全文获取类型
收费全文 | 245篇 |
免费 | 0篇 |
专业分类
安全科学 | 5篇 |
废物处理 | 3篇 |
环保管理 | 6篇 |
综合类 | 150篇 |
基础理论 | 22篇 |
污染及防治 | 49篇 |
评价与监测 | 6篇 |
社会与环境 | 4篇 |
出版年
2014年 | 3篇 |
2013年 | 10篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 12篇 |
2006年 | 6篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1984年 | 2篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1976年 | 2篇 |
1969年 | 3篇 |
1966年 | 7篇 |
1965年 | 3篇 |
1964年 | 8篇 |
1963年 | 8篇 |
1962年 | 4篇 |
1961年 | 9篇 |
1960年 | 3篇 |
1959年 | 3篇 |
1958年 | 6篇 |
1957年 | 6篇 |
1956年 | 9篇 |
1955年 | 4篇 |
1954年 | 7篇 |
1953年 | 6篇 |
1952年 | 4篇 |
1951年 | 3篇 |
1950年 | 2篇 |
1947年 | 3篇 |
1941年 | 2篇 |
1939年 | 2篇 |
1932年 | 2篇 |
1931年 | 3篇 |
1930年 | 2篇 |
1926年 | 2篇 |
1922年 | 2篇 |
1917年 | 2篇 |
1914年 | 4篇 |
1913年 | 3篇 |
排序方式: 共有245条查询结果,搜索用时 0 毫秒
161.
162.
Summary Harsh physico-chemical conditions during early development may select for parental care. However, no study on the evolution of parental care has focused on the physico-chemical conditions in the environment, the physiological needs of early life stages and the significance of parental care. Early development of the bromeliad crab is completed in small rainwater reservoirs in bromeliad leaf axils. Axils not cared for by mother crabs are acidic, hypoxic and contain very little Ca2+. Maternal care buffers axil water and increases oxygen and Ca2+ availability. Our results show that (a) bromeliad crab larvae die at pH levels usually found in unattended axils, but develop successfully into the first crab stage at the pH typical of cared-for axils; (b) oxygen concentration in unattended axils is below the critical concentration for larvae, but is high enough for normal respiration in cared-for axils; (c) the calcium demand of larvae for moulting and development cannot be satisfied in unattended axils, but is met by the higher calcium content of cared-for axils. Therefore, physicochemical conditions in the bromeliad axil habitat exert strong selection for the maintenance of parental care in the bromeliad crab.
Correspondence to: R. Diesel 相似文献
163.
Recent monitoring investigations have shown that antimicrobial agents used in veterinary medicine can cause non-point source contamination of soils through manure spreading. In the present study, the effect of the antimicrobial agent sulfamethazine (sulfadimidine) on degradation and sorption of the herbicide metolachlor in a sandy loam soil was studied. In soil samples treated with sulfamethazine at two concentrations (15 and 150 microg kg(-1) soil), metolachlor persistence was not different than of that observed in untreated samples. These results were supported by the absence of effects of both sulfamethazine concentration levels on the size of the culturable soil bacteria population. Equilibrating soil samples with metolachlor solutions containing equivalent sulfamethazine concentrations did not lead to any significant effects on metolachlor sorption, suggesting that, under the conditions of the present experiment, sulfamethazine did not affect metolachlor bioavailability in soil. This laboratory investigation showed that concentrations of sulfamethazine in the microg kg(-1) range did not cause significant effects on metolachlor degradation and sorption thus not affecting the main processes ruling its environmental fate in soil. 相似文献
164.
Industrial tree plantations in the tropics usually follow short rotations and intensive site management including slash and burn, and the use of heavy machinery. We attempt to quantify the implied nutrient losses (harvest export, erosion, slash and burn, leaching) in order to give plantation managers a chance to understand the significance of their planning and decisions. We used the scarce globally available information and a case study plantation in East Kalimantan, Indonesia (Acacia mangium and Eucalyptus deglupta). Adaptation involves problems and is discussed in some detail. Results are approximate only. Assuming a harvest volume of 200 m3 ha(-1), we assessed a loss of 427-680 kg ha(-1) N, 12-13 kg ha(-1) P, 178-252 kg ha(-1) Ca, 276-370 kg ha(-1) K, and 45-57 kg ha(-1) Mg per rotation. Of this overall loss, stand harvest accounted for 18-29% (N), 21-30% (P), 56-26% (K), 48-64% (Ca) and 22-37% (Mg). This means that the cumulative loss by erosion, slash and burn, and leaching exceeds that of the harvest. These losses can be influenced by management. 相似文献
165.
