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   1511篇
  免费   155篇
  国内免费   164篇
测绘学   39篇
大气科学   214篇
地球物理   345篇
地质学   592篇
海洋学   292篇
天文学   4篇
综合类   58篇
自然地理   286篇
  2024年   5篇
  2023年   15篇
  2022年   36篇
  2021年   42篇
  2020年   40篇
  2019年   46篇
  2018年   20篇
  2017年   85篇
  2016年   62篇
  2015年   76篇
  2014年   86篇
  2013年   78篇
  2012年   47篇
  2011年   90篇
  2010年   59篇
  2009年   116篇
  2008年   116篇
  2007年   90篇
  2006年   93篇
  2005年   73篇
  2004年   63篇
  2003年   44篇
  2002年   63篇
  2001年   39篇
  2000年   54篇
  1999年   48篇
  1998年   41篇
  1997年   33篇
  1996年   36篇
  1995年   36篇
  1994年   15篇
  1993年   20篇
  1992年   15篇
  1991年   13篇
  1990年   7篇
  1989年   10篇
  1988年   3篇
  1987年   3篇
  1985年   3篇
  1984年   3篇
  1983年   1篇
  1982年   2篇
  1980年   1篇
  1976年   1篇
  1972年   1篇
排序方式: 共有1830条查询结果,搜索用时 625 毫秒
961.
《China Geology》2018,1(3):435-449
Focusing on the Yangtze River economic zone, the previous geological researches are systematically summarized, resources and environment conditions and major geological problems which are needing to be concerned in land planning and construction are studied. The results show that the resource conditions of cultivated land, shale gas, geotherm, lithium and so on are superior in the Yangtze River economic zone, and the resources and environment conditions are conducive to develop the modern agriculture, clean energy industry and strategic emerging industries. 3×1013 m2 farmlands without heavy metal pollution are concentrated; there are three national level shale gas exploration and development bases with explored reserves of 5.441×1011 m3; geothermal availability is 2.4×109 t of standard coal each year, equivalent to 19% of the amount of coal in 2014; Asia’s largest energy lithium metal ore deposit is found. In some parts of Yangtze River economic zone, there are some major geological problems such as active faults, karst collapse, ground subsidence, landslide-collapse-debris flow, affecting the river-crossing channels, high-speed railway, urban agglomeration and green ecological corridor planning and construction. Those problems should be concerned, and the relevant suggestions and countermeasures are put forward. Meanwhile, the ideas to further support the development of the Yangtze River economic zone are put forward.  相似文献   
962.
Failure to address unsustainable global change is often attributed to failures in conventional environmental governance. Polycentric environmental governance—the popular alternative—involves many centres of authority interacting coherently for a common governance goal. Yet, longitudinal analysis reveals many polycentric systems are struggling to cope with the growing impacts, pace, and scope of social and environmental change. Analytic shortcomings are also beginning to appear, particularly in the treatment of power. Here we draw together diverse social science perspectives and research into a variety of cases to show how different types of power shape rule setting, issue construction, and policy implementation in polycentric governance. We delineate an important and emerging research agenda for polycentric environmental governance, integrating diverse types of power into analytical and practical models.  相似文献   
963.
1804号台风“艾云尼”龙卷分析   总被引:13,自引:5,他引:8  
2018年6月8日,在1804号台风“艾云尼”螺旋雨带中发生了两次陆龙卷天气,分别袭击了广州市南沙区横沥镇和佛山市南海区大沥镇。利用广州CINRAD/SA多普勒天气雷达、佛山CINRAD/XD多普勒天气雷达、5 min间隔的地面自动气象站和MICAPS等资料,研究了两次陆龙卷的天气背景、环境参数和龙卷风暴中尺度结构特征。结果表明:广州南沙龙卷为台风环流外围龙卷,位于台风中心的东北象限,强度为EF3级;佛山南海龙卷为台风环流内部龙卷,位于台风中心的东侧,强度为EF1级。龙卷均发生在中低空强东南急流在珠江口附近上下叠加和高层辐散的有利大尺度环流背景下。环境条件表现为较强的低层风垂直切变和较大的风暴相对螺旋度(SRH)、较小的对流有效位能(CAPE)和对流抑制能量(CIN)、极低的抬升凝结高度(LCL);地面存在中尺度辐合线和小尺度涡旋。广州S波段雷达探测到两次龙卷母风暴的低层钩状回波和入流缺口回波特征及低层中等强度中气旋,龙卷出现在钩状回波顶端、中气旋中心附近。佛山X波段双偏振雷达清晰地探测到佛山南海区大沥龙卷的微型超级单体和龙卷碎片特征(TDS)。   相似文献   
964.
