全文获取类型
收费全文 | 1595篇 |
免费 | 266篇 |
国内免费 | 385篇 |
专业分类
测绘学 | 227篇 |
大气科学 | 240篇 |
地球物理 | 361篇 |
地质学 | 931篇 |
海洋学 | 113篇 |
天文学 | 119篇 |
综合类 | 114篇 |
自然地理 | 141篇 |
出版年
2024年 | 10篇 |
2023年 | 42篇 |
2022年 | 101篇 |
2021年 | 94篇 |
2020年 | 91篇 |
2019年 | 77篇 |
2018年 | 84篇 |
2017年 | 65篇 |
2016年 | 89篇 |
2015年 | 88篇 |
2014年 | 98篇 |
2013年 | 103篇 |
2012年 | 67篇 |
2011年 | 100篇 |
2010年 | 86篇 |
2009年 | 103篇 |
2008年 | 84篇 |
2007年 | 102篇 |
2006年 | 77篇 |
2005年 | 73篇 |
2004年 | 42篇 |
2003年 | 45篇 |
2002年 | 45篇 |
2001年 | 48篇 |
2000年 | 50篇 |
1999年 | 63篇 |
1998年 | 51篇 |
1997年 | 42篇 |
1996年 | 28篇 |
1995年 | 35篇 |
1994年 | 43篇 |
1993年 | 35篇 |
1992年 | 18篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1958年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有2246条查询结果,搜索用时 11 毫秒
71.
利用UMRAO数据库22个耀变体源的偏振数据,根据Lazarian&Pogosyan理论模型分析研究了耀变体射电波段的偏振随波长的变化,得出不同类的耀变体偏振随波长变化的原因。结果表明,与Lazarian&Pogosyan理论模型吻合较好。由此得出如下结论:(1)反常去偏振耀变体源中反常法拉第旋光起主导作用,反常去偏振相对较少;(2)热辐射与同步辐射混合作用,高频波段的偏振度小于低频波段的偏振度(反常去偏振);(3)当被观测波段波长小于吸积盘热辐射对应的维恩波长时,高频波段的偏振度大于低频波段的偏振度(常规去偏振)。 相似文献
72.
Marine Geophysical Research - It is curious that the typical feature of high-velocity layer (HVL) underneath the crust for the magma-rich margin was found in the magma-poor margin of the South... 相似文献
73.
珠江口淇澳岛海岸带反硝化作用研究 总被引:3,自引:0,他引:3
采用N2通量法,在一套连续流动培养装置中测定珠江口淇澳岛海岸带的反硝化速率,探讨各种因素对淇澳岛海岸带反硝化速率的影响.结果表明,反硝化速率受NO3-的利用率影响,而不是NO3-的绝对浓度.大型红树植物对淇澳岛海岸带的反硝化速率影响最大,其次是硝酸盐利用率,而有机质含量的影响较小.由于大型红树植物的影响,样品Q0411-5的反硝化速率比同在岛内的Q0411-3高出1倍.样品Q0412-14的NO3-培养前后的浓度变化(△NO3-)是Q0412-9的4倍多,因为受硝酸盐利用率的影响,它的反硝化速率却是Q0412-9的2倍多.温度对反硝化速率的影响程度尚不能确定. 相似文献
74.
75.
Pengfei Xiong Cong Cheng Zenggui Kuang Jinfeng Ren Jinqiang Liang Hongfei Lai Zigui Chen Jiang Lu Xiaoyu Fang Tao Jiang 《海洋学报(英文版)》2023,42(2):120-133
In the late Miocene, giant ancient pockmarks, which are fairly rare globally, developed in the Qiongdongnan Basin. In this paper, to determine the sedimentary characteristics and genetic mechanism of these giant ancient pockmarks in the Yinggehai Formation of the Qiongdongnan Basin, based on high-resolution 3D seismic data and multiattribute fusion technologies, we analyzed the planar distribution and seismic facies of the ancient pockmarks and compared the characteristics of the ancient pockmar... 相似文献
76.
We carried out a series of linear stability analyses of the radial and low-degree non-radial p modes for stellar models with initial masses of . The stellar models were computed by using convective overshoot distance , 0.25 and 0.40 H P . Our numerical results show that the β Cephei instability strip forms a horn-shaped region pointing upwards near the main sequence on the Hertzsprung–Russell diagram (HRD). The lower part of the instability strip for the radial modes join the zero-age main-sequence (ZAMS) at , while the top of the instability strip extends up to . The instability strip for the non-radial modes is even wider. The overall instability strip is dominated by the radial and non-radial fundamental modes. The first overtone (the radial-order index is also pulsationally unstable. We have shown that the β Cephei stability is almost independent of the overshoot parameter d over used for the stellar models, while it depends critically on the metal abundance. With decreasing metal abundance, the instability region shrinks and eventually disappears for . 相似文献
77.
1 INTRODUCTIONThe mixing length theory (MLT) for stellar convection originally developed by Vitense(1953, 1958) has been the most popularly used local convection theory in the studies of stellarstructure and evolution. The theory was later modified and revised by many investigators,who suggested some different expressions. In fact, MLT is not a real hydrodynamic theory,rather, it is a simple "ballistic" theory which traces the motion of imaginary convective elements. In reality j stell… 相似文献
78.
Hu Xiong Wu Xiao-cheng Gong Xiao-yan Wang Xin Xu Qin-chen 《Chinese Astronomy and Astrophysics》2010,34(1):100-112
The technical system of the Sino-Russian joint satellite-to-satellite Mars ionosphere occultation is analyzed and introduced. The analogue computation of the observed values of the radio waves of the ionosphere occultation event is carried out by adopting the three-dimensional ray tracking method and the electron density profile inversion is conducted by means of the simulated occultation observational data, with the result showing that the emulation algorithm is reliable. By taking advantage of the emulation method the case computation and analysis of the inversion errors caused by the observational error of the occultation radio wave phase and the satellite orbital error are respectively carried out, and it is obtained from the result that the effect of the phase measuring error of the 5% circle on the result of the daytime ionosphere occultation exploration may be neglected, while the absolute error of the night electron density measurement is less than 4 × 108 m?3, and the main effect of the satellite orbital error on the occultation leads to the lifting or falling of the ionospheric height. The result shows that the technical system of the Sino-Russian joint Mars ionosphere occultation exploration is advanced. It can be expected that the high accuracy electron density profile is obtained and the technical system can be applied to the exploration of the lunar ionospheric environment. 相似文献
79.
80.