Consequences of stage-structured predators: cannibalism, behavioral effects, and trophic cascades 总被引:3,自引:0,他引:3
Cannibalistic and asymmetrical behavioral interactions between stages are common within stage-structured predator populations. Such direct interactions between predator stages can result in density- and trait-mediated indirect interactions between a predator and its prey. A set of structured predator-prey models is used to explore how such indirect interactions affect the dynamics and structure of communities. Analyses of the separate and combined effects of stage-structured cannibalism and behavior-mediated avoidance of cannibals under different ecological scenarios show that both cannibalism and behavioral avoidance of cannibalism can result in short- and long-term positive indirect connections between predator stages and the prey, including "apparent mutualism." These positive interactions alter the strength of trophic cascades such that the system's dynamics are determined by the interaction between bottom-up and top-down effects. Contrary to the expectation of simpler models, enrichment increases both predator and prey abundance in systems with cannibalism or behavioral avoidance of cannibalism. The effect of behavioral avoidance of cannibalism, however, depends on how strongly it affects the maturation rate of the predator. Behavioral interactions between predator stages reduce the short-term positive effect of cannibalism on the prey density, but can enhance its positive long-term effects. Both interaction types reduce the destabilizing effect of enrichment. These results suggest that inconsistencies between data and simple models can be resolved by accounting for stage-structured interactions within and among species. 相似文献
166.
Carbamazepine (CBZ), caffeine and cetirizine were monitored by enzyme-linked immunosorbent assays (ELISAs) in surface and wastewaters from Berlin, Germany. This fast and cost-efficient method enabled to assess the spatial and temporal variation of these anthropogenic markers in a high-throughput screening. CBZ and cetirizine were detected by the same antibody, which selectively discriminates between both compounds depending on the pH value used in the incubation step. To our best knowledge, this is the first dual-analyte immunoassay working with a single antibody.The frequent sampling with 487 samples being processed allowed for the repeated detection of unusually high concentrations of CBZ and caffeine. ELISA results correlate well with the ones obtained by liquid chromatography tandem mass spectrometry (LC-MS/MS). Caffeine concentrations found in surface waters were elevated by combined sewer overflows after stormwater events. During the hay fever season, the concentrations of the antihistamine drug cetirizine increased in both surface and wastewaters.Caffeine was almost completely removed during wastewater treatment, while CBZ and cetirizine were found to be more persistent. The maximum concentrations of caffeine, CBZ and cetirizine found in influent wastewater by LC-MS/MS were 470, 5.0 and 0.49 μg L−1, while in effluent wastewater the concentrations were 0.22, 4.5 and 0.51 μg L−1, respectively. For surface waters, concentrations up to 3.3, 4.5 and 0.72 μg L−1 were found, respectively. 相似文献
167.
Organic aerosols in the Miami area, USA: temporal variability of atmospheric particles and wet/dry deposition 总被引:1,自引:0,他引:1
Atmospheric particulate matter and both wet and dry deposition was collected over a period of nine months at one location in the metropolitan area of Miami, Florida. Molecular distributions and concentrations of n-alkanes, fatty acids, polycyclic aromatic hydrocarbons (PAHs) and hopanes were determined using weekly composite samples over this time period in order to determine temporal variability, and their possible dependence on climatic parameters such as temperature, rainfall and wind direction and frequency. Based on molecular distributions of the compounds studied, potential emission sources for the atmospheric particles were assessed and suggested to be mainly derived from automobile exhaust and natural sources. Although wet and dry deposition processes were observed to remove about equal amounts of organic aerosols from the Miami atmosphere, dry deposition was dominant in the removal of anthropogenically derived compounds such as PAHs and hopanes. Only very limited seasonal trends were observed, while wind direction and frequency was found to be the most important meteorological parameter controlling the temporal variability of the organic aerosols. This is the first detailed report of this nature for the Miami area. 相似文献
168.
169.
170.