全文获取类型
收费全文 | 126591篇 |
免费 | 2408篇 |
国内免费 | 10200篇 |
专业分类
安全科学 | 5911篇 |
废物处理 | 5352篇 |
环保管理 | 17297篇 |
综合类 | 36450篇 |
基础理论 | 31609篇 |
环境理论 | 84篇 |
污染及防治 | 27907篇 |
评价与监测 | 7090篇 |
社会与环境 | 5609篇 |
灾害及防治 | 1890篇 |
出版年
2023年 | 846篇 |
2022年 | 2012篇 |
2021年 | 1872篇 |
2020年 | 1514篇 |
2019年 | 1584篇 |
2018年 | 2207篇 |
2017年 | 2466篇 |
2016年 | 3355篇 |
2015年 | 3237篇 |
2014年 | 4624篇 |
2013年 | 11823篇 |
2012年 | 4846篇 |
2011年 | 5650篇 |
2010年 | 5313篇 |
2009年 | 5458篇 |
2008年 | 4838篇 |
2007年 | 4513篇 |
2006年 | 4436篇 |
2005年 | 3844篇 |
2004年 | 3896篇 |
2003年 | 3890篇 |
2002年 | 3349篇 |
2001年 | 3730篇 |
2000年 | 3160篇 |
1999年 | 2487篇 |
1998年 | 2112篇 |
1997年 | 2036篇 |
1996年 | 2103篇 |
1995年 | 2142篇 |
1994年 | 1875篇 |
1993年 | 1723篇 |
1992年 | 1633篇 |
1991年 | 1532篇 |
1990年 | 1452篇 |
1989年 | 1340篇 |
1988年 | 1181篇 |
1987年 | 1070篇 |
1986年 | 1041篇 |
1985年 | 1112篇 |
1984年 | 1206篇 |
1983年 | 1204篇 |
1982年 | 1206篇 |
1981年 | 1126篇 |
1980年 | 960篇 |
1979年 | 963篇 |
1978年 | 833篇 |
1977年 | 739篇 |
1976年 | 669篇 |
1973年 | 682篇 |
1972年 | 685篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
981.
Distribution of actinomycetes in oil contaminated ultisols of the Niger Delta (Nigeria) 总被引:1,自引:0,他引:1
J.P.Essien 《环境科学学报》2000,12(3):296-302
The distribution of actinomycetes in oil contaminated sandy loam ultisols of the Niger Delta region of Nigeria was studied to aid in understanding the effect of hydrocarbons on indigenous microbial population in tropical soils. The average total counts of actinomycetes in all the oil samples analysed was 103 cfu/g. Higher counts of actinomycetes were observed during the dry season than during the wet season. The counts of hydrocarbonoclastic actinomycetes correlated positively with the total count of actinomycetes.The actinomycetes were generally restricted to the top soil(0-10 cm soil depth) although a seemingly deeper(down to 40 cm soil depth) distribution was noticed in the dry season. The isolates included oil degrading species of Actinoplanes, Norcadia,Streptomyces and Streptosporangium. Their high oil utilization ability indicates their positive potential and role in the bioremediation of oil-spilled soils. 相似文献
982.
983.
A series of highly-hydrophobic MIL-53-Al (MIL = Materials of Institut Lavoisier) frameworks synthesized via decoration of the Al-OH groups by alkyl phosphonic acid were developed as adsorbents for removing acetone from humid gas streams. The newly prepared materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), N2 adsorption-desorption and thermogravimetric analysis (TGA). Their adsorption behaviors toward acetone vapor under dry and wet conditions were studied subsequently. Results showed that alkyl phosphonic acid was successfully grafted into MIL-53-Al skeleton through coordinating interaction with Al3+ generating [email protected]x (x = 12, 14, 18). The [email protected]x exhibited similar crystal structure and thermal stability to parent MIL-53-Al. Furthermore, the modified materials showed significantly enhanced hydrophobicity. The water vapor uptake of [email protected]14 decreased by 72.55% at 75% relative humidity (RH). Dynamic adsorption experiments demonstrated that water vapor had almost no effect on the acetone adsorption performance of [email protected]14. Under the condition of 90% RH, the acetone adsorption capacity of [email protected]14 was 102.98% higher than that of MIL-53-Al. Notably, [email protected]14 presented excellent adsorption reversibility and regeneration performance in 10 adsorption-desorption cycles. Taken together, the strategy of metal-OH group modification is an attractive way to improve the acetone adsorption performance over metal-organic frameworks (MOFs) under humid conditions. Besides, [email protected]14 would be deemed as a promising candidate for capturing acetone in high moisture environment. 相似文献
984.
