全文获取类型
收费全文 | 929篇 |
免费 | 105篇 |
国内免费 | 423篇 |
专业分类
安全科学 | 71篇 |
废物处理 | 43篇 |
环保管理 | 118篇 |
综合类 | 718篇 |
基础理论 | 165篇 |
污染及防治 | 225篇 |
评价与监测 | 57篇 |
社会与环境 | 52篇 |
灾害及防治 | 8篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 26篇 |
2021年 | 26篇 |
2020年 | 22篇 |
2019年 | 31篇 |
2018年 | 21篇 |
2017年 | 37篇 |
2016年 | 52篇 |
2015年 | 53篇 |
2014年 | 71篇 |
2013年 | 106篇 |
2012年 | 92篇 |
2011年 | 101篇 |
2010年 | 82篇 |
2009年 | 100篇 |
2008年 | 62篇 |
2007年 | 91篇 |
2006年 | 96篇 |
2005年 | 54篇 |
2004年 | 54篇 |
2003年 | 44篇 |
2002年 | 29篇 |
2001年 | 32篇 |
2000年 | 29篇 |
1999年 | 21篇 |
1998年 | 18篇 |
1997年 | 14篇 |
1996年 | 19篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有1457条查询结果,搜索用时 15 毫秒
991.
研究了温度、酸碱度对重组杆状病毒(AcMNPV-BmKIT-Chi)毒力的影响.结果显示,多角体病毒在温度4~50℃,pH6.0~8.0范围内可以保持较高的毒力稳定性;不同虫龄棉铃虫幼虫对重组病毒的毒力敏感性差异显著,低虫龄对重组核型多角体病毒更为敏感;病毒对幼虫存在亚致死作用,饲毒组与对照组幼虫体重差异显著.图3表3参13 相似文献
992.
Massad RS Loubet B Tuzet A Cellier P 《Environmental pollution (Barking, Essex : 1987)》2008,154(3):390-403
The ammonia stomatal compensation point of plants is determined by leaf temperature, ammonium concentration ([NH4+]apo) and pH of the apoplastic solution. The later two depend on the adjacent cells metabolism and on leaf inputs and outputs through the xylem and phloem. Until now only empirical models have been designed to model the ammonia stomatal compensation point, except the model of Riedo et al. (2002. Coupling soil-plant-atmosphere exchange of ammonia with ecosystem functioning in grasslands. Ecological Modelling 158, 83-110), which represents the exchanges between the plant's nitrogen pools. The first step to model the ammonia stomatal compensation point is to adequately model [NH4+]apo. This [NH4+]apo has been studied experimentally, but there are currently no process-based quantitative models describing its relation to plant metabolism and environmental conditions. This study summarizes the processes involved in determining the ammonia stomatal compensation point at the leaf scale and qualitatively evaluates the ability of existing whole plant N and C models to include a model for [NH4+]apo. 相似文献
993.
Al(Ⅲ) speciation distribution and transformation in high concentration PACl solutions 总被引:1,自引:0,他引:1
Effects of Al(Ⅲ) concentration and pH on the speciation of Al(Ⅲ) in polyaluminum chloride (PACl) solutions especially on the Al13 fraction were investigated. A series of PACl samples were prepared over the range of Al(Ⅲ) concentration from 0.01 to 2.0 mol/L with the B (OH/Al ratio) value from 1.0 to 2.5 by forced hydrolysis of AICl3. The samples were characterized by ferron assay, pH and 27^Al NMR. It was shown that the Al(Ⅲ) concentration had a dramatic effect on the hydrolysis processes and the species distribution of PACl was in relate to the decrease of pH. The fraction of Al species, Alb (or Al13) decreased and Al0 increased with increase of total Al(Ⅲ) concentration. Under the condition of Al(Ⅲ) 2.0 reel/L, B = 2.5, the pH value was 2.73 and no Al13 could be detected. During diluting and aging, the species distribution evoIved. The Al13 could then be detected again and the amounts increased with time. If the diluted samples were concentrated by freeze dry at -35℃ or heating at 80℃, the pH value and Al13 content would decrease with the increased concentration. It demonstrated that the key factor for formation of Al13 in concentrated PACl was pH value. 相似文献
994.
