全文获取类型
收费全文 | 4595篇 |
免费 | 30篇 |
国内免费 | 49篇 |
专业分类
安全科学 | 109篇 |
废物处理 | 203篇 |
环保管理 | 587篇 |
综合类 | 683篇 |
基础理论 | 1498篇 |
环境理论 | 4篇 |
污染及防治 | 1015篇 |
评价与监测 | 318篇 |
社会与环境 | 252篇 |
灾害及防治 | 5篇 |
出版年
2023年 | 22篇 |
2022年 | 22篇 |
2021年 | 31篇 |
2020年 | 25篇 |
2019年 | 25篇 |
2018年 | 148篇 |
2017年 | 161篇 |
2016年 | 221篇 |
2015年 | 96篇 |
2014年 | 61篇 |
2013年 | 146篇 |
2012年 | 486篇 |
2011年 | 314篇 |
2010年 | 101篇 |
2009年 | 121篇 |
2008年 | 141篇 |
2007年 | 174篇 |
2006年 | 147篇 |
2005年 | 461篇 |
2004年 | 589篇 |
2003年 | 462篇 |
2002年 | 120篇 |
2001年 | 72篇 |
2000年 | 44篇 |
1999年 | 48篇 |
1998年 | 22篇 |
1997年 | 31篇 |
1996年 | 21篇 |
1995年 | 33篇 |
1994年 | 29篇 |
1993年 | 15篇 |
1992年 | 19篇 |
1991年 | 22篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1976年 | 6篇 |
1974年 | 8篇 |
1966年 | 5篇 |
1955年 | 5篇 |
1954年 | 8篇 |
排序方式: 共有4674条查询结果,搜索用时 15 毫秒
961.
Multiple behavioral and chemical studies indicate that ant nestmate recognition cues are low-volatile substances, in particular hydrocarbons (HCs) located on the cuticular surface. We tested the hypothesis that in the ant Camponotus fellah, nest environment, in particular nest volatile odors, can modulate nestmate-recognition-mediated aggression. Workers were individually confined within their own nest in small cages having either a single mesh (SM = limited physical contact permitted) or a double mesh (DM = exposed to nest volatiles only) screen. Individual workers completely isolated outside their nest (CI) served as control. When reintroduced into a group of 50 nestmates, the CI workers were attacked as alien ants after only 2 weeks of separation, whereas the SM workers were treated as nestmates even after 2 months of separation. Aggression towards DM ants depended on the period of isolation. Only DM workers isolated for over 2 months were aggressed by their nestmates, which did not significantly differ from the CI nestmates. Cuticular HC analyses revealed that the profile of the non-isolated ants (NI) was clearly distinct from that of CI, SM and DM ants. Profile differences matched the aggressive response in the case of CI ants but were uncorrelated in the case of SM or DM ants. This suggests that keeping the ants within the nest environment affected nestmate recognition in additional ways than merely altering their HC profile. Nest environment thus appears to affect label–template mismatch by modulating aggressive behavior, as well as the direction at which cuticular HCs diverged during the separation period. 相似文献
962.
Awgulewitsch A 《Die Naturwissenschaften》2003,90(5):193-211
963.
B.?H.?J.?De?JongEmail author A.?Hellier M.?A.?Castillo-Santiago R.?Tipper 《Mitigation and Adaptation Strategies for Global Change》2005,10(2):265-278
We present a methodology for testing and applying a regional baseline for carbon (C) emissions from land-use change, using a spatial modelling approach (hereafter called the Climafor approach). The methodology is based on an analysis of causal factors of previous land-use change (Castillo et al. 2005). Carbon risk matrices constructed from the spatial correlation analysis between observed deforestation and driving factors (Castillo et al. 2005), are used to estimate future carbonemissions within acceptable limits for a forest conservation project. The performance of two risk matrices were tested by estimating carbon emissions between 1975 and 1996 from randomly selected sample plots of sizes varying from 1,600 to 10,000 ha and comparing the results of the observed emissions from these sample plots with the model estimations. Expected emissions from continued land-use change was estimated for the community applying the risk matrices to the current land cover. The methodology provides an objective means of constructing baseline scenarios including confidence intervals, using the sum of variances of the various data sources, such as measured carbon densities, classification errors, errors in the risk matrices, and differences between the model prediction and observed emissions of sample plots due to sample size. The procedures applied in this study also give an indication of the impact of the variance in the various data sources on the size of the confidence intervals, which allows project developers to decide what data sources are essential to improve his baseline. The modelling approach to estimate the deforestation pattern is based on readily available cartographic and census data, whereas data on carbon densities are required to assess the potential for forest conservation projects to offset carbon emissions. 相似文献
964.
Passerine migrants require light from the blue-green part of the spectrum for magnetic compass orientation; under yellow light, they are disoriented. European robins tested under a combination of yellow light and blue or green light showed a change in behavior, no longer preferring their seasonally appropriate migratory direction: in spring as well as in autumn, they preferred southerly headings under blue-and-yellow and northerly headings under green-and-yellow light. This clearly shows that yellow light is not neutral and suggests the involvement of at least two types of receptors in obtaining magnetic compass information, with the specific interaction of these receptors being rather complex. 相似文献
965.
本文通过在东非进行的一系列野外和实验室试验,研究了丰富的红树林十足类螃蟹迈纳新胀蟹(Neosarmatium meinerti)对落叶的清理.在地势高的海榄雌(Avicennia meinerti)潮间带,螃蟹掩埋了所有红树林林区海底的落叶,而且会在2小时内平均消耗其中的67%. 相似文献
966.
Thiel V Blumenberg M Hefter J Pape T Pomponi S Reed J Reitner J Wörheide G Michaelis W 《Die Naturwissenschaften》2002,89(2):60-66
Hexactinellid sponges are often considered to be the most ancient metazoans. Lipid biomarkers from 23 species were studied for information on their phylogenetic properties, particularly their disputed relation to the two other sponge classes (Demospongiae, Calcarea). The most prominent lipid compounds in the Hexactinellida comprise C28 to C32 polyenoic fatty acids. Their structures parallel the unique patterns found in demosponge membrane fatty acids ('demospongic acids') and strongly support a close phylogenetic association of the Demospongiae and the Hexactinellida. Both taxa also show unusual mid-chain methylated fatty acids (C15-C25) and irregular C25- and C40-isoprenoid hydrocarbons, tracers for specific eubacteria and Archaea, respectively. These biomarkers indicate a similar, highly conservative symbiont community, although some shift in the abundance of the associated microbiota was observed. The lack of these features in calcareous sponges further contradicts the still common view that Calcarea and Demospongiae are more closely related to each other than either is to the Hexactinellida. 相似文献
967.
968.
969.
970.