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91.
ABSTRACT From data obtained at stations set up in Chad, the Central African Republic and Congo-Brazzaville, stretching from the desert to the equatorial zone, it has been possible to compare measurements of evapotranspiration and of evaporation with results obtained by using the energy-balance method. Several difficulties arise in these comparisons since the scale of the measurements (small evaporating surfaces) is generally different from that of the climatic characteristics on which evaporation is dependent. After proposing a model to resolve this problem and fitting the empirical coefficients of Penman's formula, the author has applied this formula to some results derived for stations in Congo-Brazzaville; the potential evapotranspiration calculated in this way is in good agreement with water balance data. At these stations the evapotranspiration energy may be a constant percentage of global short-wave radiation. Finally, the energy-balance method has been used at Brazzaville to measure the actual evapotranspiration over grass during the dry season. The result is that actual and potential evapotranspiration were found to be closely related. These results indicate the importance of solar readiation in the field of hydrometeorology. 相似文献
92.
E.Wanda GEORGE 《资源与生态学报(英文版)》2013,4(3):275-284
加拿大新斯科舍省的大草地是传统土地利用的杰出例子,反映了人类与独特环境相互作用,也因此被联合国教科文组织列入世界遗产名录。大草地不但是加拿大最肥沃的农业景观,还是一个标志性历史遗址,承载着1755年的驱逐阿卡迭人的历史悲剧,吸引了无数游客慕名而来。而今面临着农业的转变和旅游业的衰败双重威胁,人们对大草地于2012年成为世界遗产及其所带来的旅游发展充满期待。本文将大草地作为全球重要农业文化遗产,根据以前的研究,对其成为世界遗产地之后该地区未来经济繁荣和可持续发展的情况进行了探讨。 相似文献
93.
Abstract. Reproductive parameters of the females of Penaeus semisulcatus regarding the process of ovary maturation, the degree of synchronization of the ova maturation stage within an ovary, the correlation between female length and both maturity and fecundity, as well as the relationship between moulting, copulation and ovarian maturity stage were investigated.
The seasonal and spatial pattern of the reproduction of the female population of P. semisulcatus along the southeastern coast of the Mediterranean was determined.
Average ova diameter, morphological appearance of the ova, presence of sperm, characteristics of the spermatophore, and hardness of the cuticle were used in order to study the above parameters. 相似文献
The seasonal and spatial pattern of the reproduction of the female population of P. semisulcatus along the southeastern coast of the Mediterranean was determined.
Average ova diameter, morphological appearance of the ova, presence of sperm, characteristics of the spermatophore, and hardness of the cuticle were used in order to study the above parameters. 相似文献
94.
Abstract. Recruitment, migration, growth and longevity of populations of Penaeus semisulcatus along the southeastern coast of the Mediterranean were investigated. The general pattern of the life cycle of P. semisulcatus and the parameters affecting it were identified.
Relative population density, measured by catch per unit effort, as well as relative age estimated by age group body length were used to study the pattern of the benthic phase of the life cycle. 相似文献
Relative population density, measured by catch per unit effort, as well as relative age estimated by age group body length were used to study the pattern of the benthic phase of the life cycle. 相似文献
95.
GEORGE B.BARBOUR. 《地质学报》1923,2(Z1):35-78
Ⅰ. INTRODUCTION. "One of the striking features in the Tsinan plain is a group ofisolated hillocks standing up boldly from it. Though mainly overgrown withvegetation, they are distinguishable by ther shape and dark colour from thelight-grey tabular limestone islands which for the last outposts pushedforward by the mountains lying to the south." 相似文献
96.
The geophone spurious frequency is modeled as the resonance of the planar motion of a spider spring carrying a moving mass. An analytic solution is found using the Castigliano method by assuming that the spring arm is a single-mode vibrating cantilever beam. The spring shape is found from this analysis. When the typical spring has a circumferentially varying cross-section, the Castigliano method is no longer applicable. A dimensional analysis is used as an approximate method for general design. Based on the theoretical result, a rotational fixture and a translational fixture were designed for experimental purposes. A low-noise fixture and a phase-averaging technique provide the amplitude and spurious resonance in the frequency domain. Finally, a test is run by using a rotational fixture to compare with the approximate method of spurious frequency prediction. Very good agreement between prediction and experiment is found. 相似文献
97.
