全文获取类型
收费全文 | 2579篇 |
免费 | 288篇 |
国内免费 | 1297篇 |
专业分类
安全科学 | 137篇 |
废物处理 | 319篇 |
环保管理 | 164篇 |
综合类 | 2158篇 |
基础理论 | 633篇 |
污染及防治 | 545篇 |
评价与监测 | 176篇 |
社会与环境 | 21篇 |
灾害及防治 | 11篇 |
出版年
2024年 | 5篇 |
2023年 | 35篇 |
2022年 | 60篇 |
2021年 | 83篇 |
2020年 | 91篇 |
2019年 | 83篇 |
2018年 | 97篇 |
2017年 | 117篇 |
2016年 | 143篇 |
2015年 | 171篇 |
2014年 | 180篇 |
2013年 | 297篇 |
2012年 | 252篇 |
2011年 | 238篇 |
2010年 | 195篇 |
2009年 | 190篇 |
2008年 | 167篇 |
2007年 | 227篇 |
2006年 | 212篇 |
2005年 | 163篇 |
2004年 | 135篇 |
2003年 | 131篇 |
2002年 | 122篇 |
2001年 | 93篇 |
2000年 | 89篇 |
1999年 | 94篇 |
1998年 | 94篇 |
1997年 | 71篇 |
1996年 | 66篇 |
1995年 | 53篇 |
1994年 | 35篇 |
1993年 | 25篇 |
1992年 | 37篇 |
1991年 | 40篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有4164条查询结果,搜索用时 19 毫秒
651.
652.
内蒙高腐殖酸地下水中碘的分布特征与IDD病的关系 总被引:3,自引:1,他引:2
为探讨碘在高腐植酸地下水中的分布特征 ,研究内蒙古河套平原地区 51份水样 .分析结果显示 ,水质偏碱 (平均值 pH=7.91 ) ,水中腐植酸和 COD含量均高 ,地下水类型属于 HCO3-Na和 HCO3-Cl- Na型 .在这种高还原型盐水环境中水碘平均浓度达到 430 μg/L,超过了水碘安全浓度范围的上限 ( 5~ 200μg/L) .相关分析结果显示 ,水碘浓度与其它因素的相关顺序是 :COD>荧光强度 >电导率 >HCO-3>Cl->Na+>pH>As>井深 .当地地下水中碘的分布呈现出碘浓度随腐植酸含量和盐渍化程度增加而增加的趋势 .由于这些因素的综合作用 ,当地没有发生高碘型碘缺乏病 ( IDD)的大面积流行 . 相似文献
653.
Summary. Tannins are plant defense compounds that exhibit antibiotic (e.g. toxic) and antixenotic (e.g. repellent) effects against
an array of plant pests. They are broadly divided into two major groups, hydrolysable tannins (gallotannins and ellagitannins)
and proanthocyanidins, each with an undetermined number of compounds. We investigated constitutive levels of hydrolysable
tannins and proanthocyanidins in the leaves and stems of American (Castanea dentata Marshall) (Fagales: Fagaceae) and Chinese (C. mollissima Blume) chestnut. American chestnut contained more proanthocyanidins in leaves and stems than Chinese chestnut, but Chinese
chestnut contained more foliar hydrolysable tannins. Regardless of these differences, gypsy moth (Lymantria dispar L, Lepidoptera: Lymantriidae) performance did not differ when fed American and Chinese chestnuts. We also investigated the
effects of jasmonic acid (JA) treatment on differential tannin induction in American and Chinese chestnut leaves and stems.
JA treatment increased proanthocyanidins in American chestnut stems and hydrolysable tannins in both tissue types of American
chestnut, but did not influence tannin concentrations in Chinese chestnut leaves or stems. HPLC-ESI-MS analysis of pooled
samples suggested that hydrolysable tannins in each tissue were qualitatively comprised primarily of ellagitannins, and JA
generally increased the number of hydrolysable tannins that could be detected by ESI-MS. Third, we investigated the performance
of gypsy moths on JA treated and untreated American and Chinese chestnut. Caterpillar relative growth was not influenced by
JA treatment on Chinese chestnut, but decreased in response to JA application on American chestnut. Our results indicate that
JA-dependent defenses differ between these chestnut species. This study improves our understanding of ecologically important
differences in tannin induction and herbivore susceptibility in Castanea, and has important implications in efforts for American chestnut restoration and commercial chestnut production. 相似文献
654.
水杨酸对梨叶感染轮纹菌后脂肪酸、叶绿素荧光参数和叶绿体超微结构的影响 总被引:1,自引:0,他引:1
用0.3 mmol L-1水杨酸预先处理梨叶片,3 d后接种轮纹病菌(Physalospora Piricola Nose),接种3 d后开始测定各种指标,随后每隔3 d测定1次,共5次.结果表明,经SA处理的梨叶片,感染轮纹病菌后不饱和脂肪酸含量(UFA)、不饱和脂肪酸指数(IUFA)、叶绿素含量、原初光能转换效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)、光合电子传递量子效率(ΦPSⅡ)和光化学猝灭系数(qP)比未经SA处理的相应提高;非光化学猝灭系数(qN)比未经SA处理的相应下降.电镜观察表明,部分叶绿体膨大,变形;基粒片层弯曲、散开;淀粉粒数量减少;经SA处理后,症状减轻.图3表1参20 相似文献
655.
Effects of simulated acid rain on fertility of litchi 总被引:1,自引:0,他引:1
The regulatory role of calcium in fertility of pollen and pistil under simulated acid rain was investigated. The germination percentage of pollen treated with acid rain of pH 4.5 was 9.42% lower than that of control, and that of pH 3.5, pH 2.5 and pH 1.5 were 22.47%, 45.49% and 71.62%, respectively. Simultaneously, the injury character of pollen was obviously observed when flowers were treated with acid rain of pH 3.5. The difference in fruit setting rate between the female flower treated with acid rain of pH 4.0 and the control was significant at p 〈 0.05. Ca(NO3 )5 of 0.2-0.4 mmol/L could promote pollen germination under the stress of acid rain. The beneficial function was reduced when calcium concentration surpassed 0.8 mmol/L. Spraying 2 mmol/L Ca(NO3 )5 reduced the injury of acid rain to pistil and increased fruit-setting rate significantly. The physiological importance of calcium during pollen germination and pistil development was also discussed. 相似文献
656.
657.
658.
659.
660.