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91.
The shrub Iva frutescens, which occupies the terrestrial border of U.S. Atlantic Coast salt marshes, supports a food web that varies strongly across latitude. We tested whether latitudinal variation in plant quality (higher at high latitudes), consumption by omnivores (a crab, present only at low latitudes), consumption by mesopredators (ladybugs, present at all latitudes), or the life history stage of an herbivorous beetle could explain continental-scale field patterns of herbivore density. In a mesocosm experiment, crabs exerted strong top-down control on herbivorous beetles, ladybugs exerted strong top-down control on aphids, and both predators benefited plants through trophic cascades. Latitude of plant origin had no effect on consumers. Herbivorous beetle density was greater if mesocosms were stocked with beetle adults rather than larvae, and aphid densities were reduced in the "adult beetle" treatment. Treatment combinations representing high and low latitudes produced patterns of herbivore density similar to those in the field. We conclude that latitudinal variation in plant quality is less important than latitudinal variation in top consumers and competition in mediating food web structure. Climate may also play a strong role in structuring high-latitude salt marshes by limiting the number of herbivore generations per growing season and causing high overwintering mortality. 相似文献
92.
This article reviews attempts by other workers to derive full economic evaluations of local authority waste paper recovery operations and proposals from government bodies to devise uniform costing systems for these schemes. In the light of this work a standard costing system for local authority waste paper recovery operations is proposed. Empirical data was obtained from a number of local authorities and analysed using this standard costing system. The viability of each scheme under the standard costing system and the Council's original costing system is compared. 相似文献
93.
Recent reports of absent nasal bone in fetuses with Down syndrome have sparked much interest in the use of this finding for the screening of Down syndrome. We describe the histopathological findings of nasal bones of two fetuses with Down syndrome, one with absence and the other with normal ossification of the nasal bone. We propose that histopathological examination of the nasal bone could improve the accuracy of diagnosis of nasal hypoplasia among Down syndrome abortuses. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
94.
Enteric duplications are rare lesions, and relatively few cases have been diagnosed prenatally. We present, to our knowledge, the first case of an associated communicating ileal duplication cyst in a huge omphalocele diagnosed prenatally. The prenatal ultrasound findings revealed four features of the cystic lesion including peristaltic movements of the cystic wall, communication between the cyst and normal bowel lumen, intra-cystic echogenic contents, and echogenic mesenteric tissue (fat) close to the cyst. These distinct characteristics helped us to make a firm in utero diagnosis. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
95.
Xiangrong Wang Yi Yong Shixiong Wang Hao Zhang Hing Hon Ho Pingjian Wang Shoubing Wang Weizhen Chen 《Frontiers of Environmental Science & Engineering in China》2008,2(2):178-186
The background, concept, connotation, principles, and methods of eco-planning for an Eco-Demonstration Park (EDP) and sustainability
were examined based on a case study of the Luhua EDP in the Chongming Island of Shanghai, China, which is an important part
of Shanghai Eco-city planning and construction in the 21st century. By analyzing natural, social and economic conditions,
calculating population using the land capacity eco-model, eco-function zoning, and eco-construction, an innovative eco-industrial
structure and technical chain were formulated. A comprehensive eco-planning scheme for the EDP was proposed, including planning
and management strategies for subsystems of efficient industry, good quality human settlement, high standard eco-construction
and eco-tourism as well as effective environmental protection and attractive landscape. The EDP should be an area with coordinated
and sustainable economic, social and environmental subsystems. Eco-planning for the EDP should be a very important part of
eco-city planning and sustainability. The paper aims to set up a theoretical framework and practical basis for eco-planning
and promoting harmony between human and nature. 相似文献
96.
Suppression pheromone and cockroach rank formation 总被引:1,自引:0,他引:1
Although agonistic behaviors in the male lobster cockroach (Nauphoeta cinerea) are well known, the formation of an unstable hierarchy has long been a puzzle. In this study, we investigate how the unstable
dominance hierarchy in N. cinerea is maintained via a pheromone signaling system. In agonistic interactions, aggressive posture (AP) is an important behavioral
index of aggression. This study showed that, during the formation of a governing hierarchy, thousands of nanograms of 3-hydroxy-2-butanone
(3H-2B) were released by the AP-adopting dominant in the first encounter fight, then during the early domination period and
that this release of 3H-2B was related to rank maintenance, but not to rank establishment. For rank maintenance, 3H-2B functioned
as a suppression pheromone, which suppressed the fighting capability of rivals and kept them in a submissive state. During
the period of rank maintenance, as the dominant male gradually decreased his 3H-2B release, the fighting ability of the subordinate
gradually developed, as shown by the increasing odds of a subordinate adopting an AP (OSAP). The OSAP was negatively correlated
with the amount of 3H-2B released by the dominant and positively correlated with the number of domination days. The same OSAP
could be achieved earlier by reducing the amount of 3H-2B released by the dominant indicates that whether the subordinate
adopts an offensive strategy depends on what the dominant is doing. 相似文献
97.
