全文获取类型
收费全文 | 313篇 |
免费 | 4篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 35篇 |
地球物理 | 72篇 |
地质学 | 91篇 |
海洋学 | 29篇 |
天文学 | 59篇 |
综合类 | 2篇 |
自然地理 | 21篇 |
出版年
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 15篇 |
2014年 | 7篇 |
2013年 | 10篇 |
2012年 | 10篇 |
2011年 | 14篇 |
2010年 | 19篇 |
2009年 | 13篇 |
2008年 | 14篇 |
2007年 | 31篇 |
2006年 | 13篇 |
2005年 | 18篇 |
2004年 | 13篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1971年 | 2篇 |
1965年 | 1篇 |
1953年 | 1篇 |
1952年 | 1篇 |
排序方式: 共有320条查询结果,搜索用时 31 毫秒
41.
Oscar Agertz George Lake Romain Teyssier Ben Moore Lucio Mayer Alessandro B. Romeo 《Monthly notices of the Royal Astronomical Society》2009,392(1):294-308
Observations of turbulent velocity dispersions in the H i component of galactic discs show a characteristic floor in galaxies with low star formation rates and within individual galaxies the dispersion profiles decline with radius. We carry out several high-resolution adaptive mesh simulations of gaseous discs embedded within dark matter haloes to explore the roles of cooling, star formation, feedback, shearing motions and baryon fraction in driving turbulent motions. In all simulations the disc slowly cools until gravitational and thermal instabilities give rise to a multiphase medium in which a large population of dense self-gravitating cold clouds are embedded within a warm gaseous phase that forms through shock heating. The diffuse gas is highly turbulent and is an outcome of large-scale driving of global non-axisymmetric modes as well as cloud–cloud tidal interactions and merging. At low star formation rates these processes alone can explain the observed H i velocity dispersion profiles and the characteristic value of ∼10 km s−1 observed within a wide range of disc galaxies. Supernovae feedback creates a significant hot gaseous phase and is an important driver of turbulence in galaxies with a star formation rate per unit area ≳10−3 M⊙ yr−1 kpc−2 . 相似文献
42.
43.
M. Mapelli B. Moore L. Giordano L. Mayer M. Colpi E. Ripamonti S. Callegari 《Monthly notices of the Royal Astronomical Society》2008,383(1):230-246
Chandra and XMM–Newton observations of the Cartwheel galaxy show ∼17 bright X-ray sources (≳5 × 1038 erg s−1 ) , all within the gas-rich outer ring. We explore the hypothesis that these X-ray sources are powered by intermediate-mass black holes (IMBHs) accreting gas or undergoing mass transfer from a stellar companion. To this purpose, we run N -body/smoothed particle hydrodynamics simulations of the galaxy interaction which might have led to the formation of Cartwheel, tracking the dynamical evolution of two different IMBH populations: halo and disc IMBHs. Halo IMBHs cannot account for the observed X-ray sources, as only a few of them cross the outer ring. Instead, more than half of the disc IMBHs are pulled in the outer ring as a consequence of the galaxy collision. However, also in the case of disc IMBHs, accretion from surrounding gas clouds cannot account for the high luminosities of the observed sources. Finally, more than 500 disc IMBHs are required to produce ≲15 X-ray sources via mass transfer from very young stellar companions. Such number of IMBHs is very large and implies extreme assumptions. Thus, the hypothesis that all the observed X-ray sources in Cartwheel are associated with IMBHs is hardly consistent with our simulations, even if it is still possible that IMBHs account for the few (≲1–5) brightest ultraluminous X-ray sources. 相似文献
44.
M. Mapelli B. Moore E. Ripamonti L. Mayer M. Colpi L. Giordano 《Monthly notices of the Royal Astronomical Society》2008,383(3):1223-1231
We simulate the collisional formation of a ring galaxy and we integrate its evolution up to 1.5 Gyr after the interaction. About 100–200 Myr after the collision, the simulated galaxy is very similar to observed ring galaxies (e.g. Cartwheel). After this stage, the ring keeps expanding and fades. Approximately 0.5–1 Gyr after the interaction, the disc becomes very large (∼100 kpc) and flat. Such extended discs have been observed only in giant low surface brightness galaxies (GLSBs). We compare various properties of our simulated galaxies (surface brightness profile, morphology, H i spectrum and rotation curve) with the observations of four well-known GLSBs (UGC 6614, Malin 1, Malin 2 and NGC 7589). The simulations match quite well the observations, suggesting that ring galaxies could be the progenitors of GLSBs. This result is crucial for the cold dark matter (CDM) model, as it was very difficult, so far, to explain the formation of GLSBs within the CDM scenario. 相似文献
45.
The calculation of runoff and infiltration parameters is a fundamental task for water budget estimation and water resources management. The “Kenessey method” allows these values to be calculated and its use is widespread among water scientists and practitioners. Due to language barriers and inefficient translation in past decades, the method has undergone some misinterpretations and is now far from its original usefulness and purpose. The use of the modified method can give unreal results for specific climatic zones. The purpose of this paper is to point out these methodological variations and to return to the original approach, improving it with modern technology. 相似文献
46.
