全文获取类型
收费全文 | 252878篇 |
免费 | 15969篇 |
国内免费 | 39815篇 |
专业分类
安全科学 | 23491篇 |
废物处理 | 11587篇 |
环保管理 | 28981篇 |
综合类 | 104019篇 |
基础理论 | 47572篇 |
环境理论 | 211篇 |
污染及防治 | 54379篇 |
评价与监测 | 16539篇 |
社会与环境 | 14914篇 |
灾害及防治 | 6969篇 |
出版年
2024年 | 850篇 |
2023年 | 3954篇 |
2022年 | 9430篇 |
2021年 | 9467篇 |
2020年 | 8914篇 |
2019年 | 7121篇 |
2018年 | 8322篇 |
2017年 | 10088篇 |
2016年 | 10209篇 |
2015年 | 9641篇 |
2014年 | 11387篇 |
2013年 | 20967篇 |
2012年 | 16160篇 |
2011年 | 18029篇 |
2010年 | 15770篇 |
2009年 | 15536篇 |
2008年 | 15918篇 |
2007年 | 15620篇 |
2006年 | 14538篇 |
2005年 | 11255篇 |
2004年 | 8656篇 |
2003年 | 7643篇 |
2002年 | 6751篇 |
2001年 | 6165篇 |
2000年 | 5239篇 |
1999年 | 3576篇 |
1998年 | 2400篇 |
1997年 | 2186篇 |
1996年 | 2210篇 |
1995年 | 2291篇 |
1994年 | 2025篇 |
1993年 | 1491篇 |
1992年 | 1504篇 |
1991年 | 1364篇 |
1990年 | 1251篇 |
1989年 | 1145篇 |
1988年 | 1013篇 |
1987年 | 906篇 |
1986年 | 859篇 |
1985年 | 870篇 |
1984年 | 895篇 |
1983年 | 824篇 |
1982年 | 918篇 |
1981年 | 818篇 |
1980年 | 627篇 |
1979年 | 686篇 |
1978年 | 585篇 |
1977年 | 513篇 |
1975年 | 467篇 |
1974年 | 461篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
JHERIME L. KELLERMANN MATTHEW D. JOHNSON AMY M. STERCHO STEVEN C. HACKETT 《Conservation biology》2008,22(5):1177-1185
Abstract: Coffee farms can support significant biodiversity, yet intensification of farming practices is degrading agricultural habitats and compromising ecosystem services such as biological pest control. The coffee berry borer (Hypothenemus hampei) is the world's primary coffee pest. Researchers have demonstrated that birds reduce insect abundance on coffee farms but have not documented avian control of the berry borer or quantified avian benefits to crop yield or farm income. We conducted a bird‐exclosure experiment on coffee farms in the Blue Mountains, Jamaica, to measure avian pest control of berry borers, identify potential predator species, associate predator abundance and borer reductions with vegetation complexity, and quantify resulting increases in coffee yield. Coffee plants excluded from foraging birds had significantly higher borer infestation, more borer broods, and greater berry damage than control plants. We identified 17 potential predator species (73% were wintering Neotropical migrants), and 3 primary species composed 67% of migrant detections. Average relative bird abundance and diversity and relative resident predator abundance increased with greater shade‐tree cover. Although migrant predators overall did not respond to vegetation complexity variables, the 3 primary species increased with proximity to noncoffee habitat patches. Lower infestation on control plants was correlated with higher total bird abundance, but not with predator abundance or vegetation complexity. Infestation of fruit was 1–14% lower on control plants, resulting in a greater quantity of saleable fruits that had a market value of US$44–$105/ha in 2005/2006. Landscape heterogeneity in this region may allow mobile predators to provide pest control broadly, despite localized farming intensities. These results provide the first evidence that birds control coffee berry borers and thus increase coffee yield and farm income, a potentially important conservation incentive for producers. 相似文献
32.
33.
34.