邻苯二甲酸酯类(PAEs)作为一类重要的环境激素类化学物质,被广泛应用于塑料的增塑剂中。随着工业的发展,中国PAEs的需求量迅速增加,PAEs已成为中国城市水环境的重要风险因子,因此需要对其进行生态风险评价。本研究首先针对我国典型城市水环境中PAEs的污染现状进行文献综述,总结归纳得到我国典型城市水环境中PAEs的污染分布特征;其次运用熵值法计算了我国典型水环境中PAEs对于藻类、水蚤和鱼类种群的生态风险,并依据生态风险等级划分标准将PAEs生态风险划分为4个水平。文献综述结果表明我国城市水环境中的PAEs浓度多数都高于8.00μg·L~(-1),超过了我国地表水环境质量标准(PRC-NS 2002)和饮用水质量标准(PRC-NS 2006)中的规定限值,且在大城市或PAEs工业区周围的污染水平要显著高于其他区域。将我国与国外典型城市水环境中PAEs的污染水平进行比较,结果表明我国水环境中的PAEs污染水平明显高于其他国家。此外,我国城市水环境中PAEs的污染不仅出现在地表水环境中,而且在广东东莞等地的地下水环境中也出现了PAEs污染,PAEs浓度范围为0.0~6.7μg·L~(-1)。生态风险评价的结果表明,邻苯二甲酸二丁酯(DBP)、邻苯二甲酸二异辛酯(DEHP)和邻苯二甲酸丁苄酯(BBP)是我国城市水环境中最主要的风险因子。PAEs污染分布特征和生态风险评价的结果表明我国城市水环境中的PAEs生态风险值总体处于10≤风险熵(RQ)100到RQ≥100水平,尤其是在大城市或者PAEs工业密集区域,因此,亟需对我国城市水环境中PAEs的生态风险进行早期预警和风险管理。 相似文献
98.
Kim Kyeong Ho Bae Min A. Lee Man Sig Park Hung-Suck Baek Jae Ho 《Journal of Material Cycles and Waste Management》2021,23(1):121-129
Journal of Material Cycles and Waste Management - Organic binders that are used in sand casting emit high amounts of hazardous pollutants and volatile organic compounds during the casting process.... 相似文献
99.
在工业化国家,已经证实了生物补救、植物工程与人工地下永补充的有效性.他们对发展中世界也有巨大的使用潜力.模拟自然的发育过程,它们提供了使环境可持续的解决办法.当这些和那些技术在发展中国家应用的时候,要根据当地的实际情况考虑社会、经济和环境条件.关于技术转让和能力建设的问题,也应该量力而行. 相似文献
100.
Sung Ho Hwang Jae Bum Park Kyung Jong Lee 《Environmental geochemistry and health》2018,40(4):1237-1246
This study evaluates the effect of air pollution caused by cement plants on nearby residential areas and performs an exposure assessment of particulate matter (PM) and total Cr, Cr6+, Pb, and Al. Further, the blood Cr levels of residents exposed to PM released by cement plants are also assessed. Nine buildings (eight residential and one elementary school building) close to cement plants were selected for this study, which were located in Pyeongtaek port, in west of Gyeonggi Province, South Korea. A total of 51 suspended particulate samples were collected at a flow rate of 2.0 L/min. Total Cr was more widely detected in residents’ houses and elementary schools. PM levels were higher at distances of 4.1 and 4.8 km than those at closer distances of 2.7 km. This was due to the influence of wind direction. The estimated mean blood level of Cr for the study participants was 3.80 μg/L, which is higher than levels estimated by other studies on Cr blood levels. Therefore, cement plants could cause an increase in total Cr and blood Cr levels in residential areas, and more continuous monitoring is necessary to better understand their impacts. 相似文献