全文获取类型
收费全文 | 993篇 |
免费 | 50篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 97篇 |
地球物理 | 239篇 |
地质学 | 452篇 |
海洋学 | 62篇 |
天文学 | 126篇 |
综合类 | 4篇 |
自然地理 | 52篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 16篇 |
2020年 | 20篇 |
2019年 | 18篇 |
2018年 | 25篇 |
2017年 | 35篇 |
2016年 | 25篇 |
2015年 | 40篇 |
2014年 | 41篇 |
2013年 | 61篇 |
2012年 | 52篇 |
2011年 | 60篇 |
2010年 | 70篇 |
2009年 | 57篇 |
2008年 | 54篇 |
2007年 | 47篇 |
2006年 | 46篇 |
2005年 | 53篇 |
2004年 | 44篇 |
2003年 | 32篇 |
2002年 | 35篇 |
2001年 | 28篇 |
2000年 | 15篇 |
1999年 | 12篇 |
1998年 | 16篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 16篇 |
1994年 | 3篇 |
1993年 | 14篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 11篇 |
1989年 | 6篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有1049条查询结果,搜索用时 15 毫秒
991.
Philippe Robutel 《Celestial Mechanics and Dynamical Astronomy》1995,62(3):193-217
We present a direct method for the expansion of the planetary Hamiltonian in Poincaré canonical elliptic variables with its effective implementation in computer algebra. This method allows us to demonstrate the existence of simplifications occurring in the analytical expression of the Hamiltonian coefficients. All the coefficients depending on the ratio of the semi major axis can thus be expressed in a concise and canonical form. 相似文献
992.
The human perturbation of the carbon cycle via the release of fossil CO2 and land use change is now well documented and agreed to be the principal cause of climate change. We address three fundamental research areas that require major development if we were to provide policy relevant knowledge for managing the carbon-climate system over the next few decades. The three research areas are: (i) carbon observations and multiple constraint data assimilation; (ii) vulnerability of the carbon-climate system; and (iii) carbon sequestration and sustainable development. 相似文献
993.
Hennebelle Patrick Belloche Arnaud Whitworth Anthony André Philippe 《Astrophysics and Space Science》2004,292(1-4):355-360
We present numerical simulations of the evolution of low-mass, isothermal, molecular cores which are subjected to an increase in external pressure. If the external pressure increases very slowly, the core approaches instability quite quasi-statically. However, for faster compressions, a compression wave is driven into the core (Hennebelle, P., Whitworth, A., Gladwin, P. and André, P.: 2003a MNRAS 340, 870). Quantitative comparisons with observational velocity and density profiles are presented. The consequences of this compression for the fragmentation of the cloud is investigated and discussed. 相似文献
994.
Yvon Halbwachs Gabriel Courrioux Xavier Renaud Philippe Repusseau 《Mathematical Geology》1996,28(5):625-656
The consistent geometric and topological representation of a fault network is possible through a method based on the implementation of 3-dimensional Generalized maps (3-G-map) enabling all subdivisions of space to be represented. The fault network is modeled as an assemblage of polygonal faces from a set of geometric data on the faults and a knowledge of the relationships between the faults. The resultant model is expressed in terms of a 3-G-map in which volume, surface, and topological information is constructed taking into account computed intersections between faults and known interception relations. The fault network can be edited through an interactive 3-D viewer which provides several tools for navigating within the 3-G-map. Information relevant to a fault network, such as block geometry, connectivity, adjacencies, and connectivity relationships, can be obtained by exploring the data structure of the 3-G-map. The fault network architecture is made comprehensive through interactive modeling and visualization. 相似文献
995.
This paper presents the second part of a work that aims at developing a mechanical model for the behaviour of propellant‐like materials under high confining pressure and strain rate. The model is to be employed to determine the temperature rise due to mechanical dissipation during a dynamic penetration event. Using the kinematical and thermodynamic background derived in the first part, a viscoelastic–viscoplastic–compaction model is put forward and identified. Viscoelasticity and compaction refer to the elastomeric nature of the material, while viscoplasticity, including implicit damage through dilatancy, reflects its granular nature. Some numerical exercises are performed, in view of determining the major model forces and weaknesses, and of assessing the numerical algorithm robustness. A penetration event is preliminarily simulated, and a temperature rise field predicted. Necessary model improvements are finally discussed, together with several ways of research for a longer term approach. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
996.
