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931.
R. Errmann R. Neuhuser L. Marschall G. Torres M. Mugrauer W.P. Chen S.C.‐L. Hu C. Briceno R. Chini . Bukowiecki D.P. Dimitrov D. Kjurkchieva E.L.N. Jensen D.H. Cohen Z.‐Y. Wu T. Pribulla M. Vako V. Krushevska J. Budaj Y. Oasa A.K. Pandey M. Fernandez A. Kellerer C. Marka 《Astronomische Nachrichten》2013,334(7):673-681
With an apparent cluster diameter of 1.5° and an age of 4 Myr, Trumpler 37 is an ideal target for photometric monitoring of young stars as well as for the search of planetary transits, eclipsing binaries and other sources of variability. The YETI consortium has monitored Trumpler 37 throughout 2010 and 2011 to obtain a comprehensive view of variable phenomena in this region. In this first paper we present the cluster properties and membership determination as derived from an extensive investigation of the literature. We also compared the coordinate list to some YETI images. For 1872 stars we found literature data. Among them 774 have high probability of being member and 125 a medium probability. Based on infrared data we re‐calculate a cluster extinction of 0.9–1.2 mag. We can confirm the age and distance to be 3–5 Myr and870 pc. Stellar masses are determined from theoretical models and the mass function is fitted with a power‐law index of α = 1.90 (0.1–0.4 M⊙) and α = 1.12 (1–10 M⊙). (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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AbstractThe actual evapotranspiration and runoff trends of five major basins in China from 1956 to 2000 are investigated by combining the Budyko hypothesis and a stochastic soil moisture model. Based on the equations of Choudhury and Porporato, the actual evapotranspiration trends and the runoff trends are attributed to changes in precipitation, potential evapotranspiration, rainfall depth and water storage capacity which depends on the soil water holding capacity and the root depth. It was found that the rainfall depth increased significantly in China during the past 50 years, especially in southern basins. Contributions from changes in the water storage capacity were significant in basins where land surface characteristics have changed substantially due to human activities. It was also observed that the actual evapotranspiration trends are more sensitive to precipitation trends in water-limited basins, but more sensitive to potential evapotranspiration trends in energy-limited basins.
Editor D. Koutsoyiannis; Associate editor A. Porporato 相似文献
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936.
以天津港北港池码头地区海相沉积软土为研究对象,自行研制了与CT配套的单轴固结装置,取不同深度的土样分别进行单轴固结实验。逐级加载土样固结后,对土样进行CT扫描,结合CT图像分析软土固结过程中特性变化。研究表明:随着压力的增加,CT图像灰度平均值逐渐增大,说明土样被压实,密度增大;固结过程中,不同种类土样的CT图像标准差变化存在差异性,这与孔隙水压力消散引起土样内部结构的变化有关;引入CT图像灰度压缩系数来反映土样的压缩性能,研究结果表明天津港北港池码头软土具有较高的压缩性。 相似文献
937.
Dan Zhang Xiaomang Liu Haoyuan Hong 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(8):1871-1881
Reference evapotranspiration (ET 0 ) is a key parameter in hydrological and meteorological studies. In this study, the FAO Penman–Monteith equation was used to estimate ET 0 , and the change in ET 0 was investigated in China from 1960 to 2011. The results show that a change point around the year 1993 was detected for the annual ET 0 series by the Cramer’s test. For the national average, annual ET 0 decreased significantly (P < 0.001) by ?14.35 mm/decade from 1960 to 1992, while ET 0 increased significantly (P < 0.05) by 22.40 mm/decade from 1993 to 2011. A differential equation method was used to attribute the change in ET 0 to climate variables. The attribution results indicate that ET 0 was most sensitive to change in vapor pressure, followed by solar radiation, air temperature and wind speed. However, the effective impact of change in climate variable on ET 0 was the product of the sensitivity and the change rate of climate variable. During 1960–1992, the decrease in solar radiation was the main reason of the decrease in ET 0 in humid region, while decrease in wind speed was the dominant factor of decreases in ET 0 in arid region and semi-arid/semi-humid region of China. Decrease in solar radiation and/or wind speed offset the effect of increasing air temperature on ET 0 , and together led to the decrease in ET 0 from 1960 to 1992. Since 1993, the rapidly increasing air temperature was the dominant factor to the change in ET 0 in all the three regions of China, which led to the increase in ET 0 . Furthermore, the future change in ET 0 was calculated under IPCC SRES A1B and B1 scenarios with projections from three GCMs. The results showed that increasing air temperature would dominate the change in ET 0 and ET 0 would increase by 2.13–10.77, 4.42–16.21 and 8.67–21.27 % during 2020s, 2050s and 2080s compared with the average annual ET 0 during 1960–1990, respectively. The increases in ET 0 would lead to the increase in agriculture water consumption in the 21st century and may aggravate the water shortage in China. 相似文献
938.
Rae Glacier is a small cirque glacier located in the front ranges of the Canadian Rocky Mountains. In 1990 and 1991 field research was completed to describe the physical glaciology of Rae Glacier and to characterize historical glaciological trends at the site. Ablation and surface movement rates were measured using a network of stakes drilled into the glacier and radio-echo sounding was used to describe local ice depths. Rae Glacier has experienced a significant loss in size and mass during the historical period, owing to a lengthy interval of negative mass-balance conditions. The glacier has decreased in surface area by over 50% and now contains less than 24% of the ice it did at the end of the last century. Surface-ice velocity varied between 1.4 and 5.4 m from 1990 to 1991. Rates of ice ablation proved to be highly variable, with steeper areas showing up to 50% more ablation. Combined with data on the emergent flow component of the glacier, the ablation data suggest that the glacier presently is unable to replenish the amount of ice annually being lost to ablation. The glacier has a lag time of 5 to 10 years, which confirms that it is sensitive to climatic fluctuations and responds to changes in mass balance within a very short time. This observation is supported by an estimated response time of 42 years. [Key words: glaciology, Rae Glacier, Canadian Rocky Mountains.] 相似文献
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