全文获取类型
收费全文 | 6861篇 |
免费 | 1183篇 |
国内免费 | 1859篇 |
专业分类
测绘学 | 766篇 |
大气科学 | 1333篇 |
地球物理 | 1521篇 |
地质学 | 3422篇 |
海洋学 | 1098篇 |
天文学 | 229篇 |
综合类 | 607篇 |
自然地理 | 927篇 |
出版年
2024年 | 36篇 |
2023年 | 127篇 |
2022年 | 214篇 |
2021年 | 311篇 |
2020年 | 210篇 |
2019年 | 303篇 |
2018年 | 320篇 |
2017年 | 280篇 |
2016年 | 381篇 |
2015年 | 357篇 |
2014年 | 408篇 |
2013年 | 410篇 |
2012年 | 453篇 |
2011年 | 479篇 |
2010年 | 448篇 |
2009年 | 446篇 |
2008年 | 393篇 |
2007年 | 446篇 |
2006年 | 362篇 |
2005年 | 364篇 |
2004年 | 347篇 |
2003年 | 288篇 |
2002年 | 447篇 |
2001年 | 395篇 |
2000年 | 307篇 |
1999年 | 274篇 |
1998年 | 156篇 |
1997年 | 147篇 |
1996年 | 119篇 |
1995年 | 132篇 |
1994年 | 121篇 |
1993年 | 69篇 |
1992年 | 67篇 |
1991年 | 56篇 |
1990年 | 55篇 |
1989年 | 33篇 |
1988年 | 33篇 |
1987年 | 32篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有9903条查询结果,搜索用时 0 毫秒
471.
1997年4-6月云南省地震局对滇西南重点监视区做了短临预报,但这期间未发生所预期的地震。而滇西南地区6级地震的背景和省内的前兆异常变化是明显的。为此,认为前兆异常是区域应力场增强的结果。异常与地震是相互伴生的兄弟关系,不是父子间因果关系,是造成地震虚报的主要原因。 相似文献
472.
Nans Addor Hong X. Do Camila Alvarez-Garreton Gemma Coxon Keirnan Fowler Pablo A. Mendoza 《水文科学杂志》2020,65(5):712-725
ABSTRACTLarge-sample hydrology (LSH) relies on data from large sets (tens to thousands) of catchments to go beyond individual case studies and derive robust conclusions on hydrological processes and models. Numerous LSH datasets have recently been released, covering a wide range of regions and relying on increasingly diverse data sources to characterize catchment behaviour. These datasets offer novel opportunities, yet they are also limited by their lack of comparability, uncertainty estimates and characterization of human impacts. This article (i) underscores the key role of LSH datasets in hydrological studies, (ii) provides a review of currently available LSH datasets, (iii) highlights current limitations of LSH datasets and (iv) proposes guidelines and coordinated actions to overcome these limitations. These guidelines and actions aim to standardize and automatize the creation of LSH datasets worldwide, and to enhance the reproducibility and comparability of hydrological studies. 相似文献
473.
Chen Hong-Fei Xu Wen-Yao Chen Geng-Xiong Hong Ming-Hua Peng Feng-Lin 《Solar physics》2001,204(1-2):339-349
In this paper geomagnetic disturbances at middle and low latitudes are discussed by using geomagnetic data of the magnetic
storm of 15–16 July 2000. This storm is a response to the solar Bastille Day flare on 14 July. Generally, the geomagnetic
disturbances at middle and low latitudes during a storm are mainly caused by three magnetospheric–ionospheric current systems,
such as the ring current system (RC), the partial ring current and its associated region II field-aligned currents (PR), and
the region I field-aligned currents (FA). Our results show that: (1) The northward turning of IMF-Bz started the sudden commencement of the storm, and its southward turning caused the main phase of the storm. (2) The PR- and
FA-currents varied violently in the main phase. In general, the field of the FA-current was stronger than that of the PR-current.
(3) In the first stage of the recovery phase, the RC-field gradually turned anti-parallel to the geomagnetic axis from a 15°
deviation, and the local time (Λ) pointed by the RC-field stayed at 16:00. After that, Λ rotated with the stations, and the
RC-field was not anti-parallel to the geomagnetic axis, but 5°–10° deviated. These facts suggest that the warped tailward
part of the ring current decays faster than the symmetric ring current. 相似文献
474.
You Jun-han 《Chinese Astronomy and Astrophysics》1983,7(4):315-321
This paper deals with the radio spectra of synchrotron sources with spherically symmetric non-homogeneities. It is pointed out that the Type-c spectra can be produced by such a non-homogeneity even if the source is optically thin. This model is particularly advantageous in interpreting sources with no compact characteristics and yet showing a Type-c spectrum, and the observed decrease in source size with increasing frequency. In addition, it is possible to give a uniform interpretation of the four spectral types on the basis of such a non-homogeneity. 相似文献
475.
Investigation of solid waste soil as road construction material 总被引:1,自引:0,他引:1
The geotechnical properties of solid waste soils for use as sub-base materials in road construction were investigated. A series of field tests and laboratory tests were performed to assess the physical and mechanical properties of the solid waste soils sampled from a landfill site, near to a riverside, which had been reclaimed over the last two decades. The tests showed that geotechnical properties are clearly affected by the magnitude of organic matter content. As the organic matter content increases, the maximum dry unit weight, the shear strength and bearing capacity of ground decrease, while the void ratio and compressibility increase. If the organic matter content is more than about 8% in solid waste soils, it is not suitable for use as a sub-base material in road construction due to the significant decrease of shear strength and bearing capacity. 相似文献
476.
可用于复杂地质体的波动方程基准面技术 总被引:7,自引:7,他引:0
提出改进的波动方程基准面方法,用于解决地表一致性问题,通过基准面的下移,可以使深部的信号增强,变多值走时为单值走时,从根本上消除了上覆层速度横向不均匀的影响,从而可以更好地解决复杂地质体成像问题。作者从原理上对上述观点给予了证明,而且给出利用波动方程基准面有限差分法做的实例--大庆油田“陆相断隐模型”。 相似文献
477.
478.
479.
1 Spacial Organization Optimizing Theory 1.1 The centeral place theoryThe "centeral place theory" hypothesizes that there is a region: (1) the region is a uniform plain; (2) the motion of economic activities in regions can be carried through in every directions forever; (3) the purchasing power of residents is a successive and uniform distribution; (4) the movement of consumers has rationality in space, namely, proceeding by the shortest distance. The rural settlements as the central place of… 相似文献
480.