全文获取类型
收费全文 | 17845篇 |
免费 | 174篇 |
国内免费 | 156篇 |
专业分类
安全科学 | 441篇 |
废物处理 | 785篇 |
环保管理 | 2028篇 |
综合类 | 2946篇 |
基础理论 | 4781篇 |
环境理论 | 6篇 |
污染及防治 | 4687篇 |
评价与监测 | 1274篇 |
社会与环境 | 1115篇 |
灾害及防治 | 112篇 |
出版年
2022年 | 202篇 |
2021年 | 198篇 |
2020年 | 146篇 |
2019年 | 143篇 |
2018年 | 285篇 |
2017年 | 318篇 |
2016年 | 435篇 |
2015年 | 332篇 |
2014年 | 544篇 |
2013年 | 1344篇 |
2012年 | 601篇 |
2011年 | 826篇 |
2010年 | 709篇 |
2009年 | 672篇 |
2008年 | 764篇 |
2007年 | 806篇 |
2006年 | 654篇 |
2005年 | 615篇 |
2004年 | 666篇 |
2003年 | 643篇 |
2002年 | 573篇 |
2001年 | 704篇 |
2000年 | 500篇 |
1999年 | 283篇 |
1998年 | 187篇 |
1997年 | 226篇 |
1996年 | 217篇 |
1995年 | 251篇 |
1994年 | 246篇 |
1993年 | 188篇 |
1992年 | 205篇 |
1991年 | 195篇 |
1990年 | 209篇 |
1989年 | 195篇 |
1988年 | 155篇 |
1987年 | 168篇 |
1986年 | 159篇 |
1985年 | 161篇 |
1984年 | 157篇 |
1983年 | 150篇 |
1982年 | 130篇 |
1981年 | 126篇 |
1980年 | 116篇 |
1979年 | 132篇 |
1978年 | 102篇 |
1977年 | 116篇 |
1975年 | 90篇 |
1974年 | 88篇 |
1973年 | 96篇 |
1972年 | 86篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Abstract: Because ambient temperature strongly influences reproduction in frogs, the seasonal timing of frog calling provides a sensitive index of biotic response to climate change. Over the last century, daily temperatures increased during 5 of the 8 months key to gametogenesis in frogs and toads near Ithaca, New York ( U.S.A.). Earliest dates of calling frogs recorded by Albert Hazen Wright between 1900 and 1912 near Ithaca were compared to those from the New York State Amphibian and Reptile Atlas Project for 1990–1999 for the three counties surrounding Ithaca. Four species are now calling 10–13 days earlier, two are unchanged, and none is calling later. The data suggest that climate has warmed in central New York State during this century and has resulted in earlier breeding in some amphibians—a possible first indication of biotic response to climate change in eastern North America. 相似文献
992.
Honey-bee (Apis mellifera) colonies exhibit extreme reproductive division of labour. Workers almost always have inactive ovaries and the queen monopolises
egg laying. Although extremely rare, ’anarchistic’ colonies exist in which workers produce male offspring despite the presence
of the queen. By comparing the rates of ovary activation in anarchistic and wild-type bees fostered to host colonies of different
genotype (i.e. anarchist and non-anarchist) and queen status (i.e. queenless and queenright), we investigated the factors
involved in inhibiting ovary activation. Fostered anarchist workers always had a higher level of ovary development than fostered
wild-type bees in both anarchist and non-anarchist host colonies. Fostered workers of both genotypes had more active ovaries
in anarchistic than in wild-type hosts. Fostered workers of both strains also had more active ovaries in queenless than in
queenright hosts. The results suggest that selection for worker reproduction in the anarchistic line has both reduced the
effects of brood and queen pheromones on worker ovary inhibition and increased the likelihood that workers of the anarchistic
line will develop ovaries compared to wild-type workers.
Received: 14 June 2000 / Revised: 26 September 2000 / Accepted: 7 October 2000 相似文献
993.
