全文获取类型
收费全文 | 31129篇 |
免费 | 285篇 |
国内免费 | 273篇 |
专业分类
安全科学 | 821篇 |
废物处理 | 1366篇 |
环保管理 | 3879篇 |
综合类 | 5018篇 |
基础理论 | 8051篇 |
环境理论 | 18篇 |
污染及防治 | 8183篇 |
评价与监测 | 2231篇 |
社会与环境 | 1921篇 |
灾害及防治 | 199篇 |
出版年
2022年 | 282篇 |
2021年 | 298篇 |
2020年 | 212篇 |
2019年 | 262篇 |
2018年 | 480篇 |
2017年 | 466篇 |
2016年 | 740篇 |
2015年 | 547篇 |
2014年 | 798篇 |
2013年 | 2514篇 |
2012年 | 975篇 |
2011年 | 1303篇 |
2010年 | 1153篇 |
2009年 | 1186篇 |
2008年 | 1358篇 |
2007年 | 1430篇 |
2006年 | 1255篇 |
2005年 | 1080篇 |
2004年 | 996篇 |
2003年 | 1028篇 |
2002年 | 963篇 |
2001年 | 1304篇 |
2000年 | 895篇 |
1999年 | 571篇 |
1998年 | 390篇 |
1997年 | 386篇 |
1996年 | 425篇 |
1995年 | 441篇 |
1994年 | 438篇 |
1993年 | 377篇 |
1992年 | 355篇 |
1991年 | 359篇 |
1990年 | 351篇 |
1989年 | 363篇 |
1988年 | 298篇 |
1987年 | 264篇 |
1986年 | 237篇 |
1985年 | 221篇 |
1984年 | 275篇 |
1983年 | 250篇 |
1982年 | 299篇 |
1981年 | 240篇 |
1980年 | 208篇 |
1979年 | 256篇 |
1978年 | 185篇 |
1977年 | 172篇 |
1976年 | 159篇 |
1975年 | 161篇 |
1974年 | 147篇 |
1973年 | 144篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Sam M. Jones Jelle S. van Zweden Christoph Grüter Cristiano Menezes Denise A. Alves Patrícia Nunes-Silva Tomer Czaczkes Vera L. Imperatriz-Fonseca Francis L. W. Ratnieks 《Behavioral ecology and sociobiology》2012,66(1):1-12
Recent research has shown that entrance guards of the stingless bee Tetragonisca angustula make less errors in distinguishing nestmates from non-nestmates than all other bee species studied to date, but how they
achieve this is unknown. We performed four experiments to investigate nestmate recognition by entrance guards in T. angustula. We first investigated the effect of colony odours on acceptance. Nestmates that acquired odour from non-nestmate workers
were 63% more likely to be rejected while the acceptance rate of non-nestmates treated with nestmate odour increased by only
7%. We further hypothesised that guards standing on the wax entrance tube might use the tube as an odour referent. However,
our findings showed that there was no difference in the acceptance of non-nestmates by guards standing on their own colony’s
entrance tube versus the non-nestmate’s entrance tube. Moreover, treatment of bees with nestmate and non-nestmate resin or
wax had a negative effect on acceptance rates of up to 65%, regardless of the origin of the wax or resin. The role of resin
as a source of recognition cues was further investigated by unidirectionally transferring resin stores between colonies. Acceptance
rates of nestmates declined by 37% for hives that donated resin, contrasting with resin donor hives where acceptance of non-nestmates
increased by 21%. Overall, our results confirm the accuracy of nestmate recognition in T. angustula and reject the hypothesis that this high level of accuracy is due to the use of the wax entrance tubes as a referent for
colony odour. Our findings also suggest that odours directly acquired from resin serve no primary function as nestmate recognition
cues. The lack of consistency among colonies plus the complex results of the third and fourth experiments highlight the need
for further research on the role of nest materials and cuticular profiles in understanding nestmate recognition in T. angustula. 相似文献
992.
