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991.
The main aim of this work is to understand the distribution of minerals by obtaining a shallow velocity structure around the Karatungk(喀拉通克) region.Data were acquired in 2009 by a denser array in deploying a transportable seismometer with 4.5 Hz vertical geophone.All the P-wave arrival times are picked automatically with Akaike information criterion,and then checked man-machine interactively by short-receiver geometry.The database for local active-source tomographic in-version involves 4 241 P-wave arrival ... 相似文献
992.
Guo-Ping Wang Xiao-Fei Yu Jian Wang Hong-Mei Zhao Kun-Shan Bao Xian-Guo Lu 《Environmental Earth Sciences》2011,62(1):207-216
The rare earth elements (REEs) in the sediments of the Xianghai wetlands were measured by inductively coupled plasma spectrometry.
The REEs accumulation rates in two sedimentation cores derived from the riparian and depressional marshes were determined
by 210Pb method. The results showed that REEs concentrations in the Xianghai wetland sediments (∑REEs, 116 mg kg−1) were lower than the corresponding values in Chinese soils (181 mg kg−1) and river sediments (∑REEs, 158–191 mg kg−1). Under alkaline conditions (with pH, 8.2–10.3), the light REEs were more enriched than the heavy REEs. Cerium is the predominant
element, and accounts for 30–33% of the total REEs. REEs in the depressional marsh sediments were relatively high (∑REEs,
127 vs. 104 mg kg−1), especially light REEs contents. A significantly positive correlation was found between the neighboring elements except
Pr and Dy. The different types of vertical distribution of REEs between the riparian and the depressional marsh can partly
result from long-term differing hydrological regimes. Generally, depressional marsh had accumulated much more REEs than riparian
marsh (the mean accumulation rates of ∑REEs, 102.98 vs. 48.89 μg cm−2 year−1). 相似文献
993.
浙江煤炭地质局勘探一队主要从事地质勘查及延伸业、机械制造业二大产业,按目前设备分类方法,二大产业占有设备净值分别为40%和60%,但二者创造的经营收入及利润却相差悬殊,设利比(设备余值与利润比值)高达190倍,可见地质勘查及延伸业仍是浙江煤炭地质局勘探一队目前的主要经营方向,而未取得理想效果的机械制造业仍有巨大的潜力。通过对生产设备的综合分析,提出了根据设备构成、设备新度系数、设备完好率等诸多因素分析其对地勘单位发展潜力影响的新方法。 相似文献
994.
995.
The influence of the asymmetric structure of hurricane wind field on storm surge is studied with five types of numerical experiments using a three-dimensional storm surge model. The results from the case of Hurricane Floyd (1999) show that Floyd-induced peak surge would have been much higher had the region of maximum wind rotated 30–90° counterclockwise. The idealized cases (the hypothetical hurricanes) with a wind speed asymmetry of 20 m s?1 show that the peak (negative) surge varied from 4.7 to 6.0 m (?5 to ?5.7 m) or equivalent to ?8.8% and 16.3% (2.8% and ?10.4%) differences as compared to the control experiment. The area of flooding varied from 3552 to 3660 km2. The results from two other idealized cases of varying degree of wind speed asymmetry further show that with decreasing (increasing) asymmetry of wind fields, the variations of peak surge and peak negative surge caused by the rotation of wind fields decrease (increase) accordingly. The results suggest that in storm surge simulations forced by winds derived from balanced models, considerable uncertainty in storm surge and inundation can result from wind asymmetries. This is true even if all other storm parameters, including maximum wind speed, the radius of maximum winds (storm size), minimum central pressure, storm translation speed, drag coefficient, and model settings (domain size and resolution) are identical. Thus, when constructing ensemble and probabilistic storm surge forecasts, uncertainty in wind asymmetry should be considered in conjunction with variations in storm track, storm intensity and size. 相似文献
996.
采用RT-PCR方法,研究了促性腺激素受体(FSHR和LHR)基因在雄性半滑舌鳎繁殖周期中的季节表达规律。结果表明,FSHR mRNA在雄鱼精巢、脑和脾中及LHR mRNA在雄鱼的精巢和脾中均呈季节规律性变化。3月份样品中,FSHR mRNA在精巢表达量最低,12月份,表达量最高;FSHR mRNA在脑中表达模式与精巢... 相似文献
997.
998.
Evaporation loss from the saturated soil beneath drip irrigation emitters highly influences the irrigation efficiency of drip irrigation (DI). Subsurface drip irrigation (SDI) is one good approach to curb this inefficiency, but in a new irrigation method, straight tube irrigation (STI), the irrigation tubes do not need to be buried and thus STI is recommended to increase the irrigation efficiency under normal surface-applied DI. STI consists of only connectors and water-transference tubes that can directly transfer irrigation water from the lateral emitters in the drip line to the root zone of plants. Five-month field experiments were carried out in Aeolian sand soil in the forest-belts of the Taklimakan Desert, which have poor water storage capacity, to compare the potential water saving between STI and DI. The preliminary results showed that, compared with DI, STI (1) improved the soil water content in soil depths from 40 to 100 cm under the soil surface; (2) achieved the same irrigation effects in relatively shorter irrigation durations; (3) had very little water loss due to deep seepage; and (4) formed a layer of dry sand about 10 to 30 cm thick immediately below the soil surface, which lessened evaporation loss of soil water beneath the emitters on the soil surface. This demonstrates that STI can maximize the water-saving potential of DI through the reduction of wetted soil perimeters on the soil surface. This is valuable information for water-saving engineering applications and projects with STI in arid and semiarid regions. 相似文献
999.
1000.
Dispersion of guided waves in thin anisotropic waveguides 总被引:1,自引:0,他引:1