全文获取类型
收费全文 | 1725篇 |
免费 | 18篇 |
国内免费 | 44篇 |
专业分类
安全科学 | 22篇 |
废物处理 | 120篇 |
环保管理 | 174篇 |
综合类 | 149篇 |
基础理论 | 310篇 |
环境理论 | 2篇 |
污染及防治 | 580篇 |
评价与监测 | 314篇 |
社会与环境 | 110篇 |
灾害及防治 | 6篇 |
出版年
2023年 | 61篇 |
2022年 | 174篇 |
2021年 | 126篇 |
2020年 | 25篇 |
2019年 | 49篇 |
2018年 | 86篇 |
2017年 | 93篇 |
2016年 | 109篇 |
2015年 | 46篇 |
2014年 | 80篇 |
2013年 | 189篇 |
2012年 | 80篇 |
2011年 | 90篇 |
2010年 | 73篇 |
2009年 | 63篇 |
2008年 | 82篇 |
2007年 | 63篇 |
2006年 | 69篇 |
2005年 | 38篇 |
2004年 | 27篇 |
2003年 | 21篇 |
2002年 | 35篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1979年 | 2篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1962年 | 2篇 |
1961年 | 4篇 |
1958年 | 3篇 |
1957年 | 3篇 |
1956年 | 2篇 |
1955年 | 4篇 |
1953年 | 1篇 |
排序方式: 共有1787条查询结果,搜索用时 375 毫秒
721.
722.
723.
The locomotor activity rhythm of different castes of the ant species Camponotus compressus was monitored individually under laboratory light/dark (LD) cycles, and under continuous darkness (DD). The colony of this ant species comprises two sexual castes, the queens and the males, and three worker castes, namely the major, media, and minor workers. The virgin males and virgin queens display rhythmic activity patterns, but the mated queens were arrhythmic while laying eggs, with the rhythmicity resuming soon after egg-laying. Under the LD regime, major workers showed nocturnal patterns, while about 75% of the media workers displayed nocturnal patterns and about 25% showed diurnal patterns. Under the DD regime, most major workers exhibited circadian rhythm of activity with a single steady state, whereas media workers displayed two types of activity patterns, with activity patterns changing after 6–9 days in DD (turn-arounds). The pre-turn-around of the ants that showed nocturnal activity patterns during LD entrainment was <24 h after release into DD, which then became >24 h, after 6–9 days. On the other hand, the pre-turn-around of those ants that exhibited diurnal patterns during LD entrainment was first >24 h after release into DD, and then became <24 h, after 6–9 days. The activity of the minor workers neither entrained to LD cycles nor showed any sign of free-run in DD. It appears that the circadian clocks of the ant species C. compressus are flexible, and may perhaps depend upon the tasks assigned to them in the colony. 相似文献
724.
725.
726.
727.
The success of a species depends on its ability to assess its environment and to decide accordingly which behaviors are most appropriate. Many animal species, from bacteria to mammals, are able to communicate using interspecies chemicals called pheromones. In addition to exerting physiological effects on individuals, for social species, pheromones communicate group social structure. Communication of social structure is important to social insects for the allocation of its working members into coordinated suites of behaviors. We tested effects of long-term treatment with brood pheromone on suites of honey bee brood rearing and foraging behaviors. Pheromone-treated colonies reared significantly greater brood areas and more adults than controls, while amounts of stored pollen and honey remained statistically similar. Brood pheromone increased the number of pollen foragers and the pollen load weights they returned. It appeared that the pheromone-induced increase in pollen intake was directly canalized into more brood rearing. A two-way pheromone priming effect was observed, such that some workers from the same age cohorts showed an increased and extended capacity to rear larvae, while others were recruited at significantly younger ages into pollen-specific foraging. Brood pheromone affected suites of nursing and foraging behaviors allocating worker and pollen resources associated with an important fitness trait, colony growth. 相似文献
728.
This paper describes experiments on the locomotor activity rhythm of queens of the ant species Camponotus compressus, which were performed to investigate the consequences of mating on circadian clocks. Locomotor activity rhythm of virgin and mated queens was monitored individually under constant conditions of the laboratory. The locomotor activity rhythm of virgin queens entrained to a 24 h (12:12 h) laboratory light/dark (LD) cycle and free-ran under constant dim red light (RR) with a free-running period () of approximately 24 h. The locomotor activity of the mated queens on the other hand was arrhythmic during the period when they were laying eggs, and robust rhythmicity appeared soon after the egg-laying phase was over. The of the locomotor activity rhythm of mated queens was significantly greater than that of virgin queens. These results are contrary to the commonly held belief that the role of circadian clocks in ant queens ceases after mating flights, thus suggesting that circadian clocks of ant queens are adaptively plastic and display activity patterns, perhaps depending on their physiological state and tasks in the colony. 相似文献
729.
Pinealectomy shortens resynchronisation times of house sparrow (Passer domesticus) circadian rhythms
In many birds periodic melatonin secretion by the pineal organ is essential for the high-amplitude self-sustained output of
the circadian pacemaker, and thus for the persistence of rhythmicity in 24 h oscillations controlled by it. The elimination
of the pineal melatonin rhythm, or a reduction of its amplitude, renders the circadian pacemaker a less self-sustained, often
highly damped, oscillatory system. A reduction in the degree of self-sustainment of a rhythm should not only increase its
range of entrainment but also shorten the resynchronization times following phase-shifts of the zeitgeber. This hypothesis
has not yet been directly tested. We therefore carried out the present study in which house sparrows (Passer domesticus) were subjected to both 6-h advance and 6-h delay phase-shifts of the light–dark cycle before and after the pinealectomy,
and the rhythms in locomotion and feeding were recorded. The results indicate that following the delay, but not the advance,
phase shift, resynchronization times were significantly shorter after pinealectomy. The dependence of resynchronization times
on the presence or absence of the pineal organ is not only of theoretical interest but might also be of functional significance
in the natural life of birds. A reduction or elimination of the amplitude of the melatonin secretion rhythm by the pineal
organ might be responsible for faster adjustment to changes in zeitgeber conditions in nature.
Professor Dr E. Gwinner died on 07 September 2004. 相似文献
730.
Senthil Kumar K Bowerman WW DeVault TL Takasuga T Rhodes OE Lehr Brisbin I Masunaga S 《Chemosphere》2003,53(2):173-182
Blood of adult and juvenile black and turkey vultures in the Savannah River Site of South Carolina, USA was analyzed for the presence of 2,3,7,8-chlorine substituted polychlorinated dibenzo-p-dioxins (2,3,7,8-PCDDs), dibenzofurans (2,3,7,8-PCDFs), -dioxin-like and -di-ortho polychlorinated biphenyls. Concentration ranges of 2,3,7,8-PCDD/DFs in blood of black and turkey vultures were 14.2-34.6 and 8.7-56.2 pg/ml wet wt., respectively. Dioxin-like PCBs were in the ranges of 815-4627 and 753-3611 pg/ml wet wt. respectively, in black and turkey vultures. Considerable concentrations of two congeners of di-ortho PCBs were noticed in the ranges of 1415-10325 and 663-7500 pg/ml respectively, in black and turkey vultures. Comparatively, greater toxic equivalency (TEQ) were observed in blood of turkey vultures with the ranges of 3.2-20, whereas black vulture contained 1.8-8.4 pgTEQ/ml wet wt. basis. The species-specific accumulation profiles of PCDD/DFs and dioxin-like PCBs may reflect the different feeding habits, ecology, metabolic capacity and migratory movements of these two scavenging species. 相似文献