全文获取类型
收费全文 | 621篇 |
免费 | 4篇 |
国内免费 | 7篇 |
专业分类
安全科学 | 31篇 |
废物处理 | 44篇 |
环保管理 | 77篇 |
综合类 | 89篇 |
基础理论 | 132篇 |
环境理论 | 3篇 |
污染及防治 | 184篇 |
评价与监测 | 40篇 |
社会与环境 | 26篇 |
灾害及防治 | 6篇 |
出版年
2023年 | 8篇 |
2022年 | 10篇 |
2021年 | 20篇 |
2020年 | 17篇 |
2019年 | 14篇 |
2018年 | 17篇 |
2017年 | 26篇 |
2016年 | 29篇 |
2015年 | 23篇 |
2014年 | 39篇 |
2013年 | 45篇 |
2012年 | 43篇 |
2011年 | 49篇 |
2010年 | 33篇 |
2009年 | 40篇 |
2008年 | 43篇 |
2007年 | 38篇 |
2006年 | 30篇 |
2005年 | 18篇 |
2004年 | 24篇 |
2003年 | 8篇 |
2002年 | 15篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有632条查询结果,搜索用时 15 毫秒
581.
582.
Comparison of ordinary and lognormal kriging on skewed data of total cadmium in forest soils of Sweden 总被引:2,自引:0,他引:2
Kishné AS Bringmark E Bringmark L Alriksson A 《Environmental monitoring and assessment》2003,84(3):243-263
Spatial statistical analysis of georeferenced data of total cadmium (TCd) in forest soils of Sweden was assumed to providemore advantageous maps than traditional interpolated maps. However, 264 measurements of TCd in O-horizon of forest soils displayed skewed frequency distribution. Since atypicalobservations affect badly the variogram, outliers wereidentified, different data transformations were tested andordinary (OK) and lognormal kriging (LK) scenarios werecompared based on cross-validation. Results were comparedusing overall measures of predictors, e.g. traditionalmean squared prediction error (MSPE), mean of krigingvariances, variance ratio, median of internallystandardised residuals, and assessments of classificationaccuracy, such as percentage of correctly predictedsamples and within-class MSPE.One outlier was identified based on the absolute value of skewness of value differences less or equal to one in data pairs separated at certain lag classes. Mapping categories characterised by percentage of correct classification and within-class MSPE were found to be essential in comparison of kriging results additionally to the overall measures. In comparison of kriging methods, OK predicted high values moreaccurately and LK was more effective to predict low and mediumvalues. Thus, OK was suggested for mapping high concentration of TCd and other pollutants. Percentage of correctly predictedsamples and within-class MSPE were found to be dependent on kriging method, as well as on the number and limits of categories. 相似文献
583.
Emo Chiellini Andrea Corti Arianna Giovannini Piero Narducci Anna M. Paparella Roberto Solaro 《Journal of Polymers and the Environment》1996,4(1):37-50
The results of an investigation aimed at evaluation of the biodegradability of blends of poly(-caprolactone) (PCL) with poly(ethylene terephthalate) (PET) as the major component are reported. Specimens of the blends, as melt extruded films and/or powders, were submitted to degradation tests under different environmental conditions including full-scale composting, soil burial, bench-scale accelerated aerobic degradation, and exposure to axenic cultures and esterolytic enzymes. Indications have been gained that blending in the melt gives rise to insertion of PCL segments in the PET chain. Copolymers thus attained acted as macromolecular compatibilizers, allowing for a complete miscibility of PCL and PET. The biodegradation detected on the blend samples was, however, well below the values expected from chemical composition and behavior of individual homopolymers under the same environmental conditions. The presence of PET as the major component in PET/PCL blends apparently reduces the propensity of PCL to be degraded, at least in the investigated composition range. The degradation data collected under different environmental conditions indicate that the full-scale composting system is the most efficient among the tested degradation procedures. 相似文献
584.
