全文获取类型
收费全文 | 10525篇 |
免费 | 32篇 |
国内免费 | 8篇 |
专业分类
安全科学 | 52篇 |
废物处理 | 804篇 |
环保管理 | 1449篇 |
综合类 | 1011篇 |
基础理论 | 3338篇 |
环境理论 | 2篇 |
污染及防治 | 1914篇 |
评价与监测 | 1063篇 |
社会与环境 | 924篇 |
灾害及防治 | 8篇 |
出版年
2023年 | 8篇 |
2022年 | 16篇 |
2021年 | 12篇 |
2020年 | 6篇 |
2019年 | 14篇 |
2018年 | 1490篇 |
2017年 | 1385篇 |
2016年 | 1218篇 |
2015年 | 152篇 |
2014年 | 38篇 |
2013年 | 65篇 |
2012年 | 511篇 |
2011年 | 1389篇 |
2010年 | 724篇 |
2009年 | 645篇 |
2008年 | 937篇 |
2007年 | 1276篇 |
2006年 | 57篇 |
2005年 | 50篇 |
2004年 | 74篇 |
2003年 | 100篇 |
2002年 | 131篇 |
2001年 | 23篇 |
2000年 | 25篇 |
1999年 | 16篇 |
1998年 | 23篇 |
1997年 | 11篇 |
1996年 | 14篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 16篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1957年 | 2篇 |
1935年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
191.
Claudia Ursprung Michelle den Hollander Darryl T. Gwynne 《Behavioral ecology and sociobiology》2009,63(6):781-788
Female seed beetles, Callosobruchus maculatus, mate multiply even though association with males and copulations carry costs, such as injury to the genital tract. Multiple
mating (polyandry) may, however, offset these costs through the acquisition of food and water, two material benefits hypothesized
to be obtained from the large ejaculates produced by males. The material benefits hypothesis can be tested by increasing female
access to nutrients and water, with the prediction that female mating frequency will decrease as copulation is no longer required
to derive these materials. Females were given water, 5% sugar–water or baker’s yeast, and were compared with females deprived
of these. We presented females with virgin males daily for 8 days and recorded female mating frequency, survivorship, and
fecundity. Females provided with water and sugar–water decreased mating frequency. Thus, water, rather than nutrients in the
ejaculate, appears to be important to females of this species. In addition, both life span and fecundity were extended for
females in the sugar–water and water treatments. Since water is scarce in the arid environment in which this species is found,
we conclude that polyandry provides material benefits to females that may offset some of the costs of associating with males. 相似文献
192.
The cardinalfish Siphamia versicolor (Perciformes: Apogonidae) forms a bioluminescent symbiosis with the marine luminous bacterium Photobacterium mandapamensis, harboring the bacteria in a ventral, disc-shaped light organ and using the bacterial light apparently for counterillumination
and attracting prey. Little definitive information has been available on the developmental and microbiological events surrounding
the initiation of symbiosis, a critical stage in the life history of the fish, in S. versicolor or any of the many other species of bacterially luminous fish. To identify the stage at which light organ formation begins,
to determine the origin of cells forming the light organ, and to characterize its bacterial colonization status during development,
early developmental stages of S. versicolor obtained and reared from wild-caught mouth-brooding males were examined with histological and microbiological methods. A
light organ primordium was not evident in embryos, post-embryos, or pre-release larvae, whereas the light organ began to form
within 1 day of release of full-term pre-flexion larvae from the mouths of male fish. Analysis of post-release larvae revealed
that the light organ arises from a proliferation and differentiation of intestinal epithelial cells, and that it quickly develops
structural complexity, including the formation of chambers and gaps contiguous with the intestinal epithelium. However, the
nascent light organ remained uncolonized by the symbiotic bacteria through several days of post-release development, even
in the presence of high numbers of the symbiotic bacteria. These results demonstrate that the inception of light organ formation
in S. versicolor occurs independently of its symbiotic bacteria and that receptivity to bacterial colonization apparently requires substantial
post-release development of the light organ. Larvae therefore most likely acquire their symbiotic bacteria from seawater,
during or shortly after the transition from the pre-flexion to the flexion developmental stage. 相似文献
193.
