全文获取类型
收费全文 | 556篇 |
免费 | 70篇 |
国内免费 | 84篇 |
专业分类
安全科学 | 73篇 |
废物处理 | 15篇 |
环保管理 | 87篇 |
综合类 | 366篇 |
基础理论 | 77篇 |
污染及防治 | 42篇 |
评价与监测 | 21篇 |
社会与环境 | 13篇 |
灾害及防治 | 16篇 |
出版年
2024年 | 4篇 |
2023年 | 6篇 |
2022年 | 11篇 |
2021年 | 22篇 |
2020年 | 20篇 |
2019年 | 15篇 |
2018年 | 10篇 |
2017年 | 17篇 |
2016年 | 17篇 |
2015年 | 28篇 |
2014年 | 43篇 |
2013年 | 47篇 |
2012年 | 57篇 |
2011年 | 32篇 |
2010年 | 28篇 |
2009年 | 33篇 |
2008年 | 32篇 |
2007年 | 52篇 |
2006年 | 38篇 |
2005年 | 35篇 |
2004年 | 28篇 |
2003年 | 19篇 |
2002年 | 24篇 |
2001年 | 15篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有710条查询结果,搜索用时 31 毫秒
601.
Summary Feeding by the homopteranPsylla pyricola on leaves of pear trees induces the production of volatile compounds, such as (E,E)--farnesene and methyl-salicylate, as well as the production of polyphenols. The inference on induction is based on GC-MS and HPLC chromatograms from the same samples ofPsylla infested leaves, leaves from the same pear tree beforePsylla infestation and uninfested leaves from other pear trees.Psylla infestation greatly enhanced the production of volatiles ((E,E)--farnesene, methyl-salicylate and others) and triggered the production of new polyphenols, characterized by much longer retention times.However, the responses to infestation depend critically on leaf age (defined by leaf distance to apex). With respect to the leaf volatiles it appears that infested, old leaves produce fewer compounds and lower amounts of the volatiles than infested, young leaves. Moreover, there seem to be differences in pattern. Relative to (E,E)--farnesene, methyl-salicylate was found in much lower amounts in heavily infested, old leaves. With respect to polyphenols it was found that infested old leaves collected in August have polyphenols with the same retention times, but more or less equal amounts as uninfested young leaves collected in May. This shows thatPsylla infestation causes the induced response mostly in young leaves.The induced leaf volatiles may act as synomones to heteropteran bugs. As shown elsewhere,Anthocoris nemoralis responds significantly to (E,E)--farnesene and methyl-salicylate when offered in pure form against clean air in a Y-tube olfactometer. The effect of polyphenols on the performance ofP. pyricola is not yet known. Hence, a role in direct defence is still to be investigated. 相似文献
602.
工业雷管在生产、贮运、使用过程中存在意外发火或爆炸事故。为了防止这种突然事件和避免带来的伤害与损失,笔者就可能导致意外起爆的各种原因进行了分析,提出了各种相应的防范措施和意见 相似文献
603.
Allison E. Curry 《Traffic injury prevention》2017,18(1):35-40
Objectives: Current methods of estimating compliance with graduated driver licensing (GDL) restrictions among young drivers with intermediate driver's licenses—which include surveys, direct observations, and naturalistic studies—cannot sufficiently answer many critical foundational questions: What is the extent of noncompliance among the population of young intermediate drivers? How does compliance change over the course of licensure? How does compliance differ by driver subgroup and in certain driving environments? This article proposes an alternative and complementary approach to estimating population-level compliance with GDL nighttime and passenger restrictions via application of the quasi-induced exposure (QIE) method.Methods: The article summarizes the main limitations of previous methods employed to estimate compliance. It then introduces the proposed method of borrowing the fundamental assumption of the QIE method—that young intermediate drivers who are nonresponsible in clean (i.e., one and only one responsible driver) multivehicle crashes are reasonably representative of young intermediate drivers on the road—to estimate population-based compliance. I describe formative work that has been done to ensure this method can be validly applied among young intermediate drivers and provide a practical application of this method: an estimate of compliance with New Jersey's passenger restrictions among 8,006 nonresponsible 17- to 20-year-old intermediate drivers involved in clean 2-vehicle crashes from July 2010 through June 2012.Results: Over the study period, an estimated 8.4% (95% confidence interval, 7.8%, 9.0%) of intermediate drivers' trips were not in compliance with New Jersey's GDL passenger restriction. These findings were remarkably similar to previous estimates from more resource-intensive naturalistic studies (Goodwin et al. 2006; Klauer et al. 2011).Conclusion: Studies can practically apply proposed methods to estimate population-level compliance with GDL passenger and night restrictions; examine how compliance varies by relevant driver, vehicle, and environmental factors; and evaluate the implementation of a GDL provision or other intervention aimed at increasing compliance with these restrictions. Important considerations and potential limitations and challenges are discussed. 相似文献
604.
