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991.
Monsoon rivers of Asia 总被引:2,自引:0,他引:2
992.
Tidal deformation of the Earth is normally calculated using the analytical solution with some simplified assumptions, such as the Earth is a perfect sphere of continuous media. This paper proposes an alternative way, in which the Earth crust is discontinuous along its boundaries, to calculate the tidal deformation using a finite element method. An in-house finite element code is firstly introduced in brief and then extended here to calculate the tidal deformation. The tidal deformation of the Earth due to the Moon was calculated for an geophysical earth model with the discontinuous outer layer and compared with the continuous case. The preliminary results indicate that the discontinuity could have different effects on the tidal deformation in the local zone around the fault, but almost no effects on both the locations far from the fault and the global deformation amplitude of the Earth. The localized deformation amplitude seems to depend much on the relative orientation between the fault strike direction and the loading direction (i.e. the location of the Moon) and the physical property of the fault. 相似文献
993.
基于多孔介质渗流力学和流固耦合理论,建立了应力作用下煤储层中煤层气流固耦合数学模型,并根据数学模型的非线性特性,采用多重物理量耦合软件COMSOL Multiphysic进行数值模拟分析,通过模拟结果研究了煤岩体中压力和浓度的分布特性,并且研究了耦合与非耦合情况下压力动态曲线,为模拟煤层气产量预测和预防矿井瓦斯突出提供了理论依据。 相似文献
994.
A comparative study of nutrient transfer via surface runoff from two small agricultural catchments in north China 总被引:1,自引:0,他引:1
A field study was conducted to determine the effect of landscape spatial pattern and micro-topography on nutrient transfer
via runoff from two catchments into Yuqiao Reservoir in north China. The surface runoff discharge was measured during rainfall
events and water samples were analyzed in 2004 and 2005. The mean annual total nitrogen (TN) and total phosphorus (TP) exports
per unit area from Caogezhuang catchment (C catchment) were 1.048 and 0.561 kg ha−1 year−1, respectively, while the TN and TP exports from Taohuasi catchment (T catchment) were 0.158 and 0.027 kg ha−1 year−1. In both catchments, village and vineyard shared the highest nutrient export ability due to the accumulated animal waste
and heavy application of fertilizer and manure. In T catchment, the distance of village and vineyard was about 1,500 m away
from the receiving water and in between were woodland and cropland. In the hydrological pathway, there were sink landscape
structures of small stone dams, roadside swale, vegetated filter strip and dry ponds, which could detain water and nutrients.
In C catchment, the distance between the village and the receiving water was about 200 m, and the hydrological pathway was
compacted roads and ditches with no sink structures. It is suggested that the distance between the pollution source area and
the receiving water and the micro-topographical features were the main factors to control the great difference in nutrient
export rates. 相似文献
995.
996.
Assessing pollutions of soil and plant by municipal waste dump 总被引:1,自引:0,他引:1
Changli Liu Yun Zhang Feng’e Zhang Sheng Zhang Miying Yin Hao Ye Hongbing Hou Hua Dong Ming Zhang Jianmei Jiang Lixin Pei 《Environmental Geology》2007,52(4):641-651
Research is few in the literature regarding the investigation and assessment of pollutions of soil and plant by municipal
waste dumps. Based upon previous work in seven waste dumping sites (nonsanitary landfills) in Beijing, Shanghai and Shijiazhuang,
this study expounds the investigation and assessment method and report major pollutants. Using relative background values,
this study assesses soil pollution degree in the seven dumping sites. Preliminary conclusions are: (1) pollution degrees are
moderate or heavy; (2) pollution distance by domestic waste that is dumped on a plane ground is 85 m; (3) the horizontal transport
distance of pollutants might be up to 120 m if waste leachates are directly connected with water in saturated soils; (4) vertical
transport depth is about 3 m in unsaturated silty clayey soils. Furthermore, using relative background values and hygiene
standards of food and vegetable this study assesses the pollutions of different parts of reed, sorghum, watermelon and sweet-melon.
It is found: (1) in comparison with the relative background values in a large distance to the waste dumping sites, domestic
wastes have polluted the roots and stems of reed and sorghum, whereas fine coal ash has polluted the leaves, rattans and fruits
of watermelon and sweet-melon; (2) domestic wastes and fine coal ash have heavily polluted the edible parts of sorghum, water
melon and sweet-melon. As, Hg, Pb and F have far exceeded standard values, e.g., Hg has exceeded the standard value by up
to 650–1,700 times and Cd by 120–275 times, and the comprehensive pollution index is up to 192.9–369.7; (3) the polluted sorghum,
watermelon and sweet-melon are inedible. 相似文献
997.
