首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5599篇
  免费   647篇
  国内免费   1147篇
测绘学   1629篇
大气科学   42篇
地球物理   319篇
地质学   4322篇
海洋学   300篇
天文学   40篇
综合类   332篇
自然地理   409篇
  2024年   25篇
  2023年   75篇
  2022年   204篇
  2021年   219篇
  2020年   250篇
  2019年   284篇
  2018年   203篇
  2017年   323篇
  2016年   359篇
  2015年   295篇
  2014年   410篇
  2013年   421篇
  2012年   417篇
  2011年   350篇
  2010年   263篇
  2009年   230篇
  2008年   332篇
  2007年   314篇
  2006年   283篇
  2005年   299篇
  2004年   233篇
  2003年   215篇
  2002年   187篇
  2001年   163篇
  2000年   157篇
  1999年   133篇
  1998年   147篇
  1997年   117篇
  1996年   93篇
  1995年   68篇
  1994年   52篇
  1993年   53篇
  1992年   50篇
  1991年   26篇
  1990年   34篇
  1989年   11篇
  1988年   20篇
  1987年   16篇
  1986年   18篇
  1985年   9篇
  1984年   5篇
  1982年   4篇
  1980年   5篇
  1979年   3篇
  1977年   2篇
  1976年   1篇
  1975年   1篇
  1973年   5篇
  1972年   4篇
  1971年   3篇
排序方式: 共有7393条查询结果,搜索用时 15 毫秒
41.
In order to examine the applicability of ground‐shaking mapping techniques to a near‐field earthquake, a peak ground velocity map of the 1995 Hyogo‐ken Nanbu, Japan earthquake computed from seismic zoning methods that consider the effects of geological conditions is compared with the actual observed intensity map. When computing the ground‐shaking map, the site amplification at each site is calculated in terms of the average shear‐wave velocity of the ground estimated from the corresponding geomorphological conditions. This map shows a relatively good agreement with the observed intensity map. However, the computations provide smaller values for certain disastrous areas of the earthquake, where the effects on ground motion of a deep, irregular underground structure have been reported. The effect of such structures on site response is examined implementing 2D FEM analyses, thereby being also incorporated into the method. Results considering the effect of the irregular underground structure show better agreement with the observed intensity map. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
42.
应用等效纬度-海拔模型进行地温及多年冻土制图   总被引:2,自引:2,他引:2  
This research presents a method for permafrost mapping in discontinuous permafrost regions based on equivalent latitude/elevation concept in interior Alaska. In winter months, study site has a strong temperature inversion in air up to 700 m elevation. Air temperature data and the effects of slope, aspect and elevation were used to create an equivalent latitude/elevation model. This model was well correlated with mean annual surface temperature (0.79). In this watershed, the thawing index (It≈1 400 ℃*days) at the ground surface and snow depth do not vary greatly from south facing to north facing slopes. The primary controlled factor that determines the mean annual surface temperature was the winter surface temperature. The permafrost stability is effectively controlled by the freezing index. We determined 37.5% of Caribou-Poker Creeks Research Watershed has unstable or thawing permafrost. At least 2.1% of the permafrost in this watershed may have disappeared in the last 90 years due to climate warming. This method makes it possible to evaluate the permafrost stability in the present, past and future.  相似文献   
43.
非常规综合物化探方法油气预测研究中存在的主要问题为:缺乏系统与综合的基础性理论研究,异常形成的机理还不十分清楚,在参数的优化组合及异常的求取上尚有诸多不足。针对后一种情况,选择松辽盆地东岭构造作为实验区进行了有益的探索。选取低能吸附烃、放射性测氡及土壤热释光三类参数进行了优化组合,分别计算了综合指标MAE与MAC及组合熵,然后对各值采用泛克里格法求取异常,取得了良好的效果。下一步研究应从异常形成的机理入手,建立三维非常规综合物化探油气预测模式,以提高油气预测成功率。  相似文献   
44.
本文以 1∶5万里庄幅为例 ,阐述了运用GIS系统对区调过程中各种资料的处理与编辑方法 ,并介绍了数字制图方法及工艺流程 ,提出了GIS系统在 1∶5万区调工作中的应用前景  相似文献   
45.
