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122.
通过摄影测量方式生产数字地形图,现已得到了制图界的广泛接受。作为生产地形图的第三代数字制图系统(DMS)投放市场已经两年多了,其中之一就是通用计算机辅助制图系统(UCAMS)。UCAMS的理论基础是地图语言。象任何其他语言一样,地图语言有两项基本内容:字母系统和语法,本文讨论的是生产数字地形图开发的地图,并介绍地图字母和地图语法,以及地图语言工具的实例。 相似文献
123.
Geographical distribution and accumulation features of organochlorine residues in bivalves from coastal areas of South Korea 总被引:26,自引:0,他引:26
Kim SK Oh JR Shim WJ Lee DH Yim UH Hong SH Shin YB Lee DS 《Marine pollution bulletin》2002,45(1-12):268-279
As a part of Mussel Watch Program in Korea, the contamination levels and accumulation features of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were assessed for 82 bivalve samples collected from 66 sites along the entire coast of Korea. The dry weight based ∑PCBs and ∑OCPs ranged from 4.4 ng g−1 to 422.0 ng g−1 (geometric MEAN=36.9 ng g−1) and from 9.95 ng g−1 to 131.37 (34.88) ng g−1, respectively. PCB was predominant in Korean coast, followed by DDTs, HCHs, and Chlordanes. From the observed log normal distribution of PCB and each OCP, low- and high-levels were defined as geometric mean ±1 S.D., respectively. The levels at the sites near urban and/or industrial areas often exceeded the high-levels and the spatial distributions of ∑DDTs and ∑CHLs were correlated with that of ∑PCBs, indicating terrestrial input pathways. Even distribution of ∑HCHs suggested a possibility of atmospheric input pathway of HCHs. The observed isomer ratios of DDTs, HCHs, and CHLs indicated that aging has occurred. 相似文献
124.
板块俯冲物质再循环的岩浆岩表现形式,是化学地球动力学研究的核心问题.在海底扩张和板块构造学说发展过程中诞生的化学地球动力学,在研究大洋地质的许多基本问题中已经取得了巨大成功. 相似文献
125.
Teplitz HI McLean IS Becklin EE Figer DF Gilbert AM Graham JR Larkin JE Levenson NA Wilcox MK 《The Astrophysical journal》2000,533(1):L65-L68
Moderate-resolution, near-IR spectroscopy of MS 1512-cB58 is presented, obtained during commissioning of the near-infrared spectrometer (NIRSPEC) on the Keck II telescope. The strong lensing of this z=2.72 galaxy by the foreground cluster MS 1512+36 makes it the best candidate for detailed study of the rest-frame optical properties of Lyman-break galaxies. In 80 minutes of on-source integration, we have detected Halpha, [N ii] lambdalambda6583, 6548, [O i] lambda6300, He i lambda5876, [O iii] lambdalambda5007, 4959, Hbeta, Hgamma, [O ii] lambda3727, and a strong continuum signal in the range of 1.29-2.46 μm. A redshift of z=2.7290+/-0.0007 is inferred from the emission lines, in contrast to the z=2.7233 calculated from UV observations of interstellar absorption lines. Using the Balmer line ratios, we find an extinction of E(B-V) = 0.27. Using the line strengths, we infer a star formation rate (SFR) of 620+/-18 M middle dot in circle yr-1 (H0=75, q0=0.1, and Lambda=0), which is a factor of 2 higher than that measured from narrowband imaging observations of the galaxy but is a factor of almost 4 lower than the SFR inferred from the UV continuum luminosity. The width of the Balmer lines yields a mass of Mvir=1.2x1010 M middle dot in circle. We find that the oxygen abundance is 13 solar, in good agreement with other estimates of the metallicity. However, we infer a high nitrogen abundance, which may argue for the presence of an older stellar population. 相似文献
126.
交通系统是人类经济社会活动的重要空间载体,在全球—区域—地方发展中不断促进各类生产生活要素与人口流动,交通—区域发展交互是人文与经济地理学研究的重要内容。在中国高速交通快速发展和“以人为本”的出行理念下,国内交通地理学在以任务带学科、多学科交叉融合、大数据挖掘与技术多元化的发展模式下,瞄准学科难点和研究瓶颈,服务国家发展需求。围绕交通—区域发展交互领域进行相关的理论与方法创新,以中国科学院地理科学与资源研究所交通地理研究团队为代表,阐明近10年来在交通地理学学科的创新发展。主要贡献在于:(1)高速化、网络化和复杂化视角下的交通地理学理论与方法创新;(2)交通系统与区域—地方互动机制;(3)交通大数据支持下的城市空间组织机理。基于学科理论与方法,研究成果在交通基础设施布局与区域发展“、一带一路”互联互通、新冠疫情防控与交通出行等方面进行了实践应用,为交通强国战略背景下交通地理学研究添砖加瓦。 相似文献
127.
128.
术语是在特定学科领域(包括人文社科)用来表示概念的称谓集合,准确地说,是通过语音或文字来表达或定义科学概念的约定性语言符号。一般来说,它不同于日常用语,它能比较准确、简洁地表达事物的性质和特点。 相似文献
129.
The methods behind the predefined impulse response function in continuous time (PIRFICT) time series model are extended to cover more complex situations where multiple stresses influence ground water head fluctuations simultaneously. In comparison to autoregressive moving average (ARMA) time series models, the PIRFICT model is optimized for use on hydrologic problems. The objective of the paper is twofold. First, an approach is presented for handling multiple stresses in the model. Each stress has a specific parametric impulse response function. Appropriate impulse response functions for other stresses than precipitation are derived from analytical solutions of elementary hydrogeological problems. Furthermore, different stresses do not need to be connected in parallel in the model, as is the standard procedure in ARMA models. Second, general procedures are presented for modeling and interpretation of the results. The multiple-input PIRFICT model is applied to two real cases. In the first one, it is shown that this model can effectively decompose series of ground water head fluctuations into partial series, each representing the influence of an individual stress. The second application handles multiple observation wells. It is shown that elementary physical knowledge and the spatial coherence in the results of multiple wells in an area may be used to interpret and check the plausibility of the results. The methods presented can be used regardless of the hydrogeological setting. They are implemented in a computer package named Menyanthes (www.menyanthes.nl). 相似文献
130.
露天煤矿区植被变化遥感监测与受损程度评估 总被引:1,自引:0,他引:1
以青海省聚乎更露天煤矿区为研究区,利用2001~2016年TM影像,提取了研究区植被覆盖度。以每3 a为一个时间节点,对6期数据进行像元尺度上的线性回归,首先分析了研究区内植被覆盖度变化趋势,并通过植被等级转移矩阵展现不同等级植被间的转移情况;再结合t分布,定量评估了研究区植被受损情况;最后利用剖面分析揭示了研究区恢复治理情况。结果表明,研究区植被长势整体上与时间推移呈负向变化趋势;露天采场、排土场等场地的修建直接摧毁了原有植被,高植被覆盖度区域受损最严重,矿区周边植被受影响程度与距离呈负相关;区内已全面开展恢复治理工作,部分渣山治理效果较为显著。 相似文献