全文获取类型
收费全文 | 1450篇 |
免费 | 259篇 |
国内免费 | 378篇 |
专业分类
测绘学 | 58篇 |
大气科学 | 315篇 |
地球物理 | 342篇 |
地质学 | 760篇 |
海洋学 | 243篇 |
天文学 | 70篇 |
综合类 | 157篇 |
自然地理 | 142篇 |
出版年
2024年 | 4篇 |
2023年 | 18篇 |
2022年 | 54篇 |
2021年 | 75篇 |
2020年 | 72篇 |
2019年 | 58篇 |
2018年 | 56篇 |
2017年 | 66篇 |
2016年 | 79篇 |
2015年 | 59篇 |
2014年 | 85篇 |
2013年 | 74篇 |
2012年 | 63篇 |
2011年 | 81篇 |
2010年 | 75篇 |
2009年 | 85篇 |
2008年 | 73篇 |
2007年 | 60篇 |
2006年 | 48篇 |
2005年 | 51篇 |
2004年 | 48篇 |
2003年 | 47篇 |
2002年 | 56篇 |
2001年 | 55篇 |
2000年 | 53篇 |
1999年 | 81篇 |
1998年 | 63篇 |
1997年 | 67篇 |
1996年 | 58篇 |
1995年 | 46篇 |
1994年 | 49篇 |
1993年 | 34篇 |
1992年 | 54篇 |
1991年 | 26篇 |
1990年 | 19篇 |
1989年 | 22篇 |
1988年 | 22篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2087条查询结果,搜索用时 312 毫秒
81.
82.
83.
84.
格尔木井水温异常特征及其与地震关系分析 总被引:1,自引:1,他引:1
简要介绍了格尔木井水温动态观测的环境与条件,在研究正常动态特征和影响因素的基础上,对水温异常的映震关系进行了分析,并成功地进行了一次短临地震趋势预测。探讨了水温异常的形成原因。 相似文献
85.
The effects of land use on runoff and soil nutrient losses in a gully catchment of the hilly areas: implications for erosion control 总被引:1,自引:0,他引:1
WANG Jun FU Bojie QIU Yang CHEN Liding CHEN Chen HU Baodong 《地理学报(英文版)》2005,15(4):396-404
1 Introduction Soiland waterlossisoneofthe worldwide environm entalissuesthreatening sustainable land use in semiarid areas.However,soiland water loss is highly variable in space and time,and its variability resultsfrom m any factorsoperating ata wide ran… 相似文献
86.
Intrusion and its implication for subsidence: A case from the Baiyun Sag, on the northern margin of the South China Sea 总被引:12,自引:0,他引:12
We develop a series of simple numerical models to explain the anomalous subsidence and deposition phenomena on the northern continental margin of the South China Sea, in particular in the Baiyun Sag. The results suggest that a short-period high rate deposition of around 17 Ma is related to a rapid subsidence event, which may be due to episodic emplacement of a dense intrusion. Necking and gravity models indicate that in the basement of the Baiyun Sag, there is a dense zone that is 100–200 kg/m3 more dense than the surrounding country rock. Considering its high magnetic intensity and regional igneous activity, the dense zone is thought to be related to a phase of basalt intrusion that may have taken place around 17 Ma. Thermal and subsidence models indicate that a hot denser intrusion can cause significant subsidence immediately after the intrusion. The subsidence rate then slows down with cooling, thus becoming consistent with the observed subsidence curves at around 17 Ma. The results also indicate that the lithospheric strength under the Baiyun Sag is negligible, and that the high-velocity layer in the lowermost crust may be not an original part of the pre-rift crust. Instead, it is thought to be underplated intrusion emplaced at around 30 Ma when the continental margin broke up. 相似文献
87.
88.
Soil moisture is essential for vegetation restoration in arid and semi-arid regions. Ascertaining the vertical distribution and transportation of soil moisture under different vegetation types has a profound effect on the ecological construction. In this study, the soil moisture at a depth of 500 cm for four typical vegetation types, including Robinia pseudoacacia, Caragana korshinskii, Stipa bungeana, and corn, were investigated and compared in the Zhifanggou watershed of the Loess plateau. Additionally, hydrogen and oxygen stable isotopes were detected to identify the transport mechanism of soil moisture. The results showed vertical distribution and transportation of soil moisture were different under different vegetation types. Depth-averaged soil moisture under S. bungeana and corn generally increased along the profile, while C. korshinskii and R. pseudoacacia showed weakly increasing and relatively stable after an obvious decreasing trend (0–40 cm). The soil moisture under R. pseudoacacia was lower than that under other vegetation types, especially in deep layer. However, the effect of R. pseudoacacia on soil moisture in the topsoil (< 30 cm) could be positive. For R. pseudoacacia (160–500 cm), C. korshinskii (0–500 cm), and S. bungeana (0–100 cm), the soil moisture declined with increased in vegetation age. Planting arbor species such as R. pseudoacacia intensified the decline of soil moisture on the Loess Plateau. The capacity of evaporation fractionation of soil moisture followed the sequence: corn > S. bungeana > R. pseudoacacia > C. korshinskii. The δ18O values in soil water fluctuated across the profile. The δ18O values changed sharply in upper layer and generally remained stable in deep layer. However, in middle layer, the vertical distribution characteristics of the δ18O values were different under different vegetation types. We estimated that piston flow was the main mode of precipitation infiltration, and the occurrence of preferential flow was related to vegetation types. These results were helpful to improve the understanding of the response of deep soil moisture to vegetation restoration and inform practices for sustainable water management. 相似文献
89.
为建立高时空分辨率的福建省复杂地形下气温栅格数据集,利用福建省及其周边33个常规气象站观测资料,基于数字高程模型(DEM)数据,综合考虑海拔、太阳总辐射、地表长波有效辐射对旬平均气温的影响,模拟了福建省复杂地形下旬均温的空间分布。结果表明:1)常规站验证结果显示:各旬气温绝对误差平均值(MAE)最小为0.46℃,最大为2.3℃,全年平均为0.87℃;加密站验证结果显示,MAE最大为2.3℃,最小0.5℃,全年平均为0.96℃。2)模拟结果能反映旬均温的宏观分布规律与局地细节特征。宏观范围内,旬均温受纬度影响较大,由北至南气温逐渐升高,沿海地区旬均温整体高于内陆,山区旬均温明显较低;局地范围内,各坡向上气温差异显著,海拔越高、坡度越大,差异越明显;地形因子对旬平均温的影响具有季节差异,具体表现为冬季时地形因子对旬均温的影响最大,秋季次之,春夏季节中地形因子对旬均温的影响最弱。 相似文献
90.
海流的拉格朗日运动对于研究物质输送有着重要意义,拉格朗日拟序结构(LCSs)作为研究海流结构的新型方法,相比于传统欧拉方法更为客观。本文提出了一种新的计算LCSs束的方法,基于25年的平均速度场,利用变分方法计算得到黑潮区域的气候态LCSs,并通过简化合并的方法得到了气候态LCSs束,该LCSs束能够突出地显示出海流特性和运输模式,其代表的平均拉格朗日环流有很强的约束作用,且具有鲁棒性。最终我们获得了气候态下12个月份的流场结构图,揭示了月周期性拉格朗日环流规律。本文还利用虚拟粒子输运、多年浮标轨迹以及气候态温盐异常3种方法进行了验证,与拉格朗日运输模式相吻合,证明了海流拉格朗日拟序结构的准确性和可靠性。 相似文献