全文获取类型
收费全文 | 125篇 |
免费 | 8篇 |
国内免费 | 6篇 |
专业分类
大气科学 | 7篇 |
地球物理 | 42篇 |
地质学 | 55篇 |
海洋学 | 9篇 |
天文学 | 15篇 |
自然地理 | 11篇 |
出版年
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 3篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 6篇 |
2012年 | 4篇 |
2011年 | 9篇 |
2010年 | 12篇 |
2009年 | 6篇 |
2008年 | 6篇 |
2007年 | 6篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 8篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1980年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有139条查询结果,搜索用时 15 毫秒
101.
Titanochondrodite and titanoclinohumite derived from the upper mantle in the Buell Park Kimberlite,Arizona, USA 总被引:2,自引:0,他引:2
Ken-ichiro Aoki Kiyoshi Fujino Masaki Akaogi 《Contributions to Mineralogy and Petrology》1976,56(3):243-253
Kimberlite from Buell Park, Arizona, which was intruded into Permian sediments about 30 m.y. ago, is characterized by the hydrous silicates titanochondrodite and titanoclinohumite. Titanochondrodite is the first finding in kimberlites. Optical properties, chemical compositions and cell dimensions of these two minerals are determined.Titanochondrodite and titanoclinohumite are considered to crystallize from kimberlite magma at a depth of about 100 km and at 1,000° C, on the basis of kimberlite mineralogy, petrography and high pressure experimental work. Although there is no direct evidence, the importance of these two minerals in peridotite wedges above sinking lithosphere at the continental margins is also discussed. 相似文献
102.
103.
A tuned liquid damper (TLD), which consists of rigid tanks partially filled by liquid, is a type of passive control device relying upon liquid sloshing forces or moments to change the dynamical properties and to dissipate vibrational energy of a structure. An analytical non-linear model is proposed for a TLD using rectangular tanks filled with shallow liquid under pitching vibration, utilizing a shallow water wave theory. The model includes the linear damping of the sloshing liquid, which is an important parameter in the study of a TLD as it affects the efficiency of the TLD. Shaking table experiments were conducted for verification; good agreement between the analytical simulations and the experimental results was observed in a small excitation amplitude range. The simulations of TLD-structure interaction by using the proposed model show that the TLD can efficiently suppress resonant pitching vibration of a structure. It is also found that the effectiveness of a TLD for suppressing the pitching vibration depends not only on the mass of liquid in the TLD but also on the configuration of the liquid as well as upon the position where the TLD is located. If the configuration of the liquid, i.e. the liquid depth and the TLD tank size, is designed suitably, the TLD can have a large suppressing moment and can be very effective even with a small mass of liquid. 相似文献
104.
John Kuo Ziyusei Kanamoto Hitoshi Iizumi Keiko Aioi & Hiroshi Mukai 《Marine Ecology》2006,27(4):290-298
The Nansei Islands in the southern Japanese Archipelago have 15 taxa of seagrasses from seven genera within three families. Seagrasses in this region grow on coral sands or coral debris in shallow reefs and on sandy or muddy substrata in the shallow areas of bays and inlets. Certain Halophila species grow in deep water off some islands. Enhalus acoroides only reaches to Ishigaki I. with winter sea water temperature (WST) at 23 °C, while Okinawa I. (WST at 21.6 °C) is the northern biogeographic limit for Halophila decipiens, H. okinawensis, H. major and H. gaudichaudii. Amami‐oshima I. (WST at 20.7 °C) is the northern border for Thalassia hemprichii, H. minor, H. ovalis, Cymodocea serrulata, Cymodocea rotundata, Syringodium isoetifolium, Halodule uninervis and Halodule pinifolia. Halophila mikii the sole seagrass collected from Yakushima I. (WST at 19.3 °C), is of volcanic origin. The distribution of tropical seagrasses in the Nansei Islands is clearly associated with the warm Kuroshio Current, WST and habitat availability. Zostera japonica is the only temperate species occurring in the region. Meadows of Z. japonica, H. ovalis and Halodule pinifolia have disappeared from certain localities in the Archipelago, due probably to human activities and natural siltation. 相似文献
105.
