全文获取类型
收费全文 | 1991篇 |
免费 | 17篇 |
国内免费 | 18篇 |
专业分类
安全科学 | 66篇 |
废物处理 | 86篇 |
环保管理 | 251篇 |
综合类 | 382篇 |
基础理论 | 436篇 |
环境理论 | 2篇 |
污染及防治 | 550篇 |
评价与监测 | 141篇 |
社会与环境 | 105篇 |
灾害及防治 | 7篇 |
出版年
2023年 | 20篇 |
2022年 | 30篇 |
2021年 | 36篇 |
2020年 | 23篇 |
2019年 | 31篇 |
2018年 | 53篇 |
2017年 | 43篇 |
2016年 | 53篇 |
2015年 | 56篇 |
2014年 | 62篇 |
2013年 | 84篇 |
2012年 | 87篇 |
2011年 | 122篇 |
2010年 | 92篇 |
2009年 | 123篇 |
2008年 | 108篇 |
2007年 | 116篇 |
2006年 | 76篇 |
2005年 | 73篇 |
2004年 | 89篇 |
2003年 | 64篇 |
2002年 | 75篇 |
2001年 | 56篇 |
2000年 | 38篇 |
1999年 | 23篇 |
1998年 | 28篇 |
1997年 | 27篇 |
1996年 | 27篇 |
1995年 | 30篇 |
1994年 | 21篇 |
1993年 | 13篇 |
1992年 | 18篇 |
1991年 | 17篇 |
1990年 | 21篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 17篇 |
1981年 | 7篇 |
1979年 | 10篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1970年 | 6篇 |
1968年 | 6篇 |
1965年 | 6篇 |
1962年 | 4篇 |
排序方式: 共有2026条查询结果,搜索用时 296 毫秒
181.
Detailed information is presented on the changes in lipid-class profiles (polar lipids, total neutral lipids, free sterols, steryl esters, triacylglycerols, neutral ether lipids and free fatty acids), which are manifest during the annual reproductive cycle of the seastarAsterias rubens for both the storage organs (pyloric caeca) and utilizing organs (ovaries). The ovaries appear to accumulate all individual lipid components proportional to progression of vitellogenesis. Pyloric caeca, in contrast, show variable lipid-class levels, probably due to more complex processes in these organs, operating simultaneously: digestion of food, accumulation of storage lipids, mobilization of stored lipids and their release. The results are discussed in terms of current knowledge on the role of lipids in echinoderm reproduction. 相似文献
182.
An important topic in the registration of pesticides and the interpretation of monitoring data is the estimation of the consequences of a certain concentration of a pesticide for the ecology of aquatic ecosystems. Solving these problems requires predictions of the expected response of the ecosystem to chemical stress. Up until now, a dominant approach to come up with such a prediction is the use of simulation models or safety factors. The disadvantage of the use of safety factors is a crude method that does not provide any insight into the concentration–response relationships at the ecosystem level. On the other hand, simulation models also have serious drawbacks like that they are often very complex, lack transparency, their implementation is expensive and there may be a compilation of errors, due to uncertainties in parameters and processes. In this paper, we present the expert model prediction of the ecological risks of pesticides (PERPEST) that overcomes these problems. It predicts the effects of a given concentration of a pesticide based on the outcome of already performed experiments using experimental ecosystems. This has the great advantage that the outcome is more realistic. The paper especially discusses how this model can be used to translate measured and predicted concentrations of pesticides into ecological risks, by taking data on measured and predicted concentrations of atrazine as an example. It is argued that this model can be of great use to evaluate the outcome of chemical monitoring programmes (e.g. performed in the light of the Water Framework Directive) and can even be used to evaluate the effects of mixtures. 相似文献
183.
184.
A. J. van der Graaf D. Bos M. J. J. E. Loonen M. Engelmoer R. H. Drent 《Journal of Coastal Conservation》2002,8(2):179-188
We studied the impact of livestock grazing on the distribution ofBranta bernicla bernicla (Dark-bellied Brent goose) in the Dutch Wadden Sea during spring. It was hypothesized that livestock facilitate short-term
(within-season) grazing for geese as well as long-term (over years). Therefore we measured grazing pressure by geese in salt
marsh and polder areas that were either grazed (spring-grazed) or ungrazed during spring (summer-grazed). Additionally, we
carried out a preference experiment with captive geese to test the preference between spring-grazed and summer-grazed polder
swards. We furthermore compared patterns of use by geese between long-term ungrazed and grazed salt marshes.
In May, there is a difference in grazing pressure by geese between polder pastures that are grazed or ungrazed during spring.
In this month, the ungrazed polder pastures are abandoned and the geese shift to either the grazed polder pastures or to the
salt marsh. Vegetation in the polder that had been spring-grazed had a lower canopy height and a higher tiller density than
summer-grazed vegetation. The captive geese in the preference experiment showed a clear preference for vegetation that had
been spring-grazed by sheep over ungrazed vegetation. Goose grazing pressure was negatively correlated to canopy height, both
on the polder and on the salt marsh. Within the plant communities dominated byFestuca rubra andPuccinellia maritima, marshes that were intensively grazed by livestock generally had higher grazing pressure by geese than long-term ungrazed
or lightly grazed salt marshes. 相似文献
185.
