全文获取类型
收费全文 | 1184篇 |
免费 | 365篇 |
国内免费 | 441篇 |
学科分类
地球科学 | 1990篇 |
出版年
2024年 | 4篇 |
2023年 | 18篇 |
2022年 | 38篇 |
2021年 | 48篇 |
2020年 | 54篇 |
2019年 | 65篇 |
2018年 | 48篇 |
2017年 | 70篇 |
2016年 | 79篇 |
2015年 | 68篇 |
2014年 | 96篇 |
2013年 | 110篇 |
2012年 | 99篇 |
2011年 | 105篇 |
2010年 | 102篇 |
2009年 | 83篇 |
2008年 | 103篇 |
2007年 | 102篇 |
2006年 | 90篇 |
2005年 | 77篇 |
2004年 | 81篇 |
2003年 | 58篇 |
2002年 | 64篇 |
2001年 | 48篇 |
2000年 | 40篇 |
1999年 | 47篇 |
1998年 | 38篇 |
1997年 | 26篇 |
1996年 | 33篇 |
1995年 | 20篇 |
1994年 | 22篇 |
1993年 | 20篇 |
1992年 | 16篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有1990条查询结果,搜索用时 15 毫秒
1.
1 INTRODUCTIONGlobal change research involves much geo-objectsand geo-process, such as climate and environmentalchange, substance and energy cycling, land-use/land-cover change (LUCC), interactivity between human and nature, etc.. So it need cooperation frommany research communities including international research programs groups such as IGBP (InternationalGeosphere-Biosphere Programme IPCC (Intergovemmental Panel on Climate Change), IHDP (InternationalHuman Dimension Program o… 相似文献
2.
Tidal inundation mapping under enhanced land subsidence in Semarang,Central Java Indonesia 总被引:3,自引:0,他引:3
Tidal inundation by high tide under enhanced land subsidence is a damaging phenomenon and a major threat to the Semarang urban
area in Indonesia. It impacts on economic activities, as well as the cost of an emergency program and causes interruption
of pubic services, danger of infectious diseases and injury to human lives. This study examines a spatial analysis tool on
the GIS-raster system for the tidal inundation mapping based on the subsidence-benchmark data and modified detail digital
elevation model. Neighborhood operation and iteration model as a spatial analysis tool have been applied in order to calculate
the encroachment of the tidal inundation on the coastal area. The resulting map shows that the tidal flood spreads to the
lowland area and causes the inundation of coastal settlement, infrastructure, as well as productive agricultural land, i.e.,
the fish-pond area. The monitoring of the vulnerable area due to the tidal inundation under the scenario of extended land
subsidence plays an important role in long-term coastal zone management in Semarang. 相似文献
3.
作者研究三维变系数抛物方程 Douglas交替方向隐格式的稳定性和收敛性。采用 H1能量估计方法 ,证明格式按离散 H1范数是绝对稳定的 ,并且收敛阶为 O(Δ t2 + h2 ) 相似文献
4.
5.
6.
Tang Rongqing Wang Daoyan Zhang Xixian Egnineer Shanghai Jiao Tong University Shanghai Associate Professor Shanghai Jiao University Shanghai 《中国海洋工程》1993,(3)
- The authors have used a low-cost ROV of observation type for underice surveying of the Nen-Jiang Cross-river oil pipe line in the Da Qing oil field. The operation method, process and the safety measures for severe cold areas are presented. The fruitful tries and experience may be useful to ROV operators in severe cold areas. 相似文献
7.
从高压水射流技术在水下工程中应用及高压水射流的作用效应和伤害特征着手,分析影响水下高压水射流作业安全的因素,总结各国制订高压水射流作业的安全标准规程现状,提出制订我国水下高压水射流作业安全规程若干认识和设想。 相似文献
8.
1 .IntroductionTomeasurethereflectionofincidentwavesproducedbyaphysicalmodelinawaveflumeisacommonproblemwithphysicaltestsofwaveactiononcoastalstructures .Wavesgeneratedbythewave makerpropagateforwardinthewaveflumeandarereflectedbythephysicalmodel,andthe… 相似文献
9.
Presented here is a compact explicit difference scheme of high accuracy for solving the extended Boussinesq equations.For time discretization,a three-stage explicit Runge-Kutta method with TVD property is used at predicting stage,a cubic spline function is adopted at correcting stage,which made the time discretization accuracy up to fourth order;For spatial discretization,a three-point explicit compact difference scheme with arbitrary order accuracy is employed.The extended Boussinesq equations derived by Beji and Nadaoka are solved by the proposed scheme.The numerical results agree well with the experimental data.At the same time,the comparisons of the two numerical results between the present scheme and low accuracy difference method are made,which further show the necessity of using high accuracy scheme to solve the extended Boussinesq equations.As a valid sample,the wave propagation on the rectangular step is formulated by the present scheme,the modelled results are in better agreement with the experimental data than those of Kittitanasuan. 相似文献
10.
The Princeton Ocean Model with realistic bottom topography has been used to investigate the summer temperature decrease in
the past 25 years in Fukuoka Bay. The vertical mixing of the model is expressed by a scheme that effectively includes the
influences of interannual variations of tidal currents and wind. The results show that the historical temperature decrease
in summer has been caused by tidal currents and wind weakening in the past 25 years in Fukuoka Bay. The weakening of tidal
currents and wind gives rise to weakening of the vertical mixing, and to enhancement of the estuarine circulation in the bay.
The enhancement of the estuarine circulation activates the inflow of open-ocean water toward Fukuoka Bay. Coastal water in
summer has therefore tended to be colder and more saline in the past 25 years. This interannual variation in coastal waters
is called “open-oceanization” in this study. On the basis of the numerical model, it is anticipated that the temperature will
decrease by 0.2°C in the next 25 years in Fukuoka Bay if the tide and wind weaken persistently as in the present bay. 相似文献