全文获取类型
收费全文 | 101篇 |
免费 | 1篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 6篇 |
地球物理 | 14篇 |
地质学 | 24篇 |
海洋学 | 25篇 |
天文学 | 32篇 |
自然地理 | 4篇 |
出版年
2022年 | 1篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 3篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有106条查询结果,搜索用时 31 毫秒
81.
Noriyuki Tanaka Yoichiro Takeda Shizuo Tsunogai 《Geochimica et cosmochimica acta》1983,47(10):1783-1790
Vertical and temporal variations in the radioactivities of Th-234, Pb-210 and Po-210 were measured at a station in Funka Bay from April 1979 to February 1980. The inventory of Th-234 showed a minimum in early spring, when a spring bloom of phytoplankton was observed, then a steady increase to a maximum value in late summer, just before open sea water invaded the bay and a secondary phytoplankton bloom started. The inventories of Pb-210 and Po-210 also showed minima in early spring. These results suggest that the removal of these nuclides from sea water is accelerated by biological activity. The concentration of Th-234 decreased with depth, but those of Po-210 and Pb-210 were higher in the bottom water in August 1979 when the bay water was strongly stratified. This may be due to the supply of Pb-210 and Po-210 from the bottom. However, if the supply of these nuclides is expected in sediment particles, the concentrations of these nuclides in suspended matter were not sufficient to explain their increments in the bottom water.Residence times of Th, Pb and Po were estimated by applying a non-steady state model to the bay water when the water stayed in and the concentrations of these nuclides were changing. The mean residence time of Th is not significantly different from that of Pb, but is about half of that of Po, although the difference is much smaller than that obtained by applying a steady state model. 相似文献
82.
Mineralogical and crystallographic data and electron microprobe analyses of silicate minerals for Antarctic ureilites Y74123, Y74130, Y74659, Y790981, ALHA77257, ALHA78019 and ALH82106 extend the chemical and textural variations among ureilites beyond those known for non-Antarctic ureilites. Low-Ca pyroxenes, possibly orthopyroxene, poikilitically enclosed in olivine and coexisting with Mg-rich pigeonites, have been identified in Y74659 and ALHA77257. Coexisting low-Ca pyroxene, pigeonite, and augite, together with the very Fe-rich olivine in ureilites were observed in Y74130. Almost Fe-free pigeonite and diopside coexist in ALH82106. No systematic differentiation trend has been reconstructed from these data, but the pyroxene pairs yield formation temperatures above 1200°C. A weak anticorrelation between MnO and FeO delineated by these pyroxenes suggests that a reduction reaction is responsible for the chemical variations. A working hypothesis for ureilite formation involves high-temperature episoded and a planetesimal-scale collision, which might have facilitated compaction and recrystallization of mafic silicates. During the episodes, FeNiS eutectic melt and a partial melt rich in Ca, Al and Fe might have been lost from a carbonaceous-chondrite-like source material. 相似文献
83.
Arch M. Reid Richard J. Williams Hiroshi Takeda 《Earth and Planetary Science Letters》1974,22(1):67-74
Steinbach is a stony-iron meteorite with approximately equal amounts of silicate and metal that shows Widmanstätten structure. The silicate portion contains tridymite, orthobronzite, and clinobronzite that formed by inversion from high-temperature protobronzite. The assemblage orthobronzite-protobronzite-tridymite-metallic iron indicates an equilibrium temperature of 1200°C and an ?o2 of 10?12 under a total pressure of less than 2 kbar. Preservation of the high-temperature phase relations implies much more rapid cooling in the 1200-700°C range than the rates that have been deduced for the development of Widmanstätten structure in the 700-500°C range. 相似文献
84.
