全文获取类型
收费全文 | 1919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 | 327篇 |
污染及防治 | 633篇 |
评价与监测 | 189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 | 66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 | 95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 | 90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1969条查询结果,搜索用时 46 毫秒
861.
862.
863.
Rodolfo Jaffé Fabiana C. Pioker-Hara Charles F. dos Santos Leandro R. Santiago Denise A. Alves Astrid de M. P. Kleinert Tiago M. Francoy Maria C. Arias Vera L. Imperatriz-Fonseca 《Die Naturwissenschaften》2014,101(3):261-264
High genetic diversity is important for the functioning of large insect societies. Across the social Hymenoptera (ants, bees, and wasps), species with the largest colonies tend to have a high colony-level genetic diversity resulting from multiple queens (polygyny) or queens that mate with multiple males (polyandry). Here we studied the genetic structure of Trigona spinipes, a stingless bee species with colonies an order of magnitude larger than those of polyandrous honeybees. Genotypes of adult workers and pupae from 43 nests distributed across three Brazilian biomes showed that T. spinipes colonies are usually headed by one singly mated queen. Apart from revealing a notable exception from the general incidence of high genetic diversity in large insect societies, our results reinforce previous findings suggesting the absence of polyandry in stingless bees and provide evidence against the sperm limitation hypothesis for the evolution of polyandry. Stingless bee species with large colonies, such as T. spinipes, thus seem promising study models to unravel alternative mechanisms to increase genetic diversity within colonies or understand the adaptive value of low genetic diversity in large insect societies. 相似文献
864.
Susana Garrido Rui Rosa Radhouan Ben-Hamadou Maria Emilia Cunha Maria Alexandra Chícharo Carl D. van der Lingen 《Marine Biology》2008,154(6):1053-1065
Temporal variation in the fatty acid (FA) composition of stomach contents of Iberian sardines was compared to the relative
contribution to dietary carbon made by different prey types for fish from two areas off Portugal. The effect of the FA content
of the diet on sardine muscle FA composition was also studied, aiming at (1) analysing if FA biomarkers can be used as a complementary
technique for the study of sardine diet and (2) to relate spatial and temporal variations of prey FA content with sardine
condition and reproduction. Significant spatial differences in the FA composition of sardine diet occurred with concentrations
of n-3 polyunsaturated FA, namely eicosapentaenoic acid [EPA, 20:5n-3] and linolenic acid 18:3n-3, being significantly higher
in the diet of sardines from the west coast, whilst the diet of sardines from the south coast was richer in monounsaturated
fatty acids (MUFA), namely the carnivory biomarker oleic acid 18:1n-9. These results are in agreement with the higher contribution
made by diatoms and dinoflagellates to the diet of sardines off the west coast. Spatial variation in sardine dietary FA was
also detected in their muscle composition, specifically for EPA, and the eicosapentaenoic/docosahexaenoic acid and (n-3)/(n-6)
ratios, which were higher in sardines from the west coast. No difference in FA composition was detected between sexes, and
the seasonal variability in sardine total FA concentration was primarily related to the seasonality of spawning. Sardines
accumulate high concentrations of FAs during the resting stage of reproduction when the feeding intensity is similar or lower
to that observed during the spawning season. Additionally, sardines show a high selective retention of MUFA and polyunsaturated
FA (PUFA) throughout the year except at the beginning of the spawning season, when these FAs are largely invested in the formation
of the gonads. Therefore, temporal and regional differences of prey environments are strong enough to be reflected in fish
body composition, namely on the accumulation of essential FAs, which can have a strong impact on reproduction success for
this species. 相似文献
865.
Donatella Desideri Maria Assunta Meli Carla Roselli 《Journal of environmental radioactivity》2010,101(9):751-756
Several medicinal plants used in Italy were analysed to determine natural and artificial radioactivity in those parts (leaves, fruits, seeds, roots, peduncles, flowers, barks, berries, thallus) used generally as remedies. The radionuclides were determined by alpha (238U, 210Po) and gamma (214Pb-Bi, 210Pb, 40K and 137Cs) spectrometry. 238U ranged between <0.1 and 7.32 Bq kgdry−1; 210Po between <0.1 and 30.3 Bq kgdry−1; 214Pb-214Bi between <0.3 and 16.6 Bq kgdry−1; 210Pb between <3 and 58.3 Bq kgdry−1; 40K between 66.2 and 3582.0 Bq kgdry−1; 137Cs between <0.3 and 10.7 Bq kgdry−1. The percentage of 210Po extraction in infusion and decoction was also determined; the arithmetical mean value of percentage of 210Po extraction resulted 20.7 ± 7.5. 相似文献
866.
Holger Gulyas Pawel Choromanski Nils Muelling Maria Furmanska 《Journal of Cleaner Production》2009,17(13):1223-1227
Heterogeneous photocatalytic oxidation is a water reclamation technology which avoids chemical consumption and can be powered by solar radiation. Because this generally sustainable process is of limited efficiency for the treatment of biologically pretreated greywater, it was combined with activated carbon adsorption. The effluent of a constructed wetland for treatment of separately collected greywater was subjected to photocatalytic oxidation using the photocatalyst titanium dioxide (TiO2) “P25” in both the absence and the presence of powdered activated carbon (PAC). Photocatalytic oxidation alone with UV fluences of about 10 Wh L?1 was not capable of reducing total organic carbon (TOC) from an initial concentration of 5.5 mg L?1 safely below 2 mg L?1 as a prerequisite for high-quality water reuse purposes. However, when PAC was added, TOC concentrations subsequent to photocatalytic oxidation were less than 2 mg L?1 even after reusing the TiO2/PAC mixture 10 times. PAC addition is estimated to reduce the insolation area necessary to achieve this target by solar photocatalytic oxidation of biologically treated greywater by a factor 7. This combination process represents an innovative chemical-free technology within wastewater reuse schemes. 相似文献
867.
868.
869.