全文获取类型
收费全文 | 415篇 |
免费 | 24篇 |
国内免费 | 13篇 |
专业分类
安全科学 | 67篇 |
废物处理 | 4篇 |
环保管理 | 93篇 |
综合类 | 100篇 |
基础理论 | 83篇 |
污染及防治 | 5篇 |
评价与监测 | 4篇 |
社会与环境 | 82篇 |
灾害及防治 | 14篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 17篇 |
2016年 | 7篇 |
2015年 | 13篇 |
2014年 | 8篇 |
2013年 | 24篇 |
2012年 | 24篇 |
2011年 | 26篇 |
2010年 | 16篇 |
2009年 | 25篇 |
2008年 | 18篇 |
2007年 | 25篇 |
2006年 | 28篇 |
2005年 | 20篇 |
2004年 | 18篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 10篇 |
2000年 | 19篇 |
1999年 | 12篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有452条查询结果,搜索用时 31 毫秒
81.
82.
Abstact Ecological city is the advanced mode of harmonious development of city. Constant improvement is being made in the development of ecological city. However, building ecological city is an enormous project that calls for a huge amount of capital. The government fund is far from adequate. This paper probes into the fund issue and discusses in detail the mechanism of investment and financing in building ecological city from various aspects such as diversification of the investment subjects and the modes of financing. 相似文献
83.
石油化工企业的安全事故频发和职业危害严重,不仅造成重大经济损失,而且对社会造成了不良影响,不合理的安全投资是造成这种状况的主要原因之一,对企业现有安全投资状况进行评价是合理进行安全投资的前提和基础。本文针对石油化工企业安全投资评价中诸多不确定性因素和动态特征进行分析,运用集对分析和马尔可夫链理论,建立了基于集对分析石化企业安全投资状况的动态评价模型,为安全投资状况评价工作提供了一个新方法。以某石油化工企业为例,通过对该企业2006-2009年这四年安全投资状况进行动态评价分析,并预测出2010年该企业的安全投资状况。评价结果表明,将集对分析和马尔可夫链理论用于石化企业安全投资状况的动态评价与预测,起到了非常好的效果,能够为企业科学合理地作出正确决策提供理论依据。 相似文献
84.
为探究中国在东南亚地区的海外耕地投资活动规律,利用文献资料法、空间分析法和灰色关联分析法,从空间分布和影响因素两方面进行分析。结果表明:(1)中国海外耕地投资项目多位于中南半岛,且有沿边分布特点;(2)中国在东南亚海外耕地投资意向项目、合同项目的空间分布相似性较高,而生产项目与前两者存在差异;(3)中国海外耕地投资受地缘经济、地缘文化、资源基础和地缘政治的影响且受影响程度依次减弱,其中年均进出口总值、年均中国对外直接投资存量等指标对中国企业的投资选择具有显著影响。东南亚地区作为当前中国海外耕地投资的重要区域,强化同东南亚国家间的经济、文化交流,对中国企业顺利开展海外耕地投资活动具有重要促进作用。 相似文献
85.
Although many avian eggs appear to be cryptically colored, many species also lay vibrant blue green eggs. This seemingly conspicuous
coloration has puzzled biologists since Wallace, as natural selection should favor reduced egg visibility to minimize predation
pressure. The sexual signaling hypothesis posits that blue green egg coloration serves as a signal of female quality and that
males exert post-mating sexual selection on this trait by investing more in the nests of females laying more intensely blue
green eggs. This hypothesis has received mixed support to date, and most previous studies have been conducted in cavity-nesting
species where male evaluation of his partner’s egg coloration, relative to that of other females, may be somewhat limited.
In this study, we test the sexual signaling hypothesis in colonially nesting ring-billed gulls (Larus delawarensis) where males have ample opportunity to assess their mate’s egg coloration relative to that of other females. We used correlational
data and an experimental manipulation to test four assumptions and predictions of the sexual signaling hypothesis: (1) blue
green pigmentation should be limiting to females; (2) extent of blue green egg coloration should relate to female quality;
(3) extent of blue green egg coloration should relate to offspring quality; and (4) males should provide more care to clutches
with higher blue green chroma. Our data provide little support for these predictions of the sexual signaling hypothesis in
ring-billed gulls. In light of this and other empirical data, we encourage future studies to consider additional hypotheses
for the evolution of blue green egg coloration. 相似文献
86.