Pinnaduwa H. S. W. Kulatilake Jinyong Park Pirahas Balasingam Sean A. Mckenna 《Geotechnical and Geological Engineering》2007,25(1):79-102
A 1 km square regular grid system created on the Universal Transverse Mercator zone 54 projected coordinate system is used
to work with volcanism related data for Sengan region. The following geologic variables were determined as the most important
for identifying volcanism: geothermal gradient, groundwater temperature, heat discharge, groundwater pH value, presence of
volcanic rocks and presence of hydrothermal alteration. Data available for each of these important geologic variables were
used to perform directional variogram modeling and kriging to estimate geologic variable vectors at each of the 23949 centers
of the chosen 1 km cell grid system. Cluster analysis was performed on the 23949 complete variable vectors to classify each
center of 1 km cell into one of five different statistically homogeneous groups with respect to potential volcanism spanning
from lowest possible volcanism to highest possible volcanism with increasing group number. A discriminant analysis incorporating
Bayes’ theorem was performed to construct maps showing the probability of group membership for each of the volcanism groups.
The said maps showed good comparisons with the recorded locations of volcanism within the Sengan region. No volcanic data
were found to exist in the group 1 region. The high probability areas within group 1 have the chance of being the no volcanism
region. Entropy of classification is calculated to assess the uncertainty of the allocation process of each 1 km cell center
location based on the calculated probabilities. The recorded volcanism data are also plotted on the entropy map to examine
the uncertainty level of the estimations at the locations where volcanism exists. The volcanic data cell locations that are
in the high volcanism regions (groups 4 and 5) showed relatively low mapping estimation uncertainty. On the other hand, the
volcanic data cell locations that are in the low volcanism region (group 2) showed relatively high mapping estimation uncertainty.
The volcanic data cell locations that are in the medium volcanism region (group 3) showed relatively moderate mapping estimation
uncertainty. Areas of high uncertainty provide locations where additional site characterization resources can be spent most
effectively. The new data collected can be added to the existing database to perform future regionalized mapping and reduce
the uncertainty level of the existing estimations. 相似文献
998.
本文探讨了GPS RTK定位技术在大面积1:1000航测成图高程测量方案中的实施,对布网方案进行了研究与探讨,并对GPS RTK用于高程测量的精度进行了分析,对其应用前景作出评价。 相似文献
999.
Coseismic water level oscillation and correlated deep water temperature changes have been observed in a water well at Tangshan City by high sensitivity measurement. Amount of water temperature changes depend on ampli-tude of water level oscillation. Coseismic water temperatures always decrease as water level oscillates, drop of temperature ranges from 0.001 °C to 0.01 °C corresponding to amplitude of water level oscillation from several centimeters to about one meter. Temperatures usually recover one to several hours after the oscillation. We suggest that the temperature drop is produced by dispersive transfer of heat as the water oscillates, and follow-up thermal conduction makes temperature recovery. Our finite element calculations support quantitatively the idea. High ac-curacy measurements of water temperature at different depths in the future may test our interpretation. 相似文献
1000.
Optical dating of Holocene sand dune activities in the Horqin sand-fields in inner Mongolia, China, using the SAR protocol 总被引:4,自引:0,他引:4
The Horqin sand-field in northeastern Inner Mongolia, China, had been the fertile grassland in North China, but desertification and sand-dust storm have increasingly occurred in the past decades [Zhu and Wang, 1992. Theory and practice of sandy desertification in China (in Chinese with English abstract). Quaternary Sciences 2, 97]. To understand the Holocene sand dune activities in this region, five sand dune profiles were investigated, and 32 coarse grain quartz samples were dated by OSL using the single-aliquot regenerative-dose (SAR) protocol [Murray and Wintle, 2000. Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol. Radiation Measurements 32, 57–73]. For cross-checking, six organic-rich samples from the paleosols and sandy peat/mud were dated by both 14C and quartz OSL. With one exception, 14C and quartz OSL dating results show good agreements. Based on the consistent results of five sand dune profiles, a chronology of Holocene dune activity in Horqin sand-field is established as follows: (i) active sand dunes built up widely before 10 ka; (ii) dunes semi-stabilized between 10 and 7.5 ka ago; (iii) the dunes solidify and chernozem soils developed between 7.5 and 2.0 ka ago; and (iv) partially re-mobilization of dunes occurred since about 2.0 ka ago. 相似文献