全文获取类型
收费全文 | 4266篇 |
免费 | 136篇 |
国内免费 | 99篇 |
专业分类
测绘学 | 84篇 |
大气科学 | 500篇 |
地球物理 | 1038篇 |
地质学 | 1367篇 |
海洋学 | 770篇 |
天文学 | 442篇 |
综合类 | 50篇 |
自然地理 | 250篇 |
出版年
2022年 | 24篇 |
2021年 | 53篇 |
2020年 | 54篇 |
2019年 | 74篇 |
2018年 | 153篇 |
2017年 | 145篇 |
2016年 | 158篇 |
2015年 | 104篇 |
2014年 | 199篇 |
2013年 | 262篇 |
2012年 | 158篇 |
2011年 | 243篇 |
2010年 | 233篇 |
2009年 | 234篇 |
2008年 | 216篇 |
2007年 | 212篇 |
2006年 | 192篇 |
2005年 | 163篇 |
2004年 | 130篇 |
2003年 | 128篇 |
2002年 | 126篇 |
2001年 | 90篇 |
2000年 | 104篇 |
1999年 | 72篇 |
1998年 | 66篇 |
1997年 | 62篇 |
1996年 | 42篇 |
1995年 | 54篇 |
1994年 | 38篇 |
1993年 | 30篇 |
1992年 | 37篇 |
1991年 | 31篇 |
1990年 | 27篇 |
1989年 | 24篇 |
1988年 | 25篇 |
1987年 | 39篇 |
1986年 | 25篇 |
1985年 | 35篇 |
1984年 | 56篇 |
1983年 | 53篇 |
1982年 | 44篇 |
1981年 | 38篇 |
1980年 | 41篇 |
1979年 | 21篇 |
1978年 | 19篇 |
1977年 | 28篇 |
1976年 | 14篇 |
1975年 | 26篇 |
1974年 | 20篇 |
1973年 | 16篇 |
排序方式: 共有4501条查询结果,搜索用时 125 毫秒
171.
172.
Arctic river basins are amongst the most vulnerable to climate change. However, there is currently limited knowledge of the hydrological processes that govern flow dynamics in Arctic river basins. We address this research gap using natural hydrochemical and isotopic tracers to identify water sources that contributed to runoff in river basins spanning a gradient of glacierization (0–61%) in Svalbard during summer 2010 and 2011. Spatially distinct hydrological processes operating over diurnal, weekly and seasonal timescales were characterized by river hydrochemistry and isotopic composition. Two conceptual water sources (‘meltwater’ and ‘groundwater’) were identified and used as a basis for end‐member mixing analyses to assess seasonal and year‐to‐year variability in water source dynamics. In glacier‐fed rivers, meltwater dominated flows at all sites (typically >80%) with the highest contributions observed at the beginning of each study period in early July when snow cover was most extensive. Rivers in non‐glacierized basins were sourced initially from snowmelt but became increasingly dependent on groundwater inputs (up to 100% of total flow volume) by late summer. These hydrological changes were attributed to the depletion of snowpacks and enhanced soil water storage capacity as the active layer expanded throughout each melt season. These findings provide insight into the processes that underpin water source dynamics in Arctic river systems and potential future changes in Arctic hydrology that might be expected under a changing climate. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
173.
Ki‐mook Kang Duk‐jin Kim Yunjee Kim Eunhee Lee Bong‐Gwan Kim Seung Hee Kim Kyoochul Ha Dong‐Chan Koh Yang‐Ki Cho Guebuem Kim 《水文研究》2019,33(7):1089-1100
Submarine groundwater discharge (SGD) plays an important role in coastal biogeochemical processes and hydrological cycles, particularly off volcanic islands in oligotrophic oceans. However, the spatial and temporal variations of SGD are still poorly understood owing to difficulty in taking rapid SGD measurements over a large scale. In this study, we used four airborne thermal infrared surveys (twice each during high and low tides) to quantify the spatiotemporal variations of SGD over the entire coast of Jeju Island, Korea. On the basis of an analytical model, we found a linear positive correlation between the thermal anomaly and squares of the groundwater discharge velocity and a negative exponential correlation between the anomaly and water depth (including tide height and bathymetry). We then derived a new equation for quantitatively estimating the SGD flow rates from thermal anomalies acquired at two different tide heights. The proposed method was validated with the measured SGD flow rates using a current meter at Gongcheonpo Beach. We believe that the method can be effectively applied for rapid estimation of SGD over coastal areas, where fresh groundwater discharge is significant, using airborne thermal infrared surveys. 相似文献
174.