Linhong Jing Spencer M. Steinberg Brian J. Johnson 《Journal of the Air & Waste Management Association (1995)》2013,63(9):1359-1366
ABSTRACT Linhong Jing completed a master's degree in chemistry at UNLV and is currently enrolled in the Ph.D. program at Purdue University. Her address is Department of Chemistry, Purdue University, West Lafayette, IN 47907. Dr. Spencer Steinberg is an associate professor of chemistry at UNLV. His address is UNLV Department of Chemistry, P.O. Box 454003, Las Vegas, NV 89154-4003. Dr. Brian Johnson is an associate professor of chemistry at UNLV. His address is UNLV Department of Chemistry, P.O. Box 454003, Las Vegas, NV 89154-4003. Oxidation of benzene, toluene, ethylbenzene, and xylenes (BTEX) in air, of significance due to, for example, the potential for O3 formation, is believed to be initiated by OH attack on the ring (addition) or on the alkyl side chain (H abstraction). A series of ring-breaking reactions follows, with major products predicted to be a-dicarbonyls, simple aldehydes, and organic acids. To test this prediction, ambient air mixing ratios of aldehydes (formaldehyde, ac-etaldehyde, benzaldehyde, glyoxal, and pyruvaldehyde), along with some supporting BTEX data, were measured at an urban site in Las Vegas, NV. Samples were collected on sorbents and determined by chromatographic methods; mixing ratios were compared to ambient levels of CO, O3, and NOx. A meteorological analysis (temperature, wind speed, and wind direction) was also included. Statistically significant relationships were noted among the BTEX hydrocarbons (HCs) and among the photochemi-cally derived species (e.g., O3, NO2, and some of the aldehydes), although there was seasonal variation. The observations are consistent with a common primary source (i.e., vehicular exhaust or fuel evaporation) for the BTEX compounds and a common secondary source (e.g., OH attack) for glyoxal and pyruvaldehyde. 相似文献
194.
In order to evaluate the potential harmful effects of gas flaring on mammals, albino mice, Mus musculus, were exposed to gas flares for 8 weeks under laboratory conditions. The effect of gas flaring on blood parameters includes
a reduction in white blood cell counts among mice exposed to 8-h daily of gas flaring when compared to control mice. The red
blood cells also showed varied abnormalities such as stacked erythrocytes (rouleaux formation), crenated (spicule) cells and
teardrop cells (dacrocytes). The detection of the increasing level of eosinophils in the blood of mice exposed to gas flares
was observed to be indicative of a degenerative disease condition and usefulness as a good marker of pollution for monitoring,
and early detection of adverse effects of gas flares was recommended. Histopathological examination of the lungs of exposed
mice revealed distortions in the segmental bronchus and alveoli of the respiratory organ, with interspersed brown pigments
and polymorphonuclear cells, which were absent in the controls. The environmental implications including the health hazards
posed by the exposure of mammals to gas flares in crude oil production areas were discussed. 相似文献
195.
Ali Jamshidparvar Faramin Javandel Alireza Seidavi Francisco Peña Blanco Andrés L. Martínez Marín Carmen Avilés Ramírez Estrella Agüera Buendía Nieves Núñez-Sánchez 《Environmental science and pollution research international》2017,24(30):23571-23577
Increasing levels of Heracleum persicum (golpar) in drinking water were studied in broilers. Two hundred and forty-one-day-old male chickens were allocated to one of six treatments: control, without added phytogenics nor probiotics in drinking water, and probiotics at recommended manufacturer’s level (P) or 1.0, 1.5, 2.0, and 2.5 ml/l of golpar extract solution (G1, G1.5, G2, and G2.5 treatments, respectively) in drinking water. As a result of this study, no linear or quadratic trends in the feed intake (FI) and feed conversion rate (FCR) due to golpar supplementation were found. Body weight gain, final body weight, and relative carcass weight showed a positive linear response with increasing levels of golpar supplementation. Neither golpar nor probiotics had effects on the percentages of edible parts of the carcass. Golpar supplementation levels caused a linear negative response of the albumin content in blood plasma, whereas both abdominal fat as percentage of carcass weight and uric acid levels in blood plasma linearly increased. The effects on Ig responses were only observed at 42 days of age and were similar in probiotics and the highest level of golpar supplementation. Based on our results, both probiotics and golpar supplementation could improve broiler performance and immune function. 相似文献
196.
C. Henry Obasi U. Martin Obidiegwu N. Godwin Onyeagoro O. Innocent Arukalam C. Genevive Onuegbu N. Francis Onuoha M. Chinomso Ewulonu 《Journal of Polymers and the Environment》2017,25(3):544-555
We report in this paper the transport of an aromatic solvent, xylene through palm pressed fibre filled low density polyethylene composites studied at three different temperatures (40, 60, and 80 °C) by conventional weight-gain method. The diffusion parameters were investigated with special reference to the effect of fibre content, temperature and particle size. The effect of alkali treatment on solvent uptake was also analyzed. The transport coefficients of diffusion, permeation and sorption were determined to evaluate the influence of interface bonding on transport properties. The van’t Hoff relationship was used to determine the thermodynamic parameters and was found that the estimated free energies of sorption were all positive, indicating non-spontaneity of the solubility of PPF/LDPE composites. The first order kinetic rate constant and swelling parameters were also evaluated. 相似文献
197.
María del Mar Delgado Vincenzo Penteriani Vilis O. Nams Letizia Campioni 《Behavioral ecology and sociobiology》2009,64(1):35-43
Moving and spatial learning are two intertwined processes: (a) changes in movement behavior determine the learning of the
spatial environment, and (b) information plays a crucial role in several animal decision-making processes like movement decisions.
