全文获取类型
收费全文 | 734篇 |
免费 | 16篇 |
国内免费 | 5篇 |
专业分类
安全科学 | 30篇 |
废物处理 | 20篇 |
环保管理 | 89篇 |
综合类 | 188篇 |
基础理论 | 205篇 |
环境理论 | 2篇 |
污染及防治 | 162篇 |
评价与监测 | 29篇 |
社会与环境 | 21篇 |
灾害及防治 | 9篇 |
出版年
2023年 | 10篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 15篇 |
2019年 | 9篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 21篇 |
2015年 | 22篇 |
2014年 | 18篇 |
2013年 | 34篇 |
2012年 | 37篇 |
2011年 | 54篇 |
2010年 | 30篇 |
2009年 | 35篇 |
2008年 | 26篇 |
2007年 | 42篇 |
2006年 | 30篇 |
2005年 | 20篇 |
2004年 | 13篇 |
2003年 | 7篇 |
2002年 | 23篇 |
2001年 | 15篇 |
2000年 | 7篇 |
1999年 | 15篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1995年 | 5篇 |
1992年 | 6篇 |
1989年 | 5篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1977年 | 5篇 |
1976年 | 11篇 |
1974年 | 5篇 |
1971年 | 4篇 |
1967年 | 6篇 |
1965年 | 4篇 |
1964年 | 4篇 |
1961年 | 7篇 |
1960年 | 4篇 |
1957年 | 5篇 |
1956年 | 4篇 |
1948年 | 4篇 |
1937年 | 6篇 |
1920年 | 5篇 |
排序方式: 共有755条查询结果,搜索用时 15 毫秒
131.
Hans Horst Meyer 《Die Naturwissenschaften》1934,22(36):598-601
132.
133.
Kurt H. Meyer 《Die Naturwissenschaften》1927,15(6):129-134
134.
Both phytophagous and parasitic insects deposit oviposition-marking pheromones (OMPs) following oviposition that function
to inform conspecifics of a previously utilized host of reduced suitability. The blueberry maggot fly, Rhagoletis mendax Curran (Diptera: Tephritidae), deposits eggs individually into blueberries and then marks the fruit surface with an OMP which
reduces acceptance of fruit for oviposition by conspecifics. Diachasma alloeum (Muesebeck) (Hymenoptera: Braconidae) is a parasitic wasp attacking larval R. mendax which also deposits an OMP, signaling conspecifics of a wasp-occupied host. Behavioral studies were conducted testing the
hypothesis that the OMP of the parasitic wasp modifies the oviposition behavior of its host fly. In this study, we show that
the OMP of D. alloeum is recognized by R. mendax, and female flies will reject wasp-marked fruit for oviposition. Thus, we present a rare demonstration of pheromonal recognition
between animals occupying different taxonomic orders and trophic levels. This chemical eavesdropping may enhance the ability
of the fly to avoid fruit unsuitable for larval development. 相似文献
135.
Voluntary environmental governance is a widely used policy approach that has been criticized for its lack of effectiveness. This raises fundamental questions about how to design processes that can advance voluntary programmes in a way that makes them more successful. In this paper, we analyse a government-initiated dialogue process to phase out hazardous chemicals through voluntary action by the Swedish textile industry. The analysis shows that information transfer primarily motivated business participation, while consumer pressure, regulatory threats and traditions of government–business cooperation played minor roles. The institutional design of the dialogue ensured close interaction within a homogeneous group, but collective actions were limited by disagreement about the problems to be addressed, prior unilateral environmental commitments by leading companies, and ambivalent engagement. This case provides valuable insights into the effect of institutional design on the actual interplay between business and government and its effects on voluntary governance. 相似文献
136.
