全文获取类型
收费全文 | 30223篇 |
免费 | 5581篇 |
国内免费 | 8479篇 |
专业分类
测绘学 | 4435篇 |
大气科学 | 6108篇 |
地球物理 | 6977篇 |
地质学 | 13215篇 |
海洋学 | 5961篇 |
天文学 | 1372篇 |
综合类 | 2312篇 |
自然地理 | 3903篇 |
出版年
2024年 | 131篇 |
2023年 | 377篇 |
2022年 | 1004篇 |
2021年 | 1184篇 |
2020年 | 1382篇 |
2019年 | 1639篇 |
2018年 | 1347篇 |
2017年 | 1504篇 |
2016年 | 1559篇 |
2015年 | 1745篇 |
2014年 | 1985篇 |
2013年 | 2173篇 |
2012年 | 2046篇 |
2011年 | 2124篇 |
2010年 | 1732篇 |
2009年 | 2038篇 |
2008年 | 2012篇 |
2007年 | 2237篇 |
2006年 | 2085篇 |
2005年 | 1799篇 |
2004年 | 1684篇 |
2003年 | 1439篇 |
2002年 | 1274篇 |
2001年 | 1056篇 |
2000年 | 1000篇 |
1999年 | 918篇 |
1998年 | 856篇 |
1997年 | 709篇 |
1996年 | 609篇 |
1995年 | 560篇 |
1994年 | 497篇 |
1993年 | 407篇 |
1992年 | 267篇 |
1991年 | 236篇 |
1990年 | 142篇 |
1989年 | 118篇 |
1988年 | 107篇 |
1987年 | 68篇 |
1986年 | 38篇 |
1985年 | 45篇 |
1984年 | 24篇 |
1983年 | 16篇 |
1982年 | 22篇 |
1981年 | 19篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1976年 | 10篇 |
1973年 | 5篇 |
1954年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
231.
An Ecosystem Model Coupled with Nitrogen-Silicon-Carbon Cycles Applied to Station A7 in the Northwestern Pacific 总被引:1,自引:0,他引:1
Yasuhiro Yamanaka Naoki Yoshie Masahiko Fujii Maki N. Aita Michio J. Kishi 《Journal of Oceanography》2004,60(2):227-241
A model based on that of Kishi et al. (2001) has been extended to 15 compartments including silicon and carbon cycles. This model was applied to Station A7 off
Hokkaido, Japan, in the Northwestern Pacific. The model successfully simulated the observations of: 1. a spring bloom of diatoms;
2. large seasonal variations of nitrate and silicate concentrations in the surface water; and 3. large inter-annual variations
in chlorophyll-a. It also reproduced the observed features of the seasonal variations of carbon dioxide partial pressure (pCO2)—a peak in pCO2 in winter resulting from deep winter convection, a rapid decrease in pCO2 as a result of the spring bloom, and an almost constant pCO2 from summer through fall (when the effect of increasing temperature cancels the effect of biological production). A comparison
of cases with and without silicate limitation shows that including silicate limitation in the model results in: 1. decreased
production by diatoms during summer; and 2. a transition in the dominant phytoplankton species, from diatoms to other species
that do not take up silicate. Both of these phenomena are observed at Station A7, and our results support the hypothesis that
they are caused by silicate limitation of diatom growth.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
232.
233.
1 .IntroductionUnder the influence of surface waves ,sandripples often appear on beaches . Whenthe amplitudeof water oscillationis sufficientlylarge ,vortices are formed onthe lee of every sand ripple crest . A-mongthese vortices ,the most important are t… 相似文献
234.
Using a two-dimensional primitive equation model, we examine nonlinear responses of a semidiurnal tidal flow impinging on
a seamount with a background Garrett-Munk-like (GM-like) internal wavefield. It is found that horizontally elongated pancake-like
structures of high vertical wavenumber near-inertial current shear are created both in the near-field (the region over the
slope of the seamount) and far-field (the region over the flat bottom of the ocean). An important distinction is that the
high vertical wavenumber near-inertial current shear is amplified only at mid-latitudes in the far-field (owing to a parametric
subharmonic instability (PSI)), whereas it is amplified both at mid-and high-latitudes (above the latitude where PSI can occur)
in the near-field. In order to clarify the generating mechanism for the strong shear in the near-field, additional numerical
experiments are carried out with the GM-like background internal waves removed. The experiments show that the strong shear
is also created, indicating that it is not caused by the interaction between the background GM-like internal waves and the
semidiurnal internal tides. One possible explanation is proposed for the amplification of high vertical wavenumber near-inertial
current shear in the near-field where tide residual flow resulting from tide-topography interaction plays an important role
in transferring energy from high-mode internal tides to near-inertial internal waves. 相似文献
235.
236.
237.
砂质海岸岸滩侵蚀演变模式探讨——以山东南部海岸侵蚀岸段的岸滩演变为例 总被引:5,自引:0,他引:5
在分析山东南部海岸几十年来的地形观测资料的基础上,运用砂质海岸等深线变化预测理论,建立该区的岸滩侵蚀演变预测模型,研究了该区域岸滩演变规律。实测资料验证表明:预测结果合理,基本反映了本区岸滩演变的特征。 相似文献
238.
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
239.
240.