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961.
We present a cellular automaton that simulates the interaction between a host tree and multiple potential mycorrhizal symbionts and generates testable hypotheses of how processes at the scale of individual root tips may explain mycorrhizal community composition. Existing theoretical biological market models imply that a single host is able to interact with and select from multiple symbionts to organize an optimal symbiont community. When evaluating the tree–symbiont interaction, two scales must be considered simultaneously: the scale of the entire host plant at which carbon utilization and nutrient demands operate, and the scale of the individual root tip, at which colonization and carbon-nutrient trade occurs. Three strategies that may be employed by the host tree for optimizing carbon use and nutrient acquisition through mycorrhizal symbiont communities are simulated: (1) carbon pool adjustment, in which the plant controls only the total amount of carbon to be distributed uniformly throughout the root system, (2) symbiont selection, wherein the plant opts either for or against the interaction at each fine root tip, and (3) selective carbon allocation, wherein the plant adjusts the amount of carbon allocated to each root tip based on the cost of nutrients. Strategies were tested over various nutrient availabilities (the amount of inorganically and organically bound nutrients). Success was defined on the basis of minimizing carbon expended for nutrient acquisition because this would allow more carbon to be utilized for growth and reproduction. In all cases, the symbiont selection and selective carbon allocation strategies were able to meet the nutritional requirements of the plant, but did not necessarily optimize carbon use. The carbon pool adjustment strategy is the only strategy that does not operate at the individual root tip scale, and the strategy was not successful when inorganic nutrients were scarce since there is no mechanism to exclude suboptimal symbionts. The combination of the symbiont selection strategy and the carbon pool adjustment resulted in optimal carbon use and nutrient acquisition under all environmental conditions but result in monospecific symbiont assemblages. On the other hand, the selective carbon allocation strategy is the only strategy that maintained successful, multi-symbiont communities. The simulations presented here thus imply clear hypotheses about the effect of nutrient availability on symbiont selection and mycorrhizal community richness and composition. 相似文献
962.
创新创业是我国未来数十年经济社会发展的主旋律之一,商业模式创新是其高端形态,也是改变产业竞争格局的重要力量和前提。在分析了影响区域性再生资源产业跨越式发展的某些潜在因素的基础上,认为促进其发展的三要素包括:稳固的基点、明确的目标和充足的动力;阐述了观念创新是实现战略性新兴产业跨越式发展的前提的论点;探索性地提出了蓄力于产业发展战略基点处的工作思路。 相似文献
963.
中国、美国、摩洛哥磷矿资源优势及开发战略比较分析 总被引:21,自引:0,他引:21
从资源保护和优化利用的角度出发,比较了中国、美国、摩洛哥三国磷矿石的储量、品位、重金属含量、矿产集中度、运输距离等,发现摩洛哥磷矿资源具有极强的优势,而美国资源也要优于中国。在比较了矿产开发规模、回采率、产量、成本、可利用年度等指标后,发现美国与摩洛哥各有优劣,而中国明显落后。根据磷肥生产量估算,2003年中国磷矿实际消耗量达到10558×104t标矿。根据现有开采水平和消费量估算,世界磷矿可以满足100年内的需求,但是中国P2O5≥30%的富矿资源仅能利用到2014年,提高回采率可能会达到2022年。中国磷矿资源开发策略欠佳,浪费严重、经济效益低下,导致远景供应堪忧。针对以上问题,提出了我国磷矿资源合理利用的若干建议。 相似文献
964.
研究了华南地区外来入侵种薇甘菊Mikania micrantha H B Kunth不同光环境下形态和生理可塑性及其适应性响应。通过模拟开阔地段、林缘、大林窗、小林窗、林下等不同生境的的光照环境,并设计一个干扰实验,分析了薇甘菊的生长、碳同化以及生物量分配如何对光环境作出适应性响应。研究了当干扰发生时,薇甘菊如何对光环境的变化做出形态和生理可塑性响应。通过对其各项生物量分配及气体交换等指标的观测,在小林窗光照环境下薇甘菊生长缓慢生物量积累较少,但是如果一旦受到干扰,光照环境得到改善,薇甘菊将在很短的时间内通过适应性形态和生理可塑性响应,迅速体现出较强的入侵性。这也可能是入侵植物薇甘菊"坐待对策(sit and wait strategy)"的生动体现:如果外界环境不利,暂且先保持繁殖体(种子或者根茎),一旦条件成熟(发生干扰条件得到改善或者遗传变异或者生态生理的积累),就会迅速爆发。所以我们一方面,不用担心郁闭的森林会被薇甘菊入侵,但另一方面也要注意干扰会引起光照等环境条件的改变,使得原来潜伏于林下的薇甘菊繁殖体重新变得富有入侵性。 相似文献
965.
