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131.
三频观测值为导航定位提供了更多的观测值组合选择。在利用载波相位三频线性组合消除一阶电离层误差的基础上,对组合模糊度为实数和整数两种情况下的二阶电离层误差及观测噪声水平进行了分析,获得了几种适用于精密单点定位的三频观测值组合。 相似文献
132.
We examined the anthropogenic and natural causes of flood risks in six representative cities in the Gangwon Province of Korea.
Flood damage per capita is mostly explained by cumulative upper 5% summer precipitation amount and the year. The increasing
flood damage is also associated with deforestation in upstream areas and intensive land use in lowlands. Human encroachment
on floodplains made these urban communities more vulnerable to floods. Without changes in the current flood management systems
of these cities, their vulnerability to flood risks will remain and may even increase under changing climate conditions. 相似文献
133.
A data collection and process system is developed for RDT-10000 Type Rock Dynamic Triaxial Machine with High pressure, this system is supported by several subroutines in 6502 assembly language, which is of high-speed, flexibility, multi-functions. 相似文献
134.
In Taiwan many reservoirs are constructed in mountain areas. Unfortunately, several earthquakes shook the soil, and typhoons brought a huge amount of water to the reservoir zone. In the past studies, remote-sensing image data were used to effectively monitor the landslide near reservoirs. In recent years, linear discriminant analysis (LDA) has become a well-known method for image classification. However, there are few studies to optimize the linear classification function. While the ancillary information has been adopted easily by new methodologies, the ancillary information must be examined by a landslide image classification system. To explore the effects of optimization on the LDA equations, three approaches were compared: (a) conventional LDA; (b) combined discrete rough sets and LDA (DRS + LDA), which identify the core factors and the corresponding thresholds of landslide occurrence; and (c) combined particle swam optimization algorithm and LDA (PSO + LDA), which optimizes the parameters of LDA equation to attain the best classification outcomes. The above methods were applied to a reservoir region in Taiwan, and the following classification results were obtained. The application of DRS + LDA in our case study reduced the number of ancillary attributes from 14 to 5, and resulted in an accuracy rate of 0.83. On the other hand, the application of PSO + LDA resulted in the same accuracy rate as that of DRS + LDA, whereas the accuracy rate of conventional LDA was found to be 0.78. 相似文献
135.
Xiao Yang Wang Yang Wang Shun Evans T. Matthew Stuedlein Armin W. Chu Jian Zhao Chang Wu Huanran Liu Hanlong 《Acta Geotechnica》2021,16(5):1417-1427
Acta Geotechnica - Microbially induced carbonate precipitation (MICP) has been actively investigated as a promising method to improve soil properties. A burning issue impeding its wide application... 相似文献
136.
A series of laboratory experiments are performed under various hydrological conditions to analyze the effect of pools in pipes on breakthrough curves (BTCs). The BTCs are generated after instantaneous injections of NaCl tracer solution. In order to test the feasibility of reproducing the BTCs and obtain transport parameters, three modeling approaches have been applied: the equilibrium model, the linear graphical method and the two-region nonequilibrium model. The investigation results show that pools induce tailing of the BTCs, and the shapes of BTCs depend on pool geometries and hydrological conditions. The simulations reveal that the two-region nonequilibrium model yields the best fits to experimental BTCs because the model can describe the transient storage in pools by the partition coefficient and the mass transfer coefficient. The model parameters indicate that pools produce high dispersion. The increased tailing occurs mainly because the partition coefficient decreases, as the number of pools increases. When comparing the tracer BTCs obtained using the two types of pools with the same size, the more appreciable BTC tails that occur for symmetrical pools likely result mainly from the less intense exchange between the water in the pools and the water in the pipe, because the partition coefficients for the two types of pools are virtually identical. Dispersivity values decrease as flow rates increase; however, the trend in dispersion is not clear. The reduced tailing is attributed to a decrease in immobile water with increasing flow rate. It provides evidence for hydrodynamically controlled tailing effects. 相似文献
137.
Evaluation of basin environmental vulnerability: the weighted method compared to the compromise method 总被引:1,自引:0,他引:1
C.-L. Chang 《International Journal of Environmental Science and Technology》2013,10(5):1051-1056
Environmental vulnerability analysis is an important issue in conducting sustainable basin management. In our past study, we developed a set of criteria from three categories of factors (geographic, hydrologic, and societal) for assessing basin environmental vulnerability. According to a survey and the analytical hierarchy process (AHP) analysis, seven criteria were selected as a set of criteria, and the weights of these criteria were determined. This study adopts two different multiple criteria analysis (MCA) methods, the weighted method and the compromise method, to integrate the criteria and evaluate the environmental vulnerability of major basins in Taiwan. The results show that the Cho-Shui River Basin has the highest environmental vulnerability, no matter which method is used. However, the environmental vulnerability of the Ta-Chia River Basin is higher than that of the Tan-Shui River Basin and the Tseng-Wen River Basin when considering the measure of individual regret by the modified VIKOR method, which generates a different ranking than that of the weighted method. Stricter land-use restrictions should be placed on those basins that have higher environmental vulnerability. According to the analysis, the results of basin environmental vulnerability, land-use classification strategies can be created. 相似文献
138.
139.
关于生命起源研究的问题及其主攻方向的探讨 总被引:1,自引:0,他引:1
本文综述和分析了近几十年来国内外关于生命起源的研究的问题及各种假说和见解,提出物质的起源是生命起源问题研究的核心,生命起源问题应是研究原始地球的非生命物质如何演变成为生命物质的,地球上分子手性的起源是生命起源问题研究的主攻方向,有机分子光学活性百发生在由化学进化转入生物进化这一过渡阶段。 相似文献
140.
Hung-Ming Lin Shun-Kung Chang Jian-Hong Wu C. Hsein Juang 《Engineering Geology》2009,104(3-4):280-289
This paper is aimed at creating an empirical model for assessing failure potential of highway slopes, with a special attention to the failure characteristics of the highway slopes in the Alishan, Taiwan area prior to, and post, the 1999 Chi-Chi, Taiwan earthquake. The basis of the study is a large database of 955 slope records from four highways in the Alishan area. Artificial neural network (ANN) is utilized to “learn” from this database. The developed ANN model is then used to study the effect of the Chi-Chi earthquake on the slope failure characteristics in the Alishan area. Significant changes in the degrees of influence of several factors (variables) are found and possible reasons for such changes are discussed. The novelty of this paper lies in the fact that the developed ANN models are used as a tool to investigate the slope failure characteristics before and after the Chi-Chi earthquake. 相似文献