Rocío Mariano-Jelicich Florencia Botto Paulina Martinetto Oscar Iribarne Marco Favero 《Marine Biology》2008,155(4):443-450
The degree of individual or gender variation when exploiting food resources is an important aspect in the study of foraging
ecology within a population. Previous information on non-breeding skimmers obtained through conventional methodologies suggested
sex-related differences in prey species. In this study, stable isotope techniques were used to investigate the intraspecific
segregation in diet and foraging habits of the Black Skimmer (Rynchops niger intercedens) at Mar Chiquita Coastal Lagoon (37°40′S, 57°22′W), Argentina. These results were compared with contemporary data on the
trophic composition obtained by conventional methodologies. Blood samples were taken from birds captured with mist-nets during
their non-breeding season. The isotopic signatures of skimmers showed a diet mainly composed of marine prey with some degree
of estuarine fish intake. When comparing diet between sexes, males showed enrichment in 15N compared to females, while no differences were observed in 13C. The use of mixing models revealed differences in the relative composition of prey in the diet of male and female skimmers.
This study highlights stable isotope analysis as a valuable tool to test inter-individual differences and sexual segregation
in trophic ecology of Black Skimmers as compared to conventional methodologies. The results show a trophic segregation in
the Black Skimmer during the non-breeding season that can be explained by differences in prey species and larger prey sizes
of male skimmers. Our findings have significant implications for conservation since any environmental change occurring at
wintering areas might have profound effects on several avian life-history traits, and could be different for males and females
due to trophic segregation. 相似文献
35.
36.
37.
38.
E Enan I G Berberian S el-Fiki M el-Masry O H Enan 《Journal of environmental science and health. Part. B》1987,22(2):149-170
Male Baladi rabbits were acutely and sub-chronically intoxicated with cyanofenphos and profenophos. The levels of cholesterol, triglycerides, B-lipoproteins and total proteins were determined in the serum, brain, spinal cord and sciatic nerve of rabbits. Moreover, the activities of alkaline phosphatase, acid phosphatase and glutamic-pyruvic transaminase were determined in the liver of the animals. The whole studies revealed that the biochemical constituents were highly affected by the tested insecticides. Also, the liver function suffered from adverse effects of the tested insecticides. 相似文献
39.
Daniel H Zitomer Prasoon Adhikari Craig Heisel Dennis Dineen 《Water environment research》2008,80(3):229-237
Codigestion of five wastes and municipal wastewater sludge was evaluated using full-scale testing. Synergistic, antagonistic, and neutral outcomes were observed depending on codigestate identity and concentration, highlighting the value of careful blending. Yeast waste resulted in notable synergism, increasing biogas production by over 50%, whereas aircraft deicing waste resulted in antagonism at high loadings and neutral outcomes at lower loadings. Restaurant waste codigestion resulted in neutral outcomes. The synergisim with yeast codigestates may have resulted from trace nutrients (i.e., iron, nickel, and cobalt) in the wastes that increased microbiological activity. Antagonist outcomes with deicing waste may have been the result of organic overload or inhibitory deicer constituents. Codigestion of wastes at the feed rates investigated was estimated to produce 0.50 ML/d of methane having an energy equivalent of 17 500 MJ/d. This was estimated to reduce net carbon dioxide emissions by 560 tonnes/y. 相似文献
40.
Matthew Bates Paolo Bruno Mariangela Caputi Maurizio Caselli Gianluigi de Gennaro Maria Tutino 《Atmospheric environment (Oxford, England : 1994)》2008,42(24):6144-6151
The technique of thermal desorption (TD)–GC/MS was evaluated for measuring airborne, 4–6 ring polycyclic aromatic hydrocarbons (PAHs) collected onto quartz filters. TD provides a more readily automated and sensitive alternative to traditional solvent extraction, decreasing the time/cost of analysis and reducing the risk of analyte loss or sample contamination. The developed method was successfully applied to the analysis of PAH standard solutions loaded on sorbent tubes packed with quartz wool and the graphitized carbon black sorbent Carbograph2. The optimized method showed high desorption efficiency over the whole range of target PAHs with good precision, linearity and sensitivity. The proposed method was verified on an urban dust Standard Reference Material (SRM 1649a); the experimentally determined concentrations agreed with the certified ranges (95% confidence limit) for all target compounds except benzo[a]anthracene, which fell just outside the narrow certified range. The desorption efficiency and the reproducibility of the method was evaluated by analysing pieces of real sample filters sampled from urban air for a period of 24 h. The results confirmed the homogeneity of the filter and showed high recovery efficiencies for all target PAHs. 相似文献