全文获取类型
收费全文 | 2106篇 |
免费 | 8篇 |
国内免费 | 11篇 |
专业分类
安全科学 | 11篇 |
废物处理 | 80篇 |
环保管理 | 104篇 |
综合类 | 818篇 |
基础理论 | 446篇 |
污染及防治 | 458篇 |
评价与监测 | 117篇 |
社会与环境 | 80篇 |
灾害及防治 | 11篇 |
出版年
2017年 | 22篇 |
2016年 | 31篇 |
2015年 | 19篇 |
2014年 | 24篇 |
2013年 | 86篇 |
2012年 | 30篇 |
2011年 | 66篇 |
2010年 | 57篇 |
2009年 | 63篇 |
2008年 | 86篇 |
2007年 | 69篇 |
2006年 | 52篇 |
2005年 | 57篇 |
2004年 | 54篇 |
2003年 | 52篇 |
2002年 | 60篇 |
2001年 | 66篇 |
2000年 | 57篇 |
1999年 | 43篇 |
1998年 | 33篇 |
1997年 | 37篇 |
1996年 | 34篇 |
1995年 | 37篇 |
1994年 | 34篇 |
1993年 | 31篇 |
1992年 | 19篇 |
1991年 | 40篇 |
1990年 | 54篇 |
1989年 | 24篇 |
1988年 | 28篇 |
1987年 | 22篇 |
1985年 | 24篇 |
1984年 | 24篇 |
1983年 | 19篇 |
1982年 | 32篇 |
1979年 | 21篇 |
1977年 | 19篇 |
1974年 | 20篇 |
1972年 | 21篇 |
1967年 | 31篇 |
1966年 | 23篇 |
1965年 | 24篇 |
1963年 | 22篇 |
1962年 | 23篇 |
1961年 | 19篇 |
1960年 | 17篇 |
1959年 | 21篇 |
1958年 | 23篇 |
1957年 | 19篇 |
1955年 | 16篇 |
排序方式: 共有2125条查询结果,搜索用时 109 毫秒
291.
Numerous morphotypes and great abundances of resting stages falling within the meiobenthic size-range were found in meiobenthos
samples collected in a coastal lagoon of the North Adriatic Sea. Biodiversity, abundances and energetic values of both active
and inactive meiobenthic organisms were analysed by the traditional techniques of meiobenthology. Inactive stages were represented
by more than 100 morphotypes and formed 52% of the meiobenthos in terms of numbers of individuals. Inactive meiobenthos came
mostly from plankton: the second and third most abundant groups of all meiobenthic organisms were the eggs of a rotifer and
the cysts of a dinophyte, respectively. Resting stages of plankters fit the definition of temporary meiobenthos, making up
the “inactive temporary meiobenthos”, but they are usually not considered in meiobenthology. The diversity and abundance of
the meiobenthos is, thus, currently underestimated; this leads to neglect of the role of meiobenthos in several processes
linking different ecosystems. It is hypothesised, for instance, that the meiobenthic resting stages of planktonic organisms
(besides being the “seeds” for the perpetuation of planktonic communities) might also be the prey of meiofaunal organisms
with piercing mouth parts. If this proves correct, a regulatory role might be proposed for the meiofauna in respect to plankters
with benthic stages.
Received: 10 September 1998 / Accepted: 12 April 1999 相似文献
292.
The study presents 172 measurements of the uranium238U and234U isotopes in ground water and 21 measurements of these substances in the rivers of Eastern Germany. The uranium concentration in the ground water ranged from under 0.1 mBq/l to over 1000 mBg/l with a mean of 12 mBq/l. The respective activity relationships of234U/238U ranged from 0.85 to 12.6 with a mean of 1.66. A comparison of these values with those in the literature demonstrates an agreement with more recent measurements obtained from water in Thuringia and Saxony which were seen to have a mean value of 19 mBq/l. The activity relationships of234U/238U which were seen to be substantially over the equilibrial value of 1.0 and which were found in a quite high proportion of the samples must be taken into consideration when evaluating these. The measurements of river water demonstrated values for the Elbe river which are related to the periods of extensive uranium mining in Saxony and Thuringia. Measurements performed in the catchment regions going into the Baltic Sea revealed substantially higher values than would be expected from the distribution of uranium in these areas. A number of reasons are discussed here in an attempt to explain these findings. 相似文献
293.
294.
U. Sengutta 《Environmental Sciences Europe》1993,5(2):72-76
Clay minerals as major components of soils can adsorb heavy metals. The release of toxic heavy metals such as lead and cadmium into soil presents a serious problem. To evaluate the behaviour of these elements in the environment, it is necessary to develop methods which allow precise analysis of heavy metals. This article compares and optimizes AAS methods for lead and cadmium. 相似文献
295.
296.
297.
The plankton community in the Polar Front area of the Barents Sea was investigated during a cruise from 14 to 28 July 1987. The colonial algaePhaeocystis pouchetii andDinobryon pellucidum dominated the phytoplankton. Depth integrated carbon assimilation rates varied from 190 to 810 mg C m–2 d–1. A high carbon:chlorophyll ratio (which varied from 123 to 352) prevailed at the three stations investigated, which may relate to facultative heterotrophic behaviour byD. pellucidum. The herbivorous zooplankton community was dominated byCalanus glacialis, C. finmarchicus, andC. hyperboreus. Maximum zooplankton biomass was found in the same depth strata as phytoplankton chlorophyll maximum. The herbivorous copepod populations did not display consistent day-night vertical migration patterns. Phytoplankton consumption rates of the various life stages were estimated from the turnover rate of plant pigments in the gut. The gut defecation rate constant (R) varied from 0.014 to 0.027 min–1 at 0°C in copepodites (Stage II to adult female) ofC. glacialis, independent of developmental stage.Calanus spp. community carbon ingestion rates calculated from particulate carbon:chlorophyll ratios, were 10, 65 and 400% of daily phytoplankton carbon fixation rates at Stations 1, 2 and 3, respectively. 相似文献
298.
299.
During two expeditions of the R.V. Polarstern to the Arctic Ocean, pack ice and under-ice water samples were collected during two different seasons: late summer (September 2002) and late winter (March/April 2003). Physical and biological properties of the ice were investigated to explain seasonal differences in species composition, abundance and distribution patterns of sympagic meiofauna (in this case: heterotrophs >20 µm). In winter, the ice near the surface was characterized by extreme physical conditions (minimum ice temperature: –22°C, maximum brine salinity: 223, brine volume: 5%) and more moderate conditions in summer (minimum ice temperature: –5.6°C, maximum brine salinity: 94, most brine volumes: 5%). Conditions in the lowermost part of the ice did not differ to a high degree between summer and winter. Chlorophyll a concentrations (chl a) showed significant differences between summer and winter: during winter, concentrations were mostly <1.0 µg chl a l–1, while chl a concentrations of up to 67.4 µmol l–1 were measured during summer. The median of depth-integrated chl a concentration in summer was significantly higher than in winter. Integrated abundances of sympagic meiofauna were within the same range for both seasons and varied between 0.6 and 34.1×103 organisms m–2 in summer and between 3.7 and 24.8×103 organisms m–2 in winter. With regard to species composition, a comparison between the two seasons showed distinct differences: while copepods (42.7%) and rotifers (33.4%) were the most abundant sea-ice meiofaunal taxa during summer, copepod nauplii dominated the community, comprising 92.9% of the fauna, in winter. Low species abundances were found in the under-ice water, indicating that overwintering of the other sympagic organisms did not take place there, either. Therefore, their survival strategy over the polar winter remains unclear.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
300.