全文获取类型
收费全文 | 498篇 |
免费 | 93篇 |
国内免费 | 71篇 |
专业分类
测绘学 | 26篇 |
大气科学 | 38篇 |
地球物理 | 167篇 |
地质学 | 288篇 |
海洋学 | 23篇 |
天文学 | 20篇 |
综合类 | 61篇 |
自然地理 | 39篇 |
出版年
2023年 | 10篇 |
2022年 | 22篇 |
2021年 | 30篇 |
2020年 | 18篇 |
2019年 | 19篇 |
2018年 | 26篇 |
2017年 | 22篇 |
2016年 | 32篇 |
2015年 | 24篇 |
2014年 | 29篇 |
2013年 | 26篇 |
2012年 | 35篇 |
2011年 | 30篇 |
2010年 | 18篇 |
2009年 | 17篇 |
2008年 | 25篇 |
2007年 | 23篇 |
2006年 | 17篇 |
2005年 | 8篇 |
2004年 | 14篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 34篇 |
1998年 | 21篇 |
1997年 | 28篇 |
1996年 | 15篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1958年 | 3篇 |
排序方式: 共有662条查询结果,搜索用时 343 毫秒
181.
利用高频GPS数据长基线双差精密定位技术,获取2011年3月日本Mw9.0强震近场和远场GPS连续参考站的瞬时动态形变。分析表明:距震源较近的IGS站(USUD)的同震动态形变水平方向幅度超过60 cm,震后水平形变达到30 cm;位于远场的GPS连续参考站(JLYJ)的动态形变,清晰地给出了地震面波引起的地表形变波形。对JLYJ站的谱分析表明,地震面波引起的动态形变周期为10~17 s,并出现了两次峰值,东西向和垂向上的动态位移量远大于北南向,说明JLYJ站的形变主要由Rayleigh波及其谐波所主导,Rayleigh波的传播速度为3.5 km/s,波长约50 km。 相似文献
182.
Meng Zhiyong Zhang Fuqing Luo Dehai Tan Zhemin Fang Juan Sun Jianhua Shen Xueshun Zhang Yunji Wang Shuguang Han Wei Zhao Kun Zhu Lei Hu Yongyun Xue Huiwen Ma Yaping Zhang Lijuan Nie Ji Zhou Ruilin Li Sa Liu Hongjun Zhu Yuning 《中国科学:地球科学(英文版)》2019,62(12):1946-1991
Synoptic meteorology is a branch of meteorology that uses synoptic weather observations and charts for the diagnosis,study,and forecasting of weather.Weather refers to the specific state of the atmosphere near the Earth's surface during a short period of time.The spatial distribution of meteorological elements in the atmosphere can be represented by a variety of transient weather phenomena,which are caused by weather systems of different spatial and temporal scales.Weather is closely related to people's life,and its development and evolution have always been the focus of atmospheric scientific research and operation.The development of synoptic meteorology is closely related to the development of observation systems,dynamical theories and numerical models.In China,observation networks have been built since the early 1950 s.Up to now,a comprehensive meteorological observation systembased on ground,air and space has been established.In particular,the development of a new generation of dense radar networks,the development of the Fengyun satellite series and the implementation of a series of large field experiments have brought our understanding of weather from large-scale environment to thermal dynamics,cloud microphysical structure and evolution characteristics of meso and micro-scale weather systems.The development of observation has also promoted the development of theory,numerical model and simulation.In the early days,China mainly used foreign numerical models.Lately,China has developed numerical model systems with independent intellectual property rights.Based on the results of high-resolution numerical simulations,in-depth understanding of the initiation and evolution mechanism and predictability of weather at different scales has been obtained.Synoptic meteorology has gradually changed from an initially independent development to a multidisciplinary approach,and the interaction between weather and the change of climate and environment has become a hot and frontier topic in atmospheric science.This paper reviews the important scientific and technological achievements made in China over the past 70 years in the fields of synoptic meteorology based on the literatures in China and abroad,from six aspects respectively including atmospheric dynamics,synoptic-scale weather,typhoon and tropical weather,severe convective weather,numerical weather prediction and data assimilation,weather and climate,atmospheric physics and atmospheric environment. 相似文献
183.
Liu Jianming Wang Qiong Nie Xiaohong Gao Ge Zhang Linlin Zhang Zhiguang Xiang Yang 《中国地震研究》2017,31(3):381-394
This paper introduces the basic parameters, focal mechanism solutions and earthquake sequence characteristics of the Kalpin MS5.3 earthquake sequence of December 1, 2013, and analyzed seismic activity before the earthquake, the adjacent tectonic features and the precursory anomaly at fixed points within a range of 200km. Research indicates:(1) The earthquake occurred on Kalpin fault, the source rupture type is thrust faulting with sinistral strike-slip component. (2) The earthquake sequence is mainshock-aftershock type, with the aftershock distribution attenuating quickly and trending NE. (3) Abnormal seismic activity before the earthquake was characterized by seismically nesting quiescence of MS2.0-4.0 earthquakes, seismic quiescence of MS4.0 earthquakes and seismic belts of MS3.0 earthquakes in the Kalpin block, abnormal enhancement zone of moderate earthquakes on Puchang fault and seismological parameters. (4) Anomalies of precursory observation data at fixed stations are mainly characterized by mutation. Apart from the borehole tiltmeter in Halajun, the spatial distribution of other abnormal precursors showed a phenomenon of migration from the near field to far field and from the epicenter to the peripheries. 相似文献
184.
