全文获取类型
收费全文 | 951篇 |
免费 | 106篇 |
国内免费 | 215篇 |
专业分类
安全科学 | 132篇 |
废物处理 | 18篇 |
环保管理 | 200篇 |
综合类 | 521篇 |
基础理论 | 130篇 |
环境理论 | 6篇 |
污染及防治 | 90篇 |
评价与监测 | 84篇 |
社会与环境 | 66篇 |
灾害及防治 | 25篇 |
出版年
2024年 | 2篇 |
2023年 | 19篇 |
2022年 | 17篇 |
2021年 | 29篇 |
2020年 | 36篇 |
2019年 | 40篇 |
2018年 | 36篇 |
2017年 | 53篇 |
2016年 | 52篇 |
2015年 | 45篇 |
2014年 | 50篇 |
2013年 | 88篇 |
2012年 | 77篇 |
2011年 | 83篇 |
2010年 | 60篇 |
2009年 | 69篇 |
2008年 | 49篇 |
2007年 | 55篇 |
2006年 | 60篇 |
2005年 | 49篇 |
2004年 | 29篇 |
2003年 | 43篇 |
2002年 | 37篇 |
2001年 | 37篇 |
2000年 | 17篇 |
1999年 | 32篇 |
1998年 | 19篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 12篇 |
1994年 | 13篇 |
1993年 | 15篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 7篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1272条查询结果,搜索用时 15 毫秒
991.
992.
介晓坤 《中国环境管理干部学院学报》2009,19(1):41-43
随着科学技术的进步,环境辐射已成为本世纪的主要污染源之一。本文重点介绍了电离辐射和电磁辐射的防护标准体系,针对它们的特点及不足提出:我国今后制定新的环境辐射防护标准时,应统一环境电磁波容许辐射强度的国家标准,建立相关产品的电磁辐射强度国家标准,制定相关环境辐射防护标准,从而完善辐射防护标准体系,加强环境保护。 相似文献
993.
Arróniz-Crespo M Núñez-Olivera E Martínez-Abaigar J 《Environmental pollution (Barking, Essex : 1987)》2008,151(1):8-16
We examined, under laboratory conditions, the physiological responses of the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia to artificially enhanced ultraviolet (UV) radiation for 82 days, especially considering the responses of five hydroxycinnamic acid derivatives. This species lives in mountain streams, where it is exposed to low temperatures and high UV levels, and this combination is believed to increase the adverse effects of UV. Enhanced UV radiation hardly caused any change in several physiological variables indicative of vitality, such as Fv/Fm and chlorophylls/phaeopigments ratio (OD430/OD410). Thus, this liverwort seemed to be tolerant to UV radiation, probably due to the accumulation of three UV-absorbing hydroxycinnamic acid derivatives: p-coumaroylmalic acid, 5'-(7',8'-dihydroxycoumaroyl)-2-caffeoylmalic acid, and 5'-(7',8'-dihydroxy-7-O-beta-glucosyl-coumaroyl)-2-caffeoylmalic acid. These compounds might serve as bioindicators of enhanced UV radiation. 相似文献
994.
J.-F. Mercier B.L. Tracy R. d'Amours F. Chagnon I. Hoffman E.P. Korpach S. Johnson R.K. Ungar 《Journal of environmental radioactivity》2009
It has long been observed that the environmental gamma-ray dose rate increases noticeably during precipitation intervals. This increase, due to the presence of radon progeny in the rain droplets (or snow flakes), can affect the reliability of the monitoring of artificial radioactivity and long term estimates of exposure to ambient natural radionuclides in surveillance network. Predicting the amplitude of the dose increase has been shown to be surprisingly challenging. In this work, standard air mass back trajectory analysis is used to show that the amplitude of the increase can be quantitatively linked to the history of the air mass where the precipitation is occurring. Furthermore, we show how back trajectory analysis, environmental gamma and rain data can be used to obtain estimations of relative radon emanation rates for locations far from the actual point of detection. 相似文献
995.
Little EE Calfee RD Theodorakos P Brown ZA Johnson CA 《Environmental science and pollution research international》2007,14(5):333-337
Background Cobalt cyanide complexes often result when ore is treated with cyanide solutions to extract gold and other metals. These have
recently been discovered in low but significant concentrations in effluents from gold leach operations. This study was conducted
to determine the potential toxicity of cobalt-cyanide complexes to freshwater organisms and the extent to which ultraviolet
radiation (UV) potentiates this toxicity. Tests were also conducted to determine if humic acids or if adaptation to UV influenced
sensitivity to the cyanide complexes.