The X-ray source IGR J16318-4848 was the first source discovered by INTEGRAL on January 29, 2003. The high energy spectrum
exhibits such a high column density that the source is undetectable in X-rays below 2 keV. On February 23–25, 2003 we triggered
a Target of Opportunity (ToO) Program using the EMMI and SOFI instruments on the New Technology Telescope of the European
Southern Observatory (La Silla) to get optical and near-infrared (NIR) observations. We discovered the optical counterpart,
and confirmed the already proposed candidate in the NIR. NIR spectroscopy revealed a large amount of emission lines, including
forbidden iron lines and P-Cygni profiles, showing a strong similarity with CI Cam, another strongly absorbed source. Together
with the spectral energy distribution (SED), these data point to a high luminosity, high temperature source, with an intrinsic
absorption greater than the interstellar absorption, but two orders of magnitude below the X-ray absorption. All these observations
show that IGR J16318-4848 is a high mass X-ray binary (HMXB) at a distance between 0.9 and 6.2 kpc, the mass donor being an
early-type star, probably a sgB[e] star, surrounded by a dense and absorbing circumstellar material. This would make the second
HMXB with a sgB[e] star as the mass donor after CI Cam.
Other sources, discovered by INTEGRAL near IGR J16318-4848 in the direction of the Norma arm, present the same characteristics,
at least in X-rays. Such sources may represent a different evolutionary state of X-ray binaries previously undetected with
the lower energy space telescopes; if it is so, a new class of strongly absorbed X-ray binaries is being unveiled by INTEGRAL.
Out of the 15 sources present in this region, only one might be associated with an unidentified EGRET source: IGR J16393-4643.
Therefore these obscured INTEGRAL sources do not seem to be powerful high energy (E > 100 MeV) emitters.
Based on observations collected at the European Southern Observatory, Chile (proposal ESO N∘ 70.D-0340). 相似文献
997.
The discovery of the microquasar LS 5039 well within the 95% confidence contour of the Unidentified EGRET Source (UES) 3EG
J1824−1514 was a major step towards the possible association between microquasars (MQs) and UESs. The recent discovery of
precessing relativistic radio jets in LS I +61 303, a source associated for long time with 2CG 135+01 and with the UES 3EG
J0241+6103, has given further support to this idea. Finally, the very recently proposed association between the microquasar
candidate AX J1639.0−4642 and the UES 3EG J1639−4702 points towards a population of High Mass X-ray Binary (HMXB)/Neutron
Star (NS) microquasars as counterparts of low-latitude unidentified EGRET sources. 相似文献
998.
An object located approximately atl=8°,b=–4° with a mean radial velocity of –212.3 km s–1 has been observed in the 21 cm neutral hydrogen line. The mean weighted velocity dispersion is 11.2 km s–1 and the total mass is estimated to be 190R
2 (kpc) solar masses. We discuss possible interpretations of the origin and nature of this object. The most likely interpretation is that we observe an expanding object which has been ejected from the galactic nucleus. 相似文献
999.
David Bertrand Franois Nicot Philippe Gotteland Stphane Lambert 《Computers and Geotechnics》2005,32(8):564-577
Reinforced soil structures can be used to protect infrastructures against rockfalls. An innovative way to implement such protection is to construct the front face using a cellular assembly. This paper focuses on the cellular scale, with the cell a complex heterogeneous material, composed of a wire netting box filled with rocky particles. The behaviour of a single cell was modelled using the discrete element method, thus accounting for the interaction between the rocky particles and the interaction between the box and the rocky particles. A constitutive model was developed and calibrated along confined compression loading paths, then preliminary elements of validation were obtained from the simulation of unconfined compression tests. 相似文献
1000.
Antoine Rabatel Vincent Jomelli Philippe Naveau Bernard Francou Delphine Grancher 《Comptes Rendus Geoscience》2005,337(15):1311-1322
Fluctuations of the Charquini glaciers (Cordillera Real, Bolivia) have been reconstructed for the Little Ice Age (LIA) from a set of 10 moraines extending below the present glacier termini. A lichenometric method using the Rhizocarpon geographicum was used to date the moraines and reconstruct the main glacier fluctuations over the period. The maximum glacier extent occurred in the second half of the 17th century, followed by nearly continuous retreat with three interruptions during the 18th and the 19th centuries, marked by stabilisation or minor advances. Results obtained in the Charquini area are first compared with other dating performed in the Peruvian Cordillera Blanca and then with the fluctuations of documented glaciers in the Northern Hemisphere. Glacier fluctuations along the tropical Andes (Bolivia and Peru) were in phase during the LIA and the solar forcing appears to be important during the period of glacier advance. Compared with the Northern Hemisphere mid-latitudes, the major advance observed on these glaciers during the first half of the 19th century is not present in the tropical Andes. This discrepancy may be due to regional scale climate variations. To cite this article: A. Rabatel et al., C. R. Geoscience 337 (2005). 相似文献