L. E. C. Conceição T. van der Meeren J. A. J. Verreth M. S. Evjen D. F. Houlihan H. J. Fyhn 《Marine Biology》1997,129(2):255-265
The present paper studied the influence of different food regimes on the free amino acid (FAA) pool, the rate of protein
turnover, the flux of amino acids, and their relation to growth of larval turbot (Scophthalmus maximus L.) from first feeding until metamorphosis. The amino acid profile of protein was stable during the larval period although
some small, but significant, differences were found. Turbot larvae had proteins which were rich in leucine and aspartate,
and poor in glutamate, suggesting a high leucine requirement. The profile of the FAA pool was highly variable and quite different
from the amino acid profile in protein. The proportion of essential FAA decreased with development. High contents of free
tyrosine and phenylalanine were found on Day 3, while free taurine was present at high levels throughout the experimental
period. Larval growth rates were positively correlated with taurine levels, suggesting a dietary dependency for taurine and/or
sulphur amino acids. Reduced growth rates in Artemia-fed larvae were associated with lower levels of free methionine, indicating that this diet is deficient in methionine for
turbot larvae. Leucine might also be limiting turbot growth as the different diet organisms had lower levels of this amino
acid in the free pool than was found in the larval protein. A previously presented model was used to describe the flux of
amino acids in growing turbot larvae. The FAA pool was found to be small and variable. It was estimated that the daily dietary
amino acid intake might be up to ten times the larval FAA pool. In addition, protein synthesis and protein degradation might
daily remove and return, respectively, the equivalent of up to 20 and 10 times the size of the FAA pool. In an early phase
(Day 11) high growth rates were associated with a relatively low protein turnover, while at a later stage (Day 17), a much
higher turnover was observed.
Received: 19 March 1997 / Accepted: 14 April 1997 相似文献
186.
187.
H. Brandenburg L. van der Zwan M. G. J. Jahoda Th. Stunen J. W. Wladimiroff 《黑龙江环境通报》1991,11(9):685-690
Ninety-six women of advanced maternal age were interviewed about the way they obtained information on prenatal diagnosis and about how the decision was made as to what procedure was to be performed (transabdominal chorionic villus sampling (TA-CVS) or amnio-centesis). In the CVS group, women visited their physician or midwife earlier in pregnancy (mean 7.1 weeks) than those in the amniocentesis group (mean 10.7 weeks). The availability of prenatal diagnosis was not mentioned during the first antenatal visit in 55 per cent of women from the amniocentesis group as opposed to 25 per cent from the TA-CVS group. Approximately 40 per cent of women eligible for prenatal diagnosis did not receive any information from the referring body prior to counselling at our centre. Only 29 per cent of women who underwent amniocentesis had actually chosen this procedure; 71 per cent were too late to undergo TA-CVS at 12 weeks. It is concluded that information to the patient must be improved in order to ensure early referral for prenatal diagnosis. 相似文献
188.
J. W. Wladimiroff M.D. Ph.D. M. F. Niermeijer J. J. Van Der Harten P. A. Stewart F. G. A. Versteegh W. Blom J. G. M. Huijmans 《黑龙江环境通报》1985,5(1):47-52
Congenital hypophosphatasia is an autosomal recessive disorder, which usually has a fatal outcome during the neonatal period. This report presents the prenatal diagnosis of hypophosphatasia at 16 weeks of gestation. The characteristic ultrasonic findings in this abnormality demonstrate the superiority of ultrasound as compared with radiography. 相似文献
189.
Although laboratory experiments show that non-aqueous phase liquid (NAPL) is retained in the unsaturated zone, no existing multiphase flow model has been developed to account for residual NAPL after NAPL drainage in the unsaturated zone. We developed a static constitutive set of saturation-capillary pressure relationships for water, NAPL and air that accounts for both this residual NAPL and entrapped NAPL. The set of constitutive relationships is formulated similarly to the set of scaled relationships that is frequently applied in continuum models. The new set consists of three fluid-phase systems: a three-phase system and a two-phase system, that both comply with the original constitutive model, and a newly introduced residual NAPL system. The new system can be added relatively easily to the original two- and three-phase systems. Entrapment is included in the model. The constitutive relationships of the non-drainable residual NAPL system are based on qualitative fluid behavior derived from a pore scale model. The pore scale model reveals that the amount of residual NAPL depends on the spreading coefficient and the water saturation. Furthermore, residual NAPL is history-dependent. At the continuum scale, a critical NAPL pressure head defines the transition from free, mobile NAPL to residual NAPL. Although the Pc-S relationships for water and total liquid are not independent in case of residual NAPL, two two-phase Pc-S relations can represent a three-phase residual system of Pc-S relations. A newly introduced parameter, referred to as the residual oil pressure head, reflects the mutual dependency of water and oil. Example calculations show consistent behavior of the constitutive model. Entrapment and retention in the unsaturated zone cooperate to retain NAPL. Moreover, the results of our constitutive model are in agreement with experimental observations. 相似文献
190.
Arbuscular mycorrhizal fungi can decrease the uptake of uranium by subterranean clover grown at high levels of uranium in soil 总被引:7,自引:0,他引:7
Rufyikiri G Huysmans L Wannijn J Van Hees M Leyval C Jakobsen I 《Environmental pollution (Barking, Essex : 1987)》2004,130(3):427-436
Subterranean clover inoculated or not with the arbuscular mycorrhizal (AM) fungus Glomus intraradices was grown on soil containing six levels of 238U in the range 0-87 mg kg(-1). Increasing U concentration in soil enhanced the U concentration in roots and shoots of both mycorrhizal and nonmycorrhizal plants but had no significant effects on plant dry matter production or root AM colonization. Mycorrhizas increased the shoot dry matter and P concentration in roots and shoots, while in most cases, it decreased the Ca, Mg and K concentrations in plants. The AM fungus influenced U concentration in plants only in the treatment receiving 87 mg U kg(-1) soil. In this case, U concentration in shoots of nonmycorrhizal plants was 1.7 times that of shoots of mycorrhizal plants. These results suggested that mycorrhizal fungi can limit U accumulation by plants exposed to high levels of U in soil. 相似文献