全文获取类型
收费全文 | 14900篇 |
免费 | 1726篇 |
国内免费 | 1971篇 |
专业分类
测绘学 | 5011篇 |
大气科学 | 2178篇 |
地球物理 | 2320篇 |
地质学 | 3311篇 |
海洋学 | 1541篇 |
天文学 | 1252篇 |
综合类 | 1455篇 |
自然地理 | 1529篇 |
出版年
2024年 | 74篇 |
2023年 | 154篇 |
2022年 | 463篇 |
2021年 | 604篇 |
2020年 | 612篇 |
2019年 | 687篇 |
2018年 | 487篇 |
2017年 | 815篇 |
2016年 | 697篇 |
2015年 | 720篇 |
2014年 | 836篇 |
2013年 | 1027篇 |
2012年 | 925篇 |
2011年 | 862篇 |
2010年 | 681篇 |
2009年 | 858篇 |
2008年 | 894篇 |
2007年 | 1037篇 |
2006年 | 973篇 |
2005年 | 797篇 |
2004年 | 746篇 |
2003年 | 577篇 |
2002年 | 491篇 |
2001年 | 419篇 |
2000年 | 344篇 |
1999年 | 319篇 |
1998年 | 251篇 |
1997年 | 192篇 |
1996年 | 179篇 |
1995年 | 155篇 |
1994年 | 141篇 |
1993年 | 134篇 |
1992年 | 79篇 |
1991年 | 67篇 |
1990年 | 45篇 |
1989年 | 45篇 |
1988年 | 33篇 |
1987年 | 22篇 |
1986年 | 22篇 |
1985年 | 22篇 |
1984年 | 26篇 |
1983年 | 8篇 |
1982年 | 17篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1978年 | 5篇 |
1977年 | 11篇 |
1972年 | 4篇 |
1971年 | 5篇 |
1954年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
91.
张训华 《海洋地质与第四纪地质》1994,14(4):95-100
本文简要介绍了局控项目《中国海区1∶50万区域地质编图(大连幅)》重力异常图、磁力异常图的编制过程,给出了一种以计算机为手段、实现编图自动化的新方法,并分析了该方法与以往编图方法的不同和优点,以国际分幅在中国海区开展区域地质编图尚属首次,在既无海区地质调查规范,又无海区地质调查编图规范的情况下,这一工作无异具有开创性。从理论上系统总结出一套切实可行的编图方法,对于编制中国海区区域地质调查编图规范以 相似文献
92.
93.
94.
A spread of warm water from the first crest of the Kuroshio Extension is periodically enhanced by northward warm water intrusions from the main current. The water type in the spread area was previously found to be the same as that in the Kuroshio front at depth. In looking for the possible mechanism responsible for the northward warm water intrusions, a dynamic analysis in the Kuroshio front was carried out by using CTD, ADCP, AVHRR and ARGOS buoy data, obtained in 1996 by the R.V. Hakuho Maru. Downstream, cross-stream and vertical velocities in the Kuroshio Extension were found by using a "stream coordinate system". The velocity field in the Kuroshio front at the first crest showed a double structure with two surface velocity maxima. In the inner part of the front, relatively high cross-stream (northward) and vertical (upward) velocities were found. Thus, this study suggests that while water particles flow downstream along the first stationary meander of the Kuroshio Extension, they also experience lateral and vertical movements which allow the deeper water from an upstream location to rise to the surface layer, and in certain locations to deflect northward. By assuming isopycnal movement and conservation of potential vorticity, it was found that in those locations where anticyclonic curvature of the meander increases, warm water is more likely to deflect northward. High ageostrophic components observed in the first 300 m of the water column are probably related to the relatively high cross-stream and vertical velocities in the inner part of the front. 相似文献
95.
A preliminary study of carbon system in the East China Sea 总被引:1,自引:0,他引:1
Shizuo Tsunogai Shuichi Watanabe Junya Nakamura Tsuneo Ono Tetsuro Sato 《Journal of Oceanography》1997,53(1):9-17
In the central part of the East China Sea, the activity of CO2 in the surface water and total carbonate, pH and alkalinity in the water column were determined in winter and autumn of 1993.
The activity of CO2 in the continental shelf water was about 50 ppm lower than that of surface air. This decrease corresponds to the absorption
of about 40 gC/m2/yr of atmospheric CO2 in the coastal zone or 1 GtC/yr in the global continental shelf, if this rate is applicable to entire coastal seas. The normalized
total carbonate contents were higher in the water near the coast and near the bottom. This increase toward the bottom may
be due to the organic matter deposited on the bottom. This conclusion is supported by the distribution of pH. The normalized
alkalinity distribution also showed higher values in the near-coast water, but in the surface water, indicating the supply
of bicarbonate from river water. The residence time of the East China Sea water, including the Yellow Sea water, has been
calculated to be about 0.8 yr from the excess alkalinity and the alkalinity input. Using this residence time and the excess
carbonate, we can estimate that the amount of dissolved carbonate transported from the coastal zone to the oceanic basin is
about 70 gC/m2/yr or 2 GtC/yr/area-of-global-continental-shelf. This also means that the rivers transport carbon to the oceans at a rate
of 30 gC/m2/yr of the coastal sea or 0.8 GtC/yr/ area-of-global shelf, the carbon consisting of dissolved inorganic carbonate and terrestrial
organic carbon decomposed on the continental shelf. 相似文献
96.
97.
从数据管理及后期应用的角度提出了数据平台的要领,讨论了该数据平台的物理结构、逻辑结构,在分类与组织的基础上给出了相应的数据字典。同时,还基于该平台探讨了测井曲线库及图形库的建设方法,并实现了具体功能。 相似文献
98.
采集设备采集数据发送到值班PC机,在无人干预的情况下接收处理软件自动对数据进行回放和进一步处理,为用户提供数据产品和服务,并提供一个界面,使用户能够了解系统的运行状况,获得相关数据和状态参数。 相似文献
99.
100.
研究pH和Ca(Ⅱ)对砷酸根在海水与NaCl介质中对水合氧化物和粘土矿物上交换吸附的影响:(1)在酸性条件下和海水及NaCl介质中,砷酸根在针铁矿上的交换率E(%)—pH曲线呈平顶峰型、在δ-MnO呈峰型、在粘土上分别呈双峰型和肩峰型。这是砷酸根存在多种形式与固体表面发生离子/配位子交换以及介质中阴离子竞争交换吸附共同作用的结果。(2)在碱性条件下的海水介质中,砷酸根与水合氧化物和粘土矿物的E(%)—pH曲线都呈V型,这是因为生成了具有一定结构的液—固界面三元络合物之故。(3)在NaCl介质中,Ca加入起促进作用,再次证明液—固界面三元络合物生成机理与V型曲线的内在关系 相似文献