Submarine groundwater discharge revealed by aerial thermal infrared imagery: a case study on Jeju Island,Korea 下载免费PDF全文
Eunhee Lee Ki‐mook Kang Sung Pil Hyun Kil‐Yong Lee Heesung Yoon Seung Hee Kim Yongcheol Kim Zhen Xu Duk‐jin Kim Dong‐Chan Koh Kyoochul Ha 《水文研究》2016,30(19):3494-3506
Submarine groundwater discharge (SGD) is a global phenomenon that carries large volumes of groundwater and dissolved chemical species such as nutrient, metals, and organic compounds to coastal zones. We report the influence of SGD on the coastal waters of Jeju Island, Korea, using high‐resolution aerial thermal infrared (TIR) mapping techniques and field investigations. An aircraft‐based system was implemented using a cost‐effective TIR camera for aerial TIR mapping. Ground‐based calibrations and system integration with GPS/IMU (global positioning system/inertial measurement unit) were performed for the aerial systems. The aerial surveys showed distinct low‐temperature signatures of SGD along the coasts of Jeju Island, revealing large groundwater inputs from the coastal aquifers to the ocean. Multiple aerial surveys over a range of seasons and tidal stages revealed that SGD rates dynamically affect the sea surface temperature (SST) of the coastal zone. The in‐situ measurements supported that SGD has a substantial influence on the coastal water chemistry as well as SST. Our observations highlight the extent to which aerial‐based TIR mapping can serve as a powerful tool for studying SGD and other coastal processes. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
175.
Two primary concerns in performing watershed overland flow routing are the numerical instability and computational efficiency. The stability of executing an explicit scheme has to be maintained by observing the Courant–Friedrich–Lewy criterion, which is adopted to confirm that the numerical marching speed is larger than the wave celerity. Moreover, there is another criterion of time step devised in previous studies to avoid back‐and‐forth refluxing between adjacent grids. The situation of refluxing usually occurs on flat regions. In light of this, the selection of a small time increment to honor both restrictions simultaneously is believed to decrease the computational efficiency in performing overland flow routing. This study aims at creating a robust algorithm to relax both restrictions. The proposed algorithm was first implemented on a one‐dimensional overland plane to evaluate the accuracy of the numerical result by comparing it with an analytical solution. Then, the algorithm was further applied to a watershed for 2D runoff simulations. The results show that the proposed integrated algorithm can provide an accurate runoff simulation and achieve satisfactory performance in terms of computational speed. 相似文献
176.
177.
178.
179.
180.
Jui Le Loh Fredolin Tangang Liew Juneng David Hein Dong-In Lee 《Asia-Pacific Journal of Atmospheric Sciences》2016,52(2):191-208
This study investigates projected changes in rainfall and temperature over Malaysia by the end of the 21st century based on the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) A2, A1B and B2 emission scenarios using the Providing Regional Climates for Impacts Studies (PRECIS). The PRECIS regional climate model (HadRM3P) is configured in 0.22° × 0.22° horizontal grid resolution and is forced at the lateral boundaries by the UKMO-HadAM3P and UKMOHadCM3Q0 global models. The model performance in simulating the present-day climate was assessed by comparing the modelsimulated results to the Asian Precipitation - Highly-Resolved Observational Data Integration Towards Evaluation (APHRODITE) dataset. Generally, the HadAM3P/PRECIS and HadCM3Q0/PRECIS simulated the spatio-temporal variability structure of both temperature and rainfall reasonably well, albeit with the presence of cold biases. The cold biases appear to be associated with the systematic error in the HadRM3P. The future projection of temperature indicates widespread warming over the entire country by the end of the 21st century. The projected temperature increment ranges from 2.5 to 3.9°C, 2.7 to 4.2°C and 1.7 to 3.1°C for A2, A1B and B2 scenarios, respectively. However, the projection of rainfall at the end of the 21st century indicates substantial spatio-temporal variation with a tendency for drier condition in boreal winter and spring seasons while wetter condition in summer and fall seasons. During the months of December to May, ~20-40% decrease of rainfall is projected over Peninsular Malaysia and Borneo, particularly for the A2 and B2 emission scenarios. During the summer months, rainfall is projected to increase by ~20-40% across most regions in Malaysia, especially for A2 and A1B scenarios. The spatio-temporal variations in the projected rainfall can be related to the changes in the weakening monsoon circulations, which in turn alter the patterns of regional moisture convergences in the region. 相似文献