全文获取类型
收费全文 | 362篇 |
免费 | 12篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 26篇 |
地球物理 | 86篇 |
地质学 | 118篇 |
海洋学 | 21篇 |
天文学 | 88篇 |
综合类 | 3篇 |
自然地理 | 18篇 |
出版年
2022年 | 2篇 |
2019年 | 5篇 |
2018年 | 18篇 |
2017年 | 6篇 |
2016年 | 13篇 |
2015年 | 4篇 |
2014年 | 12篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 13篇 |
2010年 | 17篇 |
2009年 | 17篇 |
2008年 | 15篇 |
2007年 | 18篇 |
2006年 | 20篇 |
2005年 | 15篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 12篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1973年 | 3篇 |
1959年 | 2篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1955年 | 2篇 |
1953年 | 1篇 |
1950年 | 3篇 |
1949年 | 3篇 |
1948年 | 1篇 |
1941年 | 1篇 |
排序方式: 共有376条查询结果,搜索用时 609 毫秒
151.
Segmentations of foreland belts and their tectonic mechanism in the Southwest Tarim Basin 总被引:2,自引:0,他引:2
Many geologists focus on the foreland structures, co-relationship between shallow and deep structures and their dynamics between intra-continent orogenies and foreland basin in recent years[1―17]. The intra-plate collision and deformed area of West Kunlun-Pamirand Southern Tianshan become the natural lab of this studies and there are many new developments con-cerned with the geometry and kinemics of foreland thrusting, back-thrusting and triangle zones[3―14]. Many types of foreland thrusti… 相似文献
152.
ZHANG Xingliang Joachim REITNER 《《地质学报》英文版》2006,80(5):636-642
The Ediacaran Dickinsonia is well-known for being the only fossil to be assigned to many phyla, ranging from lichens, Cnidaria, Piatyheiminthes, Annelida, and a phylum of its own to a nonmetazoan kingdom. A new specimen from the Ediacaran fine-grained sandstone on the Winter Coast of the White Sea in northern Russia, which has an age of -555 million years ago, preserved convincing internal anatomies of definite animals, comparable with meridionai canals of extant ctenophores (comb jellies). Additionally, we reconsidered Dickinsonia as a biradiaily symmetrical animal rather than a bilateral one as previously thought. The animal nature of Dickinsonia is, thus, well established and its affinities are most probably allied to ctenophores. This research is not only removing Dickinsonia from Vendobionta, but also bringing the fossil record of ctenophores forward to 20 million years before the Cambrian "explosion". 相似文献
153.
Abstract: The Shibantan Member (Dengying Formation, South China) represents one of only two carbonate settings with Ediacara-type organisms and offers a rare opportunity to study the biogeochemistry of these ecosystems. To evaluate possibilities and limitations for future biomarker studies on fossil-bearing outcrop samples of the Shibantan Member, we analysed the spatial distribution of hydrocarbons in extractable organic matter (i.e. bitumen) on a millimetre scale. Our study demonstrates that the sample and most likely also other rocks from the same setting are contaminated with petroleum-derived compounds that bear the potential for erroneous interpretations in palaeo-reconstructions. The contamination was revealed by distribution patterns and amounts of extractable n-alkanes and acyclic isoprenoids. The contamination is linked to the external weathering surfaces but also to cracks within the rock, and the extent most likely depends on concentration gradients between these contamination sources. Here we show that contamination can successfully be distinguished from syngenetic signals obtained from non-extractable organic matter (i.e. kerogen) using catalytic hydropyrolysis (HyPy). However, we observed that decalcification is necessary to achieve sufficient yields of kerogen-bound hydrocarbons and to avoid artificial alteration of the biomarker signals due to matrix effects. 相似文献
154.
155.
The effects of artificial ammonium enhancement on riverine periphytic diatom communities 总被引:2,自引:0,他引:2
An experiment to ascertain the influence of artificially enhanced ammonium concentrations on riverine periphytic diatom communities was conducted during an 80 day period in winter 1988/89 (temperature: 5°C). During an initial 47 day enrichment phase, ammonium chloride at different concentrations was added to O2-saturated river water in experimental channels. Compared to a control, the addition of 1.2 mg NH
4
+
-N·l–1 resulted in only slight changes in the species composition of the diatom community. The addition of 5.1 mg NH
4
+
-N·l–1 and more (60 µg NH3-N·l–1) resulted in a decrease in the biomass and a drastic change in the species composition. After the 42 day enrichment period, the diatom speciesFragilaria capucina var.vaucheriae, Navicula saprophila, Navicula atomus andGomphonema parvulum, all of which are known to be tolerant to organic pollution, were found with relative abundances of 44.8%, 35.6%, 2.3% and 1.5%, respectively. Changes in species composition of the periphytic diatom communities occurred within the first two weeks of the subsequent recovery phase. After a month of recovery, all periphytic diatom communities exhibited a high degree of structural similarity with the control. 相似文献
156.
