全文获取类型
收费全文 | 5434篇 |
免费 | 46篇 |
国内免费 | 24篇 |
专业分类
安全科学 | 118篇 |
废物处理 | 355篇 |
环保管理 | 392篇 |
综合类 | 617篇 |
基础理论 | 1148篇 |
环境理论 | 7篇 |
污染及防治 | 1949篇 |
评价与监测 | 521篇 |
社会与环境 | 380篇 |
灾害及防治 | 17篇 |
出版年
2023年 | 62篇 |
2022年 | 143篇 |
2021年 | 192篇 |
2020年 | 85篇 |
2019年 | 89篇 |
2018年 | 194篇 |
2017年 | 195篇 |
2016年 | 288篇 |
2015年 | 164篇 |
2014年 | 294篇 |
2013年 | 528篇 |
2012年 | 358篇 |
2011年 | 407篇 |
2010年 | 274篇 |
2009年 | 219篇 |
2008年 | 314篇 |
2007年 | 349篇 |
2006年 | 242篇 |
2005年 | 206篇 |
2004年 | 155篇 |
2003年 | 119篇 |
2002年 | 131篇 |
2001年 | 80篇 |
2000年 | 63篇 |
1999年 | 42篇 |
1998年 | 24篇 |
1997年 | 20篇 |
1996年 | 15篇 |
1995年 | 31篇 |
1994年 | 15篇 |
1993年 | 14篇 |
1992年 | 10篇 |
1991年 | 9篇 |
1990年 | 15篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1983年 | 3篇 |
1967年 | 9篇 |
1966年 | 6篇 |
1965年 | 3篇 |
1964年 | 13篇 |
1963年 | 8篇 |
1962年 | 10篇 |
1960年 | 6篇 |
1959年 | 6篇 |
1958年 | 24篇 |
1957年 | 8篇 |
1956年 | 6篇 |
1955年 | 4篇 |
排序方式: 共有5504条查询结果,搜索用时 312 毫秒
991.
Venom-injecting structures have arisen independently in unrelated arthropods including scorpions, spiders, centipedes, larval owlflies and antlions, and Hymenoptera (wasps, ants, and bees). Most arthropods use venom primarily as an offensive weapon to subdue prey, and only secondarily in defense against enemies. Venom is injected by biting with fangs or stinging with a specialized hypodermic structure used exclusively for the delivery of venom (usually modified terminal abdominal segments). A true sting apparatus, previously known only in scorpions and aculeate wasps, is now known in a third group. We here report the first known case of a cerambycid beetle using its antennae to inject a secretion that causes cutaneous and subcutaneous inflammation in humans. Scanning electron microscopy revealed that the terminal antennal segment of Onychocerus albitarsis (Pascoe) has two pores opening into channels leading to the tip through which the secretion is delivered. This is a novel case of convergent evolution: The delivery system is almost identical to that found in the stinger of a deadly buthid scorpion. 相似文献
992.
Flower colour is an important signal used by flowering plants to attract pollinators. Many anthophilous insects have an innate colour preference that is displayed during their first foraging bouts and which could help them locate their first nectar reward. Nevertheless, learning capabilities allow insects to switch their colour preferences with experience and thus, to track variation in floral nectar availability. Manduca sexta, a crepuscular hawkmoth widely studied as a model system for sensory physiology and behaviour, visits mostly white, night-blooming flowers lacking UV reflectance throughout its range in the Americas. Nevertheless, the spectral sensitivity of the feeding behaviour of naïve moths shows a narrow peak around 450 nm wavelengths, suggesting an innate preference for the colour blue. Under more natural conditions (i.e. broader wavelength reflectance) than in previous studies, we used dual choice experiments with blue- and white-coloured feeders to investigate the innate preference of naïve moths and trained different groups to each colour to evaluate their learning capabilities. We confirmed the innate preference of M. sexta for blue and found that these moths were able to switch colour preferences after training experience. These results unequivocally demonstrate that M. sexta moths innately prefer blue when presented against white flower models and offer novel experimental evidence supporting the hypothesis that learning capabilities could be involved in their foraging preferences, including their widely observed attraction to white flowers in nature. 相似文献
993.
