全文获取类型
收费全文 | 419篇 |
免费 | 17篇 |
国内免费 | 28篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 49篇 |
地球物理 | 76篇 |
地质学 | 141篇 |
海洋学 | 22篇 |
天文学 | 142篇 |
综合类 | 10篇 |
自然地理 | 20篇 |
出版年
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 10篇 |
2020年 | 16篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 24篇 |
2016年 | 24篇 |
2015年 | 10篇 |
2014年 | 13篇 |
2013年 | 23篇 |
2012年 | 15篇 |
2011年 | 32篇 |
2010年 | 31篇 |
2009年 | 27篇 |
2008年 | 10篇 |
2007年 | 9篇 |
2006年 | 15篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2002年 | 6篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有464条查询结果,搜索用时 15 毫秒
1.
Translated fromAstrofizika, Vol. 37, No. 4, 1994. 相似文献
2.
In our preceding paper {see [L. Sh. Grigorian and S. Gottlöber, Astrofizika (in press)]} we investigated a self-gravitating system consisting of a scalar field and a linear tensor field ik= ki with minimal coupling and with allowance for the action of vacuum polarization effects. In the present paper we investigate the case of a nonlinear tensor field ik. The action S
()
of the field ik is determined by the difference Rik — ik, where Rik is the space-time Ricci tensor and Rik is the analogous quantity constructed using the metric ik=gik+ik induced by ik ( is a free parameter). Here
S
()
coincides with the previously known expression for the action of a linear field ik. Equations of motion are derived for ik in curved space-time. The energy-momentum metric tensor, determining the contribution of ik to the gravitational field equations, is calculated.Translated from Astrofizika, Vol. 39, No. 1, pp. 135–144, January-March, 1996. 相似文献
3.
The radius, mass, total number of baryons, and other parameters of static, spherically symmetric, superdense stars are calculated. A model with one Ricci-flat inner space of arbitrary dimensionality and the approximation p1=?0.5ε + ap for additional components of the energy — momentum tensor are used (ε and ρ are the total energy density and the pressure of the stellar matter and a is a fitting parameter). In the case of white dwarfs, the results of the multidimensional theory do not depend on the dimensionality D of space-time for ?10 ? a ? 10 and coincide with the analogous data of the general theory of relativity (GTR). For neutron stars there is a dependence on D and a. For D>4, in particular, the greatest mass Mmax of a neutron star as a function of a has a maximum at 3<a(D) ? 4, which exceeds the greatest mass M max 0 =2.14 M⊙ in the GTR. A comparison of theoretical results with observational data determines the allowable values of a. Data for PSR 1913 + 16 lead to 0.2 ≤ a ≤ 9.2 in the case of D=26, while the results of [P. C. Joss and S. A. Rappaport, Annu. Rev. Astron. Astrophys.,22, 537 (1984)] lead to the stricter limits 1 ≤ a ≤ 7.4. 相似文献
4.
Sh. T. Habibullin 《Earth, Moon, and Planets》1995,71(1-2):43-58
According to A.A. Khentov Venus' rotation is in the quasi-stationary state as a result of the balance interaction of the solar tidal torque with the aerodynamical torque of the rotating Venus' atmosphere. In case of the nonconservative forces are negligible and the solar attraction is the stabilizing factor, the rotation of the rigid Venus may be assumed as the first approximation. The theory of the rotation of the rigid Venus in the coordinates,, had been constructed. It have been found that Venus rotates almost uniformly and the libration harmonics are negligible. 相似文献
5.
