全文获取类型
收费全文 | 6079篇 |
免费 | 1321篇 |
国内免费 | 1756篇 |
专业分类
测绘学 | 754篇 |
大气科学 | 884篇 |
地球物理 | 1353篇 |
地质学 | 3497篇 |
海洋学 | 976篇 |
天文学 | 265篇 |
综合类 | 645篇 |
自然地理 | 782篇 |
出版年
2024年 | 47篇 |
2023年 | 133篇 |
2022年 | 432篇 |
2021年 | 470篇 |
2020年 | 388篇 |
2019年 | 422篇 |
2018年 | 463篇 |
2017年 | 408篇 |
2016年 | 477篇 |
2015年 | 428篇 |
2014年 | 457篇 |
2013年 | 485篇 |
2012年 | 464篇 |
2011年 | 445篇 |
2010年 | 434篇 |
2009年 | 376篇 |
2008年 | 331篇 |
2007年 | 299篇 |
2006年 | 307篇 |
2005年 | 217篇 |
2004年 | 159篇 |
2003年 | 141篇 |
2002年 | 125篇 |
2001年 | 119篇 |
2000年 | 116篇 |
1999年 | 165篇 |
1998年 | 110篇 |
1997年 | 110篇 |
1996年 | 90篇 |
1995年 | 91篇 |
1994年 | 78篇 |
1993年 | 73篇 |
1992年 | 56篇 |
1991年 | 39篇 |
1990年 | 33篇 |
1989年 | 38篇 |
1988年 | 18篇 |
1987年 | 18篇 |
1986年 | 26篇 |
1985年 | 23篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1965年 | 2篇 |
1958年 | 3篇 |
1957年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有9156条查询结果,搜索用时 31 毫秒
461.
本文报道了蛇纹石族矿物及其热转变产物的红外光谱。在室温下斜纤蛇纹石,正纤蛇纹石,叶蛇纹石和利蛇纹石都具有各自的特征光谱。在结构资料基础上,我们解释了它们之间的光谱差异。无疑,红外光谱是区分各种蛇纹石矿物的有效手段。 样品加热到600—700℃时,3680cm~(-1)羟基带消失,这表明在该温度下蛇纹石矿物完全脱羟。与此同时,光谱中出现橄榄石870cm~(-1)的最强带和一个宽带1000cm~(-1),这说明蛇纹石已部分地转变为晶质橄榄石和形成一个无定形的中间相。800℃时,1060cm~(-1)新带的出现标志着顽火辉石的生成。在所有加热样品的光谱中都没有发现SiO_2吸收带,故可认为,在蛇纹石的热转变过程中没有出现SiO_2相。 相似文献
462.
在30kbar和900℃条件下,用等化学计量氧化物混合物合成了11个斜方辉石系列的样品,并对合成的样品进行了X射线粉晶分析和红外光谱分析。分析结果表明,晶胞参数和红外光谱随化学成分的改变而产生复杂的变化。不仅晶胞参数b和M而且频率ν_(670cm)-1和M之间存在很好的线性相关关系,通过用最小二乘法所拟合的相关方程可容易地测定斜方辉石的成分,但是α和c与M之间只有较差的线性关系,而ν_(450cm)-1和M以及ν_(380cm)-1和M之间并无简单的线性相关关系,这可归因于Fe~(2+)在M_1和M_2位置的有序分布。 相似文献
463.
M Andree H Oeschger W Broecker N Beavan M Klas A Mix G Bonani H J Hofmann M Suter W Woelfli T-H Peng 《Climate Dynamics》1986,1(1):53-62
In this paper we present accelerator radiocarbon measurements on hand picked benthic and planktonic foraminifera separated from two deep sea cores raised from the South China Sea. From the benthic-planktonic age differences we are able to place limits on the extent to which the ventilation rate of the deep Pacific Ocean has changed over the last 12000 years. While much work remains to be done before any definitive answers for the global oceans can be given, these results on cores with sedimentation rates suitably high to avoid major corrections for bioturbation effects suggest that the ventilation rate of the deep Pacific Ocean has remained nearly the same throughout Holocene time. Further, there is no suggestion that the rate was slower during the period of major glacial retreat. These results confirm that the changes in atmospheric14C/C ratio over the last 10000 years owe their origin to radiocarbon production rate changes. 相似文献
464.
Peng Wang Lei Liu Xichuan Liu Shuai Hu Shijun Zhao Wenming Ji Taichang Gao 《地球科学进展》1986,35(7):704-714
The accurate observation of the microphysical structure of cloud and precipitation plays an important role in understanding the formation of clouds and precipitation. In-situ measurement using measuring instruments carried by meteorological balloons is an effective way to obtain the microphysical properties of cloud and precipitation particles, which is a supplementary means for aircraft to observe cloud and precipitation particles. This observation method plays a more and more important role in in-situ measurement. According to the difference of the working principle of the existing balloon-borne cloud and precipitation particles probes, the detectors can be divided into particle impact-sampling sensors, particle imaging sensors, light-scattering sensors, light intensity attenuation sensors and charge measurement sensors. The working principles, key technologies and main advantages and disadvantages of typical instruments were summarized, and their applications to detailed cloud structure acquisition, cloud remote sensing method establishment, cloud and precipitation physical process research and parameterization, and scientific observation of thunderstorm clouds were briefly introduced. Finally, the development trend of balloon-borne cloud precipitation particle detectors was prospected, which will provide reference for related technical research and equipment development. 相似文献
465.
466.
467.
468.
本文对如何利用强震加速度记录测定近震震级ML的问题进行了研究,指出了在我国所使用的原始量规函数存在着系统偏差,并用回归现有观测资料的方法修正了这种系统偏差。用修正后的量规函数,利用近场加速度记录计算的ML值同微震台网所测定的值符合得较好,说明本文所提出的方法是可行的。 相似文献
469.
470.
Xia Wenchen Zhou Jie Lei Jianxi Zhang Nianmao Peng YangChina U niversity of Geoscience W uhan Hubei Wang Yujun 《《地质学报》英文版》1995,69(4):341-357
On the basis of exhaustive researches on the facies sequences and depositlonal evolutionary process of various depositional systems, the genetic stratigraphic framework of the extensional rifted oceanic basin, which has undergone strong structural destruction, has been reconstructed by means of dynamic genetic stratigraphic analysis. Five depositional episodes have been distinguished from various isochronous stratigraphic boundaries and stratigraphic sequences with the three-dimensional structure of each depositional episode analysed in detail. The tectonic paleogeographic environment corresponding to different stages of each depositional episode has been reconstructed for individual depositional system tracts. And the evolution history of this rifted basin has been divided into four stages' initial rifting and oceanization of continental crust, stretching and spreading of the basin, subduction and basin differentiation, and convergence and collision. A NNE-trending intracontinental soft collision sutur 相似文献