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81.
An investigation of near surface wind speed trends in arid and semiarid regions of Iran 总被引:1,自引:0,他引:1
Mohammad Reza Kousari Hossein Ahani Hemila Hakimelahi 《Theoretical and Applied Climatology》2013,114(1-2):153-168
Wind plays an important role on the ecosystems and hydrological cycles besides other meteorological parameters such as temperature, precipitation, sunshine, and relative humidity. It strongly affects evapotranspiration, especially in arid and semiarid regions where there are serious problems in regard to water resource management. Evaluating the wind speed trend can provide good information for future agricultural planning. This study was conducted in order to investigate the wind speed trends over 24 synoptic meteorological stations located in arid and semiarid regions of Iran from 1975 to 2005. Near-surface wind speed was trended by nonparametric Mann–Kendall test spatially and temporally in three time scales (annual, seasonal, and monthly). Then, Sen’s slope estimator was used to determine the amount of the changes; furthermore, 10-year moving average low-pass filter was applied to show general trends. Finally, the smoothed time series derived from the mentioned filter were classified in three clusters for each time series and then mapped to show their spatial distribution pattern. Results showed insignificant and significant, increasing and decreasing trends during the surveyed time. Wind speeds in less than 50 % of stations changed statistically in all time scales, and in most cases, the frequency of the upward trends was more than that of downward ones. The spatial distribution of significant wind speed showed that the increase mostly occurred in eastern part. Clustering gave us the turning point around 1990. Clearly, when clusters were mapped, they indicated the same pattern as the Z value maps derived from Mann–Kendall test which meant that the outputs of the mentioned method confirmed the other one. As the wind speed trends in different stations likely to follow the previous evapotranspiration (ET0) trend results in Iran, it confirms that wind speed was an effective parameter on ET0, even though other parameters should be considered too. 相似文献
82.
Naseer Iqbal Tabasum Masood Mubashir Hamid Naveel Ahmad Bari Maqbool 《Astrophysics and Space Science》2014,353(2):621-624
The correlation function theory on the basis of prescribed boundary conditions provides a deeper understanding in studying the dynamical parameters of galaxy clusters. The approach approximates that the moderate dense systems discussed by a two point correlation function is helpful for describing the dynamical nature of galaxy clusters. The projected theory of two point correlation function for point mass and extended mass structures can be used an alternative tool in measuring the average peculiar motion and temperature profile of galaxy clusters. 相似文献
83.
84.
Hamid M. K. Al-Naimiy 《Astrophysics and Space Science》1978,53(1):3-11
The radiation of a charge rotating in a circle with the constant velocity (in the external magnetic field) in the isotropic plasma with random inhomogeneities of the electron density has been considered. A general expression is obtained for the radiation intensity at thenth harmonic, which is a generalization of the known Shott formula. In the ultra-relativistic case the conditions are clarified under which the inhomogeneity effect on the form of the spectrum of radiation from a particle is essential. An asymptotic formula is derived for the spectral intensity in the region of sufficiently low frequencies. The mechanism of transient radiation in this case is shown to prevail over the synchrotron one. 相似文献
85.
The distribution of fractures and its dependence on lithology and petrophysical properties of rock in the Asmari Formation were examined using three wells data of one of the largest oil fields of southwestern Iran. Fractures were measured on cut cores. Mineral content and petrophysical data were obtained through thin section study and core plug measurement respectively. Influence of mineral composition and petrophysical property of rocks on fracture density was explored statistically. Increasing quartz (sand) and anhydrite content of rocks decrease and dolomite increases the threshold of fracture densities, however no significant relation was observed between calcite content of rock and fracture density. Increasing porosity and permeability of rock decrease the threshold of fracture density in some of the defined lithology groups. There are significant differences between the lithology groups in terms of fracture density, although the results in the three wells are not the same. In whole data, the highest fracture density can be observed in dolostone. Limestone and impure carbonates hold broader spaced fractures and sandstones display the least fracture density. The average fracture densities in the wells are strictly different. These differences are the result of the structural position of the wells and also the trend of the well and fractures. The distribution of fractures in most lithology groups can be explained by the function: , where F is relative frequency, D is fracture density and a, b, and c are constants. 相似文献
86.