汕头港水域温排水热扩散的三维数值模拟 总被引:8,自引:1,他引:8
本文建立了汕头港水域温排水扩散的三维数学模型,并采用特征差分方法求其解,对该法在三维情况下的稳定作了推导,给出了判断公式,上述模型被应用于汕头热电厂废热水排放的环境影响评价中,实例计算表明,该模型算法程序简单,计算结果合理。 相似文献
985.
Supplementing the nutrient requirement of crops through organic manures plays a key role in sustaining soil fertility, and crop productivity and reducing use of fossil fuels. Field experiments were conducted for 2 years at two different locations (i.e. Lucknow and Pantnagar) in Uttar Pradesh, India. The objectives of the study were to assess the herb and essential oil yields of Japanese mint (Mentha arvensis cv. Hy 77), and its nutrient accumulation under single and combined applications of organic manures and inorganic fertilizers (NPK). Changes in physical and chemical characteristics of the soils (Fluvisols, Mollisols) were also determined. Eight treatments comprising different combinations of NPK through inorganic fertilizers and farm yard manure (FYM) were compared. The distilled waste of mint after extraction of essential oil was recycled to soils in the plots to supplement the nutritional requirement of the succeeding mustard crop (Brassica juncea cv. Pusa Bold). Herb and essential oil yield of mint were significantly higher with combined application of organic and inorganic sources of nutrients as compared to single applications. Accumulation of N and P was at par under full inorganic and combined supply whereas, K accumulation was higher with the former. Soil organic C and pH after harvest of mint did not significantly differ among the treatments, but the level of mineralizable N, Olsen-P and NH4OAc extractable K were higher in soil with integrated supply of nutrients. Significant increase in soil water stable aggregates, organic C, available NPK and microbial biomass, and decrease in soil bulk density were observed with waste recycling over fertilizer application. These benefits were reflected in the seed and stubble yield of mustard which succeeded mint. This study indicates that combined application of inorganic fertilizers with organics helps in increasing the availability of nutrients and crop yield and provides a significant effect to the succeeding crop. Similarly, recycling crop residues reduces the need for fossil fuel based fertilizer, and helps in sustaining and restoring soil fertility in terms of available nutrients and major physical and chemical characteristics of the soil. 相似文献
986.
Nectar acquisition in the honeybee Apis mellifera is a partitioned task in which foragers gather nectar and bring it to the hive, where nest mates unload via trophallaxis
(i.e. mouth-to-mouth transfer) the collected food for further storage. Because forager mates exploit different feeding places
simultaneously, this study addresses the question of whether nectar unloading interactions between foragers and hive-bees
are established randomly, as it is commonly assumed. Two groups of foragers were trained to exploit a different scented food
source for 5 days. We recorded their trophallaxes with hive-mates, marking the latter ones according to the forager group
they were unloading. We found non-random probabilities for the occurrence of trophallaxes between experimental foragers and
hive-bees, instead, we found that trophallactic interactions were more likely to involve groups of individuals which had formerly
interacted orally. We propose that olfactory cues present in the transferred nectar promoted the observed bias, and we discuss
this bias in the context of the organization of nectar acquisition: a partitioned task carried out in a decentralized insect
society. 相似文献
987.
论DNA分子标记在家畜遗传多样性保护中的应用 总被引:1,自引:0,他引:1
本文就DNA分子遗传标记在家畜遗传多样性保护中应用的可行性及途径进行了探讨,提出了家畜遗传多样性标记辅助保护新策略。 相似文献
988.
Quantitativestructure-activitystudyonthereductivedehalogenationpotencyofthehalogenatedaromaticsHuangQingguo;WangLiansheng;Han... 相似文献
989.
EffectofacidprecipitationonleachingofnutritionsandaluminiumfromforestsoilsDaiZhaohua;LiaoBohan;WangZhihaiWangXingjun;LiuYunxi... 相似文献
990.