首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   722篇
  免费   78篇
  国内免费   390篇
安全科学   96篇
废物处理   6篇
环保管理   59篇
综合类   612篇
基础理论   240篇
污染及防治   78篇
评价与监测   35篇
社会与环境   46篇
灾害及防治   18篇
  2024年   3篇
  2023年   15篇
  2022年   41篇
  2021年   37篇
  2020年   25篇
  2019年   39篇
  2018年   42篇
  2017年   37篇
  2016年   45篇
  2015年   46篇
  2014年   49篇
  2013年   77篇
  2012年   61篇
  2011年   54篇
  2010年   60篇
  2009年   56篇
  2008年   49篇
  2007年   94篇
  2006年   77篇
  2005年   47篇
  2004年   32篇
  2003年   46篇
  2002年   30篇
  2001年   16篇
  2000年   25篇
  1999年   19篇
  1998年   14篇
  1997年   8篇
  1996年   10篇
  1995年   11篇
  1994年   5篇
  1993年   3篇
  1992年   4篇
  1991年   5篇
  1990年   1篇
  1989年   2篇
  1986年   1篇
  1984年   1篇
  1982年   1篇
  1975年   1篇
  1974年   1篇
排序方式: 共有1190条查询结果,搜索用时 15 毫秒
991.
哈得逊地区是塔里木盆地近期黑油勘探的重点地区 ,石炭系中泥岩段和东河砂岩段是勘探的两个主要目的层 ,两个层系目前均获得高产油流。笔者从烃源岩分析、构造演化、油气的运移聚集几个方面对哈得逊油田的成藏规律进行研究 ,认为石岩系中泥岩段和东河砂岩原油均来自中上奥陶统烃源岩 ,并且由于塔北的构造反转作用使得哈得逊地区原油与塔北地区具同源性质。哈得逊地区石炭系以发育低幅度背斜及受东河砂岩尖灭线控制的复合圈闭为基本特征 ,具面积大、幅度小的特点。这是在没有断层的条件下 ,不整合面作为长距离运移通道的一个典型地区 ,其中区域构造反转对后期油气的运移和聚集起着决定作用  相似文献   
992.
云南省在开展环境监测资源调查和环境监测能力现状评估中,结合实际,制定了调查指标、评估的原则和由5大指标(47个分指标)组成的量化评估指标体系,采用百分制对监测站的能力状况进行评价,并将其监测能力划分为三级四档来给出评估结果。通过调查评估,查清了全省环境监测资源的家底.为优化整合资源配置起到了积极作用。  相似文献   
993.
Seven kinds of heavy metal accumulation of rubbish compost in turfgrass by EDTA chelating were investigated. With EDTA application, heavy metal accumulation by two species of turfgrass was increased significantly. The enrichment coefficients of Lolium perenne L(L) and Festuca arundinacea L(F) to Cr reached 9.4.5 and 6.15 respectively. In the range of EDTA dosages given, heavy metal accumulation in turfgrass increased with increasing EDTA level. There were significant differences in remediation of different metals by applying EDTA. L had high ability to accumulate Cr, Cd, Ni and Zn, showing better remediation to heavy metals of rubbish compost. In contrast, F showed high ability to accumulate Cr, Ni, Cu and Zn. Low EDTA level increased aboveground net primary production (ANP) of turfgrass, but EDTA would considerably inhibit it when EDTA was higher than 20 mmol/kg. The results demonstrated that the optimum dosage of EDTA for remediating heavy metals in rubbish compost by turfgrass was between 10 mmol/kg and 20 mmol/kg.  相似文献   
994.
Four materials, sodium carboxymethylcellulose (Na-CMC), sodium alginate (SA), polyvinyl alcohol (PVA), and chitosan (CTS), were prepared as supports for entrapping fungus Aspergillus fumigatus. The adsorption of synthetic dyes. Reactive Brilliant Blue KN-R, and Reactive Brilliant Red K-2BP, by these immobilized gel beads and plain gel beads was evaluated. The adsorption efficiencies of Reactive Brilliant Red K-2BP and Reactive Brilliant Blue KN-R by CTS immobilized beads were 89.1% and 93.5% in 12 h, respectively. The adsorption efficiency by Na-CMC immobilized beads was slightly lower than that of mycelial pellets. But the dye culture mediums were almost completely decolorized in 48 h using the above-mentioned two immobilized beads (exceeding 95%). The adsorption efficiency by SA immobilized beads exceeded 92% in 48 h. PVA-SA immobilized beads showed the lowest adsorption efficiency, which was 79.8% for Reactive Brilliant Red K-2BP and 92.5% for Reactive Brilliant Blue KN-R in 48 h. Comparing the adsorption efficiency by plain gel beads, Na-CMC plain gel beads ranked next to CTS ones. SA and PVA-SA plain gel beads hardly had the ability of adsorbing dyes. Subsequently, the growth of mycelia in Na-CMC and SA immobilized beads were evaluated. The biomass increased continuously in 72 h. The adsorption capacity of Reactive Brilliant Red K-2BP and Reactive Brilliant Blue KN-R by Na-CMC immobilized beads was 78.0 and 86.7 mg/g, respectively. The SEM micrographs show that the surface structure of Na-CMC immobilized bead is loose and finely porous, which facilitates diffusion of the dyes.  相似文献   
995.
颗粒物捕集器技术首次应用到港口疏浚监测中,通过对现场疏浚悬浮颗粒物的监测以及对生物的急性半致死浓度的模拟实验研究,建立了一套较完整的疏浚监测系统和技术,可以更有效和直观地反映疏浚过程中对养殖海区生物的影响。现场调查和实验结果表明:在疏浚区和养殖区交界处疏浚悬浮物在海水表面的垂直通量为12.68mg/(cm^2.d),中层为25.41mg/(cm^2.d);在养殖中心区表层为7.58mg/(cm^2  相似文献   
996.
