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991.
旅游产业集群形成条件与识别方法 总被引:1,自引:0,他引:1
根据"产业集聚"和"产业联系"两个识别旅游集群存在的标准,结合旅游业的特点,从旅游资源空间集聚条件、旅游要素集中度和集聚效果3个方面构造区位熵指数,再根据投入产出表,用主成份分析法,确定旅游产业联系,计算产业联系密度,最后结合区位熵指数和产业联系密度,得出旅游产业集群度,同时分析旅游产业集群的形成条件,有利于制定政策引导促进旅游产业发展. 相似文献
992.
应用2×12阶高精度交错网格有限差分法,建立了震源位于自由表面时模拟瑞雷波的边界条件,通过对均匀半空间模型模拟得到的结果与解析解完全一致,证明了波场模拟的正确性.针对模拟得到的波场记录,从瑞雷波的传播速度、传播深度、能量衰减和频散特性等几个方面进行了分析,从波场模拟的角度完全证实了弹性波传播理论中的瑞雷波传播特征,加深了对瑞雷波传播过程的认识.在均匀介质模拟的基础上,对含有软弱夹层的三层介质模型进行了模拟,获得了更加接近实际情况的地震记录.为进一步开展对高模式下瑞雷波的反演研究和促进对瑞雷波勘探的应用提供了有益的帮助. 相似文献
993.
CaiNeng Zou ShiZhen Tao XiangXiang Zhang DongBo He ChuanMin Zhou XiaoHui Gao 《中国科学D辑(英文版)》2009,52(8):1068-1090
Based on the analysis of the geological characteristics and controlling factors, we analyzed the formation mechanism of different
types of gas reservoirs. The main characteristics of gas provinces with low porosity and permeability are mainly as follows:
large area, low abundance, small gas pools and large gas provinces; widely distributed excellent hydrocarbon source rocks
with closely contacted source-reservoir-cap association; development mainly in large continental depressions or in paralic
shallow-river delta systems; many kinds of traps coexisting in large areas, dominantly para-layered lithologic, digenetic
and capillary pressure traps; double fluid flow mechanisms of Darcy flow and non-Darcy flow; complicated gas and water relations;
and having the resource distribution of highly productive “sweet spots”, banding concentration, and macroscopically large
areas integrated. The main controlling factors of large sandstone gas provinces with low porosity and permeability are stable
dynamic backgrounds and gentle structural frameworks which control the extensive distribution of alternate (interbedded) sandstones
and mudstones; weak hydropower of large gentle lake basins controlling the formation of discontinuous, low porosity and permeability
reservoirs in shallow-water deltas; regionally differential diagenesis and no homogeneous digenetic facies controlling the
development of favorable reservoirs and digenetic traps; and weak and dispersive reservoir-forming dynamic forces leading
to the widely distributed small traps with low abundance. Low porosity and permeability gas provinces with different trap
types have different formation mechanisms which include fluid diversion pressure difference interactive mechanism of lithologic-trap
gas accumulations, separated differential collection mechanism of digenetic-trap gas accumulations, and the Non-Darcy flow
mechanism of capillary-pressure gas accumulations.
Supported by PetroChina Science and Technology Project (Grant No. 07-01C-01-07) and Youth Innovation Fund Project (Grant Nos.
10100042KT96, 07-06D-01-04-01-03) 相似文献
994.
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996.
Morphologic and sedimentologic patterns of active aeolian dune‐fields on the east coast of Maranhão,northeast Brazil 下载免费PDF全文
The eastern portion of the Maranhão coast is characterized by large active dune‐fields located in a tropical setting. This article combines the analysis of dune‐field morphologic patterns with the classical analysis of grain size and heavy minerals to study the sedimentary dynamics of the active aeolian system in this region. Based on the heavy mineral analysis, the main sedimentary suppliers feeding the system are the westward alongshore drift bringing sand from the coast east of the Parnaíba River mouth and the river itself. The absence of well‐defined variation patterns of the two morphometric parameters studied, dune spacing and crest length, reflects complex sedimentary dynamics and transport pathways, inside the aeolian system, despite the unidirectional wind. During the wet season, the interdune plains are flooded and the system is intensely reworked by intermittent drainages. During the dry season, the deposits formed by the drainages and interdune lakes become temporary internal sedimentary sources for the system. Due to this combined aeolian‐fluvial transport, the sediment source area has a planar geometry, with contributions from the beach and interdune plains, and not linear as expected in a typical case of source only in the beach. The areal limits of the dune‐fields is the main boundary condition controlling the dune‐field patterns, as dune spacing and crest length, by changing the sedimentary inflow–outflow balance and interactions between migration dunes. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
997.
Historically unprecedented erosion from Tropical Storm Irene due to high antecedent precipitation 总被引:1,自引:0,他引:1 下载免费PDF全文
Lacustrine sediment archives indicate that flooding during Tropical Storm Irene (2011) in the north‐eastern United States caused the most severe erosion of any flood in the historic record, surpassing that of events with greater precipitation and peak discharges. Compared to deposition from historic floods, Irene's event layer was more massive and more enriched in unweathered upland sediments, indicating an anomalously high incidence of mass wasting and sediment entrainment. Precipitation records indicate that neither precipitation intensity nor total accumulation distinguished Irene from less erosive historic floods. However, cumulative precipitation prior to Irene exceeded the 95th percentile of all days in the record. When allowing for non‐stationarity in the twentieth century background precipitation, we find a four‐fold increase in the probability of Irene‐like conditions, where impacts of extreme rainfall are enhanced by high antecedent precipitation. We conclude that irrespective of increases in extreme precipitation, the risk of highly erosive flooding in the region is increasing due to the influence of wetter baseline conditions associated with a changing climate. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
998.
This paper presents a non-linear finite element study to back-interpret the free field seismic response recorded at the Lotung Large-Scale Seismic Test site. The study is carried out in the time domain by the Finite Element (FE) code PLAXIS 3D, considering the vertical wave propagation of both the horizontal components of motion. The non-linear soil behaviour is simulated through a constitutive model, the Hardening Soil model with Small-Strain Stiffness (HSsmall), capable of describing the cyclic response of the material at different strain levels. In the paper, the constitutive response of the HSsmall model is firstly investigated through numerical simulations of strain-controlled cyclic shear tests under single and multi-directional conditions at low strain levels. Then, it is adopted to back-analyse the recorded free field seismic response, comparing the FE numerical results to the in-situ down-hole and surface signals recorded during two earthquakes occurred on May 20th and July 17th 1986, characterized by different peak ground accelerations. 相似文献
999.
Etienne Mémin 《地球物理与天体物理流体动力学》2014,108(2):119-146
We present a derivation of a stochastic model of Navier Stokes equations that relies on a decomposition of the velocity fields into a differentiable drift component and a time uncorrelated uncertainty random term. This type of decomposition is reminiscent in spirit to the classical Reynolds decomposition. However, the random velocity fluctuations considered here are not differentiable with respect to time, and they must be handled through stochastic calculus. The dynamics associated with the differentiable drift component is derived from a stochastic version of the Reynolds transport theorem. It includes in its general form an uncertainty dependent subgrid bulk formula that cannot be immediately related to the usual Boussinesq eddy viscosity assumption constructed from thermal molecular agitation analogy. This formulation, emerging from uncertainties on the fluid parcels location, explains with another viewpoint some subgrid eddy diffusion models currently used in computational fluid dynamics or in geophysical sciences and paves the way for new large-scales flow modeling. We finally describe an applications of our formalism to the derivation of stochastic versions of the Shallow water equations or to the definition of reduced order dynamical systems. 相似文献
1000.