全文获取类型
收费全文 | 53篇 |
免费 | 10篇 |
国内免费 | 8篇 |
专业分类
大气科学 | 21篇 |
地球物理 | 7篇 |
地质学 | 29篇 |
海洋学 | 4篇 |
天文学 | 1篇 |
综合类 | 1篇 |
自然地理 | 8篇 |
出版年
2023年 | 1篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 2篇 |
2012年 | 2篇 |
2011年 | 5篇 |
2010年 | 1篇 |
2008年 | 4篇 |
2007年 | 3篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1990年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
排序方式: 共有71条查询结果,搜索用时 15 毫秒
51.
52.
The nutritional quality of grasslands is closely related to recruitment of young and population dynamics of livestock and wild herbivores. However, the response of nutritional quality to climate warming has not been fully understood in the alpine meadow on the Tibetan Plateau, especially in the Northern Tibet. Here, we investigated the effect of experimental warming ( beginning in 2008) on nutritional quality in three alpine meadows (site A: 4313 m, B: 4513 m and C: 4693 m) in the Northern Tibet. Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), crude ash (Ash), ether extract (EE) and water-soluble carbohydrate (WSC) were examined in 2018-2019. Experimental warming only increased the content of CP by 27.25%, ADF by 89.93% and NDF by 41.20%, but it decreased the content of Ash by 57.76% in 2019 at site B. The contents of CP and WSC both increased with soil moisture (SM). The content of CP decreased with vapor pressure deficit (VPD). The combined effect of SM and VPD was greater than air temperature (Ta) in controlling the variations of the CP content, ADF content and nutritional quality. Compared to Ta, VPD explained more of the variation in NDF and Ash content. All of these findings suggest that warming effects on nutritional quality may vary with site and year, and water availability may have a stronger effect on the nutritional quality than temperature in the alpine meadow of the Northern Tibet. 相似文献
53.
54.
To investigate chemical profiles and formation mechanisms of aerosol particles in winter haze events,comprehensive measurements including hourly concentrations of PM2.5 and water-soluble inorganic ions and related gasphase precursors were conducted via an online monitoring system from January to March of 2016 in Shenzhen, a coastal mega-city in south China. In this study, high concentrations of PM2.5, NO2 and lower levels of O3 were observed during haze periods in comparison with clear days(Visibility15 km). The major secondary ionic species were NH+4、NO-3 and SO2-4, which varied significantly on haze and clear days. The ratio of NO-3/SO2-4 in haze days was greater than that on clear days and tended to be larger when air pollution became more serious. At the same time, compared with previous studies, it has been found that the ratio has been increasing gradually in Shenzhen, indicating that the motor vehicle exhaust emissions have a more and more important impact on air quality in Shenzhen. Sulfur oxidation rate(SOR) and nitrogen oxidation rate(NOR) was higher during the haze period than that in clean days, indicating efficient gas to particle conversion. Further analysis shows that high concentrations of sulfate might be explained by aqueous oxidation,but gas-phase reactions might dominate nitrate formation. This study also highlights that wintertime nitrate formation can be an important contributor to aerosol particles, especially during haze periods. 相似文献
55.
天然气组分的溶解特征及其意义 总被引:24,自引:0,他引:24
通过模拟实验方法研究了天然气组分在地层水中的溶解特征。发现在多组分体系中,重烃气的溶解度随矿化度的增大出现先增后减现象;环烷酸类有机物对长链烃气组有明显的增溶作用,分压及其他条件相同时,天然气组分的溶解能力顺序为:CO2〉CH4〉N2〉C2H6〉C3H8〉n-C4H10〉i-C4H10〉n-C5H12〉i-C5H12。 相似文献
56.
内蒙古陶海营子地区上二叠统林西组泥岩热演化程度研究 总被引:1,自引:0,他引:1
近年来松辽盆地外围油气勘探-基础地质调查表明,大兴安岭地区上二叠统林西组发育有厚层的暗色泥岩,为重要的潜在生烃层系之一.林西组在陶海营子地区出露广泛.本次研究采集了该区露头和钻井中的暗色泥岩样品.通过镜质体反射率(Ro)、伊利石结晶度(KI指数法),对本区林西组暗色泥岩的有机质热演化程度进行了详细的研究,认为本地区林西组烃源岩演化处于高-过成熟演化阶段,未进入变质阶段,具有较好的页岩气勘探前景. 相似文献
57.
旱—半干旱高寒地区土壤盐渍化,对区域农牧业发展及地质环境造成较大的影响。本文在西藏扎西康矿集区环境地质调查的基础上,通过对宿麦朗沟盐渍化3处土壤剖面系统采样分析,查明土壤盐分的空间分布及盐渍化成因。结果表明:相同层位土壤电导率与水溶性盐分总量之间呈正相关关系,0~80cm之间,土壤中盐分离子含量变化较大;80cm之下,土壤盐分含量趋于稳定;因子分析进一步揭示,研究区土壤盐分主要由氯离子、钠离子组成,两者之间相关性较强(R2=0.9592);维美组地层以高硅、高钠为特征,三角洲及河流相的沉积环境及地下水活动等共同造成该区域土壤盐渍化。在此基础上,针对性地提出了降低地下水位、定期人工喷淋洗盐及施入有机肥料等方法是干旱区土壤盐渍化防治的有利措施。 相似文献
58.
华南气溶胶研究的回顾与展望 总被引:17,自引:7,他引:17
大气气溶胶的气候效应研究和环境效应研究都是当今国际科技界的热门研究话题,而研究大气气溶胶的气候效应和环境效应都必须充分细致地了解气溶胶的粒子谱分布、化学组成和辐射(光学)特性,其中大气气溶胶的辐射(光学)性质的直接观测研究是目前甚为紧迫的研究内容,其结果能直接为气溶胶强迫对气候变化的估计和预测的模式研究及其环境效应的研究提供必须的参数. 相似文献
59.
综述了电动力学技术的原理及其在受污染土壤和地下水修复方面的应用.电动力学技术利用电渗析、电迁移和电泳使土壤孔隙中的水和荷电离子或粒子发生迁移运动.大量研究表明,电动力学技术能够高效地去除土壤和地下水中的重金属离子.最新研究表明电动力学技术也能够直接去除有机污染物,其与生物修复优化组合有可能成为高效"绿色"修复技术.这种技术具有安装方便、操作简单和成本低廉的特点,而且不影响生态环境,是非常有发展前景的一种环境修复技术. 相似文献
60.
A gas chromatographic study has revealed the presence in volcanic gases of a variety of volatile organic compounds. Of particular interest is the detection of such halocarbons as trichlorofluoromethane (F-11), dichlorodifluoromethane (F-12), dichlorofluoromethane (F-21), CCl4 and CHCl3. The concentrations of these compounds attaining 160 ppb in undilute solfataric gases were determined for the first time. The data obtained confirm the existence of a natural source of halocarbons that have a long lifetime in the troposphere and that play an important role in the greenhouse effect and in the catalytic cycle of destruction of stratospheric ozone. 相似文献