PAC-MBR处理垃圾渗滤液的硝化性能研究   总被引:2,自引:0,他引:2  
研究了粉末活性炭(PAC)作为载体的膜生物反应器(MBR)处理吹脱后垃圾渗滤液的硝化性能。在HRT=3d、NH4^+N=200~500mg/L条件下,进水pH〉8.7时,PAC-MBR和没有添加PAC的普通MBR均只能将氨氮转化为NO2^-;降低pH至7.6~8.2时,PAC—MBR中的亚硝酸盐氧化菌迅速恢复活性,将NO/完全转化为硝酸盐,而普通MBR仍然停留在亚硝化阶段;当吹脱取消后,NO/迅速消失,这可能与取消吹脱后,不再使用大量硫酸进行pH调节有关。研究发现,当SO4^2-为3g/L时,氨氮氧化速度出现了明显的下降,表明SO4^2-对硝化菌具有抑制作用;同时,微生物代谢产物(SMP)分泌量越高,NO2^-含量越低,但是SMP不是影响NO2^-积累的主要原因。  相似文献   
997.
Singh S  Saxena R  Pandey K  Bhatt K  Sinha S 《Chemosphere》2004,57(11):1663-1673
The interaction of metals present in tannery waste and their tolerance in the plants of sunflower (Helianthus annuus L.) was studied in the present paper under field conditions. Effects of 100% tannery sludge and various amendments of tannery sludge (10%, 25%, 35%, 50%, 75%) along with one set of control were studied on the physiological and biochemical parameters of the plant along with their metal accumulation potential after 30, 60 and 90 d after sowing. The plants of H. annuus were found effective in the accumulation of metals (Cr, Fe, Zn and Mn) in roots, shoots and leaves, however, the level of toxic metal, Cr was found below detection limit in the seeds of the plant. The oil was extracted from the seeds of the plant and the level of oil content was increased up to 35% tannery sludge as compared to control followed by decrease at higher tannery sludge ratio. An increase in the chlorophyll, protein, cysteine, non-protein thiol and sugar contents was observed at the lower amendment of tannery sludge at initial exposure periods followed by decrease than their respective controls. Malondialdehyde content in the roots and leaves was increased beyond 50% sludge amendments at all the exposure periods as compared to control. However, proline and ascorbic acid contents of the roots and leaves of the plant increased at all the exposure periods and sludge amendments, compared to their respective controls.  相似文献   
998.
不同来源的海州香薷和野胡萝卜的铜抗性及铜积累差异   总被引:2,自引:0,他引:2  
以来自矿区(铜绿山和赤马山铜矿)和非矿区(红安、武汉严西湖)的海州香薷和野胡萝卜种群为对象,通过土培实验,研究了2种植物的铜抗性及铜吸收积累差异.结果显示,来自矿区的海州香薷和野胡萝卜种群的铜抗性都明显高于非矿区种群,但2种植物种群的铜吸收积累特征明显不同:海州香薷植物吸收的Cu主要集中在根中,但矿区种群吸收积累的铜量明显低于非矿区种群;而野胡萝卜吸收的Cu主要集中在地上部分(地上部分的Cu富集量是根的1.5倍),但积累的铜量在矿区和非矿区种群间没有明显的差异.因此,来自矿区的海州香薷可能进化为铜避性对策,而野胡萝卜的铜抗性与其吸收积累的总量没有明显的关系,但有很好的向地上运输能力.  相似文献   
999.
The understanding of trade-offs between behaviours is fundamental to the study of animal behaviour. Individuals may often be faced with the choice of which of two mutually incompatible behaviours to perform. Here, I present a model investigating the trade-off between two behaviours, where one of the behaviours is crucial to the success of the other. I illustrate the results with examples, considering particularly a trade-off between territorial defence and courtship. I investigate how the ability of an individual to perform the behaviours changes the time or energy allocated to each behaviour. Intuition suggests that the time invested in performing a behaviour should decline as the individuals ability to perform the behaviour increases. Explicit, quantitative modelling suggests that this is not always the case. Instead, we see a pattern where investment in one of the behaviours at first increases and then decreases as the ability to perform the behaviour increases. This finding has implications for the empirical study of trade-offs between behaviours, since it could appear that individual ability has no effect on the trade-off under consideration. I discuss potential methods for distinguishing whether time allocation changes in a counter-intuitive, non-monotonic way with increasing individual ability, or whether there is indeed no effect.Communicated by C. St. Mary  相似文献   
1000.
According to indicator models of sexual selection, mates may obtain indirect, i.e. genetic, benefits from choosing partners indicating high overall genetic quality by honest signals. In the scorpionfly Panorpa vulgaris, both sexes show mating preferences on the basis of the condition of the potential partners. Females prefer males that produce nuptial gifts (i.e. salivary secretions) during copulation, while males invest more nuptial gifts in females of high nutritional status. Both characters, males' ability to produce nuptial gifts and high nutritional status of females, are known to be reliable indicators of foraging ability. Thus, besides possible direct benefits, both sexes might also obtain indirect benefits in terms of “good foraging genes” by their choice and thereby increase the fitness of their offspring. A prerequisite for this possibility is the heritability of the respective trait. In the present study, we estimated the repeatability and the heritability of foraging ability. Our results indicate (1) a significant repeatability of individual foraging efficiencies in males and females and (2) a heritable component of this trait by a significant parent–offspring regression. These findings suggest that genetic benefits in terms of increased offspring foraging ability might contribute to selection for mating preferences in both sexes.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号