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   10162篇
  免费   1481篇
  国内免费   1834篇
测绘学   1278篇
大气科学   477篇
地球物理   997篇
地质学   6658篇
海洋学   1506篇
天文学   20篇
综合类   916篇
自然地理   1625篇
  2024年   38篇
  2023年   103篇
  2022年   295篇
  2021年   334篇
  2020年   364篇
  2019年   361篇
  2018年   291篇
  2017年   402篇
  2016年   368篇
  2015年   451篇
  2014年   606篇
  2013年   652篇
  2012年   584篇
  2011年   667篇
  2010年   600篇
  2009年   600篇
  2008年   645篇
  2007年   695篇
  2006年   694篇
  2005年   561篇
  2004年   503篇
  2003年   432篇
  2002年   440篇
  2001年   454篇
  2000年   351篇
  1999年   342篇
  1998年   252篇
  1997年   224篇
  1996年   178篇
  1995年   176篇
  1994年   189篇
  1993年   137篇
  1992年   118篇
  1991年   70篇
  1990年   62篇
  1989年   56篇
  1988年   45篇
  1987年   42篇
  1986年   25篇
  1985年   19篇
  1984年   15篇
  1983年   7篇
  1982年   6篇
  1981年   3篇
  1980年   3篇
  1978年   5篇
  1977年   10篇
  1973年   1篇
  1971年   1篇
排序方式: 共有10000条查询结果,搜索用时 453 毫秒
141.
贵州煤矿地质工程咨询与地质环境监测中心,由于市场定位准确,加强经营管理,树立品牌意识,尊重人才,加大人才培养力度,积极推进人事制度和分配制度改革,完善激励约束机制,使单位经济效益稳步上升,职工收入不断提高。  相似文献   
142.
抚顺矿区城市下压煤面积6km^2,煤炭储量23901.5万t。通过对矿区地质特征、煤储层特征分析.认为区内煤层气含量高(9.81~24.53m^3/t),煤层中大空隙多,透气性好,渗透率较高(0.24~3.60mD)。煤层直接顶板为厚100m左右的致密油页岩,底板为泥岩、凝灰岩,具有良好的封闭条件。根据矿区多年测试资料,采用容积法得出区内煤层气资源量为30.53亿m^3。综合开发煤层气资源符合东北老矿区的实际,其将为复苏东北重工业基地提供有效的洁净能源。  相似文献   
143.
目前山区地震测量施工主要的困难体现在山区放样难、内业数据处理复杂、测量成果无法进行异常检查等方面,其严重影响后续资料处理和解释质量。针对以上难点,利用AUTOCAD为平台,开发了一套物探测量数据处理系统。该系统具有展点、点内插、绘制测线剖面图、管理测点信息、打印成果报表等功能,实现了地震勘探测量数据的快速处理及有效检核.提高了野外测量放样的施工效率和数据的准确度。另外其图层管理及系统辅助功能,还可为地震勘探施工设计提供参考。  相似文献   
144.
网络服务是煤炭地质档案业务发展的必由之路,为了解决在公共网络传输过程中的安全问题,本文介绍了一种虚拟专用网络技术,通过分析其应用于煤炭地质档案网络服务中的优势,为行业内外部的信息共享提供了一个新的思路。  相似文献   
145.
谈测绘项目管理   总被引:4,自引:0,他引:4  
本文从工程项目管理学的观点,结合测绘项目的特殊性,阐述了测绘项目管理的基本方法和要求,内容包括测绘项目组织与程序、计划、质量、进度与合同管理等。  相似文献   
146.
通过对支援柬埔寨、几内亚桩基工程的施工实践,总结出在境外工程项目的管理中,要制定相应的管理制度与突发事件的应急预案,在施工过程中要注意政局变化,加强卫生疾病的防治,进行必要的物质储备和规避风险等注意事项及解决方法.对地勘单位拓展海外市场提出了建设性意见,具有一定的借鉴意义。  相似文献   
147.
The present study deals with processing and interpreting the potential gravity and magnetic data in order to locate promising sites for metallic mineral occurrences in the basement rocks of South Sinai. Two promising sites were anticipated by combining the geophysical results and the available geological information. Each site was profiled and interpreted to the nearly approximated subsurface feature model, and the geometrical parameters of the expected subsurface structures may form mineralized bodies such as depth, thickness, width, dipping, density contrast, and magnetic susceptibility contrast could be delineated. Detailed ground Very Low Frequency (VLF) and Vertical Magnetic Gradient (VMG) methods were carried out in the site A2, eight VLF and VMG anomalies were determined, and their depths were calculated.  相似文献   
148.
The Bureau of Economic Analysis (BEA), U.S. Department of Commerce, in keeping with broad international efforts to green national gross domestic product (GDP) accounts, has attempted to create satellite accounts for mineral depletion. The present paper criticizes the BEA's unit rent measure of resource depletion, which is based upon Hotelling's pure theory of exhaustion. Following a thorough criticism of Hotelling's theory as a real-world model of mineral prices, practical issues related to the treatment of recycling, exploration, definition of reserves/resources, and their valuation/exploitation are introduced. For crude oil and natural gas and the nonfuel minerals, specific application problems of joint products and residuals complicate BEA's assumptions and efforts.  相似文献   
149.
Southeast South Australia has large reserves of potable groundwater, generally close to the surface. European settlement has had a major impact on groundwater quality due to the presence of extensive karst in the unconfined aquifer. Historically, industries such as cheese factories were often sited close to karst features (e.g. caves and sinkholes) because they provided a convenient means of waste disposal. Although most have long since closed, they have left a legacy of pollution plumes of varying sizes. In Mount Gambier, the main regional centre, the presence of both exposed and subterranean karst features provided a perfect system for the disposal of stormwater. Prior to the provision of a sewerage system within Mount Gambier, all toilet and household wastewaters were disposed to ground. These activities and the subsequent problems that began emerging in the 1960s have led to a concerted effort over the last 20 years to change the philosophy of waste disposal and to generate an understanding and responsibility by those who live in the region and depend on groundwater for the major part of their water supply. Mount Gambier's water supply comes from the Blue Lake. Groundwater inflow from a highly karstic Tertiary limestone aquifer provides 90% of the recharge to the Blue Lake. The lake is a high-value resource in a high-risk environment and in order to minimize this risk, a water-quality management plan for the lake is currently being developed.  相似文献   
150.
Wang  Yutian  Tan  Bingqi  Wang  Yifeng  Wu  Jiangtao 《Natural Resources Research》1994,3(4):284-294
We propose an information-structure-analysis (ISA) method to quantify the correlations between quantitative and qualitative variables as well as within each type of variable. This method is applied to the evaluation of mineral resources in the western Zheijiang Province of China. The district contains a number of silver-bearing Fe–Cu–Pb–Zn mineral deposits near igneous complexes and FeCuPbZn zones away from the complexes. Silver anomalies occur not only in the known Fe–Cu–Zn–Pb deposits, but also in the country rock, suggesting the possible existence of silver deposits far from the igneous complexes.The tonnage distribution of silver is modeled by Monte Carlo simulation. This simulation is conducted on the basis of the correlations between silver (Ag) and lead (Pb), since no known data on silver is available. The known tonnage distribution of lead in 11 control cells was used to approximate the tonnage distribution of silver in the Monte Carlo simulation. With ISA and Monte Carlo methods, the total amount of potential polymetallic resources in 49 cells in the western Zhejiang Provice is predicted. Significantly, a deposit with about 24 tonnes of silver has been found within our exploration target area.  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