Yang Jiang-he Fan Jun-hui Zhang Yue-lian Yang Ru-shu Tuo Man-xian Nie Jian-jun 《Chinese Astronomy and Astrophysics》2019,43(1):23-33
The X-ray emissions of blazars are located at the end of synchrotron radiation and the beginning of inverse Compton radiation. Therefore, the origin of the X-ray emissions is rather complex. The spectral energy distributions (SEDs) of blazars from radio to X-ray bands can be fitted approximatively by a parabolic function. If we consider approximately the fitting curves as the physical spectra of blazars to analyze the X-ray emissions of Fermi blazars, the results show that: (1) The X-ray emissions of blazars contain two components, i.e. the synchrotron radiation and inverse Compton radiation, which can be simply separated by these fitting curves; (2) the higher the synchrotron peak frequency of the source, the greater the synchrotron radiation component, and the less the inverse Compton radiation component; (3) at 1 keV of the X-ray waveband, the synchrotron radiation component accounts for 17%, 27%, and 73% of the total X-ray emission, for FSRQs (Flat Spectrum Radio Quasars), LBLs (Low synchrotron peak frequency BL Lac objects), and HBLs (High synchrotron peak frequency BL Lac objects), respectively; (4) there is a strong positive correlation between the synchrotron peak frequency and the synchrotron radiation flux density at 1 keV, while no correlation exists between the synchrotron peak frequency and the inverse Compton radiation flux density; (5) the radiation mechanism of LBLs may be similar to that of FSRQs in the X-ray waveband. 相似文献
185.
Nie RuSong Li YaFeng Leng WuMing Mei HuiHao Dong JunLi Chen XiXi 《Acta Geotechnica》2020,15(11):3041-3054
Acta Geotechnica - Since there is an interval time between two trains traveling in the same direction on an automatically blocked line, the dynamic loading on the railway subgrade is composed of... 相似文献
186.
Based on the Beijing Climate Center's land surface model BCC_AVIM(Beijing Climate Center Atmosphere-Vegetation Interaction Model), the ensemble Kalman filter(En KF) algorithm has been used to perform an assimilation experiment on the Moderate Resolution Imaging Spectroradiometer(MODIS) land surface temperature(LST) product to study the influence of satellite LST data frequencies on surface temperature data assimilations. The assimilation results have been independently tested and evaluated by Global Land Data Assimilation System(GLDAS) LST products. The results show that the assimilation scheme can effectively reduce the BCC_AVIM model simulation bias and the assimilation results reflect more reasonable spatial and temporal distributions. Diurnal variation information in the observation data has a significant effect on the assimilation results. Assimilating LST data that contain diurnal variation information can further improve the accuracy of the assimilation analysis. Overall, when assimilation is performed using observation data at 6-hour intervals, a relatively good assimilation result can be obtained, indicated by smaller bias(2.2 K) and root-mean-square-error(RMSE)(3.7 K) and correlation coefficients larger than 0.60. Conversely, the assimilation using 24-hour data generally showed larger bias(2.2 K) and RMSE(4 K). Further analysis showed that the sensitivity of assimilation effect to diurnal variations in LST varies with time and space. The assimilation using observations with a time interval of 3 hours has the smallest bias in Oceania and Africa(both1 K); the use of 24-hour interval observation data for assimilation produces the smallest bias(2.2 K) in March, April and July. 相似文献
187.
188.
测定了宁夏哈巴湖国家级自然保护区2013、2018年沙柳(Salix psammophila)群落、油蒿(Artemisia ordosica)群落、锦鸡儿(Caragana microphylla + C. korshinskii)群落和长芒草(Stipa bungeana)群落142个样点的土壤有机质、全氮和全磷含量,分析了土层20 cm处5年间土壤养分的变化。结果表明:从2013年到2018年,整个保护区土壤有机质显著增加52.46%,土壤全氮显著增加154.14%,土壤全磷增加21.75%;油蒿群落57个样点土壤有机质、全氮和全磷含量的增加量高于整个自然保护区,土壤有机质显著增加57.64%,土壤全氮显著增加323.50%,土壤全磷显著增加33.58%。5年来宁夏哈巴湖国家级自然保护区土地沙漠化得到了逆转,同时土壤养分的变化也开始影响植物群落的波动。 相似文献
189.
1∶25万、1∶100万基础数据是江苏省地理空间信息基础框架的重要组成部分,本文根据江苏省地理空间信息基础框架的要求,结合全省现有的基础地理数据库建设的现状,叙述了对全省范围内的17幅1∶25万DLG、DOM,4幅1∶100万DLG数据如何进行修测、更新和入库,并建立相应的元数据库的过程和方法。 相似文献
190.