全文获取类型
收费全文 | 341篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
安全科学 | 7篇 |
废物处理 | 6篇 |
环保管理 | 22篇 |
综合类 | 196篇 |
基础理论 | 52篇 |
污染及防治 | 46篇 |
评价与监测 | 9篇 |
社会与环境 | 4篇 |
灾害及防治 | 4篇 |
出版年
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 7篇 |
2014年 | 5篇 |
2013年 | 7篇 |
2012年 | 6篇 |
2011年 | 9篇 |
2010年 | 8篇 |
2009年 | 8篇 |
2008年 | 4篇 |
2007年 | 16篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 9篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 10篇 |
2000年 | 4篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1981年 | 5篇 |
1979年 | 4篇 |
1967年 | 8篇 |
1965年 | 5篇 |
1964年 | 6篇 |
1963年 | 8篇 |
1962年 | 4篇 |
1961年 | 3篇 |
1960年 | 4篇 |
1959年 | 7篇 |
1958年 | 4篇 |
1957年 | 3篇 |
1955年 | 7篇 |
1954年 | 4篇 |
1942年 | 4篇 |
1940年 | 3篇 |
1939年 | 3篇 |
1934年 | 9篇 |
1932年 | 4篇 |
1931年 | 4篇 |
1929年 | 5篇 |
1928年 | 5篇 |
1926年 | 3篇 |
1921年 | 4篇 |
1918年 | 4篇 |
1915年 | 3篇 |
1913年 | 8篇 |
排序方式: 共有346条查询结果,搜索用时 640 毫秒
31.
32.
33.
34.
Influence of turbulence on the activity of bacterial slimes 总被引:1,自引:0,他引:1
L Hartmann 《Journal - Water Pollution Control Federation》1967,39(6):958-964
35.
36.
Cicada emergence in Southwestern riparian forest: influences of wildfire and vegetation composition.
Annually emerging cicadas are a numerically and ecologically dominant species in Southwestern riparian forests. Humans have altered disturbance regimes that structure these forests such that floods are less common and wildfires occur more frequently than was historically the case. Impacts of these changes on primary consumers such as riparian cicadas are unknown. Because cicadas are consumed by a variety of animal species, disturbances that alter timing of their emergence or abundance could have consequences for species at higher trophic levels. We trapped emerging cicadas (Tibicen dealbatus) in burned and unburned riparian forest plots along the Middle Rio Grande in central New Mexico (USA) to determine effects of wildfire and vegetation structure on their density and phenology. We measured vegetation variables and soil temperature at cicada traps and related these variables to variation in emergence density and phenology. We also experimentally heated soil under emergence traps to examine the relationship between soil temperature and emergence phenology. Emergence density was similar in wildfire and unburned plots, though emergence date averaged earlier in wildfire plots and experimentally heated traps. We identified models containing cottonwood proximity (distance from the nearest cottonwood tree) and cottonwood canopy coverage as the most parsimonious explanations of emergence density at each trap. Model selection results were consistent with the literature and field observations that showed that cottonwood trees are an essential resource for T. dealbatus. Cottonwood canopy was also correlated with low soil temperatures, which are associated with later emergence dates. Failure of cottonwoods to reestablish following wildfire could result in cicadas emerging at lower densities and at earlier dates. For cicadas to emerge at densities and times that provide the greatest benefits to birds and other riparian-obligate secondary consumers, riparian forests should be protected from fire, and native vegetation in wildfire sites should be restored. 相似文献
37.
Summary Life stages of the primitive Australian ithomiine butterflyTellervo zoilus and its larval hostplant, the apocynaceous vineParsonsia straminea, were quantitatively assayed for pyrrolizidine alkaloids (PAs). PAs were found in all stages, mainly as N-oxides, being most concentrated in larvae and freshly-emerged adults. Although adults feed at various confirmed PA sources this probably does not compensate for losses, as wild-caught adults had considerably lower concentrations of PAs. The main alkaloid present in both freshly-emerged adults and in leaves of the host-plant was lycopsamine (1b), stored by butterflies in the N-oxide form. Its presence in higher proportion, in relation to intermedine (1a), in larvae, pupae and adults ofTellervo in relation to the host-plants suggests the inversion of intermedine to lycopsamine by the insects. No 14-member ring macrocyclic PAs were detected in either food-plant or butterflies. Several other PAs were found in wild-caught adults reflecting visits to other PA sources. PAs were also found in high concentrations in freshly-emerged individuals of the danaineEuploea core bred onParsonsia straminea. Wild-caughtDanaus affinis had high PA levels acquired from adult feeding. Freshly emergedEuploea raised onIschnocarpus frutescens andDanaus raised onIschnostemma carnosum (both PA-free) were preyed on by the orb weaving spiderNephila maculata, and showed no PAs. In all cases where PAs were present, most butterflies were liberated, usually cut out of the web unharmed, byNephila. The spider's response was not closely linked to PA concentration, however, and may also depend on hunger levels and previous experience with PA-containing butterflies. All control and other non-PA containing butterflies were consumed although rejection of some body parts of freshly-emergedDanaus affinis suggests that compounds other than PAs may be involved. 相似文献
38.
