全文获取类型
收费全文 | 7602篇 |
免费 | 1150篇 |
国内免费 | 1861篇 |
专业分类
测绘学 | 432篇 |
大气科学 | 1943篇 |
地球物理 | 1870篇 |
地质学 | 3491篇 |
海洋学 | 1017篇 |
天文学 | 372篇 |
综合类 | 706篇 |
自然地理 | 782篇 |
出版年
2024年 | 27篇 |
2023年 | 112篇 |
2022年 | 304篇 |
2021年 | 344篇 |
2020年 | 280篇 |
2019年 | 345篇 |
2018年 | 364篇 |
2017年 | 320篇 |
2016年 | 420篇 |
2015年 | 351篇 |
2014年 | 426篇 |
2013年 | 451篇 |
2012年 | 346篇 |
2011年 | 378篇 |
2010年 | 348篇 |
2009年 | 415篇 |
2008年 | 329篇 |
2007年 | 307篇 |
2006年 | 277篇 |
2005年 | 279篇 |
2004年 | 208篇 |
2003年 | 234篇 |
2002年 | 205篇 |
2001年 | 222篇 |
2000年 | 278篇 |
1999年 | 417篇 |
1998年 | 322篇 |
1997年 | 321篇 |
1996年 | 321篇 |
1995年 | 273篇 |
1994年 | 226篇 |
1993年 | 203篇 |
1992年 | 163篇 |
1991年 | 136篇 |
1990年 | 113篇 |
1989年 | 116篇 |
1988年 | 101篇 |
1987年 | 55篇 |
1986年 | 60篇 |
1985年 | 44篇 |
1984年 | 39篇 |
1983年 | 20篇 |
1982年 | 20篇 |
1981年 | 24篇 |
1980年 | 18篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1976年 | 6篇 |
1973年 | 7篇 |
1958年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
A fast intensity-hue-saturation fusion technique with spectral adjustment for IKONOS imagery 总被引:11,自引:0,他引:11
Te-Ming Tu Huang P.S. Chung-Ling Hung Chien-Ping Chang 《Geoscience and Remote Sensing Letters, IEEE》2004,1(4):309-312
Among various image fusion methods, intensity-hue-saturation (IHS) technique is capable of quickly merging the massive volumes of data. For IKONOS imagery, IHS can yield satisfactory "spatial" enhancement but may introduce "spectral" distortion, appearing as a change in colors between compositions of resampled and fused multispectral bands. To solve this problem, a fast IHS fusion technique with spectral adjustment is presented. The experimental results demonstrate that the proposed approach can provide better performance than the original IHS method, both in processing speed and image quality. 相似文献
42.
Chen-Tung Arthur Chen Jiunn-Tzong Wu Bing-Jye Wang Kuo-Ming Huang 《Aquatic Geochemistry》2004,10(1-2):33-57
One hundred and eighty lakes, ponds and reservoirs in Taiwan, and the offshore islands have been investigated since 1985. Effects such as warming/cooling, mixing, photosynthesis and respiration on pH have been identified. These effects were found to be less profound than those resulting from the geology. Since there is little rain or lake water pH data available prior to 1970, it was necessary to use proxy data in order to ascertain the history of lake acidification. In this study, we present data based on diatoms in a sediment core collected from a lake in the remote subalpine region of southern Taiwan. The acidity of this lake water was found to have increased since 1900. We measured the concentrations of 55 chemical species in lake water samples. In addition, concentrations of 26 chemical species were obtained from sediments. Conductivity, alkalinity (HCO3 ?), most other major and minor chemical species, as well as the non sea-salt SO4/Na ratio in lake water clearly decrease with elevation. Distribution of pH is similar, although the trend is less clear. Distribution of trace metals, however, shows a different trend as anthropogenic pollution, diagenetic reduction and lake acidification are at play. 相似文献
43.
This paper explores the concept of sustainable tourism and how it applies to urban destinations such as Singapore. As tourism is an important industry in Singapore, in terms of employment, business activity and an income generator, the Singapore Tourism Board is continuously looking at potential avenues to make Singapore a competitive destination. We examine the use of thematic zones in Singapore as a strategy to achieve its ambition of becoming a tourism capital of the world. By focusing on a case study of the Singapore River thematic zone (one of the 11 thematic zones identified by the Singapore Tourism Board), we assess the viability of thematic zones in ensuring sustainable urban tourism. The paper closes with some theoretical reflections and policy implications arising from our key findings. 相似文献
44.
数字化形变台站日常下载、处理直至管理数据,都应用《数字化通讯控制软件》、《形变前兆台站(网)数据处理系统》及《形变前兆数据库服务软件(台站版)》等三个软件交互进行,在实际使用过程中会遇到一些棘手的问题。本文结合我台的观测工作的实践,总结经验,以供台站同行共享。 相似文献
45.
