全文获取类型
收费全文 | 3779篇 |
免费 | 507篇 |
国内免费 | 688篇 |
专业分类
测绘学 | 921篇 |
大气科学 | 275篇 |
地球物理 | 913篇 |
地质学 | 1008篇 |
海洋学 | 1155篇 |
天文学 | 84篇 |
综合类 | 390篇 |
自然地理 | 228篇 |
出版年
2024年 | 20篇 |
2023年 | 54篇 |
2022年 | 108篇 |
2021年 | 131篇 |
2020年 | 156篇 |
2019年 | 188篇 |
2018年 | 118篇 |
2017年 | 162篇 |
2016年 | 163篇 |
2015年 | 186篇 |
2014年 | 227篇 |
2013年 | 248篇 |
2012年 | 268篇 |
2011年 | 258篇 |
2010年 | 179篇 |
2009年 | 178篇 |
2008年 | 185篇 |
2007年 | 245篇 |
2006年 | 203篇 |
2005年 | 221篇 |
2004年 | 177篇 |
2003年 | 169篇 |
2002年 | 131篇 |
2001年 | 127篇 |
2000年 | 120篇 |
1999年 | 102篇 |
1998年 | 77篇 |
1997年 | 93篇 |
1996年 | 75篇 |
1995年 | 75篇 |
1994年 | 90篇 |
1993年 | 59篇 |
1992年 | 45篇 |
1991年 | 26篇 |
1990年 | 17篇 |
1989年 | 19篇 |
1988年 | 24篇 |
1987年 | 17篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 3篇 |
1954年 | 1篇 |
排序方式: 共有4974条查询结果,搜索用时 15 毫秒
21.
赤潮生物种类特征光谱获取技术 总被引:1,自引:0,他引:1
较为系统地研究了赤潮生物水体反射率曲线获取方法。通过对 2类反射率反演方法得出的反射率曲线与实际反射率曲线进行比较 ,得出在不具备大气环境参数的情况下 ,经验线性法的反演结果与实际反射率曲线最接近的结论 ,并进一步对正常海水和赤潮生物水体的光谱特性进行分析 ,提取出赤潮生物水体的特征光谱。这是进行赤潮监测和识别的重要前提 相似文献
22.
23.
24.
虾塘赤潮灾害的防治对策 总被引:2,自引:1,他引:2
本文报道了一次虾塘赤潮的防治过程,结合国内外有关赤潮防治的动态和作者的经验,提出了一些为避免虾塘内发生赤潮的防治对策。 相似文献
25.
Domenico Voltolina Leslie N. Brown Maurice G. Robinson 《Estuarine, Coastal and Shelf Science》1985,21(6):817-822
The results of eight sets of repeated observations on the vertical variations of the chlorophyll maximum layer in a shallow lagoon during a red tide show that these were more frequently hydrologically induced, rather than due to active vertical migrations of the red tide-forming organism. These results are discussed and compared to those existing in the literature, with special regard to the role of light and nitrogen in conditioning vertical migrations in red tide-forming dinoflagellates. 相似文献
26.
Gene specific primers and DNA probe were designed based on the sequence of 18S rDNA cloned from the red tide alga Thalassiosira rotula. A real-time fluorescent quantitative PCR (RFQ-PCR) method was developed for quantitative detection of T.rotula. The RFQ-PCR assay data showed that the results obtained with the RFQ-PCR quite good agreement with those with the light microscope (LM) counting method, which suggested that the RFQ-PCR could be a useful method for red tide alga detection. 相似文献
27.
We use a synthetic data experiment to assess the accuracy of ocean tides estimated from satellite altimetry data, with emphasis on the impact of the phase-locked internal tide, which has a surface expression of several centimeters near its sites of genesis. Previous tidal estimates have regarded this signal as a random measurement error; however, it is deterministic and not scale-separated from the barotropic (surface) tide around complex bathymetric features. The synthetic data experiments show that the internal tide has a negligible impact on the barotropic tidal fields inferred under these circumstances, and the barotropic dissipation (a quadratic functional of the tidal fields) is in good agreement with the energetics of the three-dimensional regional primitive equations model which is the source of the synthetic data. 相似文献
28.
Shigenao Maruyama Koutaro Tsubaki Keisuke Taira Seigo Sakai 《Journal of Oceanography》2004,60(3):563-568
Deep seawater in the ocean contains a great deal of nutrients. Stommel et al. have proposed the notion of a “perpetual salt fountain” (Stommel et al., 1956). They noted the possibility of a permanent upwelling of deep seawater with no additional external energy source. If
we can cause deep seawater to upwell extensively, we can achieve an ocean farm. We have succeeded in measuring the upwelling
velocity by an experiment in the Mariana Trench area using a special measurement system. A 0.3 m diameter, 280 m long soft
pipe made of PVC sheet was used in the experiment. The measured data, a verification experiment, and numerical simulation
results, gave an estimate of upwelling velocity of 212 m/day.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
29.
波浪波形的非接触测量近年来获得广泛的应用。本文以规则波为讨论对象,针对介质为空气的超声波测量方式进行波形测量误差分析,并结合实验室和实船试验进行对比分析。理论分析表明:在规则波取为坦谷波和STOKES波的前提下,超声波技术几乎产生相同的最大误差。定量分析表明,在对测量精度限制的条件下,对文中提及的各项参数应作有效的控制 相似文献
30.
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