全文获取类型
收费全文 | 312篇 |
免费 | 28篇 |
国内免费 | 44篇 |
专业分类
安全科学 | 18篇 |
废物处理 | 3篇 |
环保管理 | 37篇 |
综合类 | 125篇 |
基础理论 | 157篇 |
污染及防治 | 20篇 |
评价与监测 | 7篇 |
社会与环境 | 6篇 |
灾害及防治 | 11篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 11篇 |
2020年 | 11篇 |
2019年 | 10篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 18篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 20篇 |
2010年 | 12篇 |
2009年 | 13篇 |
2008年 | 20篇 |
2007年 | 36篇 |
2006年 | 21篇 |
2005年 | 19篇 |
2004年 | 24篇 |
2003年 | 5篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 13篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 13篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有384条查询结果,搜索用时 296 毫秒
111.
地下储液罐抗爆炸地冲击作用的流固耦合有限元分析 总被引:1,自引:0,他引:1
储液罐的抗震性能虽然得到了较为深入的研究,但对其抗爆炸产生的地冲击作用的研究还十分罕见。本文通过建立流固耦合的数值分析模型,研究爆炸地冲击作用下地下立式储液罐的动力特性,包括储液晃动波高、罐壁的应力和应变、底板的提离和浮放储液罐的"象足"变形产生原因及破坏机理等。研究结果表明,储液罐在爆炸地冲击荷载和地震荷载作用下的动力响应有明显区别,地震荷载作用下的储液罐抗震验算方法不适用于爆炸地冲击荷载。 相似文献
112.
Behavioral and demographic changes following the loss of the breeding female in cooperatively breeding marmosets 总被引:3,自引:0,他引:3
C. Lazaro-Perea C. S. S. Castro R. Harrison A. Araujo M. F. Arruda C. T. Snowdon 《Behavioral ecology and sociobiology》2000,48(2):137-146
Recent models of the evolution and dynamics of family structure in cooperatively breeding vertebrates predict that the opening
of breeding vacancies in cooperatively breeding groups will result in (1) dispersal movements to fill the reproductive position,
and (2) within-group conflict over access to reproduction. We describe the behavioral and demographic changes that followed
the creation of breeding vacancies in three wild groups of cooperatively breeding common marmosets (Callithrix jacchus). Replacement of the breeding female was rapid when no adult females remained in the group, but did not occur for several
months when other adult females were present. Aggression of adult animals towards same-sex potential immigrants was associated
with a period of reduced affiliation, increased intragroup agonism, no intragroup sexual behavior, and frequent extragroup
copulations. This ended with the fissioning of groups along sexual lines. After replacement, multiple males copulated with
multiple females and vice versa, with no increases in sexually related aggression. Female-female conflict was resolved through
infanticide. The lack of direct conflict between males is consistent with cooperative polyandry. After a breeding vacancy
appeared, marmoset groups showed conflict of interests among group members similar to those shown by cooperatively breeding
birds, but they used different behavioral mechanisms to resolve those conflicts. Our data provide important evidence from
a cooperatively breeding mammal to support Emlen’s model for the evolution of vertebrate families, but they suggest that species-specific
inter- and intrasexual competitive strategies should be considered before the model can be applied to other cooperatively
breeding vertebrates.
Received: 23 November 1999 / Received in revised form: 28 March 2000 / Accepted: 1 April 2000 相似文献
113.
