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601.
602.
Daily stream temperatures are needed in a number of analyses. Such analyses might focus on aquatic organisms or industrial activities. To protect aquatic systems, industrial activities, for example, water withdrawals or discharges, are sometimes restricted. To evaluate where new industrial settings should be placed or if climate change will affect already existing industrial settings, the simulation of stream temperature is needed. Stream temperature models with weekly or monthly time scale might not be sufficient for this kind of analysis. Different regression models to simulate daily stream temperature for the river Elbe (Germany) are developed and their performance is estimated. For the calibration period the Nash–Sutcliffe coefficient (NSC) for the simplest model is 0·97, and the root mean squared error (RMSE) is 1·48 °C. For the most sophisticated model the NSC also is 0·97. However, the RMSE is 1·32 °C. For the validation period the NSC for the simplest model is 0·96, and the RMSE is 1·45 °C. The NSC for the most sophisticated model is 0·97, and the RMSE is 1·25 °C. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
603.
Zoltán Makó Ferenc Szenkovits Júlia Salamon Robert Oláh-Gál 《Celestial Mechanics and Dynamical Astronomy》2010,108(4):357-370
This paper provides a study of the stable and unstable regions around the smaller primary in the framework of the spatial
elliptic restricted three-body problem. The definitions and methods used to determine stable and unstable regions are extended
to three dimensions. New results concerning the stable and unstable regions around Mercury are obtained in the Sun–Mercury
system. 相似文献
604.
605.
Rita M. F. Fonseca Fernando J. A. S. Barriga Patrícia I. S. T. Conceição 《International Journal of Earth Sciences》2010,99(8):1899-1916
The Southern region of Portugal is subjected to several forms of over-erosion. Most leached products, mainly composed of fine
particles containing nutrients, metals or pesticides, are easily transported by river flows. When these are hindered by a
physical barrier such as a dam, the particulate load accumulates on the bottom of the reservoirs, often leading to a pronounced
decrease of water quality. Bottom sediments from three reservoirs were subjected to grain-size analysis and a study of clay
minerals by X-ray diffraction. Most sediments contain a diverse set of clay minerals, mostly illites, smectites, chlorites
and kaolinites. The nature of the clay minerals reflects the nature of the parent rocks. During the cycles of transport and
temporary deposition, they may undergo significant chemical and physical transformations, which lead to an increase of expandable
properties and therefore, to a higher cationic exchange capacity, determining its important role as vehicles of environmental
pollutants. 相似文献
606.
Sophie Arnaud-Haond Núria Marbà Elena Diaz-Almela Ester A. Serrão Carlos M. Duarte 《Estuaries and Coasts》2010,33(4):878-889
The diversity–stability relationship is the subject of a long-standing debate in ecology, but the genetic component of diversity
has seldom been explored. In this study, we analyzed the interplay between genetic diversity and demographic responses to
environmental pressures. This analysis included 30 meadows formed by the Mediterranean endemic seagrass, Posidonia oceanica, showing a wide range of population dynamics ranging from a near equilibrium state to steep decline due to strong environmental
pressures close to aquaculture installations. Our results show that sedimentation rates are much better predictors of mortality
than clonal or genetic components. An unexpected positive trend was observed between genotypic diversity and mortality, along
with a negative relationship between allelic richness and net population growth. Yet such trends disappeared when excluding
the most extreme cases of disturbance and mortality, suggesting the occurrence of a threshold below which no relationship
exists. These results contrast with the positive relationship between genotypic diversity and resistance or resilience observed
in previous manipulative experiments on seagrass. We discuss the reasons for this discrepancy, including the difficulties
in designing experiments reflecting the complexity of natural meadows. 相似文献
607.
Júlia Dégi Rainer Abart Kálmán Török Enikő Bali Richard Wirth Dieter Rhede 《Contributions to Mineralogy and Petrology》2010,159(3):293-314
The complex microstructure of kelyphitic rims around garnet in lower crustal garnet granulite xenoliths from the Bakony–Balaton
Highland Volcanic Field, Central Pannonian Basin has been studied in order to identify controls on garnet breakdown. Symplectites
comprised of a vermicular intergrowth of submicron sized anorthite, orthopyroxene and spinel replace garnet at a sharp reaction
front. Based on element distribution maps the transformation of garnet to symplectite is isochemical. Phase diagram calculations
indicate that this reaction was induced by a pressure decrease and/or a temperature increase. In site-specific TEM foils prepared
by focused ion beam technique and oriented parallel and perpendicular to the reaction front 200 nm wide rods of anorthite
and 20 nm wide rods of spinel are identified. The rods are oriented approximately perpendicular to the replacement front and
are embedded in an orthopyroxene matrix. The regular spacing of the symplectite phases along the reaction front suggests that
their growth is controlled by diffusion. The kinetics of symplectite formation has been modelled based on irreversible thermodynamics.