According to the principle of the eruption of debris flows, the new torrent classification techniques are brought forward. The torrent there can be divided into 4 types such as the debris flow torrent with high destructive strength, the debris flow torrent, high sand-carrying capacity flush flood torrent and common flush flood by the techniques. In this paper, the classification indices system and the quantitative rating methods are presented. Based on torrent classification, debris flow torrent hazard zone mapping techniques by which the debris flow disaster early-warning object can be ascertained accurately are identified. The key techniques of building the debris flow disaster neural network (NN)real time forecasting model are given detailed explanations in this paper, including the determination of neural node at the input layer, the output layer and the implicit layer, the construction of knowledge source and the initial weight value and so on. With this technique, the debris flow disaster real-time forecasting neural network model is built according to the rainfall features of the historical debris flow disasters, which includes multiple rain factors such as rainfall of the disaster day, the rainfall of 15 days before the disaster day, the maximal rate of rainfall in one hour and ten minutes. It can forecast the probability, critical rainfall of eruption of the debris flows, through the real-time rainfall monitoring or weather forecasting. Based on the torrent classification and hazard zone mapping, combined with rainfall monitoring in the rainy season and real-time forecasting models, the debris flow disaster early-warning system is built. In this system, the GIS technique, the advanced international software and hardware are applied, which makes the system′s performance steady with good expansibility. The system is a visual information system that serves management and decision-making, which can facilitate timely inspect of the variation of the torrent type and hazardous zone, the torrent management, the early-warning of disasters and the disaster reduction and prevention.  相似文献   
46.
This paper presents a statistical approach to study the spatial relationship between landslides and their causative factors at the regional level. The approach is based on digital databases, and incorporates such methods as statistics, spatial pattern analysis, and interactive mapping. Firstly, the authors propose an object-oriented conceptual model for describing a landslide event, and a combined database of landslides and environmental factors is constructed by integrating the various databases within such a conceptual framework. The statistical histogram, spatial overlay, and dynamic mapping methods are linked together to interactively evaluate the spatial pattern of the relationship between landslides and their causative factors. A case study of an extreme event in 1993 on Lantau Island indicates that rainfall intensity and the migration of the center of the rainstorm greatly influence the occurrence of landslides on Lantau Island. A regional difference in the relationship between landslides and topography is identified. Most of the landslides in the middle and western parts of the island occurred on slopes with slope angles of 25–35°, while in the eastern part, the corresponding range is 30–35°. Overlaying landslide data with land cover reveals that a large number of landslides occurred in the bareland and shrub-covered area, and in the transition zones between different vegetation types. The proposed approach can be used not only to analyze the general characteristics of such a relationship, but also to depict its spatial distribution and variation, thereby providing a sound basis for regional landslide prediction.  相似文献   
47.
盐山-庆云地区具多凸多凹、地质条件复杂、多向供油(气)的特点。油气化探异常发育不平衡,具有成带分布、局部富集的特征。西部主要的轻烃(CH4)异常强,东部则是重烃(C2H6、C3H8)异常最发育,由西向东轻烃逐渐下降,重烃不断增加,非烃指标(Hg、△C)异常与重烃异常基本相拟,Ks、Fe^2 异常规律不明显。根据烃类指标的分带性,轻、重烃异常规律和富集特征划分为气显示带,油显示带和油气显示带。中部地区的即油气显示带是油气最有远景的地段。  相似文献   
48.
GRAPHER、Surfer32与CorelDRAW1O在物探成图中的应用   总被引:1,自引:0,他引:1  
用GRAPHER、Surfer32软件作出给定数据的曲线图、平剖图、平面等值线图和立体曲面图后,再用CorelDRAW10来编辑,可快速做出一张满意而又少占存储空间的图件。  相似文献   
49.
我国数字填图技术研究现状与发展趋势   总被引:5,自引:0,他引:5  
李超岭 《新疆地质》2003,21(Z1):1-6
数字填图系统(RGMAP)是中国地质调查局研发的,用来进行区域地质调查工作的专业软件.通过4幅150000和10幅1250000数字填图试点应用,使数字填图系统已臻于完善,为中国地质调查局全面推广数字填图方法奠定了良好的基础.野外数据采集数字化,使得地质调查数据实现了一体化的描述、组织、综合、管理及资源的统一描述、再现和集成.建立个性化的多用户,多目标的社会化服务体系,是今后地质调查主流程信息化的主要任务和目标.  相似文献   
50.
在原子荧光光谱法中,通过改进地球化学样品的分解条件,预还原条件及测定条件,使砷、锑和汞能在同一介质中测定,而且实现了砷与汞的双道同时测定。方法的检测出限、准确度及精密度均能达到行业要求。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号