全文获取类型
收费全文 | 92774篇 |
免费 | 1244篇 |
国内免费 | 1128篇 |
专业分类
安全科学 | 3781篇 |
废物处理 | 3411篇 |
环保管理 | 14214篇 |
综合类 | 21276篇 |
基础理论 | 26678篇 |
环境理论 | 77篇 |
污染及防治 | 15546篇 |
评价与监测 | 5621篇 |
社会与环境 | 3965篇 |
灾害及防治 | 577篇 |
出版年
2022年 | 783篇 |
2021年 | 828篇 |
2020年 | 664篇 |
2019年 | 878篇 |
2018年 | 1223篇 |
2017年 | 1238篇 |
2016年 | 2239篇 |
2015年 | 1866篇 |
2014年 | 2602篇 |
2013年 | 9314篇 |
2012年 | 2279篇 |
2011年 | 2617篇 |
2010年 | 3378篇 |
2009年 | 3469篇 |
2008年 | 2150篇 |
2007年 | 2061篇 |
2006年 | 2430篇 |
2005年 | 2364篇 |
2004年 | 2666篇 |
2003年 | 2543篇 |
2002年 | 2079篇 |
2001年 | 2431篇 |
2000年 | 2082篇 |
1999年 | 1549篇 |
1998年 | 1394篇 |
1997年 | 1371篇 |
1996年 | 1505篇 |
1995年 | 1587篇 |
1994年 | 1494篇 |
1993年 | 1343篇 |
1992年 | 1337篇 |
1991年 | 1302篇 |
1990年 | 1251篇 |
1989年 | 1219篇 |
1988年 | 1059篇 |
1987年 | 996篇 |
1986年 | 997篇 |
1985年 | 1068篇 |
1984年 | 1163篇 |
1983年 | 1170篇 |
1982年 | 1179篇 |
1981年 | 1104篇 |
1980年 | 946篇 |
1979年 | 931篇 |
1978年 | 825篇 |
1977年 | 723篇 |
1976年 | 640篇 |
1974年 | 609篇 |
1973年 | 635篇 |
1972年 | 633篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
The cadmium binding properties of waters of the superior section of the Rio de la Plata estuarine were determined over a three-year period. Samples were collected at different hydrodynamic conditions. The complexing capacity was determined by square wave anodic stripping voltammetry (SWASV). Titration curve data were analyzed using a multivariable regression. Suspended particulate matter (SPM) was identified by XR diffraction and FTIR. These analyses showed that SPM principal components are clays (illite, montmorillonite and chlorite). The study was applied to the untreated, filtered and centrifuged fractions of each sample at the pH of the natural waters and at pH 1. The results show that the contribution of dissolved organic matter to the complexing capacity is negligible when compared with SPM. At natural pH, the complexing capacity of filtered and untreated fractions can be described by considering two kinds of binding sites. The associated conditional binding constants are independent of the concentration of suspended matter. Their average logarithms are ca. 6.5 and ca. 4.4. The total concentration of binding sites (S(T)) is in microM range, which is about three orders of magnitude higher than that reported for most of the studied estuaries. This difference is explained on the basis of the great amount of SPM. Hydrodynamic conditions produce variations in the concentration and composition of the SPM. At pH 1 samples still exhibit an important complexing capacity with only one binding site with log K(cond) ca. 5.4. These differences could be attributed to superficial modifications that take place at very low pH. 相似文献
123.
Ohne Zusammenfassung
Original erschienen in UWSF – Z Umweltchem ?kotox 20(2):133–144 (2008) DOI:
Herausgeber: Martin Pehnt und Eckard Helmers 相似文献
124.
In this paper, we investigate the presence of economies of scale in the global iron-making industry for integrated steel plants, iron making being the first stage in the steel-making process. Iron making depends on basic commodities, such as iron ore, coke and various forms of energy, required in the operation of the blast furnace, which can be classified as essential inputs and used in fixed proportions to produce iron. A generalized Leontief cost function is estimated using panel data for 69 integrated plants, such a specification being appropriate for technologies with essential inputs that are used in fixed proportions in production. A significant scale effect is observed due to the existence of fixed costs and a linear dependence of the cost function on production. Under a simple linear cost function, a rough estimate of the breakeven scale of plant, where costs equal revenue, is 4.5 Mt per year. Competitiveness, as measured by the ratio of plant average cost per tonne to best practice cost per tonne, can be shown to be positively related to the scale of production as well as the cost of essential inputs. Therefore, low-cost producers are also often producers with low raw material costs and production levels below the estimated breakeven scale of operation. Labor costs, although significant, are comparatively less important as a driver towards low costs. 相似文献
125.
Oritani Marsh in the Hackensack Meadowlands of urbanized northeastern New Jersey USA was assessed in 2000 for vegetation,
soil/sediment chemistry, abundance/diversity of benthic invertebrates, and bird and mammal usage. Vegetatively, both marsh
and uplands are dominated by tall, dense Phragmites australis. Small patches (less than 2 hectares total) dominated by Spartina spp. were found at the lowest elevations. Soil/sediment cores were sliced into 5 intervals and analyzed for metals, pesticides
and volatile/semivolatile organic compounds. Thirteen locations had at least one chemical above Long et al.’s [Environmental Management, 19, 1995, 81--97] “Effects Range-Median” (ERM). Seven metals and nine organics exceeded ERM in at least one sample, with mercury
showing the most exceedances. The surface 15 cm interval was generally more contaminated with metals than the 15 to 30 cm
interval; the reverse was true for semivolatile organic compounds. Twenty taxa of benthic macroinvertebrates were collected,
with each location producing from 1 to 9 taxa. Abundance ranged from 11 to 3,889 individuals/m2. Number of taxa was moderately (r
2 between 0.40 and 0.70) negatively correlated with zinc, beryllium, nickel and arsenic concentrations; no other chemical’s
r
2 was above 0.25. Diversity was moderately negatively correlated with arsenic and beryllium. These correlations were unexpected:
zinc, beryllium, nickel and arsenic were not the chemicals found at the highest concentrations relative to benchmarks. Number
of taxa, abundance and diversity were moderately (negatively) correlated with elevation; organic carbon was moderately (positively)
correlated with abundance. All other correlations were weak (r
2 < 0.35). Live traps captured only one mammal species, the meadow jumping mouse. Bird observations revealed 39 species, dominated
by a few common species. 相似文献
126.
127.
128.
129.
130.
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