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   153篇
  免费   9篇
  国内免费   10篇
安全科学   7篇
废物处理   1篇
环保管理   55篇
综合类   34篇
基础理论   48篇
污染及防治   11篇
评价与监测   3篇
社会与环境   10篇
灾害及防治   3篇
  2022年   2篇
  2021年   5篇
  2020年   4篇
  2019年   6篇
  2018年   4篇
  2017年   5篇
  2016年   7篇
  2015年   2篇
  2014年   4篇
  2013年   15篇
  2012年   5篇
  2011年   9篇
  2010年   6篇
  2009年   11篇
  2008年   5篇
  2007年   6篇
  2006年   9篇
  2005年   9篇
  2004年   6篇
  2003年   5篇
  2002年   4篇
  2001年   4篇
  2000年   4篇
  1999年   9篇
  1998年   7篇
  1997年   5篇
  1996年   3篇
  1994年   1篇
  1993年   1篇
  1992年   3篇
  1991年   1篇
  1990年   1篇
  1988年   1篇
  1986年   1篇
  1979年   1篇
  1975年   1篇
排序方式: 共有172条查询结果,搜索用时 31 毫秒
91.
为了初步了解万亩果园湿地生态公园的野生动物种类及分布情况,采用线路调查为主,点面结合的方法对园内的野生动物展开调查.调查结果显示:该园中野生动物以鸟类为主,共有5目19科32种,且以雀形目为主.从食性来看,食虫鸟类最多,占万亩果园鸟类总数的53.1%.从居留型来看,鸟类以留鸟居多,共有28种,占总种数的87.5%.通过分析生态环境现状影响野生动物栖息的原因,提出了增加植被配置、设立相对封闭区域和加强农药使用管理的改善措施.  相似文献   
92.
为深入了解盐胁迫下外源硅(Si)对水稻生长的作用,采用溶液培养法研究了外源Si对盐(NaCl)胁迫下野生型水稻和硅突变体水稻(不能正常吸收Si)营养元素和生理指标的影响.结果表明:1)外源Si可显著提高盐胁迫下两种水稻的生物量.当NaCl的浓度为100mmol·L-1时,添加1.0mmol·L-1的Si可使野生型水稻茎叶和根系干重提高12.81%和15.25%,硅突变体水稻茎叶干重提高12.31%.2)外源Si可提高盐胁迫下两种水稻茎叶和根系中营养元素含量,降低Na的含量.3)外源Si可显著降低盐胁迫下野生型水稻叶片MDA含量,但对突变体水稻叶片MDA含量影响不大.4)外源Si可显著提高盐胁迫下两种水稻的根系活力.盐胁迫下,与不加Si的对照相比,添加1.0mmol·L-1的Si可分别使野生型和突变体水稻根系活力指数提高60.47%和42.42%.  相似文献   
93.
以栽培大豆和野生大豆的基因组DNA为材料,利用PCR技术扩增并克隆了豆类胰岛素基因,分析了两者的DNA序列.结果表明,测定的DNA序列分别为841bp和903bp,有4个核苷酸差异;在信号肽编码区域内各存在一个内含子,大小分别为368和370个核苷酸;在ORF范围内,与前人报导的cDNA序列分别有1个和2个位点的核苷酸差异,从而导致相应位点的氨基酸发生变化.Southern杂交表明,栽培大豆和野生大豆的豆类胰岛素基因分别以单拷贝和多拷贝形式存在于基因组中  相似文献   
94.
研究了青岛崂山野生草本药用花卉的生物学特征、生态分布、观赏及药用价值 ,讨论了它们的开发利用途径 ,以期为青岛崂山野生草本药用花卉的合理开发和持续利用提供可靠、详实的依据。  相似文献   
95.
Since the solubilization of meat and bone meal (MBM) is a prerequisite in many MBM disposal approaches, enhancement of the solubilization by means of thermochemical pretreatment was investigated in this study at two temperatures (55°C and 131°C) and six sodium hydroxide (NaOH) concentrations (0, 1.25, 2.5, 5, 10 and 20 g/L). The MBM volatile solid (VS) reduction ratio was up to 66% and 70% at 55°C and 131°C, respectively. At the same temperature, the VS reduction ratio increased with the increase in the dosage of NaOH. The study on the methane (CH4) production potential of pretreated MBM shows that the addition of NaOH at 55°C did not cause the inhibition of the succeeding CH4 production process. However, CH4 production was inhibited by the addition of NaOH at 131°C. The CH4 production potential was in the range of 389 to 503 mL CH4/g VS MBM and 464 to 555 mL CH4/g VS MBM at 55°C and 131°C, respectively.  相似文献   
96.
