全文获取类型
收费全文 | 86237篇 |
免费 | 980篇 |
国内免费 | 550篇 |
专业分类
测绘学 | 2144篇 |
大气科学 | 5431篇 |
地球物理 | 16170篇 |
地质学 | 33311篇 |
海洋学 | 7406篇 |
天文学 | 19067篇 |
综合类 | 290篇 |
自然地理 | 3948篇 |
出版年
2022年 | 573篇 |
2021年 | 928篇 |
2020年 | 978篇 |
2019年 | 1112篇 |
2018年 | 4258篇 |
2017年 | 3813篇 |
2016年 | 3461篇 |
2015年 | 1225篇 |
2014年 | 2167篇 |
2013年 | 3756篇 |
2012年 | 3105篇 |
2011年 | 4931篇 |
2010年 | 4419篇 |
2009年 | 5198篇 |
2008年 | 4375篇 |
2007年 | 4980篇 |
2006年 | 3059篇 |
2005年 | 2276篇 |
2004年 | 2166篇 |
2003年 | 2176篇 |
2002年 | 2007篇 |
2001年 | 1715篇 |
2000年 | 1548篇 |
1999年 | 1150篇 |
1998年 | 1179篇 |
1997年 | 1220篇 |
1996年 | 954篇 |
1995年 | 959篇 |
1994年 | 905篇 |
1993年 | 808篇 |
1992年 | 775篇 |
1991年 | 760篇 |
1990年 | 798篇 |
1989年 | 740篇 |
1988年 | 704篇 |
1987年 | 780篇 |
1986年 | 657篇 |
1985年 | 871篇 |
1984年 | 926篇 |
1983年 | 848篇 |
1982年 | 768篇 |
1981年 | 803篇 |
1980年 | 718篇 |
1979年 | 624篇 |
1978年 | 656篇 |
1977年 | 619篇 |
1976年 | 554篇 |
1975年 | 542篇 |
1974年 | 535篇 |
1973年 | 571篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
891.
We describe the methodology and software developed for the numerical analysis of the characteristics of the horizontal and vertical structure of geostrophic currents. We present the results of computation of these characteristics according to the data of the summer survey of the Black Sea carried out as a part of the ComSBlack-92 program. The distinctive features of the space structure of geostrophic currents discovered as a result and the established parameters of their variability may supplement the existing data on the current field in the Black Sea. 相似文献
892.
LI Hongwei TAN Jiahua Ph. D. Candidate School of Naval Architecture Ocean Engineering Shanghai Jiaotong University 《中国海洋工程》1998,(4)
This paper analyzes the pipe network system of oil-gas collection and transportation foroffshore oilfield development.A"0-1"integer linear programming model is constructed to optimize theinvestment of seabed pipe network.The mathematical model is solved by the spanning tree method ofgraph theory and network analysis.All spanning trees of a network graph compose all the feasible solu-tions of the mathematical model.The optimal solution of the model is the spanning tree with the minimumcost among all spanning trees.This method can be used to optimize the seabed pipe network system andgive a minimum cost plan for the development of offshore marginal oilfield groups. 相似文献
893.
The high diversity of grain-size parameters of marine and oceanic sediments is determined by hydrodynamical and gravitational processes. Grain-size spectra of the sediments in the World Ocean are represented by two main types. Filtering organisms that passively inherit the proportions of clayey fractions in suspended matter only accelerate the deposition of fine particles, not influencing their distribution at the bottom. 相似文献
894.
Ya. A. Virolainen Yu. M. Timofeev A. V. Polyakov H. Steele M. Newchurch 《Izvestiya Atmospheric and Oceanic Physics》2006,42(6):752-764
A statistical ensemble of microphysical parameters of the background stratospheric aerosol at altitudes of 15 to 30 km is modeled on the basis of experimental data. The aerosol attenuation coefficients (AACs) in the wavelength range 0.38–16.3 μm are calculated for all realizations of the ensemble by algorithms of the Mie theory. Analysis of correlations between the AACs and the microphysical parameters indicate that the AAC correlates most strongly with the total volume V and area S of all particles. The errors of determining the microphysical parameters from AAC measurements are analyzed via the method of linear regression. It is shown that, if the AAC is measured with an error of 5%, the errors of determining both the particle size distribution (PSD) for particles with sizes of 0.4 to 4 μm and the parameter S are an order of magnitude smaller than the prior uncertainty, whereas the error of determining V is two orders of magnitude smaller than the prior uncertainty. Schemes of AAC measurements with the SAGE III, ISAMS, CLAES, HALOE instruments and an IR interferometer in the visible and IR regions are discussed. It is shown that combining the schemes makes it possible to extend the range of particle sizes for which the PSD is retrieved with a satisfactory accuracy and to increase the accuracy of determining S and V substantially and the accuracy of determining the total number of particles N opt to a lesser extent. Examples of interpreting AAC measurements carried out simultaneously with the SAGE III and HALOE instruments within the same spatial region are presented. A systematic discrepancy between vertical profiles of S and V obtained from SAGE III and HALOE measurements is revealed. 相似文献
895.
896.
897.
The results of theoretical studies of fracture lines in the ice floes of the Gulf of Ob as a function of the coefficient of internal sliding are presented in this paper. An estimate of the fractal dimensions of the emerging topological structures and the results of the calculation of stresses in the ice cover of the Gulf of Ob are presented as functions of different directions of external forcing caused by the joint action of winds and currents on the ice. The geographical locations of the zones of possible loads are shown, together with the estimates of the hummock sizes in the zones of the maximal compression of the ice floes in the Gulf of Ob. 相似文献
898.
899.
Within the framework of the linear theory taking into account the action of the Coriolis force, we study waves induced in a continuously stratified fluid with one thermocline by periodic variations of pressure on the free surface. The fluid fills a bounded basin of constant depth. We establish the dependences of the wave amplitudes and wave velocities on the period of disturbing pressure. The sequence of transformations of generated waves from the barotropic character of motion to baroclinic depending on changes in the period of disturbing pressure is studied in detail. 相似文献
900.
In application to the Crimean regional centre for satellite data reception, treatment, and dissemination, we have identified
the earth’s satellite-surveyed areas, with orbital heights (H) ranging from 650 to 750 km. This paper shows that for the Ukrainian territory and the Sea of Azov-Black Sea environment
to be monitored, the regional centre’s receiving station must be capable of receiving radar signals from a range of about
1500 km. For typical high-speed radio lines, this may be achieved through the use of a satellite data-receiving station, with
the antenna’s diameter being about 3 m.
Translated by Vladimir A. Puchkin. 相似文献