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   131篇
  免费   14篇
  国内免费   15篇
测绘学   21篇
大气科学   9篇
地球物理   13篇
地质学   54篇
海洋学   10篇
天文学   3篇
综合类   4篇
自然地理   46篇
  2023年   1篇
  2022年   6篇
  2021年   2篇
  2020年   7篇
  2019年   7篇
  2018年   6篇
  2017年   8篇
  2016年   9篇
  2015年   6篇
  2014年   9篇
  2013年   7篇
  2012年   17篇
  2011年   7篇
  2010年   5篇
  2009年   2篇
  2008年   6篇
  2007年   7篇
  2006年   7篇
  2005年   5篇
  2004年   10篇
  2003年   5篇
  2002年   3篇
  2001年   2篇
  2000年   3篇
  1997年   3篇
  1996年   1篇
  1995年   4篇
  1994年   1篇
  1993年   3篇
  1985年   1篇
排序方式: 共有160条查询结果,搜索用时 29 毫秒
41.
张赤军  许厚泽 《物探与化探》2002,26(1):68-70,74
为改变西部干旱缺水,在西部大开发中,大规模、长尺度地兴修水利,如南水北调,将有必要进行。基于同一个水准面上高程相同的原则,本文强调在上述工程的设计施工时应该使用与位基数意义相同的力高高程。据计算,在纬度差为12°,高差相差的近2500m的同一条测线上,现行的高程与力高高程相差7m之多,这样大的偏差是不能忽略的。文中对高程测量中重力点的布设及重力内插的精度等也提出了新的看法。  相似文献   
42.
目前 ,已有 1 0架口径 8~ 1 0m的地面大望远镜建成并投入科学观测。在近红外波段 ,自适应光学和干涉术已在大望远镜上获得成功。Hubble空间望远镜发射至今已逾 1 2年。为了研究早期宇宙 ,探测类地行星等 ,2 0 0 2年 9月NASA已与TWR公司签约 ,研制口径≥ 6m的下一代空间望远镜JWST ,计划2 0 1 0年发射。许多口径 30~ 1 0 0m的地面未来巨型望远镜FGT项目已经提出。本报告 ,也介绍了我国正在研制或预研中的三个大项目 :LAMOST、FAST和SST ,这些项目虽较小 ,但完成后都会对天文学的一个方面作出有份量的贡献。最后 ,报告人建议我国参与到与国外合作研制FGT或NGST的工作中 ,特别强调要有天文学家和工程专家参与进去  相似文献   
43.
In recent literature, projects are mostly seen as an efficient form of organization which is particularly suited for mastering tasks of high complexity and creativity and adapting to changing economic and institutional conditions. This paper challenges the assumption that inter-firm projects are persistent organizational arrangements of production in the advertising industry and presents a novel argument about the potential threats to forms of project organization in crisis situations. By exploring the cases of Frankfurt/Main and Leipzig (East Germany), we show that the organization of production is substantially affected by periods of economic crisis or political transformation. We demonstrate that inter-firm projects might be replaced by more durable organizational configurations or might not be viewed as viable options in situations of severe rupture. This applies particularly to the cooperative arrangements in the creative process and leads to an organizational paradox. Although creativity is often a pivotal force to gain competitive advantage, the advertising agencies respond to the challenges of crises by reducing cooperation with external partners to a minimum and sometimes fully rely on in-house personnel. This threatens the potential of the respective firms to develop innovative and creative ideas which would enable the firms to acquire new customers and market segments. Instead of trying to overcome crises by focusing on their creative capabilities, many advertising agencies develop a cost-cutting strategy and rely on more durable network-forms of organization instead of inter-firm projects.  相似文献   
44.
软岩浅埋隧道施工工法比选   总被引:2,自引:0,他引:2  
王伟锋  毕俊丽 《岩土力学》2007,28(Z1):430-436
目前在高速公路软岩浅埋隧道施工中均不同程度地出现了围岩坍塌、地表产生大面积沉降等问题。广福隧道某浅埋段,地质条件复杂,断面大、岩性差,受构造影响比较严重,而且顶板厚度比较薄,易发生坍塌、冒顶现象。为确保浅埋段隧道的施工安全,尽量减少隧道开挖引起的地层沉降和围岩变形,采用FLAC3D对4种施工工法全断面法、短台阶法、单侧壁导坑法和双侧壁导坑法进行模拟,分析了4种工法下地表沉降、隧道围岩周边位移和塑性区的变化特点,选出一种技术可行、经济合理的施工工法,得出一些有意义的结论。  相似文献   
45.
