全文获取类型
收费全文 | 1885篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
安全科学 | 39篇 |
废物处理 | 58篇 |
环保管理 | 108篇 |
综合类 | 647篇 |
基础理论 | 328篇 |
环境理论 | 7篇 |
污染及防治 | 547篇 |
评价与监测 | 85篇 |
社会与环境 | 74篇 |
灾害及防治 | 3篇 |
出版年
2021年 | 15篇 |
2020年 | 14篇 |
2019年 | 16篇 |
2018年 | 34篇 |
2017年 | 39篇 |
2016年 | 40篇 |
2015年 | 34篇 |
2014年 | 47篇 |
2013年 | 98篇 |
2012年 | 37篇 |
2011年 | 79篇 |
2010年 | 52篇 |
2009年 | 59篇 |
2008年 | 87篇 |
2007年 | 88篇 |
2006年 | 68篇 |
2005年 | 64篇 |
2004年 | 39篇 |
2003年 | 47篇 |
2002年 | 48篇 |
2001年 | 58篇 |
2000年 | 39篇 |
1999年 | 28篇 |
1998年 | 18篇 |
1997年 | 18篇 |
1996年 | 17篇 |
1995年 | 18篇 |
1994年 | 31篇 |
1993年 | 13篇 |
1991年 | 15篇 |
1984年 | 14篇 |
1981年 | 16篇 |
1975年 | 12篇 |
1974年 | 12篇 |
1972年 | 12篇 |
1969年 | 14篇 |
1968年 | 13篇 |
1967年 | 15篇 |
1966年 | 23篇 |
1965年 | 29篇 |
1964年 | 16篇 |
1963年 | 25篇 |
1962年 | 22篇 |
1961年 | 30篇 |
1960年 | 20篇 |
1959年 | 21篇 |
1958年 | 13篇 |
1957年 | 24篇 |
1956年 | 16篇 |
1955年 | 16篇 |
排序方式: 共有1896条查询结果,搜索用时 31 毫秒
931.
A test of male mating and hunting success in the kestrel: the advantages of smallness? 总被引:2,自引:0,他引:2
H. Hakkarainen E. Huhta Katriina Lahti Päivi Lundvall Tapio Mappes Pasi Tolonen Jürgen Wiehn 《Behavioral ecology and sociobiology》1996,39(6):375-380
We tested female choice for male wing and tarsus length and body mass in the kestrel (Falco tinnunculus), a species in which males average about 10% smaller than females. We also studied how male characters are related to their
hunting success. In the laboratory, females preferred lighter males with shorter tarsi as mates, if the difference in those
characters between competing males was larger than average. Lighter and shorter-winged males seemed to be better hunters than
heavier and longer-winged males. Field observations in a year in which voles were scarce suggested that shorter-winged males
were also better food providers in courtship feeding than longer-winged males,although in good vole years such a relationship
was not found. We argue that females may prefer to pair with smaller males, because they have higher flight performance and
better hunting success than heavier males. By doing so, females may gain direct breeding advantages. We conclude that both
female choosiness and the hunting efficiency of males well contribute to reversed sexual size dimorphism (RSD, females larger
than males) in the kestrel.
Received: 18 July 1995/Accepted after revision: 17 August 1996 相似文献
932.
Osmo Rätti Matti Hovi Arne Lundberg Håkan Tegelström Rauno V Alatalo 《Behavioral ecology and sociobiology》1995,37(6):419-425
The pied flycatcher (Ficedula hypoleuca) is sexually dichromatic with extreme variation in male plumage coloration. The benefit for males of having black plumage is controversial, and few studies have found evidence for a sexual selection benefit of being black rather than brown. However, blacker males may be better able to achieve extra-pair fertilizations (EPFs), which may be an important component of sexual selection. We studied the role of EPFs in sexual selection in the pied flycatcher by establishing a set-up where two males with different back coloration (blacker vs browner) bred simultaneously near each other. DNA fingerprinting analysis revealed that 11% of offspring resulted from EPFs, and that 22% of broods included extra-pair young (EPY) among 36 nests containing 223 nestlings. We found no evidence that browner males suffered more often from EPFs than blacker males. There was no correlation of male or female morphology or age with EPF frequency. However, breeding pairs with low genetic similarity had EPY in their nests significantly more often. Thus we argue that females paired with genetically dissimilar males may try to avoid the effects of extreme outbreeding by seeking extra-pair copulations (EPCs). Alternatively, incompatibility between genetically dissimilar mates may simply expose females to more extra-pair copulations. 相似文献
933.
Chapin FS Peterson G Berkes F Callaghan TV Angelstam P Apps M Beier C Bergeron Y Crépin AS Danell K Elmqvist T Folke C Forbes B Fresco N Juday G Niemelä J Shvidenko A Whiteman G 《Ambio》2004,33(6):344-349
The arctic tundra and boreal forest were once considered the last frontiers on earth because of their vast expanses remote from agricultural land-use change and industrial development. These regions are now, however, experiencing environmental and social changes that are as rapid as those occurring anywhere on earth. This paper summarizes the role of northern regions in the global system and provides a blueprint for assessing the factors that govern their sensitivity to social and environmental change. 相似文献
934.