Multi-dimensional Seismic Response Analysis of Base-Isolated Frame Structure with 3D Isolator 总被引:1,自引:0,他引:1
XiongShishu HuangLiting ChenJinfeng SuJingsu 《中国地质大学学报(英文版)》2005,16(1):66-71,78
INTRODUCTIONAs a new and effective method for withstandingthe horizontal component of earthquake motion on abuilding structure, the base isolation technique hascome to the engineering application phase ( Hu,1988). However, for some important buildings andfoundation facilities in an earthquake region, it is im portant to consider the effects of 3D aseismatic analy sis, including the vertical component, due to themulti dimensional characteristics of earthquakes (Suand … 相似文献
46.
He-Xin Liu Yue Huang Guang-Cheng Xiao Qing-Cui Bu Jin-Lu Qu Shu Zhang Shuang-Nan Zhang Shu-Mei Jia Fang-Jun Lu Xiang Ma 《天文和天体物理学研究(英文版)》2021,(3):193-204
We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846-031 during its outburst in 2019 with the observations ... 相似文献
47.
以综合催熟措施和移植精荚手术相结合的技术方法,解决了鱼塭产斑节对虾催熟效应期长,产卵率低,易蜕壳失去精荚等难题。使用 278 尾雌虾,催熟率达90% 以上,在40 d 内共产卵608 尾次,卵量18 530 万粒,孵出无节幼体11 998 万尾,平均孵化率 64.7% ,平均每尾雌虾孵出无节幼体 43.1 万尾,育成商品虾苗 1 028.5 万尾,育苗平均成活率 13.6% ,试养成活率57.1% 相似文献
48.
一次辽宁秋季暴雨天气的诊断分析 总被引:1,自引:0,他引:1
使用1.0°×1.0°NCEP再分析资料,对2006年10月21—22日深秋暴雨在天气形势分析的基础上,进行物理量诊断。结果表明:在有利的环境背景形势下,高位涡从对流层高层向低层伸展并形成湿位涡柱,引起气旋性环流与低涡环流叠加。对流层低层的湿斜压性增强,引起低层的锋区加强及垂直涡度发展,高空入侵干冷空气锲入底层,低层暖湿空气强迫抬升,使地面发展为气旋;高低空急流耦合产生上升气流,同时较强的补偿下沉运动激发上升运动加强,使次级环流加强,触发不稳定能量的释放;低空急流和超低空急流向辽宁输送暖湿空气及能量,对流层中低层形成湿柱并积聚高不稳定能量;中尺度气旋、高低空急流、湿位涡柱、次级环流上升支、地面高水汽含量湿区、高假相当位温出现的时间、强度、位置和结构决定了暴雨的时间和落区。 相似文献
49.
海相沉积成因的黑滑石矿床是近年来在我国发现的新的成因类型矿床,本文除着重介绍在川东南发现的海相沉积成因的黑滑石矿床地质特征和矿床成因外,还引进非金属矿床含矿建造和成矿系列的概念,提示黑滑石矿及与其共生伴生的其它非金属矿的找矿方向。 相似文献
50.
The layered intrusions in the Panzhihua-Xichang area may be grouped into two types: basic rock masses represented by the Panzhihua
rockbody and basic-ultrabasic rock masses represented by the Hongge rockbody. Their major difference lies in that the former
has poorly developed ultramafic facies, while the latter is characterized by well developed mafic facies and ultramafic facies.
There exists apparent rhythmic stratification in the rock masses, which can be basically divided into four grades in terms
of superimposition relationship and multicycle characters.
Both direct and indirect evidence suggest that the magma responsible for the layered intrusions in this area should be a transition-type
alkaline olivine basalt magma derived directly from partial melting of the upper mantle. In rhythmic cycles of various grades,
the magmatic evolution is characterized obviously by periodicity and early enrichment of Fe and Ti, which is evidently different
from the evolution of the Skaergaard magma in which Fe and Ti are enriched at the late stage. The FCA diagram can be used
to describe the unique evolutionary trend of magma in this area. It is demonstrated in this diagram that the enrichment of
Fe and Ti is consistent with the increase of basicity.
In the upper magmatic chamber, the evolutionary trend of magma is conditioned by the difference in pressure, and this enables
magma to form different types of rock assemblage. In the Fo-Di-An system, when the pressure exceeds 5 x 188 Pa, forsterite is incompatible with anorthite, and the rock facies sequence of Hongge type might form; when the pressure
is lower than 5 x 108 Pa, forsterite can coexist with anorthite, and the rock facies sequence of Panzhihua type is likely to form if the magma
is relatively rich in Mg and Fe components. 相似文献