全文获取类型
收费全文 | 381篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 2篇 |
废物处理 | 4篇 |
环保管理 | 9篇 |
综合类 | 202篇 |
基础理论 | 63篇 |
污染及防治 | 86篇 |
评价与监测 | 10篇 |
社会与环境 | 8篇 |
出版年
2021年 | 3篇 |
2018年 | 4篇 |
2016年 | 5篇 |
2014年 | 8篇 |
2013年 | 12篇 |
2012年 | 7篇 |
2011年 | 5篇 |
2010年 | 10篇 |
2009年 | 16篇 |
2008年 | 7篇 |
2007年 | 21篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1983年 | 3篇 |
1981年 | 4篇 |
1978年 | 3篇 |
1967年 | 4篇 |
1966年 | 4篇 |
1965年 | 5篇 |
1964年 | 8篇 |
1963年 | 11篇 |
1962年 | 4篇 |
1961年 | 7篇 |
1960年 | 5篇 |
1959年 | 6篇 |
1958年 | 10篇 |
1957年 | 7篇 |
1956年 | 7篇 |
1955年 | 12篇 |
1954年 | 6篇 |
1952年 | 4篇 |
1951年 | 3篇 |
1950年 | 6篇 |
1947年 | 5篇 |
1943年 | 6篇 |
1939年 | 4篇 |
1928年 | 2篇 |
1924年 | 3篇 |
排序方式: 共有384条查询结果,搜索用时 31 毫秒
71.
72.
73.
74.
75.
Preserved skin of small dinosaurs is rare. Here, a specimen of the ceratopsian dinosaur, Psittacosaurus, presents some of the best preserved epidermal scales observed to date in a relatively small dinosaur, over wide areas extending from the head to the tail. We study the preserved epidermis of SMF R 4970, the different types of scales, color, and patterns, and their respective locations in the body. We use modern application of high-power digital imaging for close-up analysis of the tubercles and fragments of preserved color. Three types of scales are preserved, large plate-like scales, smaller polygonal scales or tubercles, and round pebble-like scales. The sizes of the plate-like scales vary in different parts of the body and vanish altogether posteriorly. Light and dark cryptic patterns are created by the associations of the tubercle and plate-like scales, and there is also evidence of countershading in the proximal caudal region, the body darker dorsally and lighter ventrally. Perhaps most impressive are the distinctive pigmented impressions of scales over most of the skeletal elements. The pigmentation follows the curvature of the bones implying that when it was deposited, the skin was still pliable and able to wrap around the visible parts of the elements. The present record of color is the first in a non-theropod dinosaur and only the second record in a non-avian dinosaur. Because of its resistance to degradation and ability to produce various color tones from yellows to blacks, we suggest that melanin was the dominant chemical involved in the coloration of Psittacosaurus. The data here enable us to reconstruct the colors of Psittacosaurus as predominantly black and amber/brown, in cryptic patterns, somewhat dull, but useful to a prey animal. Indeed, skin pigment within a partially degraded bone indicates that Psittacosaurus was scavenged shortly after death. The theropod dinosaur Sinosauropteryx has recently been reported to have naturally pigmented integumental structures, which the authors interpret as proof that they are protofeathers and not support fibers of collagen. Our findings in Psittacosaurus, on the other hand, indicate a more parsimonious and less profound alternative explanation, i.e., decomposition of the skin releases pigments that readily permeate underlying structures. 相似文献
76.
