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991.
Along with the booming of dendrochronology in China, the woody species for the tree-ring study have expanded gradually from tree species to the shrub and dwarf shrub species in the last decades. The zonal woody species in the vast alpine mountains, arid desert areas and arid regions in China are mostly shrubs and semi-shrubs, which is very important to understand the process of regional evolution, environmental protection and ecological recovery. In this paper, the shrub species which have been studied on tree rings in cold and arid areas of China were collected and sorted, and the fundamental research advances were presented, which include the shrub tree ring identification, radial growth characteristics, and chronology construction by different parameters. The applications of shrub dendrochronology to the subjects in eco-response, paleoclimate reconstruction, hydrological process, ecological study of artificial forest and ecological restoration were also presented. The prospect of shrub dendrochronology in the future was also discussed. 相似文献
992.
The effect of vertical transports of heat and moisture by cumulus convection in typhoon 总被引:1,自引:0,他引:1
By utilizing the denser upper-air observations from the Okinawa region and Japanese islands during August 17-23, 1975, the vertical transports of heat and moisture by cumulus convection in the typhoon No. 7507 have been calculated. It is found that there exist a large apparent heat source (Q1) and a mois-ture sink (Q2) in the southern part of the typhoon at the disturbance, growing and mature stages. The magnitudes of the apparent heat source and moisture sink ace rather small, or turn into the apparent heat sink in the northern sector of the typhoon. In the southern part of the typhoon, the total cloud mass flux (Mc) is positive, whereas in the northern part of the typhoon Mc is negative. The above-mentioned distributions of Q1, Q2 and Mc agree well with the major cloud patterns.In the southern part of the typhoon, Q2 is positive because the drying effect is always larger than the evaporative cooling, whereas in the northern part of the typhoon, the opposite case is true because both the drying and evaporating effects of liquid water make a negative contribution to Q2. 相似文献
993.
994.
Dr. An Zhisheng Dr. Liu Tungsheng Dr. Zhou Yizhi Dr. Sun Fuqing Dr. Ding Zhongly 《GeoJournal》1987,15(2):141-143
Having investigated the loess-paleosol sequence in various loess deposition basins in the China Loess Plateau, authors have found that the paleosol complex S5 is of special significance in terms of Pleistocene paleoclimate. Paleopedological, micromorphological, palynological and paleomagnetic evidences indicate that this paleosol complex formed in the interval of 460,000 to at least 560,000 years BP, which was a climatic optimum. 相似文献
995.
The normal typhoon paths with 109 cases during the period from 1960 to 1979 have been analysed in this study.These paths are divided into 7 categories.The effect of the position and intensity of largescale wave on each category has been examined.It has been discovered,as a result,that this effect is rather evident.On the other hand,the teleconnection between different centers of anion does exist.A simple theoretical analysis indicates that the teleconnection is related to the propagation of wave energy.Thus,to predict comectly typhoon path,not only the steering flow of typhoon,but also,more significantly,the behavior of large-scale wave over the Northern Hemisphere must be taken into consideration. 相似文献
996.
本文用单轴压缩下砂岩试件的P、s波超声实验,对含裂隙高空度砂岩破裂前的Vp、Vs、Vp/Vs、Ap、As、As/Ap,初动段频谱,介质传递函数作了一系列实验研究。结果表明:l.Vp、Vs及Vp/Vs的变化同花岗岩,2.As/Ap要发生变化,3.有低频增加现象,4.介质传递函数发生变化,5.有第二P波产生。最后文章用两相介质中地宸波传播理论对实验结果作了定量分析。 相似文献
997.
998.
目的:探讨经方治疗晚期肺癌的辨治规律及处方用药。方法:收集中国知网(CNKI)中运用经方治疗晚期肺癌的病案,通过Medcase V5.2仓公诊籍国医脉案数据记录挖掘系统,运用频数分析与关联规则分析,从临床症状、舌象、脉象、病机、处方用药等多方面对经方治疗晚期肺癌的病案进行数据挖掘。结果:晚期肺癌的主要临床表现有咳嗽、疲倦乏力、食欲不振、胸闷、易醒、入睡困难等;频数较高的舌象有舌质暗红、舌质红、舌质淡红、舌质淡、苔薄白、苔黄腻;频数较高的脉象有细、弦、滑、沉、数、弱;病机主要为癌毒郁肺、肺脾气虚、肺失宣肃、肝郁化火、痰热壅肺、水饮停肺;常用药物有茯苓、法半夏、炙甘草、大枣、桂枝、柴胡等;通过关联规则分析,得到30组关联症状、28组关联病机、30组病机与临床症状关联。结论:应用数据挖掘法能够反映经方治疗晚期肺癌的辨治规律,具有一定的临床指导意义。 相似文献
999.
The origin of the Tertiary ‘red clay’ underlying the Pleistocene loess in the Chinese Loess Plateau remains controversial, although several lines of evidence have suggested a wind‐blown origin. This study examines the particle‐size parameters of the late Miocene and Pliocene ‘red clay’ by comparing it with those of the late Pleistocene loess. The particle‐size distribution of a total of 15 339 loess and 6394 ‘red clay’ samples taken from 12 loess sections along a north–south transect and two ‘red clay’ sequences at Lingtai and Jingchuan was systematically analysed. The median grain size, skewness and kurtosis of the late Pleistocene loess all show a systematic southward change and are principally influenced by distance from source region. The spatial and temporal differentiation of dust deposits is expressed in a skewness–kurtosis–median grain size ternary diagram, from which the distance to the source region can be inferred. The particle‐size characteristics of the Tertiary ‘red clay’ sediments are very similar to those of the palaeosols within the late Pleistocene loess deposits, suggesting an aeolian origin for the ‘red clay’. Based on the comparison of ‘red clay’ and loess in the ternary diagrams, it is inferred that the source–sink distance was greater in the Neogene than in the last and penultimate interglacials, and that the dust source region in north‐western China underwent a progressive expansion during the period from at least 7·0 Ma to the present. 相似文献
1000.
The diurnal-variation anomalies of the vertical-component in geomagnetic field are mainly the changes of phase and amplitude
before strong earthquakes. On the basis of data recorded by the network of geomagnetic observatories in China for many years,
the anomalous features of appearance time of the minima of diurnal variations (i.e, low-point time) of the geomagnetic vertical components and the variation of their spatial distribution (i.e, phenomena of low-point displacement) have been studied before over 30 strong earthquakes with M
S≥6.6 such as Kunlunshan M
S=8.1 earthquake on November 14, 2001; Bachu-Jashi M
S=6.8 earthquake on February 24, 2003; Xiaojin M
S=6.6 earthquake on September 22, 1989, etc. There are good relations between such rare phenomena of geomagnetic anomalies and the occurrence of earthquakes. It has
been found that most earthquakes occur in the vicinity of the boundary line of sudden change of the low-point displacement
and generally within four days before and after the 27th or 41st day counting from the day of appearance of the anomaly. In
addition, the anomalies of diurnal-variation amplitude near the epicentral area have been also studied before Kunlunshan M
S=8.1 earthquake and Bachu-Jiashi M
S=6.8 earthquake.
Foundation item: National Science Technology Tackle Key Project during the Tenth Five-year Plan (2001BA601B01-05-04) 相似文献