全文获取类型
收费全文 | 859篇 |
免费 | 33篇 |
国内免费 | 11篇 |
专业分类
安全科学 | 45篇 |
废物处理 | 28篇 |
环保管理 | 181篇 |
综合类 | 159篇 |
基础理论 | 244篇 |
环境理论 | 3篇 |
污染及防治 | 150篇 |
评价与监测 | 47篇 |
社会与环境 | 35篇 |
灾害及防治 | 11篇 |
出版年
2023年 | 14篇 |
2022年 | 10篇 |
2021年 | 26篇 |
2020年 | 32篇 |
2019年 | 31篇 |
2018年 | 32篇 |
2017年 | 40篇 |
2016年 | 49篇 |
2015年 | 45篇 |
2014年 | 30篇 |
2013年 | 71篇 |
2012年 | 50篇 |
2011年 | 73篇 |
2010年 | 46篇 |
2009年 | 31篇 |
2008年 | 42篇 |
2007年 | 46篇 |
2006年 | 43篇 |
2005年 | 28篇 |
2004年 | 15篇 |
2003年 | 24篇 |
2002年 | 16篇 |
2001年 | 12篇 |
2000年 | 6篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有903条查询结果,搜索用时 78 毫秒
61.
Joe Shaw Elizabeth Scotchman Ben Paternoster Maureen Ramos Sarah Nesbitt Sophie Sheppard Tristan Snowsill Lyn S. Chitty Natalie Chandler 《黑龙江环境通报》2023,43(4):477-488
Objectives
To develop a flexible droplet digital PCR (ddPCR) workflow to perform non-invasive prenatal diagnosis via relative mutation dosage (RMD) for maternal pathogenic variants with a range of inheritance patterns, and to compare the accuracy of multiple analytical approaches.Methods
Cell free DNA (cfDNA) was tested from 124 archived maternal plasma samples: 88 cases for sickle cell disease and 36 for rare Mendelian conditions. Three analytical methods were compared: sequential probability ratio testing (SPRT), Bayesian and z-score analyses.Results
The SPRT, Bayesian and z-score analyses performed similarly well with correct prediction rates of 96%, 97% and 98%, respectively. However, there were high rates of inconclusive results for each cohort, particularly for z-score analysis which was 31% overall. Two samples were incorrectly classified by all three analytical methods; a false negative result predicted for a fetus affected with sickle cell disease and a false positive result predicting the presence of an X-linked IDS variant in an unaffected fetus.Conclusions
ddPCR can be applied to RMD for diverse conditions and inheritance patterns, but all methods carry a small risk of erroneous results. Further evaluation is required both to reduce the rate of inconclusive results and explore discordant results in more detail. 相似文献62.
We have found that foraging bumblebees (Bombus hortorum, B. pascuorum, B. pratorum and B.␣terrestris) not only avoid flowers of Symphytum officinale that have recently been visited by conspecifics but also those that have been recently visited by heterospecifics. We propose
that the decision whether to reject or accept a flower is influenced by a chemical odour that is left on the corolla by a
forager, which temporarily repels subsequent foragers. Honeybees and carpenter bees have previously been shown to use similar
repellent forage-marking scents. We found that flowers were repellent to other bumblebee foragers for approximately 20 min
and also that after this time nectar levels in S. officinale flowers had largely replenished. Thus bumblebees could forage more efficiently by avoiding flowers with low rewards. Flowers
to which extracts of tarsal components were applied were more often rejected by wild B. terrestris workers than flowers that had head extracts applied, which in turn were more often rejected than flowers that had body extracts
applied. Extracts from four Bombus species were equally repellent to foragers. The sites of production of the repellent scent and its evolutionary origins are
discussed.
Received: 24 November 1997 / Accepted after revision: 8 March 1998 相似文献
63.