Kevin Lam Kelsie Thu Michelle Tsang Margo Moore Gerhard Gries 《Die Naturwissenschaften》2009,96(9):1127-1132
Female houseflies, Musca domestica (Diptera: Muscidae), lay their eggs in ephemeral resources such as animal manure. Hatching larvae compete for essential nutrients
with fungi that also colonize such resources. Both the well-known antagonistic relationship between bacteria and fungi and
the consistent presence of the bacterium Klebsiella oxytoca on housefly eggs led us to hypothesize (1) that K. oxytoca, and possibly other bacteria on housefly eggs, help curtail the growth of fungal resource competitors and (2) that such fungi
indeed adversely affect the development of housefly larvae. Bacteria washed from housefly eggs significantly reduced the growth
of fungi in chicken manure. Nineteen bacterial strains and ten fungal strains were isolated from housefly eggs or chicken
manure, respectively. Co-culturing each of all the possible bacterium–fungus pairs revealed that the bacteria as a group,
but no single bacterium, significantly suppressed the growth of all fungal strains tested. The bacteria's adverse effect on
fungi is due to resource nutrient depletion and/or the release of antifungal chemicals. Well-established fungi in resources
significantly reduced the number of larval offspring that completed development to adult flies.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
77.
Chris R. Pavey Chris J. Burwell Gerhard Körtner Fritz Geiser 《Die Naturwissenschaften》2009,96(6):679-683
One of the energetic benefits of daily torpor over prolonged hibernation is that it enables animals to regularly forage and,
therefore, replenish food reserves between bouts of torpor. However, little is known about the diet of predators undergoing
torpor or whether differences in prey composition among individuals influence torpor characteristics. Here, we test the hypothesis
that prey composition affects winter torpor use and patterns of a population of carnivorous marsupial, the brush-tailed mulgara
(Dasycercus blythi), in the Great Sandy Desert, Australia. Mulgaras in the study population captured a wide range of prey including vertebrates
(mammals, reptiles, birds), seven insect orders, spiders and centipedes. The proportion of vertebrates in the diet was negatively
correlated with both frequency of torpor use and maximum bout duration. This variation in torpor use with diet can be explained
by the higher energetic content of vertebrates as well as their larger size. Even assuming uniform intake of prey biomass
among individuals, those that subsisted on an invertebrate-dominated diet during winter apparently suffered energetic shortages
as a result of the scarcity of invertebrate taxa with high energy content (such as insect larvae). Our study is the first
to demonstrate a link between diet composition and daily torpor use in a free-ranging mammal. 相似文献
78.
79.
80.
Organic residue decomposition: The minicontainer-system a multifunctional tool in decomposition studies 总被引:1,自引:0,他引:1
Gerhard Eisenbeis Ralf Lenz Thomas Heiber 《Environmental science and pollution research international》1999,6(4):220-224
The Minicontainer-test, first described by Eisenbeis (1993), was designed to study the kinetics of organic residue decomposition
at a microsite level. It is derived from the litterbag technique and consists of polyethylene minicontainers (volume about
1.5 cm3) filled with a test substrate (litter, straw, cellulose, etc.). The minicontainers (MCs) are closed at either end with plastic
gauze discs of variable mesh size (e.g. 20 μm, 250 μm, 500 μm or 2 mm). A definite number of such units are inserted into
PVC-bars, which can be implanted into the soil horizontally or vertically, or be exposed on the soil surface horizontally.
The bars are very stable and can be exposed in different environments for months to years. If required, the bars can be removed
temporarily and stored, e.g. during soil cultivation. Should fresh litter be used, two phases of decomposition can be distinguished:
a fast initial phase, which can be mainly related to the effect of leaching, and a second slow phase depending mainly on the
activity of soil organisms and litter quality. Several questions can be addressed to investigations using MCs, e.g. 1) parts
of the soil fauna which are involved in decomposition (nematodes, microarthropods, and smaller specimens of the macrofauna,
e.g. enchytraeidae, diplopods and dipteran larvae) can be extracted from the litter substrate using a miniscale high gradient
extractor, 2) the organic mass loss of litter can be determined, 3) microbial biomass (Cmic, Nmic) can be assessed by fumigation extraction and 4) microbial activity (respiration) in the test substrate can also be assessed
by use of standardised methods. Compared to litterbag studies, the larger number of small replicate units improves the statistical
evaluation. Until today the Minicontainer-test has been applied in forestry and agriculture, e.g. studying the effects of
liming, soil restoration and the application of insecticides, e.g. Diflubenzuron (Dimilin) and Btk (Bacillus thuringiensis var.kurstaki). 相似文献