工业废水排放量和治理投资费用的预测 总被引:3,自引:1,他引:2
利用1996—2005年相关统计数据以及专项调查数据,对重点排放行业工业废水的产生、排放特征以及治理费用函数进行分析,建立了分行业的宏观工业废水排放和治理费用预测模型,并预测了2006—2020年工业废水排放趋势、投资需求以及减排重点. 结果表明:到2010年,工业废水和CODCr产生量分别为646×108~658×108和1 575×104~2 031×104 t,二者的排放量将分别介于234×108~301×108和441.1×104~609.2×104 t;“十一五"期间工业废水治理投资和治理费用如不能达到8 000×108元,将面临CODCr减排目标不能完成的风险. 相似文献
87.
没有一个有序高效的环保资本市场,缺乏强有力的资金支持系统是阻碍环保产业快速发展的根本问题。本文在调查研究和探索实践的基础上,建议在资金筹划、分配及使用上引进市场机制,发挥市场在资金运作方面的调节作用,引导资金向环保产业流动,促进环保产业快速发展。 相似文献
88.
评析中国现行环境保护投资体制 总被引:9,自引:0,他引:9
本文通过对我国近15年环保投资相关数据的分析,揭示了现行环保投资体制失灵的一个重要因素是结构上失衡,在环保投资中没有体现环保设施运营费用,直接影响了环保投资的效益,其次,一些指标的设计严重偏离了现实,影响了环保投资的有机构成,也导致环境政策的失效,在此基础上,结合实际,提出初步的改革设想。 相似文献
89.
Optimal parental investment usually differs depending on the sex of the offspring. However, parents in most organisms cannot
discriminate the sex of their young until those young are energetically independent. In a species with physical male–male
competition, males are often larger and usually develop sexual ornaments, so male offspring are often more costly to produce.
However, Onthophagus dung beetles (Coleoptera; Scarabaeidae) are highly dimorphic in secondary sexual characters, but sexually monomorphic in
body size, despite strong male–male competition for mates. We demonstrate that because parents provide all resources required
by their offspring before adulthood, O.
atripennis exhibits no sexual size dimorphism irrespective of sexual selection pressure favoring sexual dimorphism. By constructing
a graphic model with three fitness curves (for sons, daughters, and expected fitness return for parents), we demonstrate that
natural selection favors parents that provide both sons and daughters with the optimal amount of investment for sons, which
is far greater than that for daughters. This is because the cost of producing small sons, that are unable to compete for mates,
is far greater than the cost of producing daughters that are larger than necessary. This theoretical prediction can explain
sexual dimorphism without sexual size dimorphism, widely observed in species with crucial parental care such as dung beetles
and leaf-rolling beetles, and may provide an insight into the enigmatic relationship between sexual size dimorphism and sexual
dimorphism. 相似文献
90.
Lisa E. Schwanz 《Behavioral ecology and sociobiology》2008,62(8):1351-1358
Parasitized animals may alter their life histories to minimize the costs of parasitism. Organisms are predicted to decrease
investment in current reproduction when parasitism has the greatest impact on current reproductive ability. In contrast, if
parasitism decreases residual reproductive value, hosts should increase current reproductive investment, referred to as fecundity
compensation or terminal investment. In mammalian hosts, parasitic infection most often leads to reductions in current host
reproduction, perhaps attributable to the emphasis on parasites that are unlikely to impact the host’s residual reproductive
value. In this study, the life history response of a rodent, Peromyscus maniculatus, to infection with a parasite that should strongly impact the residual reproductive value of its host (Schistosomatium douthitti, Trematoda) was examined. Infection decreased survival for hosts exposed to a high dose of parasites and was chronic in survivors,
confirming that infection had strong impacts for the residual reproductive value of the host. As predicted, infected mice
increased their reproductive output, producing litters of greater mass due to heavier offspring. However, this increased output
was observed after a greater delay to begin breeding in infected mice and was not observed in animals that suffered early
mortality. The deer mouse S. douthitti system may provide a rare example of fecundity compensation in mammals. 相似文献