全文获取类型
收费全文 | 31577篇 |
免费 | 1319篇 |
国内免费 | 2728篇 |
专业分类
测绘学 | 1816篇 |
大气科学 | 3861篇 |
地球物理 | 6264篇 |
地质学 | 14911篇 |
海洋学 | 2009篇 |
天文学 | 1997篇 |
综合类 | 2789篇 |
自然地理 | 1977篇 |
出版年
2024年 | 27篇 |
2023年 | 113篇 |
2022年 | 308篇 |
2021年 | 349篇 |
2020年 | 282篇 |
2019年 | 349篇 |
2018年 | 5011篇 |
2017年 | 4263篇 |
2016年 | 2909篇 |
2015年 | 577篇 |
2014年 | 505篇 |
2013年 | 477篇 |
2012年 | 1326篇 |
2011年 | 3074篇 |
2010年 | 2338篇 |
2009年 | 2688篇 |
2008年 | 2186篇 |
2007年 | 2618篇 |
2006年 | 329篇 |
2005年 | 469篇 |
2004年 | 603篇 |
2003年 | 637篇 |
2002年 | 449篇 |
2001年 | 269篇 |
2000年 | 332篇 |
1999年 | 431篇 |
1998年 | 340篇 |
1997年 | 325篇 |
1996年 | 321篇 |
1995年 | 274篇 |
1994年 | 229篇 |
1993年 | 204篇 |
1992年 | 165篇 |
1991年 | 138篇 |
1990年 | 114篇 |
1989年 | 116篇 |
1988年 | 101篇 |
1987年 | 56篇 |
1986年 | 60篇 |
1985年 | 44篇 |
1984年 | 39篇 |
1983年 | 20篇 |
1982年 | 20篇 |
1981年 | 45篇 |
1980年 | 37篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1976年 | 12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 15 毫秒
51.
52.
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
53.
Ninad R. Bondre Raymond A. Duraiswami Gauri Dole 《Journal of Earth System Science》2004,113(4):809-817
The nature and style of emplacement of Continental Flood Basalt (CFB) lava flows has been a matter of great interest as well
as considerable controversy in the recent past. However, even a cursory review of published literature reveals that the Columbia
River Basalt Group (CRBG) and Hawaiian volcanoes provide most of the data relevant to this topic. It is interesting to note,
however, that the CRBG lava flows and their palaeotopographic control is atypical of other CFB provinces in the world. In
this paper, we first present a short overview of important studies pertaining to the emplacement of flood basalt flows. We
then briefly review the morphology of lava flows from the Deccan Volcanic Province (DVP) and the Columbia-Oregon Plateau flood
basalts. The review underscores the existence of significant variations in lava flow morphology between different provinces,
and even within the same province. It is quite likely that there were more than one way of emplacing the voluminous and extensive
CFB lava flows. We argue that the establishment of general models of emplacement must be based on a comprehensive documentation
of lava flow morphology from all CFB provinces. 相似文献
54.
Pollution history and recovery of a boreal lake exposed to a heavy bleached pulping effluent load 总被引:4,自引:0,他引:4
Juhani Hynynen Arja Palomäki Jarmo J. Meriläinen Allan Witick Keijo Mäntykoski 《Journal of Paleolimnology》2004,32(4):351-374
We examined the effects of heavy pulp mill discharges on the Lake Lievestuoreenjärvi ecosystem and the later recovery of diatom and chironomid communities from age-dated short core samples. Beginning in 1927 the lake received a heavy effluent load from a sulphite pulp mill. Except for the recession during the Second World War and the temporary closure of the mill from 1967 to 1971, the industrial load, containing large quantities of nutrients, organic matter and toxic compounds, increased continuously. In the early 1980s, laboratory documents were falsified by the directors of the mill and the systematic illegal effluent overload led to a collapse of the whole lake ecosystem. In 1985, the outdated plant was finally closed down. Based on the assessment of chemical properties and biological remains of the sediment, we distinguished five developmental phases in the ecological state of the lake. In the pre-industrial phase, the pelagic and profundal benthic communities were dominated by species preferring ultraoligotrophic or oligotrophic lakes. Concomitant with the increasing discharge and deposition of chlorine compounds, resin acids, and mercury, as well as strong acidity and hypolimnetic and epilimnetic anoxia, the ecological status changed in a short period from excellent to bad. Finally, in the early 1960s, the majority of the lake was virtually dead and the aquatic life survived only in the uppermost littoral zone. Since 1985, a fast recovery in the water quality has led to a strong, but temporary eutrophy in pelagic communities. The main peak of eutrophication was caused by the invasion of a species new to the lake,Aulacoseira granulata var.angustissima. Later, the pelagic communities shifted towards oligotrophy, but the original, pre-industrial status has not been re-established. The profundal benthic communities have not achieved the pre-industrial structure, but at present indicate mesotrophy. 相似文献
55.
基于二维小波变换的FMI图象分割 总被引:1,自引:0,他引:1
为了从FMI资料中定量提取参数,一个重要的步骤是从实际FMI资料中分离出反映溶孔、溶洞、裂缝的子图像。本文给出的方法,考虑图像像元邻域的特征,应用二维小波变换求出目标与背景边缘的点集,按这个边缘点集的坐标点所对应的原图像像素灰度值的平均值作为分割阈值进行图像分割。实际资料处理表明,应用这种方法可以从实际的FMI资料中准确地分割出孔洞、裂缝的子图像并且可以按深度段连续自动处理,为后续定量计算参数奠定了良好基础。 相似文献
56.
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
57.
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
58.
改进的能量守恒方法及其在CHAMP重力场恢复中的应用 总被引:1,自引:0,他引:1
XU Tianhe HE Kaifei Xi’an Research Institute of Surveying Mapping Middle Yanta Road Xi’an China. 《地球空间信息科学学报》2008,11(3):168-173
An efficient method for gravity field determination from CHAMP orbits and accelerometer data is referred to as the energy balance approach. A new CHAMP gravity field recovery strategy based on the improved energy balance approach IS developed in this paper. The method simultaneously solves the spherical harmonic coefficients, daily Integration constant, scale and bias parameters. Two 60 degree and order gravitational potential models, XISM-CHAMPO1S from the classical energy balance approach, and XISM-CHAMPO2S from the improved energy balance, are determined using about one year's worth of CHAMP kinematic orbits from TUM and accelerometer data from GFZ. Comparisons among XISM-CHAMPO1S, XISM-CHAMPO2S, EIGEN-CGO3C, EIGEN-CHAMPO3S, EIGEN2, ENIGNIS and EGM96 are made. The results show that the XISM-CHAMPO2S model is more accurate than EGM96, EIGENIS, EIGEN2 and XISM-CHAMPO1S at the same degree and order, and has almost the same accuracy as EIGEN-CHAMPO3S. 相似文献
59.
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
60.
Building damage in Dujiangyan during Wenchuan Earthquake 总被引:2,自引:1,他引:1
A field damage survey of 1,005 buildings damaged by the Wenchuan Earthquake in Dujiangyan City was carried out and the resulting data was analyzed using the statistical method. It is shown that buildings that were seismically designed achieved the desired seismic fortification target; they sustained less damage than the non-seismically designed buildings. Among the seismically designed buildings investigated, RC frame buildings performed the best in terms of seismic resistance. Masonry buildings with a ground story of RC frame structure were the second best, and masonry buildings performed the worst. Considering building height, multistory buildings sustained more severe damage than high-rise buildings and 2- and 3-story buildings. Compared to residential buildings, public buildings, such as schools and hospitals, suffered more severe damage. 相似文献