It has been suggested that nestlings use begging to increase their share of parental resources at the expense of current
or future siblings. There is ample evidence that siblings compete over food with nestmates by begging, but only short-term
effects of begging on parental provisioning rates have been shown. In this study, we use a new experimental design to demonstrate
that pied flycatcher (Ficedula hypoleuca) nestlings that beg more are able to increase parental provisioning rates over the major part of the nestling period, thus
potentially competing with future siblings. Parents were marked with microchips so that additional begging sounds could be
played back when one of the parents visited the nest. By playing back begging sounds consistently at either male or female
visits, a sex difference in provisioning rate that lasted for the major part of the nestling period was induced. If each parent
independently adjusts its effort to the begging intensity of nestlings, begging may also be the proximate control mechanism
for the sexual division of labour.
Received: 24 January 1997 / Accepted after revision: 30 August 1997 相似文献
935.
There is genetic variation in the female mating rate in the green-veined white butterfly (Pieris napi), and females benefit from male ejaculates that contain both sperm and accessory gland substances. Although polyandry corresponds to higher lifetime fecundity than monandry, some females abstain from remating irrespective of the number of available mates. Explaining genetic variation in mating rates requires that monandrous females perform better than polyandrous ones under some conditions. We experimentally explored the reproductive performance of females either with a low or high intrinsic mating rate by allowing them to mate, feed, and lay eggs freely in a laboratory. Individual females followed different life histories: during the early days of reproduction, females with a low mating rate produced more eggs than females with a high mating rate. Hence, refraining from the benefits of multiple mating may be beneficial, if the time for reproduction is limited, or other female traits associated with polyandry are traded off against longevity. Given the day length of 10 h, a model shows that even if polyandrous females enjoy higher lifetime reproductive success, changeable and unpredictable weather will favor monandry if each period of suitable weather lasts, on average, less than 5 days. Thus, a combination of life history cost and unpredictability of fitness may explain the maintenance of monandry in the wild. Our results are also consistent with the observation that frequency of monandry increases with latitude. 相似文献
936.
Susanna Andersson 《Chemoecology》2003,13(1):13-20
Summary. To better understand the biological role of floral scents for
butterflies, electrophysiological responses to floral scents were
investigated using combined gas chromatography and electroantennographic
detection (GC-EAD). The antennal responses of three butterfly species,
Aglais urticae L. (Nymphalidae), Inachis io L. (Nymphalidae), and
Gonepteryx rhamni L. (Pieridae) to floral scent compounds from both
natural and synthetic mixtures were examined. Floral scents were
collected from the butterfly nectar plants Cirsium arvense (L.)
(Asteraceae), and Buddleja davidii Franchet cv. (Loganicaeae) with
dynamic head-space methods on Tenax-GR and eluted with pentane. These
eluates, composed of natural floral scent blends, represent an array of
compounds in their natural state. In the GC-EAD analyses eleven
compounds were identified from C. arvense with the benzenoid compound
phenylacetaldehyde in highest abundance. Seventeen compounds were
identified from B. davidii with the irregular terpene oxoisophorone in
highest abundance. Thirty-nine synthetic floral scent compounds were
mixed in pentane, in equal amounts; about 35 ng were allowed to reach
the antennae. The butterflies showed antennal responses to most of the
floral scent compounds from both natural and synthetic blends except to
the highly volatile monoterpene alkenes. Certain benzenoid compounds
such as phenylacetaldehyde, monoterpenes such as linalool, and irregular
terpenes such as oxoisophorone, were emitted in relatively large amounts
from C. arvense and B. davidii, and elicited the strongest antennal
responses. These compounds also elicited strong antennal responses when
present in the synthetic scent blends. Thus, the butterflies seem to
have many and /or sensitive antennal receptors for these compounds,
which points to their biological importance. Moreover, these compounds
are exclusively of floral scent origin. For B. davidii, which depends
highly on butterflies for pollination, the exclusive floral scent
compounds emitted in high abundance could be the result of an adaptive
pressure to attract butterflies.
Received 2 Septemter 2001; accepted 9 September 2002. 相似文献
937.
