全文获取类型
收费全文 | 404篇 |
免费 | 14篇 |
国内免费 | 9篇 |
专业分类
安全科学 | 19篇 |
废物处理 | 17篇 |
环保管理 | 93篇 |
综合类 | 39篇 |
基础理论 | 139篇 |
环境理论 | 1篇 |
污染及防治 | 72篇 |
评价与监测 | 31篇 |
社会与环境 | 16篇 |
出版年
2023年 | 5篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 14篇 |
2015年 | 13篇 |
2014年 | 13篇 |
2013年 | 28篇 |
2012年 | 19篇 |
2011年 | 32篇 |
2010年 | 19篇 |
2009年 | 19篇 |
2008年 | 26篇 |
2007年 | 33篇 |
2006年 | 26篇 |
2005年 | 7篇 |
2004年 | 19篇 |
2003年 | 13篇 |
2002年 | 10篇 |
2001年 | 12篇 |
2000年 | 4篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1974年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有427条查询结果,搜索用时 234 毫秒
41.
42.
43.
44.
Mahlon Craig Barber 《Ecological modelling》1978,5(2):125-135
Historic ecosystem resource flow is modeled as a retrospective discrete Markov chain to obtain the expected values and variances of compartmental residence times and numbers of intercompartmental transfers that compartmental standing crops have experienced since their latest entry into the ecosystem. The transition probabilities of the proposed retrospective Markovian model are either stationary or time inhomogeneous according to whether a steady state or non-steady state ecosystem, respectively, is analyzed. 相似文献
45.
Hung CL Xu Y Lam JC Jefferson TA Hung SK Yeung LW Lam MH O'Toole DK Lam PK 《Chemosphere》2006,63(5):845-852
The risks to Indo-Pacific Humpback Dolphins and Finless Porpoises associated with polychlorinated biphenyls (PCBs) were assessed. Stomach contents from twelve stranded Humpback Dolphins and sixteen stranded Finless Porpoises were collected. Concentrations of total and isomer-specific PCBs in the stomach contents were determined using dual-column gas chromatography equipped with electron capture detectors (GC-ECD). Risks due to the PCBs were assessed in three scenarios, based on total PCBs (summation of 41 PCB congeners), total toxicity equivalency (TEQs) and PCB 118, using the toxicity reference values (TRVs) as the threshold effects benchmarks. The calculated risk quotients (RQs) showed that risks due to PCBs were generally low or negligible. Specifically, RQs from total TEQs and total PCBs for Finless Porpoises are below one, suggesting that PCBs should be a low risk for the Finless Porpoise in Hong Kong waters. However, the Humpback Dolphin has RQs larger than 1 for total TEQs and total PCBs when the 95th percentile data were used in the evaluation. This indicates that further investigation may be needed to examine more closely the potential impact of toxic contaminants in the habitat of the Humpback Dolphin. 相似文献
46.
47.
Craig B. Stanford 《Behavioral ecology and sociobiology》1992,30(1):29-34
Summary Data from a 15-month field study of the capped langur monkey, Presbytis pileata, in Bangladesh indicate that allomothering behavior is restricted to particular female-infant dyads. Primary allomothers were all parous adult females; nulliparous females rarely allo-mothered, Newborn infants were transferred from the mother to other females within a short time of birth, as reported for some other colobine species, but over the first 3 months of life each neonate's contact with nonmothers was largely restricted to a single allomother in each of five study groups. Capped langur mothers with newborn infants spent more time feeding when the infant was being allomothered than when it was in the mother's care. The model of allomothering as a selfish behavior by nulliparous or pregnant females used to enhance maternal skills at the expense of mothers is not supported by this study. Rather, allomothering may have adaptive significance as altruistic behavior among group females, in that it enables lactating females to increase feeding time. Capped langur allomothering is best interpreted as a low-cost behavior that can benefit recipients that may or may not be related.
Offprint requests to the present address 相似文献
48.
Parental investment decision rules and the Concorde fallacy 总被引:4,自引:0,他引:4
Summary Investment theory states that animals should base their parental investment decisions on expected benefits, and not on whether or not past investment will be wasted. Otherwise, they would comnit the Concorde fallacy. If reproduction has a cost, however, then past investment and expected benefits are necessarily confounded. Assuming a cost of reproduction, animals will be selected to maximize their remaining lifetime reproductive success, subject to a tradeoff between present and future reproduction (Williams' principle). We extend Williams' principle and develop an experimental design that would allow past investment and expected benefits to be varied independently. This design illustrates the importance of the value of the brood relative to the value of future reproduction. 相似文献
49.
Katriina Tiira Anssi Laurila Katja Enberg Jorma Piironen Sami Aikio Esa Ranta Craig R. R. Primmer 《Behavioral ecology and sociobiology》2006,59(5):657-665
A key question of evolutionary importance is what factors influence who becomes dominant. Individual genetic variation has been found to be associated with several fitness traits, including behaviour. Could it also be a factor influencing social dominance? We investigated the association between social status and the amount of intra-individual genetic variation in juvenile brown trout (Salmo trutta). Genetic variation was estimated using 12 microsatellite loci. Dominant individuals had higher mean heterozygosity than subordinates in populations with the longest hatchery background. Heterozygosity–heterozygosity correlations did not find any evidence of inbreeding; however, single-locus analysis revealed four loci that each individually differed significantly between dominant and subordinate fish, thus giving more support to local than general effect as the mechanism behind the observed association between genetic diversity and a fitness-associated trait. We did not find any significant relation between mean d 2 and social status, or internal relatedness and social status. Our results suggest that individual genetic variation can influence dominance relations, but manifestation of this phenomenon may depend on the genetic background of the population. 相似文献
50.
The southern oyster drill, Stramonita (= Thais, Kool 1987) haemastoma, is a common intertidal and subtidal predator in the southeastern United States. It uses specialized feeding structures and
foraging strategies to bore holes through the shell of its bivalve prey. However, on the east coast of Florida, S. haemastoma, is common on sabellariid worm reefs constructed by the polychaete Phragmatopoma lapidosa (Walton Rocks Beach, Florida, 27°17′N, 80°12′W), a habitat where the snail’s typical prey are scarce. From 1999 to 2001,
we examined the feeding habits of S. haemastoma on sabellariid reefs and the behavioral and morphological responses of S. haemastoma that accompanied switching from a diet of bivalves to sabellariids. On worm reefs S. haemastoma feeds on P. lapidosa by inserting the proboscis deep into a worm’s tube. Worm-feeding snails had longer proboscises (~3.7 times shell height)
than bivalve-feeding conspecifics (~2.0 times shell height). Snails raised on different diets showed significant differences
in proboscis length suggesting that the proboscis length is phenotypically plastic. Whereas typical oyster drills must bore
holes for days before ingesting prey, S. haemastoma on worm reefs avoids boring and attacks and consumes worms in 15–50 min. In the laboratory, oyster drills consumed 1.7 worms
per day, spending <1 h each day feeding. On sabellariid reefs, differences in feeding, handling costs, and prey value, are
likely to have a significant effect on the ecology and life history of S. haemastoma in this habitat. 相似文献