全文获取类型
| 收费全文 | 100篇 |
| 免费 | 28篇 |
| 国内免费 | 10篇 |
专业分类
| 测绘学 | 13篇 |
| 大气科学 | 8篇 |
| 地球物理 | 34篇 |
| 地质学 | 45篇 |
| 海洋学 | 12篇 |
| 天文学 | 11篇 |
| 综合类 | 3篇 |
| 自然地理 | 12篇 |
出版年
| 2022年 | 3篇 |
| 2021年 | 4篇 |
| 2020年 | 3篇 |
| 2019年 | 3篇 |
| 2018年 | 2篇 |
| 2017年 | 2篇 |
| 2016年 | 5篇 |
| 2015年 | 10篇 |
| 2014年 | 11篇 |
| 2013年 | 2篇 |
| 2012年 | 25篇 |
| 2011年 | 12篇 |
| 2010年 | 3篇 |
| 2009年 | 17篇 |
| 2008年 | 4篇 |
| 2007年 | 5篇 |
| 2005年 | 3篇 |
| 2004年 | 4篇 |
| 2003年 | 3篇 |
| 2002年 | 6篇 |
| 2001年 | 1篇 |
| 2000年 | 3篇 |
| 1999年 | 3篇 |
| 1998年 | 1篇 |
| 1997年 | 2篇 |
| 1996年 | 1篇 |
排序方式： 共有138条查询结果，搜索用时 15 毫秒
1.
2.
A new 3-D model REGINA (REGIonal high resolutioN Air pollution model) is under development at the National Environmental Research Institute (NERI). The model is based on pieces from several models developed over the last decades at NERI. The aim of the work is to develop a nested model which can operate with very high resolution in both space and time. To fulfill this aim the choice and implementation of accurate numerical methods is crucial. The model will be applied for studying air pollution phenomena (both monitoring, forecasting and scenarios) over Denmark. The present paper is focussed on the modification, implementation and testing of a numerical method for treating the horizontal advection in the model as well as the implementation of two-way nesting techniques. The horizontal transport in the model is solved using an accurate space derivative algorithm. This method is traditionally implemented with periodic boundary conditions, however, this is not an option for nested modelling. A new method for calculating non-periodic boundary conditions has been developed in order to overcome this problem. Extensive testing of the numerical solution of the advection and the coupling of the solution of advection and chemistry in the model using Molenkamp–Crowley rotation tests have been carried out. The results show that the model with the current implementation of numerical methods is suitable for calculating air pollution levels with high resolution. 相似文献
3.
In this paper seven of the ten Water Control Zones (WCZs) in Hong Kong′s coastal waters with monthly or bi-weekly sampling data of 17 parameters collected at 37 monitoring stations from 1988 to 1999 were selected to analyze the spatial and temporal variations of chlorophyll-a and its influencing factors. Cluster analysis was employed to group the monitoring stations based on the structure of the data set. Multiple step regression was employed to determine the significant influencing factors of chlorophyll-a level. The results suggest that all the monitoring stations could be grouped into two clusters. Cluster I with frequent red tide incidents comprises two WCZs which aresemi-enclosed bays. Cluster II with less red tide occurrence comprises the other five WCZs in an estuarine environment in the west. For both clusters, the organic contents indicator, BOD5, was a common significant influencing factor of the chlorophyll-a level. Nitrogen and light penetration condition related to turbidity, total volatile solids and suspended solids had more influence on the cholophyll-a level in Cluster I than in Cluster II, while phosphorus and oceanographic conditions associated with salinity, temperature, dissolved oxygen and pH were more important in Cluster II than in Cluster 1. Generally, there was a higher average chlorophyll-a level in winter and autumn in a year.The chlorophyll-a level was much higher in Cluster I than in Cluster II among all seasons. Although the chlorophyll-a concentration had great variations from place to place in Hong Kong′s coastal waters, it seemed to have a common long term fluctuation period of 8-10 years with a high-low-high variation in the period in the whole region, which might be influenced by other factors of global scale. 相似文献
4.
探讨了４５Ｍｎ２钻杆接头的各种热处理工艺降综合机械性能，应用断裂力学优选最佳热处理工艺，并已投入生产。 相似文献
5.
460铀-钼矿床控矿因素及矿床成因探讨 总被引：3，自引：2，他引：3
460矿床是上世纪80年代在冀北沽源中生代火山断陷盆地西部发现的大型铀-钼矿床。在对该矿床野外实地调研的基础上，结合矿床地质详查和矿床专题科研报告的综合分析，对矿床的控矿因素进行了系统总结。研究结果表明，矿床受NE向断裂（F45）和火山构造的联合控制；火山活动晚期沿断裂和中心式火山机构侵入的次流纹斑岩体是矿床定位的决定性因素；铀-钼矿化主要产于次流纹斑岩体产状变异部位或接触带附近；容矿构造为次流纹斑岩体接触带构造、隐爆角砾岩和J3z^3-5川层流纹岩中的层间裂隙带。研究认为，铀矿化受断裂构造、火山机构、岩浆活动、热液蚀变等作用的复合控制，其中火山口-火山通道相的次流纹斑岩体是主要的控矿因素。 相似文献
6.
鄂尔多斯盆地西缘惠安堡地区铀成矿特点 总被引：2，自引：1，他引：1
典型层间氧化带砂岩型铀矿产出于次造山带构造背景。惠安堡地区处于鄂尔多斯盆地西缘褶断带马家滩断褶带,传统理论认为这里不利于后生铀成矿作用的进行,但近几年的找矿实践证明该断褶带的铀成矿作用既有典型层间氧化带砂岩型铀矿的一些特点,也有自己的特殊性。该区的地层倾角较大,砂体厚度也较大;地下水近源、短途、双向径流,形成多个复杂的局部水动力系统;沿背斜东、西两翼发育的层间氧化带具有层数多、双向发育、期次多、氧化深度大、沿倾向延伸较短、纵横方向厚度变化快、连续性较差、地球化学分带不明显、水解蚀变作用弱等特点;铀矿化具有层数多、期次多、品位较低、厚度较小、矿化分散、深度较大、矿化主要受层间氧化带翼部控制、前锋成矿较弱、矿化纵横连续性差、矿后改造较强等特征。 相似文献
7.
8.
9.
10.