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Sandra García-Bustos Jimmy Landín Ricardo Moreno A.S.E. Chong Maurizio Mulas Mónica Mite 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2020,14(1):56-68
ABSTRACTIn this work, we have studied the largest earthquake magnitudes on the Ecuadorian coast by using the principles of Extreme Value Analysis based on its two approaches: Block Maxima and Peaks-over-Threshold. First, before modelling the recorded earthquakes, the K-means clustering technique was applied to determine a classification according to the level of magnitude of the earthquakes. Then, models based on the Extreme Value theory of earthquake magnitudes were developed for each of the four clusters that were found, and finally, the best-fitted models were those known as Fréchet and Gumbel ones. The zone with the greatest earthquake magnitudes on the Ecuadorian coast is located between the north of the province of Manabí and the south of the province of Esmeraldas, with a return period of 50 years for an earthquake with magnitude greater than 7.7 MW. 相似文献
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The δ18O variations in an 80.36 m ice core retrieved in the accumulation zone of the East Rongbuk Glacier, Mount Qomolangma (Everest), is not consistent with changes of air temperature from both southern and northern slopes of Himalayas, as well as these of the temperature anomalies over the Northern Hemisphere. The negative relationship between the δ18O and the net accumulation records of the ice core suggests the "amount effect" of summer precipitation on the δ18O values in the region. Therefore, the δ18O records of the East Rongbuk ice core should be a proxy of Indian Summer Monsoon intensity, which shows lower δ18O values during strong monsoon phases and higher values during weak phases. 相似文献
115.
CHEN Hui ZHAO Dongsheng LU Xinmiao LI Yuecong XU Qinghai LI Shuangcheng OUYANG Hua 《地理学报》2006,16(4):439-446
Pollen analysis of 23 surface samples in the east of Qaidam Basin reveals the characteristics of pollen assemblages and their relationships with vegetation and climate. In pollen assemblages, Chenopodiaceae and Artemisia are preponderant types in all the samples, and Ephedra, Gramineae and Compositae are common types. The results of DCA (Detrended Correspondance Analysis) and Correlation Analysis show different pollen assemblages indicate different vegetations, coincided with respective vegetation types. A/C (Artemisia/Chenopodiaceae) in the desert can indicate the aridity. Depending on the aridity, the vegetation communities are divided into four groups: severe drought group, moderate drought group, slight drought group and tropophilous group. A/C value is less 0.2 in the severe drought group, 0.2–0.5 in the moderate drought group, 1.63 in the slight drought group and 5.72 slight-wetness group. 相似文献
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Philip A. Meyers 《Journal of Paleolimnology》2002,28(2):237-244
The amounts and types of carbon delivered to the sediments Seneca Lake, New York, have varied since the middle Holocene. Concentrations of CaCO3 first fluctuate between 14 and 6% around 7 ka before decreasing erratically until about 5 ka and then remain 2% in younger sediments. Because the amount of calcite that precipitates in hard-water lakes is related to summertime thermal stratification, the carbonate fluctuations suggest that cyclic strengthening and weakening of seasonality at intervals of about three centuries accompanied the end of the Holocene Hypsithermal in northeast North America. Organic C/total N values record short, decade-long intervals of enhanced delivery of land-plant material during episodes of wetter climate that are independent of the temperature variations. Higher organic 13C values indicate that recent fertilization of lake waters from soil disturbance and land-derived runoff has increased aquatic productivity. 相似文献
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彩色显示器呈色域的确定是彩色管理系统中实现颜色空间转换的前提。不考虑亮度因素Y而仅把在CIE1931色度图上连接R、G、B三原色点形成的三角形区域认为是彩色显示器的呈色域,尚不能全面地描述显示器的呈色域。如果考虑亮度因素Y,那么,在不同的呈色亮度下,其呈色域的形状与大小是不同的。本文就彩色显示器在不同呈色亮度下呈色域的确定问题进行实验研究,得出相应结论 相似文献
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本文介绍了1980.0年中国地磁正常场图的编绘和地磁正常场数学模式的建立使用不同年代观测的地磁三要素资料2000余个,经过通化改正,统统改正到1980.0这个特定年代。采用泰勒多项式和最小二乘法,分别建立1980.0年中国地磁正常场和地磁场长期变化数学模式,并计算其网格值,用于编绘1980.0年中国地磁正常场图。本文在建立地磁正常场数学模式时,采用三个独立的地磁要素建立模式的方法,解决了地磁场模式在地磁倾角为零的地方、而垂直强度不为零的问题。 相似文献
120.
本文以色度学理论为指导,根据地图设计与生产的实际需要,建构了一个用于地图颜色设计与分色的彩色管理系统。该系统通过数学模型完成对所含的七种颜色空间的相互交换,其中YMCK空间和HVC空间直接与输入输出设备(介质)的颜色特征相关。在这一研究中,作者提出了一种不区分网点扩大性质的数学模型,改进了CIEXYZ与MRGB空间的变换方法。 相似文献