全文获取类型
收费全文 | 927篇 |
免费 | 149篇 |
国内免费 | 464篇 |
专业分类
安全科学 | 132篇 |
废物处理 | 17篇 |
环保管理 | 69篇 |
综合类 | 781篇 |
基础理论 | 335篇 |
污染及防治 | 102篇 |
评价与监测 | 44篇 |
社会与环境 | 48篇 |
灾害及防治 | 12篇 |
出版年
2024年 | 5篇 |
2023年 | 17篇 |
2022年 | 40篇 |
2021年 | 51篇 |
2020年 | 51篇 |
2019年 | 51篇 |
2018年 | 52篇 |
2017年 | 69篇 |
2016年 | 85篇 |
2015年 | 77篇 |
2014年 | 80篇 |
2013年 | 126篇 |
2012年 | 87篇 |
2011年 | 74篇 |
2010年 | 62篇 |
2009年 | 80篇 |
2008年 | 78篇 |
2007年 | 101篇 |
2006年 | 57篇 |
2005年 | 48篇 |
2004年 | 48篇 |
2003年 | 27篇 |
2002年 | 17篇 |
2001年 | 13篇 |
2000年 | 30篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 16篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有1540条查询结果,搜索用时 15 毫秒
131.
Katja?BargumEmail author Jacobus?J.?Boomsma Liselotte?Sundstr?m 《Behavioral ecology and sociobiology》2004,57(1):9-16
The genetic basis of morphological traits in social insects remains largely unexplored. This is even true for individual body size, a key life-history trait. In the social insects, the size of reproductive individuals affects dispersal decisions, so that small size in queens is often associated with reduced dispersal, and large size with long-range dispersal and independent colony founding. Worker size is connected to division of labour when workers specialize in certain tasks according to their size. In many species, variation in worker size has been shown to increase colony performance. In this study, we present the first evidence of an additive genetic component to queen size in ants, using maternal half sib analysis. We also compared intra-colony size variation in colonies with high (queen doubly mated) versus low (queen singly mated) genetic variability. We found a high and significant heritability (h2=0.51) for queen size in one of the two study years, but not in the other. Size variation among queens was greater in colonies headed by a doubly mated queen in one of the study years, but not in the other. This indicates that genetic factors can influence queen size, but that environmental factors may override these under some circumstances. The heritability for worker size was low (h2=0.09) and non-significant. Increased genetic diversity did not increase worker size variation in the colonies. Worker size appeared largely environmentally determined, potentially allowing colonies to adjust worker size ratios to current conditions.Communicated by J. Heinze 相似文献
132.
Szabolcs Lengyel 《Behavioral ecology and sociobiology》2007,61(4):589-598
When reproductive success is constant in one breeding phase, different tactics that increase variation in reproductive success
among individuals may evolve in other phases. For instance, in shorebirds, which usually have a limited clutch size of four
eggs, variation in reproductive tactics among individuals is expected either before egg-laying (e.g. diverse mating systems)
or after hatching of the young (e.g. diverse parental care). In this paper, I studied the pied avocet (Recurvirostra avosetta), a shorebird with a modal clutch size of four eggs, to test whether post-hatch chick adoption as an alternative tactic can
be linked to increased variation in annual reproductive success. When predation was high, naturally adopting pairs produced
more filial fledglings than did pairs not adopting chicks and not losing chicks to adoption. The number of filial fledglings
increased with the number of adopted young, possibly through diluting the chances of predation on filial young. Experimental
chick addition did not lead to more fledged young due to low brood integrity as shown by the frequent loss of chicks from
some experimental broods. When predation was low, larger broods occupied feeding territories with higher prey abundance than
smaller broods, possibly due to their dominance over smaller ones. Pairs that lost chicks to adoption (donors) fledged as
many filial young in their broods as did non-adopters/non-donors, whereas the total number of donors’ filial fledglings, including
those raised in adopting broods, approached that of adopters. These findings show, for the first time, that post-hatch alternative
reproductive tactics can lead to variation in annual reproductive success and to higher success for some pairs even in species
where past adaptations limit variation in reproductive success in a certain phase of reproduction. 相似文献
133.
134.
135.
为了探究3种不同粒径的污泥生物质炭(S1:大粒径 0.165 mm;S2:中粒径为0.025~0.165 mm;S3:小粒径0.025 mm)对Zn的吸附效率和固化稳定的机理,以此为污泥生物质炭在水污染控制方面的应用提供科学依据.利用实验室模拟法,研究不同反应时间、溶液初始pH和重金属浓度对生物炭吸附效果的影响,并运用四步萃取法分析生物炭上Zn的吸附形态.结果表明:①生物炭在4 h左右达到吸附平衡,吸附率呈先增加后平缓的趋势,最终吸附量S1S2S3;②溶液初始浓度为0~2 mmol·L~(-1)时Zn~(2+)的吸附量呈线性增长趋势,但随溶液浓度超过2 mmol·L~(-1)时吸附量开始趋于饱和;③3种不同粒径生物炭的水溶性组分Zn分别占总萃取量的1.70%、5.02%和7.47%,可交换态组分分别占25.27%、32.35%和27.29%,酸溶性组分分别占35.06%、38.63%和27.90%,非生物利用组分分别占37.97%、24.00%和37.34%.④污泥生物质炭的动力学吸附特征更符合准二级动力学吸附模型,单位质量的污泥生物质炭粒径越小吸附量越大;⑤污泥生物质炭的等温吸附特征更符合Langmuir模型,小粒径的生物质炭最大吸附量最优;⑥在酸性条件下随着pH的上升污泥生物质炭的吸附率在逐渐增加,碱性条件下吸附率的增加可能是形成锌的络合物沉淀导致的;⑦Zn的吸附形态以酸溶性和非生物利用态为主,水溶性占比较小.污泥生物质炭对Zn的吸附以化学吸附为主,S1吸附的Zn酸溶性组分和非生物利用组分占比最大,吸附效果较为稳定. 相似文献
136.