Spatial and Temporal Variability of Satellite Primary Production in the Japan Sea from 1998 to 2002 总被引:1,自引:0,他引:1
The spatial and seasonal variability of primary production in the Japan Sea from 1998 to 2002 was estimated using a satellite
primary production model. A size-fractionated primary production model was validated by in situ primary production data measured in the Japan Sea. Estimated primary production and in situ primary production showed a good positive correlation. Estimated primary production showed spatial variability. Annual primary
production levels were 170, 161, 191 and 222 gC m−2year−1 at the Russian coast, in the middle of the Japan Basin, the southeastern area and the southwestern area, respectively. It
was higher to the south around 40°N than to the north, and higher in the western area than in the eastern one. Peaks of primary
production appeared twice, in spring and fall, in the southern area, while a single peak appeared in the northern area. Primary
production along the Russian coast was higher than in other areas during summer. The spring bloom contributed 42% to the annual
primary production in these four areas. Furthermore, estimated primary production showed an interannual variability that was
largest in spring. Primary production in fall also showed interannual variability, especially in the middle of the Japan Basin
and the southwestern area. This corresponded mainly to the size of the phytoplankton bloom in each year. Winter convection
by wind and the depth of nutrient-rich, cold subsurface water underlying the Tsushima Current may contribute to the nutrient
supply to upper layer and interannual variations of primary production in spring. 相似文献
106.
Subduction of mantle wedge peridotites: Evidence from the Higashi-akaishi ultramafic body in the Sanbagawa metamorphic belt 总被引:1,自引:0,他引:1
The Higashi-akaishi garnet-bearing ultramafic body in the Sanbagawa metamorphic belt, Southwest Japan, represents a rare example of oceanic-type ultrahigh-pressure metamorphism. The body of 2 km × 5 km is composed mostly of anhydrous dunite with volumetrically minor lenses of clinopyroxene-rich rocks. Dunite samples contain high Ir-type platinum group elements (PGE) and Cr in bulk rocks, high Mg and Ni in olivine, and high Cr in spinel. On the other hand, clinopyroxene-rich rocks contain low concentrations of Ir-type PGE and Cr, high concentrations of fluid-mobile elements in bulk rocks, and low Ni and Mg in olivine. Clinopyroxene is diopsidic with low Al2 O3 . The compositions of bulk rocks and mineral chemistry of spinel, olivine, and clinopyroxene suggest that the olivine-dominated rocks are residual mantle peridotites after high degrees of influx partial melting, and that the clinopyroxene-rich rocks are cumulates of subduction-related melts. Thus, the Higashi-akaishi ultramafic body originated from the interior of the mantle wedge, most likely the forearc upper mantle. It was then incorporated into the Sanbagawa subduction channel by a mantle flow, and underwent high pressure metamorphism to a depth greater than 100 km. Such a strong active flow in the mantle wedge is likely facilitated by the lack of serpentinites along the interface between the slab and the overlying mantle, as it was too hot for serpentine. These unusually hot conditions and strong active mantle flow may reflect conditions in the earliest stage of development of subduction, and may have been maintained by massive upwelling and subsequent eastward flow of asthenospheric mantle in the northeastern Asian continent in Cretaceous time when the Sanbagawa belt began to form. 相似文献
107.
吉林东部汪清新生代玄武岩中地幔包体的矿物化学:对该地区岩石圈地幔形成过程的启示 总被引:1,自引:0,他引:1
在对吉林汪清新生代玄武岩中橄榄岩包体进行全岩主、微量元素分析的基础上,重点分析了矿物的主、微量元素含量,讨论了华北克拉通东北缘与兴蒙造山带结合部位陆下岩石圈地幔所经历的部分熔融作用和地幔交代作用。橄榄石的Fo、单斜辉石以及尖晶石的Mg#和Cr#均表明该地区陆下岩石圈地幔相对饱满。对地幔橄榄岩透辉石微量元素模拟计算证实,汪清陆下岩石圈地幔经历了1%~3%的部分熔融作用,并遭受后期硅酸盐熔体交代作用。这些地幔特征与中国东部其他地区新生代主体岩石圈相似。研究结果证明,吉林汪清中、新生代以来岩石圈性质的转变是在汇聚板块构造体制下通过“拆沉作用”实现的。 相似文献
108.
