全文获取类型
收费全文 | 6816篇 |
免费 | 207篇 |
国内免费 | 81篇 |
专业分类
测绘学 | 231篇 |
大气科学 | 629篇 |
地球物理 | 1526篇 |
地质学 | 2523篇 |
海洋学 | 585篇 |
天文学 | 1161篇 |
综合类 | 24篇 |
自然地理 | 425篇 |
出版年
2022年 | 51篇 |
2021年 | 95篇 |
2020年 | 118篇 |
2019年 | 91篇 |
2018年 | 202篇 |
2017年 | 184篇 |
2016年 | 244篇 |
2015年 | 160篇 |
2014年 | 221篇 |
2013年 | 334篇 |
2012年 | 266篇 |
2011年 | 405篇 |
2010年 | 299篇 |
2009年 | 387篇 |
2008年 | 339篇 |
2007年 | 271篇 |
2006年 | 279篇 |
2005年 | 280篇 |
2004年 | 350篇 |
2003年 | 274篇 |
2002年 | 205篇 |
2001年 | 148篇 |
2000年 | 158篇 |
1999年 | 138篇 |
1998年 | 133篇 |
1997年 | 107篇 |
1996年 | 75篇 |
1995年 | 77篇 |
1994年 | 73篇 |
1993年 | 65篇 |
1992年 | 61篇 |
1991年 | 47篇 |
1990年 | 58篇 |
1989年 | 30篇 |
1988年 | 30篇 |
1987年 | 55篇 |
1986年 | 37篇 |
1985年 | 41篇 |
1984年 | 58篇 |
1983年 | 45篇 |
1982年 | 49篇 |
1981年 | 43篇 |
1980年 | 41篇 |
1979年 | 28篇 |
1978年 | 44篇 |
1977年 | 41篇 |
1976年 | 38篇 |
1975年 | 44篇 |
1974年 | 36篇 |
1973年 | 35篇 |
排序方式: 共有7104条查询结果,搜索用时 140 毫秒
181.
An inventory is presented of researches concerning the use of remote sensing for landslide studies and hazard zonation as mainly carried out in the countries belonging to the European Community. An overview is given of the applicability of remote sensing in the following phases of landslide studies:
- 1. (1) Detection and classification of landslides. Special emphasis is given to the types of imagery required at different scales of analysis.
- 2. (2) Monitoring the activity of existing landslides using G.P.S., photogrammetrical techniques and radar interferometry.
- 3. (3) Analysis and prediction in space and time of slope failures. The different factors required in a landslide hazard study are evaluated, and the optimum remote sensing imagery for obtaining each of these factors is indicated.
182.
Frédérick Delay Hélène Housset-Resche Gilles Porel Ghislain de Marsily 《Mathematical Geology》1996,28(1):45-71
A new method for solving the transport equation based on the management of a large numbe of particles in a discretized 2-D domain is presented. The method uses numerical variables to represent the number of particles in a given mesh and is more complex than the 1-D problem. The first part of the paper focuses on the specific management of particles in a 2-D problem. The method also would be valid for three dimensions as long as the medium can be modeled similar to a layered system. As the particles are no longer tracked individually, the algorithm is fast and does not depend on the number of particles present. The numerical tests show that the method is nearly numerical dispersion free and permits accurate calculations even for simulations of low-concentration transport. Because each mesh is considered as a closed system between two successive time steps, it is easy to add adsorption phenomenon without any problem of numerical stability. The model is tested under conditions that are extremely demanding for its operating mode and gives a good fit to analytical solutions. The conditions in which it can be used to best advantage are discussed. 相似文献
183.
184.
Sabine Gaudzinski Felix Bittmann Wolfgang Boenigk Manfred Frechen Thijs Van Kolfschoten 《Quaternary Research》1996,46(3):319-334
The Kärlich–Seeufer archaeological site in Germany's central Rhineland was excavated between 1980 and 1992. The site provides evidence for hominid activity during a Middle Pleistocene interglaciation known up to now only from the Kärlich clay pit and therefore defined as the Kärlich Interglaciation, which is considered to be post-Cromer IV and pre-Holstein (sensu stricto) in age. The site is characterized by Acheulean artifacts, a fauna dominated byElephas (Palaeoloxodon) antiquus,and a unique and outstanding preservation of wooden and other palaeobotanical remains. Assuming all finds are associated, the site previously was interpreted as an elephant hunting camp with a wooden structure, together with wood and bone implements preservedin situ.Recent analysis of the same features has shown that the site can also be interpreted as a reworked archaeological sample. Hominid occupation occurred in the vicinity of a small lake with prevailing meso-oligotrophic conditions. Expanding boreal forests and fen vegetation characterized the landscape. 相似文献
185.
