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91.
The longitudinal fast solitary waves induced by weakly relativistic positron showers of astrophysical origin are studied in a plasma system contaminated with some massive impurities in presence of superthermal effects. The superthermal effects are due to the high energy electrons. The impurities are dust corpuscles with positive and negative charges. It is noticed that increase in the kappa parameter of electrons and relativistic streaming factor of weakly relativistic positron shower, negative dust concentration invoke an enhancement in the strength of solitary wave. On the other hand increase in the shower’s temperature as well as positive dust concentration diminish the solitary hump strength. It is worth to mention that only hump type compressive fast solitary waves are predicted by our model, for the given set of plasma parameters, because the convective coefficient of the nonlinear governing equation for solitary wave remains positive in considered regime of interaction for plasma and positron shower. Our calculations in linear regime predict both the fast and slow positron shower induced longitudinal, electrostatic perturbations. Our results may be of importance in understanding the nonlinear propagation of waves in doped astrophysical superthermal plasmas with relativistic positron showers. 相似文献
92.
M. Sohel Rana B.Sc. A. T. M. Rafiqul Hoque M. Sc. S. M. Asadul Hossain B.Sc. 《International Journal of Environmental Science and Technology》2007,4(3):395-400
In this paper, experimentally the pressure distribution over wedge and sphere surface in uniform flow has been investigated. Fluid flow over a smooth wedge surface was investigated experimentally to determine the pressure distribution at different values of Reynolds numbers and wedge angles as well as pressure distributions around the sphere of different size are reported for different Reynolds numbers. The variation of static pressures is larger near the wedge vertex and gradually decreases along the length of the wedge surface. At the forward stagnation point the pressure distribution depends on the size of spheres. Separation of flow takes place at an angle of 78° from forward stagnation point for all sizes of spheres. At the rear stagnation point of the sphere the pressure distribution predicts negative pressures. Experimental results provide useful information of interest to potential industrial application. It helps in determining the shape of various wedge and sphere surfaces used in industries for cooling or heating of different wedge surfaces. In the present experiment, it has been found that the pressure near vertex lower as the included angle of the wedge decreases and at lower values of Reynolds number. 相似文献
93.
Unsteady laminar free convection flow of a viscous incompressible and electrically conducting fluid past an accelerated vertical infinite porous plate subjected to a suction velocity proportional to (time)–1/2 is studied in presence of a uniform horizontal magnetic field. Results are discussed with the effects of the Grashof number Gr, and the magnetic field parameterM for Pr (the Prandtl number)=0.71 and 7.0 representing air and water respectively at 20 °C.Nomenclature
a
suction/injection parameter
-
C
p
specific heat at constant pressure
-
B
0
magnetic induction
-
g
acceleration due to gravity
- Gr
Grashof number (vg(T'w-T')/U
0
3
)
-
K
thermal conductivity
-
M
magnetic field parameter (B
0
2
e
2
/U
0
2
)
- Pr
Prandtl number (C
p/K)
-
T'
temperature of the fluid near the plate
-
T'
w
temperature of the plate
-
T'
temperature of the fluid at infinity
-
t'
time variable
-
t
dimensionless time (t' U
0
2
/v)
-
u
non-dimensional velocity (u'/U
0)
-
U'
velocity of the plate
-
U
dimensionless velocity of the plate (U'/U
o)
-
U
0
reference velocity
-
v'
0
suction velocity
-
v
0
nondimensional suction velocity (v'
0/U
0)=at–1/2
-
v'
normal velocity component
-
v
dimensionless normal velocity
- Ec
Eckert number ((vU
0)2/3/C
p(T'
w
-T'
))
-
T
dimensionless temperature of the fluid near the plate ((T'-T'
)/T'
w
–T'
))
-
x',y'
coordinates along and normal to the plate
-
y
dimensionless ordinate (=y' U
o/v)
-
v
kinematic viscosity
-
coefficient of volume expansion
-
electric conductivity of the fluid
-
similarity variable (y/2t)
- w
density of the fluid at the plate
-
density of the fluid at infinity
- '
skin-friction
-
dimensionless skin-friction
-
coefficient of viscosity
- e
magnetic permeability 相似文献
94.
Groundwater arsenic contamination in Manipur,one of the seven North-Eastern Hill states of India: a future danger 总被引:1,自引:0,他引:1
Dipankar Chakraborti E. Jayantakumar Singh Bhaskar Das Babar Ali Shah M. Amir Hossain Bishwajit Nayak Sad Ahamed N. Rajmuhon Singh 《Environmental Geology》2008,56(2):381-390
Manipur State, with a population of 2.29 million, is one of the seven North-Eastern Hill states in India, and is severely
affected by groundwater arsenic contamination. Manipur has nine districts out of which four are in Manipur Valley where 59%
of the people live on 10% of the land. These four districts are all arsenic contaminated. We analysed water samples from 628
tubewells for arsenic out of an expected total 2,014 tubewells in the Manipur Valley. Analyzed samples, 63.3%, contained >10 μg/l
of arsenic, 23.2% between 10 and 50 μg/l, and 40% >50 μg/l. The percentages of contaminated wells above 10 and 50 μg/l are
higher than in other arsenic affected states and countries of the Ganga–Meghna–Brahmaputra (GMB) Plain. Unlike on the GMB
plains, in Manipur there is no systematic relation between arsenic concentration and the depth of tubewells. The source of
arsenic in GMB Plain is sediments derived from the Himalaya and surrounding mountains. North-Eastern Hill states were formed
at late phase of Himalaya orogeny, and so it will be found in the future that groundwater arsenic contamination in the valleys
of other North-Eastern Hill states. Arsenic contaminated aquifers in Manipur Valley are mainly located within the Newer Alluvium.
In Manipur, the high rainfall and abundant surface water resources can be exploited to avoid repeating the mass arsenic poisoning
that has occurred on the GMB plains. 相似文献
95.
96.
97.
98.
Paleoproterozoic granitoids in the basement of Bangladesh: A piece of the Indian shield or an exotic fragment of the Gondwana jigsaw? 总被引:1,自引:0,他引:1
S.M. Mahbubul Ameen Simon A. Wilde Md. Zafrul Kabir Eunuse Akon Khalil R. Chowdhury Md. Sharif Hossain Khan 《Gondwana Research》2007,12(4):380-387
We present the first precise age for Precambrian basement rocks in Bangladesh. These lie within the Dinajpur block, located between the Indian Craton to the southwest and the Shillong Massif to the east. There are no surface outcrops and the rocks were intersected by drill holes. They consist of a suite of tonalitic and granodioritic rocks, variously deformed to granitic gneiss and intruded by younger monzogranite. A tonalite obtained at a depth of 227.48 m in drill hole BH-2 at Maddhapara, in northwestern Bangladesh, records a SHRIMP zircon 207Pb/206Pb magmatic age of 1722 ± 6 Ma. Paleoproterozoic rocks with similar magmatic ages are unknown in the adjacent Indian blocks of the Chotanagpur Plateau (Indian Craton) or Shillong Massif. This lack of comparable ages may be due to the paucity of precise radiometric ages from the Indian terrains or, more likely, because there are real age differences, with the buried rocks at Maddhapara representing a separate and discrete microcontinental fragment (the Dinajpur block) that was trapped by the northward migration of India during Gondwana dispersal. 相似文献
99.
100.