全文获取类型
收费全文 | 689篇 |
免费 | 27篇 |
国内免费 | 12篇 |
专业分类
测绘学 | 29篇 |
大气科学 | 27篇 |
地球物理 | 164篇 |
地质学 | 356篇 |
海洋学 | 35篇 |
天文学 | 66篇 |
综合类 | 20篇 |
自然地理 | 31篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 21篇 |
2020年 | 28篇 |
2019年 | 23篇 |
2018年 | 70篇 |
2017年 | 53篇 |
2016年 | 70篇 |
2015年 | 36篇 |
2014年 | 56篇 |
2013年 | 73篇 |
2012年 | 29篇 |
2011年 | 39篇 |
2010年 | 35篇 |
2009年 | 28篇 |
2008年 | 20篇 |
2007年 | 22篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 14篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有728条查询结果,搜索用时 15 毫秒
701.
Riyaz Ahmad Mir Sanjay K. Jain Arun K. Saraf Ajanta Goswami 《Journal of the Indian Society of Remote Sensing》2014,42(1):91-105
Himalayan glaciers and their mass balance are poorly sampled through direct mass balance measurements. Thus, based on Landsat datasets of ETM+ (2000), ETM+ (2006) and TM (2011), mass balance studies of 32 glaciers was carried out using accumulation area ratio (AAR) method in the Tirungkhad river basin, a tributary of Satluj River, located in western Himalayan region. The overall specific mass balance was negative varying from ?27 cm (2000) to ?41 cm (2011). Out of 32 glaciers, 27 glaciers (81.2 %) showed negative mean mass balance and 5 glaciers (18.7 %) showed positive mean mass balance. Mean of specific mass balance for the year 2000, 2006 and 2011 was found to be ?48 cm, ?55 cm and ?0.61 cm respectively, in case of glaciers with negative mass balance while in case of glaciers with positive mass balance, it was 0.67 cm (2000), 0.56 cm (2006) and 0.47 cm (2011). The investigations suggested a loss of ?0.034 km3 of glacial ice for 2000, 0.036 km3 for 2006 and 0.038 km3 for 2011 respectively. The negative mass balance of the glaciers since 2000 correlates well with the increasing trend of annual mean temperature and decreasing trend of precipitation (snow water equivalent (SWE) and rainfall). Based on Mann Kendall test the temperature and SWE trends were significant at 95 % confidence level, however, the rainfall trend was insignificant. 相似文献
702.
703.
704.
705.
The present study deals with the inhomogeneous plane symmetric models in scalar-tensor theory of gravitation. We used symmetry group analysis method to solve the field equations analytically. A new class of similarity solutions have been obtained by considering the inhomogeneous nature of metric potential. The physical behavior and geometrical aspects of the derived models are also discussed. 相似文献
706.
Abstract Based on 16 years of oceanographic and meteorological data the monthly variations of the net heat flux at the air‐sea interface in coastal waters near Jeddah show that the sea gains an average of about 14 ±2 W m?2 from April to October and loses about 79± 4W m?2from November to March. The loss of heat during the winter months is not compensated by the gain during the summer months and therefore leads to an annual average deficit of 25 ± 3 Wm?2. The gain during summer may not favour the formation of a strong seasonal thermocline. 相似文献
707.
A. N. Khondaker Karim Malik Nahid Hossain Shaikh Abdur Razzak Rouf Ahmad Khan 《Climate Policy》2013,13(4):517-541
The energy sector is the main contributor to GHG emissions in Saudi Arabia. The tremendous growth of GHG emissions poses serious challenges for the Kingdom in terms of their reduction targets, and also the mitigation of the associated climate changes. The rising trend of population and urbanization affects the energy demand, which results in a faster rate of increase in GHG emissions. The major energy sector sources that contribute to GHG emissions include the electricity generation, road transport, desalination plants, petroleum refining, petrochemical, cement, iron and steel, and fertilizer industries. In recent years, the energy sector has become the major source, accounting for more than 90% of national CO2 emissions. Although a substantial amount of research has been conducted on renewable energy resources, a sustainable shift from petroleum resources is yet to be achieved. Public awareness, access to energy-efficient technology, and the development and implementation of a legislative framework, energy pricing policies, and renewable and alternative energy policies are not mature enough to ensure a significant reduction in GHG emissions from the energy sector. An innovative and integrated solution that best serves the Kingdom's long-term needs and exploits potential indigenous, renewable, and alternative energy resources while maintaining its sustainable development stride is essential.Policy relevanceThe main contributor to GHG emissions in Saudi Arabia is the energy sector that accounts for more than 90% of the national CO2 emissions. Tremendous growth of GHG emissions poses serious challenges for the Kingdom in their reduction and mitigating the associated climate changes. This study examines the changing patterns of different activities associated with energy sector, the pertinent challenges, and the opportunities that promise reduction of GHG emissions while providing national energy and economic security. The importance of achieving timely, sustained, and increasing reductions in GHG emissions means that a combination of policies may be needed. This study points to the long-term importance of making near- and medium-term policy choices on a well-informed, strategic basis. This analytical paper is expected to provide useful information to the national policy makers and other decision makers. It may also contribute to the GHG emission inventories and the climate change negotiations. 相似文献
708.