Methods Rainbow trout (Oncorhynchus mykiss), Daphnia magna, and Ceriodaphnia dubia were exposed to potassium hexacyanocobaltate in the presence and absence of UV radiation, in the presence and absence of
humic acids. Cyano-cobalt exposures were also conducted with C. dubia from cultures adapted to elevated UV.
Results With an LC50 concentration of 0.38 mg/L, cyanocobalt was over a 1000 times more toxic to rainbow trout in the presence of
UV at a low, environmentally relevant irradiance level (4 μW/cm2 as UVB) than exposure to this compound in the absence of UV with an LC50 of 112.9 mg/L. Toxicity was immediately apparent,
with mortality occurring within an hour of the onset of exposure at the highest concentration. Fish were unaffected by exposure
to UV alone. Weak-acid dissociable cyanide concentrations were observed in irradiated aqueous solutions of cyanocobaltate
within hours of UV exposure and persisted in the presence of UV for at least 96 hours, whereas negligible concentrations were
observed in the absence of UV. The presence of humic acids significantly diminished cyanocobalt toxicity to D. magna and reduced mortality from UV exposure. Humic acids did not significantly influence survival among C. dubia. C. dubia from UV-adapted populations were less sensitive to metallocyanide compounds than organisms from unadapted populations.
Conclusions The results indicate that metallocyanide complexes may pose a hazard to aquatic life through photochemically induced processes.
Factors that decrease UV exposure such as dissolved organic carbon or increased pigmentation would diminish toxicity. 相似文献
996.
997.
Summary. Recent advances in both the systematics and the natural products chemistry of the order Sacoglossa (=Ascoglossa) in the gastropod
subclass Opisthobranchia suggest a revised and improved historical account of the evolution of the group. Although the algal
genus Caulerpa makes a suitable model for the ancestral food of the order, other siphonaceous algae are consistent with both morphological
and chemical data. At an early evolutionary stage terpenoids are sequestered from the food, and used defensively, often with
modification. With an evolutionary switch to different kinds of algal food, there is often a shift to other, related defensive
chemicals. A switch to new food source sometimes leads to the abandonment of chemical defense, but in other cases there is
de-novo synthesis of defensive metabolites. The synthesis of polypropionates, which are used defensively, occurs in some other gastropods,
but otherwise is known only in fungi. The systematic distribution of the defensive polypropionates suggests that their defensive
use has evolved several times among gastropods. Failure to detect them may mean that synthetic capacity has evolved more than
once, or it may mean that they exist at low levels, perhaps having a non-defensive function.
Received 9 February 1998; accepted 20 March 1998. 相似文献
998.
铊在黄铁矿中的相态分布及碳酸盐在其释放过程中的作用 总被引:2,自引:0,他引:2
采用分级提取-电感耦合等离子体质谱法,对黄铁矿中铊的相态分布进行了考察.结果表明,黄铁矿中的铊主要以存在于硅酸盐相中和以酸可交换的形式存在于矿物结构中的铊为主,这部分铊分别占到58.3%和25.1%;以可氧化态形式结合在黄铁矿(FeS2)中的铊次之,占11.2%;以易还原态形式存在于铁氧化物相中的铊最少,为5.4%.自然条件下铊的释放主要是酸可交换态铊和可氧化态铊的释放迁移过程.漫反射红外光谱表征发现,黄铁矿在表面氧化过程中其表面羟基增多,表明存在表面溶解及表面酸化现象.进一步的释放机理探讨认为,铊在黄铁矿表面存在一种"溶解-吸附沉淀"平衡,这一平衡由碳酸盐中和作用和黄铁矿表面氧化共同控制,并决定了铊的释放迁移. 相似文献
999.
通过生物化学的方法,研究了UV-B辐射对亚历山大藻(Alexandrium tamarense)生长及其可溶性蛋白、叶绿素a、H2O2、丙二醛(MDA)含量和超氧化物歧化酶(SOD)活力的影响.结果表明:UV-B辐射会抑制亚历山大藻的生长并对其生理生化特征产生明显的影响;经过UV-B辐射后,可溶性蛋白和叶绿素a含量呈现降低的趋势;H2O2、丙二醛含量和超氧化物歧化酶活力呈现升高的趋势;UV-B辐射产生过量的活性氧自由基是导致亚历山大藻受损伤的主要原因. 相似文献
1000.
根据5G基站工作原理及发射特点,研究了5G基站的电磁辐射方向、强度与用户终端位置分布及应用场景存在的对应关系.经实测验证,终端位置移动将导致电磁辐射方向发生显著变化;多终端窄波辐射相互叠加与应用场景明显相关,基站小区辐射覆盖范围扩大.建议对现行移动通信基站电磁辐射环境监测技术方法进行研究修订. 相似文献