全文获取类型
收费全文 | 29298篇 |
免费 | 5537篇 |
国内免费 | 8115篇 |
专业分类
测绘学 | 4425篇 |
大气科学 | 4970篇 |
地球物理 | 6593篇 |
地质学 | 15871篇 |
海洋学 | 4406篇 |
天文学 | 316篇 |
综合类 | 2261篇 |
自然地理 | 4108篇 |
出版年
2024年 | 129篇 |
2023年 | 391篇 |
2022年 | 1066篇 |
2021年 | 1218篇 |
2020年 | 1394篇 |
2019年 | 1664篇 |
2018年 | 1349篇 |
2017年 | 1512篇 |
2016年 | 1648篇 |
2015年 | 1776篇 |
2014年 | 1950篇 |
2013年 | 2161篇 |
2012年 | 2025篇 |
2011年 | 2137篇 |
2010年 | 1714篇 |
2009年 | 1926篇 |
2008年 | 1930篇 |
2007年 | 1965篇 |
2006年 | 1952篇 |
2005年 | 1708篇 |
2004年 | 1500篇 |
2003年 | 1327篇 |
2002年 | 1218篇 |
2001年 | 994篇 |
2000年 | 962篇 |
1999年 | 841篇 |
1998年 | 790篇 |
1997年 | 691篇 |
1996年 | 589篇 |
1995年 | 531篇 |
1994年 | 463篇 |
1993年 | 388篇 |
1992年 | 246篇 |
1991年 | 200篇 |
1990年 | 139篇 |
1989年 | 102篇 |
1988年 | 106篇 |
1987年 | 60篇 |
1986年 | 43篇 |
1985年 | 42篇 |
1984年 | 25篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1954年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
231.
At the circular Babi Island in the Flores tsunami (1992) and pear shaped island in the Okushiri event (1993), unexpectedly large tsunami run‐up heights in the lee of conic islands were observed. The flume and basin physical model studies were conducted in the Coastal Hydraulic Laboratory, Engineering Research and Development Center, U.S. Army Corps of Engineers to provide a better understanding of the physical phenomena and verify numerical models used in predicting tsunami wave run‐up on beaches, islands, and vertical walls. Reasonably accurate comparison of run‐up height of solitary waves on a circular island has been obtained between laboratory experimental results and two‐dimensional computation model results. In this study we apply three‐dimensional RANS model to simulate wave run‐up on conical island. In the run‐up computation we obtain that 3D calculations are in very good comparison with laboratory and 2D numerical results. A close examination of the three‐dimensional velocity distribution around conical island to compare with depth‐integrated model is performed. It is shown that the velocity distribution along the vertical coordinate is not uniform: and velocity field is weaker in the bottom layer and higher on the sea surface. The maximum difference (about 40%) appears at the time when solitary wave reached the circular island. 相似文献
232.
东海陆架盆地与松辽盆地的类比分析 总被引:3,自引:0,他引:3
陈建文 《海洋地质与第四纪地质》1994,14(3):19-32
松辽盆地在我国的含油气盆地中勘探程度较高,已探明了几十亿吨的地质储量,对控制盆地油气形成的生、储、盖、圈、运、保等条件的研究也比较深入和细致,东海陆架盆地是我国目前勘探程度较低却有很大油气远景的盆地,这两个盆地都是我国东部中新生代大型复合沉积盆地,在地质构造上具有一定的相似性。本文试图通过东海陆架盆地与松辽盆地的对比在研究它们各自特征的基础上,寻找这两个大型沉积盆地的共同点和相似性,以便借鉴松辽盆 相似文献
233.
234.
235.
黄海地质构造与油气资源 总被引:13,自引:4,他引:13
概述了南,北黄海盆地地质构造特征,盆地的形成与演化,分析研究了油气地质特征与成藏条件;对黄海各盆地和隆起区可能具有找油气远景的新领域,新层位和新类型,提出一些探讨性的认识。 相似文献
236.
C. Kranenburg 《Applied Ocean Research》1984,6(1):23-30
The rupture of a submarine oil pipeline starts various mechanisms leading to an oil spill. Among these mechanisms the leakage of oil driven by the difference in specific gravities of oil and sea-water is difficult to estimate. A simple mathematical model has been developed and laboratory experiments have been carried out to obtain an insight into the density-driven exchange flow and to determine the leak rate. The mathematical model is predictive and takes account of the effects of friction, inclination of the pipeline, and inertia of the fluid. The experiments were done in a horizontal model pipeline. Theoretical and experimental results are in satisfactory agreement. 相似文献
237.
AbstractWith the large-scale development and utilization of ocean resources and space, it is inevitable to encounter existing submarine facilities in pile driving areas, which necessitates a safety assessment. In this article, by referring to a wharf renovation project as a reference, the surrounding soil response and buried pipe deformation during pile driving in a near-shore submarine environment are investigated by three-dimensional (3D) numerical models that consider the pore water effect. Numerical studies are carried out in two different series: one is a case of a single pile focusing on the effect of the minimum plane distance of the pile–pipe, and the other is a case of double piles focusing on the effect of the pile spacing. 相似文献
238.
Abstract. The marine plant communities of the littoral zone in different biotopes of the Greek coasts were investigated in 1980-81. Seasonal distribution and variation of marine plant biomass were assessed. The communities of Cystoseira crinita and C. compressa were outstanding with maximum biomass during the summer months. Corallina officinalis and Pterocladia capillacea + Viva rigida communities predominated with maximum biomass in autumn and exhibited a decrease in winter, except in stressed biotopes. The species diversity and productivity of seaweeds along the Greek coasts are interpreted in relation to a number of environmental parameters. 相似文献
239.
B. Gjevik D. Hareide B. K. Lynge A. Ommundsen J. H. Skailand H. B. Urheim 《Marine Geodesy》2006,29(1):1-17
A system for displaying tidal currents in an electronic chart display and information system (ECDIS) has been developed and implemented in compliance with the standards of the International Hydrographic Organization (IHO). The tidal current fields can be displayed in real time on the electronic navigational chart and several options and functions for updating and zooming have been designed. The current fields are calculated from a data base with the harmonic constants for the four major tidal constituents. The harmonic constants are obtained from a high resolution numerical model with horizontal grid resolution of 100 m. The model is validated by comparing with sea level and current measurements. The depth matrix for the central part of the model domain was calculated from data from multibeam bathymetric surveys. An application example of the implementation is given for Trondheimsleia, a part of the main sailing route along the western coast of Norway. 相似文献
240.
I. Brandariz P. Castro M. Montes F. Penedo M.E. Sastre de Vicente 《Marine Chemistry》2006,102(3-4):291-299
Acid–base equilibrium constants of triethanolamine (TEA) have been determined by potentiometric titrations with a glass electrode, at 25 °C. Ionic strength was kept constant with only one electrolyte (using one of these salts: NaCl, KCl, MgCl2 or CaCl2), with binary mixtures of MgCl2 and CaCl2, and finally, in a solution with a composition approximately similar to that of natural seawater without sulfate. Equilibrium constants have been expressed in function of ionic strength by means of Pitzer equations and interaction parameters proposed in this theory have been obtained. It has been found that acid–base behaviour of TEA depends greatly on the salt used: basicity of TEA is decreased by CaCl2, while it is increased by the other electrolytes used in this work. 相似文献