全文获取类型
收费全文 | 66562篇 |
免费 | 1041篇 |
国内免费 | 595篇 |
专业分类
测绘学 | 1573篇 |
大气科学 | 4325篇 |
地球物理 | 12956篇 |
地质学 | 23958篇 |
海洋学 | 6104篇 |
天文学 | 15932篇 |
综合类 | 150篇 |
自然地理 | 3200篇 |
出版年
2022年 | 458篇 |
2021年 | 737篇 |
2020年 | 846篇 |
2019年 | 871篇 |
2018年 | 1875篇 |
2017年 | 1741篇 |
2016年 | 2052篇 |
2015年 | 1077篇 |
2014年 | 1947篇 |
2013年 | 3508篇 |
2012年 | 2129篇 |
2011年 | 2814篇 |
2010年 | 2505篇 |
2009年 | 3307篇 |
2008年 | 2784篇 |
2007年 | 2841篇 |
2006年 | 2646篇 |
2005年 | 1835篇 |
2004年 | 1808篇 |
2003年 | 1700篇 |
2002年 | 1661篇 |
2001年 | 1505篇 |
2000年 | 1417篇 |
1999年 | 1190篇 |
1998年 | 1227篇 |
1997年 | 1172篇 |
1996年 | 1016篇 |
1995年 | 986篇 |
1994年 | 937篇 |
1993年 | 781篇 |
1992年 | 747篇 |
1991年 | 747篇 |
1990年 | 845篇 |
1989年 | 674篇 |
1988年 | 654篇 |
1987年 | 812篇 |
1986年 | 666篇 |
1985年 | 883篇 |
1984年 | 916篇 |
1983年 | 875篇 |
1982年 | 814篇 |
1981年 | 766篇 |
1980年 | 702篇 |
1979年 | 641篇 |
1978年 | 655篇 |
1977年 | 564篇 |
1976年 | 565篇 |
1975年 | 565篇 |
1974年 | 536篇 |
1973年 | 564篇 |
排序方式: 共有10000条查询结果,搜索用时 851 毫秒
901.
Methods are described for estimating the parameters of the Fisher-Tippet Type 1 extreme value distribution and associated return values from measured extremes, such as maximum wave height. A comparison of these methods, with simulated data, shows that those using Gumbel's plotting position are least satifactory. Maximum likelihood methods give the smallest mean square errors, but the very much simpler method of moments is nearly as good. 相似文献
902.
Validation of the stochastic distorted-wave Born approximation model with broad bandwidth total target strength measurements of Antarctic krill 总被引:2,自引:0,他引:2
In the computations of SDWBATTS(f) in Figure 4, the scatteredvector was integrated over all orientations in the XY plane,where X is the main axis of the krill, but a factor of 2 was 相似文献
903.
904.
The concentrations of a number of trace metals (Co, Ni, Cu, Zn, Ag, Cd and Hg) have been determined in sediments from cores collected in the Southampton Water region. Measurements of total hydrocarbons were also made on several of the cores. Markedly elevated concentrations of copper, up to 362 μg/g dry wt, were found in sediments which were collected close to the discharge points of oil refinery outfalls and which also showed concentrations of total hydrocarbons considerably greater than the background levels for the estuary. The results of selective chemical extractions showed that much of the copper was present in the non-lattice fraction of the sediment. Although the concentrations of Co, Ni, Zn and Cd were significantly correlated with those of copper in the core showing the highest concentrations of this element, these metals were not enhanced in comparison with the levels found in several other parts of the estuary. Variations in concentrations of metals in sediments throughout the estuary were not correlated with differences in organic carbon content. 相似文献
905.
The ICES North Sea benthos survey: the sedimentary environment 总被引:2,自引:1,他引:2
906.
907.
A.G. Abul-Azm 《Ocean Engineering》1996,23(5):403-422
This paper presents an analytical, computationally efficient method for the wave reflection and dynamic displacement of a submerged flexible breakwater. The solution of the two-dimensional linearized hydrodynamic problem introduced is based on the eigenfunction expansion technique. The breakwater is assumed to be thin, impermeable, flexible, moored to the bed through tethers and kept in tension by means of a floating buoy at its tip. The beam structure is considered to be either clamped or hinged at the sea bed, situated in an arbitrary water depth and subjected to normal linear waves. Numerical examples presented by this method are compared with those obtained by the Boundary Integral Equation Method, presented by Williams et al. Comparisons show an excellent agreement over a wide range of parameters for the wave reflection and the dynamic displacement. Numerical results are presented, mainly to show the effect of the breakwater rigidity and the method of fixation on the wave reflection and the structural displacement over a wide range of wave frequencies. 相似文献
908.
909.
910.
This paper considers the relationship between multi-year air temperature and pressure fluctuations over the ocean, based on an approximate solution of the problem on the determination of large-scale seawater temperature anomalies from the conditions predominating at the sea surface. The dependence derived is numerically analysed using observations made in the North Atlantic. It is shown that the variability of annual mean air temperature anomalies is largely controlled by the air pressure field which has taken place during the preceding long-term period. The dependence derived may be applied to generate long-term forecasts of the ocean's hydrometeorological regime.Translated by Vladimir A. Puchkin. 相似文献