全文获取类型
收费全文 | 2221篇 |
免费 | 435篇 |
国内免费 | 454篇 |
专业分类
测绘学 | 143篇 |
大气科学 | 366篇 |
地球物理 | 501篇 |
地质学 | 1232篇 |
海洋学 | 172篇 |
天文学 | 223篇 |
综合类 | 240篇 |
自然地理 | 233篇 |
出版年
2024年 | 14篇 |
2023年 | 49篇 |
2022年 | 137篇 |
2021年 | 143篇 |
2020年 | 91篇 |
2019年 | 116篇 |
2018年 | 139篇 |
2017年 | 104篇 |
2016年 | 104篇 |
2015年 | 107篇 |
2014年 | 127篇 |
2013年 | 141篇 |
2012年 | 125篇 |
2011年 | 113篇 |
2010年 | 101篇 |
2009年 | 115篇 |
2008年 | 86篇 |
2007年 | 100篇 |
2006年 | 74篇 |
2005年 | 81篇 |
2004年 | 54篇 |
2003年 | 48篇 |
2002年 | 60篇 |
2001年 | 75篇 |
2000年 | 92篇 |
1999年 | 105篇 |
1998年 | 92篇 |
1997年 | 87篇 |
1996年 | 66篇 |
1995年 | 59篇 |
1994年 | 49篇 |
1993年 | 54篇 |
1992年 | 30篇 |
1991年 | 31篇 |
1990年 | 28篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 18篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 2篇 |
1958年 | 4篇 |
排序方式: 共有3110条查询结果,搜索用时 0 毫秒
31.
Introduction Since 1920s, with increasing awareness of disaster prevention and reduction in various as-pects and gradually deepened development of International Decade for Natural Disaster Reduction (IDNDR) activities in China, the role and position of disaster risk analysis and risk management work are increasingly prominent. In the final report of the IDNDR activities in 1999, the Science and Technology Committee of IDNDR had presented 5 challenge fields, which the international dis… 相似文献
32.
This paper studies the temporal and spatial distribution of great global earthquakes( M W≥8.0) since 1900.We compare the two periods of upsurges of great earthquakes occurring in the middle of last century and beginning of this century.The former period took place between 1950 and 1965 during which 13 great earthquakes( M W≥ 8.0) occurred,including three events with moment magnitude greater than 9.0.The largest magnitude in this period reached 9.6.The latter period starts from the beginning of this century.In less than 12 years,15 great earthquakes have attacked the world with the largest magnitude being M W9.1.On the basis of comparison between these two upsurges of global earthquake activity,we infer that the ongoing high level of earthquake activity may continue for another five years or so.Numerous great earthquakes( M W≥8.0) and many large earthquakes( M W6.0~7.0) will occur globally in these five years.In addition,this paper also discusses the relationships between earthquake activity along the Sumatra segment of the Indian-Australia plate boundary and that in the Bayankala block in the middle of Qinghai-Tibetan plateau as well as in the blocks of the southern plateau.The results indicate that the Qinghai-Tibetan plateau,in particular its middle and southern parts,is a likely place for future earthquakes of magnitude over 7.0. 相似文献
33.
Spectroscopic Study of Natural Diamonds in China 总被引:2,自引:0,他引:2
It has become clear in recent years that the important substitutional impurities in diamond are nitrogen,hydrogen and boron(Bibby,D.M.,1982).The physical and chemical properties of diamond are determined by the content and form of occurence of nitrogen based on which diamonds are generally classified.The well-known experiments concerning the mutual transformation of the forms the origin of diamond.by Evans.T.Et al.(1982) have provided a theoretic basis for the origin of diamond.Since 1979,spectroscopic investigation of natural diamonds from different areas in china has been carried out using UV-visible and IR spectrophotometer,EPR and cathodoluminescence techniques.We have conducted the classification of natural cathodoluminescence techniques.We have conducted the classification of natural diamonds in China and studies on the forms of nitrogen and hydrogen,the radiation damage and their geological implications.Spectroscopic characteristics of natural diamonds in china and their geological implications are discussed in this paper. 相似文献
34.
Due to the continuous and intense rainfall from June 26 to 28, 2016, Xinlu Village in Ganshui Town, Qijiang District, Chongqing, experienced a unitary-slip landslide at approximately UTC+8 19:30 on June 28. This landslide disrupted the Chuan-Qian railway and damaged four residential buildings. To analyze and rehabilitate the landslide, the engineering geology, hydrological conditions, and deformation instability mechanism of this landslide were investigated and comprehensively analyzed based on an in situ survey, geophysical drilling, and a laboratory quick-shearing test. The results show that the landslide is a typical gradual progressive landslide. 相似文献
35.
36.
Urbanization in modern times led to a series of development strategies that brought new opportunities in China. Rapid urbanization caused severe stress to the ecosystems and the environment. Using the center-of-gravity(COG) method and parameters such as population, economy, and land, we studied the urbanization pattern in Songhua River Basin and its southern source sub-basin from 1990 to 2010. Urbanization was analyzed based on the COG position, eccentric distance, movement direction of COG, and distance of COG movement. Various characteristics of urbanization in the southern source sub-basin of the Songhua River were explained in relation to the whole Songhua River Basin. Urbanization in the southern source sub-basin of the Songhua River is balanced, relatively advanced, and stable compared to the whole Songhua River Basin. The average eccentric distance between the urbanization COGs in the Songhua River′s south source basin indicated rapid expansion of land urbanization during the span of this study. A basic pattern of urbanization COG in the whole Songhua Basin was observed, but there existed differences among the three aspects of urbanization process. Land urbanization is still in its active stage, so future studies should focus on analysis of such urbanization trends. 相似文献
37.
Solar Physics - A curved filament in a decaying active region (AR&;nbsp;8329) was observed on 9 September 1998 with a combination of several instruments. The main data base is a 4-hour long time... 相似文献
38.
Yu Xin Xiao-Bin Zhang Li-Cai DengNational Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2002,2(6)
We present a snapshot of our recent results of a variable star survey in 1 degree fields around three open clusters: NGC 188, NGC 7789 and M67. A total number of 39 variable stars are newly discovered, including 22 W UMa stars, 10 EA (Algol) type binaries, one RR-lyr and one RRd pulsator, and five unclassified variables. 相似文献
39.
40.
We have investigated the correlations among color, morphology and luminosity for all LRGs, cut I LRGs, cut II LRGs, and Main
galaxies that are also classified as LRGs. It is found that the morphology of LRGs is tightly correlated with luminosity.
The rest-frame u-g color of cut I LRGs and cut II LRGs is nearly independent of luminosity, but the color of Main galaxies
is correlated with luminosity. For cut I LRGs and Main galaxies, the early type proportion apparently changes with color:
at the rest-frame u-g < 1.3 it increases strongly with increasing color, while at the rest-frame u-g > 1.3 it decreases with
increasing color. We also notice that the morphology of cut II LRGs is only a weak function of color.
Published in Astrofizika, Vol. 50, No. 3, pp. 335–345 (August 2007). 相似文献