全文获取类型
收费全文 | 9440篇 |
免费 | 1661篇 |
国内免费 | 2215篇 |
专业分类
测绘学 | 502篇 |
大气科学 | 1908篇 |
地球物理 | 2548篇 |
地质学 | 4763篇 |
海洋学 | 940篇 |
天文学 | 522篇 |
综合类 | 934篇 |
自然地理 | 1199篇 |
出版年
2024年 | 52篇 |
2023年 | 164篇 |
2022年 | 419篇 |
2021年 | 474篇 |
2020年 | 420篇 |
2019年 | 509篇 |
2018年 | 568篇 |
2017年 | 486篇 |
2016年 | 577篇 |
2015年 | 461篇 |
2014年 | 606篇 |
2013年 | 520篇 |
2012年 | 487篇 |
2011年 | 574篇 |
2010年 | 541篇 |
2009年 | 502篇 |
2008年 | 461篇 |
2007年 | 476篇 |
2006年 | 357篇 |
2005年 | 290篇 |
2004年 | 283篇 |
2003年 | 279篇 |
2002年 | 292篇 |
2001年 | 260篇 |
2000年 | 302篇 |
1999年 | 387篇 |
1998年 | 332篇 |
1997年 | 335篇 |
1996年 | 278篇 |
1995年 | 241篇 |
1994年 | 288篇 |
1993年 | 219篇 |
1992年 | 167篇 |
1991年 | 129篇 |
1990年 | 104篇 |
1989年 | 77篇 |
1988年 | 98篇 |
1987年 | 50篇 |
1986年 | 45篇 |
1985年 | 41篇 |
1984年 | 36篇 |
1983年 | 33篇 |
1982年 | 35篇 |
1981年 | 27篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1975年 | 2篇 |
1958年 | 7篇 |
1954年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
本文对采集于甘肃省兰州市海石湾镇中侏罗统窑街组的一块真蕨类化石进行了系统描述。当前标本最显著的特征是,小羽片分裂2~3次,相邻羽片相互接触或略叠覆,同时保留有完整的实羽叶,通过与前人已报道的蕨叶、叶脉、羽片、小羽片分裂的程度及裂片形状等特征的对比分析,发现其与Coniopteris nikaensis的基本特征完全符合,可明确该化石植物为C.nikaensis,属于窑街盆地的首次报道。经过实验分析,揭示了C.nikaensis的原位孢子基本特征:孢子三缝,赤道轮廓亚三角形,三边微凹,顶角钝圆,直径平均约35 μm;射线较窄且平直,具微弱发育的唇,长度约为孢子体半径的3/4或更长;外壁薄,表面光滑。本研究为完善窑街盆地古植物群面貌提供了新材料,窑街盆地和宝积山盆地相较伊犁盆地更适宜Coniopteris的生长。 相似文献
82.
83.
1999年全世界地震灾害综述 总被引:2,自引:0,他引:2
1999年全球地震活动为中等水平 ,但地震灾情较重。重大地震灾害分别发生在土耳其、中国台湾省和哥伦比亚。地震死亡人数总计 2 3 3 11人 ,伤 64 2 91人 ,经济损失约 3 0 0亿美元。台湾 7.6级地震是中国自唐山地震以来最严重的震灾。 相似文献
84.
正We report the first near real-time inverted echo sounder (IES) observation in the South China Sea (Fig.1).Although the first IES observation in the South China Sea was in 2005,and the near real-time IES observation module was first developed in 2012(http://www.po.gso.uri.edu/dynamics/IES/hist.html),the real-time IES has never been deployed in the South China Sea until the reporting of observations in this study.IES is a bottom-mounted mooring that records the round-trip acoustic travel time from the bottom to the surface and back (τ), 相似文献
85.
86.
87.
InSAR detection of residual settlement of an ocean reclamation engineering project: a case study of Hong Kong International Airport 总被引:1,自引:1,他引:1
Qing Zhao Hui Lin Wei Gao Howard A. Zebker Albert Chen Kin Yeung 《Journal of Oceanography》2011,67(4):415-426
Man-made land or islands that are reclaimed from the sea are suitable for building airports, harbors, and industry parks for
material transportation because of their broad air and land spaces. However, the reclaimed foundation settlement process is
of public concern, including the continuous impact of ocean processes on its stability. The majority of the buildings and
facilities of Hong Kong International Airport (HKIA) are built on a reclaimed foundation. The reclaimed foundation has been
in residual settlement since completion of the filling project in 1994. In this study, we use persistent scatterer interferometry
(PSI) and ENVISAT (European Satellite) advanced synthetic aperture radar (ASAR) data to detect the residual settlement rates
from 19 April 2006 to 9 January 2008. We use ground truth data to develop empirical correction models for correcting systematic
biases in the ASAR PSI-detected settlement rates. The corrected data follow the Lorentz distribution well, implying that the
residual settlement process is dominated by two modes or categories of settlement rates. The first category represents a relatively
stable state and the second category represents a continuous settlement state. A ground settlement rate map of HKIA shows
that an area of the Passenger Terminal Building and an area of the Southern Runway are two relatively stable areas. There
are two major continuous settlement areas. One covers the airport Midfield. Another is along the coastline, implying that
attention should be paid to impacts of ocean processes on the stability of airport foundations. 相似文献
88.
89.
Numerous elongated mounds and channels were found at the top of the middle Miocene strata using 2D/3D seismic data in the Liwan Sag of Zhujiang River Mouth Basin(ZRMB) and the Beijiao Sag of Qiongdongnan Basin(QDNB). They occur at intervals and are rarely revealed by drilling wells in the deepwater areas. Origins of the mounds and channels are controversial and poorly understood. Based on an integrated analysis of the seismic attribute, palaeotectonics and palaeogeography, and drilling well enco... 相似文献
90.