全文获取类型
收费全文 | 847篇 |
免费 | 41篇 |
国内免费 | 69篇 |
专业分类
安全科学 | 100篇 |
废物处理 | 28篇 |
环保管理 | 96篇 |
综合类 | 236篇 |
基础理论 | 390篇 |
污染及防治 | 47篇 |
评价与监测 | 24篇 |
社会与环境 | 30篇 |
灾害及防治 | 6篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 14篇 |
2020年 | 15篇 |
2019年 | 10篇 |
2018年 | 8篇 |
2017年 | 19篇 |
2016年 | 24篇 |
2015年 | 21篇 |
2014年 | 24篇 |
2013年 | 35篇 |
2012年 | 41篇 |
2011年 | 54篇 |
2010年 | 48篇 |
2009年 | 56篇 |
2008年 | 70篇 |
2007年 | 72篇 |
2006年 | 80篇 |
2005年 | 55篇 |
2004年 | 41篇 |
2003年 | 42篇 |
2002年 | 23篇 |
2001年 | 21篇 |
2000年 | 28篇 |
1999年 | 31篇 |
1998年 | 23篇 |
1997年 | 20篇 |
1996年 | 20篇 |
1995年 | 18篇 |
1994年 | 12篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有957条查询结果,搜索用时 15 毫秒
31.
Soil and preen waxes influence the expression of carotenoid-based plumage coloration 总被引:1,自引:1,他引:0
The signaling function of carotenoid-based plumage is mainly determined by the concentration of pigments in feathers. For
this reason, most studies of the proximate control of coloration focus on processes during and preceding moult. In great tits
Parus major, past research demonstrates that carotenoid-based plumage coloration honestly indicates male quality and, thus, may be a
sexually selected signal. In this study, we investigate how dirt and preen oil influence the coloration of carotenoid-based
feathers in the great tit. We collected six feathers from each individual bird; three feathers served as controls while the
remaining three feathers were washed with a chloroform/methanol mixture to remove soil and preen waxes. We assessed plumage
coloration using digital photography. This cleaning procedure slightly enhanced ornamentation; the experimentally cleaned
feathers expressed hues shifted towards shorter wavelengths and expressed brighter overall coloration than control feathers.
This is the first experimental study conducted on wild birds demonstrating that, in addition to pigment concentration, the
presence of preen waxes and soils on feathers may contribute to variation in coloration. 相似文献
32.
Artificial neural network model for identifying taxi gross emitter from remote sensing data of vehicle emission 总被引:2,自引:0,他引:2
Vehicle emission has been the major source of air pollution in urban areas in the past two decades. This article proposes an artificial neural network model for identifying the taxi gross emitters based on the remote sensing data. After carrying out the field test in Guangzhou and analyzing various factors from the emission data, the artificial neural network modeling was proved to be an advisable method of identifying the gross emitters. On the basis of the principal component analysis and the selection of algorithm and architecture, the Back-Propagation neural network model with 8-17-1 architecture was established as the optimal approach for this purpose. It gave a percentage of hits of 93%. Our previous research result and the result from aggression analysis were compared, and they provided respectively the percentage of hits of 81.63% and 75%. This comparison demonstrates the potentiality and validity of the proposed method in the identification of taxi gross emitters. 相似文献
33.
34.
35.
36.
传统有机磷、有机氯农药具有高毒性、持久性和环境激素效应,处于痕量和超痕量浓度水平都可能给人类生命健康和生态环境带来严重威胁和风险。由于农药及其副产物的历史残留、累积及跨界迁移和分布,农药厂搬迁厂址用于房地产开发场地环评具有很大困难。结合南方某市一大型农药厂搬迁厂址用于房地产开发项目的案例,探讨了该类场地评价中基础资料的搜集方法和环评中应遵循的理念和原则。 相似文献
37.
合理地选择排水体制,是城市和工业企业排水系统规划和设计的重要问题.环境保护应是选择排水体制时所考虑的主要问题.排水体制的选择问题一直是学界和业界争论的热点问题之一.对不同排水体制的比较研究,有助于人们了解不同排水体制的优劣,从而选择最合适的排水体制.回顾国内外已有的对不同排水体制的比较研究,可以为以后的研究提供指导和参考. 相似文献
38.
39.
MATTHEW E. WOLAK GEORGE W. GILCHRIST VICTORIA A. RUZICKA DANIEL M. NALLY RANDOLPH M. CHAMBERS 《Conservation biology》2010,24(5):1268-1277
Abstract: Juvenile growth rate and adult body size are important components of life‐history strategies because of their direct impact on fitness. The diamondback terrapin (Malaclemys terrapin) is a sexually dimorphic, long‐lived turtle inhabiting brackish waters throughout the Atlantic and Gulf coasts of the United States. In parts of its range, terrapins face anthropogenically imposed mortality: juveniles of both sexes inadvertently enter commercial crab traps and drown. For adult females, the carapace eventually grows large enough that they cannot enter traps, whereas males almost never reach that critical size. We compared age structure, carapace dimensions, growth curves, and indices of sexual dimorphism for a Chesapeake Bay population of terrapins (where mortality of turtles is high due to crab traps) with contemporary terrapins from Long Island Sound and museum specimens from Chesapeake Bay (neither group subject to commercial crab traps). We also calculated the allochronic and synchronic rates of evolutionary change (haldanes) for males and females to measure the rate of trait change in a population or between populations, respectively. We found a dramatic shift to a younger male age structure, a decrease in the length of time to terminal female carapace size, a 15% increase in female carapace width, and an increase in sexual dimorphism in Chesapeake Bay. In a new twist, our results implicate a fishery in the selective increase in size of a reptilian bycatch species. These sex‐specific changes in life history and demography have implications for population viability that need to be considered when addressing conservation of this threatened turtle. 相似文献
40.
ADAM C. D. BARLOW CHRISTINA J. GREENWOOD ISHTIAQ U. AHMAD JAMES L. D. SMITH 《Conservation biology》2010,24(5):1338-1347
Abstract: Human–carnivore conflict is manifested in the death of humans, livestock, and carnivores. The resulting negative local attitudes and retribution killings imperil the future of many endangered carnivores. We tailored existing management tools to create a framework to facilitate the selection of actions to alleviate human–carnivore conflict and applied the framework to the human–tiger conflict in the Bangladesh Sundarbans. We identified potential actions that consider previous management efforts, local knowledge, cost‐effectiveness, fieldwork experience of authors and project staff, previous research on tiger ecology by the authors, and recommendations from human–carnivore conflict studies in other countries. Our framework includes creation of a profile to improve understanding of the nature of the conflict and its underlying causality. Identified actions include deterrents, education, direct tiger management, and response teams. We ranked actions by their potential to reduce conflict and the monetary cost of their implementation. We ranked tiger‐response teams and monitoring problem tigers as the two best actions because both had relatively high impact and cost‐effectiveness. We believe this framework could be used under a wide range of human–wildlife conflict situations because it provides a structured approach to selection of mitigating actions. 相似文献