全文获取类型
收费全文 | 469篇 |
免费 | 28篇 |
国内免费 | 13篇 |
专业分类
测绘学 | 19篇 |
大气科学 | 48篇 |
地球物理 | 130篇 |
地质学 | 197篇 |
海洋学 | 50篇 |
天文学 | 29篇 |
综合类 | 4篇 |
自然地理 | 33篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 32篇 |
2020年 | 26篇 |
2019年 | 28篇 |
2018年 | 30篇 |
2017年 | 28篇 |
2016年 | 29篇 |
2015年 | 11篇 |
2014年 | 25篇 |
2013年 | 46篇 |
2012年 | 30篇 |
2011年 | 30篇 |
2010年 | 13篇 |
2009年 | 24篇 |
2008年 | 19篇 |
2007年 | 15篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 16篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 1篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有510条查询结果,搜索用时 15 毫秒
171.
The development of a coupled damage‐plasticity constitutive model for concrete is presented. Emphasis is put on thermodynamic admissibility, rigour and consistency both in the formulation of the model, and in the identification of model parameters based on experimental tests. The key feature of the thermodynamic framework used in this study is that all behaviour of the model can be derived from two specified energy potentials, following procedures established beforehand. Based on this framework, a constitutive model featuring full coupling between damage and plasticity in both tension and compression is developed. Tensile and compressive responses of the material are captured using two separate damage criteria, and a yield criterion with a multiple hardening rule. A crucial part of this study is the identification of model parameters, with these all being shown to be identifiable and computable based on standard tests on concrete. Behaviour of the model is assessed against experimental data on concrete. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
172.
E.F. van Dishoeck W.-F. Thi G.-J. van Zadelhoff 《Astrophysics and Space Science》2003,285(3-4):691-698
We report the first detection of DCO+ in a circumstellar disk. The DCO+
J=5–4 line at 360.169 GHz is observed with the 15 m James Clerk Maxwell Telescope in the disk around the pre-main sequence
star TW Hya. Together with measurements of the HCO+ and H13CO+
J=4–3 lines, this allows an accurate determination of the DCO+/HCO+ ratio in this disk. The inferred value of0.035±0.005 is close to that found in cold pre-stellar cores and is somewhat higher
than that measured in the envelope around the low-mass proto star IRAS 16293-2422. It is also close to the DCN/HCN ratio obtained
for pristine cometary material in the jet of comet Hale-Bopp. The observed DCO+/HCO+ ratio for TW Hya is consistent with theoretical models of disks which consider gas-phase fractionation processes within a
realistic 2-D temperature distribution and which include the effects of freeze-out onto grains.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
173.
1 IntroductionOneofthemaintasksinstudyinggeodynamicprocessisevaluatingtherateofearthcrustmove ments.Normally ,themethodsforstudyingearthcrustmovementareestablishedonthebasisoftheobjectofstudyandtherequirementsfortheresultstobeobtainedasfollows.1 )Tostudythemovingprocessofcrustplatesinalargeareaandwithinacertaintectonicperiod ,geologicmethodsareusuallyused .2 )Geodeticmeasurementsarecarriedoutinanareacoveringfromsomekm2 totensofkm2 andal lowtodeterminethedisplacementoftheearthcrustwithinaperio… 相似文献
174.
Pierre Ocvirk Ariane Lançon Christophe Pichon Philippe Prugniel Damien Le Borgne Brigitte Rocca-Volmerange Michel Fioc Caroline Soubiran Eric Thiébaut 《Astrophysics and Space Science》2003,284(2):933-936
We present inversion techniques which aim at recovering the composite nature and the kinematics of a stellar population from
its high resolution absorption line spectrum. The originality of the combined inversion is its potential to recover both the
stellar content and the kinematics simultaneously. These techniques use new synthetic high resolution spectra produced by
PéGASE and minimization algorithms. We apply them to mock data representing the bulge and disk population of the inner region
of spiral galaxies.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
175.
This paper presents an analytical study of the longitudinal dynamics of a thrusting, lifting, orbital vehicle in a nearly circular orbit. The translational motion is composed of a nonlinear oscillation, or phugoid, and a spiral mode which results in either decay or dilatation of the orbit depending on the perturbed initial conditions. The nonlinear effects on the phugoid period and damping are small in the altitude range considered. Elements of the orbit such as radial distance, velocity, and flight path angle were obtained explicitly as functions of time. The behavior of the variations of these elements is correctly predicted. Explicit expressions for period and damping of the angle-of-attack mode were derived. It is shown that a critical altitude may exist at which the phugoid mode and the angle-of-attack mode have nearly equal periods. Near this resonance altitude linearized solutions are no longer valid and a study of the nonlinear equations shows that there is a strong interactions between the translational and the rotational modes resulting in a switching of the two frequencies of oscillations.This work was supported by NASA Contract No. NASr 54(06). 相似文献
176.