Gohar Rehman Sajjad Ahmad Shuhab D. Khan Fayaz Ali Taqweemul H. Ali Sadaf F. Khan 《Natural Hazards》2014,70(2):1589-1602
Glacial lake outburst flood (GLOF) is a powerful natural phenomenon that is very active in the Karakoram and Himalayas. This paper presents a case study from Gupis Tehsil in northern areas of Pakistan that is exposed to GLOFs from nine different glacial lakes in its upper catchment areas. Khukush Lake being the largest of all the glacial lakes has been studied and a flood attenuation model has been created for the whole Gupis Tehsil. This lake covers almost 2.2 km2 of surface area, and its calculated volume is 2.6 × 104 m3. In case of its outburst, the peak flow discharge is calculated to be 7,642 m3/s. The catchment area which contributes water and debris to the lake is 170 km2. This lake is dammed by a glacial moraine, which is not strong enough to sustain the pressure for a longer period of time. Other factors that are reducing the reliability of the dam are the secondary hazards which are in direct contact with the lake, and in case of their reactivation, they can put severe impacts on the dam. There are eight potential sites of the snow avalanche activity where debris along with snow may fall directly into the lake producing a strong wave. This strong wave of water will increase the pressure on the dam and ultimately will increase the probability for its outburst. The presense of water springs towards the downstream side of the natural dam also indicate the presence of hidden channels passing through the dam which may weaken the shear strength of the dam. Almost 24 villages settled along either sides of the Gupis River are critically studied for the expected flood from Khukush Lake. With few exceptions, almost 20–25 % area of all the villages will be affected from this flood. 相似文献
709.
Saifullah Nadeem Sarwar Sadia Bibi Mahtab Ahmad Yong Sik Ok 《Environmental Earth Sciences》2014,71(4):1663-1672
Cadmium (Cd) is a highly toxic heavy metal and its presence in soil is of great concern due to the danger of its entry into the food chain. Among many others, proper plant nutrition is an economic and practicable strategy for minimizing the damage to plants from Cd and to decrease Cd accumulation in edible plant parts. The study was carried out to compare the effectiveness of soil and foliar applications of zinc (Zn) to minimize Cd accumulation in wheat grains. The results revealed that the exposure of plants to Cd decreased plant growth and increased Cd concentration in the shoots and grains of wheat, when compared with unexposed plants. Foliar application of 0.3 % zinc sulfate solution effectively decreased Cd concentration in wheat grains. Foliar application of Zn at a suitable concentration can effectively ameliorate the adverse effects of Cd exposure and decrease the grain Cd concentration of wheat grown in Cd-contaminated soil. 相似文献
710.
Evaluating Boolean,AHP and WLC methods for the selection of waste landfill sites using GIS and satellite images 总被引:2,自引:2,他引:0
Himan Shahabi Soroush Keihanfard Baharin Bin Ahmad Mohammad Javad Taheri Amiri 《Environmental Earth Sciences》2014,71(9):4221-4233
The city of Saqqez has a population of 140,000 people, making it one of the largest cities in Iran. Population growth, consumerism, and change in eating habits, such as the increased use of packaged products, is causing the accumulation of waste in this city to increase. In this study, the selection of a waste landfill site for Saqqez focused on 13 layers of geography information that was used by the IDRISI and Arc GIS software. Different models of the analytic multi-criteria decision-making process, such as an analytical hierarchy process (AHP), weighted linear combination (WLC), and Boolean logic, were used to manage layers to establish specific databases for urban waste landfills. Satellite images (Landsat ETM+ and SPOT 5), proposed sites and a land use map of the study area were also used. The results of this study indicated that two methods (AHP and WLC) in the early stages had better decision-making powers for locating landfill sites when compared to Boolean logic. Overlapping and compounding the similarities between these models in Arc GIS software, a 74-ha site was found. This site will be able to accept 130 tons of waste per day for the next 20 years. 相似文献