A significant challenge in resource management is addressed: the perceived trade-off between economic growth and ecosystem restoration and conservation. Traditional approaches to management regard restoration as a potential cost to economic productivity. In this study we show that by considering a broader range of economic values, including ecosystem services values, an argument can be made that restoration of lake ecosystems also leads to favourable economic outcomes when commonly disregarded values are considered. Our case study analyses the ecological outcomes of different catchment mitigation and land use scenarios in terms of water quality results in a lake, assessing changes in land use values based on opportunity costs, and ecosystem services values. We show that when considering the value of ecosystem services, intensive agricultural land use is not necessarily the most economically valuable form of land use within a lake catchment. Indeed, a shift towards alternative land uses within a catchment can lead to both ongoing economic benefits and improvements in water quality. In this context, land-use change offers an option for water quality improvement that minimises lake and land mitigation costs, while adding value to catchment land use. An argument is made supporting land use change towards indigenous forest types, which can sustain alternative sources of income such as a range of recreational values, while supporting important ecosystem functions for the region.  相似文献   
965.
An estimated 26% of current global child deaths can be attributed to various and modifiable environmental factors, which are addressed under multiple Sustainable Development Goals (SDGs). This study assesses future reductions in child mortality in relation to the achievement of environment-related SDG targets. It uses projections of health risk factors from the IMAGE 3.0 Integrated Assessment Model, based on the Shared Socioeconomic Pathways (SSPs), linked to a standard multi-state health model (GISMO), distinguishing risk factors, disease occurrence and cause-specific death. The study concludes that, on a global level, the SDG target on child mortality will not be achieved in any of the three SSP scenarios analysed, mainly due to persistent high mortality rates in Sub-Saharan Africa and South Asia. By 2030, environmental health risk factors – including childhood undernutrition, no access to improved drinking water and sanitation, no access to modern fuels and exposure to malaria – will still be responsible for 14% to 16% of total global child deaths (8% to 10% when excluding nutrition-related mortality). Under the middle-of-the-road SSP2 baseline scenario, achievement of the SDG targets on hunger, drinking water and sanitation and modern energy services, would avoid 433 thousand child deaths by 2030. If, in addition, also higher standards would be achieved for access to water and energy, as well as universal secondary female education and advanced malaria control, a total of 733 thousand child deaths is projected to be avoided by 2030 (444 thousand child deaths, when excluding nutrition-related mortality), which would reduce projected global child mortality by 13%. Overall, more than 25% of the child mortality reduction that is needed to achieve the SDG target in Sub-Saharan Africa can be achieved through SDG-related policies on food, water and energy. This requires integrated and intersectoral approaches to environmental health.  相似文献   
966.
白琨琳 《地质与勘探》2021,57(3):656-666
成因法是油气资源评价中常用的方法,能较好地体现含油气盆地的生烃、排烃、运聚等过程,具有明确的地质意义,可用来计算油气资源量的"上限值"。其中运聚系数取值是成因法计算的重难点,因此有必要建立一个简单有效并能体现出成因法计算特点的运聚系数取值模型。本文从成因法的自身特点出发,分析了目前运聚系数取值存在的问题,初步建立了运聚系数取值模型。该模型将计算过程分为排烃过程、运移过程、聚集过程、储存过程、破坏过程、资源比例过程这6个过程,并分别设立了6个过程中各项参数的取值依据。最后通过2个刻度区的实例验证,证明该取值模型准确度较高,在中-低勘探程度地区适用性较高,在高勘探程度地区适用性中等。  相似文献   
967.
