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   1285篇
  免费   179篇
  国内免费   205篇
测绘学   133篇
大气科学   221篇
地球物理   345篇
地质学   371篇
海洋学   225篇
天文学   23篇
综合类   74篇
自然地理   277篇
  2024年   4篇
  2023年   17篇
  2022年   47篇
  2021年   42篇
  2020年   49篇
  2019年   67篇
  2018年   45篇
  2017年   70篇
  2016年   62篇
  2015年   64篇
  2014年   110篇
  2013年   105篇
  2012年   73篇
  2011年   96篇
  2010年   61篇
  2009年   87篇
  2008年   75篇
  2007年   100篇
  2006年   77篇
  2005年   55篇
  2004年   39篇
  2003年   48篇
  2002年   41篇
  2001年   40篇
  2000年   30篇
  1999年   34篇
  1998年   18篇
  1997年   24篇
  1996年   17篇
  1995年   17篇
  1994年   12篇
  1993年   11篇
  1992年   6篇
  1991年   6篇
  1990年   3篇
  1989年   1篇
  1988年   3篇
  1987年   5篇
  1986年   3篇
  1985年   1篇
  1983年   1篇
  1982年   2篇
  1973年   1篇
排序方式: 共有1669条查询结果,搜索用时 15 毫秒
361.
Lofer cyclothems of the Alpine Upper Triassic have many features in common with Holocene sediments of Florida Bay. The modal ‘complete’ Lofer cycle is essentially symmetrical, having a deepening and shoaling phase, as does the cycle-in-progress in Florida Bay. Lateral discontinuity and thickness variations within members of the Lofer cyclothems indicate syn-depositional relief, possibly in the form of mud banks, the signature feature of Florida Bay sedimentation. Spatial and temporal dimensions, although poorly constrained, appear comparable. Analogous depositional textures, biota and sedimentary structures, while not unique to either environment, strengthen the inferences that can be made about the Triassic depositional environment and regarding future evolution of the modern environment. The striking similarities between the Holocene icehouse sediments and the Late Triassic greenhouse deposits suggest that sedimentation patterns at the scale of individual cycles or parasequences may be largely independent of the global climate regime.  相似文献   
362.
Almost every country requires some form of environmental licensing prior to the inception of development projects that may affect the integrity of the environment and its social context. We developed a new conceptual and methodological model to instruct the assessment of the potential impacts posed by proposed projects. Susceptibility to Human Interventions for Environmental Licensing Determination (SHIELD) includes a novel geomorphological interpretation of the Environmental Impact Assessment (EIA). It considers the impact of human interventions on geomorphological processes and landscape functioning in the context of the entire ecosystem, going further than the classical concept of vulnerability. Estimated susceptibility of the site informs the screening stage, allowing local conditions to help define the criteria used in the process. Similarly, the level of detail of the environmental baseline is scoped by considering the degree of disturbance of natural processes posed by human intervention. Testing this geomorphological susceptibility model on different kinds of environments would allow shifting the environmental licensing practices from the prevailing anthropocentric and static conception of the environment towards an Ecosystem Approach. SHIELD addresses the need to improve the screening and scoping stages that form the basis of the rest of any EIA. SHIELD introduces several innovations to EIA including the incorporation of fuzzy logic, a preassembled database of contributions form experts, and a shifting of emphasis from the type of proposed intervention to the type of environment and its relative susceptibility.  相似文献   
363.
使用IBIS-L系统对大型水电站边坡长时间的监测数据进行分析和处理,并与TM30全站仪进行变形监测精度对比。试验表明,IBIS系统可得到在雷达视线方向优于mm级精度的形变结果,优于TM30全站仪,可以实现高分辨率、高精度、实时的大型水电站边坡长时间变形监测。  相似文献   
364.
?????????????????????????????????????????????????????3?????棬??????????????????????????????3????????????????????????GPS/?????????????4?????????????“???????100 km????£???????澫??±1 cm”????????|??????????????????????????|GOCE????????Ч???????????????????????????????  相似文献   
365.
