全文获取类型
收费全文 | 4228篇 |
免费 | 37篇 |
国内免费 | 41篇 |
专业分类
安全科学 | 102篇 |
废物处理 | 236篇 |
环保管理 | 359篇 |
综合类 | 696篇 |
基础理论 | 885篇 |
环境理论 | 3篇 |
污染及防治 | 1314篇 |
评价与监测 | 410篇 |
社会与环境 | 273篇 |
灾害及防治 | 28篇 |
出版年
2023年 | 44篇 |
2022年 | 131篇 |
2021年 | 169篇 |
2020年 | 83篇 |
2019年 | 74篇 |
2018年 | 159篇 |
2017年 | 162篇 |
2016年 | 210篇 |
2015年 | 136篇 |
2014年 | 196篇 |
2013年 | 307篇 |
2012年 | 202篇 |
2011年 | 279篇 |
2010年 | 201篇 |
2009年 | 171篇 |
2008年 | 206篇 |
2007年 | 200篇 |
2006年 | 146篇 |
2005年 | 159篇 |
2004年 | 194篇 |
2003年 | 190篇 |
2002年 | 135篇 |
2001年 | 97篇 |
2000年 | 51篇 |
1999年 | 42篇 |
1998年 | 21篇 |
1997年 | 28篇 |
1996年 | 26篇 |
1995年 | 26篇 |
1994年 | 28篇 |
1993年 | 15篇 |
1992年 | 16篇 |
1991年 | 18篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1979年 | 9篇 |
1975年 | 4篇 |
1970年 | 3篇 |
1968年 | 3篇 |
1966年 | 3篇 |
1964年 | 5篇 |
1961年 | 3篇 |
排序方式: 共有4306条查询结果,搜索用时 46 毫秒
981.
Differential access to food resources is thought to be the main determinant of differences in female reproductive success but is poorly studied in both pair-living and nocturnal primates. The modes of food competition within and between families were investigated following the principles proposed by the ecological model using 3 years of field data from seven fork-marked lemur (Phaner furcifer) families. The major food resources were identified from year-round feeding observations and the strength and mode of competition were inferred from differences in physical condition. The most important food resource of fork-marked lemurs were tree exudates which occurred in small, defendable food patches, characterized by fast depletion and rapid renewal. These characteristics led to strong within-group contest and scramble competition, which were found to yield a positive dominance effect and a negative group-size effect on female net energy gain. Differential physical condition, however, did not translate directly into differential reproductive success. Low female fertility was best predicted by large family size associated with delayed dispersal by previous offspring. Although there is no obvious benefit from full-grown offspring in their territory, adults tolerate delayed natal dispersal, probably because dispersal poses extraordinary costs for the offspring. These costs are likely to accrue from decreased foraging efficiency in unfamiliar habitats because exudate feeding requires very rigid feeding itineraries. In conclusion, the presented evidence for group-size effects on reproductive success in pair-living females opens a new area for research on the costs and benefits of delayed dispersal and female reproductive decisions.This revised version was published in September 2003 with corrections to the Authors Present address.An erratum to this article can be found at
Communicated by E.H.M. Sterck 相似文献
982.
A new concept based on analysis of dive depth data was developed to help estimate prey consumption in ten free-ranging Magellanic penguins (Spheniscus magellanicus) that were brooding chicks. By simultaneously analysing the undulations in the dive depth profile (measured by time-depth recorders, TDRs) and beak opening (obtained from the recently developed intra-mandibular angle sensors, IMASEN), it was possible to determine the proportions of the undulations in the dive profile that resulted (or not) in prey capture. This methodology allowed the number of prey consumed to be estimated with a mean error of 10±6% using TDR data alone. If the mean mass of prey is known, then the overall mass of prey consumed per unit time can be determined. Additionally, the method allows estimation of the depth at which prey is taken and thus indicates how penguins exploit the water column. Due to its simplicity, the proposed methodology has applications for other Spheniscus penguin species and should be considered for other marine endotherm divers that show undulations in the dive depth profile.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
983.
Standard metabolic rates of the endemic Antarctic scallop, Adamussium colbecki (Smith, 1902), were measured in austral summer and under simulated winter conditions. Average mass-specific metabolic rates were significantly different between "summer" (151.17±45.06 µl O 2 g -1 h -1) and "winter" (106.52±39.65 µl O 2 g -1 h -1) animals. The overall metabolic rates of A. colbecki are comparable to those of other Antarctic bivalve species, but well below those of temperate scallop species. Data for 24 scallop populations (13 species) from different latitudes give no evidence for elevated metabolic rates in A. colbecki as suggested by the concept of "metabolic cold adaptation". A world-wide comparison of metabolic rate and overall growth performance of scallops indicates that in the Antarctic scallop the energetic advantage of low basal metabolism does not counterbalance the disadvantage of the prolonged seasonal period of food shortage. 相似文献
984.
985.
986.
987.
988.
989.
990.
Jonathan Mark Wilson Alexandre Leitão Ana Filipa Gonçalves Catarina Ferreira Patrick Reis-Santos Ana-Violeta Fonseca Joana Moreira da Silva José Carlos Antunes Cristina Pereira-Wilson João Coimbra 《Marine Biology》2007,151(5):1633-1645
The Anguillid juvenile glass eel must deal with the osmoregulatory consequences of highly variable environmental salinities
on its recruitment migration from coastal to fresh waters. Changes in ionoregulatory parameters and branchial ion transport
protein [Na+/K+-ATPase, Na+:K+:2Cl− cotransporter (NKCC), cystic fibrosis transmembrane regulator (CFTR) anion channel, V-type proton ATPase] expression (activities,
protein and/or mRNA level expression and/or cellular localization) in response to acclimation to a broad range of ionic strengths
[distilled water (DW) to hypersaline water (HSW; 150%) sea water (SW 32‰)] was studied. The estuarine glass eels were very
euryhaline and successfully acclimated to acute changes in environmental ionic strength from 50% SW, with high mortality only
observed in HSW (51%) and sublethal osmoregulatory indicators (whole body water content and sodium levels) disturbed at the
extremes (DW and HSW). Central to a high salinity acclimation were elevated branchial Na+/K+-ATPase, NKCC and CFTR expression. At lower salinity, Na+/K+-ATPase expression was maintained and NKCC and CFTR expressions were reduced. Branchial chloride cells increased in size up
to SW but decreased in HSW. During hypotonic disturbance (DW), no compensatory elevation in V-ATPase or Na+/K+-ATPase expression was observed. 相似文献