Jennifer M. Duringer Laurence R. Swan Douglas B. Walker A. Morrie Craig 《Environmental monitoring and assessment》2010,170(1-4):585-598
Recently, interest has developed for using essential oils from Western juniper (Juniperus occidentalis) foliage and Port Orford cedar (Chamaecyparis lawsoniana) heartwood in commercial products such as pest repellents and cosmetics. In order to gauge the relative toxicological risk that these oils pose to freshwater and marine organisms, the acute aquatic toxicity of these oils was evaluated using OPPTS guidelines to the cladoceran Daphnia magna, the rainbow trout Oncorhynchus mykiss and the green alga Selenastrum capricornutum. For western juniper foliage oil, no toxicity was exhibited toward D. magna or O. mykiss, even at 5.0 mg/L (the highest concentration tested and limit of solubility). For toxicity to S. capricornutum using algal cell density, the 72 and 96 h EC50 value was 1.7 mg/L and the no observable effect concentration (NOEC) was 0.63 mg/L. For Port Orford cedar heartwood oil, no toxicity was exhibited toward O. mykiss or S. capricornutum, even at 5.0 mg/L (the highest concentration tested and limit of solubility). The 48-h D. magna EC50 value was 1.9 mg/L; the NOEC values for algal cell density were 1.25 mg/L (72 h) and 0.63 mg/L (96 h). In summary, this study shows that western juniper foliage and Port Orford cedar heartwood oils demonstrate little to no risk to aquatic organisms. 相似文献
993.
994.
Miriam Hampel Esteban Alonso Irene Aparicio James E. Bron Juan Luis Santos John B. Taggart Michael J. Leaver 《Environmental science and pollution research international》2010,17(4):917-933
Background, aim, and scope
Pharmaceuticals are emerging pollutants widely used in everyday urban activities which can be detected in surface, ground, and drinking waters. Their presence is derived from consumption of medicines, disposal of expired medications, release of treated and untreated urban effluents, and from the pharmaceutical industry. Their growing use has become an alarming environmental problem which potentially will become dangerous in the future. However, there is still a lack of knowledge about long-term effects in non-target organisms as well as for human health. Toxicity testing has indicated a relatively low acute toxicity to fish species, but no information is available on possible sublethal effects. This study provides data on the physiological pathways involved in the exposure of Atlantic salmon as representative test species to three pharmaceutical compounds found in ground, surface, and drinking waters based on the evaluation of the xenobiotic-induced impairment resulting in the activation and silencing of specific genes. 相似文献995.
Recent studies have reported an increasing trend of mercury concentrations in walleye (Sander vitreus) from the Athabasca River, north eastern Alberta (Canada); these studies were based on three years of comparison and attributed the mercury increase to expanding oil sands developments in the region. In order to conduct a more comprehensive analysis of mercury trends in fish, we compiled an extensive database for walleye, lake whitefish (Coregonus clupeaformis), northern pike (Esox lucius) and lake trout (Salvelinus namaycush) using all available data obtained from provincial, federal, and industry-funded monitoring and other programs. Evidence for increasing trends in mercury concentrations were examined for each species by location and year also considering fish weight and length. In the immediate oil sands area of the Athabasca River, mercury concentrations decreased (p < 0.001) in walleye and lake whitefish over 1984-2011. In western Lake Athabasca and its delta, mercury concentrations decreased (p < 0.0001) in northern pike (1981-2009) although no trend was evident for walleye (1981-2005) and lake trout (1978-2009). Mercury concentrations in lake trout from Namur Lake, a small lake west of the oil sands area, were higher in 2007 than 2000 (p < 0.0001); it is difficult to ascribe this increase to an oil sands impact because similar increases in mercury concentrations have been observed in lake trout from similar sized lakes in the Northwest Territories. While mercury emissions rates have increased with oil sands development and the landscape become more disturbed, mercury concentrations remained low in water and sediments in the Athabasca River and its tributaries and similar to concentrations observed outside the development areas and in earlier decades. Our fish database was assembled from a series of studies that differed in study purpose, design, and analytical methods. Future monitoring programs investigating mercury trends in fish should be more rigorous in their design. 相似文献
996.
Correlations in polycyclic aromatic hydrocarbon (PAH) concentrations in UK ambient air and implications for source apportionment 总被引:3,自引:0,他引:3
The extent of correlation in polycyclic aromatic hydrocarbon (PAH) concentration data obtained by the UK PAH Monitoring and Analysis Air Quality Network from March 2008 to November 2010 has been assessed. Application of principal component analysis (PCA) to the dataset has revealed that the concentrations of the vast majority of PAHs are very highly correlated. The use of diagnostic PAH ratios (including a new benzo[b]naph[2,1-d]thiophene/benzo[a]pyrene diagnostic ratio), and a novel 'combined diagnostic ratio - PCA' approach has revealed information about the main sources of PAH at individual Network sites, allowing the sites to be grouped in terms of those influenced by solid fuel use, industry and traffic, and those of an urban or rural nature. Solid fuel use has also been delineated from other fuel burning. Conclusions are drawn about a number of UK PAH Network sites - four sites are shown to be influenced significantly by solid fuel use, and the sites in South Wales and at London Marylebone Road are found to be located in distinct and unusual PAH pollution climates - the identification of a unique PAH pollution climate in South Wales is a key and novel conclusion of the work. 相似文献
997.
