全文获取类型
收费全文 | 1389篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 25篇 |
废物处理 | 19篇 |
环保管理 | 128篇 |
综合类 | 1004篇 |
基础理论 | 93篇 |
污染及防治 | 100篇 |
评价与监测 | 20篇 |
社会与环境 | 6篇 |
灾害及防治 | 3篇 |
出版年
2016年 | 10篇 |
2013年 | 55篇 |
2012年 | 11篇 |
2011年 | 15篇 |
2010年 | 18篇 |
2009年 | 8篇 |
2008年 | 19篇 |
2007年 | 15篇 |
2006年 | 10篇 |
2005年 | 10篇 |
2004年 | 9篇 |
2003年 | 20篇 |
2002年 | 10篇 |
1998年 | 12篇 |
1995年 | 59篇 |
1994年 | 51篇 |
1993年 | 42篇 |
1992年 | 37篇 |
1991年 | 26篇 |
1990年 | 33篇 |
1989年 | 28篇 |
1988年 | 34篇 |
1987年 | 29篇 |
1986年 | 21篇 |
1985年 | 16篇 |
1984年 | 14篇 |
1983年 | 19篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1973年 | 11篇 |
1965年 | 8篇 |
1962年 | 9篇 |
1961年 | 8篇 |
1959年 | 9篇 |
1957年 | 13篇 |
1955年 | 8篇 |
1940年 | 10篇 |
1939年 | 10篇 |
1937年 | 9篇 |
1935年 | 11篇 |
1934年 | 7篇 |
1919年 | 47篇 |
1918年 | 44篇 |
1917年 | 36篇 |
1916年 | 53篇 |
1915年 | 37篇 |
1914年 | 71篇 |
1913年 | 106篇 |
排序方式: 共有1398条查询结果,搜索用时 868 毫秒
921.
922.
923.
924.
Kurt O Reinhart Julie Gurnee Reyes Tirado Ragan M Callaway 《Ecological applications》2006,16(5):1821-1831
The effects of invasive nonnative species on community composition are well documented. However, few studies have determined the mechanisms by which invaders drive these changes. The literature indicates that many nonnative plant species alter light availability differently than natives in a given community, suggesting that shading may be such a mechanism. We compared light quantity (photosynthetically active radiation, PAR) and quality (red: far-red ratio, R:Fr) in riparian reaches heavily invaded by a nonnative tree (Acer platanoides) to that in an uninvaded forest and experimentally tested the effects of our measured differences in PAR and R:Fr on the survival, growth, and biomass allocation of seedlings of the dominant native species and Acer platanoides. Light conditions representative of the understory of Acer platanoides-invaded forest decreased survival of the native maple Acer glabrum by 28%; Amelanchier alnifolia by 32%; Betula occidentalis by 55%; Elymus glaucus by 46%; and Sorbus aucuparia by 52%, relative to seedlings growing in PAR similar to that of native understories. In contrast, Acer platanoides and the native shrub Symphoricarpos albus were not affected by reductions in PAR. Acer platanoides seedlings and saplings are uniquely adapted to shade relative to native species. Acer platanoides was the only species tested that decreased allocation to roots relative to shoots in the invaded forest vs. the native forest light conditions. Therefore it was the only species to demonstrate an adaptive response to the particular light environment associated with Acer platanoides invasion as predicted by optimal partitioning theory. The profound change in light quantity associated with Acer platanoides canopies appears to act as an important driver of native suppression and conspecific success in invaded riparian communities. Further research is necessary to determine whether the effect of nonnative plant-driven changes on light quantity and quality is a widespread mechanism negatively affecting resident species and facilitating invasion by nonnatives. 相似文献
925.
926.
We report on the prenatal diagnosis of congenital myotonic dystrophy in a case of nonimmune hydrops fetalis. DNA analysis of amniocytes revealed expansion of the trinucleotide (CTG) repeat within the myotonin PK gene, associated with myotonic dystrophy. The fetus was found to have approximately 1730 copies, while the normal population has between 5 and 27 copies, and minimally affected individuals have at least 50 copies. 相似文献
927.
928.
929.
Dr A. O. Aweto 《The Environmentalist》1995,15(1):10-15
Summary This paper evaluates the rates of organic carbon diminution in the soil under monospecific tree plantations of teak, gmelina, rubber, oil palm, cashew and coffee. The differences between the organic carbon status of their soils and soil under nearby natural rain forest vegetation are compared. Annual rates of organic carbon decrease for the 0–10 cm soil layer, varied from 82.1 kg ha–1 for cashew to 316.7 kg ha–1 for oil palm. The tree plantations appear to release more carbon dioxide from the soil into the atmosphere than the natural forest. They therefore, appear to have the potential of contributing towards global warming — a threat they are supposed to mitigate. 相似文献
930.
Dr. M. V. Angel 《The Environmentalist》1982,2(1-2):1-17
Considerable concern has been recently expressed in conservation circles about the potential threat to oceanic trench ecosystems.
Here, the geological origin in environmental characteristics and biological significance of the trenches are reviewed.
Each trench provides a unique and isolated habitat, consequently endemicity has been found to be high at the specific level
in each trench that has been adequately studied. However, the remoteness from primary food sources greatly reduces the richness
of the fauna.
The physical instability of trench habitats deriving from their high level of seismic activity, will result in the organisms
being pre-adapted to mechanical disturbance. The main threats are either direct through poisoning by toxic chemicals or indirect
through the decoupling of the trench habitat from its primary food source, or reduction in oxygen levels caused either by
eutrophication or reduction in flushing rates.
Only direct threats are considered as being at all dangerous, and any incident would be restricted to a single trench system.
these threats could be reduced by rerouting vessels carrying toxic cargoes and by improving the effectiveness of the London
Dumping Convention.
The internationally agreed criteria for the selection of sites for any proposed seabed disposal of radioactive waste exclude
the use of trenches for this purpose. 相似文献