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881.
准噶尔是新疆北部古生代造山带的重要组成部分,以广泛发育晚古生代花岗岩为特征,是中亚造山带总显生宙陆壳生长作用非常显著的地区之一。根据最新获得的LA-ICP-MSU-Pb锆石年龄,木斯塔巴岩体锆石年龄为(303±2.0) Ma(晚石炭世),岩石地球化学分析,岩石具高硅(66.04%~70.4%),高碱(2.26~2.87),高铝(13.25%~15.46%),高钾(3.4%~4.58%),低镁,A/CNK=1.06~1.22,低固结(6.34~12.87),高分异(78.35~84.5),富轻稀土(LREE/HREE=3.57~12.97)和大离子亲石元素K,Rb,Ba,Sr,亏损高场强元素Nb,Ta,Ti,P,为过铝质高钾钙碱性系列花岗岩,具碰撞花岗岩特征,属额尔齐斯构造带的重要组成部分,其形成与板块俯冲作用关系密切。本区石炭纪花岗岩的数据与北准噶尔地区对比,显示晚石炭世额尔齐斯构造带闭合,进入后碰撞阶段。 相似文献
882.
介绍了广东省ADP数字地震前兆综合观测台网中心系统的构成、功能以及运行情况。 相似文献
883.
基于三角网格的有限差分法叠后逆时偏移 总被引:1,自引:1,他引:0
Compared with other migration methods, reverse-time migration is based on a precise wave equation, not an approximation, and performs extrapolation in the depth domain rather than the time domain. It is highly accurate and not affected by strong subsurface structure complexity and horizontal velocity variations. The difference method based on triangular grids maintains the simplicity of the difference method and the precision of the finite element method. It can be used directly for forward modeling on models with complex top surfaces and migration without statics preprocessing. We apply a finite difference method based on triangular grids for post-stack reverse-time migration for the first time. Tests on model data verify that the combination of the two methods can achieve near-perfect results in application. 相似文献
884.
885.
“前兆区域台网中心数据整理软件”是应广东省区域前兆台网中心的工作需要而研发的,其功能包括监控日(月)报、压缩包、电报码文件、省局数据汇集,数据入库,日志系统.备忘和辅助系统。软件满足了前兆值班工作的需求,提高了工作效率。 相似文献
886.
Construction of regional and local seismic anisotropic structures from wide-angle seismic data: crustal deformation in the southeast of China 总被引:10,自引:0,他引:10
We present a method to obtain spatial distributions of seismic anisotropy associated with regional stress and local faulting
in the crust from wide-angle seismic data. The method contains three steps. The first step consists of obtaining radial- and
transverse-component seismic sections using a pre-stack depth migration algorithm from the S-wave velocity model determined
by conventional interpretation of picked intra-crustal seismic events. In the second step, we compute time delays between
split shear-waves and polarizations of fast split shear-waves by minimizing the transverse-component seismic energy. The time
delay and polarization in each layer are derived using a layer-stripping method. The final step is to estimate the average
splitting parameters along the whole profile. Thus, the average time delay and polarization can be regarded as caused by the
effects owing to regional structure and stress fields, whereas the residual values of the splitting parameters are considered
to be related to local structures and local faulting. Our method allows us to construct multi-layer anisotropic images, which
may later be interpreted in terms of intra-layer coupling/decoupling or deformation. We present results from a set of three-component
seismic data acquired by a controlled source experiment in the southeast region of China. The results demonstrate that the
average polarizations and time delays are consistent with the direction and strength of the stress field, and their lateral
variations related to local anisotropy match the spatial distribution of surface faulting crossing the acquisition seismic
profile. 相似文献
887.
