全文获取类型
收费全文 | 36314篇 |
免费 | 482篇 |
国内免费 | 331篇 |
专业分类
测绘学 | 848篇 |
大气科学 | 2591篇 |
地球物理 | 7501篇 |
地质学 | 13232篇 |
海洋学 | 3160篇 |
天文学 | 7622篇 |
综合类 | 85篇 |
自然地理 | 2088篇 |
出版年
2021年 | 321篇 |
2020年 | 325篇 |
2019年 | 353篇 |
2018年 | 801篇 |
2017年 | 688篇 |
2016年 | 879篇 |
2015年 | 478篇 |
2014年 | 819篇 |
2013年 | 1749篇 |
2012年 | 941篇 |
2011年 | 1322篇 |
2010年 | 1168篇 |
2009年 | 1515篇 |
2008年 | 1369篇 |
2007年 | 1334篇 |
2006年 | 1286篇 |
2005年 | 1016篇 |
2004年 | 1029篇 |
2003年 | 969篇 |
2002年 | 966篇 |
2001年 | 811篇 |
2000年 | 826篇 |
1999年 | 719篇 |
1998年 | 714篇 |
1997年 | 717篇 |
1996年 | 559篇 |
1995年 | 578篇 |
1994年 | 547篇 |
1993年 | 503篇 |
1992年 | 445篇 |
1991年 | 418篇 |
1990年 | 465篇 |
1989年 | 359篇 |
1988年 | 408篇 |
1987年 | 465篇 |
1986年 | 397篇 |
1985年 | 576篇 |
1984年 | 609篇 |
1983年 | 624篇 |
1982年 | 495篇 |
1981年 | 492篇 |
1980年 | 521篇 |
1979年 | 457篇 |
1978年 | 474篇 |
1977年 | 419篇 |
1976年 | 430篇 |
1975年 | 399篇 |
1974年 | 444篇 |
1973年 | 422篇 |
1972年 | 275篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
FluBiDi is a two-dimensional model created to simulate real events that can take days and months, as well as short events (minutes or hours) and inclusive laboratory tests. To verify the robustness of FluBiDi, it was tested using a previous study with both designed and real digital elevation models. The results highlight good agreement between the models (i.e. Mike Flood, SOBEK, ISIS 2D, and others) tested and FluBiDi (around 90% for a specific instant and 95% for the complete time simulation). In the simulated hydrographs, the discharge peak value, time to peak, and water level results were accurate, reproducing them with an error of less than 5%. The velocity differences observed in a couple of tests in FluBiDi were associated with very short periods of time (seconds). However, FluBiDi is highly accurate for simulating floods under real topographical conditions with differences of around 2 cm when water depth is around 150 cm. The average water depth and velocities are precise, and the model describes with high accuracy the pattern and extent of floods. FluBiDi has the capability to be adjusted to different types of events and only requires limited input data. 相似文献
72.
P. Rodríguez-Gil B. T. Gänsicke H.-J. Hagen S. Araujo-Betancor A. Aungwerojwit C. Allende Prieto D. Boyd J. Casares D. Engels O. Giannakis E. T. Harlaftis J. Kube H. Lehto I. G. Martínez-Pais R. Schwarz W. Skidmore A. Staude M. A. P. Torres 《Monthly notices of the Royal Astronomical Society》2007,377(4):1747-1762
73.
Elementary cluster analysis of induced seismicity in a South African gold mine has shown that there is a clear interaction amongst the clusters; and that the level of the interaction is a function of the distance. The clusering algorithm used is an adaptation of the single-link cluster analysis which considers both three-dimensional space and time. A high level of interaction between the clusters is demonstrated from the cross-correlation analysis of seismic activity rates and radiated energy. A distinct decrease in the value of correlation coefficients was detectable as distance increased. This was somewhat surprising, considering the simplicity of the technique used. Since no attempt is made to study the physical mechanisms of interaction, these results are very preliminary, but interesting from an observational point of view. 相似文献
74.
Robert W. Luth 《Contributions to Mineralogy and Petrology》1995,122(1-2):152-158
The carbonation reaction CaMg(CO3)2 (dolomite)+2SiO2 (coesite)=CaMgSi2O6 (diopside)+2 CO2 (vapor) has been determined experimentally between 3.5 and 6 GPa in a multiple-anvil, solid-media apparatus. This reaction,
a candidate for carbonation of eclogites (garnet+clinopyroxene) in the Earth’s mantle, lies at higher pressure for a given
temperature than do the carbonation reactions for peridotites (olivine+orthopyroxene±clinopyroxene). A depth interval may
exist within the Earth’s mantle under either ‘normal’ or ‘subduction’ thermal regimes where carbonated peridotite could coexist
with carbonate-free, CO2-bearing eclogite.
Received: 25 May 1994/Accepted: 13 June 1995 相似文献
75.
76.
O. V. Ilyina N. S. Tychkov A. M. Agashev A. V. Golovin A. E. Izokh O. A. Kozmenko N. P. Pokhilenko 《Doklady Earth Sciences》2016,467(2):408-411
The results of the first study of the PGE distribution in deformed lherzolites of the Udachnaya kimberlite pipe (Yakutia) are presented here. The complex character of evolution of the PGE composition in the Deformed lherzolites is assumed to be the result of silicate metasomatism. At the first stage, growth in the amount of clinopyroxene and garnet in the rock is accompanied by a decrease in the concentration of the compatible PGE (Os, Ir). During the final stage, the rock is enriched with incompatible PGE (Pt, Pd) and Re possible due to precipitation of submicron-sized particles of sulfides in the interstitial space of these mantle rocks. 相似文献
77.
M.?B.?BellEmail author L.?W.?Avery J.?M.?MacLeod J.?P.?Vallée 《Astrophysics and Space Science》2011,333(2):377-388
Sensitive spectral observations made in two frequency bands near 6.0 and 17.6 GHz are described for Orion and W51. Using frequency
switching we were able to achieve a dynamic range in excess of 10,000 without fitting sinusoidal or polynomial baselines.
This enabled us to detect lines as weak as T
A
∼1 mK in these strong continuum sources. Hydrogen recombination lines with Δn as high as 25 have been detected in Orion. In the Orion data, where the lines are stronger, we have also detected a systematic
shift in the line center frequencies proportional to linewidth that cannot be explained by normal optical depth effects. 相似文献
78.
79.
Robert O. Fournier Robert J. Rosenbauer James L. Bischoff 《Geochimica et cosmochimica acta》1982,46(10):1975-1978
The solubility of quartz in 2, 3, and 4 molal NaCl was measured at 350°C and pressures ranging from 180 to 500 bars. The molal solubility in each of the salt solutions is greater than that in pure water throughout the measured pressure range, with the ratio of solubility in NaCl solution to solubility in pure water decreasing as pressure is increased. The measured solubilities are significantly higher than solubilities calculated using a simple model in which the water activity in NaCl solutions decreases either in proportion to decreasing vapor pressure of the solution as salinity is increased or in proportion to decreasing mole fraction of water in the solvent. 相似文献
80.