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   73篇
  免费   11篇
  国内免费   40篇
测绘学   5篇
大气科学   18篇
地球物理   22篇
地质学   35篇
海洋学   20篇
天文学   2篇
综合类   6篇
自然地理   16篇
  2023年   1篇
  2022年   5篇
  2021年   2篇
  2020年   1篇
  2019年   1篇
  2018年   5篇
  2017年   1篇
  2016年   1篇
  2015年   2篇
  2014年   2篇
  2013年   10篇
  2012年   2篇
  2011年   6篇
  2010年   2篇
  2009年   4篇
  2008年   4篇
  2007年   5篇
  2006年   2篇
  2005年   7篇
  2004年   9篇
  2003年   6篇
  2002年   6篇
  2001年   2篇
  2000年   4篇
  1999年   2篇
  1998年   3篇
  1997年   1篇
  1996年   2篇
  1995年   3篇
  1993年   1篇
  1991年   1篇
  1990年   2篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1983年   1篇
  1960年   1篇
  1937年   1篇
  1933年   2篇
  1931年   1篇
  1927年   3篇
  1926年   2篇
  1924年   2篇
  1923年   2篇
排序方式: 共有124条查询结果,搜索用时 109 毫秒
31.
An examination of the locational characteristics of intended foreign equity joint venture (EJV) investment in China during the period 1979 to 1985 indicates that foreign EJV investment was highly concentrated in the coastal region, in the more developed areas of the provinces, and in large cities. The locational characteristics, however, differed between economic sectors and between countries of origin of investment. Although foreign EJV investment became spatially more dispersed through time, the impacts on the development of inland regions and backward areas in China remained limited.  相似文献   
32.
33.
在新冠肺炎疫情期间,线上教学大规模开展,相关线上教学问题逐渐成为研究热点。传统的测绘地理类课程的教学方式主要是上课时以老师传授知识为主,课后以学生完成作业为辅的方式进行。但是,这种教学方式比较单一,并且在科学化考核和促进学生学习主动性等方面存在诸多问题。然而,线上网络课程是通过互联网以电子设备为教学平台,具有不受教学时空限制、教学方法灵活多样和丰富学生的学习方式等优点。因此,对《城市地理资讯学》MOOC(massive online open courses)课程实施效果进行分析,为其他测绘地理类网络课程设计提供优化思路,同时为无法进行面授教学的特殊时期提供一种有效的教学方案。  相似文献   
34.
35.
Journal of Oceanology and Limnology - Hong Kong has a long historical record of harmful algal blooms (HABs). In the 1980s–1990s, HABs were mainly pollution-related and most of the events...  相似文献   
36.
Abstract

The detention storage in a drainage basin under the equilibrium condition is an important parameter in rainfall-runoff modelling. As this parameter is an efficient measure of the basin response to rainfall, it is commonly used as a basis of approximation of a complex basin by a simpler one. For flows on an overland plane, the equilibrium storage has also been used as a basis of determining the resistance coefficient of the overland surface. A formula is derived, based on the kinematic wave theory, for the equilibrium detention storage for a series of planes. For practical applications, the formula is further developed in terms of the Manning resistance coefficient. The derived formulae are all consistent with the published formulae for a single plane.  相似文献   
37.
Two gigantic individuals of the puzosiine ammonite genus Pachydesmoceras, from uppermost Middle and lower Upper Turonian strata in central and southwest Poland, are described and illustrated as the first examples of this genus to be recorded from Poland. Specific identification is problematic because of internal mould preservation and deformation to various extent; in addition, comparative material from other European localities is lacking. Representatives of Pachydesmoceras are typical of the Tethyan Realm; records from the European and Northwest Pacific provinces in the Boreal Realm are few. Both Polish specimens are referred to as P. cf. pachydiscoide Matsumoto.  相似文献   
38.
基于生物酶的固土技术在香港的应用研究   总被引:2,自引:0,他引:2  
传统加固土体的方法主要是通过在土中加入一定量的高性能掺合剂使之成为一种强度较高的复合土体,但这种方法需要较长的养护时间,且不经济。利用一种新型实用的生物酶固化技术,针对香港地区3种常见的海洋黏土、完全风化花岗岩和完全风化凝灰岩,开展了土体加固试验研究。试验结果表明,生物酶对海洋土的加固效果最好,强度增加最高可达20%,而生物酶对完全风化花岗岩的加固效果则不太理想,抗剪强度指标只有少许改变。此外,海洋土和完全风化凝灰岩的压缩性因为生物酶的作用反而有所增强。最后,从微观上分析了生物酶固土作用的本质,指出固土效果主要缘自于生物酶分子与土中的黏土矿物分子发生相互作用产生的胶结作用。  相似文献   
39.
针对长孔段漏涌地层及松散破碎等复杂地层,提出以泡沫泥浆或充气泥浆平衡地层压力的钻进方法,兼备护壁和防止冲洗液漏失的双重作用,实现连续堵漏和护壁,减少堵漏时间,有利于提高钻探效率,降低成本。对干旱缺水地区、全漏失地层钻探施工拓展了新的技术手段。  相似文献   
40.
This study presents the radar-based characteristics and formation environment of supercells spawned by the tornadic landfalling Typhoon Mujigae(2015)in October 2015.More than 100 supercells were identified within a 24-hour period around the time of the typhoon’s landfall,of which three were tornadic with a rotational intensity clearly stronger than those of non-tornadic supercells.The identified supercells were concentrated within a relatively small area in the northeast quadrant beyond 140 km from the typhoon center.These supercells were found more likely to form over flat topography and were difficult to maintain in mountainous regions.During the study period,more supercells formed offshore than onshore.The mesocyclones of the identified supercells were characterized by a small diameter generally less than 5 km and a shallow depth generally less than 4 km above ground level.An environmental analysis revealed that the northeast quadrant had the most favorable conditions for the genesis of supercell in this typhoon case.The nondimensional supercell composite parameter(SCP)and entraining-SCP(E-SCP)were effective in separating supercell from non-supercell environment.Even though the atmosphere in the typhoon’s northeast quadrant was characterized by an E-SCP/SCP value supportive of supercell organization,orography was an impeditive factor for the supercell development.These findings support the use of traditional parameters obtained from midlatitude supercells to assess the supercell potential in a tropical cyclone envelope.  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