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131.
Observations from the Horizontal Array Turbulence Study (HATS) field program are used to examine the attenuation of measured
scalar fluxes caused by spatial separation between the vertical velocity and scalar sensors. The HATS data show that flux
attenuation for streamwise, crosswind, and vertical sensor displacements are each a function of a dimensionless, stability-dependent
parameter n
m
multiplied by the ratio of sensor displacement to measurement height. The scalar flux decays more rapidly with crosswind
displacements than for streamwise displacements and decays more rapidly for stable stratification than for unstable stratification.
The cospectral flux attenuation model of Kristensen et al. agrees well with the HATS data for streamwise sensor displacements,
although it is necessary to include a neglected quadrature spectrum term to explain the observation that flux attenuation
is often less with the scalar sensor downwind of the anemometer than for the opposite configuration. A simpler exponential
decay model provides good estimates for crosswind sensor displacements, as well as for streamwise sensor displacements with
stable stratification. A model similar to that of Lee and Black correctly predicts flux attenuation for a combination of streamwise
and crosswind displacements, i.e. as a function of wind direction relative to the sensor displacement. The HATS data for vertical
sensor displacements extend the near-neutral results of Kristensen et al. to diabatic stratification and confirm their finding
that flux attenuation is less with the scalar sensor located below the anemometer than if the scalar sensor is displaced an
equal distance either horizontally or above the anemometer. 相似文献
132.
133.
HNLC海区间现场加铁实验的比较 总被引:1,自引:1,他引:0
综述了在赤道太平洋、南大洋和亚北极太平洋3个典型的高硝酸盐、低叶绿素a(high-nitrateandlow-chlorophylla,HNLC)海区不同研究小组现场加铁实验的结果,并阐述了铁限制与光限制、硅限制以及浮游动物摄食等其它限制因素之间的关系。加铁后,各海区的浮游植物生物量都增加了,但不同海区的浮游植物生物量、种群结构、颗粒有机碳通量等方面却有不同的响应,因而通过对大洋施铁以缓解大气中CO2增加的设想的可行性还需作进一步验证。 相似文献
134.
《African Journal of Marine Science》2013,35(2):119-124
Namibia’s most important commercial fisheries resource, the shallow-water Cape hake Merluccius capensis, is currently assessed using statistical catch-at-age analysis. Age data obtained from otoliths constitute an important data component of this model. Recent age-validation studies of M. capensis showed that growth was previously underestimated. We investigated this new fast-growth hypothesis (FGH) by using measurements and counts of translucent zones (T1 to T14, from otolith core to edge) on two survey otolith samples covering the entire range of fish lengths. We compared three hypotheses of periodicity of otolith zone formation and show that, if all zones are counted, T2 (at 9.0 mm otolith length), T5, T8, T11 and T14 are most likely to be annuli. A conversion from the slow-growth-hypothesis (SGH, currently used) age data was calculated as: FGH age group = round (0.41[SGH age group] + 0.25), and this formula should be applied to compute and test updated catch-at-age data in a future hake stock assessment. Additional adjustment for the hake stock assessment following the FGH, such as the timing of recruitment in winter and catches in summer, should be considered in future assessments. 相似文献
135.
地球科学中大地构造理论假说争论的历史经历了山脉臆说的“实在论”与“唯名论”的探索、“塌陷说”与“隆起说”对立时期以及受“形而上学”和“自然哲学”的影响这一过程。“收缩说”统治时期,“机械唯物主义”阻碍了“自然辩证法”的指导;“活动论”兴起后,并未找到先进的地学哲学武器。中国古代有机论自然观蕴藏了丰富的地学哲学思想-有机论辩证唯物主义的天地生整体自然观。“立地之道,曰柔与刚”,“合乎谓之坤,辟乎谓之乾,一合一辟谓之变”,“刚柔相摩,八卦相摩,八卦相荡”等精辟论述。早已从地质哲学高度,把“威尔逊旋回”、“开合运动”等大地构造假说涵蓄其内。大地构造理论的未来发展必然由此获得新的启迪。 相似文献
136.
Thomas J. Cooke 《The Professional geographer》1996,48(4):458-467
This research tests the spatial mismatch hypothesis by comparing the employment probabilities of central city versus suburban African American males in nine metropolitan areas. Treatment effects models are used to control for the effects of both individual characteristics and residential self-selection on the probability of employment. A positive effect of suburban residential location on employment is found for the residents of Dallas, Los Angeles, New York, and Washington, while no effect is found for the residents of Cleveland, Houston. Jackson, Memphis, and Newark. The general conclusion to be drawn is that the spatial mismatch effect is contingent on the particular characteristics of each metropolitan area. Preliminary analysis shows that metropolitan areas with a spatial mismatch effect are large in terms of total population and total land area, and have less efficient transportation systems. 相似文献
137.
坐标转换模型尺度参数的假设检验 总被引:8,自引:1,他引:8
介绍了基于空间尺度为各向异性的三尺度参数坐标转换模型及其转化形式,从理论上分析了坐标转换中如何对尺度参数进行选择,给出了坐标转换模型中尺度参数假设检验模型的统一表达形式,构造了相应的检验统计量。该检验模型能对三尺度坐标转换模型、双尺度模型和单尺度是的相互转化及尺度参数的显著性等情况进行假设检验。通过该假设检验方法对两算例进行了解算,得出了一些有益的结论。 相似文献
138.
大地震发生的网络性质——兼论有关地震预测的争论 总被引:22,自引:0,他引:22
现有地震形成机制的假说大多是仅考虑震源及其邻近地区的事实依据。文中提出 :大地震的形成机制具有网络特性 ,把大地震看成是多层次网络的节点。一个地震的发生是多种动力 (包括天文因素 )作用的结果。地震形成机制的网络假说能较好地综合已有概念 ,解释地震预测研究中发现许多新现象。从网络假说看近年来“地震能否预测”的争论可有许多新启示。如果应用网络假说 ,至少一部分地震应是可以预测的。 相似文献
139.
NI Jinren WANG Guangqian Dr. of Eng- Dept. of Geography Peking University China Dr. of Eng 《国际泥沙研究》1991,(3)
The problem of sediment concentration distribution in a vertical for channel and pipe flows is studied in this paper. Considering the variation of the vertical component of the fluctuation velocity v as an independent variable, two types of sediment concentration distribution can be derived. However, only one type of distribution is commonly quoted while the other one rarely reported. In this paper explanation for such phenomena is given and conditions for the occurrence of both types are also discussed. 相似文献
140.
魏洲龄 《大地构造与成矿学》1991,15(4):345-357
热能聚散交替假说是地质学说的一个重要组成部分,是用于解析地壳演化和运动机因的新论点。本文通过实例结合研究,经实际检验,证明这一新论点不仅可以用宏观的地热异常表征加以描述,同时可以用微观的量纲给予肯定,它既有深刻的理论意义,又有重大的实际意义。 相似文献