全文获取类型
收费全文 | 99703篇 |
免费 | 1236篇 |
国内免费 | 1158篇 |
专业分类
安全科学 | 3972篇 |
废物处理 | 3791篇 |
环保管理 | 15005篇 |
综合类 | 21458篇 |
基础理论 | 27498篇 |
环境理论 | 73篇 |
污染及防治 | 19045篇 |
评价与监测 | 6048篇 |
社会与环境 | 4578篇 |
灾害及防治 | 629篇 |
出版年
2022年 | 833篇 |
2021年 | 847篇 |
2020年 | 664篇 |
2019年 | 878篇 |
2018年 | 1304篇 |
2017年 | 1352篇 |
2016年 | 2294篇 |
2015年 | 1855篇 |
2014年 | 2598篇 |
2013年 | 9280篇 |
2012年 | 2607篇 |
2011年 | 3233篇 |
2010年 | 3488篇 |
2009年 | 3652篇 |
2008年 | 2903篇 |
2007年 | 2745篇 |
2006年 | 2946篇 |
2005年 | 2808篇 |
2004年 | 3071篇 |
2003年 | 2962篇 |
2002年 | 2473篇 |
2001年 | 2945篇 |
2000年 | 2313篇 |
1999年 | 1678篇 |
1998年 | 1414篇 |
1997年 | 1407篇 |
1996年 | 1541篇 |
1995年 | 1644篇 |
1994年 | 1525篇 |
1993年 | 1369篇 |
1992年 | 1383篇 |
1991年 | 1352篇 |
1990年 | 1312篇 |
1989年 | 1254篇 |
1988年 | 1101篇 |
1987年 | 1028篇 |
1986年 | 1005篇 |
1985年 | 1082篇 |
1984年 | 1175篇 |
1983年 | 1179篇 |
1982年 | 1182篇 |
1981年 | 1106篇 |
1980年 | 946篇 |
1979年 | 957篇 |
1978年 | 833篇 |
1977年 | 727篇 |
1976年 | 651篇 |
1974年 | 643篇 |
1973年 | 675篇 |
1972年 | 678篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Molecular phylogeny and population structure of tideland snails in the genus Cerithidea around Japan
Phylogenetic relationships and genetic population structures were analyzed for tideland gastropods in the genus Cerithidea around Japan on the basis of partial sequence of the mitochondrial COI gene. Large genetic divergence was shown between individuals of Cerithidea cingulata in the southern Ryukyus and those in the central Ryukyus and the Japanese Islands. Haplotypes of C. cingulata from the Japanese Islands were paraphyletic with the exclusion of a monophyletic group from the central Ryukyus. Genetic differentiation of C. cingulata was also detected between Amami-Oshima Island and Okinawajima Island. No genetic divergence was found between Cerithidea rhizophorarum in the Japanese Islands and its subspecies C. rhizophorarum morchii in the Ryukyu Islands. The lack of genetic divergence of Cerithidea largillierti between continental China and Japan suggests relatively recent migration between the Japanese Islands and the Asian continent. For all three Cerithidea species distributed in both the Japanese Islands and the Ryukyu Islands, the Tokara Gap and the Kerama Gap were shown to have acted as barriers to the dispersal. 相似文献
82.
83.
84.
Daniel H Zitomer Prasoon Adhikari Craig Heisel Dennis Dineen 《Water environment research》2008,80(3):229-237
Codigestion of five wastes and municipal wastewater sludge was evaluated using full-scale testing. Synergistic, antagonistic, and neutral outcomes were observed depending on codigestate identity and concentration, highlighting the value of careful blending. Yeast waste resulted in notable synergism, increasing biogas production by over 50%, whereas aircraft deicing waste resulted in antagonism at high loadings and neutral outcomes at lower loadings. Restaurant waste codigestion resulted in neutral outcomes. The synergisim with yeast codigestates may have resulted from trace nutrients (i.e., iron, nickel, and cobalt) in the wastes that increased microbiological activity. Antagonist outcomes with deicing waste may have been the result of organic overload or inhibitory deicer constituents. Codigestion of wastes at the feed rates investigated was estimated to produce 0.50 ML/d of methane having an energy equivalent of 17 500 MJ/d. This was estimated to reduce net carbon dioxide emissions by 560 tonnes/y. 相似文献
85.