Takashi?SasaokaEmail author Tri?Karian Akihiro?Hamanaka Hideki?Shimada Kikuo?Matsui Masatomo?Ichinose 《Geotechnical and Geological Engineering》2016,34(2):671-678
The basic objectives of mine roadways are to provide sufficient cross sections to accommodate equipment, transport, personnel travel and ventilation. However, many roadways become damaged to the extent of needing maintenance, generally dinting, and in some cases requiring re-ripping. Strata conditions play important effects on stability of roadways and other mining activities. Weak rocks cause excessive roadway closures, and water softens some rocks and worsens the closure problem. Therefore, study on effect of mine water on the stability of underground coal mine roadways is important for underground coal mine development. A scientific discussion on the effect of water on the stability of roadways is given on the basis of results obtained by means of field investigation and laboratory tests. Based on analysis, rock in saturated condition has only between 0.19 to 0.49 of its compressive strength and 0.17 to 0.59 of its tensile strength in dry condition. Among the coal measures rock in research area, water has the most obvious effect on the strength reduction of shale. The slaking behavior of shale has also been the worst among the other. Field investigation of roadway driven in shale shown vertical closure in the wet and dry condition area reached 40–60 and 5–15 cm respectively, in 30 days after the drivage. Among the measures, drainage is considered to be the most economical and simplest method to reduce the water content in the rocks or the rock masses. 相似文献
85.
Takaya Iwasaki Keiji Adachi Takeo Moriya Hiroki Miyamachi Takeshi Matsushima Kaoru Miyashita Testsuya Takeda Takaaki Taira Tomoaki Yamada Kazuo Ohtake 《Tectonophysics》2004,388(1-4):59
The Hidaka Collision Zone (HCZ), central Hokkaido, Japan, is a good target for studies of crustal evolution and deformation processes associated with an arc–arc collision. The collision of the Kuril Arc (KA) with the Northeast Japan Arc (NJA), which started in the middle Miocene, is considered to be a controlling factor for the formation of the Hidaka Mountains, the westward obduction of middle/lower crustal rocks of the KA (the Hidaka Metamorphic Belt (HMB)) and the development of the foreland fold-and-thrust belt on the NJA side. The “Hokkaido Transect” project undertaken from 1998 to 2000 was a multidisciplinary effort intended to reveal structural heterogeneity across this collision zone by integrated geophysical/geological research including seismic refraction/reflection surveys and earthquake observations. An E–W trending 227 km-long refraction/wide-angle reflection profile found a complicated structural variation from the KA to the NJA across the HCZ. In the east of the HCZ, the hinterland region is covered with 4–4.5 km thick highly undulated Neogene sedimentary layers, beneath which two eastward dipping reflectors were imaged in a depth range of 10–25 km, probably representing the layer boundaries of the obducting middle/lower crust of the KA. The HMB crops out on the westward extension of these reflectors with relatively high Vp (>6.0 km/s) and Vp/Vs (>1.80) consistent with middle/lower crustal rocks. Beneath these reflectors, more flat and westward dipping reflector sequences are situated at the 25–27 km depth, forming a wedge-like geometry. This distribution pattern indicates that the KA crust has been delaminated into more than two segments under our profile. In the western part of the transect, the structure of the fold-and-thrust belt is characterized by a very thick (5–8 km) sedimentary package with a velocity of 2.5–4.8 km/s. This package exhibits one or two velocity reversals in Paleogene sedimentary layers, probably formed by imbrication associated with the collision process. From the horizontal distribution of these velocity reversals and other geophysical/geological data, the rate of crustal shortening in this area is estimated to be greater than 3–4 mm/year, which corresponds to 40–50% of the total convergence rate between the NJA and the Eurasian Plate. This means that the fold-and-thrust belt west of the HCZ is absorbing a large amount of crustal deformation associated with plate interaction across Hokkaido Island. 相似文献
86.
