全文获取类型
收费全文 | 41382篇 |
免费 | 6973篇 |
国内免费 | 10420篇 |
专业分类
测绘学 | 4954篇 |
大气科学 | 6596篇 |
地球物理 | 9824篇 |
地质学 | 20335篇 |
海洋学 | 5951篇 |
天文学 | 2412篇 |
综合类 | 3067篇 |
自然地理 | 5636篇 |
出版年
2024年 | 150篇 |
2023年 | 491篇 |
2022年 | 1244篇 |
2021年 | 1482篇 |
2020年 | 1824篇 |
2019年 | 1962篇 |
2018年 | 1622篇 |
2017年 | 2040篇 |
2016年 | 2000篇 |
2015年 | 2260篇 |
2014年 | 2565篇 |
2013年 | 3032篇 |
2012年 | 2708篇 |
2011年 | 2810篇 |
2010年 | 2232篇 |
2009年 | 2760篇 |
2008年 | 2795篇 |
2007年 | 3103篇 |
2006年 | 3007篇 |
2005年 | 2446篇 |
2004年 | 2242篇 |
2003年 | 1885篇 |
2002年 | 1571篇 |
2001年 | 1363篇 |
2000年 | 1431篇 |
1999年 | 1287篇 |
1998年 | 1169篇 |
1997年 | 924篇 |
1996年 | 778篇 |
1995年 | 663篇 |
1994年 | 568篇 |
1993年 | 521篇 |
1992年 | 403篇 |
1991年 | 298篇 |
1990年 | 202篇 |
1989年 | 225篇 |
1988年 | 151篇 |
1987年 | 105篇 |
1986年 | 100篇 |
1985年 | 74篇 |
1984年 | 46篇 |
1983年 | 19篇 |
1982年 | 28篇 |
1981年 | 23篇 |
1980年 | 25篇 |
1978年 | 15篇 |
1977年 | 22篇 |
1976年 | 25篇 |
1973年 | 18篇 |
1971年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
41.
ENVIRONMENTAL SUSTAINABILITY AND SCENARIOS OF URBANIZATION IN ARID AREA——A Case Study in Wuwei City of Gansu Province 总被引:1,自引:0,他引:1
YOUFei LIYu DONGSuo-cheng 《中国地理科学(英文版)》2005,15(2):120-130
1IN T R O D U C T IO N The western China isfacinggrowing problems of eco- logicaland economic development. The disparitiebse- tween the socio-economy of the western and eastern China were enlarging, and the major ecologicalprob- lems stilelvolve as past(H… 相似文献
42.
43.
A highly automated moving object detection package 总被引:1,自引:0,他引:1
44.
45.
Sang-konKim Maeng-eonPark Seung-gyunBaek Kyu-youlSung Sun-okKim Hee-yulPark 《东北亚地学研究》2004,7(2):125-135
Chemical composition, Raman microspectrometry, and Fourier transform infrared (FT-1R) and SEM-CL (Cathodluminescence) analyses are carried out for Tanzania and Madagascar garnets for locality identification. Inclusion study was sustained after electron probe microanalysis (EPMA). Needle-like illmenites, apatites and zircons were the most common solid inclusions in Tanzania garnets. Madagascar garnets revealed rutile needles and apatites were also observed, but differences in size, shape and distribution patterns were noticed compared to Tanzania garnets. Tanzania garnets exhibited all types of observable fluid inclusions such as ““ fingerprint““ pattern, called Type Ⅰ-A, liquid-only (L) single phase fluid inclusion, called Type Ⅰ-B and Type Ⅱ-A ( L S), Type Ⅱ-B ( L V) and Type Ⅲ-A (L Sylvite even if all examined garnets from three localities retained ““fingerprint““ features, so called, partially healed fractures, in common. Chemical composition, Raman microspectrometry and Fourier transform infrared (FT-IR) analysis taken turned out to be useful methods for the purpose of this study. Using consequences of SEM-CL and inclusion study, accordingly, the locality identification of gem-quality garnets is capable of being available in further application for other kinds of gemstones. 相似文献
46.
薛建康 《成都信息工程学院学报》1990,(1)
本文针对冬半年高原低涡几个不同源地的低涡生成背景,着重分析500hpa环流场,指出:地形对低涡生成是非常重要的条件,但一定范围内有利的环境流场也是低涡生成不可缺少的外部条件。并给出了不同涡源区有利于低涡发生,发展的500hpa环流形势。 相似文献
47.
介绍了MATLAB语言特点和系统建模方法的基本理论.根据南海气象数据的实际建模处理过程,给出了建模的详细步骤及其MATLAB实现过程以及MATLABTM的主要实现程序.试验讨论和结果表明利用MATLAB语言可以方便地对南海气象数据用系统建模方法进行建模和处理,MATLAB在运用系统建模法处理南海气象数据方面具有明显的优越性. 相似文献
48.
Majid T. Manzari 《国际地质力学数值与分析法杂志》2004,28(10):1011-1032
A micropolar elastoplastic model for soils is formulated and a series of finite element analyses are employed to demonstrate the use of a micropolar continuum in overcoming the numerical difficulties encountered in application of finite element method in standard Cauchy–Boltzmann continuum. Three examples of failure analysis involving a deep excavation, shallow foundation, and a retaining wall are presented. In all these cases, it is observed that the length scale introduced in the polar continuum regularizes the incremental boundary value problem and allows the numerical simulation to be continued until a clear collapse mechanism is achieved. The issue of grain size effect is also discussed. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
49.
50.
基于SAR干涉点目标分析技术的城市地表形变监测 总被引:1,自引:0,他引:1
通过深入研究干涉点目标的相位模型,提出基于空间搜索的邻近点目标干涉相位差解缠方法,用以计算点目标的地形残差和线性形变,以及分离点目标大气延迟相位和非线性形变相位的时空域滤波方法,解决干涉点目标分析中的关键问题.最后,以苏州地区地表沉降监测为应用试验,利用形成的SAR干涉点目标形变信息提取技术,获取苏州市区1992-2002年间的地表沉降信息.研究结果与已有文献记录保持比较好的一致性,证明SAR干涉点目标技术完全可以发展成为应用于城市地表形变监测的实用化技术.Abstract: Interferometric point target analysis (IPTA) is one of the latest developments in radar interferometric processing. It is achieved by analysis of the interferometric phases of some individual point targets, which are discrete and present temporarily stable backscattering characteristics, in long temporal series of interferometric SAR images. This paper analyzes the interferometric phase model of point targets, and then addresses two key issues within IPTA process. Firstly, a spatial searching method is proposed to unwrap the interferometric phase difference between two neighboring point targets. The height residual error and linear deformation rate of each point target can then be calculated, when a global reference point with known height correction and deformation history is chosen. Secondly, a spatial-temporal filtering scheme is proposed to further separate the atmosphere phase and nonlinear deformation phase from the residual interferometric phase. Finally, an experiment of the developed IPTA methodology is conducted over Suzhou urban area. Totally 38 ERS-1/2 SAR scenes are analyzed, and the deformation information over 3 546 point targets in the time span of 1992-2002 are generated. The IPTA-derivecl deformation shows very good agreement with the published result, which demonstrates that the IPTA technique can be developed into an operational tool to map the ground subsidence over urban area. 相似文献