全文获取类型
收费全文 | 230篇 |
免费 | 5篇 |
国内免费 | 4篇 |
专业分类
安全科学 | 11篇 |
废物处理 | 6篇 |
环保管理 | 21篇 |
综合类 | 44篇 |
基础理论 | 109篇 |
污染及防治 | 34篇 |
评价与监测 | 5篇 |
社会与环境 | 9篇 |
出版年
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 12篇 |
2015年 | 5篇 |
2014年 | 11篇 |
2013年 | 15篇 |
2012年 | 12篇 |
2011年 | 14篇 |
2010年 | 18篇 |
2009年 | 10篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 30篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 4篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 1篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1958年 | 1篇 |
1938年 | 1篇 |
1937年 | 1篇 |
1932年 | 1篇 |
1926年 | 1篇 |
1924年 | 1篇 |
排序方式: 共有239条查询结果,搜索用时 15 毫秒
231.
Maternal investment, sex-differential prospects, and the sex ratio in wild house mice 总被引:2,自引:0,他引:2
Sven Krackow 《Behavioral ecology and sociobiology》1997,41(6):435-443
In a population of first-generation offspring from wild-caught house mice (Mus musculus domesticus), previous evidence suggested that male fitness is more strongly affected by an increase in body weight than female fitness.
This paper shows that in these mice the young are weaned at heavier weights the smaller the litter and the better the maternal
body condition. These effects persisted into adulthood and were less pronounced in female young. However, contrary to expectation
from conventional sex ratio theory, maternal condition and litter size had no detectable effect on sex ratios. Also, litter
size did not affect sex ratios in two populations of laboratory-kept, wild-caught western (M. m. domesticus) and eastern house mice (M. m. musculus). Wild house mice, therefore, appear not to adaptively manipulate the sex ratio of offspring. It is argued that this absence
of sex ratio trends might not be maladaptive, but rather that models currently used to predict sex ratio trends in rodents
may not be valid.
Received: 13 March 1997 / Accepted after revision: 9 August 1997 相似文献
232.
Ammonia (NH3) emission from livestock production causes undesirable environmental effects and a loss of plant-available nitrogen. Much atmospheric NH3 is lost from livestock manure applied in the field. The NH3 emission may be reduced by slurry injection, but slurry injection in general, and especially on grassland, increases the energy demand and places heavy demands on the slurry injection techniques used. The reduction in NH3 emission, injection efficiency, and energy demand of six different shallow slurry-injection techniques was examined. The NH3 emission from cattle slurry applied to grassland was reduced by all the injectors tested in the study, but there were major differences in the NH3 reduction potential of the different types of injectors. Compared with the trailing hose spreading technique, the NH3 loss was reduced by 75% when cattle slurry was injected using the most efficient slurry injection technique, and by 20% when incorporated by the least efficient injection technique. The reduction in NH3 emission was correlated with injection depth and the volume of the slot created. The additional energy demand for reducing ammonia emissions by slurry injection was approximately 13 000 kJ ha(-1) for a 20% reduction and 34 000 kJ ha(-1) for a 75% reduction. The additional energy demand corresponds to additional emissions of, respectively, 5.6 and 14.5 kg CO2 per ha injected. 相似文献
233.
The Science of Nature - 相似文献
234.
235.
236.
237.
The importance of preserving both protected areas and their surrounding landscapes as one of the major conservation strategies
for tigers has received attention over recent decades. However, the mechanism of how land-use surrounding protected areas
affects the dynamics of tiger populations is poorly understood. We developed Panthera Population Persistence (PPP)—an individual-based
model—to investigate the potential mechanism of the Sumatran tiger population dynamics in a protected area and under different
land-use scenarios surrounding the reserve. We tested three main landscape compositions (single, combined and real land-uses
of Tesso-Nilo National Park and its surrounding area) on the probability of and time to extinction of the Sumatran tiger over
20 years in Central Sumatra. The model successfully explains the mechanisms behind the population response of tigers under
different habitat landscape compositions. Feeding and mating behaviours of tigers are key factors, which determined population
persistence in a heterogeneous landscape. All single land-use scenarios resulted in tiger extinction but had a different probability
of extinction within 20 years. If tropical forest was combined with other land-use types, the probability of extinction was
smaller. The presence of agroforesty and logging concessions adjacent to protected areas encouraged the survival of tiger
populations. However, with the real land-use scenario of Tesso-Nilo National Park, tigers could not survive for more than
10 years. Promoting the practice of agroforestry systems surrounding the park is probably the most reasonable way to steer
land-use surrounding the Tesso-Nilo National Park to support tiger conservation. 相似文献
238.
The oxyfuel process is one of the most promising options to capture CO2 from coal fired power plants. The combustion takes place in an atmosphere of almost pure oxygen, delivered from an air separation unit (ASU), and recirculated flue gas. This provides a flue gas containing 80–90 vol% CO2 on a dry basis. Impurities are caused by the purity of the oxygen from the ASU, the combustion process and air ingress. Via liquefaction a CO2 stream with purity in the range from 85 to 99.5 vol% can be separated and stored geologically. Impurities like O2, NOX, SOX, and CO may negatively influence the transport infrastructure or the geological storage site by causing geochemical reactions. Therefore the maximum acceptable concentrations of the impurities in the separated CO2 stream must be defined regarding the requirements from transportation and storage. The main objective of the research project COORAL therefore is to define the required CO2 purity for capture and storage. 相似文献
239.
This paper compares the capability of a first-order and a spherical diffusion model to describe and predict long-term sorption and desorption processes of chlortoluron in two soils. Chlortoluron sorption was investigated at different time scales utilizing one rate experiment (120 days) and two sorption/desorption experiments. Experimental periods for sorption and desorption were set to 1 day (five desorption steps) and 30 days (three desorption steps), respectively. Upon fitting, the two models satisfactorily described the whole set of data. The spherical diffusion model performed better than the first-order model. We then tested the predictive capability of the models by predicting 30-day sorption/desorption data using kinetic parameters fitted on 1-day sorption/desorption data only. While the spherical diffusion model was able to predict the 30-day data set, the first-order model failed completely. Fitting both models to subsets of the data corresponding to different experimental time scales revealed that the rate parameter as well as the Freundlich coefficient of the first-order model are strongly time-dependent--a property that is not shared by parameters of the spherical diffusion model. The apparent stability of the spherical diffusion model with regard to time dependency of its parameters indicates that sorptive uptake may be diffusion-controlled. This also explains the models greater predictive power across different time scales compared to the first-order model. Finally, we investigate the suitability of solute class specific log-linear relationships between the first-order rate parameter and the Freundlich coefficient presented by earlier researchers in the light of the time dependency observed for the parameters of the first-order model. 相似文献