全文获取类型
收费全文 | 3478篇 |
免费 | 624篇 |
国内免费 | 775篇 |
专业分类
测绘学 | 231篇 |
大气科学 | 680篇 |
地球物理 | 923篇 |
地质学 | 1630篇 |
海洋学 | 504篇 |
天文学 | 186篇 |
综合类 | 296篇 |
自然地理 | 427篇 |
出版年
2024年 | 19篇 |
2023年 | 63篇 |
2022年 | 192篇 |
2021年 | 214篇 |
2020年 | 180篇 |
2019年 | 214篇 |
2018年 | 237篇 |
2017年 | 191篇 |
2016年 | 233篇 |
2015年 | 162篇 |
2014年 | 223篇 |
2013年 | 210篇 |
2012年 | 202篇 |
2011年 | 172篇 |
2010年 | 187篇 |
2009年 | 169篇 |
2008年 | 166篇 |
2007年 | 184篇 |
2006年 | 117篇 |
2005年 | 118篇 |
2004年 | 98篇 |
2003年 | 87篇 |
2002年 | 96篇 |
2001年 | 107篇 |
2000年 | 105篇 |
1999年 | 151篇 |
1998年 | 85篇 |
1997年 | 99篇 |
1996年 | 85篇 |
1995年 | 78篇 |
1994年 | 61篇 |
1993年 | 69篇 |
1992年 | 43篇 |
1991年 | 37篇 |
1990年 | 28篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1986年 | 25篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1974年 | 3篇 |
排序方式: 共有4877条查询结果,搜索用时 15 毫秒
41.
42.
43.
Two numerical studies (Endoh, 1977;Harashima
et al., 1978) have been proposed on a front formed by a coupling effect of cooling of the sea surface and inflow of the fresh water in a vertical two-dimensional plane without the rotation of the earth. It is, however, not easy to interpret their numerical results. A simple interpretation will be proposed by an analytical study in this paper.It is found that local convection due to the density inversion, which is expressed by the convective adjustment of the vertical diffusion coefficient in the actual numerical calculations, plays an important role on the front formation.The characteristics of the front is also clarified in the case of steady state. Namely, simple functional dependences are obtained of the position and the width of the front, the horizontal and the vertical velocities and the distribution of the buoyancy and the salinity in the neighborhood of the front on the horizontal coordinate, the cooling rate, the eddy coefficients of diffusion and viscosity, the water depth and the vertically averaged horizontal fluxes of buoyancy and salinity. 相似文献
44.
REEdistributioninwater-sedimentinterfacesystematdeepoceanfloor¥ZhangLijie;LiuJihuaandYaoDe(ReceivedFebruary1,1994;acceptedMay... 相似文献
45.
东太平洋沉积物U的地球化学 总被引:4,自引:0,他引:4
本文对地矿部“海洋四号”科学考察船1987-1989年在东赤道太平洋CC区所取得的27个深海表层沉积样品进行U的地球化学分析,探讨了U在深海沉积中的地球化学行为,结果表明,不同类型沉积的U含量不同,平均值由大至小的次序的含沸石粘土(2.16×10^-6),硅质粘土(1.95×10^-6),硅质软泥(1.65×10^-6),钙质硅质粘土(1.59×10^-6),在同类型沉积中U的分散性较大;U在区域 相似文献
46.
南海西沙西南海域表层沉积物特征 总被引:3,自引:1,他引:3
西沙西南海域表层沉积物样品矿物成分,地球化学,微体古生物分析测试结果表明:沉积物可分为7种类型,沉积环境主要是陆坡,部分为深海平原,海洋生物,海洋化学以及火山物质的沉积起到了积极的作用,陆源物质的影响较小,它们主要来源于北部大陆和南部岛礁等物源区。 相似文献
47.
The behavior of isolated meso-scale eddies near the coastal boundary is studied by numerical experiments based on the quasi-geostrophic equation in a basin on an f-plane. First, Bachelor-modon type eddies are investigated as an idealized model of isolated eddies close to the wall. The first-mode Bachelor-modon type eddy is found to be robust enough to recover its original form even after it turns a corner of the basin. In contrast, the second mode is unstable; it tends to move away from the wall and finally splits into two eddies proceeding in opposite directions along the wall. An initially Gaussian eddy a little distant from the boundary interacts with a Bachelor-modon type eddy translating along the boundary, sometimes resulting in vortex merging and pairing just as in the head-on collision of two modons on a beta-plane. It is found that an initially Gaussian eddy located moderately close to the coast rapidly settles down to a steadily translating eddy, which can be approximated remarkably well by a first-mode Bachelor-modon type eddy not only in appearance but also in translation velocity within an error of about 20%. 相似文献
48.
Arata Kaneko Hiroyuki Honji Kazuo Kawatate Shinjiro Mizuno Akira Masuda Tsunehiro Miita 《Journal of Oceanography》1986,42(1):75-82
An internal wavetrain, generated by a tidal current in superposition with the Tsushima Warm Current, has been observed by use of an acoustic echo-sounder upstream of the Shichiri-Ga-Sone Seamounts in the East Tsushima Strait of the Japan Sea. The sea surface above the internal wavetrain was simultaneously observed and was found to be undulated at the wavelength of the internal wave. 相似文献
49.
Kohtaro Hosoda Hiroshi Murakami Akira Shibata Futoki Sakaida Hiroshi Kawamura 《Journal of Oceanography》2006,62(3):339-350
This study compares infrared and microwave measurements of sea surface temperature (SST) obtained by a single satellite. The
simultaneous observation from the Global Imager (GLI: infrared) and the Advanced Microwave Scanning Radiometer (AMSR: microwave)
aboard the Advanced Earth Observing Satellite-II (ADEOS-II) provided an opportunity for the intercomparison. The GLI-and AMSR-derived
SSTs from April to October 2003 are analyzed with other ancillary data including surface wind speed and water vapor retrieved
by AMSR and SeaWinds on ADEOS-II. We found no measurable bias (defined as GLI minus AMSR), while the standard deviation of
difference is less than 1°C. In low water vapor conditions, the GLI SST has a positive bias less than 0.2°C, and in high water
vapor conditions, it has a negative (positive) bias during the daytime (nighttime). The low spatial resolution of AMSR is
another factor underlying the geographical distribution of the differences. The cloud detection problem in the GLI algorithm
also affects the difference. The large differences in high-latitude region during the nighttime might be due to the GLI cloud-detection
algorithm. AMSR SST has a negative bias during the daytime with low wind speed (less than 7 ms−1), which might be related to the correction for surface wind effects in the AMSR SST algorithm. 相似文献
50.
We present H monochromatic and spectroscopic observations of the sudden disappearance of a dark filament located near the center of the solar disk on October 26, 1989. The event was not associated with the flare activity. The dark filament first disintegrated into two loop-like components, and then each component successively showed ascending motion with a velocity greater than 30 km s–1. Comparison of the H pictures taken before and after the start of this event suggests that the dark filament was originally composed of two magnetic flux loops. 相似文献