/ Sociologist Robert Bullard challenged the prevailing paradigm of environmentalism as a consensual issue in the United States by developing the concept of environmental racism. As he claims, ethnic minorities have been put "at greater environmental risk" than has the Caucasian majority in most areas of the country. This study of the Tucson metropolitan area examines this proposition by utilizing data from several sources: interviews with elected officials and other opinion leaders, GIS-generated socioeconomic data, articles in the press, and a literature review. We conclude that Bullard's concept has validity for this metropolitan area but that there also exist widely divergent differences of opinion on the subject. We explain why this is so. We further conclude that the allegation of "environmental racism" made by the Hispanic community in the 1980s and 1990s has had a transformative effect on local politics.KEY WORDS: Environment; Racism; Tucson; Garbage dumps; County government; Pollution; Equity; Justice 相似文献
585.
Nancy C. Rose M.D. Jacob A. Canick George J. Knight Andrea Pulkkinen M. B. Tumber Michael T. Mennuti Glenn E. Palomaki 《黑龙江环境通报》1994,14(10):947-951
Both a cross-sectional and a longitudinal study were performed to investigate whether or not the collection time should be taken into consideration when generating a patient's risk for fetal Down syndrome with multiple marker screening. Diurnal variations of third-trimester alpha-fetoprotein (AFP) levels and first-trimester human chorionic gonadotropin (hCG) levels have been previously reported. In addition, large episodic fluctuations of conjugated and unconjugated oestriol (uE3) as well as a diurnal variation have also been reported in the third trimester. If the levels of these analytes routinely fluctuate during the day, they could affect a patient's risk calculation for fetal Down syndrome. The longitudinal study evaluated ten non-diabetic women who underwent sequential sampling for AFP, hCG, and uE3. The cross-sectional study evaluated 1953 patients for these three markers whose time of sampling was recorded between 8·00 a.m. and 5·59 p.m. Using either study design, no significant effect was seen in the median MOM levels of the screening analytes as a function of the time of day. 相似文献
586.
The currently discussed model of magnetoreception in birds proposes that the direction of the magnetic field is perceived by radical-pair processes in specialized photoreceptors, with cryptochromes suggested as potential candidate molecules mediating magnetic compass information. Behavioral studies have shown that magnetic compass orientation takes place in the eye and requires light from the blue-green part of the spectrum. Cryptochromes are known to absorb in the same spectral range. Because of this we searched for cryptochrome (CRY) in the retina of European robins, Erithacus rubecula, passerine birds that migrate at night. Here, we report three individually expressed cryptochromes, eCRY1a, eCRY1b, and eCRY2. While eCRY1a and eCRY2 are similar to the cryptochromes found in the retina of the domestic chicken, eCRY1b has a unique carboxy (C)-terminal. In light of the radical-pair model, our findings support a potential role of cryptochromes as transducers for the perception of magnetic compass information in birds. 相似文献
587.
We examined patterns of concurrent multiple mating in a live-bearing poeciliid fish, the sailfin molly (Poecilia latipinna). We tested whether the probability of multiple paternity was related to female body size or fertility and whether the rate
of multiple paternity varied among four populations that differed in their distributions of female body size and fertility.
We analyzed data on mother and offspring genotypes for three polymorphic allozymes by three techniques, including a maximum-likelihood
estimator that accounts for sampling error in both parental and offspring allele frequencies. The estimated rate of multiple
paternity varied between 0.09 and 0.85, and the rate in one population varied seasonally between 0.33 (spring) and 0.85 (autumn).
The variation in these rates was not associated with variation in body-size distributions among populations but was closely
associated with variation in size-specific fertility: populations with greater variation in female fertility had higher multiple-paternity
rates. Within two populations, logistic regression revealed that individual females of larger body size and greater size-specific
fertility were more likely to carry multiply sired broods. This result is consistent with observations made in one of the
populations 5 years earlier. In general, the results strongly suggest that the mating system varies markedly among conspecific
populations of sailfin mollies and that larger, more fertile females are the objects of intermale competition.
Received: 6 May 1996 / Accepted in revised form: 5 December 1996 相似文献
588.
Oviposition behavior of insects has associated fitness costs related to the probability that females survive to oviposit.
During summer 2003, we observed the oviposition behavior and compared the mortality rates of females of 17 mayfly species
in one western Colorado watershed. We dissected adult females collected on terrestrial sticky traps, in drift nets submerged
in streams, and in stomachs of brook trout to determine whether the mayflies had oviposited before capture, drowning, or consumption.
