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 15 毫秒
81.
Haruna Amano Toshiaki Fujita Naoshi Hiramatsu Sayumi Sawaguchi Takahiro Matsubara Craig V. Sullivan Akihiko Hara 《Marine Biology》2007,150(6):1215-1225
Coralliophila abbreviata (Lamarck) is a corallivorous gastropod that lives and feeds on several species of scleractinian coral in the Western Atlantic
and Caribbean. Previous studies of C. abbreviata have revealed that snails on branching acroporid corals are larger and consume more tissue than those on massive and plating
corals. To ascertain whether snail life-history and fitness are differentially affected by the coral host, an analysis of
the age structure and female reproductive output of snail populations on three coral host taxa (Acropora palmata, Diploria spp., and Montastraea spp.) was conducted at four shallow (2–7 m depth) reef sites off Key Largo, Florida in June through August, 2004. Snails
were, on average, almost twice as large on A. palmata than on Diploria spp. and Montastraea spp., averaging 30.3 mm shell length, compared to 17.2 and 17.6 mm, respectively. Brood size increased as a power function
with female shell length. Females on A. palmata were significantly larger than females on the other two hosts and, therefore, produced more offspring per female. The number
of growth striae on the inner surface of the operculum was used to estimate snail age. Estimates of growth rate were obtained
by fitting the Gompertz growth function to size-at-age plots and mortality was estimated using growth parameters and size-frequency
data. The data suggest that C. abbreviata inhabiting A. palmata are larger than on alternative hosts due to a combination of a faster growth rate and longer life-span. The species is believed
to be a protandrous hermaphrodite. The timing of sex change varied among hosts; snails on A. palmata changed sex later at larger sizes relative to those on the other two hosts. Based on these results, it seems probable that
C. abbreviata has developed reaction norms for life-history traits, allowing snails to adjust and maximize fitness in the different environments
associated with various coral hosts. 相似文献
82.
Logging, Conifers, and the Conservation of Crossbills 总被引:1,自引:0,他引:1
Craig W. Benkman 《Conservation biology》1993,7(3):473-479
A survey of the forestry literature shows that as the age and area of coniferous forests decline, decreased conifer seed production and increased frequencies of cone failures can be expected. This would, in turn, cause declines in crossbills ( Loxia ), which specialize on the seeds held in conifer cones. In western North America, at least five different species of Red Crossbills ( L. curvirostra ) have recently been distinguished (Groth 1990); each specializes on a different species or even a single variety of conifer (Benkman 1993). Measures for conserving this diversity of crossbills include protecting mature and old-growth stands, and increasing rotation ages throughout the range of each of the required conifers. These recommendations are not unique to crossbills, but rather the loss of crossbill diversity is another reason to employ such measures. 相似文献
83.
Conkling BL Hoover CM Smith WD Palmer CJ 《Environmental pollution (Barking, Essex : 1987)》2002,116(Z1):S221-S232
The national Forest Health Monitoring (FHM) program conducted a remeasurement study in 1999 to evaluate the usefulness and feasibility of collecting data needed for investigating carbon budgets in forests. This study indicated that FHM data are adequate for detecting a 20% change over 10 years (2% change per year) in percent total carbon and carbon content (MgC/ha) when sampling by horizon, with greater than 80% probability that a change in carbon content will be determined when a change has truly occurred (P < or = 0.33). The data were also useful in producing estimates of forest floor and soil carbon stocks by depth that were somewhat lower than literature values used for comparison. The scale at which the data were collected lends itself to producing standing stock estimates needed for carbon budget development and carbon cycle modeling. The availability of site-specific forest mensuration data enables the exploration of above ground and below ground linkages. 相似文献
84.
Craig S. Criddle Perry L. McCarty M. Claire Elliott James F. Barker 《Journal of contaminant hydrology》1986,1(1-2)
At the Canadian Forces Base, Borden, hexachloroethane (HCE) that was introduced into an unconfined sand aquifer disappeared rapidly, with a half-life of about 40 days. Laboratory-scale studies, initiated to help assess the fate of HCE, indicated that it is reductively biotransformed to tetrachloroethylene (PCE) both by aerobic cultures of wastewater microflora and by microcosms containing unhomogenized Borden aquifer material. The results also indicate that the agents involved in the aquifer transformation of HCE to PCE are not homogeneously distributed in the aquifer material. 相似文献
85.
Summary Measures of relative gamete contribution were related to degree of parental investment for both males and females from six groups of communally breeding pukeko (Porphyrio porphyrio). If there is a fitness cost to participation in parental duties, then for males parental investment should relate to degree of confidence of paternity while for females investment should relate to the number of eggs laid. Data were analysed in two ways: (1) by looking at individuals of the same sex within the same group to see if males that had a greater probability of paternity and females that had greater number of eggs in a nest subsequently invested relatively more in parental duties and (2) by pooling the data from the six groups and determining if there was a positive correlation between measures of presumed gamete contribution and amount of parental investment. The results from both types of analyses are variable and give no clear support for a positive relationship between presumed gamete contribution and parental investment even though a possible fitness cost is suggested. Factors which might influence investment are discussed. 相似文献
86.
