全文获取类型
收费全文 | 4108篇 |
免费 | 29篇 |
国内免费 | 5篇 |
专业分类
安全科学 | 66篇 |
废物处理 | 156篇 |
环保管理 | 186篇 |
综合类 | 1500篇 |
基础理论 | 860篇 |
环境理论 | 8篇 |
污染及防治 | 1005篇 |
评价与监测 | 189篇 |
社会与环境 | 166篇 |
灾害及防治 | 6篇 |
出版年
2022年 | 30篇 |
2019年 | 40篇 |
2018年 | 78篇 |
2017年 | 82篇 |
2016年 | 97篇 |
2015年 | 88篇 |
2014年 | 106篇 |
2013年 | 190篇 |
2012年 | 98篇 |
2011年 | 178篇 |
2010年 | 120篇 |
2009年 | 123篇 |
2008年 | 199篇 |
2007年 | 166篇 |
2006年 | 146篇 |
2005年 | 118篇 |
2004年 | 106篇 |
2003年 | 98篇 |
2002年 | 129篇 |
2001年 | 81篇 |
2000年 | 72篇 |
1999年 | 49篇 |
1998年 | 40篇 |
1997年 | 38篇 |
1996年 | 44篇 |
1995年 | 47篇 |
1994年 | 47篇 |
1993年 | 29篇 |
1992年 | 43篇 |
1991年 | 37篇 |
1990年 | 37篇 |
1989年 | 32篇 |
1981年 | 30篇 |
1976年 | 32篇 |
1973年 | 29篇 |
1968年 | 29篇 |
1967年 | 34篇 |
1966年 | 30篇 |
1965年 | 47篇 |
1964年 | 37篇 |
1963年 | 36篇 |
1962年 | 31篇 |
1961年 | 44篇 |
1960年 | 39篇 |
1959年 | 41篇 |
1958年 | 45篇 |
1957年 | 39篇 |
1956年 | 40篇 |
1955年 | 37篇 |
1954年 | 40篇 |
排序方式: 共有4142条查询结果,搜索用时 412 毫秒
751.
752.
In mammals, the chemical profiles of individuals are complex and variable mixtures, and animals perceive information based on variation in the overall quality of these mixtures. A variety of compounds potentially involved in chemical communication have been characterized in the urine of different felid species, but little is known about the information content of felid scent marks. In this study, we investigated whether chemical composition of Eurasian lynx Lynx lynx urine was related to sex, reproductive state, and individual identity. We further analysed if elemental sulphur in lynx urine could serve as a dietary cue or as an indicator for the freshness of a scent mark. We collected urine from captive and wild Eurasian lynx, and analysed volatile constituents of urine by means of solid phase microextraction and gas chromatography-mass spectrometry. Our results show that lynx scent profiles contain sex-specific information on reproductive state, as well as individual identity cues. Urine marks are, therefore, well-suited to fulfil a role in reproductive behaviour and social organisation of wild lynx populations. Relative sulphur content was unrelated to time since last feeding, but decreased with age of the urine sample. The influence of diet and body condition on scent profiles should be further investigated by means of experimental studies, and may shed more light on the messages encoded in carnivore scent-marks. 相似文献
753.
754.
755.
Molecular phylogeny and DNA barcoding of tropical eastern Pacific shallow-water gorgonian octocorals
The octocoral fauna inhabiting the shallow waters (<50 m) of the eastern Pacific has been the subject of renewed interest, and the taxonomy of the most important genera in the region has been reviewed and clarified. Many new species have been described, significantly increasing the known biological diversity of the region. Despite their importance as potential sister-groups of Caribbean octocorals, the phylogenetic relationships of eastern Pacific octocorals remain poorly studied. Here, using partial mitochondrial MutS and igr1-COI sequences, we provide a phylogenetic assessment of a broad sample of eastern Pacific shallow-water octocorals and investigate their phylogenetic relationships with Caribbean gorgonians. We corroborate the monophyly of Pacifigorgia, Leptogorgia and Eugorgia and provide evidence of a close relationship between Swiftia and Psammogorgia, currently placed in Plexauridae. In addition, the phylogenies obtained here provide insights into the historical biogeography and phylogenetic diversity of the eastern Pacific octocoral assemblages and on character evolution among this diverse faunal assemblage. Finally, we evaluate the classification power of DNA barcoding for identifying species of shallow-water eastern Pacific octocorals and assess the use of a nuclear intron (SRP54) to supplement traditional mitochondrial barcodes in this group of organisms. 相似文献
756.
