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991.
Lj. Cvetković V. A. Boronikhin M. K. Pavićević D. Krajnović I. Gržetić E. Libowitzky G. Giester E. Tillmanns 《Mineralogy and Petrology》1995,53(1-3):125-131
Summary A hitherto unknown TI-sulfosalt, containing antimony and arsenic, was discovered by ore microscopy (including quantitative reflectance measurements) and electron microprobe analysis in samples from the Allchar TI-Sb-As sulfide ore deposit (Macedonia). The chemical formula is TI5Sb9(As,Sb)4S22, X-ray single crystal and powder diffration data gave the lattice parameters
o = 7.393(4) Å, b0 = 8.707(2) Å, co = 17.584(3) Å, = 103.81(1)°, = 91.79(1)°, = 109.50(1)°; space group
, Z = 1. The new mineral and the new mineral naine jankoviéite have been approved by the IMA/CNMMN.
Jankoviit, Tl5Sb9(As,Sb)4S22, ein neues TI-Sulfosalz aus Allehar, Macedonien
Zusammenfassung Ein bislang unbekanntes Thallium-Antimon-Arsen-Sulfosalz wurde mittels Erzmikroskopie (inklusive quantitativer Reflexionsmessungen) und Elektronenstrahl-Mikrosonde in Proben aus der TI-Sb-As-Sulfid-Lagerstätte Allchar in Macedonien entdeckt. Die chemische Formel lautet Tl5Sb9(As,Sb)4S22, aus Röntgen-Einkristallaufnahmen und Pulverdiffraktogrammen konnten folgende Gitterkonstanten bestimmt werden: ao = 7.393(4) Å, bo = 8.707(2) _Å, co = 17.584(3) Å, a = 103.81(1)°, = 91.79(1)°, = 109.50(1)°; Raumgruppe , Z = 1. Das neue Mineral, sowie der neue Mineralname Jankoviit wurden durch die IMA/CNMMN anerkannt.相似文献
992.
Vít Voženílek 《GeoJournal》1994,32(3):241-245
The territory of the Czech Republic has been investigated by geographers for many decades. The Moravian Gate situated in the eastern part of the Czech Republic, became a place of high human concentration due to its geographical location. Geomorphological research in the Czech republic has reached an impressive level in the field of both the morphostructure of the whole territory and the extent of glaciation. The article treats the relationship between the morphostructure and the extent of glaciation in a geographically complicated region. Both of these have been investigated separately. The synthesis of all results brings new knowledge and suggestions for future research in the region close to the main European watershed. The paper is completed on the basis of the author's research including the complex geomorphological analysis, especially morphostructural and morfosculptural analysis, the investigation of the features and genesis of georelief, the digital elevation model of studied area, the detailed geomorphological mapping in 1:10.000 scale and the compilation of denudation chronology. 相似文献
993.
994.
Different types of oscillatory motions were detected in the late phases of eruption of a prominence. We found oscillations of the prominence axis and diameter with periods of 4.3 and 9.1 min, corresponding to the eigenmodes m = 4 and m = 8 with a damping factor 4.6 × 10–3 s–1. A period about 4.5 min was found for oscillations of the pitch angle of the helically twisted filaments. The m = 2 and m = 3 eigenmodes could be also identified and they led to the final relaxation of the prominence axis. The observations are compared with a model in which we consider forces acting in a curved, cylindrical magnetic tube anchored at both ends in the photosphere and carrying an electric current. The stability of the prominence is discussed. 相似文献
995.
SONG Ci'an LEI Liangqi YANG Qijun 《中国地球化学学报》2007,26(3):329-332
In the Lingchuan-Daoping and Xinglu Pb-Zn ore fields in northern and eastern Guangxi Autonomous Region, Pb, Cu botanogeochemical anomalies may be ascribed to the excessive amounts of Pb and Cu taken up by the root system of plants, such as China fir (Cunninghamia lanceolata Lamb. Hook), mason pine (Pinus massoniana Lamb.) and bracken fern (Pteridium aquilinum var. latiusculum). Under transmission electron microscope (TEM), the excess Pb, Cu in the leaf cells of the plants are present as high electron-density substances, which were precipitated in the leaf cells, causing phytotoxic effects by deforming and injuring cellular tissues. The sorts of toxic elements accumulating in the leaf cells are consistent with those of the botanogeochemically anomalous elements in the polluted soil where the plants grow. In addition, the plants may also be capable of resisting the invasion of excess Cu (and Pb) . 相似文献
996.