Saverio Romeo Lucio Di Matteo Laura Melelli Corrado Cencetti Walter Dragoni Andrea Fredduzzi 《Landslides》2017,14(4):1457-1465
On October 30, 2016, a seismic event and its aftershocks produced diffuse landslides along the SP 209 road in the Nera River Gorge (Central Italy). Due to the steep slopes and the outcropping of highly fractured and bedded limestone, several rockfalls were triggered, of which the main event occurred on the slope of Mount Sasso Pizzuto. The seismic shock acted on a rock wedge that, after an initial slide, developed into a rockfall. The debris accumulation blocked the SP 209 road and dammed the Nera River, forming a small lake. The river discharge was around 3.6 m3/s; the water overtopped the dam and flooded the road. By a preliminary topographic survey, we estimated that the debris accumulation covers an area of about 16,500 m2, while the volume is around 70,000 m3. The maximum volume occupied by the pre-existing talus mobilized by the rockfall is about 20% of the total volume. Besides blocking the road, the rockfall damaged a bridge severely, while, downstream of the dam, the water flow caused erosion of a road embankment. A rockfall protection gallery, a few hundred meters downstream of the dam, was damaged during the event. Other elastic nets and rigid barriers were not sufficient to protect the road from single-block rockfalls, with volumes around 1–2 m3. Considering the geological and geomorphological conditions, as well as the high seismicity and the socioeconomic importance of the area, a review of the entire rockfall protection systems is required to ensure protection of critical infrastructure and local communities. 相似文献
47.
48.
Dynamics of the circulation in the Sea of Marmara: numerical modeling experiments and observations from the Turkish straits system experiment 总被引:4,自引:3,他引:1
Jacopo?ChiggiatoEmail author Ewa?Jarosz Jeffrey?W.?Book James?Dykes Lucio?Torrisi Pierre-Marie?Poulain Riccardo?Gerin Jochen?Horstmann ?ükrü?Be?iktepe 《Ocean Dynamics》2012,62(1):139-159
During September 2008 and February 2009, the NR/V Alliance extensively sampled the waters of the Sea of Marmara within the
framework of the Turkish Straits System (TSS) experiment coordinated by the NATO Undersea Research Centre. The observational
effort provided an opportunity to set up realistic numerical experiments for modeling the observed variability of the Marmara
Sea upper layer circulation at mesoscale resolution over the entire basin during the trial period, complementing relevant
features and forcing factors revealed by numerical model results with information acquired from in situ and remote sensing
datasets. Numerical model solutions from realistic runs using the Regional Ocean Modeling System (ROMS) produce a general
circulation in the Sea of Marmara that is consistent with previous knowledge of the circulation drawn from past hydrographic
measurements, with a westward meandering current associated with a recurrent large anticyclone. Additional idealized numerical
experiments illuminate the role various dynamics play in determining the Sea of Marmara circulation and pycnocline structure.
Both the wind curl and the strait flows are found to strongly influence the strength and location of the main mesoscale features.
Large displacements of the pycnocline depth were observed during the sea trials. These displacements can be interpreted as
storm-driven upwelling/downwelling dynamics associated with northeasterly winds; however, lateral advection associated with
flow from the Straits also played a role in some displacements. 相似文献
49.
Maria Giovanna Durante Luigi Di Sarno George Mylonakis Colin A. Taylor Armando Lucio Simonelli 《地震工程与结构动力学》2016,45(7):1041-1061
An effective way to study the complex seismic soil‐structure interaction phenomena is to investigate the response of physical scaled models in 1‐g or n‐g laboratory devices. The outcomes of an extensive experimental campaign carried out on scaled models by means of the shaking table of the Bristol Laboratory for Advanced Dynamics Engineering, University of Bristol, UK, are discussed in the present paper. The experimental model comprises an oscillator connected to a single or a group of piles embedded in a bi‐layer deposit. Different pile head conditions, that is free head and fixed head, several dynamic properties of the structure, including different masses at the top of the single degree of freedom system, excited by various input motions, e.g. white noise, sinedwells and natural earthquake strong motions recorded in Italy, have been tested. In the present work, the modal dynamic response of the soil–pile–structure system is assessed in terms of period elongation and system damping ratio. Furthermore, the effects of oscillator mass and pile head conditions on soil–pile response have been highlighted, when the harmonic input motions are considered. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
50.
AbstractA semi-distributed hydrological model and reservoir optimization algorithm are used to evaluate the potential impacts of climate change on existing and proposed reservoirs in the Sonora River Basin, Mexico. Inter-annual climatic variability, a bimodal precipitation regime and climate change uncertainties present challenges to water resource management in the region. Hydrological assessments are conducted for three meteorological products during a historical period and a future climate change scenario. Historical (1990–2000) and future (2031–2040) projections were derived from a mesoscale model forced with boundary conditions from a general circulation model under a high emissions scenario. The results reveal significantly higher precipitation, reservoir inflows, elevations and releases in the future relative to historical simulations. Furthermore, hydrological seasonality might be altered with a shift toward earlier water supply during the North American monsoon. The proposed infrastructure would have a limited ability to ameliorate future conditions, with more benefits in a tributary with lower flood hazard. These projections of the impacts of climate change and its interaction with infrastructure should be of interest to water resources managers in arid and semi-arid regions.
Editor D. Koutsoyiannis 相似文献