全文获取类型
收费全文 | 3060篇 |
免费 | 7篇 |
国内免费 | 38篇 |
专业分类
安全科学 | 67篇 |
废物处理 | 145篇 |
环保管理 | 311篇 |
综合类 | 427篇 |
基础理论 | 1193篇 |
污染及防治 | 590篇 |
评价与监测 | 191篇 |
社会与环境 | 181篇 |
出版年
2022年 | 2篇 |
2021年 | 9篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 116篇 |
2017年 | 120篇 |
2016年 | 191篇 |
2015年 | 55篇 |
2014年 | 23篇 |
2013年 | 34篇 |
2012年 | 433篇 |
2011年 | 223篇 |
2010年 | 42篇 |
2009年 | 40篇 |
2008年 | 57篇 |
2007年 | 71篇 |
2006年 | 73篇 |
2005年 | 399篇 |
2004年 | 554篇 |
2003年 | 407篇 |
2002年 | 44篇 |
2001年 | 43篇 |
2000年 | 18篇 |
1999年 | 32篇 |
1998年 | 5篇 |
1997年 | 11篇 |
1996年 | 3篇 |
1995年 | 12篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1966年 | 2篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1938年 | 1篇 |
1937年 | 1篇 |
1932年 | 1篇 |
1926年 | 1篇 |
1924年 | 1篇 |
排序方式: 共有3105条查询结果,搜索用时 406 毫秒
731.
Feeding behaviors of the gastropods Batillaria zonalis, a suspension and deposit feeder, and Cerithideopsilla cingulata, an obligate deposit feeder, were studied to examine their effect on dynamics of suspended materials, total nitrogen (TN) and total organic carbon (TOC) in sediments. Suspension feeding in B. zonalis was observed in detail visually, as it had been previously unreported. An experimental system where B. zonalis and C. cingulata were cultured for 10 weeks, using previously frozen microalgae Nannochloropsis oculata as food, was then constructed. During feeding observations, the suspension-feeding B. zonalis formed a mucus food cord to entangle particulate materials, which were subsequently ingested. The feeding mode of B. zonalis is hence categorized as ctenidial filter feeding. For the culture experiments, decreases in suspended materials were seen only in the B. zonalis cultures, while the control (no gastropods) and C. cingulata cultures remained nearly unchanged. Sediment TN and TOC showed no significant differences between B. zonalis (with mean TN at 0.0345% and mean TOC at 0.261%) and control cultures (with TN at 0.0389% and TOC at 0.331%), but the sediments in C. cingulata cultures had lower levels (with TN at 0.0204% and TOC at 0.156%). The C/N ratios were similar for both B. zonalis (7.55) and C. cingulata (7.68) cultures, and both were lower than the control cultures (8.55). The filtration rate for B. zonalis was lower than that previously observed in bivalves inhabiting the same intertidal flat (e.g. Cyclina sinensis, Grafrarium tumidum and Barbatia virescens). However, Batillaria zonalis occurs at higher abundances than these bivalves. Therefore, it is expected that this species has a large affect upon the transport of suspended materials to the sediments. The addition of TN and TOC to sediments in B. zonalis cultures was probably caused by biodeposition, but deposit feeding by B. zonalis may have restrained the accumulation of those components. The impact of deposit feeding in Cerithideopsilla cingulata cultures was most probably stronger than sedimentation and biodeposition, because of the lower sediment TN and TOC. Bioturbation by both B. zonalis and C. cingulata yields the same effect on sediment quality, as indicated by the low C/N in the culture sediment of both treatments, despite difference in feeding modes. This paper demonstrates, for the first time, the importance of gastropods in bioturbation and removal of suspended materials in subtropical tidal flat habitats.Communicated by T. Ikeda, Hakodate 相似文献
732.
E.?Cocheret de la Morinière I.?Nagelkerken H.?van der?Meij G.?van der?VeldeEmail author 《Marine Biology》2004,144(1):139-145
The value of mangroves for fish species is usually explained in terms of high food abundance or shelter against predators as a result of high turbidity and structural complexity. In a field experiment, artificial mangrove units (AMUs) were designed as open cages, each of which was provided with a different degree of structural complexity and shade. Fish species that were attracted to the AMUs were identified and counted and the effects of shade and structural complexity, as well as the interaction between the two factors, were tested. Diurnal fish showed a preference for the greatest structured complexity and for a moderate increase in shade. Two nocturnal species common in local mangroves as well as seagrass beds showed statistically significant effects: densities of Haemulon sciurus were positively related to both shade and structural complexity, whereas only shade had a significant positive effect on densities of Ocyurus chrysurus. The experiment indicated that the attractiveness of mangrove vegetation for H. sciurus may be influenced by the structural complexity of the habitat as well as by the degree of shade, and that both factors are equally and separately important. Individuals of O. chrysurus that are attracted to mangroves are more likely to be influenced by the presence of shade than by the degree of structural complexity. The data thus indicated that the positive relationship between fish densities in mangrove habitats and the degree of shade and structural complexity, or both, is species-specific.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
733.
