全文获取类型
收费全文 | 3121篇 |
免费 | 634篇 |
国内免费 | 809篇 |
专业分类
测绘学 | 239篇 |
大气科学 | 694篇 |
地球物理 | 848篇 |
地质学 | 1572篇 |
海洋学 | 405篇 |
天文学 | 109篇 |
综合类 | 291篇 |
自然地理 | 406篇 |
出版年
2024年 | 27篇 |
2023年 | 96篇 |
2022年 | 204篇 |
2021年 | 222篇 |
2020年 | 192篇 |
2019年 | 199篇 |
2018年 | 242篇 |
2017年 | 192篇 |
2016年 | 230篇 |
2015年 | 167篇 |
2014年 | 221篇 |
2013年 | 193篇 |
2012年 | 194篇 |
2011年 | 159篇 |
2010年 | 171篇 |
2009年 | 147篇 |
2008年 | 143篇 |
2007年 | 156篇 |
2006年 | 91篇 |
2005年 | 92篇 |
2004年 | 89篇 |
2003年 | 74篇 |
2002年 | 91篇 |
2001年 | 96篇 |
2000年 | 95篇 |
1999年 | 133篇 |
1998年 | 74篇 |
1997年 | 94篇 |
1996年 | 78篇 |
1995年 | 73篇 |
1994年 | 55篇 |
1993年 | 63篇 |
1992年 | 39篇 |
1991年 | 35篇 |
1990年 | 25篇 |
1989年 | 19篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 18篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1968年 | 1篇 |
1958年 | 1篇 |
1951年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有4564条查询结果,搜索用时 5 毫秒
931.
At about 8:30 p.m. on 27 August 2014, a catastrophic rock avalanche suddenly occurred in Fuquan, Yunnan, southwestern China. This landslide and related impulse water waves destroyed two villages and killed 23 persons. The impulse waves occurred after initiation of the landslide, caused by the main part of the slide mass rapidly plunging into a water-filled quarry below the source area. The wave, comprising muddy water and rock debris, impacted the opposite slope of the quarry on the western side of the runout path and washed away three homes in Xinwan village. Part of the displaced material traveled a horizontal distance of about 40 m from its source and destroyed the village of Xiaoba. To provide information for potential landslide hazard zonation in this area, a combined landslide–wave simulation was undertaken. A dynamic landslide analysis (DAN-W) model is used to simulate the landslide propagation before entering the quarry, while Fluent (Ansys Inc., USA) is used to simulate the impulse wave generation and propagation. Output data from the DAN-W simulation are used as input parameters for wave modeling, and there is good agreement between the observed and simulated results of the landslide propagation. Notably, the locations affected by recordable waves according to the simulation correspond to those recorded by field investigation. 相似文献
932.
鱼田堡煤矿水文地质特征及深部突水模式分析 总被引:5,自引:1,他引:5
通过对鱼田堡煤矿各生产水平、开采区域、开采煤层涌水观测资料,以及水质化验、连通试验等资料的分析与研究,查明了该矿深部煤层开采的突水水源及突水通道——浅部与采空区融为一体的“地下水库”及深部K3(4#煤层)开采时在煤层顶板以上发育的采动离层裂隙带,为防治矿井深部突水提供了较为切合实际的水文地质依据。 相似文献
933.
934.
935.
为探究缢蛏糖原磷酸化酶基因(Sc-GPH)与糖原含量的关系,本研究克隆获得Sc-GPH cDNA全长,检测其在不同组织、不同月份的表达模式,并在Sc-GPH基因编码区筛选与糖原含量关联的SNP位点.结果表明,Sc-GPH cDNA全长为3963 bp,开放阅读框为2541 bp,编码846个氨基酸;氨基酸序列多重比对和系统发育树显示,缢蛏与欧洲大扇贝、虾夷扇贝、长牡蛎等贝类亲缘关系较近,而与哺乳类、甲壳类、昆虫类亲缘关系较远.实时荧光定量PCR结果显示,Sc-GPH在8个组织中均有表达,其中在外套膜和足中表达量最高(p<0.01),推测与其糖原存储能力有关;不同月份的缢蛏外套膜和足中,Sc-GPH在8月表达量最高,而此时糖原含量较低,说明Sc-GPH的表达可能受缢蛏生殖周期的影响.以缢蛏"甬乐1号"群体为实验材料,在Sc-GPH基因编码区筛选到4个与糖原含量相关SNP位点,其中c.930T>C位点在台州野生群体中得到进一步验证,该位点为高糖原缢蛏分子标记辅助选育提供了候选标记. 相似文献
936.