Females oviposited by either splashing on the water surface releasing all their eggs (splashers), dropping their eggs from
the air (bombers), dipping their abdomens multiple times releasing a few eggs at a time (dippers), landing on rocks and ovipositing
on the undersides (landers), or floating downstream while releasing their eggs (floaters). Almost 100% of lander and 50% of
dipper females had not oviposited when captured on sticky traps, increasing their vulnerability to preoviposition mortality
by aerial predators compared to mayflies with other behaviors. In contrast, most females had laid their eggs before drowning
or being eaten by a fish (50–90%). However, groups with oviposition behaviors most exposed to the water surface (floaters,
then splashers, dippers, and landers) were more vulnerable to drowning before completing oviposition. In addition, splashers
and floaters were most vulnerable to predation by brook trout before ovipositing. These data suggest that fitness costs associated
with preoviposition mortality may be considerable depending on mayfly oviposition behavior. Furthermore, previously demonstrated
benefits of low predation rates on eggs of lander species may be offset in part by costs to female survival.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
589.
Jonathan P. Evans Jennifer L. Kelley Indar W. Ramnarine Andrea Pilastro 《Behavioral ecology and sociobiology》2002,52(6):496-502
Previous work has shown that under elevated predation risk, male guppies (Poecilia reticulata) switch from courtship to less conspicuous coercive mating attempts. This behavioural transition is traditionally interpreted as a 'risk-sensitive' response that makes males less conspicuous to predators. However, predation risk leads to behavioural changes (such as schooling and predator inspection) in females that may result in coercive mating attempts being more profitable in high-risk situations. Here, we tested the hypothesis that the switch to coercive mating by male guppies in high-risk situations is mediated by adjustments in female behaviour, rather than directly by the predator. We used replicate models resembling a known guppy predator to simulate predation risk in wild-caught guppies from a high-predation population in Trinidad. Our results revealed that males performed proportionately more coercive mating attempts when presented with a female that had been exposed previously to a model predator compared to when males were paired with non-exposed females. Total mating activity (combined rates of courtship and forced mating attempts) did not differ significantly among the two treatment groups, indicating that overall mating activity is unaffected by predation risk. Importantly, when we subsequently presented both sexes concurrently with a predator model, total mating activity and the proportion of forced mating attempts remained unchanged in the high-risk treatment. Taken together, these results indicate that the transition from courtship to forced mating attempts under elevated predation risk is mediated by changes in female behaviour, which we suggest may favour the use of coercive mating under high predation risk. 相似文献
590.
Andrea Gori Cristina Linares Sergio Rossi Rafel Coma Josep-Maria Gili 《Marine Biology》2007,151(4):1571-1584
Paramuricea clavata (Risso, 1826) and Eunicella singularis (Esper, 1794) are the most representative gorgonian species in hard bottoms sublittoral communities in the Western Mediterranean
Sea. Reproductive cycles of two populations of both species were studied in two distinct locations approximately 600 km apart
(Medes Islands and Cape of Palos), in order to assess interpopulation variability on a relevant geographic scale. Seasonal
variation of lipid concentration levels in the gorgonian tissue was used as a tool to quantify energy storage by each studied
population in order to explain possible interpopulation differences in gonadal output. Sex ratio in Medes Islands populations
of both species was 1:1, while in Cape of Palos sex ratio was significantly male biased (1:7) in P. clavata, and female biased (1.7:1) in E. singularis populations. Spawning timing occurred in all cases coinciding with a marked increase in sea-water temperature in spring,
and after the most successful feeding season, but comparing localities there was a clear temporal shift in the time of gametes
release, appearing well linked to the shift in sea-water temperature rising in spring in both sites at the depth where populations
are placed. Therefore, in this study the temperature appears as the main synchronizing factor of gonadal development within
these populations. Significant differences in gonadal volume per polyp were found in both species owing mainly to differences
in the number of gonads per polyp between populations, with Cape of Palos populations displaying higher values in both studied
species, suggesting that the exposition to different local conditions may be reverted in a different gonadal output. But the
observed patterns in lipid concentrations levels in gorgonians disable us to conclude that lipid concentration levels explain
the observed differences in gonadal output found in this study. 相似文献