全文获取类型
收费全文 | 571篇 |
免费 | 13篇 |
国内免费 | 19篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 95篇 |
地球物理 | 119篇 |
地质学 | 157篇 |
海洋学 | 173篇 |
天文学 | 27篇 |
综合类 | 9篇 |
自然地理 | 14篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 12篇 |
2019年 | 8篇 |
2018年 | 29篇 |
2017年 | 34篇 |
2016年 | 43篇 |
2015年 | 41篇 |
2014年 | 36篇 |
2013年 | 37篇 |
2012年 | 34篇 |
2011年 | 53篇 |
2010年 | 43篇 |
2009年 | 35篇 |
2008年 | 26篇 |
2007年 | 24篇 |
2006年 | 25篇 |
2005年 | 20篇 |
2004年 | 12篇 |
2003年 | 18篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 2篇 |
1997年 | 6篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有603条查询结果,搜索用时 125 毫秒
311.
The Daejosa Buddha is formed of highly weathered coarse grained biotite granite. The main body is dark green due to a covering of lichens. The main body of the Buddha has developed nearly vertical, horizontal and oblique joint systems. Results of physical properties for the rock samples from the Daejosa Buddha are lower than for normal fresh granite as the primary minerals of the host rocks have been altered to clay and iron hydroxide minerals. Spore and mycelium of green algaes and some plants cover the surface of the standing Buddha and fill the pore space of the surrounding rocks. Considering the weathering and state of deterioration, the Buddha statue requires conservation treatment. Restoration may be largely divided into the head part, upper and lower parts, and the back side of the Buddha. The head and the cap rock were joined and restored with unslaked lime filling. The head and stone crown of the Buddha were fitted and restored using an epoxy type resin with high viscosity that was mixed with granite powder and talc as petro-fillers. For the back side, resin was applied for reinforcement. Araldite and hardener of low viscosity that were used with the addition of glass fibers. Finally, texture and color matching treatments were carried out. 相似文献
312.
Performance of Singapore Integrated Multiple Reference Station Network (SIMRSN) for RTK Positioning 总被引:1,自引:0,他引:1
Conventional RTK positioning is usable, but requires the use of a local base station. It is also restricted by the effects
of the de-correlate atmospheric refraction on the GPS signal, which limits the use of the RTK positioning up to distances
of 10–15 km from the reference station to the user. With a multiple reference station network approach, precise RTK positioning
capability may be extended for a much larger area. The Singapore Integrated Multiple Reference Station Network (SIMRSN) has
been established for this purpose. Using an existing method termed linear combination method, the multiple reference station
network corrections are generated for the user on an epoch by epoch, satellite-by-satellite basis. A residual-based adaptive
Kalman filter is proposed to improve network correction availability. The VRS concept is used to transmit corrections to the
user for RTK positioning. Field tests were conducted to demonstrate the general performance of SIMRSN. The tests confirmed
that RTK positioning within a multiple reference station network can provide the user with better than 3 cm in horizontal
position, the height accuracy is in the range of 1–7 cm, and the average TTF (Time To Fix) are 46 and 76 s during GLC station
and LPR station tests, respectively. With this highly efficient survey technique, the user needs only to be equipped with
a single GPS receiver. This reduces equipment and manpower costs compared with traditional RTK positioning using a specially
set up reference station. The multiple reference station framework also paves the way for various other applications beyond
the traditional surveying profession.
Electronic Publication 相似文献
313.
The Bulkugsa Dabotap pagoda was built in AD 761, and designated as World Cultural Heritage by UNESCO in 1995. The ca. 270 blocks used in the construction of the pagoda consist mainly of white grey alkali granite with medium-grained equi-granular texture and small mialolitic cavities. Small quantities of biotite granite, granodiorite, gabbroic and tuffaceous rocks were also used. Some overlapping blocks are very damp. The pagoda body is inclined toward the northeast owing to differential loading. Fractures and artificial deterioration of the pagoda are not serious, but the surfaces of blocks show exfoliations that indicate granular decomposition of minerals. The supporting rocks and the round handrail of the octagonal second floor are too weathered to be treated and are being replaced. The roof stones on the first and second floor are seriously damaged because there is no drainage route for rainwater. The joints between blocks have fractures that cross each other; they have been further damaged by inserting concrete, cement mortar, rock fragments and iron plates. This has accelerated discoloration and fractures. Widespread colonization by algae, fungi, lichens and bryophytes has occurred on the margins and surfaces roof stones of the pagoda. Chemical treatment will be necessary to remove the vegetation cover. 相似文献
314.
The separation of heavy metals from wastewater may be improved by precipitation/flocculation with iron- or aluminium salts. Often, the resulting products are voluminous, water-containing, amorphous hydroxides which show only limited flocculation properties and may possibly pose problems with the technical separation from the aqueous phase. The application of magnetite could be advantageous because magnetite is ferromagnetic and can be separated very quickly in a magnetic field. First of all, a simple preparation method for magnetite was studied. Pure magnetite could be prepared by mixing an iron(II) salt solution with an equivalent amount of sodium hydroxide at room temperature without oxidation by air. The required reaction time was only 3 hours. For the precipitation of heavy metals from an electroplating wastewater, a better metal elimination and smaller sludge volumes resulted with that artificially produced magnetite in comparison with a precipitation by NaOH. Thereby not only the adsorption of metals was established but also coagulation effects of the magnetite sludge with small metal hydroxide particles. By means of the experimental results. sorption of nickel and chromium was compiled as function of pH and precipitation time. Because freshly precipitated magnetite shows very good sorption and flocculation properties, and pH of precipitation may be lower, its use in high gradient magnetic separation (HGMS) could be more effective for metal elimination than magnetite powder. 相似文献
315.