采用规则网格有限差分方法对二维平面弹性波动方程进行差分离散,得到相应的弹性波动方程的有限差分方程,再将弹性波动方程的差分格式与吸收边界、自由边界的离散形式结合形成弹性波动方程有限差分方程解决问题的主体,将其应用于含方形凹陷半无限非均匀介质的模型中进行数值模拟,得到此离散化模型中不同时刻不同节点的位移值。针对具体算例,运用上述方法结合科学计算软件MATLAB和结果后处理软件DIFEM ISOLINE PLOTER得到不同时刻的水平方向位移等值线图与接收器测量点处的合成位移记录,讨论非均匀介质、吸收边界、方形凹陷等对波动特性的影响。 相似文献
937.
基于北斗卫星短信通信方式的无人值守自动气象站网 总被引:1,自引:0,他引:1
以新疆气象局基于北斗卫星短信方式布设的无人值守自动气象站网为例,介绍北斗卫星短信通信方式在无人值守自动气象站数据传输中的实际应用,重点介绍无人值守自动气象站数据传输的特殊需求、通信传输网的架构模式、信息处理流程、控制方式等方面的技术内容,并针对新疆气象局的实际应用情况,对无人自动站采用北斗卫星短信通信方式传输数据的优势与不足进行分析,提出了北斗卫星短信方式在无人自动气象站数据传输方面具有较广的应用空间。 相似文献
938.
Modeling the risk of nitrate leaching and nitrate runoff loss from intensive farmland in the Baiyangdian Basin of the North China Plain 总被引:2,自引:0,他引:2
The water movement and soil nitrogen cycle of the Baiyangdian Basin were simulated, and the risk of nitrate leaching and nitrate runoff loss from intensive farmland was assessed by using the distributed hydrological soil and water assessment tool (SWAT) in this study. The model assessment showed that SWAT was able to simulate water and nitrate movement in the region with satisfactory results. The modeling analysis indicated that fertilizer application was the overriding source of soil nitrogen and might result in a large amount of nitrate accumulation in soils; this nitrate might be lost by leaching or runoff driven by water movement. In 2009, nitrate nitrogen leaching represented 19.5 % of the total amount of nitrogen fertilizer application, while nitrate nitrogen runoff represented 1.7 % only. Thus, it showed that the nitrate leaching was the main approach of soil nitrogen movement in farmland because of strong percolation. It also showed a significant variation of nitrate leaching from different soil depths, with the largest amount leached from surface soil layers and the smallest amount leached from lower soil layers. Therefore, it could be further revealed that the nitrate concentration was very low at soil layers lower than the root zone of crops (1.2 m). Validated by groundwater observations, groundwater pollution by nitrate derived from fertilizers was not serious because of the deep groundwater level in the study plain. However, the risk of groundwater pollution would increase significantly if precipitation increased. 相似文献
939.
Expeditions to Muztagata (in the eastern Pamirs) during the summer seasons of 2002 and 2003 collected precipitation samples
and measured their oxygen isotopes. The δ
18O in precipitation displays a wide range, varying from −17.40‰ to +1.33‰ in June-September 2002 and from −22.31‰ to +4.59‰
in May-August 2003. The δ
18O in precipitation correlates with the initial temperature of precipitation during the observing periods. The positive correlation
between δ
18O and temperature suggests that δ
18O can be used as an indicator of temperature in this region. The δ
18O values in fresh-snow samples collected from two snow events at different elevations on the Muztagata Glacier show a strong
“altitude effect”, with a ratio of nearly −0.40% per 100 m from 5500 m to 7450 m. 相似文献
940.
Qian Ye Bo-Yang Wang Qiang Yao Jin-Qing Wang Qing-Hui Liu Zhi-Qiang Shen 《天文和天体物理学研究(英文版)》2021,(10):175-186
This paper presents a new method to obtain the deformation distribution on the main reflector of an antenna only by measuring the electric intensity on a spheri... 相似文献