在开展地质灾害变形监测的过程中,由于传感器采集数据结果会受到客观环境的影响而出现异常情况,导致对变形情况的监测结果与实际情况存在较大误差,为此,提出基于多传感器估值融合理论的地质灾害变形监测方法研究。在对多传感器数据进行预处理阶段,引入了估值融合理论,具体采用的融合算法为最小误差均方差法,利用其对传感器采集数据结果中的异常值进行校正。在变形监测阶段,充分利用了多个数据源(传感器)对同一目标进行观测时的特征构成,结合观测特征、实时状态数据与发展函数三者之间的关系,实现对地质灾害变形情况的有效监测。在测试结果中,设计方法能够获取某地铁隧道水平方向上和垂直方向上的位移结果,具有较高的可靠性和精度。  相似文献   
968.
通过对泥河湾盆地43条剖面和6个钻孔晚新生代地层和微体古生物(介形类和有孔虫)的调查研究,发现非常丰富的介形类,计26属70余种,有孔虫4属4种,其中介形类自下而上可明显地划分为5个组合带:(1)Potamocypris plana-Candoniella-Ilyocypris组合带;(2)Leucocythere-Ilyocypris-Candoniella组合带;(3)Leucocythere-Cytherissa-Limnocythere组合带;(4)Ilyocypris-Limnocythere flexa-Limnocythere dubiosa组合带;(5)Limnocythere dubiosa-Limnocythere sancti-Patricii-Ilyocypris组合带。按以上5个介形类组合带的分布,第1组合带及所含地层红崖村组和石匣组的时代为上新世;第2~4组合带及所含地层泥河湾组的时代为早更新世;第5组合带为中-晚更新世,分布于虎头梁组和许家窑组,虎头梁组置中更新世为宜,许家窑组为晚更新世。根据5个介形类组合带和有孔虫的分布及介形类的始现、繁盛、兴衰的演替特征,对泥河湾古湖和盆地的形成经历了上新世的起始,早更新世早期的扩展,中、晚期稳定、发展、湖面最大,中更新世向西部退缩和晚更新世消亡、桑干河水系形成五个发展阶段的演化进行了探讨。  相似文献   
969.
This article tells the story of long-lasting and ongoing struggles surrounding the construction plans for a major reservoir on the headwaters of the Kemi River in the Finnish Province of Lapland. A point of contention since the beginning of hydropower development on the river in the mid twentieth century, the reservoir project has been promoted and abandoned multiple times in waves of land purchasing, legal procedures, opposition campaigns, and the delineation of nature reserves. Despite a Finnish Supreme Administrative Court ruling officially setting an end to the project, it never entirely left public discourse and is currently being re-negotiated in slightly adapted form. Articulating voices and documenting practices of riverbank inhabitants, activists and hydro electricity managers, this article presents the struggle as multiple modes of heterogeneous engineering, where both proponents and opponents work towards creating different realities. The article develops the metaphor of heterogeneous engineering by drawing attention to three temporal dimensions central to the reservoir struggle: moments, which refer to the situated emergence of practices and strategies; futures, which speak to the attempts to build and contest expectations regarding conflicting projects; and durations, which consider the cumulative aspects of a decades-long struggle on people and landscapes. Thereby, the article contributes to discussions on making, planning and environmental management, and illustrates ways of studying these processes as situated practices in relation to time.  相似文献   
970.
This paper analyses how in the aftermath of one of the worst environmental disasters ever to occur in Spain – the Aznalcóllar Disaster – various environmentalist and conservationist groups mobilised migratory birds to bring new insights and the need for new precautions to the controversy elicited by the spill. The case study, thus, revolves around how environmentalists established a “hybrid collective action” to draw attention to unconsidered risks and impacts of the disaster and thereby make the case for open debate. Building upon this, I engage with two different, though interrelated, theoretical debates that contribute to a rethinking of environmental management (EM) as a social and materially situated practice. Drawing on the idea of “tactic” (De Certeau, 1984), I draw attention to the devices, actions and procedures that environmentalists carried out to resist attempts to minimise the spill and to undermine administrations’ assumptions of control, coherence and singularity associated the idea of management. Drawing on Tim Ingold’s latest work (2007, 2008, 2011), I analyse environmentalists’ most successful tactic: the enactment of migratory birds as “lines”. Together with other authors in this special issue, I will use this notion to make an argument against some of the assumptions of the “hybrid ontology”. In contrast to more essentialists and static notions of non-human agency and politics, the idea of line is particularly useful as a way of understanding how nature(s) can be effectuated differently and how this leads to the imagining of new regimes of cohabitation, human and non-human management and intervention.  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