全文获取类型
收费全文 | 101篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 7篇 |
地球物理 | 36篇 |
地质学 | 31篇 |
海洋学 | 3篇 |
天文学 | 17篇 |
综合类 | 1篇 |
自然地理 | 3篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 5篇 |
2014年 | 1篇 |
2013年 | 6篇 |
2012年 | 3篇 |
2011年 | 2篇 |
2010年 | 7篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 7篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有104条查询结果,搜索用时 671 毫秒
1.
A new model of albedo and emissivity of planetary surfaces covered by volatile ices in the form of porous slab-like deposits is described. In the model, a radiative transfer model is coupled with a microphysical model in order to link changes in albedo and emissivity to changes in porosity caused by ice metamorphism. Preliminary results for Triton, Pluto, and Io are presented (the martian CO2 caps will be the subject of a separate publication). The coupled model will aid in the interpretation of ground-based and spacecraft observations and should lead to advances in surface and atmospheric modeling. 相似文献
2.
Abstract. Two sediment cores were collected in the southern Baltic Sea and sliced into 1.0cm-thick layers. Sediments of each layer were analysed for activities of 210Pb, 137Cs, 134Cs and for the density of meiobenthic organisms (meiofauna). Zones with the rapid mixing occur in the uppermost layers (0–3 cm) of the cores based on I34Cs profiles. The extent and density of meiofauna confirmed the rapid mixing and revealed layers with slow mixing (4–8 cm). Sedimentation rates were derived from 210Pb profiles below the mixing zones (1.21 and 1.72 mm a-I) and were confumed by 137Cs distribution. Of twenty-one major meiofauna taxa commonly found in the Baltic sediments, three were present in the cores. 相似文献
3.
This paper introduces a new method for GPS signal acquisition, which is based on the repeatability of successive code phase
measurements and the M-of-N search algorithm. The performance of the proposed method in terms of probability of signal detection
is similar to that of traditional methods, except that the calculation of the probability of detection does not rely on the
noise distribution or the Carrier-to-Noise ratio (C/N0). The code phase repeatability-based method is presented along with equations for probability of detection and probability
of false detection. If the distribution of the noise is known, it also provides an estimate of the C/N0. The proposed method is illustrated for coherent and non-coherent acquisition and C/N0 estimation. 相似文献
4.
To study geochemical processes for migration and fixation of fissiogenic rare earth elements (REE) in association with uranium dissolution, in situ isotopic analyses using an ion microprobe were performed on U- and REE-bearing secondary minerals, such as coffinite, françoisite, uraniferous goethite, and uraninite found in a sandstone layer 30 to 110 cm beneath a natural fission reactor at Bangombé, Gabon. Phosphate minerals such as phosphatian coffinite and françoisite with depleted 235U (235U/238U = 0.00609 to 0.00638) contained large amount of fissiogenic light REE, while micro-sized uraninite grains in a solid bitumen aggregate have normal U isotopic values (235U/238U = 0.00725) and small amount of fissiogenic REE components. The proportions of fissiogenic and non-fissiogenic REE components in four samples from the core of BAX03 vary in depth ranging from 30 cm to 130 cm beneath the reactor, which suggests mixing between fissiogenic isotopes from the reactor and non-fissiogenic isotopes from original minerals in the sandstone. Significant chemical fractionation was observed between Ce and the other REE in the secondary minerals, which shows evidence of an oxidizing atmosphere during their formation. Pb-isotopic analyses of individual minerals do not directly provide chronological information because of the disturbance of U-Pb decay system due to recent geologic alteration. However, systematic Pb-isotopic results from all of the minerals reveal the mobilization of fissiogenic isotopes, Pb and U from the reactor in association with dolerite dyke intrusion ∼0.798 Ga ago and the formation of the secondary minerals by mixing event between 2.05 Ga-old original minerals and reactor materials due to recent alteration. 相似文献
5.
Natural Hazards - On 17 April 2015, the Wujek/?l?sk underground coal mine in Poland was struck by a strong induced tremor of magnitude M4.0. The event was followed by a massive rock burst... 相似文献
6.