宫学栋 《中国环境管理干部学院学报》2000,(2)
我国环保系统人才的构成现状,决定了在职环境培训在一个相当长的时间内,仍是我国环保工作的一个重要组成部分。本文在分析在职环境培训情况的基础上,对今后进一步搞好培训工作提出了几点建议。 相似文献
605.
606.
607.
A new FAGE setup has recently been built at the University of Lille, France. It permits the quantification of OH and HO2 in the atmosphere with a detection limit of 3×105 molecules/(cm3·min) for OH and 1×106 molecules/(cm5·min) for HO2. Its coupling to a photolysis cell enables the measurement of the total reactivity of the hydroxyl radical in ambient air and kinetic studies in laboratory. Two configurations have been considered: one with the photolysis cell at 90° to the FAGE nozzle, the other on line with the FAGE nozzle. The two configurations have been tested and validated by measuring the well known rate constants of OH with CH4, C3H8 and CO. The advantages and drawbacks of each configuration have been evaluated. The “on line” configuration limits losses and permits measurements over a larger reactivity range but is affected by OH formation from the laser beam striking the FAGE nozzle, thus limiting the ability to carry out energy dependence studies which can, in contrast, be successfully performed in the 90° configuration. 相似文献
608.
Rod N. Millward 《Chemistry and Ecology》2013,29(1-3):115-127
The demonstration of an increased tolerance to a pollutant is direct evidence that this pollutant has presented a selection pressure upon a population or community. Recently, pollution-induced community tolerance (PICT) has been applied to the benthic community in a metal-enriched estuary to establish causal linkage between observed changes in community structure and composition and the presence of copper. This paper describes the rationale and methodology behind applying PICT to the marine benthic environment, and shows it to be a sensitive ecotoxicological tool. It also presents a case study, demonstrating how a PICT investigation has aided the interpretation of changes in a benthic community, establishing a causal linkage between these changes in the community and the presence of a specific pollutant. 相似文献
609.
简要介绍了淮安市四季青污水处理厂基本概况与主要设备,针对冬季雨雪天气及较低温度情况,对A曝与B曝所呈现的不同问题和现状进行了简述,并根据污泥负荷、效率变化等指标,得出了生物活性相对值随水温变化的曲线,同时还列举了构筑物、机械设备及仪表曾出现过的异常情况,提出了一些可行性对策与预防措施,如提前做好机械设备的维护与保养,在冬季加大A、B段污泥回流比,确保微生物处在较佳状态,从而保证出水达标。 相似文献
610.
壳聚糖对烟草抗黑胫病的作用 总被引:35,自引:0,他引:35
研究表明,壳聚糖除了对烟草黑胫病菌(Phytophthora parasitica)有抑制作用外,还能诱导烟草植株的抗病性。烟苗经浓度为0.5gL^-1和1gL^-1的壳聚糖处理4d后,诱导效应分别为78.56%和100%,用浓度为1gL^-1的壳聚糖处理烟草幼苗,叶片中的苯丙氨酸解氨酶(PAL)、过氧化物酶(PO)和多酶氧化酶(PPO)3种防御酶的活性均比CK有所提高。 相似文献