全文获取类型
收费全文 | 238篇 |
免费 | 10篇 |
国内免费 | 5篇 |
专业分类
安全科学 | 6篇 |
废物处理 | 4篇 |
环保管理 | 60篇 |
综合类 | 41篇 |
基础理论 | 55篇 |
污染及防治 | 69篇 |
评价与监测 | 8篇 |
社会与环境 | 6篇 |
灾害及防治 | 4篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 3篇 |
2013年 | 23篇 |
2012年 | 14篇 |
2011年 | 11篇 |
2010年 | 10篇 |
2009年 | 11篇 |
2008年 | 7篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2004年 | 2篇 |
2003年 | 7篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有253条查询结果,搜索用时 222 毫秒
31.
32.
33.
34.
35.
36.
Mark C. Roberts 《Resources Policy》1988,14(4)
This paper explores the general reasons for the sudden decline in the growth of world metal demand which began after 1974 and continues to impact the metal industries. For all of the eight metals studied, except aluminium, the dominant cause of this atrophy in demand is the stagnation in total world economic growth, which has caused reduced demand for all goods and services. In addition, consumer preferences have shifted away from metal-intensive goods, further reducing the need for metals. However, materials substitutions and manufacturing technologies have continued to evolve towards lower use of metal in each product at much the same rate after 1974 as before. Therefore, these aspects do not explain the sudden shortfall after 1974 except in the case of aluminium which experienced a dramatic change during the energy crisis years. 相似文献
37.
D. Roberts 《Marine Biology》1972,16(2):119-125
The rate of uptake of Endosulfan by Mytilus edulis L. exposed to pesticide concentrations of 0.1, 0.5, and 1.0 mg/l, and its subsequent elution on removal to clean sea water, was investigated. Higher residue levels were recorded for mussels exposed to higher concentrations of the pesticide, but concentration factors were reduced. There was a rapid initial fall in tissue residue levels on transfer to clean sea water due, it is suggested, to elution of Endosulfan adsorbed on particulate matter assimilated in the gut. The spawning period was prolonged at higher concentrations and, at 1.0 mg/l, the onset of spawning was delayed, possibly due to interference with gamonic action. At 0.1 mg/l, the minor protraction of the spawning period may reflect the effect of experimental tank conditions. No seasonal trend was obvious, and there was an exaggeration of the expected fall in condition in mussels exposed to higher concentrations of Endosulfan. In controls, the expected seasonal trend was reduced. 相似文献
38.
A rapid, automated procedure has been used for differentiation and quantitative determination of siderite, calcite and dolomite, based on the different rates of dissolution of the three carbonate species when reacted with excess 5 mol/litre HCl. The method employs manometric measurements of acid-liberated CO2 with a membrane differential-pressure transducer coupled to a stripchart recorder. Tested on the three carbonate species, singly and in pairs, the technique is discriminatory, sensitive and relatively rapid.Contributions from the Department of Agronomy, University of Kentucky Agricultural Experiment Station in Lexington, and Institute for Mining and Minerals Research of the University of Kentucky. The investigation reported in this paper (No. 83-3-206) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director. 相似文献
39.