吴应科 《中国岩溶》2004,23(1):63-73
桂林“三世”工程指申报世界文化与自然遗产、申报世界岩溶地质公园、创建桂林世界喀斯特博览园三项工程。桂林“三世”工程申报有着优良厚实的基础,它将给创建桂林国际旅游名城带来新的契机,成为有效保护桂林岩溶山水景观资源和打造“桂林特色旅游航母”、做大做强广西旅游的龙头;同时也是全面建设小康社会的需要。“三世”工程具有开创性、全局性、前瞻性的重要战略意义和现实意义。   相似文献   
46.
This article analyzes the collective action frames used by members of Chilean nongovernmental organizations (NGOs) while engaging in policy advocacy. The focus is a large-scale dam project along the Bío Bío River that generated controversy for more than a decade due to its impact on the environment and indigenous communities. It is argued that the environmental advocates’ reliance on certain frames hindered their ability to influence policymaking. They framed the neoliberal model as “pathologically” growth centered, unjust, and destructive. Additionally, advocates were besieged by counter frames portraying them as foes of modernization. Though compelling, the groups’ frames set them on a collision course with the policymaking establishment. In contrast, members of groups advocating for children used more effective discursive strategies and achieved a greater presence in policy debates. These arguments are supported with qualitative data collected primarily through interviews with NGO members, textual analysis of their documents, and news content analysis.  相似文献   
47.
地质勘查预算标准是安排省地勘项目的主要依据,预算编制水平直接影响财政资金的分配和地勘项目的管理。从预算编制的准备工作、技术条件、表式分类、工作手段及费用指标解释、编制说明等各方面逐一进行了分析和阐述,具有一定的实用性和可操作性,对于提高和完善预算编制工作,具有促进和推动作用。  相似文献   
48.
The pace of the international Square Kilometre Array (SKA) project is accelerating, with major concept reviews recently completed and a number of technology demonstrators well underway. First-round submissions to host the telescope were lodged by six countries. The SKA timeline currently shows a site decision in 2006, and one or more technology concepts chosen in 2008. The telescope is expected to be operational, in various phases, in the period 2015–2020. This paper gives a status review of the project, and outlines engineering concept development and demonstration projects.  相似文献   
49.
王淑芳  孙士宽  叶帅 《地理研究》2022,41(7):1814-1825
“一带一路”倡议提出以来,中国海外项目投资的广度、深度及力度都在不断拓展。凑组理论将所有事物视为复杂关系的动态演变,因而从发展过程及成员关系的角度探究不同海外投资项目的凑组模式,能解构项目凑组中的复杂性并减少不确定性,对于提高项目的风险规避能力、运营能力和盈利能力具有十分重要的意义。基于凑组理论,本文构建中国海外投资项目凑组的理论框架,并以中老铁路为例解析凑组模式。研究表明:① 海外投资项目可以通过技术、产业和市场等价值关联进行凑组,因而中国企业的海外投资可以采用“以一带多,核心集聚”的方式。② 海外投资项目的类型和领域越多样越广泛,项目凑组越完整越稳定。③ 凑组所形成的空间形态取决于项目的空间分布与项目间的价值关系,中老铁路表现为“走廊”式空间形态。④ 中老铁路具备形成项目凑组的条件,但后期技术需求的不确定及相关产业下游项目投资的缺乏,使中老铁路建设带来的延伸市场缺乏项目支撑。  相似文献   
50.
《Climate Policy》2013,13(3):242-254
The Clean Development Mechanism (CDM) under the Kyoto Protocol allows industrialized countries to use credits from greenhouse gas (GHG) abatement projects in developing countries. A key requirement of the CDM is that the emission reductions be real, measurable and additional. This article evaluates how the additionality of CDM projects has been assessed in practice. The analysis is mainly based on a systematic evaluation of 93 registered CDM projects and comes to the conclusion that the current tools for demonstrating additionality are in need of substantial improvement. In particular, the application of the barrier analysis is highly subjective and difficult to validate in an objective and transparent manner. Key assumptions regarding additionality are often not substantiated with credible, documented evidence. In a considerable number of cases it is questionable whether the emission reductions are actually additional. Based on these findings, practical recommendations for improving the assessment of additionality are provided.  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