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791.
Dr. Vincent J. Schaefer 《Pure and Applied Geophysics》1956,34(1):211-220
Summary An exploration of the electrical properties of the atmosphere on and above the island of Hawaii, as indicated by a portable corona current unit, is described. A 30 foot telescopic mast having a radioactive probe mounted on an insulated bushing and connected by shielded cable to a sensitive microammeter was used. Corona currents were measured at a number of geographic locations ranging from sea level under conditions of heavy surf to the 10,000 foot level on Mauna Kea several thousand feet above the exchange layer, and over the land and ocean in a light plane. Observations were made under clear, cloudy and rainy conditions. Fair weather and cloudy conditions gave currents from air to earth of positive sign. With warm rain falling the currents had a negative sign and increased in value with intensity of precipitation. In several instances indications of incipient discharges similar to that observed in mild lightningstorms were noted.The island of Hawaii has many desirable features to recommend it for an extensive research program in atmospheric electricity. A simple and inexpensive approach to inaugurating such a program is suggested. 相似文献
792.
793.
Dr. I. Valeton 《Contributions to Mineralogy and Petrology》1956,5(1):100-104
Zusammenfassung Es wird über Turmalin- und Zirkon-Veränderungen durch Auflösung und Neukristallisation berichtet. Unter Anführung von Beobachtungen anderer Autoren wird von der Verfasserin angenommen, daß es sich um sedimentäre Neubildungen handelt. 相似文献
794.
795.
Dr Otto Braitsch 《Contributions to Mineralogy and Petrology》1956,5(3):210-226
Zusammenfassung Bei einfachen Gefügediagrammen mit nur 1 Maximum wird eine elementar ausführbare rechnerische Bestimmung des Schwerpunktvektors mit Hilfe von Auszählnetzen durchgeführt. Seine wahrscheinlichkeitstheoretische Zuverlässigkeit kann aus Nomogrammen; die nach der Theorie vonR. A. Fisher berechnet wurden, abgelesen werden. Die Größe des Schwerpunktvektors, umgerechnet auf Prozent der idealen. Parallelorientierung, ist ein unmittelbares Maß der Regelungsschärfe und daher auch von praktischem Interesse. Anwendungsmöglichkeiten und Grenzen der rechnerischen Auswertung werden aufgezeigt. Ein Beispiel erläutert die Besonderheiten des Verfahrens. 相似文献
796.
Prof. Dr. T. N. Krishnamurti H. S. Bedi Wei Han 《Meteorology and Atmospheric Physics》1998,67(1-4):117-134
Summary In this paper we address the issue of monsoon forecasts in relation to the organization of convection. Given a physical initialization procedure, within a data assimilation, it is possible to use the detailed distribution of rainfall from mesoconvective precipitating elements to define the initial state of a global model. If that is carried out using a very high resolution model then the initial state can carry within it an organization of convection within the resolvable scales. Then the impact of physical initialization on the maintenance and prediction of tropical weather such as the monsoon can be determined. Lacking such an initialization, one can expect the convectively driven energetics to be biased, and a slow degradation of the forecasts can follow. Several examples of forecasts at different resolutions are discussed here. The main findings of this study are that improved forecast results are obtained when physical initialization is invoked where the observed rain and the model resolution are comparable, i.e. the footprint of the highest resolutions rainfall estimates obtained from satellite based data sets (principally we use the SSM/I instrument over the oceans). At this resolution, we note that the model is able to carry an organization of convection in the initialization and in the forecasts through the medium-range time scale.We have compared our results of monsoon studies at a resolution T255 with those at resolution T62. The transform grid separation at the resolution T255 is approximately 50 km and at the resolution T62, it is approximately 200 km. We find that the model at the higher resolution (T255) performs better and has more realistic energy conversions for the convectively driven synoptic scale monsoon.An organization of convection, at the synoptic scales, is not seen in the forecasts at lower resolutions, T62, where the rainfall patterns are generally much broader and tend to be more zonal. Such organization appears more realistic at the resolution T255. Variances of the energy conversion, calculated in the two-dimensional spectral space, from physically initialized short range forecasts at the higher resolution are seen to be largest on the scales of the monsoon. Similar calculations for the reanalyzed fields at lower resolutions show the spectral distribution of variances to be biased towards local Hadley scale overturnings.With 12 Figures 相似文献
797.
Summary Variability of the summer climate of Madagascar is studied using area-averaged rainfall (1961–1992) and ECMWF meteorological data (1987–1992). Rainfall time series illustrate a seasonal onset in late December, a convective peak in mid-February and cessation near the end of March. Convective cycles with periods of 10–20 and 40 days are common. The former are contributed by easterly waves and the latter by monsoon surges which may resonate with the Madden Julian Oscillation. Using ECMWF January–February means, the summer climate of the Madagascar region is described. Characteristics of the region include SST>28°C, a quasi-permanent, topographic trade wind trough, sudden cyclogenesis, and distinct circulation regimes with easterly (westerly) shear to the north (south). The most poleward limit of deep convection and sustained uplift is near 20°S, 45°E. A convective vortex embedded in the ITCZ is a prevalent feature owing to the interaction of the NW monsoon and local topography.With 11 Figures 相似文献
798.
Summary In this paper a retrieval technique for estimating rainfall rates is introduced. The novel feature of this technique is the combination of two satellite radiometers — the Special Sensor Microwave/Imager (SSM/I) and the Advanced Very High-Resolution Radiometer (AVHRR) — with mesoscale weather prediction model data. This offers an adjustment of the model atmospheres to reality which is necessary for calculating brightness temperatures that can be compared with microwave satellite measurements.In sensitivity studies it was found that the estimation of precipitation is determined to a high degree by the particle size distribution of rain and snow, especially by the size distribution of solid hydrometeors. These studies also reveal the influence of the knowledge of the correct cloud coverage inside a SSM/I pixel and the importance of using a realistic temperature profile instead of using standard atmospheres.The retrieval technique is based on radiative transfer calculations using the model of Kummerow et al. (1989). The algorithm consists of two parts: First Guess (FG) brightness temperatures for the SSM/I frequencies are generated as a function of the cloud top height and the cloud coverage, derived from AVHRR data and predictions from a meso-scale model. The rainfall rate of different types of clouds containing raindrops, ice particles and coexisting ice and water hydrometeors is then calculated as a function of the cloud top height. As an example, a strong convective rain event over the western part of Europe and over the Alps is taken to evaluate the performance of this technique. Good agreement with radar data from the German Weather Service was achieved. Compared to statistical rainfall algorithms, the current algorithm shows a better performance of detecting rainfall areas.With 12 Figures 相似文献
799.
800.