Weak Zone Related Seismic Cycles in Progressive Failure Leading to Collapse in Brittle Crust 总被引:2,自引:0,他引:2
Until quite recently our understanding of the basic mechanical process responsible for earthquakes and faulting was not well known. It can be argued that this was partly a consequence of the complex nature of fracture in crust and in part because evidence of brittle phenomena in the natural laboratory of the earth is often obliterated or obscured by other geological processes. While it is well understood that the spatial and temporal complexity of earthquakes and the fault structures emerge from geometrical and material built-in heterogeneities, one important open question is how the shearing becomes localized into a band of intense fractures. Here we address these questions through a numerical approach of a tectonic plate by considering rockmass heterogeneity both in microscopic scale and in mesoscopic scale. Numerical simulations of the progressive failure leading to collapse under long-range slow driving forces in the far-field show earthquake-like rupture behavior. En Echelon crack-arrays are reproduced in the numerical simulation. It is demonstrated that the underlying fracturing induced acoustic emissions (or seismic events) display self-organized criticality—from disorder to order. The seismic cycles and the geometric structures of the fracture faces, which are found greatly depending on the material heterogeneity (especially on the macroscopic scale), agree with that observed experimentally in real brittle materials. It is concluded that in order to predict a main shock, one must have extremely detailed knowledge on very minor features of the earth's crust far from the place where the earthquake originated. If correct, the model proposed here seemingly provides an explanation as to why earthquakes to date are not predicted so successfully. The reason is not that we do not understand earthquake mechanisms very well but that we still know little about our earth's crust. 相似文献
997.
内蒙古海拉尔盆地大磨拐河组孢粉组合 总被引:13,自引:1,他引:13
海拉尔盆地大磨拐河组自下而上可以划分出两个孢粉组合 :哈氏三角孢 -微细云杉粉 ( Deltoidospora hallii-Piceaepollenites exilioides)组合和澳洲无突肋纹孢 -卵形光面单缝孢 ( Cicatricosisporites australiensis- L aevigato-sporites ovatus)组合 ,分别分布于大磨拐河组一段和二段 ,组合特征明显 ,可以作为研究区内地层划分对比的生物地层学依据之一。两个孢粉组合中见有属种繁多的海金沙科孢子及其他繁盛于早白垩世的孢子花粉 ,结合在数以千计的岩心样品中没有发现可靠的早期被子植物花粉的情况分析 ,推测产这两个孢粉组合的大磨拐河组的地质时代为早白垩世凡兰吟期—欧特里沃期 ( Valanginian— Hauterivian) ,不排除部分进入巴列姆期 ( Barrem ian)的可能 相似文献
998.
利用锆石形态、成分组成及年龄分析进行沉积物源区示踪的综合研究 总被引:26,自引:4,他引:26
通过盆地碎屑沉积物分析示踪源区,进而探讨区域构造演化已成为当前地学研究的热点。盆地沉积物中的锆石不但分布广泛,而且稳定性极强,因而能保存大量的源区信息。随着锆石裂变径迹及U-Pb年龄谱分析等新测试技术的发展,锆石的形态、成分组成及年龄分析已成为盆地沉积物源区示踪的重要探针。本文结合实例,介绍了目前在综合利用锆石的形态、成分组成及年代学特征进行物源示踪的一些主要进展。由于物源示踪的复杂性,在利用锆石进行物源示踪时,应充分了解区域地质背景,密切结合其它物源示踪方法。 相似文献
999.
M. Široká C. Fischer V. Cassé R. Brožková J.-F. Geleyn 《Meteorology and Atmospheric Physics》2003,82(1-4):227-244
Summary ?The paper deals with an alternative formulation of the so-called NMC (National Meteorological Center, now National Centers
for Environmental Prediction) statistics to compute the background error covariance matrix to be used in a mesoscale variational
analysis. While the standard method uses differences of forecasts valid for the same time, but starting from different analysis
times, the new formulation required the recomputation of the short-term forecast with the initial and lateral boundary data
that come from the long-term run. In the frame of a limited-area model, this approach forces the error variances at large
scales to decrease drastically, because those scales are controlled by the (constant data) lateral boundary coupling. As a
result, the background cost function acts more scale selectively, with an emphasis on medium scales. The analysis increments
obtained from the 3D-VAR system show that the analysis increments are sharper and more concentrated with the new formulation,
both in single observation and in full observation experiments. This work is part of a wider project for building a variational
assimilation system inside the ALADIN model. The complete system should concentrate on mesoscale features and it should not
reanalyse those scales that were already treated by the global model (ARPEGE). Some difficulties and perspectives are drawn
in the concluding discussion.
Received February 12, 2001; revised July 24, 2001 相似文献
1000.