全文获取类型
收费全文 | 81671篇 |
免费 | 1149篇 |
国内免费 | 703篇 |
专业分类
测绘学 | 2233篇 |
大气科学 | 5760篇 |
地球物理 | 15495篇 |
地质学 | 31106篇 |
海洋学 | 6899篇 |
天文学 | 18065篇 |
综合类 | 299篇 |
自然地理 | 3666篇 |
出版年
2022年 | 416篇 |
2021年 | 685篇 |
2020年 | 788篇 |
2019年 | 886篇 |
2018年 | 4109篇 |
2017年 | 3732篇 |
2016年 | 3269篇 |
2015年 | 1203篇 |
2014年 | 1959篇 |
2013年 | 3388篇 |
2012年 | 2917篇 |
2011年 | 4783篇 |
2010年 | 4255篇 |
2009年 | 5109篇 |
2008年 | 4305篇 |
2007年 | 4798篇 |
2006年 | 2715篇 |
2005年 | 2237篇 |
2004年 | 2116篇 |
2003年 | 2062篇 |
2002年 | 1965篇 |
2001年 | 1590篇 |
2000年 | 1486篇 |
1999年 | 1256篇 |
1998年 | 1267篇 |
1997年 | 1236篇 |
1996年 | 1038篇 |
1995年 | 967篇 |
1994年 | 928篇 |
1993年 | 783篇 |
1992年 | 715篇 |
1991年 | 710篇 |
1990年 | 741篇 |
1989年 | 668篇 |
1988年 | 619篇 |
1987年 | 726篇 |
1986年 | 631篇 |
1985年 | 798篇 |
1984年 | 886篇 |
1983年 | 777篇 |
1982年 | 776篇 |
1981年 | 684篇 |
1980年 | 662篇 |
1979年 | 599篇 |
1978年 | 612篇 |
1977年 | 524篇 |
1976年 | 490篇 |
1975年 | 493篇 |
1974年 | 472篇 |
1973年 | 505篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
821.
This paper deals with the solution of the problem of the dynamic response of the leg of a tension leg platform subjected to an axial, suddenly applied load at one end, considering a highly simplified model but taking into account several complicating factors. The problem is solved by means of a non-harmonic Fourier expansion in terms of eigenfunctions obtained from a non-regular Sturm-Liouville system. 相似文献
822.
823.
Donald J. Walter Douglas N. Lambert David C. Young Kevin P. Stephens 《Geo-Marine Letters》1997,17(4):260-267
Real-time trackline plots of surficial sediment acoustic impedance delineate several sedimentary facies off Garden Key in
the Dry Tortugas. The sea floor within a 6×6 km surveyed area consists of carbonate muds (silts), sands and shell, rock, and
live corals. The 4-kHz acoustic data supports this finding by providing a pictographic representation of the distribution
and structure of several sediment facies types. Plotting the gridded acoustic data with commercial mapping software (Surfer)
provides a three-dimensional (3D) perspective of the bottom topography with a color contour map of surficial sediment impedance
(upper 0.4 m) draped over the 3D surface. 相似文献
824.
The expansion of the temperature anomaly field in the North Atlantic is considered using natural orthogonal functions of depth. It is shown that the first few components of this expansion describe the field both at the surface and in the upper 1000 m layer accurately enough. The relation between the water temperature anomaly at some levels and the above components is estimated for various regions of the ocean.Translated by Mikhail M. Trufanov. 相似文献
825.
P. Ziveri R.C. Thunell D. Rio 《Deep Sea Research Part I: Oceanographic Research Papers》1995,42(11-12)
Seasonal changes in coccolithophore cell densities in the San Pedro Basin, Southern California Bight, were investigated for the period October 1991 to September 1992. Coccolitho phore cell densities ranged from 6.3 × 104 coccospheres per liter in March 1992 to 0 cells per liter in November 1991. High coccolithophore concentrations occurred in late winter and spring, and low densities occurred in the summer and fall. The high coccolithophore densities during spring 1992 were associated with unusually low surface nutrient concentrations and a lack of upwelling, suggesting that the high densities were not part of a typical spring phytoplankton bloom in this region. We propose that the suppression of upwelling during spring 1992 may have been related to the prevailing ENSO conditions. Emiliania huxleyi type A dominated the total coccolithophore population throughout the year, Umbilicosphaera sibogae var. sibogae being the second most important contributor to the coccolithophore assemblages. 相似文献
826.
827.
828.
829.
We perform the analysis of the time spectra of four tsunamis generated in the Black Sea by the earthquakes of 26.07.1927,
11.09.1927, 26.12.1939, and 12.07.1966. For the analysis of the spectra, we used digitized marigrams obtained for 12 points
of the Black-Sea coast. The obtained spectra are, as a rule, multimode and have 1–4 spectral maxima. One maximum corresponds
to the periods typical of tsunami waves and the other maxima correspond to the oscillations of the sea level with lower frequencies.
It seems likely that the events of tsunami are accompanied by low-frequency oscillations of the level caused by the atmospheric
forcing, seiches, or other factors. In numerous cases, the oscillations from the predominant energy range lie outside the
characteristic range of periods of the tsunami waves.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 21–30, September–October, 2007. 相似文献
830.
Maps of the boundary topography for anaerobic waters in the Black Sea are plotted for the summers of the 1920s and 1980s. The mean depths of the H2S boundary for this period are determined. It is shown that the variation in the distribution and average location of the hydrogen sulphide zone has remained constant for the last 60 years.Translated by Mikhail M. Trufanov. 相似文献