全文获取类型
收费全文 | 274篇 |
免费 | 19篇 |
国内免费 | 21篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 5篇 |
地球物理 | 38篇 |
地质学 | 219篇 |
海洋学 | 15篇 |
天文学 | 11篇 |
综合类 | 3篇 |
自然地理 | 16篇 |
出版年
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 29篇 |
2013年 | 18篇 |
2012年 | 20篇 |
2011年 | 27篇 |
2010年 | 20篇 |
2009年 | 24篇 |
2008年 | 17篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 12篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有314条查询结果,搜索用时 15 毫秒
81.
基于ArcGIS的地图符号库的设计与实现 总被引:18,自引:0,他引:18
地理信息系统(GIS)的主要功能之一就是地图制图及输出。地图作为用户能够理解空间信息的主要图件,地图符号作为地图语言则在地图的制作和输出中起着非常重要的作用。美国ESRI公司开发的ARCGIS是功能强大的GIS软件平台,但是它的数据输入、编辑、查询与制图模块ArcMap中自带的符号库不能满足我国基本比例尺地图输出的要求,因此必须为它建立符合地图图式要求的符号库。本文重点论述了ArcGIS环境下地图符号库的设计方法,并分别讨论了点状符号、线状符号和面状符号的实现方式。 相似文献
82.
金矿体明显受断裂构造及石英脉体的双重控制。根据矿床地质特征分析,认为该矿床成因为沿构造劈理充填、改造的中低温低硫热液石英含金硫化物复合脉型矿床,具中一大型远景规模。 相似文献
83.
三江并流带旅游地质景观 总被引:4,自引:2,他引:2
强烈新构造运动造就宏伟、稀罕、绚丽的三江并流带地质奇观,蕴育丰富、珍稀的旅游地质资源。本文就三江并流带旅游地质资源类型、景观单元及其等级、景观系列、景观结构、展布特征及区划、特色进行剖析,推荐观赏三江并流旅游地质景观的特色景观组合及精品线路。 相似文献
84.
This contribution discusses the application of Chebyshev Type I filter for processing real earthquake records. Consideration
is given to the effects of filtering parameters (passband amplitude ripple and order of the filter) on the time series, strong-motion
parameters, Fourier Amplitude Spectrum of acceleration, and elastic displacement response spectra. Time histories of five
earthquakes with different moment magnitudes have been examined (from stations located close to the epicenters). Data processing
is based on application of bandpass Chebyshev filtering over frequency range with substantial signal to noise ratio (level
of 3 or approximately 3 dB). Applying different filters, we have monitored several important strong-motion parameters: peak
values of acceleration, velocity, and displacement; Arias intensity, acceleration/velocity spectrum intensity, significant
duration, etc. Some new results and conclusions concerning the influence of Chebyshev filter in data processing of records
have been summarized. The graphical and numerical outcomes obtained, as well as the comparison with a Butterworth causal filter,
are included in the work. The results could be potentially useful to engineering seismologists who need to evaluate and better
understand the merits of this type of filtering for strong-motion data processing. 相似文献
85.
86.
The results of geological research show that those phenomena such as surface geology,geomorphology,deep geophysical field,and time-space distribution of seismicities can be usedas the main seismogeological indicators to identify the newly-generated seismic rupture zone(NSRZ).According to their formation and evolution process,the NSRZs can be divided intothree types:pre-rupture-isolated,quasi-rupture-discontinuous and major-rupture-connected.In a pre-rupture-isolated NSRZ,the seismicity is dominated by medium-small earthquakes.In a quasi-rupture-discontinuous NSRZ,the frequency and intensity of strong earthquakesincrease and there may even be the largest earthquake to occur.A major-rupture-connectedNSRZ is the segment where rupture has entered the mature stage;in such a zone,theintensity and duration of seismic activity depend on the constitutive condition and regionalstress field in the zone. 相似文献
87.
Gerd Bürger 《水文研究》2017,31(22):4039-4042
A main obstacle to trend detection in time series occurs when they are autocorrelated. By reducing the effective sample size of a series, autocorrelation leads to decreased trend significance. Numerous recipes attempt to mitigate the effect of autocorrelation, either by adjusting for the reduced effective sample size or by removing the autocorrelated components of a series. This short note deals with the latter, also called prewhitening (PW). It is known that removal of autocorrelation also removes part of the trend, which may affect the signal‐to‐noise ratio. Two popular methods have dealt with this problem, the trend‐free prewhitening (TFPW) and the iterative prewhitening. Although it is generally accepted that both methods reduce the adverse effects of PW on the trend magnitude, corresponding effects on statistical significance have not been clearly stated for TFPW. Using a Monte Carlo approach, it is demonstrated that both methods entail quite different Type‐I error rates. The iterative prewhitening produces rates that are generally close to the nominal significance level. The TFPW, however, shows very high Type‐I error rates with increasing autocorrelation. The corresponding rate of false trend detections is unacceptable for applications, so that published trends based on TFPW need to be reassessed. 相似文献
88.
89.
90.