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991.
992.
993.
Du Duc Tien Thanh Ngo-Duc Hoang Thi Mai Chanh Kieu 《Meteorology and Atmospheric Physics》2013,122(1-2):55-64
This study examines the dependence of the tropical cyclone (TC) intensity errors on the track errors in the Weather Research and Forecasting (WRF-ARW) model. By using the National Centers for Environmental Prediction global final analysis as the initial and boundary conditions for cloud-resolving simulations of TC cases that have small track errors, it is found that the 2- and 3-day intensity errors in the North Atlantic basin can be reduced to 15 and 19 % when the track errors decrease to 55 and 76 %, respectively, whereas the 1-day intensity error shows no significant reduction despite more than 30 % decrease of the 1-day track error. For the North-Western Pacific basin, the percentage of intensity reduction is somewhat similar with the 2- and 3-day intensity errors improved by about 15 and 19 %, respectively. This suggests that future improvement of the TC track forecast skill in the WRF-ARW model will be beneficial to the intensity forecast. However, the substantially smaller percentages of intensity improvement than those of the track error improvement indicate that ambient environment tends to play a less important role in determining the TC intensity as compared to other factors related to the vortex initialization or physics representations in the WRF-ARW model. 相似文献
994.
Impact of the snow cover scheme on snow distribution and energy budget modeling over the Tibetan Plateau 总被引:1,自引:0,他引:1
Zhipeng?Xie Zeyong?HuEmail author Zhenghui?Xie Binghao?Jia Genhou?Sun Yizhen?Du Haiqing?Song 《Theoretical and Applied Climatology》2018,131(3-4):951-965
This paper presents the impact of two snow cover schemes (NY07 and SL12) in the Community Land Model version 4.5 (CLM4.5) on the snow distribution and surface energy budget over the Tibetan Plateau. The simulated snow cover fraction (SCF), snow depth, and snow cover days were evaluated against in situ snow depth observations and a satellite-based snow cover product and snow depth dataset. The results show that the SL12 scheme, which considers snow accumulation and snowmelt processes separately, has a higher overall accuracy (81.8%) than the NY07 (75.8%). The newer scheme performs better in the prediction of overall accuracy compared with the NY07; however, SL12 yields a 15.1% underestimation rate while NY07 overestimated the SCF with a 15.2% overestimation rate. Both two schemes capture the distribution of the maximum snow depth well but show large positive biases in the average value through all periods (3.37, 3.15, and 1.48 cm for NY07; 3.91, 3.52, and 1.17 cm for SL12) and overestimate snow cover days compared with the satellite-based product and in situ observations. Higher altitudes show larger root-mean-square errors (RMSEs) in the simulations of snow depth and snow cover days during the snow-free period. Moreover, the surface energy flux estimations from the SL12 scheme are generally superior to the simulation from NY07 when evaluated against ground-based observations, in particular for net radiation and sensible heat flux. This study has great implications for further improvement of the subgrid-scale snow variations over the Tibetan Plateau. 相似文献
995.
996.
997.
We addressed the mesoscale structure variation of the central South China Sea (SCS) with the measurements by a long-lived
Argo float and a high-resolution ATLAS buoy during 1998–2002. T-S diagram indicates cooling and freshening events in 2000
and 2001 with lower salinity (0.5–0.8) and lower temperature (1–1.7°C). Significant decrease in the net heat flux and increase
in the precipitation suggest that the cooling and freshening is due to extra forcing by the atmosphere. Additional to large
year-to-year changes, intraseasonal variability is moderate in the research area. The axis of the maximum intraseasonal temperature
and salinity signals are mainly located on the thermocline. Typically, amplitude and period of intraseasonal temperature is
about 2°C and 40–60 days, and that of salinity is 0.3–0.5 and 35–60 days. Rapidly-changing winds, heat flux, and precipitation
are critical in controlling the intraseasonal fluctuations of the mixed layer of the area. Studies on heat and freshwater
balance in the mixed-layer further suggest that horizontal advection plays an important role in intraseasonal fluctuation
in the upper ocean. In addition, the energetic mesoscale propagation radiated from the east boundary is linked to the intraseasonal
variability in winter. 相似文献
998.
新疆西南天山蓝片岩-榴辉岩带是全球少有的几个经历超高压变质作用的洋壳俯冲带之一,近年来的同位素年代学研究表明其变质作用主要发生于石炭纪。然而,该蓝片岩-榴辉岩带峰期变质作用,特别是超高压变质作用的时代还未精确限定。本文选取来自该带的典型钠云母黝帘石榴辉岩(样品211-3和H76-10),在详细的岩石学和相平衡研究基础上,开展了Lu-Hf同位素年代学研究,以期获得其峰期变质作用时代。相平衡模拟结果表明两榴辉岩中石榴石均记录了升温降压型折返P-T(温度-压力)轨迹。其中,样品211-3经历了超高压变质作用,其压力峰期P-T条件为~540℃、~2.9GPa,石榴石-绿辉石-全岩Lu-Hf等时线年龄为326.9±1.3Ma;样品H76-10仅经历了高压变质作用,其压力峰期P-T条件为~490℃、~2.4GPa,石榴石-绿辉石-全岩Lu-Hf等时线年龄为306±11Ma。结合前人年代学数据,获得新疆西南天山超高压榴辉岩峰期变质作用时代为327~326Ma,高压榴辉岩峰期变质作用时代为316-306Ma。本文获得的超高压变质作用确切年龄326.9±1.3Ma,对于揭示古南天山洋深俯冲和闭合的时间具有重要意义。 相似文献
999.
近40年拉萨霜期变化的气候特征分析 总被引:10,自引:1,他引:10
采用气候统计学方法,对拉萨无霜期、初(终)霜日气候特征及其气候变化进行了分析。结果表明:无霜期的绝对变率要比初、终霜日的绝对变率大,终霜日推迟的概率比初霜日提早的概率大。1954~1988年总的趋势是初霜日提早、终霜日推迟、无霜期缩短;1989年后表现为无霜期延长、初霜日推迟、终霜日提早。 相似文献
1000.
A New Method to Determine Epochs of Solar Cycle Extrema 总被引:1,自引:0,他引:1
Zhan-Le Du Hua-Ning Wang Xiang-Tao He Department of Astronomy Beijing Normal University Beijing National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2006,6(3):338-344
A weighted average method is proposed to determine the epochs of solar cycle extrema and hence the solar cycle lengths. Comparing to the previous methods, this method has the advantage that the extremum epochs are easily and uniquely determined. 相似文献