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131.
Shafiee Ali Kamalian Mohsen Jafari Mohammad Kazem Hamzehloo Hossein 《Natural Hazards》2011,59(1):481-505
An important step in effectively reducing seismic risk and the vulnerability of a city located in an earthquake prone area
is to conduct a ground motion microzonation study for the desired return period. The International Institute of Earthquake
Engineering and Seismology (IIEES) initiated a number of seismic microzonation projects for Iran. This paper presents the
steps followed by IIEES in ground motion microzonation. IIEES performs both probabilistic and deterministic seismic hazard
analysis. IIEES uses his own fault map for seismotectonic studies and develops modulus and damping curves for the soils in
the study area. The experience of ground motion microzonation shows that in almost all cases, the estimated 475-year peak
ground acceleration (PGA) values are higher than the PGA proposed by the Iranian seismic code. Although ground motion microzonation
in Iran has some shortcomings, IIEES is making new improvement. This includes development in deterministic seismic hazard
analysis, two-dimensional and three-dimensional modelling of basin and topographical effects, using microtremor measurements
to find shear-wave velocity profiles in high-density urban areas and providing maps for spectral acceleration in the study
area. 相似文献
132.
The presence of heavy metal concentrations was examined in natural sediments from four sites along the Jajrood river in northeast
of Tehran, the capital of Iran. Besides determination of elemental concentrations (Pb, Cu, Zn, Cd, Ni and Cr), X-ray fluorescence
and X-ray diffraction tests were carried out to determine other chemical components in these adsorbents. Also the ability
of sediments to adsorb these heavy metal ions from aqueous solutions was investigated. Results show that the extent of adsorption
increases with increase in adsorbent concentration. The amount of adsorbed Pb, Cu and Zn in sediments was much greater than
that of the other metals, and Cr was adsorbed much less than others. The adsorbabilities of sediments to heavy metals increased
in the order of Pb > Cu > Zn > Cd > Ni > Cr. Based on the adsorption data, equilibrium isotherms were determined at selected
areas to characterize the adsorption process. The adsorption data followed Freundlich and Langmuir isotherms in most cases.
Correlation and cluster analysis was performed on heavy metals adsorption and sediment components at each site to evaluate
main adsorbing compounds in sediments for each metal. Results demonstrated that heavy metals sorption is mostly related to
load of organic matter in the Jajrood river sediments. 相似文献
133.
Mohsen Hamidpour Mahmoud Kalbasi Majid Afyuni Hossein Shariatmadari Gerhard Furrer 《Environmental Earth Sciences》2011,62(3):559-568
This study deals with the use of the natural, low-cost sorbents bentonite and zeolite for the removal of lead from aqueous
solutions. The mineral material is from large deposits of bentonite and zeolite that have been discovered recently in Iran.
Experimental and modeling data from our kinetic and equilibrium investigations reveal that (1) the pseudo-second-order kinetic
model gave the best fit, and (2) the Koble–Corrigan sorption model describes the interaction between Pb(II) and the two mineral
materials better than the Freundlich and Langmuir models. However, the sorption of Pb(II) ions by zeolite and bentonite is
complex and probably involves several mechanisms. The experimental data show that natural zeolite and bentonite used in this
study exhibited a reasonable sorption capacity for Pb(II), and thus may be useful for the immobilization of Pb(II) from polluted
sites. 相似文献
134.
Davoud Agha‐Aligol Mohammad Lamehi‐Rachti Parvin Oliaiy Farah Shokouhi Mohammad Farmahini Farahani Mahmoud Moradi Fatemeh Farshi Jalali 《Geoarchaeology》2015,30(3):261-270
It had long been thought that obsidian found in Iranian sites originated from Anatolia and Armenia, but new research has challenged this assumption. In this study, 68 samples of obsidian obtained from an archaeological survey of Nader‐Tepe Aslanduz were analyzed by Proton Induced X‐ray Emission (PIXE). Nader‐Tepe Aslanduz is a tell site west of the city of Aslanduz in the Parsabad county of the Ardebil province in northern Iran. The site was inhabited from the first millennium B.C. to A.D. 17, and its history may extend back to the third or fourth millennium B.C. Our chemical composition results have been combined with obsidian composition data from Turkey and Armenia and subjected to Principal Component Analysis (PCA). This analysis shows that obsidian from each location can be grouped into distinctive classes—the obsidian from Nader‐Tepe Aslanduz is therefore probably derived from volcanic outcrops of the Sahand and Sabalan region. This study has been unable to assign a known source from Anatolia and Armenia for the obsidian of Nader‐Tepe Aslanduz. 相似文献
135.