An investigation of trends in precipitation volume for the last three decades in different regions of Fars province, Iran 总被引:1,自引:1,他引:0
Hossein Ahani Mehrzad Kherad Mohammad Reza Kousari Mehdi Rezaeian-Zadeh Mohammad Amin Karampour Faezeh Ejraee Saeedeh Kamali 《Theoretical and Applied Climatology》2012,109(3-4):361-382
Under condition of climate changes as global warming, monitoring and detecting trend of precipitation volume is essential and will be useful for agricultural sections. Considering the fact that there were not enough research related to precipitation volume, this study aimed to determine trends in precipitation volume, monthly and annually in different regions of Fars province for the last three decades (33?years period; 1978–2010). Fars province is located in arid and semi-arid regions of Iran, and it plays an important role in agricultural production. Inverse distance weighting interpolation method was used to provide precipitation data for all regions. To analyze the trends of precipitation volume, Mann–Kendall test, Sen’s slope estimator, and 10-year moving average low-pass filter (within time series) were used. The negative trends were identified by the Sen’s slope estimator as well as Mann–Kendall test. However, all the trends were insignificant at the surveyed confidence level (95%). With regards to the application of 10-year moving average low-pass filter, a considerable decreasing trend was observed after around year 1994. Since one of the most important restrictions in agricultural development of the Fars province is lack of sufficient water resources, any changes onward to lack of sufficient precipitation impose impressive pressure and stress on valuable resources and subsequently agricultural production. 相似文献
87.
Hamid M. K. Al-Naimiy Ala A. J. Al-Douri Abdalla A. Alnajjar Umran Inan 《Earth, Moon, and Planets》2009,104(1-4):189-193
The proposed research project is aiming for providing basic data for quantitative comparison of lightning-induced disturbances of the ionosphere and the radiation belts in the American, European and Asia sectors. Most of the current data on such phenomena has so far been obtained in the western hemisphere, and the weight of scientific information indicates that lightning-induced effects at high altitudes and in the radiation belts may dominate other processes on a global scale. The proposed research project will facilitate the establishment and conduct of Very Low Frequency observations in the United Arab Emirates as a part of the Asia sector, thus providing a basis for comparison to facilitate global extrapolations and conclusions. Under the proposed project, Stanford University partners with Sharjah University, deploying one of their Very Low Frequency receivers at Sharjah University campus. Sharjah University provides the data digitization and recording equipment to facilitate continuous acquisition of the data. All data from the proposed project will be available for analysis over the Internet, and a series of annual visits are planned to maximize interactions and information exchange between the two universities. 相似文献
88.
Hamidreza Ramazi Mohammad Reza Hossein Nejad Aenollah Azizzadeh Firoozi 《Journal of the Geological Society of India》2009,74(2):260-266
This paper is devoted to application of SP, resistivity and mise-a-la-masse method in Khenadarreh (Arak, Iran) graphite deposit
exploration. Mise-a-la-masse method is one of the main geophysical exploration methods used to investigate conductive bodies
with outcrops on the surface or in exploratory pits. By integrating mise-a-la-masse results with other geoelectrical methods,
such as self-potential and resistivity surveys, useful results can be acquired. Powerful survey design, data processing and
interpretation methods can make geoelectrical surveying results more reliable. Here, we applied integrated geoelectrical methods
to explore the Khenadarreh-bala graphite deposit in the Sarband region of the Markazi province, Iran. We present a new and
simple method for processing and interpreting mise-a-la-masse data, which corrects for the effect of distance from the current
electrode in the conductive body. After correction, the residual potential values corresponded with the SP results and the
apparent resistivity pseudosections. The geophysical results were confirmed by drill holes in the study area. 相似文献
89.
Propagation of cylindrical and spherical electron-acoustic solitary waves in unmagnetized plasmas consisting of cold electron
fluid, hot electrons obeying a superthermal distribution and stationary ions are investigated. The standard reductive perturbation
method is employed to derive the cylindrical/spherical Korteweg-de-Vries equation which governs the dynamics of electron-acoustic
solitons. The effects of nonplanar geometry and superthermal hot electrons on the behavior of cylindrical and spherical electron
acoustic soliton and its structure are also studied using numerical simulations. 相似文献
90.
Kocatepe Ayberk Ulak Mehmet Baran Kakareko Grzegorz Ozguven Eren Erman Jung Sungmoon Arghandeh Reza 《Natural Hazards》2019,95(3):615-635
Natural Hazards - Roadway closures magnify the adverse effects of disasters on people since any type of such disruption increases the emergency response travel time (ERTT), which is of central... 相似文献