全文获取类型
收费全文 | 17089篇 |
免费 | 110篇 |
国内免费 | 90篇 |
专业分类
安全科学 | 336篇 |
废物处理 | 711篇 |
环保管理 | 2356篇 |
综合类 | 2617篇 |
基础理论 | 5019篇 |
环境理论 | 7篇 |
污染及防治 | 3575篇 |
评价与监测 | 1115篇 |
社会与环境 | 1468篇 |
灾害及防治 | 85篇 |
出版年
2022年 | 103篇 |
2021年 | 98篇 |
2020年 | 80篇 |
2019年 | 94篇 |
2018年 | 710篇 |
2017年 | 659篇 |
2016年 | 667篇 |
2015年 | 243篇 |
2014年 | 276篇 |
2013年 | 885篇 |
2012年 | 567篇 |
2011年 | 1226篇 |
2010年 | 805篇 |
2009年 | 925篇 |
2008年 | 1097篇 |
2007年 | 1344篇 |
2006年 | 458篇 |
2005年 | 508篇 |
2004年 | 381篇 |
2003年 | 463篇 |
2002年 | 484篇 |
2001年 | 487篇 |
2000年 | 357篇 |
1999年 | 214篇 |
1998年 | 150篇 |
1997年 | 159篇 |
1996年 | 163篇 |
1995年 | 190篇 |
1994年 | 192篇 |
1993年 | 160篇 |
1992年 | 133篇 |
1991年 | 170篇 |
1990年 | 166篇 |
1989年 | 158篇 |
1988年 | 116篇 |
1987年 | 115篇 |
1986年 | 120篇 |
1985年 | 93篇 |
1984年 | 119篇 |
1983年 | 113篇 |
1982年 | 118篇 |
1981年 | 109篇 |
1980年 | 96篇 |
1979年 | 112篇 |
1978年 | 73篇 |
1977年 | 76篇 |
1975年 | 76篇 |
1973年 | 74篇 |
1972年 | 65篇 |
1967年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
T. B. Kalinnikova I. A. Krasnoperova T. M. Gainutdinov S. V. Sadykova M. Kh. Gainutdinov 《Russian Journal of Ecology》2005,36(2):109-114
The thermal resistance of Daphnia magna Straus is a trait depending on the interaction between individuals. The group effect is expressed in D. magna as both a decrease in thermal resistance and a marked individual differentiation with respect to thermal resistance. Two types of interactions between individual D. magna have been found: (1) the release of an unidentified factor decreasing thermal resistance (without noticeably changing the phenotypic variability of this trait) into the medium and (2) a decrease in the thermal resistance of individuals poorly adapted to heat stress, with the thermal resistance of well-adapted individuals (determined by the dependence of thermal resistance on interactions between individuals) remaining the same or even slightly increasing.Translated from Ekologiya, No. 2, 2005, pp. 126–131.Original Russian Text Copyright © 2005 by Kalinnikova, Krasnoperova, T. Gainutdinov, Sadykova, M. Gainutdinov. 相似文献
992.
E. A. Zinov'ev 《Russian Journal of Ecology》2005,36(5):349-353
The ecotypic structure of two grayling species in Eurasia is considered. Based on original and published data, the development of ecological forms in water bodies of different kinds is analyzed. Parallelism in the emergence of highly similar forms in different sites of the ranges is demonstrated. Distinctive features of ecotypes and their internal structure are described. The causes and rate of establishment of forms with a short life cycle are discussed. 相似文献
993.
994.
995.
996.
M. M. Lambrechts A. Rieux M. -J. Galan M. Cartan-Son P. Perret J. Blondel 《Russian Journal of Ecology》2008,39(7):516-522
Although mistimed reproduction (i.e., time-lag between peak food supply and offspring food demand) has been attributed to
habitat modifications or climate change in recent avian investigations, earlier breeding parents have higher reproductive
success in many habitats. Here we compare first and second broods in great tits (Parus major L.) from two Mediterranean oak habitats differing significantly in the timing (about 5 weeks), but not the amount of caterpillar
supply required to rear chicks. The study indicates that both the extent of mistimed reproduction and the breeding date per se influence breeding performance in this study system.
The text was submitted by the authors in English. 相似文献
997.
