全文获取类型
收费全文 | 65673篇 |
免费 | 506篇 |
国内免费 | 371篇 |
专业分类
测绘学 | 1605篇 |
大气科学 | 3720篇 |
地球物理 | 11924篇 |
地质学 | 26897篇 |
海洋学 | 5487篇 |
天文学 | 14398篇 |
综合类 | 269篇 |
自然地理 | 2250篇 |
出版年
2022年 | 579篇 |
2021年 | 859篇 |
2020年 | 905篇 |
2019年 | 1010篇 |
2018年 | 4101篇 |
2017年 | 3648篇 |
2016年 | 3128篇 |
2015年 | 942篇 |
2014年 | 1865篇 |
2013年 | 2805篇 |
2012年 | 2745篇 |
2011年 | 4288篇 |
2010年 | 3796篇 |
2009年 | 4310篇 |
2008年 | 3626篇 |
2007年 | 4263篇 |
2006年 | 2352篇 |
2005年 | 1511篇 |
2004年 | 1450篇 |
2003年 | 1482篇 |
2002年 | 1376篇 |
2001年 | 1158篇 |
2000年 | 975篇 |
1999年 | 695篇 |
1998年 | 705篇 |
1997年 | 736篇 |
1996年 | 549篇 |
1995年 | 574篇 |
1994年 | 535篇 |
1993年 | 434篇 |
1992年 | 448篇 |
1991年 | 429篇 |
1990年 | 480篇 |
1989年 | 423篇 |
1988年 | 388篇 |
1987年 | 414篇 |
1986年 | 340篇 |
1985年 | 467篇 |
1984年 | 471篇 |
1983年 | 456篇 |
1982年 | 434篇 |
1981年 | 402篇 |
1980年 | 413篇 |
1979年 | 348篇 |
1978年 | 378篇 |
1977年 | 321篇 |
1976年 | 292篇 |
1975年 | 293篇 |
1974年 | 276篇 |
1973年 | 344篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
731.
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
732.
733.
Sublethal effects of cadmium on reproduction can have detrimental consequences for the long-term survival, even of species with high LC50 values. The sea mussel, Mytilus edulis, is well-known for its use in biomonitoring work due to its relatively low sensitivity towards many toxicants, including cadmium.1 Because little is known on sublethal effects of this metal in invertebrates,2–6 we have studied these effects, with emphasis on reproduction, by exposing mussels to 100 ppb cadmium in sea water. This concentration significantly inhibits follicle development in both male and female gonads, but has subsequently a stimulating effect on the spawning frequency. Due to these opposite effects the consequences of cadmium stress for gamete production are expected to be small, as the average number of gametes released by spawning animals was not significantly changed. 相似文献
734.
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
735.
Abstract. The marine plant communities of the littoral zone in different biotopes of the Greek coasts were investigated in 1980-81. Seasonal distribution and variation of marine plant biomass were assessed. The communities of Cystoseira crinita and C. compressa were outstanding with maximum biomass during the summer months. Corallina officinalis and Pterocladia capillacea + Viva rigida communities predominated with maximum biomass in autumn and exhibited a decrease in winter, except in stressed biotopes. The species diversity and productivity of seaweeds along the Greek coasts are interpreted in relation to a number of environmental parameters. 相似文献
736.
I. N. Ivanova O. N. Mel’nikova T. A. Nivina K. V. Pokazeev 《Izvestiya Atmospheric and Oceanic Physics》2006,42(5):646-652
The air-flow velocity field near the water surface is studied in the zone of wind-wave intensification. Caused by a periodic separation of eddies, a nonzero time-averaged value of the wind velocity in the near-water streamline is detected at the leading slope of the wave. The distribution of pressure along the wave with allowance for the vertical velocity shear and disturbances produced by eddies and a periodic deceleration of the viscous layer was calculated with the aid of the Cauchy-Lagrange integral. This procedure made it possible to calculate the growth rate of the wave amplitude, whose value was found to be close to its experimental value at the initial stage of acceleration. 相似文献
737.
A. E. Gledzer E. B. Gledzer F. V. Dolzhanskii V. M. Ponomarev 《Izvestiya Atmospheric and Oceanic Physics》2006,42(4):399-422
This paper analyzes the properties of solutions to the equations describing the motion of a stratified fluid in the class of velocity and temperature fields linear in coordinates. For an ideal fluid, these equations, on the one hand, are exact for the corresponding hydrodynamic problem and, on the other hand, are identical to the equations of motion for a heavy top. In a conservative case, the equations of motion of a top share common solutions with the equations of geophysical fluid dynamics and reproduce motions similar to those existing in the theory of the large-scale atmospheric circulation. This study considers the effects of viscosity and heat conduction in the fluid, which are, in a sense, similar to the effect of friction in the case of a top. The influence of deflections of the vectors of gravity and external rotation from their standard directions for a plane-parallel atmosphere is also considered. The regimes of motions that are described by the starting equations and approximations commonly used to model the atmospheric general circulation (the quasi-geostrophic approximation) are analyzed. It is shown that these equations correctly describe the Hadley and Rossby circulation regimes and transitions between them that are observed in numerical and laboratory experiments. Particular attention is given to the consistency between different regimes of the exact equations and their quasi-geostrophic approximations, which is manifested for small Rossby numbers and is generally absent for large Rossby numbers. The asymptotic behaviors of the curves of transition between the Hadley and Rossby regimes under the conditions of breaking the external symmetry of flows are obtained. These asymptotics explain the corresponding transition boundaries for the regimes observed in the known experiments in annuluses. 相似文献
738.
A method is proposed to study the transport of a passive additive in the atmospheric surface layer with the use of the atmospheric transfer function. This method makes it possible to estimate the spatial distribution of the concentration of a passive additive in the atmospheric surface layer from the additive’s surface source without experimentally determining the vertical profile of the transport coefficient or without resorting to various hypotheses for the character of its behavior. The transfer function, which contains the information on the wind-field structure, can be obtained from simple one-point measurements of surface-and air-temperature fluctuations and from subsequent spectral processing of the data. The effects of the wind-velocity profile and turbulence on the spatial distribution of additive concentration are assessed. This method allows one to simplify experiments during development and verification of the models of atmospheric diffusion. This method may also be useful in emergency situations to predict the propagation of hazardous additives. 相似文献
739.
The dependence of the variation in the depth of the upper mixed layer (MLD) on the governing parameters (the momentum flux, the buoyancy fluxes at the ocean surface, and the density gradient in the pycnocline) is considered. It is shown that, in the spring storm season, wind mixing dominates over convective mixing. In this case, the MLD is linearly correlated with the Ekman scale calculated from the friction velocity observed approximately 12 h before the measurement of the MLD. 相似文献
740.
I. Brandariz P. Castro M. Montes F. Penedo M.E. Sastre de Vicente 《Marine Chemistry》2006,102(3-4):291-299
Acid–base equilibrium constants of triethanolamine (TEA) have been determined by potentiometric titrations with a glass electrode, at 25 °C. Ionic strength was kept constant with only one electrolyte (using one of these salts: NaCl, KCl, MgCl2 or CaCl2), with binary mixtures of MgCl2 and CaCl2, and finally, in a solution with a composition approximately similar to that of natural seawater without sulfate. Equilibrium constants have been expressed in function of ionic strength by means of Pitzer equations and interaction parameters proposed in this theory have been obtained. It has been found that acid–base behaviour of TEA depends greatly on the salt used: basicity of TEA is decreased by CaCl2, while it is increased by the other electrolytes used in this work. 相似文献