Wiesław Wiśniewolski Janusz Górczyński Wiesław Madry 《Aquatic Sciences - Research Across Boundaries》1989,51(3):249-259
Width of the first ray of the pectoral fin has been measured in two places for 154 young and 89 adult wels. Statistical relationships between the above characters and fish length as well as its maturity and sex have been proved. Three models of discriminant function for identification of adult fish sex have been derived and verified. The accuracy of sex separation has been 89,5% in a standard sample of wels, and 90,6% in a routine sample, after an adjustment in the procedure. 相似文献
7.
8.
Janusz Krzyścin 《Pure and Applied Geophysics》1990,132(3):481-493
In this paper we solve analytically wave kinematic equations and the wave energy transport equation, for basic long surface gravity wave in the coastal upwelling zone. UsingGent andTaylor's (1978) parameterization of drag coefficient (which includes interaction between long surface waves and the air flow) we find variability of this coefficient due to wave amplification and refraction caused by specific surface water current in the region. The drag coefficient grows towards the shore. The growth is faster for stronger current. When the angle between waves and the current is less than 90° the growth is mainly connected with the waves steepness, but when the angle is larger, it is caused by relative growth of the wave phase velocity. 相似文献
9.
Is Newton's iteration faster than simple iteration for transformation between geocentric and geodetic coordinates? 总被引:2,自引:0,他引:2
Piotr Laskowski 《Journal of Geodesy》1991,65(1):14-17
Summary Two iterative algorithms for transformation from geocentric to geodetic coordinates are compared for numerical efficiency: the well known Bowring's algorithm of 1976, which employs the method of simple iteration, and the recent (1989) algorithm by Borkowski, which employs the Newton-Raphson method. The results of numerical tests suggest that the simple iteration method implemented in Bowring's algorithm executes approximately 30% faster than the Newton-Raphson method implemented in Borkowski's algorithm. Only two iterations of each algorithm are considered. Two iterations are sufficient to produce coordinates accurate to the comparable level of 1E-9 m, which exceeds the requirements of any practical application. Therefore, in the class of iterative methods, the classical Bowring's algorithm should be the method of choice. 相似文献
10.
Glauconite pellets from the Lower Silurian Brassfield Formation on both limbs of the Cincinnati Arch in Ohio and Indiana give a RbSr age of 370 ± 11 Ma, which is substantially younger than the stratigraphic age of the formation. The age is concordantcwith conventional KAr ages of 355 ± 6 and 368 ± 5 Ma for two of the same glauconites. Concordant ages were also obtained from the Viburnum Trend in Missouri, where glauconite pellets from the Davis Formation in an ore-zone collapse structure into the underlying Bonneterre Formation give a RbSr age of 387 ± 21 Ma and conventional KAr ages of 368 ± 5 and 369 ± 5 and 369 ± 5 Ma. A third suite of glauconite from the Bonneterre Formation in the Old Lead Belt ~ 10 km from the nearest ore body has given a RbSr age of 423 ± 7 Ma and slightly older conventional KAr ages of 434 ± 6, 445 ± 6 and 441 ± 11 Ma.Because these glauconite-bearing rocks have been buried to depths of less than 1 km, thermal resetting of the RbSr and KAr systematics appears unlikely. The initial ratios of the RbSr isochrons are similar to the ratios for vein- and vug-filling dolomite and calcite. This is consistent with resetting of the RbSr and KAr systems during diagenetic changes which included the isotopic equilibration (perhaps by cation exchange) of the Sr in the glauconite with that in the diagenetic and Mississippi Valley-type ore fluids. This interpretation implies that the age of the Mississippi Valley-type mineralization in the Viburnum Trend is Devonian rather than Carboniferous—Permian as has been inferred from paleomagnetic measurements.Cation-exchange experiments with a dilute Sr-bearing solution and an artificial oilfield brine indicate that glauconite adsorbs large amounts of Sr, some of which is sufficiently strongly attached to the glauconite lattice as to resist leaching with ammonium acetate. The introduction of this strongly attached Sr may be the first step in the resetting of the RbSr systematics of glauconite by cation exchange. 相似文献