During interaction of the xenolith with the host basalt the microstructure and chemistry of the An–Opx–Spl symplectite was
significantly modified and it was partially replaced by an olivine bearing symplectite. In contrast to primary symplectite
formation, these processes were metasomatic in nature including addition of sodium, titanium and some trace elements from
the basaltic melt and can clearly be discerned from the garnet breakdown. Based on these observations it is inferred that
symplectite formation took place within the deep crust during the extension of the Pannonian Basin between 15 and 30 km depth
at high temperature (850–1,050°C) prior to the volcanic transport to the surface. 相似文献
608.
Antonio Alfonso-Faus Màrius Josep Fullana i Alfonso 《Astrophysics and Space Science》2013,348(2):527-531
From the equivalence principle, one gets the strength of the gravitational effect of a mass M on the metric at position r from it. It is proportional to the dimensionless parameter β 2=2GM/rc 2, which normally is ?1. Here G is the gravitational constant, M the mass of the gravitating body, r the position of the metric from the gravitating body and c the speed of light. The seeable universe is the sphere, with center at the observer, having a size such that it shall contain all light emitted within it. For this to occur one can impose that the gravitational effect on the velocity of light at r is zero for the radial component, and non zero for the tangential one. Light is then trapped. The condition is given by the equality R g =2GM/c 2, where R g represents the radius of the seeable universe. It is the gravitational radius of the mass M. The result has been presented elsewhere as the condition for the universe to be treated as a black hole. According to present observations, for the case of our universe taken as flat (k=0), and the equation of state as p=?ρc 2, we prove here from the Einstein’s cosmological equations that the universe is expanding in an accelerated way as t 2, a constant acceleration as has been observed. This implies that the gravitational radius of the universe (at the event horizon) expands as t 2. Taking c as constant, observing the galaxies deep in space this means deep in time as ct, linear. Then, far away galaxies from the observer that we see today will disappear in time as they get out of the distance ct that is <R g . The accelerated expanding vacuum will drag them out of sight. This may be a valid test for the present ideas in cosmology. Previous calculations are here halved by our results. 相似文献
609.
Frank Beyrich Jens Bange Oscar K. Hartogensis Siegfried Raasch Miranda Braam Dani?lle van Dinther Doreen Gr?f Bram van Kesteren Aline C. van den Kroonenberg Bj?rn Maronga Sabrina Martin Arnold F. Moene 《Boundary-Layer Meteorology》2012,144(1):83-112
Scintillometry has been increasingly used over the last decade for the experimental determination of area-averaged turbulent fluxes at a horizontal scale of a few kilometres. Nevertheless, a number of assumptions in the scintillometer data processing and interpretation still call for a thorough evaluation, in particular over heterogeneous terrain. Moreover, a validation of the path-averaged structure parameters derived from scintillometer data (and forming the basis for the flux calculations) by independent measurements is still missing. To achieve this, the LITFASS-2009 field campaign has been performed around the Meteorological Observatory Lindenberg ?C Richard-A?mann-Observatory of the German Meteorological Service (DWD) in July 2009. The experiment combined tower-based in-situ turbulence measurements, field-scale laser scintillometers, long-range optical (large-aperture) and microwave scintillometers, and airborne turbulence measurements using an automatically operating unmanned aircraft. The paper describes the project design and strategy, and discusses first results. Daytime near-surface values of the temperature structure parameter, ${C_{T}^{2}}$ , over different types of farmland differ by more than one order of magnitude in their dependence on the type and status of the vegetation. Considerable spatial variability in ${C_{T}^{2}}$ was also found along the flight legs at heights between 50 and 100?m. However, it appeared difficult to separate the effects of heterogeneity from the temporal variability of the turbulence fields. Aircraft measurements and scintillometer data agreed in magnitude with respect to the temporal variation of the path-averaged ${C_{T}^{2}}$ values during the diurnal cycle. The decrease of ${C_{T}^{2}}$ with height found from the scintillometer measurements close to the surface and at 43?m under daytime convective conditions corresponds to free-convection scaling, whereas the aircraft measurements at 54 and 83?m suggest a different behaviour. 相似文献
610.
The computation of sunspot areas is important for many applications in solar physics. Some uncertainty is, however, inherent
to this determination, since there is uncertainty in defining the limits of sunspots, as well as their umbrae and penumbrae,
particularly in high-resolution images where large variations in intensity are observed, mainly in the penumbrae and photosphere
regions. In this paper a methodology based on the classical histogram method is presented that enables the generation of fuzzy
sets that correspond to the umbrae and penumbrae of sunspots, as well as to the complete sunspots, which enable the representation
of the uncertainty in their locations. The areas of the sunspots and of their umbrae and penumbrae are then obtained by computing
the areas of the fuzzy sets used to represent them. Two operators are used: the Rosenfeld Area operator, which generates a
real number for the area, and the Fuzzy Area operator, which generates a fuzzy number, providing more information about the
uncertainty of the area. A comparison of the obtained results with the area values given by the classical cumulative histogram
method is made and the differences analyzed. 相似文献