全文获取类型
收费全文 | 1992篇 |
免费 | 345篇 |
国内免费 | 373篇 |
专业分类
测绘学 | 266篇 |
大气科学 | 352篇 |
地球物理 | 456篇 |
地质学 | 821篇 |
海洋学 | 261篇 |
天文学 | 87篇 |
综合类 | 234篇 |
自然地理 | 233篇 |
出版年
2024年 | 8篇 |
2023年 | 37篇 |
2022年 | 106篇 |
2021年 | 113篇 |
2020年 | 121篇 |
2019年 | 92篇 |
2018年 | 103篇 |
2017年 | 124篇 |
2016年 | 138篇 |
2015年 | 112篇 |
2014年 | 122篇 |
2013年 | 142篇 |
2012年 | 131篇 |
2011年 | 136篇 |
2010年 | 93篇 |
2009年 | 115篇 |
2008年 | 110篇 |
2007年 | 98篇 |
2006年 | 84篇 |
2005年 | 69篇 |
2004年 | 49篇 |
2003年 | 58篇 |
2002年 | 54篇 |
2001年 | 45篇 |
2000年 | 41篇 |
1999年 | 71篇 |
1998年 | 48篇 |
1997年 | 56篇 |
1996年 | 30篇 |
1995年 | 33篇 |
1994年 | 30篇 |
1993年 | 25篇 |
1992年 | 31篇 |
1991年 | 25篇 |
1990年 | 11篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1971年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有2710条查询结果,搜索用时 31 毫秒
61.
Widely distributed on tidal flats on the west and south coast of Korea, the long arm octopus Octopus minor is one of the important shellfish resources, as 相似文献
62.
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
63.
Availability of reliable delineation of urban lands is fundamental to applications such as infrastructure management and urban planning. An accurate semantic segmentation approach can assign each pixel of remotely sensed imagery a reliable ground object class. In this paper, we propose an end-to-end deep learning architecture to perform the pixel-level understanding of high spatial resolution remote sensing images. Both local and global contextual information are considered. The local contexts are learned by the deep residual net, and the multi-scale global contexts are extracted by a pyramid pooling module. These contextual features are concatenated to predict labels for each pixel. In addition, multiple additional losses are proposed to enhance our deep learning network to optimize multi-level features from different resolution images simultaneously. Two public datasets, including Vaihingen and Potsdam datasets, are used to assess the performance of the proposed deep neural network. Comparison with the results from the published state-of-the-art algorithms demonstrates the effectiveness of our approach. 相似文献
64.
针对适合捷联式重力仪的AUV搭载平台的选型问题,基于国内AUV实际航行数据,分析了多推进器组合、推进器和浮力舱组合、推进器和鳍舵组合等3类AUV的定深航行运动特性;推导了AUV水下航行在3个坐标轴方向上对重力仪产生的运动加速度计算公式,得到运动加速度与AUV水下6个自由度运动要素的解析表达式;基于运动加速度分析,讨论了适用于水下移动重力测量的AUV平台和推进装置设计,进行了AUV搭载平台的优选,并给出了重力仪安装位置建议;选定的AUV实验平台实施移动重力测量验证试验重复线精度达到0.42mGal,验证了搭载平台优选的有效性。 相似文献
65.
Sumi Kanij Rukshana Kim Soo Cheol Howlader Jewel Sharker Md Rajib Choi Kap Seong Choi Sang Ki Park Jong-In Nou Ill-Sup Kho Kang Hee 《Ocean Science Journal》2019,54(3):363-374
Ocean Science Journal - A carbonic anhydrase VII gene, encoding 277 amino acids, was identified in the intestinal tissue of pufferfish (Takifugu rubripes). The translated protein with an 833-bp... 相似文献
66.
基于自动探测方法的南海北部涡致海表温度锋面的特征研究 总被引:1,自引:0,他引:1
南海北部具有丰富的温度锋面和中尺度涡,它们调节着局地的热量和能量平衡。本文利用卫星海洋高度异常和海表温度数据,并基于自动探测方法,探究了2007年至2017年南海北部中尺度涡边缘的海表温度锋面(涡致锋面)特征。反气旋/气旋边缘出现锋面的概率可达20%。气旋涡在各个方向上出现锋面的概率比较均匀,反气旋涡的东北部和西南部出现锋面的概率大于西北部和东南部。中尺度涡致锋面的数量有明显的季节变化,而涡动能未表现出明显的季节变化。中尺度涡致锋区的总涡动能是中尺度涡内动能的3倍,并且反气旋涡致锋面的总涡动能明显强于气旋涡致锋面的总涡动能。中尺度涡致锋面的数量和涡动能的年际变化与厄尔尼诺南方涛动指数没有明显的相关性。本研究也讨论了中尺度涡致锋面的可能机制,但是中尺度涡对海表温度锋的贡献需要进一步定量研究。 相似文献
67.
68.
69.
Vertical distributions of aerosol optical properties during haze and floating dust weather in Shanghai 下载免费PDF全文
A comparative study on the vertical distributions of aerosol optical properties during haze and floating dust weather in Shanghai was conducted based on the data obtained from a micro pulse lidar.There was a distinct difference in layer thickness and extinction coefficient under the two types of weather conditions.Aerosols were concentrated below 1 km and the aerosol extinction coefficients ranged from 0.25 to 1.50km-1 on haze days.In contrast,aerosols with smaller extinction coefficients(0.20 0.35 km-1) accumulated mainly from the surface to 2 km on floating dust days.The seasonal variations of extinction and aerosol optical depth(AOD) for both haze and floating dust cases were similar greatest in winter,smaller in spring,and smallest in autumn.More than 85%of the aerosols appeared in the atmosphere below 1 km during severe haze and floating dust weather.The diurnal variation of the extinction coefficient of haze exhibited a bimodal shape with two peaks in the morning or at noon,and at nightfall,respectively.The aerosol extinction coefficient gradually increased throughout the day during floating dust weather.Case studies showed that haze aerosols were generated from the surface and then lifted up,but floating dust aerosols were transported vertically from higher altitude to the surface.The AOD during floating dust weather was higher than that during haze.The boundary layer was more stable during haze than during floating dust weather. 相似文献
70.