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841.
过对鲁西东部中下寒武统研究表明:利用δ13C和δ18O以及Sr,Ni,V,Ba,B元素地球化学特征,不仅可以判断沉积古气候、古盐度、古水温、氧化-还原条件,而且还能提供海平面变化旋回及暴露-间断面确立的依据。研究证明此方法是非常有效的。 相似文献
842.
YU Xuexiang associate professor Ph.D Department of Resource Environment Engineering Anhui University of Science Technology Huainan China. XU Shaoquan GAO Wei LU Weicai 《地球空间信息科学学报》2003,6(4):51-56
A new similar singledifference mathematical model ( SS-DM) and its corresponding algorithm are advanced to solve the deformation of monitoring point directly in single epoch. The method for building the SSDM is introduced in detail, and the main error sources affecting the accuracy of deformation measurement are analyzed briefly, and the basic algorithm and steps of solving the deformation are discussed. In order to validate the correctness and the accuracy of the similar single-difference model, the test with five dual frequency receivers is carried out on a slideway which moved in plane in Feb. 2001. In the test, five sessions are observed. The numerical results of test data show that the advanced model is correct. 相似文献
843.
Observational estimation of heat budgets on drifting ice and open water over the Arctic Ocean 总被引:9,自引:0,他引:9
It is of major scientific interests to determine the parameters of momentum, heat and vapor exchange in the planetary boundary layer in order to study the effects of ocean-ice-atmosphere interactions and their feedback mechanisms on global climate[1]. Lin… 相似文献
844.
名铁矿中三氧化二铝含量测定的方法研究 总被引:1,自引:0,他引:1
名铁矿试样经碱熔,直接分离铁,再酸化,中和后用六次甲基四胺沉淀铝与络合物,沉淀酸溶,用氟盐取代-EDTA容量法测定三氧化二铝。该法充分消除了铁的干扰,使滴定终点比DZG93-012(铬铁矿操作规程-氟盐取代)-EDTA容量法测定三氧化二铝)方法的滴定终点更清晰,准确,结果重现性好。 相似文献
845.
高精度国际时间比对的进展 总被引:12,自引:0,他引:12
在过去的45yr中原子频标的性能大约每7yr提高一个数量级,从国际标准时间和各国高精度守时的需要出发,远距离的高精度时间频率传递比对技术也有与之相适应的很大的发展。GPS卫星在近20yr中不仅成为导航定位不可缺少的工具,在时间、频率的方面也发挥出巨大威力;近年来多通道“全视接收”技术的发展钎时频传输比对的稳定性有了重大改善;GLONASS卫星系统在高精度时间比对方面正在成为GPS系统的重要补充手段 相似文献
846.
半拉格朗日、半隐式欧拉方程组大气数值模式研究 总被引:2,自引:1,他引:1
介绍了一个具有较高时间积分效率的三维弹性大气数值模式。其中,控制方程为能够描述大气非静力及可压缩性的欧拉方程组,时间积分采用了高效率的“半拉格朗日、半隐式”方案。通过引用一个简化的“云物理过程”参数化方案,针对大气中深厚湿对流过程的若干问题进行了数值试验,结果表明,模式能够对该过程中的一些基本和复杂现象进行有效地模拟。试验结果还表明,动力学框架具有很好的稳定性,能够实现高效率的时间积分,它还具有较好的频散特性,保证了空间计算的精度,从而完好地描述了风暴的形态。 相似文献
847.
848.
急性颈椎损伤的CT诊断 总被引:2,自引:1,他引:1
本文目的是分析急性颈椎损伤(ACT)的CT征象,评价CT在ACT诊断中的价值及限度。方法:78例颈椎外伤患者行平片、薄层CT检查及三维重建,并做对照分析。结果经影像学诊断60例ACT,CT诊断59例,1例CT阴性而由平片确诊 1例。平片与CT的骨折检出率分别为 53. 3%和 98.3%。结论:CT比X线平片可发现更多的骨折,并能明确骨折块与椎管的关系。这对临床处理严重颈椎损伤起到指导作用。 相似文献
849.
Fluid inclusion studies of 5 gold deposits connected with alkaline rocks show that quartz separated from auriferous quartz veins contains abundant three-phase CO2-NaCl-H2O inclusions and two-phase CO2-dominated ones,measuring 5-20um in diameter,Homogenization temperatures of the fluid inclusions are mostly within the range of 150-300℃,and the salinities,mainly 0.2wt%-12 wt%(NaCl),Gold mineralizations occurred at depths of 1.4-2.8km,The most striking character of fluid composition is that among the cations,Na^ in dominant,followed by K^ ,Ca^2 ,among the anions,Cl^- is slightly higher than SO4^2-,In the evaporate,H2O is dominant,followed by CO2,The pH values are mainly within the range of 6.5-8.5,indicating that the ore-forming solutions are alkaline in nature.The hydrogen and oxygen isotopic ratios indicate that the ore fluid is composed mainly of magmatic water.With the dropping of temperature in the ore fluid,the contents of CO2 decreased while the salinity increased.The relations between Au and other components of the ore fluid are discussed in the paper,and it is concluded that in these deposits,Chlorides,H2S,SiO2,CO2,etc.in the fluid all are involved in the migration and concentration of Au. 相似文献
850.
Data from flume studies are used to develop a model for predicting bed‐load transport rates in rough turbulent two‐dimensional open‐channel flows moving well sorted non‐cohesive sediments over plane mobile beds. The object is not to predict transport rates in natural channel flows but rather to provide a standard against which measured bed‐load transport rates influenced by factors such as bed forms, bed armouring, or limited sediment availability may be compared in order to assess the impact of these factors on bed‐load transport rates. The model is based on a revised version of Bagnold's basic energy equation ibsb = ebω, where ib is the immersed bed‐load transport rate, ω is flow power per unit area, eb is the efficiency coefficient, and sb is the stress coefficient defined as the ratio of the tangential bed shear stress caused by grain collisions and fluid drag to the immersed weight of the bed load. Expressions are developed for sb and eb in terms of G, a normalized measure of sediment transport stage, and these expressions are substituted into the revised energy equation to obtain the bed‐load transport equation ib = ω G 3·4. This equation applies regardless of the mode of bed‐load transport (i.e. saltation or sheet flow) and reduces to ib = ω where G approaches 1 in the sheet‐flow regime. That ib = ω does not mean that all the available power is dissipated in transporting the bed load. Rather, it reflects the fact that ib is a transport rate that must be multiplied by sb to become a work rate before it can be compared with ω. It follows that the proportion of ω that is dissipated in the transport of bed load is ibsb/ω, which is approximately 0·6 when ib = ω. It is suggested that this remarkably high transport efficiency is achieved in sheet flow (1) because the ratio of grain‐to‐grain to grain‐to‐bed collisions increases with bed shear stress, and (2) because on average much more momentum is lost in a grain‐to‐bed collision than in a grain‐to‐grain one. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献