Frank Arnold Joachim Curtius Stefan Spreng Terry Deshler 《Journal of Atmospheric Chemistry》1998,30(1):3-10
The first direct in situ measurements of the sulfuric acid contained in stratospheric aerosol particles were made using a novel balloon-based Ion Molecule Reaction Mass Spectrometer instrument (IMRMS) equipped with an aerosol vaporizer. The IMRMS method employed offers direct aerosol sulfuric acid measurements with high spatial resolution. The balloon flight took place on 23 October 1995 in middle latitudes (44°N) and reached a maximum altitude of 24 km. Measured molecular number densities of aerosol sulfuric acid decreased with increasing altitude from about 2.9 × 109 cm-3 at 15km altitude to about 2.4 × 108 cm-3 at 21 km. Corresponding mass mixing ratios are 2.5 and 0.6 ppbm, respectively. Calculated sulfuric acid mixing ratios from aerosol volumes inferred from aerosol size distribution measurements on the same balloon agree well with the IMRMS data using standard assumption aerosol composition. 相似文献
157.
Morphotectonic evidence from lateral propagation of an active frontal fold; Pakuashan anticline, foothills of Taiwan 总被引:1,自引:0,他引:1
B. Delcaillau B. Deffontaines L. Floissac J. Angelier J. Deramond P. Souquet H. T. Chu J. F. Lee 《Geomorphology》1998,24(4):263-290
The Pakuashan anticline is uniquely suited for study of the forward and lateral growth of fault-related folds. The Pakuashan ridge development arises from the late Quaternary uplift of the most external thrust zone of the western foothills of Taiwan. From Kaoshiung to Taichung, recent and active westward thrusting occurs at the front of the foothills. The Pakuashan anticline, trending N 150°E in the northern part to N 000° in the southern part, has been active throughout the Quaternary period. This activity is marked by geological structures, tectonic geomorphology and seismicity. A multisource and multiscale approach to study of the continental collision setting has been undertaken to combine tectonics, sedimentology and geomorphology. Studies of fracture patterns allow identification of two main features of stress orientations: a WNW/ESE compression direction, and E–W and N–S extension directions. Quantitative geomorphic parameters have been used to define the morphotectonic evolution and to infer tectonic style along the mountain front. Geomorphic evidence provides significant information on the processes that govern lateral propagation of an active anticline. Quaternary terraces are uplifted, tilted and folded over the Pakuashan ridge. Drainage systems in areas of active compression give information on the thrust zone structures and their development. Steep drainage and high local relief indicate that the Pakuashan anticline forms a well-defined zone of high uplift, especially in the southern part. The two main controls on drainage in that area are rock strength in the hanging wall and propagation of the deformation towards the south. 相似文献
158.
Sebastiano Ghigna Ben Moore Fabio Governato George Lake Thomas Quinn & Joachim Stadel 《Monthly notices of the Royal Astronomical Society》1998,300(1):146-162
We examine the properties of dark matter haloes within a rich galaxy cluster using a high-resolution simulation that captures the cosmological context of a cold dark matter universe. The mass and force resolution permit the resolution of 150 haloes with circular velocities larger than 80 km s−1 within the cluster virial radius of 2 Mpc (with Hubble constant H 0 = 50 km s−1 Mpc−1 ). This enables an unprecedented study of the statistical properties of a large sample of dark matter haloes evolving in a dense environment. The cumulative fraction of mass attached to these haloes varies from close to zero per cent at 200 kpc to 13 per cent at the virial radius. Even at this resolution the overmerging problem persists; haloes that pass within 100–200 kpc of the cluster centre are tidally disrupted. Additional substructure is lost at earlier epochs within the massive progenitor haloes. The median ratio of apocentric to pericentric radii is 6:1, so that the orbital distribution is close to isotropic, circular orbits are rare and radial orbits are common. The orbits of haloes are unbiased with respect to both position within the cluster and the orbits of the smooth dark matter background, and no velocity bias is detected. The tidal radii of surviving haloes are generally well-fitted using the simple analytic prediction applied to their orbital pericentres. Haloes within clusters have higher concentrations than those in the field. Within the cluster, halo density profiles can be modified by tidal forces and individual encounters with other haloes that cause significant mass loss —'galaxy harassment'. Mergers between haloes do not occur inside the cluster virial radius. 相似文献
159.
Joachim Baumgarte Wolfgang von Grünhagen 《Celestial Mechanics and Dynamical Astronomy》1979,20(2):173-178
This paper shows that for the free symmetric top a formulation of the equations of motion is possible, which is Liapunov stable. The formalism applied is equivalent to the conservative stabilization of the Keplerian problem. The perturbed problem appears in -stable form. This stabilization procedure could be useful in celestial mechanics, if the gyroscopic motion of a satellite is considered and one is interested in the exact position of the angles. 相似文献
160.
Joachim Köhler 《International Journal of Earth Sciences》1941,32(1-2):71-92
Ohne ZusammenfassungAm Schlu\ meiner Arbeit möchte ich meinem hochverehrten Lehrer, Herrn Prof. Dr. F.Angel (Graz), für seine Anregungen und ständige Anteilnahme meinen allerbesten Dank aussprechen. Meinem lieben KameradenSiegfried Däweritz, Mei\en, danke ich herzlich für die Zeichnung von Abbildungen während des Feldzuges in Frankreich. 相似文献