Plastic deformation of garnets: systematics and implications for the rheology of the mantle transition zone 总被引:14,自引:0,他引:14
Shun-ichiro Karato Zichao Wang Bofa Liu Kiyoshi Fujino 《Earth and Planetary Science Letters》1995,130(1-4):13-30
Plastic properties of materials with garnet structure have been studied under wide temperature conditions, ranging from room temperature to 95% of the melting temperatures, using uniaxial compression and hot microhardness tests. Garnets studied include single crystals of oxide garnets (Y3Al5O12, Gd3Ga5O12 and Y3Fe5O12) and silicate garnets (various solid solutions, including grossular, almandine, andradite, pyrope, spessartine and uvarovite). Both uniaxial compression and hot hardness tests indicate that there is a general trend in the plasticity of garnets when the data are compared at normalized conditions (T/Tm andσ/μ), and that the resistance to plastic deformation in garnets is significantly higher than most of the other minerals in the Earth's mantle. Based on both stress-dip tests and microstructural observations, it is proposed that the creep strength of garnet is largely controlled by the resistance to dislocation glide rather than by recovery processes. This conclusion is consistent with the high Peierls stress inferred from the hot hardness tests. The high Peierls stress in garnets is, presumably, due to the large unit cell (i.e., long Burgers vectors) and/or the bcc packing, which are common to all garnets. We postulate, therefore, that the present results can be applied to the strength of high-pressure garnet (majorite) and suggest that garnet-rich layers in the Earth, such as subducted oceanic crust in the transition zone or a possibly garnet-rich (bottom part of the) transition zone, will be considerably stronger than surrounding regions. 相似文献
109.
Derek D. Stretch James W. Rottman S.Karan Venayagamoorthy Keiko K. Nomura Chris R. Rehmann 《Dynamics of Atmospheres and Oceans》2010
Mixing efficiency in stratified flows is a measure of the proportion of turbulent kinetic energy that goes into increasing the potential energy of the fluid by irreversible mixing. In this research direct numerical simulations (DNS) and rapid distortion theory (RDT) calculations of transient turbulent mixing events are carried out in order to study this aspect of mixing. In particular, DNS and RDT of decaying, homogeneous, stably-stratified turbulence are used to determine the mixing efficiency as a function of the initial turbulence Richardson number Rit0=(NL0/u0)2, where N is the buoyancy frequency and L0 and u0 are initial length and velocity scales of the turbulence. The results show that the mixing efficiency increases with increasing Rit0 for small Rit0, but for larger Rit0 the mixing efficiency becomes approximately constant. These results are compared with data from towed grid experiments. There is qualitative agreement between the DNS results and the available experimental data, but significant quantitative discrepancies. The grid turbulence experiments suggest a maximum mixing efficiency (at large Rit0) of about 6%, while the DNS and RDT results give about 30%. We consider two possible reasons for this discrepancy: Prandtl number effects and non-matching initial conditions. We conclude that the main source of the disagreement probably is due to inaccuracy in determining the initial turbulence energy input in the case of the grid turbulence experiments. 相似文献
110.
Multiple Tuned Mass Dampers (MTMD) consist of a large number of small oscillators with natural frequencies distributed around the natural frequency of a controlled mode of the structure. In the present paper, the modal characteristics and efficiency of the MTMD are studied analytically. Perturbation solutions for the modal properties of the MTMD–structure system are obtained and the modal characteristics are discussed. An explicit formula to estimate the effectiveness of the MTMD subjected to harmonic forces is also derived. It is shown that the MTMD is efficient when at least one of the oscillators is strongly coupled with the structure in any mode. Based on this observation, a critical bandwidth of the natural frequencies of the MTMD to make the system multiply tuned is derived in a simple form, and furthermore a robustness criterion for the frequency tuning under a given bandwidth is proposed. It is shown that, when properly designed, the MTMD can be much more stable (robust) than a conventional single TMD while maintaining more or less the same efficiency. Numerical studies verify the accuracy of the perturbation solutions and the proposed formulas. 相似文献