全文获取类型
收费全文 | 918篇 |
免费 | 6篇 |
国内免费 | 11篇 |
专业分类
安全科学 | 12篇 |
废物处理 | 33篇 |
环保管理 | 104篇 |
综合类 | 200篇 |
基础理论 | 239篇 |
环境理论 | 1篇 |
污染及防治 | 194篇 |
评价与监测 | 95篇 |
社会与环境 | 52篇 |
灾害及防治 | 5篇 |
出版年
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 21篇 |
2020年 | 7篇 |
2019年 | 13篇 |
2018年 | 26篇 |
2017年 | 33篇 |
2016年 | 36篇 |
2015年 | 36篇 |
2014年 | 22篇 |
2013年 | 66篇 |
2012年 | 43篇 |
2011年 | 140篇 |
2010年 | 30篇 |
2009年 | 25篇 |
2008年 | 53篇 |
2007年 | 37篇 |
2006年 | 32篇 |
2005年 | 31篇 |
2004年 | 28篇 |
2003年 | 20篇 |
2002年 | 35篇 |
2001年 | 17篇 |
2000年 | 7篇 |
1999年 | 13篇 |
1998年 | 5篇 |
1997年 | 13篇 |
1996年 | 3篇 |
1995年 | 8篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1983年 | 6篇 |
1973年 | 3篇 |
1964年 | 3篇 |
1959年 | 7篇 |
1957年 | 5篇 |
1955年 | 3篇 |
1929年 | 3篇 |
1926年 | 3篇 |
1925年 | 2篇 |
1924年 | 3篇 |
1923年 | 5篇 |
1921年 | 4篇 |
1920年 | 2篇 |
1916年 | 2篇 |
1913年 | 2篇 |
排序方式: 共有935条查询结果,搜索用时 234 毫秒
1.
A transition zone in the otoliths of orange roughy (Hoplostethus atlanticus) is described where annulus width decreases markedly. For fish sampled at spawning time, the relationship between gonad stage
and the presence or absence of a transition zone is consistent with the hypothesis that this zone marks the onset of maturity,
if allowance is made for some error in gonad staging and identification of the zone. Another data set from a non-spawning
area after the spawning season is not consistent with the hypothesis. However, these latter data are considered less reliable
because of the small size of the fish in the sample and difficulties in determining, outside the spawning season, whether
a fish has been reproductively active. This hypothesis was used to provide estimates of the median age (30 yr) and length
(31 cm) at the onset of maturity for the Chatham Rise, New Zealand population. These estimates are unaffected by the biases
associated with the usual ogive method of estimation.
Received: 27 June 1997 / Accepted: 1 July 1997 相似文献
2.
3.
4.
西印度洋(WIO)地区以其迷人的海岸带、丰富的海洋生物多样性以及富饶的海洋和海岸带资源而著称.但是地处WIO地区的许多国家像肯尼亚、莫桑比克、索马里、南非、坦桑尼亚、科摩罗、马达加斯加、毛里求斯、留尼旺、塞舌尔等却极度贫困,特别是近二三十年以来,该地区的环境退化现象以及自然资源和生物多样性的下降越来越明显. 相似文献
5.
6.
7.
Pinard Michelle Putz Francis 《Mitigation and Adaptation Strategies for Global Change》1997,2(2-3):203-215
The Reduced-Impact Logging Project, a pilot carbon offset project, was initiated in 1992 when a power company provided funds to a timber concessionaire to implement timber-harvesting guidelines in dipterocarp forest. The rationale for the offset is that when logging damage is reduced, more, carbon is retained in living trees, and, because soil damage is minimized, forest productivity remains high. To estimate the carbon benefit associated with implementation of harvesting guidelines, a monitoring program was developed based on 1) field studies for measuring carbon stocks and flows; 2) a computer model of forest carbon dynamics for simulating various combinations of harvesting intensity and damage; and, 3) a projection model for calculating carbon balance over the project lifespan. Seventy-five percent of the carbon stored in this forest is in biomass, and of this, 59% is in large, trees (≧6- cm, diameter); consequently, reliable estimates of variables related to large trees are critical to the estimate of carbon benefits. Allometric methods for estimating belowground biomass are recommended over pit-sampling methods because of low cost-effectiveness of obtaining precise estimates of woody root biomass. Sensitivity analyses of variables used in the simulation model suggest that maintenance of ecosystem productivity has a large influence on long-term carbon storage in the forest. Projections of differences in carbon stores between the reduced-impact and conventional logging sites rely on assumptions about tree mortality, growth, and recruitment; published, data for comparable sites in Malaysia are probably appropriate for estimating forest recovery from conventional but not reduced-impact logging. Continuing field work is expected to provide the data needed to evaluate assumptions of the models. 相似文献
8.
9.
The Science of Nature - 相似文献
10.