Strategic investment in reputation 总被引:1,自引:0,他引:1
Dirk?SemmannEmail author Hans-Jürgen?Krambeck Manfred?Milinski 《Behavioral ecology and sociobiology》2004,56(3):248-252
Although collective efforts are common in both animal and human societies, many human and probably animal social dilemmas have no obvious cooperative solution, which is a challenge for evolutionary biologists. In public goods games, i.e. the experimental paradigm for studying the sustainability of a public resource with human subjects, initial cooperation usually declines quickly. Recently, it has been shown that the interaction with another social game in which good reputation attracts help, can maintain a high level of cooperation in the public goods game. Here we show experimentally that humans use different strategies in the public goods game conditional on whether the player knows that his decisions will be either known or unknown in another social game. The knowledge of being recognized as the same individual in both scenarios motivates players to invest in their reputation and thus sustain the public resource. However, cooperation declines immediately when individual identities switch from being recognizable to being unrecognizable between the two interacting games.Communicated by M. Borgerhoff-Mulder 相似文献
734.
Eve?McDonald-MaddenEmail author Mark?A.?Elgar Kathrine?A.?Handasyde 《Behavioral ecology and sociobiology》2004,56(4):322-327
The costs of reproduction are widely recognised as a major selective force in the evolution of various behavioural and life-history characteristics. In particular, the behaviour of reproductively active animals is likely to change when breeding increases risk of predation. We investigated the effect of an experimentally derived threat on the vigilance and escape behaviour of female Trichosurus caninus with and without dependent offspring and at different stages of offspring development. Females with offspring showed a heightened response to the threat in comparison to females without offspring. In addition, females with offspring displayed a stronger response at earlier stages of their offsprings development.Communicated by P. Bednekoff 相似文献
735.
John?YangEmail author Jianguo?Sun David?Hammer Robert?Blanchar 《Environmental Chemistry Letters》2004,2(3):159-162
Soil pH, a log-transformed form of hydrogen ion (H+) activity, is often used for various statistics. However whether soil pH meets the requirement of distribution normality for statistical analyses is unknown. We studied the statistical suitability of both soil pH and H+ activity by examining their distribution normalities. Results show that the variability of H+ activity is higher and its distribution is skewer, which is significantly different from the normal and soil pH, regardless of soil conditions and analytical methods. Here we demonstrate that soil pH is more appropriate than the H+ activity for performing statistical analysis in terms of distribution normality. 相似文献
736.
Benjamin?TooheyEmail author Gary?A.?Kendrick Thomas?Wernberg Julia?C.?Phillips Sairah?Malkin Jane?Prince 《Marine Biology》2004,144(5):1019-1027
Kelp canopies have long been recognised for their influence on the structure of algal assemblages on sublittoral reefs. In Marmion Lagoon, Western Australia, we investigated how a canopy of the small kelp Ecklonia radiata affected the associated foliose algal assemblage and what potential mechanisms were responsible for the effects we observed. Light levels and physical abrasion (thallus scour) by an E. radiata canopy were manipulated in an orthogonal fixed-factor experiment that revealed that changes in light, but not thallus scour, had a significant effect on the composition of the algal assemblage. Reduced light levels were associated with a decrease in the Shannon-Wiener diversity index and an increased dominance of the foliose algae Pterocladia lucida and Rhodymenia sonderi. Photobiological investigations of three foliose species, P. lucida, R. sonderi and Chauviniella coriifolia indicated that they were able to photoacclimate to low light levels by increasing thallus absorption by up to 11%. Photoacclimation was also evident by an increase in the maximum rate of electron transport under low-light conditions. We conclude that the E. radiata canopy in Marmion Lagoon structures the foliose algal assemblage through the modification of the light environment and that this effect may be mediated by differences in the ability of different species of foliose algae to photoacclimate.Communicated by M.S. Johnson, Crawley 相似文献
737.
738.
739.
740.
Markus??stEmail author Ron?Ydenberg Kai?Lindstr?m Mikael?Kilpi 《Behavioral ecology and sociobiology》2003,54(5):451-457
Both theoretical and empirical work has shown that group size increases with increasing ecological constraints on solitary breeding. Ecological constraints refer to extrinsic factors such as availability of breeding sites, food or mates. Common eider (Somateria mollissima) females pool their broods and share brood-rearing duties, or rear broods alone. Females are often in poor condition at hatching, as incubation is accomplished without feeding, and variation in body condition is largely environmentally induced and thus unpredictable. We found that the intensity of and duration of parental care that females provide is positively correlated with their body condition at hatching. This suggests that body condition is an ecological constraint on successful solitary breeding. We further observed that group productivity in common eider broods is a decelerating function of the number of tending females. As predicted, females in poorer condition (i.e., facing stronger ecological constraints) were found in larger groups. This result is straightforward if solitary tenders can enter any group at no cost. However, if entry is group-controlled, stable groups of non-relatives are predicted not to occur when per capita reproduction declines with group size. The N-person staying incentive model permits groups to form under these conditions, because reproduction is unevenly divided between dominants and subordinates in the group. We discuss the plausibility of these alternative models of group size for understanding the grouping behavior of brood-caring female common eiders.Communicated by M. Webster 相似文献