Poly-β-hydroxybuyrate (PHB) is a carbon—energy storage material which is accumulated as intracellular granule in variety of
microorganism under nutrient starved conditions. Solid PHB is a biodegradable thermoplastic polymer and is utilizable in various
ways similar to many conventional plastics. Ralstonia eutropha (Alcaligenes sp.), a gram negative bacteria accumulates PHB as insoluble granules inside the cells when nutrients other than carbon are
limited. In this report effort has been made to analyze PHB granule synthesis inside Alcaligenes sp. NCIM 5085 by transmission electron microscopy and qualitative estimation of PHB was carried out by fourier transform
infrared spectroscopy which provide better precision compared to other conventional techniques previously applied for PHB
determination. Maximum PHB concentration of 2.20 ± 0.40 g/L and cell biomass of 3.42 ± 0.20 g/L was obtained after 48.0 h
of fermentation. Leudking-Piret equation deduced mixed growth associated product formation which varies from earlier reports. 相似文献
998.
N. Mithil Kumar K. Varaprasad G. Ramachandra Reddy G. Siva Mohan Reddy Y. Sivabharathi G. Venkata Subba Reddy S. Venkata Naidu 《Journal of Polymers and the Environment》2011,19(1):225-229
Synthesis and characterization of novel biodegradable, water soluble and optically active DL-malic acid (DMA) and citric acid
(CA) copolymers were studied for possible use as antibacterial agents. The copolymers were synthesized by direct bulk melt
condensation in the absence of a catalyst above 150 °C. Characterization of obtained copolymers was carried out with the help
of infrared absorption spectra, differential scanning calorimetry and thermo gravimetric analysis. The antibacterial activity
of copolymers against bacteria was investigated. The results obtained shows the above copolymers possess a broad wound dressing
activity against different types of bacteria and may be useful as antibacterial agents. 相似文献
999.
M. Jawaid H. P. S. Abdul Khalil P. Noorunnisa Khanam A. Abu Bakar 《Journal of Polymers and the Environment》2011,19(1):106-109
In this research, hybrid composite materials were prepared from combination of oil palm Empty fruit bunches (EFB) fibre and
jute fibre as reinforcement, epoxy as polymer matrix. This study intended to investigate the effect of jute fiber hybridization
and different layering pattern on the physical properties of oil palm EFB-Epoxy composites. Water absorption and thickness
swelling test reveal that hybrid composite shows a moderate water absorption which is 11.20% for hybrid EFB/Jute/EFB composite
and 6.08% for hybrid Jute/EFB/Jute composite. The thickness swelling and water absorption of the hybrid composites slightly
increased as the layering pattern of hybrid composites changed. Hybrid composites are more water resistance and dimensional
stable compare to the pure EFB composites. This is attributed to the more hydrophilic nature of EFB composites. Hybridization
of oil palm EFB composites with jute fibres can improve the dimensional stability and density of pure EFB and Jute fibre reinforced
composites has higher density of 1.2 g/cm3 compared to all other composites. 相似文献
1000.
Aarin Teague Philip B. Bedient Birnur Guven 《Journal of the American Water Resources Association》2011,47(3):620-634
Teague, Aarin, Philip B. Bedient, and Birnur Guven, 2011. Targeted Application of Seasonal Load Duration Curves Using Multivariate Analysis in Two Watersheds Flowing Into Lake Houston. Journal of the American Water Resources Association (JAWRA) 47(3):620‐634. DOI: 10.1111/j.1752‐1688.2011.00529.x Abstract: Water quality is a problem in Lake Houston, the primary source of drinking water for the City of Houston, Texas, due to pollutant loads coming from the influent watersheds, including Spring Creek and Cypress Creek. Statistical analysis of the historic water quality data was developed to understand the source characterization and seasonality of the watershed. Multivariate analysis including principal component, cluster, and discriminant analysis provided a custom seasonal assessment of the watersheds so that loading curves may be targeted for season specific pollutant source characterization. The load duration curves have been analyzed using data collected by the U.S. Geologic Survey with corresponding City of Houston water quality data at the sites to characterize the behavior of the pollutant sources and watersheds. Custom seasons were determined for Spring Creek and Cypress Creek watersheds and pollutant source characterization compared between the seasons and watersheds. 相似文献