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901.
Post-earthquake investigation on several geosynthetic-reinforced soil retaining walls and slopes during the Ji-Ji earthquake of Taiwan 总被引:1,自引:0,他引:1
Hoe I. Ling Dov Leshchinsky Nelson N. S. Chou 《Soil Dynamics and Earthquake Engineering》2001,21(4):3087
This paper gives an overview on the application of geosynthetic-reinforced soil structures in Taiwan. Taiwan has an unique topography and geotechnical conditions that rendered a less conservative and more challenging design compared to that of North America, Europe and Japan. The Ji-Ji (Chi-Chi) earthquake of 1999 gave an opportunity to examine the behavior of reinforced soil structures. The performance of several modular-block reinforced soil retaining walls and reinforced slopes at the vicinity of the fault was evaluated. Reinforced structures performed better than unreinforced soil retaining walls. The failure cases were highlighted and the cause of failure was identified. The lack of seismic design consideration could be a major cause of failure. The compound failure mode, the inertia force of the blocks, and the connection stiffness and strength relative to the large dynamic earth pressure, were among major items that would warrant further design consideration. 相似文献
902.
The effectiveness of tuned mass dampers (TMD) in vibration control of buildings was investigated under moderate ground shaking caused by long‐distance earthquakes with frequency contents resembling the 1985 Mexico City (SCT) or the 1995 Bangkok ground motion. The elastic–perfectly plastic material behaviour was assumed for the main structure, with linear TMDs employed by virtue of their simplicity and robustness. The accumulated hysteretic energy dissipation affected by TMD was examined, and the ratio of the hysteretic energy absorption in the structure with TMD to that without it is proposed to be used, in conjunction with the peak displacement ratio, as a supplementary TMD performance index since it gives an indication of the accumulated damage induced in the inelastic structures. For the ground motions considered, TMD would be effective in reducing the hysteretic energy absorption demand in the critical storeys for buildings in the 1.8–2.8 s range. The consequence is reduction in damage of the buildings which would otherwise suffer heavy damage in the absence of TMD, resulting in economical restorability in the damage control limit state. This is of practical significance in view of the current trend toward performance‐based design. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
903.
A. D. Shukla N. Bhandari Sheela Kusumgar P. N. Shukla Z. G. Ghevariya K. Gopalan V. Balaram 《Journal of Earth System Science》2001,110(2):111-132
Chemical analysis of nine Deccan flow basalts at Anjar, Kutch, western India, indicates that all, except the uppermost flow
F-9, are alkaline. In their major and trace element composition, the alkali basalts resemble Ocean island basalts (OIB). Similarities
of many diagnostic trace element ratios (e.g. Sm/Nd, Ba/Nb,Y/Nb and Zr/Nb) are similar to those found in the Réunion Island
basalts. The uppermost basalt is tholeiitic and chemically resembles the least contaminated Deccan basalt (Ambenali type).
The Anjar basalts have iridium concentration ranging between 2 and 178 pg/g. Some of these values are higher by about an order
of magnitude compared to the Ir concentration in other basalts of the Deccan. A synthesis of chemical, palaeomagnetic and
geochronologic data enables us to construct a chemical and magnetic stratigraphy for these flows.
The three flows below the iridium enriched intertrappean bed (IT III) show normal magnetic polarity whereas all except one
of the upper basalts show reversed magnetic polarity. The sequence seems to have started in polarity zones 31N and probably
continued up to 28R or 27R. The results presented here support the view that Deccan volcanism in Kutch occurred on a time
span of a few million years. 相似文献
904.
Cross-border communication and co-operation at the Eastern fringe of the European Union seems so far to have been a matter
of political initiative and a lot of good will at the levels of national, regional and local governance. This article maintains
that everyday culture must be given more notice when cross-border activities are regarded at the local level, especially in
twin cities. The case of the German-Polish twin city Guben/Gubin reveals a strong tendency towards a new divergence of thought
and action between formal and informal levels of action, namely the level of local politics and governance and the level of
local everyday milieux. While the politics of Euroregions, local administrations and local governments is very often directed
towards establishing symbolic gestures of border-crossing and mutual understanding, social milieux at the ‘base’ of local
societies are rather driven by a paradoxical mixture of hope, anxiety, resentments and prejudice, thus producing contradictions
and even conflict with official political initiative.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
905.
Modeling of dioctahedral 2:1 phyllosilicates by means of transferable empirical potentials 总被引:1,自引:0,他引:1
C. I. Sainz-Diaz A. Hernández-Laguna M. T. Dove 《Physics and Chemistry of Minerals》2001,28(2):130-141
Dioctahedral 2:1 phyllosilicates with different interlayer charge have been studied theoretically by using transferable empirical
interatomic potentials. The crystal structures of pyrophyllite, muscovite, margarite, beidellite, montmorillonite, and different
smectites and illites have been simulated. The interatomic potentials were able to reproduce the experimental structure of
phyllosilicates with high, medium and low interlayer charge. The calculated structures are in agreement with experiment for
the main structural features of the crystal lattice. The effect of the cation substitution in the octahedral and tetrahedral
sheets on the structural features has been also studied. Good linear relationships have been found, and the calculated effects
are consistent with experimental results. Some unknown structural features of the crystal structures of clays are predicted
in this work.