An idea is developed that the vacuum in the gravitational field acquires properties of an elastic medium described by a definite tension
ik
. The vacuum is stated to also participate in the formation of the space-time metric, together with the usual matter. So, the matter, vacuum and metric form a complex unity determined by the solution of the field equations. The vacuum may prove to play an essential role in the extremely strong fields existing in superdense celestial bodies. The tensor
ik
is not to be identified with the pseudo-tensor of the energy-momentum of the gravitational field the idea of which is preserved.The problem of vacuum is investigated in the case of the central symmetry static field. A number of properties of the tensor
ik
is found using the symmetry of the field and comparison with the post-Newton limit. The external and internal problems, as well as the procedure of joining the solutions on the surface of a celestial body, have been formulated. The stellar surface is determined in the usual way:P(r) = 0 whereP is the matter pressure. The theory includes three dimensionless parametersa=p/,b=p
/ (,p, p
are the density of the vacuum energy and of its pressures in the radial and transverse directions) and determining the vacuum elastic properties. Generally speaking, they depend on the valueP/c2 in the stellar centre where is the mass density. From general physical considerations it is shown that 0 1 + lim
P (l/q). The field equations are solved for the simple version of the theoryb=–a. There are solutions corresponding to superdense celestial bodies with masses considerably exceeding that of the Sun. 相似文献
6.
H. Asilian M.Sc. Ph.D. Sh. Moradian fard M.Sc. A. Rezaei M.Sc. Ph.D. S. B. Mortazavi M.Sc. Ph.D. A. Khavanin M.Sc. Ph.D. 《International Journal of Environmental Science and Technology》2006,3(2):153-157
In this study acrylic water base color was removed from synthetic wastewater using coagulation process. Experiments were conducted on the sample containing 100 mg/L and 400 mg/L of acrylic water base color. Destruction of color by means of coagulation/flocculation techniques using ferrous sulfate, alum, lime and polyelectrolyte (cationic, anionic and non ionic). The study was performed in a systematic approach searching optimum values of alum and FeSO4 concentration, pH and temperature. All the experiments were run in a laboratory scale.The obtained results show that treatment with alum and ferrous sulfate alone proved to be very effective in removing the color (> 99 %) and part of COD (60–70 %) from aqueous solution. Lime alone did not significant change on COD and color removal. 相似文献
7.
8.
Sh. R. Yadav V. K. Murthy D. Mishra B. Baral 《International Journal of Environmental Science and Technology》2005,1(4):253-255
Kerosene is common adulterant utilized for mixing with diesel. Five fuel-adulterant mixtures in different proportions by volume were prepared and individually tested for density and kinematic viscosity. The mixtures were administered to six light cargo vehicles and the tail pipe exhaust emission was tested for opacity value. No appreciable density variation at different levels of adulteration was observed. Density was within the prescribed value even at higher adulteration. Considerable decrease in kinematic viscosity, a departure from prescribed viscosity, was noted at higher adulteration level. The percent opacity value decreased sharply even at small level of adulteration. The probable amount of kerosene present as an adulterant in diesel dispensed at filling stations in Kathmandu city ranged between 35% and 50%. The observations suggest density test is not a good indicator of diesel adulteration. Kinematic viscosity and opacity value are useful diesel adulteration test parameters. Existing diesel adulteration warrants initiation of strict compliance regulation. 相似文献
9.
E. Sh. Elizbarashvili M. E. Elizbarashvili N. B. Kutaladze I. Keggenhoff Sh. E. Elizbarashvili B. M. Kikvadze N. M. Gogia 《Russian Meteorology and Hydrology》2016,41(4):261-267
Using observational data from 50 weather stations in Georgia for the period of 1936-2013, the following climate indices of moisture regime are studied: maximum 1-day precipitation, maximum 5-day precipitation, the simple daily intensity index, the number of days with precipitation equal to not less than 10, 20, and 50 mm, number of consecutive wet and dry days. Geoinformation maps of the spatial structure are plotted, and the dynamics of these indices is studied for the period of global warming. Expected changes in the moisture regime in different physiographic regions in Georgia are assessed. 相似文献
10.
I. A. Bogush V. I. Cherkashin G. V. Ryabov M. Sh. Abdullayev 《Doklady Earth Sciences》2016,466(1):11-13
The weathering crust of the Beden ultrabasite massif (the basin of Big Laba River) is identified and studied. Anomalously high contents of noble metals (Au, Pt, Pd) are revealed in the basal horizon of the Jurassic part of the weathering crust. For this reason we suspect an existence of a belt of noble metal miner-alization in the Paleozoic ultrabasites in the Peredovoi Range of the Northern Caucasus. 相似文献