Beatriz Willink Federico Bolaños Heike Pröhl 《Behavioral ecology and sociobiology》2014,68(2):249-261
The evolution of aposematism is linked to increased opportunities for conspicuous sexual displays since detection by potential predators is no longer disadvantageous. Therefore, phenotypic divergence in aposematic species leading to relatively cryptic forms is expected to constrain such opportunities, by restoring the trade-off between natural and sexual selection on the boldness of sexual displays. We asked if and how a derived phenotype of the poison-dart frog Oophaga granulifera that appears relatively cryptic to potential predators exhibits conspicuous sexual displays for potential mates. We used visual modeling of frog contrasts against their natural backgrounds to test if for conspecifics green frogs appear less conspicuous than red frogs as they do for birds. We conducted behavioral observations of focal red and green males to determine if green frogs adjust their display behavior to the availability of potential mates. Dorsal brightness is known to influence female preferences in at least one poison frog species. We found that, despite being less visible under some measures, green frogs may appear as bright as red frogs for conspecifics but not birds, when viewed on dark backgrounds. Additionally, green males called more intermittently than red males when advertising to distant females, but they exhibited a dramatic increase in calling activity in proximity of a female and were as active as red males in this context. Together, our results suggest that green frogs retain context-dependent conspicuousness to conspecifics despite the evolution of relative crypsis to potential predators. 相似文献
757.
Three populations of the grazing isopod Idotea balthica were exposed to high CO2 treatment for a period of 20 days to investigate the effect of ocean acidification (OA) on animal health and immunocompetence. The results of the populations from more saline habitats were comparable and showed a 60–80 % decrease in immune response as a result of the high CO2 treatment. Analysis of protein carbonyls showed no treatment effect, indicating that short-term OA does not increase oxidative protein damage. Meanwhile, the third tested population from the lower saline Baltic Sea had higher background protein carbonyl levels. Ocean acidification in addition to this resulted in 100 % mortality. The results of this study show that OA reduced immunocompetence of this marine isopod. In addition, populations and individuals in poor health are potentially at greater risk to succumb under OA. 相似文献
758.
The fatty acid (FA) composition was determined in 14 species of marine macroalgae belonging to the Chlorophyta, Phaeophyta and Rhodophyta, which were collected from ?ile in the Black Sea and Kepez in the Dardanelles. Generally, polyunsaturated FAs and monounsaturated FAs were major components (50–77%). Total saturated FAs ranged from 22% to 50%, with 16?:?0 as the most abundant saturate (32–38%). Two samples of Cystoseira barbata collected from a different station had some differences from each other in their contents of 18?:?2n-6 and 18?:?3n-3 and in the 18?:?2n-6/20?:?4n-6 ratios. Green algal species had a significantly higher proportion of unsaturated FAs and a significantly lower proportion of saturated FAs than the red and brown algae. The amount of n-3 FAs was significantly higher in Ulva rigita, Chaetomorpha linum, Enteromorpha linza and Gracilaria verrucosa (8.88, 6.44, 5.31 and 5.24, respectively). 相似文献
759.
Dr. V. Ladewig D. Jungmann H.-R. Köhler O. Licht K.-U. Ludwichowski M. Schirling 《毒物与环境化学》2013,95(4):649-664
The impact of bisphenol A (BPA) on Gammarus fossarum and Lumbriculus variegatus was studied in four artificial indoor streams (0, 5, 50 and 500?µg?L?1 BPA, nominal) over 103 days in a pulse–dose exposure scenario (weekly BPA application). For G. fossarum populations at day 103, the proportions of juveniles and of breeding females from the highest BPA treatment were in tendency reduced. For individually exposed gammarid pairs an EC10 of 17?µg?L?1 BPA (nominal) for the proportion of reproductive females in the fourth brood was determined. During the first three broods, the largest brood size occurred at the highest BPA concentration, whereas in the fourth brood it decreased concentration-dependently (fourth brood EC10?=?5?µg?L?1 BPA, nominal). Effects on L. variegatus were a reduced population growth (103?d-EC10 of 2?µg?L?1 BPA, nominal) and an increase in dry weight and the number of segments in large, complete worms. 相似文献
760.
Pesticides are chemicals used in agriculture but are known to produce adverse effects on humans. In this study, blood activities of superoxide dismutase (SOD), catalase (CAT), aspartate transaminase (AST), alanine transaminase (ALT), gamma-glutamyl transaminase, lactate dehydrogenase (LDH), and levels of malondialdhyde (MDA) were determined in 44 greenhouse workers (24 tomato workers, 20 clove workers) and in tomato (24 samples) and clove (20 samples) products. At the end of this study, blood MDA levels and activities of ALT, AST, and LDH levels in greenhouse workers were significantly increased while SOD and CAT activity levels fell significantly. Pesticide residues were not found in agricultural worker blood. Malathion residues (average 0.8?ppm) were detected in tomatoes (8 samples) in these greenhouses. Data suggest that the health of the greenhouse workers may be adversely affected by pesticides. 相似文献