In 2016, Swedish climate reporting declined in quantity and shifted focus somewhat from climate change as such to the harmful climate impacts of meat consumption. The latter prompted discussions in social media—an increasingly important forum for public debate but infrequently studied in environmental communication research. Despite strong evidence that a meat and dairy-based diet is harmful for the environment, meat consumption is increasing, and this qualitative study aims to—through the lens of social representation theory—contribute knowledge about how livestock production is legitimized in everyday discourse on Facebook. The article identifies representations that legitimize livestock production through polarization between (1) livestock production and other (environmental) issues, (2) environmentally “good” and “bad” countries, and (3) “reliable” and “unreliable” information. It concludes by discussing the influence of national ideology on the legitimization of livestock production and the potential of social media to counter the post-politicization of environmental issues.  相似文献   
97.
The aim of study was to determine 9 organic acids in nine aboveground and seven wood-growing wild edible mushroom species originated from an area under the direct influence of a busy trunk road in Poland. The organic acids in the extracts of samples were identified by reversed-phase column liquid chromatography (RPLC). The presented results show that all the mushroom species were characterized by high variation in the profile and content of the analyzed acids. Each of mushroom species contained oxalic acid, the profiles of the other acids strictly depended on mushroom species. Among aboveground species, the highest total content of organic acids was found in Lepista gilva (267.5 ± 26.6 mg g?1 dry weight (DW)), while Laccaria amethystina was characterized by the lowest content (37.7 ± 6.5 mg g?1 DW). Within wood-growing species, the highest content of organic acids was determined in Flammulina velutipes (171.9 ± 26.7 mg g?1 DW), whereas the lowest content (34.2 ± 2.9 mg g?1 DW) of the studied acids was observed in Grifola frondosa.  相似文献   
98.
以黄土高原区露天煤矿复垦地为对象,于2005年8月对准格尔旗黑岱沟露天煤矿1992-2005年复垦的364hm2排土场野生植物入侵的种类进行了调查与研究,分析了42个样地上不同野生植物侵入的多度、频度、侵入规律及对生态系统的影响.结果表明:1992-2005年的近15年中,共有115种野生植物自然侵入到排土场内,群落中以1年生植物占优势(>50%),但多年生植物已比复垦初期(<5%)增加了很多,在组成上约占总种数的40%~50%,多度高的植物已有多年生植物,且分布于植物群落中.影响复垦植被生长的主要侵入种是披碱草和拂子茅.复垦地野生杂草侵入,表现为①平台侵入种数>边坡侵入种数,阴坡侵入种数>阳坡侵入种数;②纯林侵入种数>混交林侵入种数;③沙棘灌丛侵入种数>油松侵入种数>杨树林侵入种数;④黄土覆盖区侵入种数>土石混排区侵入种数.   相似文献   
99.
Abstract: A sea cage, sometimes referred to as a net pen, is an enclosure designed to prevent farm fish from escaping and to protect them from large predators, while allowing a free flow of water through the cage to carry away waste. Farm fish thus share water with wild fish, which enables transmission of parasites, such as sea lice, from wild to farm and farm to wild fishes. Sea lice epidemics, together with recently documented population‐level declines of wild salmon in areas of sea‐cage farming, are a reminder that sea‐cage aquaculture is fundamentally different from terrestrial animal culture. The difference is that sea cages protect farm fish from the usual pathogen‐control mechanisms of nature, such as predators, but not from the pathogens themselves. A sea cage thus becomes an unintended pathogen factory. Basic physical theory explains why sea‐cage aquaculture causes sea lice on sympatric wild fish to increase and why increased lice burdens cause wild fish to decline, with extirpation as a real possibility. Theory is important to this issue because slow declines of wild fish can be difficult to detect amid large fluctuations from other causes. The important theoretical concepts are equilibrium, host‐density effect, reservoir‐host effect, and critical stocking level of farmed fish (stocking level at which lice proliferate on farm fish even if wild fish are not present to infect them). I explored these concepts and their implications without mathematics through examples from salmon farming. I also considered whether the lice‐control techniques used by sea‐cage farmers (medication and shortened grow‐out times) are capable of protecting wild fish. Elementary probability showed that (where W is the abundance of wild fish, W* is the prefarm abundance, F is the abundance of farm fish, and is the ratio of lice per farm fish to lice per wild fish). Declines of wild fish can be reduced by short growing cycles for farm fish, medicating farm fish, and keeping farm stocking levels low. Declines can be avoided only by ensuring that wild fish do not share water with farmed fish, either by locating sea cages very far from wild fish or through the use of closed‐containment aquaculture systems. These principles are likely to govern any aquaculture system where cage‐protected farm hosts and sympatric wild hosts have a common parasite with a direct life cycle.  相似文献   
100.
泰山植物资源丰富,共有野生种子植物107科401属762种。本文按经济用途将泰山的资源植物主要分为11类,提出了对它们进行合理开发利用的措施  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