A useful way to explore the interactions between movement decisions and learning of the spatial environment is by comparing
individual behaviors during the different phases of natal dispersal (when individuals move across more or less unknown habitats)
with movements and choices of breeders (who repeatedly move within fixed home ranges), that is, by comparing behaviors between
individuals who are still acquiring information vs. individuals with a more complete knowledge of their surroundings. When
analyzing movement patterns of eagle owls, Bubo bubo, belonging to three status classes (floaters wandering across unknown environments, floaters already settled in temporary
settlement areas, and territory owners with a well-established home range), we found that: (1) wandering individuals move
faster than when established in a more stable or fixed settlement area, traveling larger and straighter paths with longer
move steps; and (2) when floaters settle in a permanent area, then they show movement behavior similar to territory owners.
Thus, movement patterns show a transition from exploratory strategies, when animals have incomplete environmental information,
to a more familiar way to exploit their activity areas as they get to know the environment better. 相似文献
198.
One of the major consequences of global warming is a rise in sea surface temperature which may affect the survival of marine
organisms including phytoplankton. Here, we provide experimental evidence for heat-induced cell death in a symbiotic microalga.
Shifting Symbiodinium microadriaticum from 27 to 32°C resulted in an increase in mortality, an increase in caspase 3-like activity, and an increase in nitric oxide
(NO) production. The caspase-like activity was strongly correlated with the production of NO in thermally challenged microalgae.
For this experiment, the application of Ac-DEVD-CHO, a mammalian caspase 3-specific inhibitor, partly prevented (by 65%) the
increase in caspase-like activity. To verify the relationship between NO and the caspase-like activity, S. microadriaticum were subsequently incubated with 1.0 mM of the following chemical NO donors: sodium nitroprusside (SNP), S-nitrosoglutathione (GSNO), S-nitroso-N-acetylpenicillamine (SNAP) and 3,3bis(Aminoethyl)-1-hydroxy-2-oxo-1-triazene (NOC-18). The supplementation of both SNP and
NOC-18 caused a significant increase in caspase-like activity compared to the control treatment. Pre-treatment of the microalgae
with the inhibitor Ac-DEVD-CHO before the supplementation of the different NO donors completely prevented the increase in
caspase-like activity. These results suggest that NO could play a role in the induction of cell death in heat-stressed S. microadriaticum by mediating an increase in caspase-like activity. 相似文献
199.
Merlin Aydın Hale Tozlu Sebnem Kemaloglu Ayse Aytac Guralp Ozkoc 《Journal of Polymers and the Environment》2011,19(1):11-17
In this study, the influence of alkali (NaOH) treatment on the mechanical, thermal and morphological properties of eco-composites
of short flax fiber/poly(lactic acid) (PLA) was investigated. SEM analysis conducted on alkali treated flax fibers showed
that the packed structure of the fibrils was deformed by the removal non-cellulosic materials. The fibrils were separated
from each other and the surface roughness of the alkali treated flax fibers was improved. The mechanical tests indicated that
the modulus of the untreated fiber/PLA composites was higher than that of PLA; on the other hand the modulus of alkali treated
flax fiber/PLA was lower than PLA. Thermal properties of the PLA in the treated flax fiber composites were also affected.
Tg values of treated flax fiber composites were lowered by nearly 10 °C for 10% NaOH treatment and 15 °C for 30% NaOH treatment.
A bimodal melting behavior was observed for treated fiber composites different than both of neat PLA and untreated fiber composites.
Furthermore, wide angle X-ray diffraction analysis showed that the crystalline structure of cellulose of flax fibers changed
from cellulose-I structure to cellulose-II. 相似文献
200.
Brian L. Finlayson Jon Barnett Taoyuan Wei Michael Webber Maotian Li Mark Y. Wang Jing Chen Hao Xu Zhongyuan Chen 《Regional Environmental Change》2013,13(2):329-340
Big cities are often said to have big water problems, and Shanghai is no exception. In this paper, we examine and compare the influence of the major factors that give rise to the risk of water insecurity in Shanghai. There is an extensive and diverse literature on these issues, dealt with in isolation, and here, we provide a synthesis of the literature, together with our own assessments and calculations, to assess what are the risks to Shanghai’s water supply and what is our degree of confidence in this assessment. We describe the systems that supply water to the city, and past and future changes in the systems, including changes in the glaciers that supply some water to the river, changes in climate, changes in land use, the construction of dams, and water diversions. We show how, at the same time as Shanghai is increasing its dependence on the Yangtze river, water diversions and sea level rise are increasing the risk that this water will be too saline to consume at certain times of the year. This analysis suggests that most of the major drivers of the risk to water security in Shanghai are within the power of environmental managers to control. 相似文献