186.
During the last decade, exploration and mining of modern-Tertiary heavy mineral beach and raised beach sands along the west
coast of South Africa has developed into a major industry. High resolution radiometric techniques have demonstrated their
use as a quantitative indicator of total heavy mineral concentration (THM) and also have the ability to discriminate between
sediments derived from different provenance terrains. Results indicate that it is possible to calculate the total heavy mineral
concentration from high resolution radiometric measurements, but the ability to quantify the concentration of individual mineral
fractions, such as ilmenite, requires further refinement of the method. Radiometric characteristics of the light mineral fraction
made it possible to distinguish between sediments from mixed marine-aeolian palaeoplacers and active present beach placers.
The effects of in situ alteration of the ilmenite fraction in the palaeoplacers were also reflected by subtle contrasts in
the radiometric character of the deposits. Furthermore, the uniform radiometric character of the sample population indicates
a common provenance for the heavy mineral suite and supports previous results which indicate the metamorphites of the mid-Proterozoic
Namaqua Province as the primary source terrain. The high resolution radiometric techniques discussed offer a broad spectrum
of applications in sedimentology and have the potential to aid heavy mineral exploration. With further refinement it can possibly
be used quantitatively in grade control during mining and beneficiation of heavy mineral deposits.
Received: 19 July 1996 / Accepted: 7 January 1997 相似文献
187.
Geologie en Mijnbouw - 相似文献
188.
Geochemical exploration for platinum-group elements in the Bushveld Complex, South Africa 总被引:2,自引:0,他引:2
H. J. Wilhelm H. Zhang F. L. Chen J. H. Elsenbroek M. Lombard D. de Bruin 《Mineralium Deposita》1997,32(4):349-361
Analyses of stream sediment and soil samples from the Bushveld Complex, South Africa have revealed enhanced precious metal
concentrations, which can be related both to mining activities and the presence of hidden concentrations of platinum-group
elements (PGEs) and gold. The economically important PGE deposits hosted by the Upper Critical Zone of the Rustenburg Layered
Suite are revealed by a high PGE and Au content in the overlying soils. A second zone of elevated precious metal concentrations
straddles the boundary between the Main and Upper Zones and has to date been traced for more than 100 km. This zone follows
the igneous layering of the Rustenburg Layered Suite and is offset by the Brits Graben. It is therefore thought to be the
reflection of a magmatic PGE-Au mineralisation.
Received: 31 May 1996 / Accepted: 7 January 1997 相似文献
189.
190.
S. Klimov S. Romanov E. Amata J. Blecki J. Büchner J. Juchniewicz J. Rustenbach P. Triska L. J. C. Woolliscroft S. Savin Yu. Afanas’yev U. de Angelis U. Auster G. Bellucci A. Best F. Farnik V. Formisano P. Gough R. Grard V. Grushin G. Haerendel V. Ivchenko V. Korepanov H. Lehmann B. Nikutowski M. Nozdrachev S. Orsini M. Parrot A. Petrukovich J. L. Rauch K. Sauer A. Skalsky J. Slominski J. G. Trotignon J. Vojta R. Wronowski 《Annales Geophysicae》1997,15(5):514-527
The plasma-wave experiment ASPI (analysis of spectra of plasma waves and instabilities) on board the INTERBALL spacecraft is a combined wave diagnostics experiment. It performs measurements of the DC and AC magnetic field vector by flux-gate and searchcoil sensors, the DC and AC electric field vector by Langmuir double probes and the plasma current by Langmuir split probe. Preliminary data analysis shows the low noise levels of the sensors and the compatibility of new data with the results of previous missions. During several months of in-orbit operation a rich collection of data was acquired, examples of which at the magnetopause and plasma sheet are presented in second part of the paper. 相似文献