全文获取类型
收费全文 | 1918篇 |
免费 | 21篇 |
国内免费 | 29篇 |
专业分类
安全科学 | 80篇 |
废物处理 | 131篇 |
环保管理 | 175篇 |
综合类 | 292篇 |
基础理论 | 325篇 |
污染及防治 | 635篇 |
评价与监测 | 188篇 |
社会与环境 | 131篇 |
灾害及防治 | 11篇 |
出版年
2024年 | 2篇 |
2023年 | 29篇 |
2022年 | 68篇 |
2021年 | 77篇 |
2020年 | 37篇 |
2019年 | 33篇 |
2018年 | 82篇 |
2017年 | 79篇 |
2016年 | 103篇 |
2015年 | 61篇 |
2014年 | 94篇 |
2013年 | 190篇 |
2012年 | 132篇 |
2011年 | 140篇 |
2010年 | 102篇 |
2009年 | 83篇 |
2008年 | 119篇 |
2007年 | 96篇 |
2006年 | 106篇 |
2005年 | 88篇 |
2004年 | 62篇 |
2003年 | 39篇 |
2002年 | 32篇 |
2001年 | 13篇 |
2000年 | 6篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1979年 | 2篇 |
1966年 | 2篇 |
1962年 | 2篇 |
1961年 | 2篇 |
1960年 | 2篇 |
1959年 | 2篇 |
1953年 | 2篇 |
1929年 | 1篇 |
1928年 | 2篇 |
排序方式: 共有1968条查询结果,搜索用时 875 毫秒
391.
392.
393.
Dr Antonio Perez-Aytes Nuria Sanchis Agnes Barbal Maria Jose Artés Julio Domene Melitina Chirivella Andres Baamonde 《黑龙江环境通报》1995,15(9):859-863
A large intrapericardial teratoma was found at necropsy in a 38−week stillborn fetus, in which prenatal diagnosis of hydrops fetalis and an ehogenic cardiac mass had been made. Clinical and pathological data are reported. In utero intrapericardial teratomata lead to different outcomes depending on whether fetal hydrops is associated. When generalized fetal hydrops is not present, the outcome is good, even in cases with large pericardial effusions. When generalized fetal hydrops occurs, it often results in a poor outcome. In our literature review, we have found eight perinatal deaths in nine similar cases reported. 相似文献
394.
395.
396.
Although external sexually dimorphic traits are commonly found in males of combtooth blenny species, little is known about
the benefit they can convey to male mating success. Indeed, while female preferences for large males have been demonstrated
in some species, the possible role played by dimorphic ornaments has been neglected. We now report on the tentacled blenny,
Parablennius tentacularis, a species where males are characterized by bulb glands on the anal fin and both sexes exhibit a dark spot on the dorsal
fin and orbital tentacles. Males are territorial, make nests in empty bivalve shells, and provide solitary parental care for
the eggs. Using morphometric analysis and field collected data on male and female external features, nest characteristics
and number of eggs in the nests, we have assessed the development of dimorphic traits in both sexes and male mating success.
The results reveal that orbital tentacles of males are more developed and more variable in size than those of females. Larger
males exhibit longer orbital tentacles and larger anal glands but do not necessarily occupy larger nests. Male mating success
is significantly correlated with the inner nest surface area and with orbital tentacle size but not with body size. These
results provide support for a primary role of male ornaments in enhancing blenny male mating success and are discussed in
the context of mate choice for direct and indirect benefits. 相似文献
397.
Maria I. Sandell 《Behavioral ecology and sociobiology》2007,62(2):255-262
In the European starling, Sturnus vulgaris, optimal mating systems differ between males and females. Males gain from polygyny, whereas monogamy increases female fitness.
The cost of polygyny to females lead to intense female–female competition, and it has previously been shown that the intensity
of female aggression during the pre-breeding period can predict the realised mating system. The physiological regulation of
such female aggression in starlings is not yet known. This study examines the role of testosterone in mediating aggressive
behaviours involved in intra-specific reproductive competition in female starlings. Testosterone levels were experimentally
elevated with testosterone implants in females during the pre-laying period. To simulate a situation in which an additional
female tried to mate with the focal female’s mate, a caged female was presented close to a nest-site to which the male could
attract a secondary female. Testosterone was significantly related to several behaviours involved in female–female interactions.
Females with testosterone implants spent significantly more time close to the caged female and produced more song bouts than
control females. In contrast, male behaviour was unrelated to the experimental status of the mate. Females mated to males
that attracted a secondary female were less aggressive towards the caged female than those that remained monogamously mated.
