全文获取类型
收费全文 | 15061篇 |
免费 | 1824篇 |
国内免费 | 2126篇 |
专业分类
测绘学 | 5030篇 |
大气科学 | 2341篇 |
地球物理 | 2262篇 |
地质学 | 3605篇 |
海洋学 | 1455篇 |
天文学 | 1248篇 |
综合类 | 1462篇 |
自然地理 | 1608篇 |
出版年
2024年 | 81篇 |
2023年 | 157篇 |
2022年 | 488篇 |
2021年 | 633篇 |
2020年 | 633篇 |
2019年 | 733篇 |
2018年 | 529篇 |
2017年 | 789篇 |
2016年 | 709篇 |
2015年 | 727篇 |
2014年 | 859篇 |
2013年 | 1060篇 |
2012年 | 963篇 |
2011年 | 896篇 |
2010年 | 692篇 |
2009年 | 868篇 |
2008年 | 909篇 |
2007年 | 1061篇 |
2006年 | 978篇 |
2005年 | 793篇 |
2004年 | 781篇 |
2003年 | 585篇 |
2002年 | 507篇 |
2001年 | 427篇 |
2000年 | 355篇 |
1999年 | 322篇 |
1998年 | 259篇 |
1997年 | 185篇 |
1996年 | 173篇 |
1995年 | 161篇 |
1994年 | 145篇 |
1993年 | 131篇 |
1992年 | 78篇 |
1991年 | 71篇 |
1990年 | 44篇 |
1989年 | 44篇 |
1988年 | 35篇 |
1987年 | 27篇 |
1986年 | 25篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1977年 | 11篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1971年 | 5篇 |
1954年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 828 毫秒
381.
382.
383.
C. Ravaut S. Operto L. Improta J. Virieux A. Herrero P. Dell'Aversana 《Geophysical Journal International》2004,159(3):1032-1056
384.
The Application of ARGO Data to the Global Ocean Data Assimilation Operational System of NCC 总被引:11,自引:0,他引:11
下载免费PDF全文
![点击此处可从《Acta Meteorologica Sinica》网站下载免费的PDF全文](/ch/ext_images/free.gif)
1. Introduction It is well-known that the state of ocean plays very important role in the climate change. But there is a paucity of the ocean observation data. The data distri- bution in the space, time and different components is very inhomogeneous, even in some areas, there are no any observation data. Hence, it brings some diffcul- ties to the scientists to study many problems relevant to ocean. This situation has been being changed since ARGO (Array for Real-time Geostrophic Oceanogra-… 相似文献
385.
386.
Underground coal and copper ore exploitation in two Polish mining regions causes mining tremors and a series of other negative phenomena in the environment. Although these tremors are strictly connected with human activity, they differ considerably from other paraseismic vibrations. The moment of their occurrence is not to be foreseen likewise for earthquakes. The main problem discussed in the paper was formulated as the neural network evaluation of a relation between mining tremor energies, epicentral distances and acceleration response spectra. Back-propagation neural networks with Resilient back-propagation learning method were used. Each input vector included information about the mining tremor energy and the epicentral distance. Values of acceleration response spectrum were expected as the outputs of neural networks. Neurally evaluated spectra were compared with spectra computed on the basis of experimental data. After the network is trained and tested, it can be used for mapping of new data of mining tremor energies and epicentral distances into the spectra. Then, what is the substantial advantage of neural approach, the prediction of acceleration response spectra can be performed without recording of surface vibrations. In the light of the results, it is visible that the presented way of computation of acceleration response spectra can be peculiarly applied to prognosis of mining tremors influences on structures. 相似文献
387.
Satellite-data allows the magnetic field produced by the dynamo within the Earth’s core to be imaged with much more accuracy than previously possible with only ground-based data. Changes in this magnetic field can in turn be used to make some inferences about the core surface flow responsible for them. In this paper, we investigate the improvement brought to core flow computation by new satellite-data based core magnetic field models. It is shown that the main limitation now encountered is no longer the (now high) accuracy of those models, but the “non-modelled secular variation” produced by interaction of the non-resolvable small scales of the core flow with the core field, and by interaction of the (partly) resolvable large scales of the core flow with the small scales of the core field unfortunately masked by the crustal field. We show how this non-modelled secular variation can be taken into account to recover the largest scales of the core flow in a consistent way. We also investigate the uncertainties this introduces in core flows computed with the help of the frozen-flux and tangentially geostrophic assumptions. It turns out that flows with much more medium and small scales than previously thought are needed to explain the satellite-data-based core magnetic field models. It also turns out that a significant fraction of this flow unfortunately happens to be non-recoverable (being either “non-resolvable” because too small-scale, or “invisible”, because in the kernel of the inverse method) even though it produces the detectable “non-modelled secular variation”. Applying this to the Magsat (1980) to Ørsted (2000) field changes leads us to conclude that a flow involving at least strong retrograde vortices below the Atlantic Hemisphere, some less-resolved prograde vortices below the Pacific Hemisphere, and some poorly resolved (and partly non-resolvable) polar vortices, is needed to explain the 1980-2000 satellite-era average secular variation. The characteristics of the fraction of the secular variation left unexplained by this flow are also discussed. 相似文献
388.
Tetsuya Komabayashi Soichi Omori Shigenori Maruyama 《Physics of the Earth and Planetary Interiors》2005,153(4):191-209
Fluid-undersaturated experiments were conducted to determine the phase relations in the simplified peridotite system MgO-SiO2-H2O (MSH) at 11.0-14.5 GPa and 800-1400 °C. Stability relations of dense hydrous magnesium silicates (DHMSs) under fluid-undersaturated conditions were experimentally examined. From the fluid-absent experimental results, we retrieved thermodynamic data for clinohumite, phase A, phase E, and hydrous wadsleyite, consistent with the published data set for dry mantle minerals. With this new data set, we have calculated phase equilibria in the MSH system including dehydration reactions. The dehydration reactions calculated with lower water activities of 0.68-0.60 match the fluid-present experiments of this study above 11.0 GPa and 1000 °C, indicating that considerable amounts of silicate component were dissolved into the fluid phase. The calculated phase equilibria illustrate the stability of the post-antigorite phase A-bearing assemblages. In the cold subducting slab peridotite, phase A + enstatite assemblage survives into the transition zone, whereas phase A + forsterite + enstatite assemblage forms hydrous wadsleyite at a much shallower depth of about 360-km. The slab is subducted with no dehydration reactions occurring when entering the transition zone. The phase equilibria also show the high temperature stability of phase E. Phase E is stable up to 1200 °C at 13.5 GPa, a plausible condition in the mantle of relatively low temperature, i.e., beneath subduction zones. Phase E is a possible water reservoir in the mantle as well as wadsleyite and ringwoodite. 相似文献
389.
390.
通过对乾陵地震台DSC2A型数据采集器雷害故障现象特征、诊断修复过程、故障原因等的分析,提出了数据采集器雷害故障检修的一般步骤方法,并认为,数据采集器内部模拟输入通道转换继电器和通道程控放大电路ICL7650集成运放块易遭雷击损坏,是故障率较高的部件。 相似文献