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71.
Shucong Ai Quanliang Chen Jianping Li Ruiqiang Ding Quanjia Zhong 《Asia-Pacific Journal of Atmospheric Sciences》2017,53(2):243-256
The nonlinear local Lyapunov exponent (NLLE) method is adopted to quantitatively determine the predictability limit of East Asian summer monsoon (EASM) intensity indices on a synoptic timescale. The predictability limit of EASM indices varies widely according to the definitions of indices. EASM indices defined by zonal shear have a limit of around 7 days, which is higher than the predictability limit of EASM indices defined by sea level pressure (SLP) difference and meridional wind shear (about 5 days). The initial error of EASM indices defined by SLP difference and meridional wind shear shows a faster growth than indices defined by zonal wind shear. Furthermore, the indices defined by zonal wind shear appear to fluctuate at lower frequencies, whereas the indices defined by SLP difference and meridional wind shear generally fluctuate at higher frequencies. This result may explain why the daily variability of the EASM indices defined by zonal wind shear tends be more predictable than those defined by SLP difference and meridional wind shear. Analysis of the temporal correlation coefficient (TCC) skill for EASM indices obtained from observations and from NCEP’s Global Ensemble Forecasting System (GEFS) historical weather forecast dataset shows that GEFS has a higher forecast skill for the EASM indices defined by zonal wind shear than for indices defined by SLP difference and meridional wind shear. The predictability limit estimated by the NLLE method is shorter than that in GEFS. In addition, the June-September average TCC skill for different daily EASM indices shows significant interannual variations from 1985 to 2015 in GEFS. However, the TCC for different types of EASM indices does not show coherent interannual fluctuations. 相似文献
72.
Moon Y.-J. Yun H.S. Lee S.W. Kim J.-H. Choe G.S. Park Y.D. Ai G. Zhang H.Q. Fang C. 《Solar physics》1999,184(2):323-338
In this paper we introduce a measure of magnetic field discontinuity, MAD, defined as Maximum Angular Difference between two adjacent magnetic field vectors. To examine the characteristics of the MAD, we have considered several active region models having a quadrupolar field configuration and computed MADs over these active regions by approximating the 3-D magnetic fields as an ensemble of charge potential fields or linear force-free fields. The computed MAD fields are studied in comparison with other flare activity indicators such as separators. It is found that (1) the region of high level MAD corresponds well with the separator, or practically the intersection of the separator with the plane of measurement, (2) it singles out local discontinuities of magnetic fields, and (3) the MAD can also be a measure of the evolutionary status of an active region.An observational test has been made for 2-D MADs, using the Yohkoh SXT observation of a flare in AR 6919 and the vector magnetogram taken at the Mees Solar Observatory during this flare activity. The high level contours of 2-D MAD are found to trace well the observed soft X-ray bright points, which indicates that the MAD could serve as a good flare activity indicator. 相似文献
73.
南京地下水开采引起的环境地质问题及防治对策 总被引:3,自引:0,他引:3
近些年来,南京市的地下水开采量呈上升趋势,引发了泉水干涸、地面沉降、塌陷、水质恶化等一系列环境地质问题。对此进行了全面细致的分析,并提出了防治这些环境地质问题的措施,对我国城市地下水资源的合理规划和管理具有一定的借鉴意义。 相似文献
74.
记甘肃华池的一件空棘鱼类化石 总被引:2,自引:0,他引:2
本文记述了一件产自甘肃华池晚三叠世的空棘鱼类化石,并讨论了陕甘宁盆地中生代早,中期一些含鱼沉积的海相成因及可能与油气生成的关系。 相似文献
75.
1998年5月29日皮山县发生6.2级地震,震中距皮山县城约39km,震源深度为32km,烈度分布区为北西-南东走向的椭圆形,极震区烈度为Ⅶ度,个别点为Ⅷ度,地震使皮山县县城,9个乡,2个镇,2个农场,墨玉县部分地区遭到不同程度的损失。共计受伤人数为26人,其中重伤为2人,无家可归者人数为5566人,1392户,牲畜死亡4454头。地震造成的直接经济损失达5486.75万元。 相似文献
76.
塔里木盆地雅克拉断凸前中生界不整合面之下下奥陶统白云岩储层特征 总被引:11,自引:2,他引:9
研究表明,塔里木盆地雅克拉断凸内前中生界不整合面之下下奥陶统白云岩储层具以下特证:储集岩类简单,但结构较为复杂,主要有浅灰、灰黄色厚层含粒屑中-细晶白云岩,亮晶砂屑白云岩,硅质细-中晶白云岩、细-中晶残余砂屑白云岩,细晶残余鲕粒白云岩,粉-粗晶白云岩,局部有灰白色硅质岩。储层所经历的成岩作用有8种。其中,胶结作用、压实作用是使储层储集性能变差的主要成岩作用,而白云石化作用、破裂作用、溶蚀作用,特别是表生淡水溶蚀作用是产生次生孔隙的主要成岩作用。储层进油期孔隙以次生型为主,主要有晶间孔、晶间溶孔,胶结物内溶孔、溶洞、裂(溶)缝、晶间缝,孔隙度一般5%~8%,局部高达15%,故此其储集类型为孔、洞、缝复合型。储层含油气丰富,其含油饱和度高达75%,是重要的高产工业油气层。 相似文献
77.
从某一大型工程中的邻海区域江堤加固工程的各种方案比较出发,分析讨论了这类工程结构形式受波浪作用的情况及结构物设计中方案比选的有关问题。 相似文献
78.
79.
As an important method of terrain representation, a DEM usually needs to be generalized at multiple resolutions in order to adapt to different applications. The preservation of main landscape features is an important constraint in DEM generalization. The traditional generalization method based on signal processing by resampling or low-pass filtering is just a data compression operation rather than the abstraction of real information. This study develops a structured analysis method to generalize DEM data through the identification of minor valleys and filling the corresponding depression positions. The generalization process has two steps: geographic decision and geometric operation. According to their hydrological significance, the unimportant valley branches are detected and their corresponding coverage is filled by raising the terrain to make the terrain surface smoother. In contrast to the conventional algorithms based on image processing, this method is able to retain the main geographical characteristics more effectively in terrain representation. 相似文献
80.