Hideki Shimada Saeid Khazaei Kikuo Matsui 《Geotechnical and Geological Engineering》2004,22(2):161-186
In order to protect the safety of workers construction, as well as for environmental and cost reasons, efficient small-diameter
shallow tunneling methods have recently become increasingly important in regards to outside plant engineering such as for
water supplies, electricity, telecommunications and gas. The effects of the above projects in overcrowded urban areas are
significant and often result in substantial impact and traffic delays associated with a loss of travel time. Clearly the solution
to these utility placement problems, if the full impact of trench excavation is to be avoided, is trench less technology.
In particular, for construction work near existing facilities, underground tunnels that are excavated by slurry pipe-jacking
are being increasingly employed in order to avoid problems. Slurry pipe-jacking was firmly established as a special method
for the non-disruptive construction of the underground pipelines of sewage systems. Pipe-jacking, in its traditional form,
has occasionally been used for short railways, roads, rivers, and other projects. Basically the system involves the pushing
or thrusting of a drivage machine through concrete pipes ahead of jacks. This method utilizes mud slurry that is formed around
the pipes in order to stabilize the surrounding soil. Moreover, in recent years, the rectangular shape of the concrete pipe
in using slurry pipe-jacking was introduced due to the effective uses of the space. Based on his reason, the rectangular shape
of the concrete pipe is often adopted in Japan. From this point of view, this paper discusses the effect shapes have on the
stability of surrounding soil by means of the numerical analysis. Secondly, this paper discusses the performance of the mud
slurry around the drivage pipes by means of the two-dimensional Eulerian-Lagragian seepage analysis. Moreover, in slurry pipe-jacking,
the performance of the mud slurry plays an important role in the pushing process. Finally, the thrusts in slurry pipe-jacking
can be predicted accurately by evaluating the resistance between the mud slurry and the concrete pipes and the resistance
between the soil and the pipes in the curved jacking area.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
87.
88.
89.
A quantitative evaluation of the solubility of uraninite (UO2) in aqueous solutions under hydrothermal conditions was made using previously reported thermodynamic data, so as to inquire into the controlling factors for Canadian unconformity-type ore mineralization as observed in the Athabasca uranium field. The results of solubility calculations suggest that uranyl carbonate complexes, such as UO2CO
3
o
, UO2(CO3)
2
2-
and UO2(CO3)
3
4-
, predominate under relatively oxidizing and slightly acidic-alkaline conditions and that the uranyl chloride complex, UO2Cl+ is dominant under acidic conditions. These features are predicted at temperatures up to 200 °C over reasonable ranges of CO2 pressure (Pco2) and salinity. Consequently, the physico-chemical parameters, such as oxygen activity (ao2), and pH are regarded as the most important factors controlling uraninite solubility. Judging from the paragenetic sequences observed in most unconformity-type uranium deposits in the Athabasca district, appreciable decreases in the above variables are postulated to have occurred in the stage of principal uranium deposition. Such changes would be due to fluid-mixing phenomenon accompanied by the diagenetic-hydrothermal activity (Hoeve and Quirt 1987). 相似文献
90.
Akira Ohtsuki Masanori Hirota Kikuo Ishimura Kazutomo Yokoyama Kiyoshi Fukutake 《地震工程与结构动力学》1992,21(7):591-607
The verification of a two-dimensional non-linear analysis based on a hybrid constitutive model, which consists of the Ramberg-Osgood model extended to two-dimensional problems and a dilatancy model, is discussed through a comparison of the shaking-table test results for a one-storey structure standing on a dry sandy deposit with those for the same on a saturated sandy deposit. Since the relationships G vs. γ and h vs. γ for shear strains of 10?5?10?3 can be obtained accurately by an inversion analysis of the resonance curve of the sandy deposit the proposed non-linear method can represent well the observed non-linear response of the dry or the saturated sandy deposit including the structure. This method, however, should be applied carefully to assess the response of a soil-structure system when the three-dimensional interaction affects significantly the response of the model. An equivalent linear analysis using a sway-rocking model is applied to simulate the non-linear ground motion including the three-dimensional interaction, and it is found that the sway-rocking model can also represent well the non-linear response of the system. 相似文献