98.
It is usually believed that we know everything to be known for any separable Hamiltonian system, i.e. an integrable system
in which we can separate the variables in some coordinate system (e.g. see Lichtenberg and Lieberman 1992, Regular and Chaotic Dynamics, Springer). However this is not always true, since through the separation the solutions may be found only up to quadratures,
a form that might not be particularly useful. A good example is the two-fixed-centers problem. Although its integrability
was discovered by Euler in the 18th century, the problem was far from being considered as completely understood. This apparent
contradiction stems from the fact that the solutions of the equations of motion in the confocal ellipsoidal coordinates, in
which the variables separate, are written in terms of elliptic integrals, so that their properties are not obvious at first
sight. In this paper we classify the trajectories according to an exhaustive scheme, comprising both periodic and quasi-periodic
ones. We identify the collision orbits (both direct and asymptotic) and find that collision orbits are of complete measure
in a 3-D submanifold of the phase space while asymptotically collision orbits are of complete measure in the 4-D phase space.
We use a transformation, which regularizes the close approaches and, therefore, enables the numerical integration of collision
trajectories (both direct and asymptotic). Finally we give the ratio of oscillation period along the two axes (the ‘rotation
number’) as a function of the two integrals of motion.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
99.
Geochemical and Isotopic (O, Nd, Pb and Sr) Constraints on A-type Granite Petrogenesis Based on the Topsails Igneous Suite, Newfoundland Appalachians 总被引:22,自引:2,他引:22
WHALEN JOSEPH. B.; JENNER GEORGE A.; LONGSTAFFE FREDERICK J.; ROBERT FRANCINE; GARIPY CLMENT 《Journal of Petrology》1996,37(6):1463-1489
The voluminous, bimodal, Silurian Topsails igneous suite consistsmainly of A-type peralkaline to slightly peraluminous,hypersohnis to subsolvus granites with subordinate syenite,onzonite and diabase, plus consanguineous basalts and highsilicarhyolites. Nd(T) values from the suite range from 1.5to +5.4; most granitoid components exhibit positive Nd(T) values(+1.1 to +3.9). Granitoid initial 87Sr/86Sr and most 18 O valuesare in the range expected for rocks derived from mantle-likeprotoliths (0.7010.706 and +6 to +80/). Restricted 207Pb/204Pbvariation is accompanied by significant dispersion of 206Pb/204Pband 208Pb/204Pb. Superficially, petrogenesis by either direct(via fractionation from basalt) or indirect (via melting ofjuvenile crust) derivation from mantle sources appears plausible.Remelting of the granulitic protolith of Ordovician are-typegranitoids can be ruled out, because these rocks exhibit negativeNd(T) and a large range in 207Pb/204Pb. Geochemical and isotopicrelationships are most compatible with remelting of hybridizedlithospheric mantle generated during arc-continent collision.A genetic link is suggested among collision-related delaminationor slab break-off events and emplacement of post-erogenicgranite suites. A-type granites may recycle previously subductedcontinental material, and help explain the mass balance notedfor modern arcs. However, they need not represent net, new,crustal growth. KEY WORDS: A-type granites; juvenile crust; isotopes; Newfoundland
*Telephone: (613) 995-4972. Fax: (613) 995-7997. e-mail: jwhalen{at}gsc.emr.ca 相似文献
100.
GEORGE B.BARBOUR 《地质学报》1931,(1)
Introduction The Locality General Geological Structure Stratigraphy Physiography and Structure Age of the Taiku Fault Bearing of the Character of the Deposits on the Problem of Sanmenian Climate Correlation of Pleistocene Climatic Fluctuations 相似文献