Ventral polarization vision in tabanids: horseflies and deerflies (Diptera: Tabanidae) are attracted to horizontally polarized light 总被引:1,自引:0,他引:1
Adult tabanid flies (horseflies and deerflies) are terrestrial and lay their eggs onto marsh plants near bodies of fresh water
because the larvae develop in water or mud. To know how tabanids locate their host animals, terrestrial rendezvous sites and
egg-laying places would be very useful for control measures against them, because the hematophagous females are primary/secondary
vectors of some severe animal/human diseases/parasites. Thus, in choice experiments performed in the field we studied the
behavior of tabanids governed by linearly polarized light. We present here evidence for positive polarotaxis, i.e., attraction
to horizontally polarized light stimulating the ventral eye region, in both males and females of 27 tabanid species. The novelty
of our findings is that positive polarotaxis has been described earlier only in connection with the water detection of some
aquatic insects ovipositing directly into water. A further particularity of our discovery is that in the order Diptera and
among blood-sucking insects the studied tabanids are the first known species possessing ventral polarization vision and definite
polarization-sensitive behavior with known functions. The polarotaxis in tabanid flies makes it possible to develop new optically
luring traps being more efficient than the existing ones based on the attraction of tabanids by the intensity and/or color
of reflected light. 相似文献
994.
Gómara B González MJ Baos R Hiraldo F Abad E Rivera J Jiménez B 《Environment international》2008,34(1):73-78
This study provides information on the current status of contamination by organochlorines (DDTs, PCBs, PCDDs and PCDFs) in the declining red kite (Milvus milvus L.) population breeding in the Do?ana National Park (DNP), south-western Spain. Analyses were performed in addled eggs collected between 1999 and 2001. DDE concentrations ranged from 0.1 to 33.5 microg/g ww, representing more than 86% of the total DDTs. Of the samples studied, 50% showed DDE levels above those associated with reproductive impairment in other raptor species. Concentrations of ortho PCBs (average 36.8 microg/g ww+/-37.7) in 50% of the eggs were much higher than levels reported to cause reduced hatching success, embryo mortality, and deformities in birds (>20 microg/g ww). It is remarkable that average ortho PCB and DDE concentrations showed an increase of one order of magnitude compared to previous data for the species during the 80s. Total PCDD/Fs showed levels in the low pg/g range (7.2-42 pg/g ww), having PCDDs and PCDFs similar contributions in most samples. Total mean TEQs were 238 pg/g (ww), being the range 7.02-667 pg/g (ww). Spatial variation within DNP was observed for PCBs, DDTs, as well as for TEQs. Since some eggs exceeded the NOEL (67%) and LOEL (33%) reported for other raptor species, we would expect the red kite to experience detrimental effects to dioxin-like toxicity. Our results suggest that organochlorine contaminants should be regarded as an element of concern in the population under study, in addition to other conservation problems already reported. Further investigations should be undertaken to identify potential sources of these chemicals in DNP, and to find out if organochlorine contamination is present in other predator species in the area, as well as their potential health effects on individuals and/or populations. 相似文献
995.
Alvarez-Pedrerol M Ribas-Fitó N Torrent M Carrizo D Garcia-Esteban R Grimalt JO Sunyer J 《Environment international》2008,34(6):737-740
OBJECTIVE: Thyroid hormones play an important role in human brain development, and some organochlorine compounds (OCs) act as thyroid disruptors. The objective of the present study was to evaluate the association between prenatal exposure to organochlorine compounds and thyroid function in newborns from a general population birth cohort in Menorca, with an a-priori specific focus on beta-HCH. METHODS: Levels of polychlorinated biphenyls (PCB congeners 28, 52, 101, 118, 138, 153 and 180), hexachlorobenzene (HCB), beta-hexachlorocyclohexane (beta-HCH), dichlorodiphenyl dichloroethylene (p'p'-DDE) and dichlorodiphenyl trichloroethane (p'p-DDT) in cord serum, and thyrotropin (TSH) concentration in plasma three days after birth were measured in 387 newborns from Menorca. The TSH concentration was categorized (high or low), except for 27 children whose TSH levels were quantified. RESULTS: Levels of beta-HCH and PCB-153 were positively related to TSH concentrations (gestational age-adjusted coefficient (p-value): 0.26 (p = 0.006) and 0.31 (p = 0.050), respectively). CONCLUSIONS: beta-HCH is potentially a new thyroid disrupting compound, deserving special interest in future studies given its high body burden in humans. 相似文献
996.