S. S. Cook J. L. Roberts G. M. Hallegraeff A. McMinn 《Journal of Coastal Conservation》2007,11(3):171-181
We assessed the potential impact of a proposed canal development in an estuarine sandflat at Ralphs Bay, Tasmania on intertidal
microalgal productivity and species composition, by comparing it over summer and winter seasons with a well- established (30 year
old) canal estate at Patterson Lakes, Victoria. Pulse amplitude modulation (PAM) fluorometry was used to generate a relative
measure of photosynthetic performance, which combined with microalgal chlorophyll biomass and irradiance provides an assessment
of potential primary productivity. We present a sophisticated mathematical model for calculating benthic microalgal production
and the contribution to total primary production, taking into account sediment light attenuation as estimated from sediment
grain size. Ralphs Bay had a total productive microalgal biomass of 44 mg chlorophyll a m−2 which was six times higher than Patterson Lakes, while the relative productivity of Ralphs Bay was four times greater compared
to Patterson Lakes where productivity was virtually absent in the subtidal zone of the canal waterway. Ralphs Bay exhibited
a more or less homogeneous spatial distribution of microphytobenthos biomass but this was subject to some seasonal variation
in species composition, abundance and productivity. By contrast, at Patterson Lakes biomass distribution, diversity and productivity
was highly spatially variable in the canal system in both seasons. Patterson Lakes exhibited 60% lower microphytobenthos species
richness than Ralphs Bay but little variation in species composition occurred between seasons in the canal estate. This suggests
that the dominant diatom species in Patterson Lakes, Pinnularia yarrensis, Gyrosigma balticum and Pleurosigma salinarum, are well adapted to the disturbance regime within the canal estate. The proposed canal development at Ralphs Bay is estimated
to cause a decrease in microalgal productivity by both reducing available marine substrate (66% reduction) and replacing productive
intertidal phytobenthic habitat with nonproductive canal substrate. These combine to cause a decline in productivity of 92%
with significant flow-on effects predicted for higher trophic levels such as migratory wading birds. 相似文献
40.
Invertebrates containing endosymbiotic dinoflagellate algae (zooxanthellae) retain excretory nitrogen, and many are able to take up ammonium from the surrounding seawater. However, the site of assimilation and role of nitrogen recycling between symbiont and host remains unclear. In the present study, ammonium uptake by the symbiotic sea anemone Anemonia viridis (Forskål) was examined by following the pathway of assimilation using 15N-enriched ammonium. Since zooxanthellae became enriched with 15N from ammonium at up to 17 times the rate of the host, they appear to be the primary site of assimilation. In the light, the rate of zooxanthellae enrichment at 20?M was twice that at 10?M, whereas the rate of host enrichment was not significantly affected by ammonium concentration. When anemones were incubated with [15N]ammonium in the dark, after 12?h without light the rate of enrichment was lowered in both zooxanthellae and host. However, while the enrichment of the host was significantly reduced when the light level was lowered from 300 to 150?μmol photons m?2?s?1, zooxanthellae enrichment was unchanged. Low molecular weight material from the zooxanthellae became enriched at 20 times the rate of that from the host, and enrichment was detected in the amino acids glutamate, glutamine, aspartate, alanine, glycine, phenylalanine, threonine, valine, tyrosine, and leucine from zooxanthellae. In the zooxanthellae, amino acids accounted for 65% of the total enrichment of low molecular weight material. Of the amino acids detected in zooxanthellae, over 90% of the enrichment was accounted for by glutamate, glutamine and aspartate. The enrichment of the amide group of glutamine was greater than that of the amine group of glutamate or glutamine, consistent with the glutamine synthetase/glutamine 2-oxoglutarate amidotransferase cycle as the mechanism of ammonium assimilation. To examine the flux of 15N from zooxanthellae to host, anemones were pulse-labelled with [15N]ammonium and then transferred to an unlabelled chase. Over a 2?h period there was no evidence for a flux of nitrogen from zooxanthellae to host. However, during the chase period, the enrichment of low molecular weight material declined and that of high molecular weight material increased in both zooxanthellae and host, indicating that protein was synthesized using 15N from ammonium in both components of the symbiosis. Again by using a pulse-chase system, it was found that glutamate was metabolised most rapidly by zooxanthellae, followed by (in order of decreasing rate of turnover) aspartate, alanine, glycine and valine (no data are available for glutamine). Unlike these amino acids, nitrogen was transferred to the essential amino acids phenylalanine and threonine, increasing their enrichment during the chase period. While recycled nitrogen is clearly important to this symbiosis, the mechanism by which it is cycled remains to be resolved. 相似文献