全文获取类型
收费全文 | 381篇 |
免费 | 17篇 |
国内免费 | 38篇 |
专业分类
安全科学 | 41篇 |
废物处理 | 2篇 |
环保管理 | 18篇 |
综合类 | 216篇 |
基础理论 | 101篇 |
污染及防治 | 18篇 |
评价与监测 | 4篇 |
社会与环境 | 33篇 |
灾害及防治 | 3篇 |
出版年
2024年 | 2篇 |
2023年 | 1篇 |
2022年 | 9篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 11篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 17篇 |
2012年 | 18篇 |
2011年 | 14篇 |
2010年 | 19篇 |
2009年 | 27篇 |
2008年 | 30篇 |
2007年 | 20篇 |
2006年 | 17篇 |
2005年 | 16篇 |
2004年 | 20篇 |
2003年 | 17篇 |
2002年 | 6篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 9篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1981年 | 1篇 |
排序方式: 共有436条查询结果,搜索用时 329 毫秒
181.
不同年龄夜鹭卵中有机氯农药污染的生物指示 总被引:7,自引:0,他引:7
通过对太湖鼋头渚 2 0 0 0年采集的二龄、三龄和四龄夜鹭卵以及相应年龄组夜鹭的捕食物中有机氯残留的检测 ,发现捕食物中HCH和DDT的平均残留量随年龄增加而增加 .除γ HCH外 ,其它 15种有机氯农药在卵样中均有检出 ,残留水平最高的为p ,p′ DDE ,占有机氯农药残留总量的 85 %以上 .β HCH是六六六类中持留性最强的组分 ,其残留量仅次于p ,p′ DDE .研究发现 ,p ,p DDT和 β HCH检出率为 10 0 % ,而其它类型农药只有很低的检出率 ,这与我国有机氯农药使用的历史情况相吻合 .随着亲鸟年龄增加 ,卵中 β HCH残留量有所提高 ,p ,p′ DDE残留量似有先升后稍降的趋势 .统计结果表明 :各年龄组有机氯残留量差异不明显 ,因此在用夜鹭卵作有机氯污染的生物指示时可以不考虑年龄差异所带来的影响 . 相似文献
182.
鼋头渚不同年龄夜鹭卵中多氯联苯污染状况及分布特征 总被引:4,自引:1,他引:3
通过对太湖鼋头渚2000年采集的2龄、3龄和4龄夜鹭所产卵中15种多氯联苯同系物残留状况的研究,发现所有样品中均检出多氯联苯,残留量最高的为PCB118,PCB87,PCB101和PCB153,占PCBs残留量的75%~85%.含5~6个氯原子的同系物在夜鹭卵中的PCBs残留量明显高于其它类型的同系物.同时,多氯联苯残留量随亲鸟年龄增加而明显增加.4龄卵样分别比3龄、2龄卵样中PCBs残留量高出47.5%和60.9%.统计处理结果表明:多氯联苯残留总量与亲鸟年龄呈正相关(p=0.05).PCBs总量与亲鸟年龄呈正相关(p=0.05).与欧美日等国家同类研究结果中PCB153残留量最高的情况略有不同,本研究在夜鹭卵中发现残留量最高的是PCB118,占PCBs残留总量的30%左右,PCB153含量仅为PCBs残留总量的17%左右. 相似文献
183.
This article attempts to examine the influence of some selected predictor variables on female age at first marriage in slum areas of Bangladesh. A path and multiple classification analysis (MCA) approach have been adopted. Authors thought that respondent's educational level and the mass media such as watching television have a significant direct impact on age at marriage, while the types of family and occupational status have an indirect effect on age at marriage. 相似文献
184.
P. V. Akatov 《Russian Journal of Ecology》2009,40(1):33-38
To estimate the response of tree vegetation to recent climate warming in the Western Caucasus, the population state of several tree species at the upper limit of their distribution has been estimated in three mountain massifs in the Belaya River basin. For this purpose, the average and maximum stem diameters, vitality, and age of trees have been determined in the transitional zone between middle-mountain and high-mountain beech-fir forests (1400–1700 m a.s.l.) and in crooked birch forests growing at the upper timberline (1810–2025 m). The upper limits of Acer platanoides, A. pseudoplatanus, Ulmus glabra, and Betula litwinowii have shown a tendency to rise. The upper limit of Abies nordmanniana has remained unchanged over the past few decades, which may be explained by a decrease in moisture supply during the warm season. 相似文献
185.
186.
E. Z. Cameron W. L. Linklater K. J. Stafford E. O. Minot 《Behavioral ecology and sociobiology》2000,47(4):243-249
In many mammalian species, female success in raising offspring improves as they age. The residual reproductive value hypothesis
predicts that each individual offspring will be more valuable to the mother as she ages because there is less conflict between
the current and potential future offspring. Therefore, as mothers age, their investment into individual offspring should increase.
Empirical evidence for an influence of declining residual reproductive value on maternal investment is unconvincing. Older
mothers may not invest more, but may be more successful due to greater experience, allowing them to target their investment
more appropriately (targeted reproductive effort hypothesis). Most studies do not preclude either hypothesis. Mare age significantly
influenced maternal investment in feral horses living on the North Island of New Zealand. Older mares, that were more successful
at raising foals, were more protective for the first 20 days of life, but less diligent thereafter. Total maternal input by
older mothers did not seem to be any greater, but was better targeted at the most critical period for foal survival and a
similar pattern was observed in mares that had lost a foal in the previous year. In addition, older mothers were more likely
to foal in consecutive years, supporting the hypothesis that they are investing less than younger mares in individual offspring.
Therefore, older mothers seem to become more successful by targeting their investment better due to experience, not by investing
more in their offspring.
Received: 22 September 1999 / Received in revised form: 30 October 1999 / Accepted: 6 November 1999 相似文献
187.
188.
低C/N城市污水亚硝酸型硝化试验研究 总被引:1,自引:0,他引:1
对低C/N城市污水进行亚硝酸型硝化的可行性、稳定性进行了研究,具体研究了系统的启动培养、稳定亚硝化、污泥毒害、短暂亚硝化、污泥适应等5个阶段及污泥的适应性问题。低C/N城市污水可实现稳定的亚硝酸型硝化,其亚硝化率最高可达90%。试验中合理确定反应周期的首要因素是系统出水NH4+-N的浓度至少达到50%降解率,其次是出水中NOx-NN应主要以NO2-N为主。根据泥龄维持所能维持的MLSS浓度确定系统泥龄在合理范围。系统不排泥和较长泥龄将不能通过排泥,将系统中硝化菌"洗出",硝化菌也会最终适应亚硝酸型硝化的环境因素,从而导致亚硝酸型硝化现象的不可逆消失。杆状污泥絮体为亚硝酸型硝化现象的特征污泥相。 相似文献
189.
190.
低溶解氧下SBR内短程硝化影响因素试验研究 总被引:4,自引:1,他引:4
为了明确低溶解氧下短程硝化的其它控制因素,文章采用序批式反应器(SBR)系统研究了低溶解氧下实现短程硝化影响因素的控制范围。试验结果表明:SBR内较高的游离氨浓度(0.50~20.73 mg/L)对亚硝酸的积累起到一定促进作用;实现低溶解氧下短程硝化的温度和泥龄范围较大,在温度为21~30℃、泥龄为15~40 d的范围内都可以实现稳定的短程硝化,实验过程中亚硝酸积累率一直维持在80%以上;有机物的存在对氨氧化速率影响不大,但高有机物浓度(COD为900 mg/L)下,SBR内发生了高粘性膨胀。 相似文献