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排序方式: 共有854条查询结果,搜索用时 875 毫秒
521.
以淇县人民医院污水处理站实际生产工艺流程为研究对象,全面考察了污水处理采用预处理+格栅+调节池+缺氧好氧工艺+絮凝沉淀+过滤+二氧化氯消毒工艺,污泥处理采用污泥浓缩+压滤脱水工艺的工作性能.同时系统介绍了各个处理单元的功能和设计要点,为工艺推广应用提供直接的设计依据.在此基础上,对医院污水收集、污水处理工艺选择、污水处理设施选择以及处理设施运行管理等方面进行了总结探讨. 相似文献
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525.
季建林 《城市环境与城市生态》2000,13(6):18-20
我国的城市化水平落后于工业化水平,已成为制约我国经济与社会发展的重要因素。提升我国城市化水平,从经济上讲,具有如下重要意义:(1)有利于化解有效需求不足矛盾。(2)有利于带动相关产业增长和主人口增加。(3)有利于促进我国产业结构优化,提高经济运行质量。(4)有利于资源的综合利用和耕地保护。(5)有利于缩小城乡差距。提升我国城市化水平是我国新世纪的战略任务,必须进行相关的政策调整与选择。 相似文献
526.
Some mate choice theories propose that only male signals that are honest and condition-dependent can be stable, while another
hypothesis states that males evolve signals that exploit the sensory system of females. However, sensory traps might evolve
into honest signals if they are differentially costly for males. We tested whether a pre-existing sensory bias for food chemicals
explained chemosensory preferences of female Iberian rock lizards for male scents. We manipulated hunger levels of females
and found that food-deprived females had increased chemosensory responses to chemical stimuli from both invertebrate prey
and femoral secretions of males, but not to control water. Further tests suggested that cholesta-5,7-dien-3-ol (provitamin
D3), a lipid found in both prey and males’ scent, may be one of the chemicals eliciting these responses. Moreover, hungry females
spent more time on scent marks of males that had experimentally increased cholesta-5,7-dien-3-ol than on scent marks of males
alone, whereas for control females this effect was not significant. We suggest that preexisting sensory bias for essential
nutrients (i.e., provitamin D) may be the origin of similar female responses to male chemicals. However, previous studies
have suggested that the allocation of these chemicals to ornaments is costly and only high quality males can afford it. Therefore,
preexisting sensory bias for essential nutrients may further allow the evolution and maintenance of honest sexual displays. 相似文献
527.
Peter M. Kappeler 《Behavioral ecology and sociobiology》1998,42(6):411-421
The goals of this study were to investigate the transmission and possible functions of chemical signals in intragroup communication
among ring-tailed lemurs, Lemur catta. In particular, I examined the effects of sex on these processes because sexual selection theory predicts specific functions
for chemical signals. I recorded all interactions with 214 scent marks of 11 male and 9 female ring-tailed lemurs during the
first 10 min following their deposition. I found that 62% of these scent marks were investigated with a median latency of
30 s and that 89% of investigated scents were also counter-marked by the receiver. The type of focal scent mark (male or female
anogenital and male antebrachial mark) had a significant effect on both the timing and type of response. Males investigated
and counter-marked female scents more often than vice versa, but significant second-order transitions suggested that the behavior
of an animal was not only influenced by the immediately preceding scent mark and that a scent is not completely masked by
a counter-mark. There was no evidence for an audience effect, and only social rank of female senders had an effect on receivers.
Variation in the response of receivers across reproductive seasons as a function of senders' sex indicated that female scents
may function in mate attraction and competition among females, whereas male scents may be primarily used in intrasexual competition.
Three main conclusions emerged. First, the exchange of olfactory signals within groups was highly structured and surprisingly
efficient. Second, olfactory signals may constitute general mesasages whose transfer is partly controlled by the receiver.
Finally, sexual selection theory provides a useful theoretical framework for functional examinations of mammalian olfactory
communication.
Received: 13 June 1997 / Accepted after revision: 20 March 1998 相似文献
528.
Anders Pape Møller 《Behavioral ecology and sociobiology》2007,61(8):1311-1319
Protandry reflects the earlier arrival of males than females to the site of reproduction. Such protandry is hypothesised to
arise from sex differences in costs and benefits of early arrival. I investigated temporal patterns of arrival date of male
and female barn swallows Hirundo rustica and temporal patterns of selection to test the hypothesis that sex differences in selection account for sex differences in
arrival date. Mean arrival date of male barn swallows but not of females advanced during the last 33 years, giving rise to
an increasing sex difference in arrival date. Early arrival was favoured by increasingly better survival in males, while females
showed an opposite pattern that did not reach significance, although the effect differed between sexes. Early arrival increased
fecundity in both sexes equally.The sex difference in viability selection in relation to arrival date changed from positive
to negative as the degree of protandry increased in recent years, although there was no similar significant relationship for
fecundity selection. Furthermore, sex differences in viability selection in a given year affected the degree of protandry
in the following year through differential survival of certain phenotypes over others. Finally, temporal changes in sex difference
in viability selection and protandry were related to an increase in the interval between first and second clutches, as the
duration of the breeding season increased because of climatic amelioration. These findings suggest that arrival date is under
divergent selection in the two sexes, providing a mechanism for the evolution of protandry. 相似文献
529.
层次分析法在闽南沿海山地混交林优化模式选择上的应用 总被引:1,自引:0,他引:1
陈如英 《湖南环境生物职业技术学院学报》2006,12(4):353-355
采用层次分析法(AHP)对闽南沿海山地各混交经营模式进行层次决策选择,从层次选择模型和判断矩阵的构建入手,对评价因子和混交优化模式进行排序并经一致性检验,结果表明,所构建的判断矩阵的随机一致性比率=0.0646<0.10,总排序的=0.0516<0.10,均具有满意的一致性和可靠性,选择出的优化模式与现实生产实际相吻合,说明层次分析法在混交林经营模式的定量化选择上的应用是可行的. 相似文献
530.
This paper explores the problem of China's ‘missing’ girls—estimated to run into many millions. It considers the impact of the underpinning Confucian value system in China that has produced a culture of son preference and which, together with China's compulsory family planning program and ‘one child policy’, has effectively established a ‘one son policy’. Discussion of the various means by which the birth or survival of daughters have traditionally been prevented provides the context for identifying the contribution of new sex selection procedures to the maintenance of son preference in contemporary Chinese society. The paper concludes that China's son preference is not simply a personal problem for the millions of ‘missing girls’ who were destined to live a shorter life and for the surviving girls who continue to face considerable discrimination simply because they are of the ‘wrong’ sex; it heralds a social and demographic disaster of major proportions for which neither the government nor the people of China appear to have the will or the means to forestall. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献