Gutiérrez-Villanueva JL Martín-Martín A Peña V Iniguez MP de Celis B de la Fuente R 《Journal of environmental radioactivity》2008,99(10):1520-1524
In situ gamma spectrometry provides a fast method to determine (137)Cs inventories in soils. To improve the accuracy of the estimates, one can use not only the information on the photopeak count rates but also on the peak to forward-scatter ratios. Before applying this procedure to field measurements, a calibration including several experimental simulations must be carried out in the laboratory. In this paper it is shown that Monte Carlo methods are a valuable tool to minimize the number of experimental measurements needed for the calibration. 相似文献
997.
In the Harghita volcanic range (Romania) there are many occurrences of dry CO(2) emanations, called mofettes. The emanating gas with high carbon dioxide content has a proved curative effect. The gas also contains important quantities of radon. Since the mofettes are used in curative purposes in several illnesses, in most of the cases without medical supervising, has been proposed to determine the radon activity concentration in some of the most frequented mofettes from Romania. The seasonal variations have also been monitored and were calculated the effective doses received by the patients during a cure. The radon activity concentrations' levels above the mofettes indoor air range between 548 and 10 717Bq/m(3) while within the gas pools' values between 3210 and 32 781Bq/m(3) have been measured. The effective dose received by the patients during a cure is between 0.0086 and 0.16mSv. No major seasonal variations of the radon activity concentrations levels have been pointed out so far in the studied mofettes. 相似文献
998.
Bazała MA Gołda K Bystrzejewska-Piotrowska G 《Journal of environmental radioactivity》2008,99(7):1200-1202
We present a new protocol to study fluxes of radionuclides and other xenobiotics in saprophytic fungi. This simple method has successfully been used to evaluate transport of radiocesium in hyphae of Pleurotus eryngii and its translocation to fruitbodies. 相似文献
999.
Research into landscape history makes it possible to follow landscape changes in the past and support landscape management, conservation and restoration programs. Floodplain habitats are lost, isolated and fragmented on account of land use. Nowadays, these habitats are threatened by modifications in the natural water regime, as well as agricultural and forestry practices. Floodplains have great importance because they provide a transition between aquatic habitats and terrestrial biotopes. Our analysis of aerial photographs and topographical maps revealed that the major predicted changes in the study area are related to agricultural abandonment and afforestation. The comparison of land cover maps from 1784 to 2005 showed intensification of agriculture with land cover conversions from arable land and orchards to grasslands, marshes and woodlands. The land use types that are mostly responsible for the fragmentation of the landscape are arable land, economic plantations and orchards. We found that fragmentation was greater after 1956. This was caused by socioeconomic changes and showed that the habitats of floodplains have changed intensively during the last 200 years. Knowledge of this last 200 years of history contributes to a more careful and wiser management of the region through biodiversity protection and environmental development. 相似文献
1000.
Monterroso I Binimelis R Rodríguez-Labajos B 《Journal of environmental management》2011,92(3):494-507
The study described in this article incorporates stakeholders' views on aquatic invasion processes and combines expert analysis with information from field work into an evaluation exercise. Management scenarios are designed based on available technical data and stakeholders' perceptions. These scenarios are evaluated using the Social Multi-Criteria Evaluation framework employing the NAIADE model. Two evaluations are carried out, technical and social. Social acceptance of different management scenarios, distribution of costs and benefits, and attribution of responsibility are discussed. The case study was carried out on Lake Izabal, a body of water connected to the Caribbean Sea in Northeastern Guatemala. In 2000, local fishermen reported the presence of an alien species in the lake, the macrophyte Hydrilla verticillata. Two years later, this alien species was established around the entire lakeshore, damaging the ecosystem, endangering native species and the subsistence of local inhabitants through impacts on transportation, fishing practices, and tourism. 相似文献