全文获取类型
收费全文 | 4975篇 |
免费 | 197篇 |
国内免费 | 101篇 |
专业分类
测绘学 | 177篇 |
大气科学 | 592篇 |
地球物理 | 1350篇 |
地质学 | 2155篇 |
海洋学 | 197篇 |
天文学 | 594篇 |
综合类 | 82篇 |
自然地理 | 126篇 |
出版年
2022年 | 45篇 |
2021年 | 85篇 |
2020年 | 71篇 |
2019年 | 40篇 |
2018年 | 170篇 |
2017年 | 160篇 |
2016年 | 240篇 |
2015年 | 167篇 |
2014年 | 259篇 |
2013年 | 308篇 |
2012年 | 251篇 |
2011年 | 186篇 |
2010年 | 232篇 |
2009年 | 248篇 |
2008年 | 186篇 |
2007年 | 148篇 |
2006年 | 117篇 |
2005年 | 117篇 |
2004年 | 90篇 |
2003年 | 81篇 |
2002年 | 87篇 |
2001年 | 88篇 |
2000年 | 78篇 |
1999年 | 75篇 |
1998年 | 96篇 |
1997年 | 71篇 |
1996年 | 82篇 |
1995年 | 68篇 |
1994年 | 65篇 |
1993年 | 48篇 |
1992年 | 34篇 |
1991年 | 39篇 |
1990年 | 40篇 |
1989年 | 41篇 |
1988年 | 31篇 |
1987年 | 45篇 |
1986年 | 35篇 |
1985年 | 36篇 |
1984年 | 47篇 |
1983年 | 58篇 |
1982年 | 43篇 |
1981年 | 41篇 |
1980年 | 41篇 |
1979年 | 45篇 |
1978年 | 48篇 |
1977年 | 37篇 |
1976年 | 32篇 |
1975年 | 47篇 |
1974年 | 39篇 |
1973年 | 39篇 |
排序方式: 共有5273条查询结果,搜索用时 15 毫秒
991.
Vizvári Béla Golabi Mahmoud Nedjati Arman Gümüşbuğa Ferhat Izbirak Gokhan 《Natural Hazards》2019,99(1):571-597
Natural Hazards - In this study, a relief system for a large metropolitan city exposed to serious earthquakes is designed and a top-down approach is applied. Afflicted people’s states and... 相似文献
992.
Dr. S. von Bubnoff Sal Rüger C. Gagel Wcks Rudolf Hundt 《International Journal of Earth Sciences》1921,11(5-6):267-274
Ohne Zusammenfassung 相似文献
993.
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
994.
Stefanie Donner Dirk Rößler Frank Krüger Abdolreza Ghods Manfred R. Strecker 《Journal of Seismology》2013,17(3):925-959
The M w 6.2 Baladeh earthquake occurred on 28 May 2004 in the Alborz Mountains, northern Iran. This earthquake was the first strong shock in this intracontinental orogen for which digital regional broadband data are available. The Baladeh event provides a rare opportunity to study fault geometry and ongoing deformation processes using modern seismological methods. A joint inversion for hypocentres and a velocity model plus a surface-wave group dispersion curve analysis were used to obtain an adapted velocity model, customised for mid- and long-period waveform modelling. Based on the new velocity model, regional waveform data of the mainshock and larger aftershocks (M w ?≥3.3) were inverted for moment tensors. For the Baladeh mainshock, this included inversion for kinematic parameters. All analysed earthquakes show dominant thrust mechanisms at depths between 14 and 26 km, with NW–SE striking fault planes. The mainshock ruptured a 28° south-dipping area of 24 × 21 km along a north-easterly direction. The rupture plane of the mainshock does not coincide with the aftershock distribution, neither in map view nor with respect to depth. The considered aftershocks form two main clusters. The eastern cluster is associated with the mainshock. The western cluster does not appear to be connected with the rupture plane of the mainshock but, instead, indicates a second activated fault plane dipping at 85° towards the north. 相似文献
995.
L. Makra J. Mika A. Bartzokas R. Béczi E. Borsos Z. Sümeghy 《Meteorology and Atmospheric Physics》2006,92(1-2):115-137
Summary This paper determines the characteristic air mass types over the Carpathian Basin for the winter (December, January, and February)
and summer (June, July and August) months dependant on levels of the main air pollutants. Based on the ECMWF data set, daily
sea-level pressure fields analysed at 00 UTC were prepared for each air mass type (cluster) in order to relate sea-level pressure
patterns with the level of air pollutants in Szeged. The data comprise daily values of twelve meteorological and eight pollutant
parameters for the period 1997–2001. Objective definition of the characteristic air mass types is achieved by using the methods
of Factor Analysis and Cluster Analysis. According to the results, during the winter months five air mass types (clusters)
were detected based on higher concentrations of primary pollutants that occur with high irradiance and low wind speed. This
is the case when an anticyclone is found over the Carpathian Basin and over the region south of Hungary, influencing the weather
of the country. Low levels of pollutants occur when zonal currents exert influence over Hungary. During the summer months
anticyclones and anticyclone ridge situations are found over the Carpathian Basin. (During the prevalence of anticyclone ridge
situations, the Carpathian Basin is found at the edge of a high pressure centre.) As a result of high irradiance and very
low NO levels, secondary pollutants are highly enriched. 相似文献
996.
Summary The development of a cyclonic vortex over a polynya is investigated with the primitive equation mesoscale model METRAS. The
impact of different atmospheric processes on vortex development is determined by calculating the terms of the vorticity tendency
equation. Sensitivity studies are performed for different large-scale situations (geostrophic winds 1 ms−1, 3 ms−1, 20 ms−1, initial ice-water temperature difference of 35 K or 17.5 K) and for different polynya sizes and shapes. In general, the
vortex develops within a few hours. It is intensified by buoyancy, mainly resulting from latent heat release. Advective and
diffusive processes hinder the vortex development. The intensification depends on the actual situation and is faster over
small polynyas and heterogeneous ice cover. These situations result in intensification periods of only 12 to 18 hours for
the vortex, but create very strong vortices. Halved horizontal temperature gradients also about halve the vortex intensity.
