全文获取类型
收费全文 | 65462篇 |
免费 | 2205篇 |
国内免费 | 3339篇 |
专业分类
测绘学 | 2253篇 |
大气科学 | 5311篇 |
地球物理 | 12042篇 |
地质学 | 28718篇 |
海洋学 | 6162篇 |
天文学 | 12160篇 |
综合类 | 1239篇 |
自然地理 | 3121篇 |
出版年
2023年 | 366篇 |
2022年 | 1153篇 |
2021年 | 1527篇 |
2020年 | 1463篇 |
2019年 | 1566篇 |
2018年 | 4676篇 |
2017年 | 4180篇 |
2016年 | 3562篇 |
2015年 | 1422篇 |
2014年 | 2235篇 |
2013年 | 2802篇 |
2012年 | 3086篇 |
2011年 | 4695篇 |
2010年 | 4114篇 |
2009年 | 4435篇 |
2008年 | 3780篇 |
2007年 | 4380篇 |
2006年 | 2358篇 |
2005年 | 1499篇 |
2004年 | 1407篇 |
2003年 | 1501篇 |
2002年 | 1406篇 |
2001年 | 1199篇 |
2000年 | 977篇 |
1999年 | 777篇 |
1998年 | 708篇 |
1997年 | 758篇 |
1996年 | 587篇 |
1995年 | 601篇 |
1994年 | 550篇 |
1993年 | 450篇 |
1992年 | 428篇 |
1991年 | 385篇 |
1990年 | 410篇 |
1989年 | 372篇 |
1988年 | 325篇 |
1987年 | 314篇 |
1986年 | 237篇 |
1985年 | 338篇 |
1984年 | 334篇 |
1983年 | 323篇 |
1982年 | 303篇 |
1981年 | 282篇 |
1980年 | 296篇 |
1979年 | 221篇 |
1978年 | 250篇 |
1977年 | 213篇 |
1976年 | 187篇 |
1975年 | 195篇 |
1973年 | 213篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Wave records at seven different locations within a groin field have been analysed by both statistical and spectral approaches to study the general wave climate. The wave heights and periods from the wave records were obtained by both upcross and downcross methods for the statistical approach. The variation of different wave height and wave period parameters with respect to the time of measurement at a particular location and its variation at different locations within the groin field at a particular instant of time are presented and discussed in detail in this paper. It is generally found that the wave heights follow the Weibull distribution. 相似文献
82.
83.
From July, 1975 to November, 1976 mussels from the Laguna Veneta, north-east Italy, and the adjacent Adriatic Sea were collected bimonthly at ten stations and analysed for 3,4-benzopyrene (BaP) and perylene (Pe) content. Mean concentrations were in the range 12·0–135·1 μg/kg dry weight for BaP and 1·5–16·9 μg/kg for Pe, but values as high as 327 μg/kg for BaP and 71 μg/kg for Pe have been measured. The distribution of BaP and Pe closely matches previous results on petroleum hydrocarbon contamination in mussels from this area and indicates that the major portion of BaP and Pe in these bivalves is due principally to human activities. 相似文献
84.
Based on the MEGAPOLYGON data, it is shown that the large-scale elements of the thermohaline structure and the fields of currents in the baroclinic layer (down to 1200 m) are well coordinated. The circulation has a two-layer structure with a transitory layer at a depth of 1200 m. The topography of the isopycnic surface of the layer's core is formed under the influence of small-scale and mesoscale processes which realize the trans-frontal exchange.Translated by Mikhail M. Trufanov. 相似文献
85.
V. M. Kushnir 《Physical Oceanography》1995,6(3):229-236
Data on the fine vertical structure of currents and hydrological elements in the Black Sea, obtained through the use of a hydrophysical OLT profiler, are examined. Vertical exchange coefficients are evaluated, whose distribution is characterized by the occurrence of minima in the seasonal pycnocline and main halocline, a maximum in the core of the cold intermediate layer (CIL), and relatively steady values within the 300–500 m layer. The vertical exchange coefficient values, are consistent with the data acquired through other techniques, and the profiles of this parameter vertically are more detailed.Translated by Vladimir A. Puchkin. 相似文献
86.
The near wave field generated by the travelling atmospheric pressure zone over a stratified fluid is studied within the framework of the linear theory of long waves allowing for the Coriolis force. The exact solution of the problem as a set of single integrals is deduced for the model distribution of pressures. The characteristics of the near wave field have been computed for the Väisälä-Brunt frequency profile takeu from observations. Their dependences on the geographical latitude and the wave generator travelling rate are analysed.Translated by Mikhail M. Trufanov. 相似文献
87.
A. A. Bezborodov S. L. Gokchen V. N. Eremeev I. T. Konuk A. K. Saidam E. M. Tirasin 《Physical Oceanography》1991,2(3):227-231
The hydrological and hydrochemical structures of the upper 300 m water column of the Black Sea in autumn 1988 have been studied. Regularities in the distribution of the physico-chemical characteristics in the zone of interaction between aerobic and anaerobic waters as well as the topography of the H2S zone boundary and its connection with a certain density gradient have been found.Translated by Mikhail M. Trufanov. 相似文献
88.
89.
M. V. Ramana 《Geo-Marine Letters》1986,6(1):1-5
Satellite imagery and offshore magnetic data were analysed to correlate regional tectonic elements on the inner continental
shelf off Konkan and the adjacent Deccan plateau. Three statistically important lineament trends—N-S, WNW-ESE and ENE-WSW—that
prevail on land are correlatable well with the offshore trends. This positive correlation suggests simultaneous deformation.
The major magnetic lineament observed off Jaigad Bay, west coast of India, may be the extension of onshore lineaments. The
correlation of both the offshore and onshore trends indicates that the fracture pattern of the crystalline basement has also
controlled the offshore structural pattern. 相似文献
90.
Ivanov V. A. Kubryakov A. I. Lyubartseva S. P. Mikhailova É. N. Shapiro N. B. 《Physical Oceanography》2004,14(2):67-83
In the present work, we generalize the results of our investigations in the field of simulation of hydrophysical and ecological processes in coastal regions of various seas and some closed basins. The developed and applied mathematical models and the results of numerical experiments are briefly analyzed. 相似文献