A. Nguyen Van Nghia Jougnot Damien Thanh Luong Duy Van Do Phan Thuy Tran Thi Chung Hue Dang Thi Minh Hung Nguyen Manh 《Hydrogeology Journal》2021,29(6):2017-2031
Hydrogeology Journal - Predicting the permeability of porous media in saturated and partially saturated conditions is of crucial importance in many geo-engineering areas, from water resources to... 相似文献
177.
Landslides - The frequency of landslides and their magnitude are increasing worldwide due to global climate change, causing damage to people and infrastructure. Therefore, landslide risk assessment... 相似文献
178.
Binh Thai Pham Abolfazl Jaafari Tran Van Phong Hoang Phan Hai Yen Tran Thi Tuyen Vu Van Luong Huu Duy Nguyen Hiep Van Le Loke Kok Foong 《地学前缘(英文版)》2021,12(3):101105
Improving the accuracy of flood prediction and mapping is crucial for reducing damage resulting from flood events. In this study, we proposed and validated three ensemble models based on the Best First Decision Tree (BFT) and the Bagging (Bagging-BFT), Decorate (Bagging-BFT), and Random Subspace (RSS-BFT) ensemble learning techniques for an improved prediction of flood susceptibility in a spatially-explicit manner. A total number of 126 historical flood events from the Nghe An Province (Vietnam) were connected to a set of 10 flood influencing factors (slope, elevation, aspect, curvature, river density, distance from rivers, flow direction, geology, soil, and land use) for generating the training and validation datasets. The models were validated via several performance metrics that demonstrated the capability of all three ensemble models in elucidating the underlying pattern of flood occurrences within the research area and predicting the probability of future flood events. Based on the Area Under the receiver operating characteristic Curve (AUC), the ensemble Decorate-BFT model that achieved an AUC value of 0.989 was identified as the superior model over the RSS-BFT (AUC = 0.982) and Bagging-BFT (AUC = 0.967) models. A comparison between the performance of the models and the models previously reported in the literature confirmed that our ensemble models provided a reliable estimate of flood susceptibilities and their resulting susceptibility maps are trustful for flood early warning systems as well as development of mitigation plans. 相似文献
179.
The paper analyzes the possibility for countering ballistic perturbations of the interplanetary transfer trajectory of the spacecraft with electric propulsion (EP) associated with the temporary impossibility of the normal use of the EP in phases of the heliocentric transfer. The main result of the present study is the method for the determination of a new nominal trajectory, at any point of which the allowed duration of the emergency shutdown of electric propulsion is large enough. The numerical analysis is given for one of the possible scenarios of spacecraft injection into the operational heliocentric orbit for solar research. 相似文献
180.
Nga Thi Thanh Pham Quang Hong Nguyen Anh Duc Ngo Hang Thi Thu Le Cong Tien Nguyen 《Natural Hazards》2018,92(1):189-204
Flooding associated with landing tropical cyclones (TCs) is one of the major natural hazards in the coastal region of Vietnam. Annually, approximately 5 or 6 TCs make landfall in Vietnam, bringing heavy rains and inducing flooding, particularly to the central coastal region because of its topography and geographic configuration. This study focuses on the modelling of typhoon-induced floods that have resulted in widespread damage to agriculture over the central Thua Thien Hue Province of Vietnam by coupling two well-known hydrological models, KINEROS2 and HEC-RAS (Daniel et al. in Open Hydrol J 5(1), 2011), and using GSMaP (Global Satellite Mapping of Precipitation) data as the satellite rainfall input. Landsat imagery and GIS are also used for mapping and analysing the inundated areas. The discharge and water level from the KINEROS2 and HEC-RAS models displayed acceptable results for the floods modelled from three selected typhoons; both the Nash–Sutcliffe simulation efficiency coefficient (NSE) and the coefficient of determination (R2) were greater than 0.6. The simulated inundation maps of these typhoon-induced floods were compared with those extracted from the Landsat imagery to assess consistency. The result revealed a similar spatial extension of the inundated agricultural areas. This information, together with the forecasted TC movements and associated rainfalls, will be helpful to plan methods for mitigating potential typhoon-induced flooding and damage, particularly damage to agricultural regions. 相似文献