The international compensation regime for tanker oil pollution has been successful in providing adequate and prompt compensation to pollution victims in its member states. Nevertheless, the attitudes of different countries toward acceptance of this regime have varied considerably. This paper aims to explain three main factors in the acceptance of the regime, including: (1) The level of economic development; (2) the risk of exposure to tanker oil spills; and (3) the financial burden associated with adherence to the International Oil Pollution Compensation Fund (IOPC). Using both fuzzy-set Qualitative Comparative Analysis and an Ordered Probit model, this study found two patterns causing upper-middle and high income countries to have a high acceptance level: (a) Those facing a medium risk of oil spills and having a low financial burden; and (b) those facing a high risk of oil spills. The study reveals that, for a country with a high risk of exposure to tanker oil spills, such as China, with its improvement in economic status it is far better for it to join the IOPC Fund, so as to provide better protection both for potential pollution victims and for the marine environment. The results of this study can also be applied to other countries that are considering whether or not to accept the international compensation regime for tanker oil pollution.  相似文献   
366.
Recently, a human rights approach has been center-staged within fisheries governance as a response to the limits of private property rights in reducing insecurity and vulnerability among fishers and fishing communities. Despite its growing adoption in international legal frameworks and among civil society organizations, the conceptual pitfalls of the human rights approach to fisheries (i.e., its neoliberal tendencies and the neglect of collective rights and social duties) raised by critical scholarship remain largely unsettled, leading to practical concerns about whether such a framework will ultimately benefit fishers on the ground. To further contribute to the debate, this article presents a nuanced discussion of the human rights perspective by introducing the concept of human dignity. Specifically, it argues that human dignity, with its greater conceptual scope and depth, could act as a foundational value with which to mitigate some of the shortcomings of the human rights approach. The purpose here is suggestive rather than definitive and is aimed at highlighting the link that has not been clearly made between human rights and human dignity. I argue that heightened attention to human dignity has the potential to create wider support for the human rights approach and ultimately help facilitate its efficacy in fisheries.  相似文献   
367.
天津雾和霾自动观测与人工观测的对比评估   总被引:3,自引:1,他引:2       下载免费PDF全文
为适应地面气象观测业务调整方向,提高新型自动气象站观测资料的质量及可用性,研究中对天津地区10个地面气象站1951—2014年历年2月人工观测及2014年2月自动观测和人工观测的轻雾、雾、霾现象进行对比评估。结果表明:天津地区历年2月轻雾的平均日数为10 d,雾和霾均为2 d,轻雾和霾同期出现的日数占有天气现象的7.4%,而雾和霾同期出现日数仅占0.7%;平行观测期的对比分析得到人工观测轻雾日数比自动观测多11 d,雾日数和霾日数均比自动观测少6 d,其中,轻雾和雾的判别差异集中出现在每日08:00(北京时,下同),霾则基本出现在每日08:00,14:00,17:00,20:00;通过对比自动观测和人工观测的能见度数据发现,二者相对偏差达25.1%,能见度小于15.0 km时,自动观测的能见度有60%~76%数值偏小,特别是08:00和20:00, 因此,在相对湿度满足条件的情况下,能见度的判别误差是导致自动观测与人工观测轻雾、雾、霾现象判别差异的重要原因。  相似文献   
368.
We report the genetic linkage map of Jian carp(C yprinus carpio var. Jian). An F1 population comprising 94 Jian carp individuals was mapped using 254 microsatellite markers. The genetic map spanned 1 381.592 c M and comprised 44 linkage groups,with an average marker distance of 6.58 c M. We identified eight quantitative trait loci(QTLs) for body weight(BW) in seven linkage groups,explaining 12.6% to 17.3% of the phenotypic variance. Comparative mapping was performed between Jian carp and mirror carp( Cyprinus carpio L.),which both have 50 chromosomes. One hundred and ninety-eight Jian carp marker loci were found in common with the mirror carp map,with 186(93.94%) showing synteny. All 44 Jian carp linkage groups could be one-to-one aligned to the 44 mirror carp linkage groups,mostly sharing two or more common loci. Three QTLs for BW in Jian carp were conserved in mirror carp. QTL comparison suggested that the QTL confidence interval in mirror carp was more precise than the homologous interval in Jian carp,which was contained within the QTL interval in Jian carp. The syntenic relationship and consensus QTLs between the two varieties provide a foundation for genomic research and genetic breeding in common carp.  相似文献   
369.
370.
有色金属资源在国民经建设中具有不可替代的作用,我省有色金属资源日趋紧缺,要解决资源危机必须建立2个市场,采取2个措施的建议。  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