Ingo?NarberhausEmail author Claudine?Theuring Thomas?Hartmann Susanne?Dobler 《Chemoecology》2004,14(1):17-23
Summary. Several species of Longitarsus take up, metabolize and
store pyrrolizidine alkaloids (PAs) from their host plants. In feeding experiments using
radioactively labeled PAs of different types we examined the time course of the sequestration
process in L. jacobaeae and
L. aeruginosus. We found that adapted species efficiently
store PAs for at least two weeks without major losses. During that time, there is virtually
no change in the ratio of tertiary alkaloids to stored non-toxic
N-oxides, regardless of chemical form fed to the beetles. This
implies a transient N-oxidation process where the alkaloids are
only temporarily accessible to the enzyme. A dissection experiment with
L. aeruginosus six days after uptake of labeled PAs
showed that the tertiary alkaloids are not found in the hemolymph but are stored in the
elytra and other body compartments. This conforms with earlier experiments that localized the
enzymes site of action in the hemolymph. Furthermore we show that different total alkaloid
doses in the diet of L. jacobaeae and the potentially less
adapted L. succineus do not affect the ratio of recovered
N-oxides to tertiary molecules. Thus, the efficiency of the
N-oxidizing enzyme is not dependent on the concentration of
alkaloids offered. 相似文献
39.
Karlsson PE Pleijel H Belhaj M Danielsson H Dahlin B Andersson M Hansson M Munthe J Grennfelt P 《Ambio》2005,34(1):32-40
Ground level ozone concentrations, in combination with the prevailing climate, at the estate Ostads S?teri in southwestern Sweden were estimated to reduce the yield of wheat and potato ranging between 5% and 10%. Occasionally, in years with the highest ozone concentrations and/or climatic conditions favoring high rates of ozone uptake to the leaves, yield loss levels above 10% may occur. Based on simple extrapolation, these ozone-induced reductions of crop yields at Ostads S?teri represent a potential total annual yield loss in Sweden in the range of 24.5 million Euro for wheat and 7.3 million Euro for potato, respectively. A simulation of forest growth at Ostad S?teri predicted that prevailing mean ozone exposure during 1993-2003 had the potential to reduce forest growth by 2.2% and the economic return of forest production by 2.6%. Using this value for extrapolation to the national level, the potential annual economic loss for Sweden due to negative impacts of ozone on forest production would be in the range of 56 million Euro (2004 prices). 相似文献
40.
Rainer Brüggemann Andreas Kaune Laszlo Zelles Anton Hartmann Christian Steinberg 《Umweltwissenschaften und Schadstoff-Forschung》1995,7(5):265-274
Die ?kotoxikologie mu? sich mit biologischen Systemen und ihren Antworten auf schadstoffinduzierten Stre? auseinandersetzen.
Die hierzu verwendete experimentelle Technik eilt dabei den M?glichkeiten dynamischer, proze?orientierter mathematischer Modellierung
weit voraus.
In dieser methodisch orientierten Arbeit werden Techniken aus der mathematischen Disziplin der Verbandstheorie vorgestellt,
die eine Datenanalyse unter den Aspekten vergleichender Bewertung erlauben. Wichtige Ergebnisse sind dabei
相似文献
– | • Aussagen zur Diversit?t mikrobieller Systeme (soweit durch die hier verwendeten Muster von vier Phospholipidfetts?uren erfa?bar), |
– | • Analysen ordinaler Abh?ngigkeiten sowie |
– | • komprimierte Darstellung komplexer Befunde im Zusammenhang mit der Toxizit?t von Huminstoff-Chemikalien-Systemen. |