The main source of human exposure to persistent organic pollutants (POPs) is, in general, food. In this study, 64 butter samples from 37 countries were analyzed to assess the global contamination of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs), hexachlorobenzene (HCB), and 2,2-bis (4-chlorophenyl)-1,1,1-trichloroethane (DDT) together with its major metabolites. The objectives of the study were to assess the presence of major organohalogen contaminants in butter, to trace geographical differences, and to determine toxic equivalents (TEQs) of PCDDs/Fs and dioxin-like PCBs in butter. The highest PCDD/F concentrations were found in butter from Korea with an average of 1.4 pg TEQ g(-1) lipid weight (l.w.). from PCDD/F and an additional contribution from the non- and mono-ortho-PCBs of 0.55 pg TEQ g(-1) l.w. Belgian butter showed average levels of 0.53 and 1.2 pg TEQ g(-1) l.w. for PCDDs/Fs and PCBs, respectively, but one sample of Belgium butter had a total TEQ level as high as 4.0 pg TEQ g(-1) l.w. Three out of five butter samples from Portugal showed similarly high PCDD/F TEQ levels. The sigmaPCB levels in European butter appeared to be somewhat higher than in the samples from the rest of the world. The average contribution of CB-153 to the total PCB concentration was 22% (SD 6.4, coefficient of variation 29%). Generally, the PCBs contributed around 60% of the total TEQ value, with CB-126 contributing approximately half of this value. This shows the important TEQ contribution from dioxinlike PCBs to the total TEQs. The highest HCB levels were found in butter samples from Russia, Ukraine, Belgium, and Slovenia. Low levels of HCB in butter were generally found in the Southern Hemisphere. Butter samples from countries from Eastern Europe had elevated sigmaDDT concentrations, with a particularly high concentration in Ukraine butter, followed by some Russian samples, Brazil, and the U.S. 相似文献
938.
Removal of DEHP in composting and aeration of sewage sludge 总被引:4,自引:0,他引:4
The potential of composting and aeration to remove bis(2-ethylhexyl) phthalate (DEHP) from municipal sewage sludge was studied with two dewatered sludges: raw sludge and anaerobically digested sludge. Composting removed 58% of the DEHP content of the raw sludge and 34% of that of the anaerobically digested sludge during 85 days stabilisation in compost bins. A similar removal for the anaerobically digested sludge was achieved in a rotary drum in 28 days. Less than 1% of DEHP was removed with the compost leachate. Although DEHP removal was greater from raw sludge compost than anaerobically digested sludge compost, the total and volatile solids removals were on the same level in the two composts. In the aeration of raw sludge at 20 degrees C the DEHP removals were 33-41% and 50-62% in 7 and 28 days, respectively. Both composting and aeration are concluded to have the potential to reduce the DEHP contents typically found in sewage sludges to levels acceptable for agricultural use. 相似文献
939.
Petänen T Lyytikäinen M Lappalainen J Romantschuk M Kukkonen JV 《Environmental pollution (Barking, Essex : 1987)》2003,122(3):407-415
Three sediment samples LP (pool where logs are stored), LF (brook through landfill area), KN (Kaskesniemi) which is in Lake Pyh?selk? downstream from the mill, were taken from an old sawmill area and one from the unpolluted Lake H?yti?inen. The arsenite concentration was measured by GFAAS and two arsenite biosensing bacterial strains Pseudomonas fluorescens OS8 (pTPT31) and Escherichia coli MC1061 (pTOO31). The toxicity of sediment and pore water samples was determined by using luminescent bacteria (Flash test) and, further, whole sediment toxicity was measured using 10 days growth test and 50 days emergency test with midges (Chironomus riparius). With the flash test a lowered EC50 value was found only in sediment LF (EC50=0.17 v/v%). The Flash test indicated that all sediment samples taken from the sawmill area were highly toxic to bacteria, whereas growth and the emergence of chironomids showed no effects in other samples than LF. The midges tolerate well the contaminated environment. In contrast, bioavailability of arsenite of sediment samples KN and LF was quite high determined using the biosensor-strains in a direct contact assay. The bioavailable fraction of sediment LP was 6-10% out of the total arsenite concentration obtained with GFAAS (0.46-0.77 microg g-1 dw). The results show that the choice of analysis method grossly affects the outcome without any of the method giving an incorrect result. Different methods measure different parameters of a toxic sample and can thus be used to complement each other. 相似文献
940.
Bioavailability, toxicokinetics and toxicity (LC(50)) of water- and sediment-associated 2,4,5-trichlorophenol (2,4,5-TCP) and pentachlorophenol (PCP) were measured in Lumbriculus variegatus Müller in a set of experiments. The critical body residue approach was applied by measuring also the lethal body residues (LBR(50)). Freshwater and three different sediments with various sediment organic carbon (SOC) concentrations were used as exposure media. SOC decreased the bioavailability of both chlorophenols, and the uptake rates decreased by 81% and 91% for 2,4,5-TCP and PCP, respectively, in the sediment with a SOC of 6.9% compared to those in sediment with a SOC of 0.5%. SOC appeared to be an important factor controlling the bioavailability as after the carbon normalisation the difference between the sediments was much smaller. The 96-h LC(50) values for instance for PCP were 145.3 microg/l in freshwater, and 6.8 and 8.1 microg/g dry weight in sediments with SOC concentrations of 0.5% and 2.4%, respectively. The LBR(50) values, were practically the same in freshwater and sediments: between 1.0 and 1.6 and from 0.4 to 0.9 micromol/g wet weight for 2,4,5-TCP and PCP, respectively, demonstrating the usefulness of this method for accurate, and more comparable, measurement of toxicity of chemicals with the same mode of toxic action in varying conditions. L. variegatus expressed a dose-response sediment avoidance behaviour but the PCP tissue concentrations were not affected by this behaviour. 相似文献