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211.
Wu TH Cañas JE Rainwater TR Platt SG McMurry ST Anderson TA 《Environmental pollution (Barking, Essex : 1987)》2006,144(1):151-157
Seven complete clutches of Morelet's crocodile (Crocodylus moreletii) eggs were collected in northern Belize and examined for organochlorine (OC) pesticide residues. The primary OC detected, p,p-DDE, was found in every egg analyzed (n=175). Other OCs detected included p,p-DDT, p,p-DDD, methoxychlor, aldrin, and endosulfan I. Concentrations of individual OCs ranged from 4 ppb (ng chemical/g egg wet weight) to greater than 500 ppb. A statistical evaluation of p,p-DDE levels in three complete clutches was used to derive the minimum number of eggs needed from a clutch to precisely determine the mean p,p-DDE concentration representative of that clutch. Sample sizes of 8 (80% confidence level) and 11 (90% confidence level) were determined to yield an accurate estimate of contaminant levels in a full clutch of eggs. The statistically recommended sample size of 11 eggs (at 90% confidence level) was successfully tested on the four additional clutches. 相似文献
212.
In safety assessments of nuclear facilities, a wide range of radioactive isotopes and their potential hazard to a large assortment of organisms and ecosystem types over long time scales need to be considered. Models used for these purposes have typically employed approaches based on generic reference organisms, stylised environments and transfer functions for biological uptake exclusively based on bioconcentration factors (BCFs). These models are of non-mechanistic nature and involve no understanding of uptake and transport processes in the environment, which is a severe limitation when assessing real ecosystems. In this paper, ecosystem models are suggested as a method to include site-specific data and to facilitate the modelling of dynamic systems. An aquatic ecosystem model for the environmental transport of radionuclides is presented and discussed. With this model, driven and constrained by site-specific carbon dynamics and three radionuclide specific mechanisms: (i) radionuclide uptake by plants, (ii) excretion by animals, and (iii) adsorption to organic surfaces, it was possible to estimate the radionuclide concentrations in all components of the modelled ecosystem with only two radionuclide specific input parameters (BCF for plants and Kd). The importance of radionuclide specific mechanisms for the exposure to organisms was examined, and probabilistic and sensitivity analyses to assess the uncertainties related to ecosystem input parameters were performed. Verification of the model suggests that this model produces analogous results to empirically derived data for more than 20 different radionuclides. 相似文献
213.
Venkatesan G. Subramani T. Karunanidhi D. Sathya U. Li Peiyue 《Environmental science and pollution research international》2021,28(15):18552-18552
Environmental Science and Pollution Research - A Correction to this paper has been published: https://doi.org/10.1007/s11356-021-13406-7 相似文献
214.
Venkatesan G. Subramani T. Karunanidhi D. Sathya U. Li Peiyue 《Environmental science and pollution research international》2021,28(15):18539-18551
Environmental Science and Pollution Research - In the present study, impact of precipitation disparity on groundwater level fluctuation was carried out in Vellore district, Tamil Nadu, India, using... 相似文献
215.
216.
Conservation Genetics of the Endangered Isle Royale Gray Wolf 总被引:5,自引:0,他引:5
R. K. WAYNE N. LEHMAN D. GIRMAN P.J.P. GOGAN D. A. GILBERT K. HANSEN R. O. PETERSON U. S. SEAL A. EISENHAWER L. D. MECH R.J. KRUMENAKER 《Conservation biology》1991,5(1):41-51
Abstract. The small group of wolves on Isle Royale has been studied for over three decades as a model of the relationship between large carnivores and their prey. During the last ten years the population declined from 50 individuals to as few as 12 individuals. The causes of this decline may be food shortages, disease, or reduced genetic variability. We address the issues of genetic variability and relationships of Isle Royale wolves using allozyme electrophoresis, mtDNA restriction-site analysis, and multilocus hypervariable minisatellite DNA analysis (genetic fingerprinting). Our results indicate that approximately 50% of the allozyme heterozygosity has been lost in the island population, a decline similar to that expected if no immigration had occurred from the mainland. The genetic fingerprinting data indicate that the seven sampled Isle Royale wolves are as similar as captive populations of siblings. Surprisingly, the Isle Royale wolves have an mDNA genotype that is very rare on the mainland, being found in only one of 144 mainland wolves ThFF suggests that the remaining Isle Royale wolves areprobably derived from a single female founder 相似文献
217.
Hydrolytic enzyme activities were determined in tissue extracts of the two North Sea ctenophores Pleurobrachia pileus and Beroe gracilis. The following activities were measured in field samples and characterized according to their mean specific activities and their pH optima: protease, aminopeptidase, amylase, N-acetylglucosaminidase, -glucosidase, chitinase, carboxylesterase, phosphatase. Many of the enzyme activities are correlated, indicating their control by the same factors (i.e. nutritional conditions). Differences found between the phosphatase activities and the apparent lack of the chitinolytic system in B. gracilis reflect the differences in body composition and food specialization in both ctenophores, respectively. The low amylase and -glucosidase activities in both ctenophores agree with the low carbohydrate content of their prey. In spite of high carboxylesterase activities, no lipolytic activity was detected in either of the ctenophores. In a laboratory feeding experiment with P. pileus, the enzyme activities increased but did not reach the activities found in the field samples. In B. gracilis, seasonal variations of some enzyme activities are discussed in relation to the seasonal abundance of its prey, P. pileus. 相似文献
218.
Change in a bacterial population during the process of degradation of a phytoplankton bloom was investigated at Lake Hamana, Japan in June 1981. The predominant phytoplankton were Prorocentrum micans Ehrenberg and P. triestinum Schiller. While most phytoplankton cells were living and moving actively, most bacteria were those in a free-living state (free-living bacteria) and the number of bacteria associated with particulate materials (attached bacteria) was less than a few percent of the total bacterial number. As the decline process proceeded, the number of free-living bacteria remained almost constant or decreased slightly; on the other hand, the number of attached bacteria increased gradually and reached about 40% of the total bacterial number. These results indicate that some of the free-living bacteria become attached to particulate organic matter and grow on the surface of the particles. 相似文献
219.
The evaporation of organic contaminants of different volatility from a porous sandfill was investigated in laboratory experiments. A significant decrease of the evaporation rate was observed under conditions of compacted fill, at high concentrations of the low-volatile component. This can be explained by the formation of a layer with a low mass fraction of the solvent near the gas-phase boundary of the contaminated zone. The term ?self-encapsulation” is suggested for this phenomenon. Theoretical considerations show that this effect can occur if a volatile component evaporates from a mixture with a substance of low volatility and if the total mass transfer resistance is mainly within the contaminant phase. The formation of a solid layer at the surface can enhance this encapsulating effect for the remaining volatile material. A similar behaviour can be expected for contaminants consisting of components of different solubility which get in contact with flowing water. 相似文献
220.