The effects of arsenic(As)were investigated on seed germination,root and shoot length and their biomass and some other factors to elucidate the toxicity of As.The results showed low concentrations of As(O-1 mg/kg)stimulated seed germination and the growth of root and shoot,however,these factors all decreased gradually at high concentrations of As(5-20 mg/kg).The contents Of O2-,MDA,soluble protein and peroxidase(POD)activity all increased with increasing As concentrations.Soluble sugar content,ascorbate peroxidase(APX),and superoxide dismutase(SOD)activities decreased at low concentrations of As,and increased at high concentrations of As.While acetylsalicylic acid(ASA)and chlorophyll contents,catalase(CAT)activity displayed increasing trend when the concentrations of As was lower than 1 mg/kg,and then decreasing trend.By polyacrylamide gel electrophoresis(PAGE).As induced the expression of POD isozymes of wheat seedlings.As induced the expression of CAT isozymes but inhibited the expression of SOD isozymes of wheat seedlings at concentrations lower than 1 mg/kg.However,As inhibited the expression of CAT isozymes but induced the expression of SOD isozymes at concentrations higher than 5 mg/kg.The results indicated As could exert harmfulness in the early development stage of wheat at inappropriate concentrations. 相似文献
114.
L. Star E. D. Ellen K. Uitdehaag F. W. A. Brom 《Journal of Agricultural and Environmental Ethics》2008,21(2):109-125
The combination of breeding for increased production and the intensification of housing conditions have resulted in increased
occurrence of behavioral, physiological, and immunological disorders. These disorders affect health and welfare of production
animals negatively. For future livestock systems, it is important to consider how to manage and breed production animals.
In this paper, we will focus on selective breeding of laying hens. Selective breeding should not only be defined in terms
of production, but should also include traits related to animal health and welfare. For this we like to introduce the concept
of robustness. The concept of robustness includes individual traits of an animal that are relevant for health and welfare.
Improving robustness by selective breeding will increase (or restore) the ability of animals to interact successfully with
the environment and thereby to make them more able to adapt to an appropriate husbandry system. Application of robustness
into a breeding goal will result in animals with improved health and welfare without affecting their integrity. Therefore,
in order to be ethically acceptable, selective breeding in animal production should accept robustness as a breeding goal.
L. Star, E. D. Ellen contributed equally to this work. Star belongs to the Adaptation Physiology Group, Wageningen University,
and the rest of the authors belong to the Animal Breeding and Genomics Centre, Wageningen University. 相似文献
115.
Abstract: The global amphibian crisis has resulted in renewed interest in captive breeding as a conservation tool for amphibians. Although captive breeding and reintroduction are controversial management actions, amphibians possess a number of attributes that make them potentially good models for such programs. We reviewed the extent and effectiveness of captive breeding and reintroduction programs for amphibians through an analysis of data from the Global Amphibian Assessment and other sources. Most captive breeding and reintroduction programs for amphibians have focused on threatened species from industrialized countries with relatively low amphibian diversity. Out of 110 species in such programs, 52 were in programs with no plans for reintroduction that had conservation research or conservation education as their main purpose. A further 39 species were in programs that entailed captive breeding and reintroduction or combined captive breeding with relocations of wild animals. Nineteen species were in programs with relocations of wild animals only. Eighteen out of 58 reintroduced species have subsequently bred successfully in the wild, and 13 of these species have established self‐sustaining populations. As with threatened amphibians generally, amphibians in captive breeding or reintroduction programs face multiple threats, with habitat loss being the most important. Nevertheless, only 18 out of 58 reintroduced species faced threats that are all potentially reversible. When selecting species for captive programs, dilemmas may emerge between choosing species that have a good chance of surviving after reintroduction because their threats are reversible and those that are doomed to extinction in the wild as a result of irreversible threats. Captive breeding and reintroduction programs for amphibians require long‐term commitments to ensure success, and different management strategies may be needed for species earmarked for reintroduction and species used for conservation research and education. 相似文献
116.