医药行业对药品生产的纯度控制相当重要,蒸馏操作是医药行业普遍运用的工艺手段之一.但由于蒸馏工序所涉及的物料常伴随具有较强燃爆性的危险化学品,且闪点以上操作加剧了物料的燃爆危险,因此医药行业蒸馏系统便成了事故多发的工艺单元之一.通过对某公司蒸馏系统的危险性分析,找出了蒸馏系统存在燃爆危险的主要因素,再进一步采用蒸汽云爆炸事故模拟评价方法,结合拉乌尔定律和道尔顿分压定律对该公司蒸馏系统进行安全评价,确定蒸馏系统二元混合物蒸气云爆炸冲击波损害半径. 相似文献
995.
996.
997.
针对采用《水质氨氮的测定纳氏试剂分光光度法》(HJ 535—2009)测定低浓度氨氮时存在的测不准问题,研究了药剂投加量、反应时间等因素对检测结果的影响,认为低浓度氨氮下的显色反应速度过慢是测定结果不准的原因,并据此提出利用强碱调节pH的方法加速反应进程。改良后的方法可以在0.2~1.2 mg/L氨氮浓度范围内呈现良好的线性关系,相关系数r为0.999 4。该方法具有较高的准确度和精密度,有效扩大了低浓度氨氮的检测范围,在实际样品检测中的回收率为102.5%~115.0%,可为准确测定水环境和饮用水中的氨氮浓度提供一种简便易行的手段。 相似文献
998.
PCP(pentachlorophenol,五氯酚)是一种可电离有机化合物,pH会影响水体中PCP的毒性.为准确评估沉积物中PCP的生态风险,通过研究不同pH下沉积物中PCP对河蚬(Corbicula fluminea)、泥鳅(Misgurnus anguillicaudatus)、伸展摇蚊(Chironomus riparius)等底栖生物的毒性效应,探讨沉积物中PCP生物毒性与pH的关系.基于毒性试验结果和搜集筛选文献中报道的PCP生物毒性数据,利用物种敏感度分布法推导PCP沉积物质量基准,进而对我国淡水水体沉积物中PCP风险进行评估.结果表明:①沉积物中PCP对底栖生物的毒性均随pH的升高而降低,pH为6.5~8.5时,沉积物中PCP对河蚬、泥鳅、伸展摇蚊的96 h-LC50值分别为2.99~7.64、8.05~8.76、10.50~22.30 μg/g;对泥鳅的30 d-LC10值为0.26~0.80 μg/g,对伸展摇蚊的21 d-EC10值为0.28~0.54 μg/g.②推导获得PCP依赖于pH的沉积物质量基准函数,即CMCsed(急性基准值)=e0.204pH-2.96、CCCsed(慢性基准值)=e0.204pH-5.85,当pH为7.0时,CMCsed、CCCsed分别为0.217、0.012 μg/g.③我国主要淡水河流、湖泊沉积物中99.0%的采样点w(PCP)低于该研究推导的CCCsed,仅有1.0%的采样点w(PCP)介于CCCsed与CMCsed之间.研究显示,我国主要淡水水体沉积物中PCP总体风险较低,个别地区沉积物中PCP可能存在潜在的生态风险,需要引起重视. 相似文献
999.
Understanding Stream Geomorphic State in Relation to Ecological Integrity: Evidence Using Habitat Assessments and Macroinvertebrates 总被引:2,自引:0,他引:2
Scientists have long assumed that the physical structure and condition of stream and river channels have pervasive effects on biological communities and processes, but specific tests are few. To investigate the influence of the stream-reach geomorphic state on in-stream habitat and aquatic macroinvertebrate communities, we compared measures of habitat conditions and macroinvertebrate community composition between stable and unstable stream reaches in a paired-study design. We also explored potential associations between these ecological measures and individual geomorphic characteristics and channel adjustment processes (degradation, aggradation, overwidening, and change in planform). We found that habitat quality and heterogeneity were closely tied to stream stability, with geomorphically stable reaches supporting better habitat than unstable reaches. Geomorphic and habitat assessment scores were highly correlated (r = 0.624, P < 0.006, n = 18). Stable reaches did not support significantly greater macroinvertebrate densities than unstable reaches (t = −0.415, P > 0.689, df = 8). However, the percent of the macroinvertebrate community in the Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa was significantly correlated with the overall habitat assessment scores as well as with individual measures of geomorphic condition and habitat quality. While there is a clear need for more work in classifying and quantifying the responses of aquatic and aquatic-dependent biota to various geomorphic states and processes, this study provides solid preliminary evidence that macroinvertebrate communities are affected by the geomorphic condition of the stream reaches they inhabit and that geomorphic assessment approaches can be used as a tool for evaluating ecological integrity. 相似文献
1000.