甘肃马先蒿(Pedicularis kansuensis)作为高寒草甸退化进程中的一种入侵毒杂草,其生长状况和繁殖特征为草地退化状况的重要指标,也是衡量高寒草甸演替进程的重要指示植物。通过比较重度退化和未退化高寒草甸的群落特征,甘肃马先蒿的生长状况与花期资源分配,结果表明:退化的高寒草甸土壤-植被系统变化明显,高寒草甸退化显著影响了甘肃马先蒿的生长状况和资源分配特征。在重度退化的黑土滩样地中,甘肃马先蒿个体形态特征如株高、根长、分叉数、叶片数、花数、总生物量都显著高于未退化高寒矮嵩草草甸样地;重度退化草甸中甘肃马先蒿花期各器官的资源投资状况,如根系投资、茎叶投资、繁殖投资分别为7.46%、48.76%、43.78%,未退化样地中甘肃马先蒿的根系投资、茎叶投资、繁殖投资分别为10.12%、54.34%、35.54%。在重度退化高寒草甸中甘肃马先蒿占据较大的生态位,长势良好,且将资源更多地用于繁殖投入。而未退化草甸中甘肃马先蒿优势度不大,更多的是将资源分配到根系和茎叶等营养器官,以期获得较多的水分、无机盐、光照等资源,增强个体竞争力。甘肃马先蒿在不同生境下资源分配的显著差异实质反映了草地退化的影响,亦是植物对外部环境改变的一种适应机制,同时也是植物可塑性的重要表现形式。 相似文献
966.
Valentin Amrhein Lars Erik Johannessen Lena Kristiansen Tore Slagsvold 《Behavioral ecology and sociobiology》2008,62(10):1633-1641
The costs and benefits of bird song are likely to vary among species, and different singing patterns may reflect differences
in reproductive strategies. We compared temporal patterns of singing activity in two songbird species, the blue tit (Cyanistes caeruleus) and the great tit (Parus major). The two species live side by side year round, and they have similar breeding ecology and similar rates of extra-pair paternity.
However, they differ in two aspects of reproductive strategy that may have an influence on song output: blue tits are facultatively
polygynous and have a fairly short breeding season with almost no second broods, whereas great tits are socially monogamous
but more commonly raise second broods. We found that great tit males continued singing at high levels during the egg-laying
and incubation periods, while monogamously paired blue tit males strongly reduced singing activity after the first days of
egg-laying by their female. Since males of both species sang much more intensely shortly before sunrise than after sunrise,
at midday or in the evening, this difference was most conspicuous at dawn. No differences in singing activity were found within
species when testing for male age. We suggest that in contrast to blue tits, great tit males continued singing after egg-laying
to defend the territory and to encourage the female for a possible second brood. 相似文献
967.
968.
高新技术产业是知识经济时代的主要支柱产业,其快速发展在为人类带来巨大利益的同时,往往具有更高的孕灾潜势和事故风险。本文分析了高新技术灾害经济问题的特殊性,并提出了减灾防灾应采取的主要措施。 相似文献
969.
970.
V. V. Tarasov 《Russian Journal of Ecology》2005,36(3):193-199
The return of willow ptarmigans to the sites in which they nested the previous year has been studied using color banding. No factors influencing the return index have been revealed, except for its dependence in males on the time when spring begins in a given year. In northernYamal, in contrast to the temperate zone, some surviving birds fail to return to their former nesting sites. Polymorphism of individuals with respect to territorial behavioral strategy is proposed for L. lagopus populations at the northern boundary of the species range.__________Translated from Ekologiya, No. 3, 2005, pp. 215–221.Original Russian Text Copyright © 2005 by Tarasov. 相似文献