The giant clam Tridacna crocea harbors in the mantle tissue symbiotic microalgae commonly called zooxanthellae. Isolated zooxanthellae release glycerol
into the medium in the presence of mantle tissue homogenate (MH), but it is not clear whether the cells do so in situ. In
order to determine the photosynthetic products released by zooxanthellae in the mantle of the giant clam we traced photosynthetic
fixation products from 13C- and 14C-bicarbonate both in the clam and in isolated zooxanthellae (IZ) in the presence or absence of MH. After 15 min incubation
in the absence of MH the IZ released less than 0.6% of the fixed labeled carbon, mainly as glucose. The major intracellular
photosynthates were neutral lipids, which constituted 20 to 40% of the total extractable 14C. In the presence of MH, the IZ released up to 5.6% of the total fixed 14C, mostly as glycerol, and the major intracellular photosynthate was glucose. In an intact clam incubated in sea water containing
14C-bicarbonate, 46 to 80% of the fixed 14C was translocated from the zooxanthellae to the host tissues. Most of the 14C in the hemolymph, in the isolated zooxanthellae and in intact mantle tissue (containing zooxanthellae) was recovered as
glucose. No 14C-glycerol was detected in the mantle after 1 to 30 min incubation, and, even after 60 min, far less 14C-glycerol was synthesized than by IZ in the presence of MH. The possibility that in clam tissue glycerol is converted to
glucose was examined by tracing the labeled carbon from 14C-glycerol injected into the adductor muscle. After 5 min incubation, no labeled glucose was found in the hemolymph, but after
60 min, some 20% was found as glucose. Thin slices containing zooxanthellae, cut from the surface of the mantle, fixed inorganic
carbon supplied as NaH14CO3 in the medium and mainly released 14C-glucose. The addition of MH to the surrounding medium did not affect the release rate or form of release product. When the
slices were cut into smaller pieces, however, the ratio of glycerol to glucose in the release product increased. These results
indicate that in the presence of MH the metabolism of isolated zooxan- thellae was different from that of zooxanthellae in
the mantle. In the presence of MH, isolated zooxanthellae release mostly glycerol, whereas in the mantle they release glucose.
Received: 18 February 1998 / Accepted: 4 December 1998 相似文献
137.
138.
Christian Sonne PhD DVM VMD MVSc Rossana Bossi Rune Dietz Pall S. Leifsson Frank F. Rigét Erik W. Born 《毒物与环境化学》2013,95(2):275-283
In this study, residual concentrations of chlorpyrifos (CPF) were determined in feed (40) and fodder (25) samples collected from various locations of Tarai region of Uttarakhand. For extracting residues, liquid–liquid partition followed by alumina column clean up was used and the detection and quantification of residues was undertaken with the help of high-performance liquid chromatography using C18 column and diode array detector at 220?nm. Of the total 40 feed samples analyzed, 7 (17.5%) samples were found positive for CPF with the mean residual concentration of 0.058?µg?g?1; while out of 25 fodder samples, CPF residues were detected in a single (4%) sample with residual concentration of 0.39?µg?g?1. However, none of the feed or fodder samples contained CPF residues above the prescribed limit. 相似文献
139.
The factors that determine species' range limits are of central interest to biologists. One particularly interesting group comprises odonates (dragonflies and damselflies), which show large differences in secondary sexual traits and respond quickly to climatic factors, but often have minor interspecific niche differences, challenging models of niche-based species coexistence. We quantified the environmental niches at two geographic scales to understand the ecological causes of northern range limits and the coexistence of two congeneric damselflies (Calopteryx splendens and C. virgo). Using environmental niche modeling, we quantified niche divergence first across the whole geographic range in Fennoscandia, and second only in the sympatric part of this range. We found evidence for interspecific divergence along the environmental axes of temperature and precipitation across the northern range in Fennoscandia, suggesting that adaptation to colder and wetter climate might have allowed C. virgo to expand farther north than C. splendens. However, in the sympatric zone in southern Fennoscandia we found only negligible and nonsignificant niche differences. Minor niche differences in sympatry lead to frequent encounters and intense interspecific sexual interactions at the local scale of populations. Nevertheless, niche differences across Fennoscandia suggest that species differences in physiological tolerances limit range expansions northward, and that current and future climate could have large effects on the distributional ranges of these and ecologically similar insects. 相似文献
140.
Effects of predation may cascade down the food web. By alleviating interspecific competition among prey, predators may promote biodiversity, but the precise mechanisms of how predators alter competition have remained elusive. Here we report on a predator-exclosure experiment carried out in a tropical intertidal ecosystem, providing evidence for a three-level trophic cascade induced by predation by molluscivore Red Knots (Calidris canutus) that affects pore water biogeochemistry. In the exclosures the knots' favorite prey (Dosinia isocardia) became dominant and reduced the individual growth rate in an alternative prey (Loripes lucinalis). Dosinia, a suspension feeder, consumes suspended particulate organic matter (POM), whereas Loripes is a facultative mixotroph, partly living on metabolites produced by sulfur-oxidizing chemoautotrophic bacteria, but also consuming suspended POM. Reduced sulfide concentrations in the exclosures suggest that, without predation on Dosinia, stronger competition for suspended POM forces Loripes to rely on energy produced by endosymbiotic bacteria, thus leading to an enhanced uptake of sulfide from the surrounding pore water. As sulfide is toxic to most organisms, this competition-induced diet shift by Loripes may detoxify the environment, which in turn may facilitate other species. The inference that predators affect the toxicity of their environment via a multi-level trophic cascade is novel, but we believe it may be a general phenomenon in detritus-based ecosystems. 相似文献