Received: 8 March 2000 / Accepted: 19 September 2000 相似文献
906.
Analytical expressions are derived for the Poisson's ratios associated with a three-dimensional network of regular, corner-sharing
tetrahedra in which: (1) the tetrahedra are assumed to be rigid and free to rotate relative to each other; (2) the tetrahedra
are assumed to maintain shape and orientation but are free to change size (dilate); (3) tetrahedral rotation and dilation
are assumed to act concurrently. The structure has a primitive unit cell containing four tetrahedra and is analogous to the
molecular structure of α-cristobalite. Strain-dependent variations in Poisson's ratio are also predicted by the models. For
deformation due to tetrahedral rotation the network is found to exhibit negative Poisson's ratios in each of the three principal
directions, with the magnitude of the Poisson's ratio being dependent on the angle of rotation of the tetrahedra. The behaviour
of the Poisson's ratio is isotropic in the transverse plane, but anisotropic elsewhere. In the dilation model negative Poisson's
ratios equal to −1 are observed for uniaxial loading in any of the principal directions, with the value being constant irrespective
of tetrahedral size. The model for concurrent tetrahedral rotation and dilation allows positive as well as negative Poisson's
ratios, with the values determined by the framework geometry and relative strengths of the two mechanisms. The concurrent
model also offers a design route to materials and structures having ultrahigh Young's moduli.
Received: 15 February 2000 / Accepted: 1 October 2000 相似文献
907.
甘肃南金山金矿床的~(40)Ar-~(39)Ar同位素年龄及其地质意义 总被引:2,自引:0,他引:2
南金山金矿是我国西北地区最重要的金矿床之一 ,矿床产于下石炭统白山组浅变质海相火山碎屑岩中。本文通过对金矿床中的蚀变绢云母进行了40 Ar 3 9Ar同位素年龄测定 ,获得了两组数据 ,分别为 2 5 0 .6±2 .8Ma和 2 32 .7± 4.1Ma ,说明南金山金矿的形成经历了两期成矿作用。 相似文献
908.
Agricultural practices, hydrology, and water quality of the 267-km2 Big Spring groundwater drainage basin in Clayton County, Iowa, have been monitored since 1981. Land use is agricultural; nitrate-nitrogen
(-N) and herbicides are the resulting contaminants in groundwater and surface water. Ordovician Galena Group carbonate rocks
comprise the main aquifer in the basin. Recharge to this karstic aquifer is by infiltration, augmented by sinkhole-captured
runoff. Groundwater is discharged at Big Spring, where quantity and quality of the discharge are monitored.
Monitoring has shown a threefold increase in groundwater nitrate-N concentrations from the 1960s to the early 1980s. The nitrate-N
discharged from the basin typically is equivalent to over one-third of the nitrogen fertilizer applied, with larger losses
during wetter years. Atrazine is present in groundwater all year; however, contaminant concentrations in the groundwater respond
directly to recharge events, and unique chemical signatures of infiltration versus runoff recharge are detectable in the discharge
from Big Spring.
Education and demonstration efforts have reduced nitrogen fertilizer application rates by one-third since 1981. Relating declines
in nitrate and pesticide concentrations to inputs of nitrogen fertilizer and pesticides at Big Spring is problematic. Annual
recharge has varied five-fold during monitoring, overshadowing any water-quality improvements resulting from incrementally
decreased inputs.
Electronic Publication 相似文献
909.
P. N. Shukla N. Bhandari Anirban Das A. D. Shukla J. S. Ray 《Journal of Earth System Science》2001,110(2):103-110
We report here an unusually high concentration of iridium in some alkali basalts and alkaline rocks of Deccan region having
an age of about 65Ma, similar to the age of the Cretaceous-Tertiary boundary. The alkali basalts of Anjar, in the western
periphery of Deccan province, have iridium concentration as high as 178pg/g whereas the alkaline rocks and basalts associated
with the Amba Dongar carbonatite complex have concentrations ranging between 8 and 80 pg/g. Some of these values are more
than an order of magnitude higher than the concentration in the tholeiitic basalts of Deccan, indicating the significance
of alkaline magmatism in the iridium inventory at the Cretaceous-Tertiary boundary. Despite higher concentration, their contribution
to the global inventory of iridium in the Cretaceous-Tertiary boundary clays remains small. The concentration of iridium in
fluorites from Amba Dongar was found to be <30 pg/g indicating that iridium is not incorporated during their formation in
hydrothermal activity. 相似文献
910.
Jake Hancock 《Cretaceous Research》2001,22(6):677
The Aptian/Albian boundary, as currently placed, presents problems which have not yet been solved and possibly never will be. No detailed definition of recent years can be applied on a world-wide scale, which will be needed for any definition acceptable to the Subcommission on Cretaceous Stratigraphy. The only satisfactory and workable solution is to choose a completely new position. It is suggested that this should be at the base of the Zone of Lyelliceras lyelli. This would change the start of the Albian from appproximately 112 Ma to 109 Ma but it would be a standard which should be recognizable on all five continents. 相似文献