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51.
Prof. Dr. John G. Dennis 《International Journal of Earth Sciences》1969,59(1):222-228
Zusammenfassung Oft wird zwischen Klüften und Verschiebungen ein genetischer Zusammenhang gesehen. Neuere Untersuchungen lassen einen grundsätzlichen Unterschied erkennen: Die gemeinen Klüfte entstehen durch spröden Bruch im Anschluß an eine elastische Deformation; Verschiebungen und ihnen zugeordnete Klüfte gehen zumeist aus einer plastischen Deformation hervor. Auch sind Verschiebungen an begrenzte Zonen gebunden und meist gefügefremd, obwohl sie sich bestehenden Kluftsystemen anpassen können. Die Systeme der gemeinen Klüfte sind dagegen fast gleichmäßig auf weite Bereiche verteilt und passen sich dem bestehenden Gesteinsgefüge an. Zur Deutung der Bruchtektonik sollten deshalb klufttektonische Analysen nur mit äußerster Vorsicht herangezogen werden.
Joints and faults are commonly regarded as genetically related. Recent investigations, however, tend to bring out a fundamental genetic distinction: Common joints form by brittle fracture following elastic deformation; faults result from ductile fracture. Moreover, faults and related joints are restricted to narrow zones and rarely conform with preexisting fabric, while common joints are regionally pervasive and are fabric controlled. When evaluating fracture analyses, therefore, the genetic distinction between common joints and faults must be borne in mind.
Résumé On croit souvent devoir mettre en relation génétique joints et failles. Des études récentes permettent d'y voir une distinction. Les joints banaux proviennent d'une rupture cassante, à la suite d'une déformation élastique. Les failles suivent une rupture plastique. En plus, les failles et les joints qui leur sont apparentés sont restreints à des zones plus ou moins étroites et se conforment rarement à la structure interne de la roche, trandis que les joints banaux ont une distribution régionale, et sont liés à la structure interne. L'analyse des ruptures géologiques doit, par conséquent, tenir compte d'une distinction fondamentale entre joints banaux, et joints apparentés aux failles.
, , : , ; - . , . . - .相似文献
52.
A. T. M. Sakiur Rahman Takahiro Hosono Ozgur Kisi Boateng Dennis A. H. M. Rahmatullah Imon 《水文科学杂志》2020,65(12):1994-2006
ABSTRACT This study aimed to evaluate the potential of the recently introduced Prophet model for estimating reference evapotranspiration (ETo). A comparative study was conducted for benchmarking the model results with support vector regression (SVR) and temperature-based empirical models (Thornthwaite and Hargreaves) in southern Japan. The performance of the Prophet, SVR and temperature-based empirical models was evaluated by Nash–Sutcliffe efficiency (NSE) and coefficient of determination (R2). The results indicate that temperature-based Prophet and SVR models have greater accuracy than the empirical models. The Prophet model with sole input of relative humidity, sunshine hours or windspeed showed acceptable accuracy (NSE > 0.80; R2 > 0.80), while SVR models with similar inputs showed greater errors. Accuracy improved with increasing number of input parameters, giving excellent performance (NSE > 0.95; R2 > 0.95) with all input parameters. Hence, the Prophet model is a new promising approach for modelling ETo with limited input variables. 相似文献
53.
54.
Dennis Rawlins 《Geophysical Journal International》1982,69(1):265-271
Summary. A rigorous method is developed for the exact solution of the extrema of the total tidal field on a spherical celestial body, disturbed by a multiplicity of gravitating point masses distributed in three dimensions at distances large relative to the disturbed body's size. A short program is provided for convenient use of the method. As an illustration, maximal solar tides due to planetary attraction are calculated for the Solar System 1964–1991. 相似文献
55.
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57.
Beach-cast wrack of marine origin is considered a spatial subsidy to the marine-terrestrial transition zone. We found that
the wrack line on sand and gravel beaches of Vancouver Island was frequented by intertidal purple shore crabs,Hemigrapsus nudus (Dana 1851) and densely colonized by detritivorous talitrid amphipods. Amphipods spend the day buried in sand and forage
on beach wrack during the night.H. nudus were found in supratidal wrack putches immediately after nightly high tides in field censuses, but spent most of the day
and ebb tides either submerged subtidally or hidden underneath intertidal rocks and boulders. In feeding trials, intertidal
shore crabs were capable of preying on talitrid amphipods. We considerH. nudus an omnivore feeding on both fresh and decaying macroalgae as well as animal prey. Although living supratidally, amphipods
were significantly preferred over intertidal littorine snails by foraging shore crabs. Handling time of amphipods was significantly
shorter than for littorine snails. While amphipods had a reduced risk of predation byH. nudus when buried in the sand, foraging undern eath wrack patches did not reduce predation pressure on amphipods by shore crabs.
