of a general syndrome of voracity (aggression towards prey) that is expressed in multiple behavioral contexts. In this view, selection favoring high levels of voracity throughout ontogeny spills over to cause sexual cannibalism in adult females even when it is not necessarily beneficial. Using the North American fishing spider, Dolomedes triton, we present the first in depth test of this hypothesis. We found support for three aspects of the spillover hypothesis. First, voracity towards hetero-specific prey results in high feeding rates, large adult size, and increased fecundity. Second, juvenile and adult voracity are positively correlated (i.e., voracity is a consistent trait over ontogeny). Third, voracity towards hetero-specific prey is indeed positively correlated with precopulatory sexual cannibalism. Assays of antipredator behavior further revealed positive correlations between boldness towards predators, voracity and precopulatory sexual cannibalism. Overall, our results support the notion that precopulatory sexual cannibalism in D. triton is part of a behavioral syndrome spanning at least three major contexts: foraging, predator avoidance, and mating. 相似文献
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John Humphreys Richard W. G. Caldow Selwyn McGrorty Andrew D. West Antony C. Jensen 《Marine Biology》2007,151(6):2255-2270
The Manila clam Ruditapes philippinarum was introduced to Poole Harbour (lat 50°N) on the south coast of England in 1988 as a novel species for aquaculture. Contrary
to expectations, this species naturalised. We report on individual growth patterns, recruitment, mortality and production
within this population. On the intertidal mudflats the abundance of clams (>5 mm in length) varied seasonally between 18 and
56 individuals m−2. There appear to be two recruitment events per year and there were 6 year classes in the population. A mid-summer decline
in abundance was partly due to increased mortality but probably also a result of down-shore migration in response to high
water temperatures and the development of anoxic conditions. A winter fishery removes c 75% of clams of fishable size (maximum
shell length ≥40 mm) and c 20% of the annual production. The fishery depresses the maximum age and size attained by the clams
but appears to be sustainable. Clam mortality due to factors other than fishing is highest in late-winter to early spring.
The growth of the clams is intermediate in comparison with many published studies but remarkably good given their intertidal
position. As on the coasts of the Adriatic Sea, where the clam is also non-native, the Manila clam has thrived in a shallow,
eutrophic, lagoon-like system on the English coast. While the Poole Harbour population is currently Europe’s most northerly
reported self-sustaining, naturalised population, given forecasts of increasing air and sea temperatures it might be expected
that this species will eventually spread to more sites around the coasts of Northern Europe with associated economic and ecological
consequences. 相似文献
340.
Greg?A.?SkilleterEmail author Andrew?Olds Neil?R.?Loneragan Yuri?Zharikov 《Marine Biology》2005,147(2):353-365
Penaeid prawns were sampled with a small seine net to test whether catches of postlarvae and juveniles in seagrass were affected by the distance of the seagrass (mainly Zostera capricorni) from mangroves and the density of the seagrass in a subtropical marine embayment. Sampling was replicated on the western and eastern sides of Moreton Bay, Queensland, Australia. Information on catches was combined with broad-scale spatial information on the distribution of habitats to estimate the contribution of four different categories of habitat (proximal dense seagrass, distal dense seagrass, proximal sparse seagrass, distal sparse seagrass) to the overall population of small prawns in these regions of Moreton Bay. The abundance of Penaeus plebejus and Metapenaeus bennettae was significantly and consistently greater in dense seagrass proximal to mangroves than in other types of habitat. Additionally, sparse seagrass close to mangroves supported more of these species than dense seagrass farther away, indicating that the role of spatial arrangement of habitats was more important than the effects of structural complexity alone. In contrast, the abundance of P. esculentus tended to be greatest in sparse seagrass distal from mangroves compared with the other habitats. The scaling up of the results from different seagrass types suggests that proximal seagrass beds on both sides of Moreton Bay provide by far the greatest contribution of juvenile M. bennettae and P. plebejus to the overall populations in the Bay.Communicated by M.S. Johnson, Crawley 相似文献