Alexandra Bächtold Estevão Alves-Silva Lucas A. Kaminski Kleber Del-Claro 《Die Naturwissenschaften》2014,101(11):913-919
Ovipositing adult females of myrmecophilous lycaenids are expected to select plants based on ant presence in order to maximize the survivorship of immature stages. Usually, larvae feed ants with honey-like solutions and, in turn, ants ward off parasitoids. Nonetheless, a rarely investigated approach is whether ant partners can also extend their protective behavior towards lycaenids eggs. Here, we investigated the ant-related oviposition pattern of Allosmaitia strophius and Rekoa marius; then, we compared egg parasitism according to the presence of ants. Lycaenid oviposition and egg parasitism (in percent) were experimentally compared in ant-present and ant-excluded treatments. The study plant, Heteropterys byrsonimifolia, is an extrafloral nectaried shrub which supports several ant species. We sampled 280 eggs, of which 39.65 % belonged to A. strophius and 60.35 % to R. marius. Both lycaenids eggs were significantly more abundant on branches with ants, especially those with Camponotus crassus and Camponotus blandus, two ant species known to attend to lycaenids. A. strophius and R. marius parasitism was 4.5- and 2.4-fold higher, respectively, in ant-present treatments, but the results were not statistically significant. Our study shows that ant-mediated host plant selection in lycaenids might be much more widespread than previously thought, and not restricted to obligate myrmecophilous species. Tending ants may be inefficient bodyguards of lycaenid eggs, because unlike larvae which release sugared liquids, eggs do not offer obvious rewards to ants. Ants can ward off parasitoids of larvae, as observed elsewhere, but our findings show that positive ant–lycaenid interactions are conditional and depend on immature ontogeny. 相似文献
998.
Elles M. J. Boon Hélène B. Schlecht Peter Martin Geoff Daniels Rolf H. A. M. Vossen Johan T. den Dunnen Bert Bakker Rob Elles 《黑龙江环境通报》2007,27(10):932-937
Objectives To validate the use of Real Time PCR, a widely used technique that can detect very low levels of Y chromosomal sequence, and to assess the use of a highly sensitive PCR technique, pyrophosphorolysis-activated polymerisation (PAP), for fetal sex determination using free fetal DNA (ffDNA). Methods The fetal sex was determined by Real Time PCR in 58 pregnancies using ffDNA isolated from maternal plasma. In parallel with the Real Time PCR experiments, the presence of Y chromosome sequence was also determined using PAP on 54 isolated ffDNA samples. Results Both techniques detected Y chromosome sequence at very low levels with 98% specificity and 100% sensitivity (Real Time n = 44, PAP n = 54). Furthermore, the PAP technique was shown to be more robust than the Real Time PCR as none of the samples tested failed to meet the acceptance criteria. Combining the two techniques for male fetal sex detection from maternal blood plasma increases the sensitivity and specificity to 100% in this series. Conclusions This study shows that both Real Time PCR and PAP can be used for Y chromosome detection on ffDNA. Furthermore, by using PAP in combination with Real Time PCR more reliable early prenatal sexing can be performed using ffDNA. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
999.
Emo Chiellini Andrea Corti Salvatore D’Antone Norman C. Billingham 《Journal of Polymers and the Environment》2007,15(3):169-178
Most of the standardized biodegradation tests used to assess the ultimate biodegradation of environmentally degradable polymers
are based solely on the determination of net evolved carbon dioxide. However, under aerobic conditions, it has to be considered
that heterotrophic microbial consortia metabolize carbon substrates both to carbon dioxide and in the production of new cell
biomass. It is generally accepted that in the relatively short term, 50% of the carbon content of most organic substrates
is converted to CO2, with the remaining carbon being assimilated as biomass or incorporated into humus. The latter is particularly important
when the metabolism of the organic matter occurs in a soil environment. A straightforward relationship between the free-energy
content of a carbon substrate (expressed as the standard free-energy of combustion) and its propensity for conversion to new
microbial biomass rather than mineralization to CO2 has been established. This can potentially lead to underestimation of biodegradation levels of test compounds, especially
when they consist of carbon in a fairly low formal oxidation state and relatively high free-energy content. In the present
work, the metabolism of different kind of carbon substrates, especially in soil, is reviewed and compared with our own experimental
results from respirometric tests. The results show that conversion of highly oxidized materials, such as the commonly used
reference materials, cellulose or starch, to CO2 may be significantly overestimated. The addition of glucosidic material to soil leads to greatly increased respiration and
is accompanied by a very low conversion to biomass or humic substances. In contrast, relatively less oxidized substrates metabolize
more slowly to give both CO2 and biomass to an extent which may be significantly underestimated if glucosidic materials are used as the reference. The
need for an overall carbon balance taking into account both the carbon immobilized as biomass and that volatized as CO2 must be considered in standard respirometric procedures for assessing the biodegradability of slowly degrading macromolecules. 相似文献
1000.