Constraining the anisotropy structure of the crust by joint inversion of seismic reflection travel times and wave polarizations 总被引:2,自引:0,他引:2
In the context of wide-angle seismic profiling, the determination of the physical properties of the Earth crust, such as the
elastic layer depth and seismic velocity, is often performed by inversion of P- and/or S-phases propagation data supplying
the geometry of the medium (reflector depths) or any other structural parameter (P- or S-wave velocity, density...). Moreover,
the inversion for velocity structure and interfaces is commonly performed using only seismic reflection travel times and/or
crustal phase amplitudes in isotropic media. But it is very important to utilize more available information to constrain the
non-uniqueness of the solution. In this paper, we present a simultaneous inversion method of seismic reflection travel times
and polarizations data of transient elastic waves in stratified media to reconstruct not only layer depth and vertical P-wave
velocity but also the anisotropy feature of the crust based on the estimation of the Thomsen’s parameters. We carry out
a checking with synthetic data, comparing the inversion results obtained by anisotropic travel-time inversion to the results
derived by joint inversion of seismic reflection travel times and polarizations data. The comparison proves that the first
procedure leads to biased anisotropic models, while the second one fits nearly the real model. This makes the joint inversion
method feasible. Finally, we investigate the geometry, P-wave velocity structure and anisotropy of the crust beneath Southeastern
China by applying the proposed inversion method to previously acquired wide-angle seismic data. In this case, the anisotropy
signature provides clear evidence that the Jiangshan-Shaoxing fault is the natural boundary between the Yangtze and Cathaysia
blocks. 相似文献
888.
太原市地层空间异质性对地面沉降分布的影响 总被引:4,自引:0,他引:4
对比1956~2000年太原市地下水位与地面沉降资料发现,该区地面沉降漏斗与地下水位降落漏斗的空间分布基本相近,但不完全吻合,局部地区存在偏移。通过对黏性土层累计厚度分布、黏性土层与粗颗粒土层的组合特征、不同分区各深度处土的力学特征值与上述偏移的对比分析,认为太原市地层的空间异质性对地面沉降分布有如下影响:(1)与地下水位降落漏斗相比,地面沉降漏斗偏向于黏性土层较厚的一侧;(2)地层组合(黏性土的夹层数、单层厚度等)对地面沉降的空间分布影响较大,沉降多发生在黏性土夹层多、单层厚度较小的地区;(3)土的力学性质的差异是影响沉降分布的重要因素。 相似文献
889.
Microbial carbonates in Holocene beachrocks,Shuiweiling, Luhuitou Peninsula,Hainan Island 总被引:2,自引:0,他引:2
Two research methods, geomicrobiology and carbonate sedimentology, were adopted to study the microbial carbonates in the beachrocks, Shuiweiling, Luhuitou, Sanya City, Hainan Island. The results indicate that microbial carbonates occur in Shuiweiling beachrocks and cements related to microbial activitives are common. Microbial carbonates were mainly developed on the surfaces of coral skeletons and within the coral (fragments and shivers) skeletal cavities,and rarely grew in interspaces formed by coral and other biological detritus. The growth morphologies of microbial carbonates are various, including stromatolitic lamination, thin crusts, dome-like, and microbialites. Microbial carbonates commonly trap fine-sized bioclasts, contain tubular filaments, and show laminated growth striation. Microbial carbonates within the coral skeletal cavities are generally stromatolitic cone-shaped, with a random growth direction along the bearing of trend of cavities, showing distinct growth laminae and recognizable growth phases. It is a special growth pattern of crypt microbial carbonates. Microbial cements occur mainly in shape of needle cement, calcified filaments, microborings, and calcified framboidal spheres. The needle cement is the most common type. These microbial cements indicate that microbial activities and microbial carbonates played an important role in beachrock formation in which carbonates were dominant components and the climate of tropical ocean monsoon was influential. Such microbial carbonates and microbial cementation have not been reported here from beachrocks along the northern shorelines of the South China Sea. The results support a clear microbial origin for certain carbonate cements in beachrocks, confirm that microbial carbonates are a significant contributor to carbonate sedimentation, and widen the knowledge of beachrocks from a new field. 相似文献
890.
放射性核素在地下介质中迁移机理与模型研究 总被引:5,自引:0,他引:5
介绍了铀尾矿库的物理、化学概念模型和其中重金属、放射性核素迁移的一般过程 ;论述了沉淀作用、络合作用和胶体作用对放射性核素迁移的影响 ;重点讨论了描述吸附作用的离子交换模型和表面络合模型的建模机理 ;对定量模拟放射性核素迁移行为的 Kd模型、表面络合模型及“反应 -运移模型”的应用进行了评述。 相似文献