全文获取类型
收费全文 | 2670篇 |
免费 | 76篇 |
国内免费 | 23篇 |
专业分类
安全科学 | 123篇 |
废物处理 | 109篇 |
环保管理 | 809篇 |
综合类 | 257篇 |
基础理论 | 631篇 |
环境理论 | 1篇 |
污染及防治 | 568篇 |
评价与监测 | 157篇 |
社会与环境 | 79篇 |
灾害及防治 | 35篇 |
出版年
2023年 | 14篇 |
2022年 | 20篇 |
2021年 | 28篇 |
2020年 | 20篇 |
2019年 | 32篇 |
2018年 | 50篇 |
2017年 | 46篇 |
2016年 | 61篇 |
2015年 | 53篇 |
2014年 | 53篇 |
2013年 | 287篇 |
2012年 | 107篇 |
2011年 | 137篇 |
2010年 | 110篇 |
2009年 | 119篇 |
2008年 | 155篇 |
2007年 | 144篇 |
2006年 | 126篇 |
2005年 | 95篇 |
2004年 | 77篇 |
2003年 | 97篇 |
2002年 | 86篇 |
2001年 | 56篇 |
2000年 | 45篇 |
1999年 | 24篇 |
1998年 | 43篇 |
1997年 | 28篇 |
1996年 | 38篇 |
1995年 | 46篇 |
1994年 | 31篇 |
1993年 | 44篇 |
1992年 | 36篇 |
1991年 | 15篇 |
1990年 | 23篇 |
1989年 | 17篇 |
1988年 | 24篇 |
1987年 | 15篇 |
1986年 | 19篇 |
1985年 | 28篇 |
1984年 | 23篇 |
1983年 | 24篇 |
1982年 | 34篇 |
1981年 | 34篇 |
1980年 | 32篇 |
1979年 | 21篇 |
1978年 | 23篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1974年 | 7篇 |
1972年 | 9篇 |
排序方式: 共有2769条查询结果,搜索用时 109 毫秒
361.
362.
Jennifer K. Schultz Richard L. Pyle Edward DeMartini Brian W. Bowen 《Marine Biology》2007,151(1):167-175
Color variation is used in taxonomic classification of reef fishes, but it may not reliably indicate evolutionary divergence.
In the central Pacific, there are three color morphs of the flame angelfish, Centropyge loriculus: a red morph that occurs primarily in the Hawaiian archipelago, the endemic Marquesan color morph with reduced black markings,
and an orange morph that occurs throughout the rest of Oceania. The red and orange morphs co-occur at Johnston Atoll (1,300 km
south of Hawai’i), but intermediate forms have not been reported. To determine whether the three color morphs represent distinct
evolutionary lineages, we compared 641 base pairs of mitochondrial cytochrome b. Forty-one closely related haplotypes were observed in 116 individuals. Analysis of molecular variance (AMOVA) indicated
no significant genetic structure among color morphs (ΦST = 0.011, P = 0.147). Likewise, there was no significant pairwise structure between sampling locations, separated by up to 5,700 km,
after a Bonferroni correction (ΦST = 0.000–0.080, P = 0.0130–0.999). Genetic studies in conjunction with larval distribution data indicate that Centropyge species are highly dispersive. While there is a strong geographic component to the distribution of color morphs in C. loriculus, we find no evidence for corresponding genetic partitioning. We do not rule out an adaptive role for color differentiation,
but our data do not support emerging species. 相似文献
363.
Dispersal Can Limit Local Plant Distribution 总被引:21,自引:0,他引:21
The ability of species to establish new populations at unoccupied sites is a critical feature in the maintenance of biological diversity, and it has taken on new importance as a result of global climate change and expected changes in species distribution. To examine the dispersal potential of plant species, seeds of four annual plant species were experimentally dispersed 40 to 600 m from existing populations in Massachusetts (U.S.A.) to 34 nearby unoccupied but apparently suitable sites. At three of these sites new populations were established that persisted for four generations and expanded slowly in area. At seven sites, a small initial population eventually died out. At the 24 other sites, new populations did not become established, indicating that the sites were in some way unsuitable, that not enough seeds arrived, or that conditions suitable for seed germination do not occur every year. These results suggest that some species may be unable to disperse naturally out of their existing ranges in response to global climate change, particularly if habitat fragmentation creates barriers to dispersal. These species may have to be assisted to reach suitable sites nearby to prevent their extinction in the wild. 相似文献
364.
365.
366.
367.
368.
369.
Kenneth L. Ladd Jr. Richard Chambers Sherry Kunka Dale Harmon 《Environment international》1981,6(1-6)
In October 1977, Southwestern Public Service Company executed a contract with the U.S. Environmental Protection Agency that called for a study to assess the performance of a fabric filter system installed on a large utility boiler that utilizes low sulfur Western coal. The project is now into its second year and the objectives of this paper are to describe the scope and intent of the study, as well as to report progress to date. In addition, some of the difficulties that we have encountered are discussed. Although some of these problems have resulted in procedural changes, the intent of the study has not been altered. This paper describes work being done in specific areas with which both the EPA and Southwestern are connected. These include fabric assessment, data collection, selection and installation of instrumentation, and overall fabric filter system performance. Results of the first performance test are also reviewed and the installation of a pilot baghouse is discussed. 相似文献