全文获取类型
收费全文 | 5991篇 |
免费 | 1596篇 |
国内免费 | 2669篇 |
专业分类
测绘学 | 522篇 |
大气科学 | 4974篇 |
地球物理 | 1442篇 |
地质学 | 1303篇 |
海洋学 | 827篇 |
天文学 | 249篇 |
综合类 | 310篇 |
自然地理 | 629篇 |
出版年
2024年 | 44篇 |
2023年 | 129篇 |
2022年 | 204篇 |
2021年 | 281篇 |
2020年 | 333篇 |
2019年 | 384篇 |
2018年 | 264篇 |
2017年 | 306篇 |
2016年 | 313篇 |
2015年 | 350篇 |
2014年 | 488篇 |
2013年 | 500篇 |
2012年 | 501篇 |
2011年 | 483篇 |
2010年 | 394篇 |
2009年 | 528篇 |
2008年 | 501篇 |
2007年 | 596篇 |
2006年 | 526篇 |
2005年 | 417篇 |
2004年 | 407篇 |
2003年 | 325篇 |
2002年 | 254篇 |
2001年 | 240篇 |
2000年 | 225篇 |
1999年 | 187篇 |
1998年 | 166篇 |
1997年 | 156篇 |
1996年 | 140篇 |
1995年 | 108篇 |
1994年 | 121篇 |
1993年 | 91篇 |
1992年 | 59篇 |
1991年 | 63篇 |
1990年 | 31篇 |
1989年 | 31篇 |
1988年 | 28篇 |
1987年 | 18篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1954年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
This study is devoted to oceanographic features of the semi-enclosed Gulf of Aqaba, Red Sea. The data were recorded in winter—spring
1999 on the R/V Meteor cruise leg 44/2. Temperature and salinity profiles were measured at six positions (I—VI). The shipboard
NarrowBand Acoustic Doppler Current Profiler (NB ADCP) 150 kHz continuously recorded current profiles down to 350 m en route.
The research revealed that the current near the Strait of Tiran front (position VI) represents a semidiurnal signal of an
internal tide wave (∼12 h period; 0.2 ms−1 amplitude) that might be generated by the barotropic tide at the sill of the Strait. A sequence of cyclonic and anticyclonic
eddy pairs is found along the axis of the Gulf of Aqaba during winter-spring seasons. These sub-mesoscale signals are dominant
above the main thermocline and might be caused by wind forcing and the narrowness of the Gulf; it might remain in other seasons
with different dimensions in relation to the depth of thermocline. The total diameter of each pair was twice the baroclinic
Rossby radius (R ≈ 10 km). A single anti-cyclonic eddy was observed in the upper 300 m in the northern tip of the Gulf with a diameter of
about 5–8 km. 相似文献
32.
我国的渤海和黄海北部在每年冬季都出现不同程度的冰情,它直接影响结冰海区的石油平台、船舶以及港口等设施的正常作业,对海冰的观测与预报随着上述海区的开发利用越发显得重要,利用航海雷达连续准确地跟踪海冰漂移运动轨迹,是当今观测、调查、研究冰漂流移动规律的有效方法之一,我国的科研人员利用雷达成像技术对渤海的冰情进行了长期的雷达海冰观测、研究,在由雷达海冰图像对海冰的物理特征的识别、分类以及冰漂流场测量方面取得了一些进展[1-4]。 相似文献
33.
A coding error in the s-Coordinate Primitive Equation Model (SPEM) has led to misleading statements about the behaviour of the Mellor–Yamada level 2 parameterization of vertical mixing. It has been claimed that the scheme removes static instability only very slowly and preserves statically unstable stratifications for an unrealistic long time. This note corrects this statement by demonstrating that the Mellor–Yamada mixing scheme, if implemented correctly, tends to overestimate rather than underestimate vertical mixing in seasonally ice-covered seas. Similar to other mixing schemes with the same behaviour, this leads to spurious open ocean deep convection, an unrealistic homogenization of the water column, and a significant reduction of sea ice volume. 相似文献
34.
From the experimental studies in recent years, it has become known that when a wave breaks directly on a vertical faced coastal structure, high magnitude impact pressures are produced. The theoretical and experimental studies show that the dynamic response of such structures under wave impact loading is closely dependent on the magnitude and duration of the load history. The dynamic analysis and design of a coastal structure can be succeeded provided the design load history for the wave impact is available. Since these types of data are very scarce, it is much more convenient to follow a method which is based on static analysis for the dynamic design procedure. Therefore, to facilitate the dynamic design of a vertical plate that is exposed to breaking wave impact, a multiplication factor called “dynamic magnification factor” is herein presented which is defined as the ratio of the maximum value of the dynamic response to that found by static analysis. The computational results of the present study show that the dynamic magnification factor is a useful ratio to transfer the results of static analysis to the dynamic design of a coastal plate for the maximum impact pressure conditions of pmax/γH0≤18. 相似文献
35.
36.
37.
38.
A Computational Model for Velocity Separation in Shallow Sea 总被引:1,自引:0,他引:1
Based on the hydrodynamical feature and the theoretical velocity profiles of tidal flow and vvind-induced flow in shal-low sea, a computational model is established for the first time, which can separate observed velocity into tidal velocity and wind-induced velocity by use of the least square method. With the model, not only the surface velocities of tidal flow and vvind-induced flow are obtained, but also the bed roughness height is determined and the wind velocity above the wa-ter surface is estimated. For verification of the model, the observed velocity in the Yellow River Estuary and the laborato-ry test is separated, then it is applied to the Yangtze River Estuary. All the results are satisfactory. The research results show that the model is simple in method, feasible in process and reasonable in result. The model is a valid approach to analysis and computation of field dala, and can be applied to separate the observed velocity in shallow sea; at the same time, reasonable boundary conditions of th 相似文献
39.
采用TOGA/COARE国际合作考察期间(1992年10月─1993年2月)获得的267次定点(2°S,155°E)定时高空大气探测资料,进行计算分析,发现1992年12月─1993年2月低空存在一支西风急流,有两次分别持续半月之久,而1992年11月的两次赤道西风急流,因无赤道高空急流配合,仅持续2d便消失。本文还指出:(1)赤道低空西风急流是各种海-气指数产生ENSO异常的重要信息;(2)赤道高空急流有滞后赤道低空急流2d左右的响应关系;(3)赤道低空急流是纬向水汽输送的狭窄通道。 相似文献
40.