Fish advisories for polychlorinated biphenyls (total-PCBs) and mercury are often given on a length-specific basis and fish sex is usually not considered. The relationship between concentration and length is well established for mercury, however its suitability for total-PCBs and the influence of sex over the large scale covered by most monitoring programs is not well known. Here we use what is perhaps the largest consistent sport fish contaminant dataset to evaluate the relationship between total-PCB/mercury and length and sex. We evaluated seven of the most commonly consumed fishes from the Canadian Great Lakes and two Ontario (Canada) inland lakes. For mercury, the relationship between concentration and length was significant (p<0.05) in most fish species and locations. For total-PCB, this relationship was also generally significant in Chinook salmon and lake trout, which are the species with the most advisories for this compound. In contrast, significant relationships were found less often for whitefish, northern pike, smallmouth bass, walleye, and especially yellow perch. However, mercury usually drives fish consumption advisories for these species. Overall, our results support the protocol of issuing contaminant advice on a length-specific basis in fish monitoring programs with reasonable confidence when at least a moderate number of samples over the natural size range of a species are included in the analysis. Sex differences were common for walleye (males>females, p<0.05) but not other species, suggesting that an equal number of male and female walleye should be used in deriving fish advisories for walleye. 相似文献
64.
65.
66.
67.
Fielding JL 《Disasters》2012,36(3):477-494
This paper explores the environmental inequalities of living in the floodplains of England and Wales and the differences in flood awareness of those 'at risk'. An area comparison is made between an etic, objective flood risk exposure, and an emic, subjective perception of that risk by social class. In all areas except the Midlands, the working classes were more likely to reside in the floodplains; the greatest exposure inequality is seen in the North East and Anglian regions. Flood awareness in the Anglian regions was much lower than average, but there were no significant class differences. In the Thames region, despite equal flood risk exposure between classes, the most deprived displayed the least awareness of flood risk. In the North East, inequalities in the distribution of flood risk exposure accompanied inequalities in perception, resulting in the least aware and most deprived experiencing the greatest flood risk. 相似文献
68.
69.
Agricultural opportunities to mitigate greenhouse gas emissions 总被引:15,自引:0,他引:15
Johnson JM Franzluebbers AJ Weyers SL Reicosky DC 《Environmental pollution (Barking, Essex : 1987)》2007,150(1):107-124
Agriculture is a source for three primary greenhouse gases (GHGs): CO(2), CH(4), and N(2)O. It can also be a sink for CO(2) through C sequestration into biomass products and soil organic matter. We summarized the literature on GHG emissions and C sequestration, providing a perspective on how agriculture can reduce its GHG burden and how it can help to mitigate GHG emissions through conservation measures. Impacts of agricultural practices and systems on GHG emission are reviewed and potential trade-offs among potential mitigation options are discussed. Conservation practices that help prevent soil erosion, may also sequester soil C and enhance CH(4) consumption. Managing N to match crop needs can reduce N(2)O emission and avoid adverse impacts on water quality. Manipulating animal diet and manure management can reduce CH(4) and N(2)O emission from animal agriculture. All segments of agriculture have management options that can reduce agriculture's environmental footprint. 相似文献
70.
Karen L. Stals Matthew Wakeling Júlia Baptista Richard Caswell Andrew Parrish Julia Rankin Carolyn Tysoe Garan Jones Adam C. Gunning Hana Lango Allen Lisa Bradley Angela F. Brady Helena Carley Jenny Carmichael Bruce Castle Deirdre Cilliers Helen Cox Charu Deshpande Abhijit Dixit Jacqueline Eason Frances Elmslie Andrew E. Fry Alan Fryer Muriel Holder Tessa Homfray Emma Kivuva Victoria McKay Ruth Newbury-Ecob Michael Parker Ravi Savarirayan Claire Searle Nora Shannon Deborah Shears Sarah Smithson Ellen Thomas Peter D. Turnpenny Vinod Varghese Pradeep Vasudevan Emma Wakeling Emma L. Baple Sian Ellard 《黑龙江环境通报》2018,38(1):33-43
针对传统教与学算法在解决复杂多峰函数优化问题时,具有局部最优且搜索开发能力较差的缺点,提出了一种改进的多学习教与学优化算法,新算法为学员的每一维加入不同的教学因子,设计了基于学员均值比较的教师选择策略和向教师及学员学习的多学习策略。基于多个单峰和多峰函数的仿真结果表明,新算法跟传统的、改进的教与学算法相比,在稳定性、寻优精度和收敛速度方面更具优势。 相似文献