全文获取类型
收费全文 | 1441篇 |
免费 | 257篇 |
国内免费 | 384篇 |
专业分类
测绘学 | 51篇 |
大气科学 | 236篇 |
地球物理 | 334篇 |
地质学 | 917篇 |
海洋学 | 168篇 |
天文学 | 61篇 |
综合类 | 173篇 |
自然地理 | 142篇 |
出版年
2024年 | 8篇 |
2023年 | 30篇 |
2022年 | 65篇 |
2021年 | 59篇 |
2020年 | 49篇 |
2019年 | 89篇 |
2018年 | 86篇 |
2017年 | 66篇 |
2016年 | 75篇 |
2015年 | 63篇 |
2014年 | 69篇 |
2013年 | 71篇 |
2012年 | 70篇 |
2011年 | 98篇 |
2010年 | 81篇 |
2009年 | 85篇 |
2008年 | 71篇 |
2007年 | 73篇 |
2006年 | 62篇 |
2005年 | 53篇 |
2004年 | 42篇 |
2003年 | 34篇 |
2002年 | 42篇 |
2001年 | 41篇 |
2000年 | 58篇 |
1999年 | 86篇 |
1998年 | 62篇 |
1997年 | 68篇 |
1996年 | 51篇 |
1995年 | 60篇 |
1994年 | 46篇 |
1993年 | 47篇 |
1992年 | 17篇 |
1991年 | 22篇 |
1990年 | 21篇 |
1989年 | 11篇 |
1988年 | 16篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1965年 | 1篇 |
1958年 | 3篇 |
排序方式: 共有2082条查询结果,搜索用时 328 毫秒
911.
Soil bacterial functional diversity as influenced by cadmium,phenanthrene and degrade bacteria application 总被引:1,自引:0,他引:1
Wei Jiang Jijun Wang Jianshe Tang Feng Hou Yitong Lu 《Environmental Earth Sciences》2010,59(8):1717-1722
There are increasing concerns over compound pollution in northeast of China and its bioremediation. Cd, Phe, degradation bacteria
W.J and their combination on soil microbial community function were assessed with the BIOLOG method. The microbial community
was extracted from the soil with different treatments. Average color development, richness, Shannon–Weaver index, and principal
component analysis on OD standardized data were performed. The results showed that soil microbial metabolic diversity in CK
was significantly higher than that in the soils in which Cd, Phe, W.J or their combination was added. It indicated that Cd,
Phe has significantly negative effect on the sole-carbon-source metabolic ability of soil microbial communities, particularly
when both of them were present. Application of degradation bacteria incubation makes soil microbial communities same as control
except for the significant decrease in 4-hydroxy benzoic acid, l-serine, glucose-1-phosphate metabolism. It shows that the incubate application has a considerably effect in soil communities
reversion. 相似文献
912.
The multi-scale characteristics of wave significant height (Hss) in eastern China seas were revealed by multi-scale wavelet analysis. In order to understand the relation between wave and wind, the TOPEX/Poseidon measurements of Hs and wind speed were analyzed. The result showed that Hs and wind speed change in multi-scale at one-, two-month, half-, one- and two-year cycles. But in a larger time scale, the variations in Hs and wind speed are different. Hs has a five-year cycle similar to the cycle of ENSO variation, while the wind speed has no such cycle. In the time domain, the correlation between Hs and ENSO is unclear. 相似文献
913.
1 INTRODUCTION The unicellular Dunaliella salina, is one of the well studied microalgae for mass culture and is of commercial importance as a source of natural beta-carotene (Avron and Ben-Amot, 1992). D. sa- lina has desirable properties of halotolerance… 相似文献
914.
The profiles of cortisol, testosterone, ll-ketotestosterone and 17α, 20β- dihydroxy-4-pregnene-3-one in mule rainbow trout reared under constant water temperature and natural photoperiod were determined by radioimmunoassay. Gonads of male rainbow trout reached maturity when the fish were two years old. Changes in the plasma levels of both sex steroid hormones and cortisol were closely related to the GSI. Plasma levels of testosterone, 11-ketotestostemne and 17a, 2013-dihydroxy 4-pregnene-3-one showed a clear peak in the annual breeding season, when the GSI reached their maxima. Plasma cortisol levels also showed clearly seasonal changes in both two- and three-year-old fish. The results suggest that the elevated plasma levels of cortisol may not just be due to stresses during the breeding season but have certain physiological functions in the reproduction of rainbow trout. 相似文献
915.
基于逐日气象干旱指数,构建了可以反映某一时段内气象旱涝强度的标准化阶段气象旱涝强度指数 (staged meteorological drought intensity index, ISD) 和阶段气象旱涝时间分布状态的标准化阶段气象旱涝空间分布差异指数 (staged meteorological drought discrepancy index, ISDD)。以构建昆明月尺度的ISD和ISDD为例说明了阶段气象旱涝指数的构建方法,通过对不同时段降水距平百分率、ISD, ISDD和标准降水指数 (standardized precipitation index, ISP) 的对比分析,结合降水及逐日气象干旱指数 (multi-scale standardized precipitation index, IMSP) 的演变,验证了ISD和ISDD的有效性。对于任一站点的不同时间尺度,两个指数可以在日尺度到年尺度乃至更大的时间尺度上进行计算,通过Boltzmann函数来构建ISD和ISDD的方法具有很好的拓展应用性,其他气象干旱指数也可以采用该方法来构建阶段干旱指数。 相似文献
916.
利用天津近30年来的逐年电力负荷数据以及2002-2005年逐时电力负荷资料,分析了天津电力负荷的变化特征,研究了电力负荷与气象因子的关系.结果表明:近30年来,天津电力负荷的长期趋势基本受当地GDP的影响,气温等气象因子的作用不明显;在季节和日尺度上,气温的影响十分显著,7、8月气温每上升1℃,气象负荷将增加120MW左右;除气温的影响外,夏季、初秋相对湿度对电力负荷的影响非常显著,此外,4月、6月、7月和12月还得考虑风的影响;一般来说,夏季最高气温在30℃以上,平均相对湿度大于65%时,才可能出现极端电力负荷. 相似文献
917.
在对国内气象旅游资源评估方法分析研究的基础上,从气象旅游资源相关因素中,筛选出了7个指标,创建了气象旅游资源评估指标体系,提出了评估方法。计算每个评估指标的实际数值并进行标准化处理。采用专家咨询和层次分析法相结合的方法对评估指标体系中的每一级指标赋予相应的权重,最终构建出气象旅游资源评估模型。在实例研究中,以大连为例,选取葫芦岛、东港、鞍山和岫岩等4个城市为对照,结合多年的气候统计数据,分别计算5个城市的气象旅游资源评估指数,并进行横向对比分析,找出各城市气象旅游资源的优势和不足。 相似文献
918.
919.
920.