The effect of exogenous testosterone in this study indicates that androgens may mediate social behaviours in female starlings
during the breeding season. 相似文献
398.
Low Genetic Variability in the Hawaiian Monk Seal 总被引:1,自引:0,他引:1
Maria B. Kretzmann William G. Gilmartin Axel Meyer Gerard P. Zegers Steven R. Fain Bruce F. Taylor & Daniel P. Costa 《Conservation biology》1997,11(2):482-490
The Hawaiian monk seal ( Monachus schauinslandi) is a critically endangered species that has failed to recover from human exploitation despite decades of protection and ongoing management efforts designed to increase population growth. The seals breed at five principal locations in the northwestern Hawaiian islands, and inter-island migration is limited. Genetic variation in this species is expected to be low due to a recent population bottleneck and probable inbreeding within small subpopulations. To test the hypothesis that small population size and strong site fidelity has led to low within-island genetic variability and significant between-island differentiation, we used two independent approaches to quantify genetic variation both within and among the principal subpopulations. Mitochondrial control region and tRNA gene sequences (359 base pairs) were obtained from 50 seals and revealed very low genetic diversity (0.6% variable sites), with no evidence of subpopulation differentiation. Multilocus DNA fingerprints from 22 individuals also indicated low genetic variation in at least some subpopulations (band-sharing values for "unrelated" seals from the same island ranged from 49 to 73%). This method also provided preliminary evidence of population subdivision ( F'st estimates of 0.20 and 0.13 for two adjacent island pairs). Translocations of seals among islands may therefore have the potential to relieve local inbreeding and possibly to reduce the total amount of variation preserved in the population. Genetic variation is only one of many factors that determine the ability of an endangered species to recover. Maintenance of existing genetic diversity, however, remains an important priority for conservation programs because of the possibility of increased disease resistance in more variable populations and the chance that inbreeding depression may only be manifest under adverse environmental conditions. 相似文献
399.
Maria Lahtinen Lauri Kapari Vladimir Ossipov Juha-Pekka Salminen Erkki Haukioja Kalevi Pihlaja 《Chemoecology》2005,15(3):153-159
Summary. We investigated the biochemical transformation of individual phenolic compounds of mountain birch leaves in larvae of six birch-feeding sawfly species: Amauronematus amplus, Pristiphora alpestris, Nematus brevivalvis, Priophorus pallipes, Arge sp. and Nematus viridis by comparing the phenolic residues in larval faeces to those of their leaf diet. Partial hydrolysis of hydrolysable tannins, isomerisation of chlorogenic acid and glycosylation of flavonoid aglycones were observed in all studied species. Moreover, we found considerable among-species variation in the composition of phenolic compounds in larval faeces. In addition to foliar phenolics, seventeen non-foliar phenolic metabolites, including eight phenolic acids and nine flavonoid glycosides were detected from the faeces. Of the non-foliar phenolic acids, four were egested species-specifically and only two by all six sawfly species. We also detected differences in the ratios of chlorogenic acid isomers in the faeces of different species, which can indicate different physiological conditions in the guts of studied larvae. In addition to the qualitative differences, quantitative differences were detected in the egestion of chlorogenic acids, possible o-quinone precursors in the larvae. Detected differences, either qualitative or quantitative, could not be explained by seasonal changes in the content of compounds in the leaf diet. 相似文献
400.
In the routine São Paulo state (Brazil) surface water quality-monitoring program, which includes the Salmonella microsome mutagenicity assay as one of its parameters, a river where water is taken and treated for drinking water purposes has repeatedly shown mutagenic activity. A textile dyeing facility employing azo-type dyes was the only identifiable source of mutagenic compounds. We extracted the river and drinking water samples with XAD4 at neutral and acidic pH and with blue rayon, which selectively adsorbs polycyclic compounds. We tested the industrial effluent, raw, and treated water and sediment samples with YG1041 and YG1042 and compared the results with the TA98 and TA100 strains. The elevated mutagenicity detected with YG-strains suggested that nitroaromatics and/or aromatic amines were causing the mutagenicity detected in the samples analyzed. Positive responses for the blue rayon extracts indicated that mutagenic polycyclic compounds were present in the water samples analyzed. The mutagen or mixture of mutagens present in the effluent and water samples cause mainly frameshift mutations and are positive with and without metabolic activation. The Salmonella assay combined with different extraction procedures proved to be very useful in the identification of the origin of the pollution and in the identification of the classes of chemical compounds causing the mutagenic activity in the river analyzed. 相似文献