Should heterogeneity be the basis for conservation? Grassland bird response to fire and grazing. 总被引:2,自引:0,他引:2
Samuel D Fuhlendorf Wade C Harrell David M Engle Robert G Hamilton Craig A Davis David M Leslie 《Ecological applications》2006,16(5):1706-1716
In tallgrass prairie, disturbances such as grazing and fire can generate patchiness across the landscape, contributing to a shifting mosaic that presumably enhances biodiversity. Grassland birds evolved within the context of this shifting mosaic, with some species restricted to one or two patch types created under spatially and temporally distinct disturbance regimes. Thus, management-driven reductions in heterogeneity may be partly responsible for declines in numbers of grassland birds. We experimentally altered spatial heterogeneity of vegetation structure within a tallgrass prairie by varying the spatial and temporal extent of fire and by allowing grazing animals to move freely among burned and unburned patches (patch treatment). We contrasted this disturbance regime with traditional agricultural management of the region that promotes homogeneity (traditional treatment). We monitored grassland bird abundance during the breeding seasons of 2001-2003 to determine the influence of altered spatial heterogeneity on the grassland bird community. Focal disturbances of patch burning and grazing that shifted through the landscape over several years resulted in a more heterogeneous pattern of vegetation than uniform application of fire and grazing. Greater spatial heterogeneity in vegetation provided greater variability in the grassland bird community. Some bird species occurred in greatest abundance within focally disturbed patches, while others occurred in relatively undisturbed patches in our patch treatment. Henslow's Sparrow, a declining species, occurred only within the patch treatment. Upland Sandpiper and some other species were more abundant on recently disturbed patches within the same treatment. The patch burn treatment created the entire gradient of vegetation structure required to maintain a suite of grassland bird species that differ in habitat preferences. Our study demonstrated that increasing spatial and temporal heterogeneity of disturbance in grasslands increases variability in vegetation structure that results in greater variability at higher trophic levels. Thus, management that creates a shifting mosaic using spatially and temporally discrete disturbances in grasslands can be a useful tool in conservation. In the case of North American tallgrass prairie, discrete fires that capitalize on preferential grazing behavior of large ungulates promote a shifting mosaic of habitat types that maintain biodiversity and agricultural productivity. 相似文献
87.
Stochastic dynamic programming (SDP) models predict that males singing to attract a mate should concentrate singing in what
has been termed the dawn chorus. This is because male birds should have a variable surplus of fat in the morning that can
be used to fuel singing, with the amount of fat available dependent upon such factors as his quality, foraging success and
risk of predation. In this manner, the dawn chorus can act as an indicator of male quality in the context of female mate choice.
We test a key prediction of SDP models of singing behaviour that males with greater fat levels should sing more. We conducted
an experiment where we recorded the dawn chorus of male silvereyes (Zosterops lateralis) on three consecutive days. Each male received supplementary food on the second day, which enabled us to sample his dawn
chorus before, during and after food supplementation. We also collected data on the effect of supplementary food on the body
mass of silvereyes. As predicted by SDP models, we found that silvereyes sang for a greater proportion of the time after receiving
supplementary food. Supplementary food also had a significant effect on the complexity of a male song, indicating that males
not only increased the quantity of their song but also the quality of their song when they received extra food. As the provision
of supplementary food significantly increased the mass of fed birds, our results support a causal link between male energy
reserves and his ability to perform the dawn chorus. 相似文献
88.
Food access, brood size and filial cannibalism in the fantail darter, Etheostoma flabellare 总被引:4,自引:0,他引:4
We compared the occurrence of filial cannibalism in fed and starved male fantail darters (Etheostoma flabellare). All males in the experiment consumed eggs, and 56% ate all of their eggs. A male's initial body condition did not explain
the number of eggs that he ate. Neither did non-fed males eat more eggs than fed males. Fed males were able to maintain better
body condition during the experiment, but the change in body condition also depended on the number of eggs eaten. Thus, males
who ate more eggs were able to maintain better body condition.The most important determinant of whether or not a male ate
all of his eggs was his initial egg number. Males with small egg masses ate all of their eggs whereas males with large egg
masses were only partial cannibals. There was, however, no difference in the total number of eggs eaten by total and partial
cannibals. We conclude that eggs are only partially eaten for energetic reasons. We also suggest that small egg masses are
completely consumed because the costs of caring for a small egg mass may exceed the expected reproductive benefits of a small
egg mass.
Received: 26 January 1996 / Accepted after revision: 2 November 1996 相似文献
89.
90.