The lifetime and intensification of a vortex increases with the time the air mass spends over the water. Thus, weak winds
show a slower development of the vortex but the vortex intensifies for more than 24 hours. Over big polynyas several vortices
develop, a long polynya results in a longer and narrower vortex which intensifies over a longer period. 相似文献
997.
Erik Rüttener Juan José Egozcue Dieter Mayer-Rosa Stephan Mueller 《Natural Hazards》1996,14(2-3):165-178
Seismic hazard analysis is based on data and models, which both are imprecise and uncertain. Especially the interpretation of historical information into earthquake parameters, e.g. earthquake size and location, yields ambiguous and imprecise data. Models based on probability distributions have been developed in order to quantify and represent these uncertainties. Nevertheless, the majority of the procedures applied in seismic hazard assessment do not take into account these uncertainties, nor do they show the variance of the results. Therefore, a procedure based on Bayesian statistics was developed to estimate return periods for different ground motion intensities (MSK scale).Bayesian techniques provide a mathematical model to estimate the distribution of random variables in presence of uncertainties. The developed method estimates the probability distribution of the number of occurrences in a Poisson process described by the parameter . The input data are the historical occurrences of intensities for a particular site, represented by a discrete probability distribution for each earthquake. The calculation of these historical occurrences requires a careful preparation of all input parameters, i.e. a modelling of their uncertainties. The obtained results show that the variance of the recurrence rate is smaller in regions with higher seismic activity than in less active regions. It can also be demonstrated that long return periods cannot be estimated with confidence, because the time period of observation is too short. This indicates that the long return periods obtained by seismic source methods only reflects the delineated seismic sources and the chosen earthquake size distribution law. 相似文献
998.
A semi-active strategy for model predictive control (MPC), in which magneto-rheological dampers are used as an actuator, is presented for use in reducing the nonlinear seismic response of high-rise buildings. A multi-step predictive model is developed to estimate the seismic performance of high-rise buildings, taking into account of the effects of nonlinearity, time-variability, model mismatching, and disturbances and uncertainty of controlled system parameters by the predicted error feedback in the multi-step predictive model. Based on the predictive model, a Kalman-Bucy observer suitable for semi-active strategy is proposed to estimate the state vector from the acceleration and semi-active control force feedback. The main advantage of the proposed strategy is its inherent stability, simplicity, on-line real-time operation, and the ability to handle nonlinearity, uncertainty, and time-variability properties of structures. Numerical simulation of the nonlinear seismic responses of a controlled 20-story benchmark building is carried out, and the simulation results are compared to those of other control systems. The results show that the developed semi-active strategy can efficiently reduce the nonlinear seismic response of high-rise buildings. 相似文献
999.
1000.
N. V. Chukanov S. M. Aksenov R. K. Rastsvetaeva K. V. Van D. I. Belakovskiy I. V. Pekov V. V. Gurzhiy W. Schüller B. Ternes 《Geology of Ore Deposits》2015,57(8):721-731
A new mineral, mendigite (IMA no. 2014-007), isostructural with bustamite, has been found in the In den Dellen pumice quarry near Mendig, Laacher Lake area, Eifel Mountains, Rhineland-Palatinate (Rheinland-Pfalz), Germany. Associated minerals are sanidine, nosean, rhodonite, tephroite, magnetite, and a pyrochlore-group mineral. Mendigite occurs as clusters of long-prismatic crystals (up to 0.1 × 0.2 × 2.5 mm in size) in cavities within sanidinite. The color is dark brown with a brown streak. Perfect cleavage is parallel to (001). D calc = 3.56 g/cm3. The IR spectrum shows the absence of H2O and OH groups. Mendigite is biaxial (–), α = 1.722 (calc), β = 1.782(5), γ = 1.796(5), 2V meas = 50(10)°. The chemical composition (electron microprobe, mean of 4 point analyses, the Mn2+/Mn3+ ratio determined from structural data and charge-balance constraints) is as follows (wt %): 0.36 MgO, 10.78 CaO, 37.47 MnO, 2.91 Mn2O3, 4.42 Fe2O3, 1.08 Al2O3, 43.80 SiO2, total 100.82. The empirical formula is Mn2.00(Mn1.33Ca0.67) (Mn0.50 2+ Mn0.28 3+ Fe0.15 3+ Mg0.07)(Ca0.80 (Mn0.20 2+)(Si5.57 Fe0.27 3+ Al0.16O18). The idealized formula is Mn2Mn2MnCa(Si3O9)2. The crystal structure has been refined for a single crystal. Mendigite is triclinic, space group \(P\bar 1\); the unit-cell parameters are a = 7.0993(4), b = 7.6370(5), c = 7.7037(4) Å, α = 79.58(1)°, β = 62.62(1)°, γ = 76.47(1)°; V = 359.29(4) Å3, Z = 1. The strongest reflections on the X-ray powder diffraction pattern [d, Å (I, %) (hkl)] are: 3.72 (32) (020), 3.40 (20) (002, 021), 3.199 (25) (012), 3.000 (26), (\(01\bar 2\), \(1\bar 20\)), 2.885 (100) (221, \(2\bar 11\), \(1\bar 21\)), 2.691 (21) (222, \(2\bar 10\)), 2.397 (21) (\(02\bar 2\), \(21\bar 1\), 203, 031), 1.774 (37) (412, \(3\bar 21\)). The type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4420/1. 相似文献