全文获取类型
收费全文 | 693篇 |
免费 | 10篇 |
国内免费 | 11篇 |
专业分类
安全科学 | 47篇 |
废物处理 | 7篇 |
环保管理 | 192篇 |
综合类 | 111篇 |
基础理论 | 239篇 |
环境理论 | 4篇 |
污染及防治 | 39篇 |
评价与监测 | 21篇 |
社会与环境 | 29篇 |
灾害及防治 | 25篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 14篇 |
2020年 | 6篇 |
2019年 | 22篇 |
2018年 | 14篇 |
2017年 | 16篇 |
2016年 | 32篇 |
2015年 | 19篇 |
2014年 | 22篇 |
2013年 | 31篇 |
2012年 | 11篇 |
2011年 | 31篇 |
2010年 | 19篇 |
2009年 | 64篇 |
2008年 | 54篇 |
2007年 | 57篇 |
2006年 | 55篇 |
2005年 | 28篇 |
2004年 | 27篇 |
2003年 | 17篇 |
2002年 | 13篇 |
2001年 | 11篇 |
2000年 | 21篇 |
1999年 | 17篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有714条查询结果,搜索用时 500 毫秒
371.
Many different approaches for national sustainable development strategies (NSDS) have been proposed since 1992, with some components common to all. A country's national strategy should be designed to help mainstream environmental concerns into policy. More broadly, it should coordinate local policy with global concerns, as well as integrate scientific knowledge into policy and development planning. The peer review mechanism for national strategies was piloted by France, and also involved representatives of countries from the North and the South as well as stakeholders. The peer review process allows countries to share their experience and information, and can assist them in identifying their own path to sustainable development. The business community can also contribute to sustainable development through provision of local and global public goods. Another input to sustainable development could come from the International Organization for Standardization (ISO) and its Guidance Standard on Social Responsibility (ISO 26000), as a coordinating mechanism between voluntary initiatives and binding obligations (such as international conventions). ISO standards and guidelines should therefore be integrated with national sustainable development strategies and local Agenda 21 frameworks. 相似文献
372.
373.
以《量和单位》(GB3100-3102-1993)为依据,列举了各种常见的错误使用量和单位的名称和符号、量和单位非标准化的例子,对其进行了分析和探讨,提出标准化对策。 相似文献
374.
The potential for reproductive conflict among colony members exists in all social insect societies. For example, queens and
workers may be in conflict over the production of males within colonies. Kin selection theory predicts that in a colony headed
by a multiply-mated queen, worker reproduction is prevented by worker policing in the form of differential oophagy. However,
few studies have demonstrated that workers actually lay eggs within queenright colonies. The purpose of this study was to
determine if workers laid male eggs within unmanipulated queen-right colonies of the polyandrous social wasps Vespula maculifrons and V. squamosa. We focused our analysis on an unusual brood pattern within colonies, multiple egg cells. We were primarily interested in
determining if individuals reared in these irregular circumstances were queen or worker offspring. To address this question,
we genotyped 318 eggs from eight V. maculifrons and two V. squamosa colonies. No worker‑reproduction was detected in any of the queenright colonies; all of the eggs found in multiple egg cells were consistent
with being queen‑produced. However, the frequency of multiple egg cells differed among colonies, suggesting that queens vary
in the frequency of errors they make when laying eggs within cells. Finally, we suggest that workers may not be laying eggs
within queenright colonies and that worker reproduction may be controlled through mechanisms other than differential oophagy
in polyandrous Vespula wasps. 相似文献
375.
376.
Pavel Salz 《Journal of Coastal Conservation》1999,5(2):149-152
The aim of this paper is to explore the issue of problem definition in coastal (zone) management, with particular emphasis on social and institutional aspects. Do the existing scientific theories provide the necessary tools for open formulation of questions or problem definition, without preconceived ideas? Or are they rigid frameworks, which lead our curiosity along well-paved trails to predetermined results? Formulation of the right questions is probably the most important step in arriving at relevant answers. 相似文献
377.
In this study, we investigate association patterns of 249 bottlenose dolphin feeding groups off Sardinia Island (Italy) from
January 2000–May 2007 and describe how their association behaviour is related to their response to food patches created by
a marine fin fish farm. We also tested the hypothesis that dolphins have different social structures with different feeding
activities: Associations should decrease during opportunistic feeding behaviours as it is easier to capture prey, and cooperation
is not as necessary. Sixteen individually identified bottlenose dolphins were observed participating in both opportunistic
and not opportunistic feeding activities, with a mean of 30 ± 8 times and 9.6 ± 1 times, respectively. Bottlenose dolphins
show non-random social behaviour during feeding and this behaviour differs depending on their specific foraging activity.