MICHAEL J. FORD§ JEFFREY J. HARD BRANT BOELTS† ERIC LaHOOD JASON MILLER 《Conservation biology》2008,22(3):783-794
Abstract: Captive breeding is a commonly used strategy for species conservation. One risk of captive breeding is domestication selection—selection for traits that are advantageous in captivity but deleterious in the wild. Domestication selection is of particular concern for species that are bred in captivity for many generations and that have a high potential to interbreed with wild populations. Domestication is understood conceptually at a broad level, but relatively little is known about how natural selection differs empirically between wild and captive environments. We used genetic parentage analysis to measure natural selection on time of migration, weight, and morphology for a coho salmon ( Oncorhynchus kisutch ) population that was subdivided into captive and natural components. Our goal was to determine whether natural selection acting on the traits we measured differed significantly between the captive and natural environments. For males, larger individuals were favored in both the captive and natural environments in all years of the study, indicating that selection on these traits in captivity was similar to that in the wild. For females, selection on weight was significantly stronger in the natural environment than in the captive environment in 1 year and similar in the 2 environments in 2 other years. In both environments, there was evidence of selection for later time of return for both males and females. Selection on measured traits other than weight and run timing was relatively weak. Our results are a concrete example of how estimates of natural selection during captivity can be used to evaluate this common risk of captive breeding programs. 相似文献
117.
金龙 《中国环境管理干部学院学报》2007,17(4):54-57
渔业环境权是渔业权人在得到许可的渔业水域从事养殖、捕捞等生产活动时所拥有的保护渔业水域环境的权利。根据物权理论,渔业环境权是一种基于国家对渔业水域的所有权上派生的用益物权,是《物权法》中养殖权和捕捞权的构成要件,它同养殖或捕捞水生动(植)物的所有权、对得到许可的水域(水体)的占有或使用权一起,构成完整的养殖权或捕捞权。这就是现行法律制度没有规定独立的渔业环境权的原因。 相似文献
118.
In many cooperatively breeding species, dominant females suppress reproduction in subordinates. Although it is commonly assumed
that aggression from dominant females plays a role in reproductive suppression, little is known about the distribution of
aggressive interactions. Here, we investigate the distribution of aggressive and submissive interactions among female meerkats
(Suricata suricatta). In this species, dominant females produce more than 80% of the litters, but older subordinates occasionally breed. Dominant
females commonly kill the pups of subordinates and usually evict older female subordinates from the group 1–3 weeks before
the birth of the dominant female's litter. The aggression frequency of the dominant female toward subordinates and the submission
frequency that each subordinate female showed to the dominant female increased as the age of the subordinate female increased
and as the birth of the dominant female's pups approached. Moreover, as birth approached, both of these behaviors intensified
more quickly between the dominant female and older subordinates than between the dominant female and younger subordinates.
The aggression frequency of the dominant female toward each subordinate female predicted whether that subordinate female was
evicted from the group; the submission frequency by each subordinate female predicted the timing of their eviction during
the pregnancy period of the dominant female. These results support the idea that conflict between dominant and subordinate
females increases with the age of subordinates and, since older subordinate females are most likely to reproduce, suggest
that dominant females may less easily control reproductive attempts by older subordinate females. 相似文献
119.
John S. Koreny Terry T. Fish 《Journal of the American Water Resources Association》2001,37(2):453-466
ABSTRACT: The deep aquifers of the Portland Basin are used as a regional water supply by at least six municipalities in Oregon and Washington. Maximum continuous use of the aquifers in 1998 was 13 mgd and peak emergency use was 55 mgd. Continuous use of the deep aquifers at a rate of 55 mgd has been proposed and inchoate water rights have been reserved for expansion of pumping to 121 mgd. A study was completed, using a calibrated ground water flow model, to evaluate the role of induced recharge from the Columbia River in mitigating aquifer drawdown from continuous‐use and expanded pumping scenarios in the center and eastern areas of the basin. The absolute average residual was less than 3.6 feet for steady‐state model calibrations, and less than 8.0 feet for transient calibration to a 42 mgd pumping event in 1987 with 170 feet of drawdown. Continuous use of the aquifers at a rate of 55 mgd is predicted to increase drawdown to 210 feet. Expansion of pumping to 121 mgd in the center basin is predicted to cause 400 feet of drawdown. However, expansion of pumping in the east basin is predicted to result in only 220 feet of drawdown because of induced recharge from the Columbia River. 相似文献
120.