Fazeleh Khajenabi Mohsen Shadmehri 《Monthly notices of the Royal Astronomical Society》2007,377(4):1689-1695
We study the dynamical structure of a self-gravitating disc with coronae around a supermassive black hole. Assuming that the magnetorotational instability responsible for generating the turbulent stresses inside the disc is also the source for a magnetically dominated corona, a fraction of the power released when the disc matter accretes is transported to and dissipated in the corona. This has a major effect on the structure of the disc and its gravitational (in)stability according to our analytical and self-consistent solutions. We determine the radius where the disc crosses the inner radius of gravitational instability and forms the first stars. Not only the location of this radius which may extend to very large distances from the central black hole, but also the mass of the first stars highly depends on the input parameters, notably the viscosity coefficient, the mass of the central object and the accretion rate. For accretion discs around quasi-stellar objects (QSOs) and the Galactic Centre, we determine the self-gravitating radius and the mass of the first clumps. Comparing the cases with a corona and without a corona for typical discs around QSOs or the Galactic Centre, when the viscosity coefficient is around 0.3, we show that the self-gravitating radius decreases by a factor of approximately 2, but the mass of the fragments increases with more or less the same factor. The existence of a corona implies a more gravitationally unstable disc according to our results. The effect of a corona on the instability of the disc is more effective when the viscosity coefficient increases. 相似文献
136.
A systematic study of the linear thermal instability of a self-gravitating magnetic molecular cloud is carried out for the
case when the unperturbed background is subject to local expansion or contraction. We consider the ambipolar diffusion, or
ion-neutral friction on the perturbed states. In this way, we obtain a non-dimensional characteristic equation that reduces
to the prior characteristic equation in the non-gravitating stationary background. By parametric manipulation of this characteristic
equation, we conclude that there are, not only oblate condensation forming solutions, but also prolate solutions according
to local expansion or contraction of the background. We obtain the conditions for existence of the Field lengths that thermal
instability in the molecular clouds can occur. If these conditions establish, small-scale condensations in the form of spherical,
oblate, or prolate shape may be produced via thermal instability. 相似文献
137.
138.
Monjezi Sara Najarchi Mohsen Mo’meni Mansour Monjezi Narges Hassuninezade Houshang 《Water Resources》2021,48(6):1013-1022
Water Resources - To water quality management of the Gotvand Reservoir, this paper attempts to determine to what extent the negative impacts of Anbar salt domes dissolution can be reduced... 相似文献
139.
The objective of this paper is to test the ability of a spatially distributed hydrologic model (WetSpa) to simulate soil moisture. The test is conducted in the Baron Fork river basin (Oklahoma, USA), where soil moisture has been recorded on a daily basis at the WEST site soil moisture monitoring station of the Oklahoma Mesonet. The model is calibrated by comparing hourly simulated and observed river flows at Eldon gaging station from October 1, 1995 to December 31, 1996. The model performance to predict hourly river flows is verified by comparing model estimates and observations from January 1, 1997 to December 31, 2000. Next, the model predictions of soil moisture are compared with observations of WEST site soil moisture monitoring station for the same validation period. The observations are well reproduced by the model with errors that are within range of the observation accuracy, although the predictions show somewhat more abrupt temporal fluctuations as the whole root zone is considered to react instantaneously to precipitation events. The good performance compared to other studies is especially attributed to the quality of the rainfall data provided by weather radars. It is concluded that the performance of the model to predict soils moisture is promising, although spatial patterns still have to be verified. 相似文献
140.
This study investigated the effect of cations and anions on the sorption and desorption of iron (Fe) and manganese (Mn) in six surface calcareous soil samples from Western Iran. Six 10 mM electrolyte background solutions were used in the study, i.e., KCl, KNO3, KH2PO4, Ca(NO3)2, NaNO3, and NH4NO3. NH4NO3 and NaNO3 increased the soil retention of Fe and Mn, whereas Ca(NO3)2 decreased the soil retention of Fe and Mn. Iron and Mn sorption was decreased by NO3 ? compared with H2PO4 ? or Cl?. The Freundlich equation adequately described Fe and Mn adsorption, with all background electrolytes. The Freundlich distribution coefficient (K F) decreased in the order H2PO4 ? > Cl? > NO3 ? for Mn and H2PO4 ? > NO3 ? > Cl? for Fe. The highest sorption reversibility was for Fe and Mn in competition with a Ca2+ background, indicating the high mobility of these two cations. A MINTEQ speciation solubility model showed that Fe and Mn speciation was considerably affected by the electrolyte background used. Saturation indices indicated that all ion background solutions were saturated with respect to siderite and vivianite at low and high Fe concentrations. All ion background solutions were saturated with respect to MnCO3(am), MnHPO4, and rhodochrosite at low and high Mn concentrations. The hysteresis indices (HI) obtained for the different ion backgrounds were regressed on soil properties indicating that silt, clay, sand, and electrical conductivity (EC) were the most important soil properties influencing Fe adsorption, while cation exchange capacity (CEC), organic matter (OM), and Mn-DTPA affected Mn adsorption in these soils. 相似文献