Dolphin associations during feeding can be divided into three categories: acquaintances, affiliates, and feeding associates.
Association behaviour during fish farm feeding is consistent with our hypothesis that during opportunistic behaviours, benefits
from cooperation decrease, as it is easier to capture prey. Group size homogeneity in both feeding activities demonstrates
that the number of dolphins engaging in foraging is not necessarily related with cooperation levels. Moreover, an adult dolphin
may prefer to associate with a specific individual, independent of the sex, who shares the same foraging priorities. This
study is the first to show how aquaculture is not only directly affecting marine predators but could also indirectly affect
their social structure and behaviour. 相似文献
378.
Hormones play a central role in the physiology and behaviour of animals. The recent development of noninvasive techniques
has increased information on physical and social states of individuals through hormone measurements. The relationships among
hormones, life history traits and behaviours are, however, still poorly known. For the first time, we evaluated natural winter
glucocorticoid and testosterone levels in young ungulates in relation to winter progression, diet quality and social rank.
Overwinter, levels of glucocorticoid and testosterone decreased, possibly due to the decline of fawns’ body mass. The relationships
between hormone levels and diet quality were surprising: Fawns fed the control diet presented higher glucocorticoid and lower
testosterone levels then fawns fed the poor diet, suggesting that control fawns faced a higher nutritional stress than those
on the poor diet. Similarly to other studies on social mammals, we found no relationship between faecal glucocorticoid levels
and social rank, suggesting that social stress was similar for dominant and subordinate fawns during winter. Testosterone
levels were not correlated to social rank as found previously in groups of individuals forming stable social hierarchies and
maintaining stable dominance relationships. The simultaneous suppression of glucocorticoid and testosterone levels suggests
for the first time that young ungulates present a hormonal strategy to prevent fast depletion of limited proteins and fat
resources during winter. 相似文献
379.
Structure of the social network and its influence on transmission dynamics in a honeybee colony 总被引:4,自引:3,他引:1
Dhruba Naug 《Behavioral ecology and sociobiology》2008,62(11):1719-1725
Infectious processes in a social group are driven by a network of contacts that is generally structured by the organization
arising from behavioral and spatial heterogeneities within the group. Although theoretical models of transmission dynamics
have placed an overwhelming emphasis on the importance of understanding the network structure in a social group, empirical
data regarding such contact structures are rare. In this paper, I analyze the network structure and the correlated transmission
dynamics within a honeybee colony as determined by food transfer interactions and the changes produced in it by an experimental
manipulation. The study demonstrates that widespread transmission in the colony is correlated to a lower clustering coefficient
and higher robustness of the social network. I also show that the social network in the colony is determined by the spatial
distribution of various age classes, and the resulting organizational structure provides some amount of immunity to the young
individuals. The results of this study demonstrates how, using the honeybee colony as a model system, concepts in network
theory can be combined with those in behavioral ecology to gain a better understanding of social transmission processes, especially
those related to disease dynamics. 相似文献
380.
Theory predicts that frequent dyadic association should promote cooperation through kin selection or social tolerance. Here
we test the hypothesis that sex differences in the strength and stability of association preferences among free-ranging chimpanzees
conform to sex differences in cooperative behavior. Using long-term data from the Kanyawara chimpanzee (Pan troglodytes schweinfurthii) community (Kibale National Park, Uganda), we calculated indices of intra-sexual dyadic association over a 10-year period.
We found that (1) male–male dyads had significantly stronger association indices than female–female dyads, (2) the pattern
of association preferences in both sexes changed little over the entire study period, and (3) when comparing periods with
different alpha males, changes in association strength were more frequent among males. These results demonstrate that both
the strength and stability of association patterns are important components of social relationships. Male chimpanzees, which
are characterized by frequent cooperation, had association preferences that were both strong and stable, suggesting that forming
long-term bonds is an important dominance strategy. However, the fact that male association patterns were sensitive to upheaval
in the male dominance hierarchy suggests that males also take advantage of a changing social climate when choosing association
partners. By contrast, the overall strength of female associations was relatively weak. Female association preferences were
equally stable as males’; however, this reflected a dyad’s tendency to be found in the same party rather than to associate
closely within that party. Therefore, in this community, female association patterns appear to be more a consequence of individual
ranging behavior rather than a correlate of cooperation. 相似文献