全文获取类型
收费全文 | 61562篇 |
免费 | 14719篇 |
国内免费 | 22884篇 |
专业分类
测绘学 | 10907篇 |
大气科学 | 8472篇 |
地球物理 | 11646篇 |
地质学 | 41861篇 |
海洋学 | 11734篇 |
天文学 | 872篇 |
综合类 | 5086篇 |
自然地理 | 8587篇 |
出版年
2024年 | 740篇 |
2023年 | 2004篇 |
2022年 | 3990篇 |
2021年 | 4696篇 |
2020年 | 3906篇 |
2019年 | 4494篇 |
2018年 | 4000篇 |
2017年 | 3806篇 |
2016年 | 3933篇 |
2015年 | 4472篇 |
2014年 | 4313篇 |
2013年 | 5053篇 |
2012年 | 5622篇 |
2011年 | 5520篇 |
2010年 | 5521篇 |
2009年 | 5067篇 |
2008年 | 5161篇 |
2007年 | 4843篇 |
2006年 | 4539篇 |
2005年 | 3885篇 |
2004年 | 2958篇 |
2003年 | 2022篇 |
2002年 | 2089篇 |
2001年 | 1908篇 |
2000年 | 1578篇 |
1999年 | 803篇 |
1998年 | 364篇 |
1997年 | 224篇 |
1996年 | 203篇 |
1995年 | 162篇 |
1994年 | 130篇 |
1993年 | 143篇 |
1992年 | 144篇 |
1991年 | 92篇 |
1990年 | 107篇 |
1989年 | 68篇 |
1988年 | 56篇 |
1987年 | 49篇 |
1986年 | 59篇 |
1985年 | 54篇 |
1984年 | 56篇 |
1983年 | 38篇 |
1982年 | 32篇 |
1981年 | 28篇 |
1979年 | 34篇 |
1978年 | 21篇 |
1977年 | 15篇 |
1976年 | 15篇 |
1957年 | 19篇 |
1954年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
141.
Up to now, available method of numerical forecasting and suitable wind field model for the Bohai Sea storm surge have been few. In this paper, through the analysis of the weather situation is presented a mathematical model for the wind fields involved mainly the deformation field of a high pressure matched with a low pressure, the temperate cyclone, the cold wave and the northword typhoon. Meanwhile, numerical computations combined with the nonlinear storm surge models are made by using "ADI" method. The computed results are generally coincident with the practical observations. It has showed a success in the simulated wind field and the feasibility of using "ADI" method to forecast the Bohai Sea storm surge. 相似文献
142.
143.
144.
Samples of O isotopic tracer were mlleMed at Sections P3,P25,PcM-t/2-E and PCM-1/2.w in both the Fast China Sea and the area to the east of the Ryūkyū-gunto during October-November,1991.Analytical results of the δ18O are as follows: (1) In the Kuroshio area,the δ18O isolines are almost parallel to the 200 m isobath.The value of δ18O is negative and reaches minimum mt the main axis of the Kuroshio,and increases on both sides.(2) In the Taiwan Warm Current (TWC) area there is a high δ18O tongue extending to the northeast.(3) In the area near the coast,the distribution of δ18O isoline shows that the Changjiang River runoff diffuses seaward and the land-ocean isotopic effect from the nearshore to the offshore.(4) The values of δ18O are from -1.0×10-3 to -0.5×10-3 in the shelf.(5) There is a low mre of δ18O value(<-1.6×10-3) at the 600 m layer in the Kuroshio area,which is quite in accord with the existence of a low salinity mre (S G 34.30) between the 600 and 800 m layers in the same area.Finally,the mrrelations of the δ18O with the salinity and temperature,the upwelling and so on are discussed. 相似文献
145.
The study of the Kuroshio in the East China Sea and the currents east of the Ryukyu Islands 总被引:3,自引:0,他引:3
In this study, the inverse method is used to compute the Kuroshio in the East China Sea and southeast of Kyushu and the currents east of the Ryukyu Islands, on the basis of hydrographic data obtained during September-October, 1987 by R/V Chofu Maru. The results show that: (1)A part of the Taiwan Warm Current has a tendency to converge to the shelf break; (2) the Kuroshio flows across the section C3 (PN) with a reduced current width, and the velocity of the Kuroshio at the section C3 increases and its maximum current speed is about 158 cm/s, and its volume transport here is about 26×106m3/s; (3) the Kuroshio has two current cores at the sections C3 (PN) and B2 (at the Tokara Strait); (4) the currents east of the Ryukyu Islands are found to flow northward over the Ryukyu Trench during September-October, 1987. The velocities of the currents are not strong throughout the depths. At the section C2 east of the Ryukyu Islands, the maximum current speed is at the 699 m levei and its magnitude is 25 cm/s, and i 相似文献
146.
Using 203HgCl2 as a tracer, uptake and combination of inorganic mercury in Tilapia mossambica (petres) and its transfer between different tissues of the fish were studied. The results demonstrate that gill is the main tissue uptaking mercury directly from seawater and that the mercury in gill, skin, digestive tube and fin would be transferred to the other tissues. The result of gel chromatography with Sephadex G-75 shows that most of mercury in gill filaments, liver, and digestive tube are bound in high molecules (MW-70000) and not in metallothionein, but in kidney and bile mercury binding proteins are similar to metallothionein and are accounted for up to 60% and 46% respectively. 相似文献
147.
Based on the shear effect of internal wave currents in stratified fluid, the necessary condition for the possible existence of an internal wave and the sufficient condition under which there will be no internal wave are deduced starting from the continuity equation of incompressible fluid. The above two conditions are verified by the measured results from vertical current meter arraies at some observation stations in the Bohai Sea and the South Huanghai Sea. In the treatment of measured results, first of all, the tidal period components are separated from the measured currents by Fourier-analysis method, and then the internal wave currents of tidal period from the tidal period components in the light of some considerations. The analytical results of observed currents are well consistent with theoretical analysis. Furthermore, one can also deduce some features of internal waves therefrom. Consequently, it is concluded that the observation from a vertical current meter array is an important means to verif 相似文献
148.
A new approach to high-order Boussinesq-type equations with ambient currents is presented. The current velocity is assumed to be uniform over depth and of the same magnitude as the shallow water wave celerity. The wave velocity field is expressed in terms of the horizontal and vertical wave velocity components at an arbitrary water depth level. Linear operators are introduced to improve the accuracy of the kinematic condition at the sea bottom. The dynamic and kinematic conditions at the free surface are expressed in terms of wave velocity variables defined directly on the free surface. The new equations provide high accuracy of linear properties as well as nonlinear properties from shallow to deep water, and extend the applicable range of relative water depth in the case of opposing currents. 相似文献
149.
150.