Rates of amphipod consumption by shore crabs were higher at darkness than daylight. In addition to an apparent day-night rhythm,
tidal height and time elapsed since previous high tide had a significant influence on shore crab density wrack. We conclude
that beach-cast wrack acts as a spatial subsidy by virtue of providing a valuable food source to talitrid amphipods, which
are in turn consumed by shore crabs that ride the nightly high tide into supratidal wrack patches to reduce the risk of passing
bare sand on theiry way to a feeding habitat rich in valuable prey. 相似文献
58.
Jeff Standish Dennis Geist Karen Harpp Mark D. Kurz 《Contributions to Mineralogy and Petrology》1998,133(1-2):136-148
Roca Redonda volcano is a mostly submarine shield volcano that rises nearly 3 km from the adjacent seafloor. Over twenty
lava flows and palagonite tuff are exposed in a 60 meter high oblong outcrop above sea level, and several other flows are
exposed in the shallow water surrounding the islet. Thick, slightly alkaline picritic flows form the base of the section.
Thinner picrites interbedded with sparsely porphyritic alkali-olivine basaltic pahoehoe toes characterize the upper section.
The subaerial section probably records the filling of a palagonite tuff cone with younger lavas. Numerous fumaroles that may
have a magmatic component are present in the shallow (<30 m) submarine zone and indicate that the volcano is probably still
active. Three lava types are exposed: the basal picrites with 19% > MgO > 14%, high-Mg basalts with MgO of about 9%, and low-Mg
basalts with MgO of about 6%. The Sr and Nd isotopic ratios of the three lava types are within analytical uncertainty. Olivine
compositions indicate that the picrites are basaltic liquids that have accumulated olivine whose composition is in equilibrium
with the host basaltic liquid. Apparently, basaltic magmas percolated through dunite and troctolite that had crystallized
from slightly older Roca Redonda basaltic magma. Lavas from Roca Redonda have enriched trace element contents and isotopic
ratios relative to nearby Wolf volcano, but they are quite similar to lavas from Cerro Azul and Ecuador volcanoes. The common
characteristic of these volcanoes is that they lie on the periphery of the archipelago and are in a stage of subaerial growth.
This suggests that Galápagos volcanoes may go through a juvenile alkaline stage before a mature tholeiitic stage, analogous
to the Loihi stage of Hawaiian volcanism. A low 3He/4He ratio in olivine from one of the picrites indicates a small contribution by the Galápagos mantle plume.
Received: 15 December 1997 / Accepted: 6 May 1998 相似文献
59.
Electron paramagnetic resonance (EPR) spectroscopy analysis of marine samples from different environments appears to differentiate
between adsorbed and structural Mn (II) and Fe (III) sites in the sediment. This suggests that EPR may provide a means of
distinguishing different environmental influences on sediment. Acid extract solutions from sediment samples exhibit clearly
defined EPR spectra due to Mn(II), Ti(III), Fe(III), and VO(IV), which are amenable to qualitative and quantitative analysis
at concentrations below one part per million. Spectra of several shellfish vary considerably, both between species, and within
a species, depending on sampling localities. Resonances from Mn(II), Mo(V), and Fe(III) can be obtained. Mn(II) is substituted
for Ca(II) in the calcite structure of some shells.
The low detection limits, small sample size, required and identification of oxidation states by EPR complement other analytical
techniques and may prove useful in marine systems. 相似文献
60.
Dennis G. Waslenchuk 《Environmental Geology》1975,1(3):131-136
Once inputs of mercury-bearing effluents to a fluvial system are stopped, levels of contamination will decline slowly to background
values. Crystalline mercury phases will dissolve in response to lowered aqueous mercury concentrations, and aqueous Hg(OH)2 will desorb from ferric hydroxide grain coatings as the coatings age to more ordered phases. In the Ottawa River, mercury
concentrations in bed sediments are declining by about 50 percent annually.
Editor's note: Waslenchuk is now with the Georgia Institute of Technology School of Geophysical Sciences, Atlanta, Georgia
30332, U.S.A. 相似文献