D. Eskinazi J. E. Cichanowicz W. P. Linak R. E. Hall 《Journal of the Air & Waste Management Association (1995)》2013,63(8):1131-1139
This paper summarizes information and results presented at the 1989 Symposium on Stationary Combustion NOX Control, held March 6-9, 1989 in San Francisco. Cosponsored by the Electric Power Research Institute (EPRI) and the U.S. Environmental Protection Agency, (EPA) the symposium was the fifth in a biennial series. 相似文献
994.
P. Kaniewska K. R. N. Anthony E. M. Sampayo P. R. Campbell O. Hoegh-Guldberg 《Marine Biology》2014,161(2):313-328
Reef-building corals are an example of plastic photosynthetic organisms that occupy environments of high spatiotemporal variations in incident irradiance. Many phototrophs use a range of photoacclimatory mechanisms to optimize light levels reaching the photosynthetic units within the cells. In this study, we set out to determine whether phenotypic plasticity in branching corals across light habitats optimizes potential light utilization and photosynthesis. In order to do this, we mapped incident light levels across coral surfaces in branching corals and measured the photosynthetic capacity across various within-colony surfaces. Based on the field data and modelled frequency distribution of within-colony surface light levels, our results show that branching corals are substantially self-shaded at both 5 and 18 m, and the modal light level for the within-colony surface is 50 μmol photons m?2 s?1. Light profiles across different locations showed that the lowest attenuation at both depths was found on the inner surface of the outermost branches, while the most self-shading surface was on the bottom side of these branches. In contrast, vertically extended branches in the central part of the colony showed no differences between the sides of branches. The photosynthetic activity at these coral surfaces confirmed that the outermost branches had the greatest change in sun- and shade-adapted surfaces; the inner surfaces had a 50 % greater relative maximum electron transport rate compared to the outer side of the outermost branches. This was further confirmed by sensitivity analysis, showing that branch position was the most influential parameter in estimating whole-colony relative electron transport rate (rETR). As a whole, shallow colonies have double the photosynthetic capacity compared to deep colonies. In terms of phenotypic plasticity potentially optimizing photosynthetic capacity, we found that at 18 m, the present coral colony morphology increased the whole-colony rETR, while at 5 m, the colony morphology decreased potential light utilization and photosynthetic output. This result of potential energy acquisition being underutilized in shallow, highly lit waters due to the shallow type morphology present may represent a trade-off between optimizing light capture and reducing light damage, as this type morphology can perhaps decrease long-term costs of and effect of photoinhibition. This may be an important strategy as opposed to adopting a type morphology, which results in an overall higher energetic acquisition. Conversely, it could also be that maximizing light utilization and potential photosynthetic output is more important in low-light habitats for Acropora humilis. 相似文献
995.
O.E. Demesouka A.P. Vavatsikos K.P. Anagnostopoulos 《Waste management (New York, N.Y.)》2013,33(5):1190-1206
Multicriteria spatial decision support systems (MC-SDSS) have emerged as an integration of geographical information systems (GIS) and multiple criteria decision analysis (MCDA) methods for incorporating conflicting objectives and decision makers’ (DMs’) preferences into spatial decision models. This article presents a raster-based MC-SDSS that combines the analytic hierarchy process (AHP) and compromise programming methods, such as TOPSIS (technique for order preference by similarity to the ideal solution) and Ideal Point Methods. To the best of our knowledge it is the first time that a synergy of AHP and compromise programming methods is implemented in raster-driven GIS-based landfill suitability analysis. This procedure is supported by a spatial decision support system (SDSS) that was developed within a widely used commercial GIS software package. A real case study in the Thrace region in northeast Greece serves as a guide on how to conduct a suitability analysis for a MSW landfill site with the proposed MC-SDSS. Moreover, the procedure for identifying MSW disposal sites is accomplished by performing four computational models for synthesizing the DMs per criterion preferential system. Based on the case study results, a comparison analysis is performed according to suitability index estimations. According to them Euclidean distance metric and TOPSIS present strong similarities. When compared with Euclidean distance metric, TOPSIS seems to generate results closer to that derived by Manhattan distance metric. The comparison of Chebychev distance metric with all the other approaches revealed the greatest deviations. 相似文献
996.
997.
998.
999.