Brock TC Crum SJ Deneer JW Heimbach F Roijackers RM Sinkeldam JA 《Environmental pollution (Barking, Essex : 1987)》2004,130(3):411-426
Three different risk assessment procedures are described that aim to protect freshwater habitats from risks of the photosynthesis-inhibiting herbicides metribuzin and metamitron. These procedures are (1) the first-tier approach, based on standard toxicity tests and the application of an assessment factor, (2) the Species Sensitivity Distribution (SSD) approach, based on laboratory tests with a wider array of species and the application of a statistical model to calculate the HCx (the Hazardous Concentration for x% of the species), and (3) the model ecosystem approach, based on the evaluation of treatment-related effects in field enclosures. A comparison of the risk assessment procedures reveals that the first-tier approach is the most conservative for metamitron and metribuzin, and that HC5 values (and even HC10 values) based on acute EC50 values of algae and aquatic vascular plants may be used to derive maximum permissible concentrations for single applications. For both compounds these HC5 values were very similar to the ecological threshold concentrations in the enclosure studies. In contrast to model ecosystem experiments, however, HCx values based on lab toxicity tests do not provide information on the recovery potential of sensitive endpoints and on indirect effects, which may be important for regulatory decision-making. In the enclosure study, indirect effects of metribuzin on invertebrate populations were observed at an exposure concentration that was approximately 20 times lower than the corresponding HC5 value based on lab toxicity data for aquatic invertebrates. 相似文献
137.
Haloacetic acids (HAAs) are environmental contaminants found in aquatic ecosystems throughout the world as a result of both anthropogenic and natural production. The ecological risk posed by these compounds to organisms in freshwater environments, with a specific focus on aquatic macrophytes, was characterized. The plants evaluated were Lemna gibba, Myriophyllum spicatum and M. sibiricum and the HAAs screened were monochloroacetic acid (MCA), dichloroacetic acid (DCA), trichloroacetic acid (TCA), trifluoroacetic acid (TFA) and chlorodifluoroacetic acid (CDFA). Laboratory toxicity data formed the basis of the risk assessment, but field studies were also utilized. The estimated risk was calculated using hazard quotients (HQ), as well as effect measure distributions (EMD) in a modified probabilistic ecological risk assessment. EMDs were used to estimate HAA thresholds of toxicity for use in HQ assessments. This threshold was found to be a more sensitive measure of low toxicity than the no observed effect concentrations (NOEC) or the effective concentration (EC10). Using both deterministic and probabilistic methods, it was found that HAAs do not pose a significant risk to freshwater macrophytes at current environmental concentrations in Canada, Europe or Africa for both single compound and mixture exposures. Still, HAAs are generally found as mixtures and their potential interactions are not fully understood, rendering this phase of the assessment uncertain and justifying further effects characterization. TCA in some environments poses a slight risk to phytoplankton and future concentrations of TFA and CDFA are likely to increase due to their recalcitrant nature, warranting continued environmental surveillance of HAAs. 相似文献
138.
不同粒度飞灰中16种微量元素的含量分布 总被引:7,自引:0,他引:7
研究了不同粒级的燃煤飞灰中的Ba、Be、Cd、Cr、Cu、Hg、Li、Mn、Ni、Pb、Sr、Ti、V、Zn、Zr元素的含量分布,煤中元素的含量比及富集因子。 相似文献
139.
受西风控制的天山地区黄土广泛分布,是中亚重要的黄土分布区之一。这些陆相风成沉积物为研究中亚干旱区气候环境变化历史提供了重要的信息载体。本文选取天山北麓博乐地区一个厚为12.7 m的黄土剖面作为研究对象,分析了其磁化率、粒度指标的变化特征,并探讨了其古气候意义。结果表明:(1)博乐黄土粒度组成以粉砂为主,是典型的风成沉积物,成壤作用很弱;(2)博乐黄土磁化率变化主要受控于风力强度;(3)剖面粒度的环境敏感粒级为31.7μm、31.7—282.5μm,分别可能代表风暴过后的浮尘堆积和风暴过程中风力近距离搬运的沉积物组分;(4)博乐黄土MIS(海洋氧同位素)3阶段记录了多次千年尺度气候事件,能与北大西洋Heinrich事件和D-O事件对应,表明中纬度西风环流在传递北大西洋信号到东亚的过程中扮演着重要角色。 相似文献
140.
研究沙尘随高度的变化特征对揭示沙尘物质在近地层分布特征具有重要意义。为揭示0—80 m沙尘通量的垂直分布规律,在野外实测的基础上,选取2008年7月20日、8月7日、8月19日、8月29日4次沙尘天气,对贴地层(0—0.05 m)、中间层(0.05—2 m)、近地层(2—80 m)的沙尘通量进行对比分析。结果表明:贴地层(0—0.05 m),沙尘通量随着高度的增高呈增加趋势,最大值为1604.29 g?mm?2。中间层(0.05—2 m),沙尘通量随高度分布的关系为幂函数关系,且随着高度的升高沙尘通量减小,决定系数R2值均在0.9以上。近地层(2—80 m),沙尘通量随高度增加呈分段函数分布,32 m、48 m处为沙尘通量的拐点高度。由此看出,研究沙尘通量对阐明沙尘输送机制非常重要,不仅可加强对沙尘输送的定量研究,还可为沙尘输送的数值模拟提供重要参数。 相似文献