R. A. Cliff G. Jones W. C. Choi T. J. Lee 《Contributions to Mineralogy and Petrology》1985,90(4):346-352
The NE/SW trending Ogcheon Belt formed during the Mesozoic by deformation and metamorphism of a sedimentary sequence which includes tillite formations of late Precambrian or Lower Palaeozoic age. In this study Rb-Sr isotopic data are reported from cm-scale sampling of clasts and matrix in these tillites, which underwent metamorphism at grades ranging from the biotite zone to the kyanite zone. Sr-isotopic disequilibrium between clasts and matrix persists up to the highest grade but in four out of five rocks the matrix samples approximate to isochrons (MSWD's<12). The mechanism for this selective isotopic equilibration is considered to be related to the metamorphic reactions in the matrix, which were probably accompanied by a substantial fluid flow. The matrix isochrons for three of the rocks, together with separated white micas from associated schists, suggest that metamorphism took place in the Trias, approximately 200 Myr ago. Metamorphism was followed by slow cooling and biotite closure temperatures were not reached until 190-150 Myr. — These results suggest that where high fluid/rock ratios can be demonstrated on independent petrological grounds, the analysis of small-scale whole-rock samples may allow effective Rb/Sr dating of metamorphism. 相似文献
316.
To dispose of the spent fuels generated from the Korean nuclear power plants in an underground repository, a large area of
about 4 km2 is required. This could be a constraint for selecting an adequate repository site and it is required to investigate the possibility
of a multi-level repository design. In this study different parameters related to the multi-level repository design such as
the level distance, waste type disposed of at each level, and the time interval between the operations at the levels, were
investigated using the three-dimensional code, FLAC3D. For obtaining more reliable results, rock properties measured from
deep boreholes were used. From the analysis, it was possible to conclude that a multi-level repository concept could be an
attractive alternative to reduce the underground area as well as to dispose of the spent fuels from Pressurized Water Reactors
(PWR) and Canadian Deuterium Uranium (CANDU) reactors at different levels with different time schedules. 相似文献
317.
318.
Sequential tracer tests for determining water seepage paths in a large rockfill dam, Nakdong River basin, Korea 总被引:2,自引:0,他引:2
Jin-Yong Lee Hyoung-Soo Kim Yea-Kwon Choi Jeong-Woo Kim Jeong-Yong Cheon Myeong-Jae Yi 《Engineering Geology》2007,89(3-4):300-315
The rockfill dam of this study has a clay core, filter zone, and sandy gravel shell, and it is located in the Nakdong River basin in Korea. Filling the reservoir began in August 1994 and it was full by April 1998. When the reservoir level was approximately 150 m, three settlement holes were found in the dam crest. To determine possible seepage paths and potential damaged areas within the rockfill dam, 15 tracer tests were performed during two periods. During the two test periods, six and nine tracer tests were conducted when the average water levels of the reservoir were 145 m and 142 m, respectively. Rhodamine WT (RWT) and bromide ion were used as tracers. For each test, 1800 to 4000 L of tracer solution were injected into the riprap for about 5 h. The 15 injection points were uniformly distributed from the right to left sides of the embankment and the two tracers were injected alternately. Tracer concentrations were monitored at 26 observation wells, which were divided into four groups by their geographical positions: right side of the crest, left side of the crest, right side of the dam toe, and left side of the dam toe. For each tracer test, more than 30 water samples were taken during a period of 96 h at each observation well. Based the breakthrough curves obtained from the sequential tracer tests, it was inferred that the most probable seepage paths and potential damaged area were in the left side of the crest (tongue wing zone) and, to a lesser extent, in the right side of the dam abutment. 相似文献
319.
Urban impervious surfaces are considered as key indicator of urbanization intensity and environmental quality. Due to their significant impact on surface runoff, flood frequency, and water quality, impervious surfaces have been identified as an important indicator for examining the hydrological impact of urbanization. The amount and distribution of impervious surfaces have been estimated using remote sensing and geographic information system (GIS) techniques. Little research, however, has been conducted to predict future impervious surface distributions. To address this problem, we developed an integrated residential/commercial growth and impervious surface distribution model to predict urban impervious surface distribution. Taking Milwaukee River Basin, Wisconsin as a case study, we simulated future residential and commercial developments using a CA model. Further, we developed a linear regression model to predict impervious surface distributions in residential and commercial land uses. Analysis of results suggests that the proposed model performs significantly better than the traditional approaches. 相似文献
320.
This paper examines the current procedure for determining the soil-water characteristic curve (SWCC) model with a particular focus on its application to slope stability analysis under transient unsaturated seepage conditions. A series of laboratory experiments was performed to determine the SWCC of different soils, ranging from high plasticity clay to silty sand, found across the Korean Peninsula. The experimental results were utilized to identify the suitable SWCC model for each soil type based on the fitting criterion. Also, this paper developed a numerical framework for infinite slope stability analysis under transient unsaturated seepage conditions. The significant advantage of the proposed framework, from the practical viewpoint, is to directly predict the timing of failure and potential failure plane based on rainfall recording. The effect of choice of SWCC models on predictability in stability analysis was evaluated by adopting the present framework along with the identified SWCC models. Furthermore, a case study of landslides after a 3-month rainfall in Pohang, Korea, was revisited to assess the performance of the proposed framework. The obtained results demonstrate the significant role of SWCC model on the results of slope stability analysis. The analysis using the SWCC model satisfying the fitting criterion could still not capture the real behavior of unsaturated soil. The comprehensive transient analysis is strongly suggested as a complementary means to the current fitting criterion for determining the suitable SWCC model for stability analysis under transient seepage conditions. 相似文献