86.
87.
88.
89.
Schaefer CE do Amaral EF de Mendonça BA Oliveira H Lani JL Costa LM Fernandes Filho EI 《Environmental monitoring and assessment》2008,140(1-3):279-289
The relationships between soils attributes, soil carbon stocks and vegetation carbon stocks are poorly know in Amazonia, even
at regional scale. In this paper, we used the large and reliable soil database from Western Amazonia obtained from the RADAMBRASIL
project and recent estimates of vegetation biomass to investigate some environmental relationships, quantifying C stocks of
intact ecosystem in Western Amazonia. The results allowed separating the western Amazonia into 6 sectors, called pedo-zones:
Roraima, Rio Negro Basin, Tertiary Plateaux of the Amazon, Javari-Juruá-Purus lowland, Acre Basin and Rondonia uplands. The
highest C stock for the whole soil is observed in the Acre and in the Rio Negro sectors. In the former, this is due to the
high nutrient status and high clay activity, whereas in the latter, it is attributed to a downward carbon movement attributed
to widespread podzolization and arenization, forming spodic horizons. The youthful nature of shallow soils of the Javari-Juruá-Purus
lowlands, associated with high Al, results in a high phytomass C/soil C ratio. A similar trend was observed for the shallow
soils from the Roraima and Rondonia highlands. A consistent east–west decline in biomass carbon in the Rio Negro Basin sector
is associated with increasing rainfall and higher sand amounts. It is related to lesser C protection and greater C loss of
sandy soils, subjected to active chemical leaching and widespread podzolization. Also, these soils possess lower cation exchangeable
capacity and lower water retention capacity. Zones where deeply weathered Latosols dominate have a overall pattern of high
C sequestration, and greater than the shallower soils from the upper Amazon, west of Madeira and Negro rivers. This was attributed
to deeper incorporation of carbon in these clayey and highly pedo-bioturbated soils. The results highlight the urgent need
for refining soil data at an appropriate scale for C stocks calculations purposes in Amazonia. There is a risk of misinterpreting
C stocks in Amazonia when such great pedological variability is not taken into account. 相似文献
90.
Jean-Pierre Franzidis Martin Héroux Miroslav Nastev Christophe Guy 《Waste management & research》2008,26(2):121-131
An evaluation of lateral landfill gas migration was carried out at the Saint-Michel Environmental Complex in Montreal, City of Montreal Landfill Site, Canada, between 2003 and 2005. Biogas concentration measurements and gas-pumping tests were conducted in multilevel wells installed in the backfilled overburden beside the landfill site. A migration event recorded in autumn 2004 during the maintenance shutdown of the extraction system was simulated using TOUGH-LGM software. Eleven high-density instantaneous surface monitoring (ISM) surveys of methane were conducted on the test site. Gas fluxes were calculated by geostatistical analyses of ISM data correlated to dynamic flux chamber measurements. Variograms using normal transformed data showed good structure, and kriged estimates were much better than inverse distance weighting, due to highly skewed data. Measurement-based estimates of yearly off-site surface emissions were two orders of magnitude higher than modelled advective lateral methane flux. Nucleodensimeter measurements of the porosity were abnormally high, indicating that the backfill was poorly compacted. Kriged porosity maps correlated well with emission maps and areas with vegetation damage. Pumping tests analysis revealed that vertical permeability was higher than radial permeability. All results suggest that most of the lateral migration and consequent emissions to the atmosphere were due to the existence of preferential flow paths through macropores. In December 2006, two passively vented trenches were constructed on the test site. They were successful in countering lateral migration. 相似文献