全文获取类型
收费全文 | 504篇 |
免费 | 94篇 |
国内免费 | 76篇 |
专业分类
测绘学 | 27篇 |
大气科学 | 38篇 |
地球物理 | 171篇 |
地质学 | 294篇 |
海洋学 | 23篇 |
天文学 | 20篇 |
综合类 | 62篇 |
自然地理 | 39篇 |
出版年
2023年 | 10篇 |
2022年 | 23篇 |
2021年 | 31篇 |
2020年 | 18篇 |
2019年 | 21篇 |
2018年 | 26篇 |
2017年 | 22篇 |
2016年 | 32篇 |
2015年 | 24篇 |
2014年 | 29篇 |
2013年 | 26篇 |
2012年 | 39篇 |
2011年 | 32篇 |
2010年 | 18篇 |
2009年 | 17篇 |
2008年 | 25篇 |
2007年 | 23篇 |
2006年 | 18篇 |
2005年 | 9篇 |
2004年 | 14篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 34篇 |
1998年 | 21篇 |
1997年 | 28篇 |
1996年 | 15篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1958年 | 3篇 |
排序方式: 共有674条查询结果,搜索用时 218 毫秒
561.
本文介绍了改型后的D/max—ⅢB衍射仪定性检索与多重绘图的基本原理,操作方法及其应用,总结了仪器软件的基本性能和特点。 相似文献
562.
寒冻地区铁路隧道气温状态 总被引:7,自引:0,他引:7
本文根据实测资料论述了寒冻地区铁路隧道内的气温状态,给该地区隧道防冻及排水设计提供了依据,并指出在寒冻地区非多年冻土中开挖隧道后有可能形成多年冻土。 相似文献
563.
以内蒙古中间锦鸡儿(Caragana intermedia)、小叶锦鸡儿(Caragana microphylla),新疆北部粉刺锦鸡儿(Caragana pruinosa)、多刺锦鸡儿(Caragana spinosa)为材料,探讨4种植物叶脉特征是否存在差异,是否促进干旱胁迫下叶忍耐的最低水势的分化。结果表明:中间锦鸡儿、小叶锦鸡儿叶忍耐的最低水势分别为-6.0 MPa和-6.5 M Pa,粉刺锦鸡儿、多刺锦鸡儿忍耐的最低水势分别为-4.0 M Pa和-4.4 M Pa;最低水势与一级脉密度、二级脉密度无线性关系,但随三级叶脉密度和细脉密度的增加而线性增加;最低水势随一级脉、二级脉、三级脉和细脉导管壁厚与导管腔直径比值的三次方(t/b)3增加而增加,但只与细脉(t/b)3显著线性相关。和新疆分布种相比,内蒙古分布种三级脉和细脉密度的增加,细脉抗塌陷能力的增强促进了叶干旱胁迫下忍耐的最低水势的下降。 相似文献
564.
565.
Analysis of surface subsidence mechanism and regularity under the influence of seism and fault 总被引:1,自引:1,他引:0
Surface subsidence with various formation mechanisms possesses varied and complex influencing factors. Thus, studying surface subsidence mechanism and regularity under different special geological conditions is important in implementing disaster prevention and reduction programs. This paper focuses on goaf surface subsidence under the influence of the interaction between seism and fault, taking the Changping Expressway surface subsidence as the case study. In the full investigation of the engineering geological conditions in research area, the graphic method and numerical simulation method FLAC3D are adopted to study surface subsidence mechanism and regularity, after which the influence of seism and fault on surface subsidence is explored. The results show that the Changping Expressway surface subsidence is caused by earthquake-induced reactivation of the old goaf. Under the influence of geological fault, the maximum surface settlement significantly increased, the location of the maximum surface subsidence became close to the fault side, and the subsidence deformation showed an apparent discontinuity near the fault. 相似文献
566.
Kamil Nieścioruk 《The Cartographic journal》2013,50(2):186-196
The paper describes mental maps and their use in teaching process. The survey conducted among students of geodesy and cartography resulted in 124 sketches. They were analysed from the point of view of cartographic methodology and used methods of presentation. The different elements and methods were counted and helped in evaluation of teaching process effectiveness, showing changes in students’ knowledge of certain rules of cartographic language and design and their applications. As the survey was conducted in relation to courses taught, the results are of great value in increasing the quality of cartographic content of these courses and teaching methods. 相似文献
567.
Xue-Liang Zhu Jian-Rong Shi Gang Zhao Ji Li Qing-Xiang Nie 《中国天文和天体物理学报》2007,7(3):405-414
High-resolution optical spectra of the zero age star HD77407 are analysed and its Li, C, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Co, Ni and Ba contents are determined using spectral synthesis method. The temperature of the star is determined by fitting the H α line wings. The parameters derived for this star are Teff=5900K, log g=4.47 and [Fe/H] = 0.07. It is found that the derived iron content is slightly higher than what is given in the published literature. This star shows a relative overabundances of Ca and Ba, and underabundances of Na, V and Ni with respect to the solar mix. Activity of the star is indicated by the filled in Hα and Ca II triplet line cores. It has been confirmed that our spectroscopic approach yields fairly reliable and consistent results for active stars. 相似文献
568.
Suping Nie Tongwen Wu Yong Luo Xueliang Deng Xueli Shi Zaizhi Wang Xiangwen Liu Jianbin Huang 《大气科学进展》2016,33(7):889-904
This paper describes a strategy for merging daily precipitation information from gauge observations, satellite estimates(SEs), and numerical predictions at the global scale. The strategy is designed to remove systemic bias and random error from each individual daily precipitation source to produce a better gridded global daily precipitation product through three steps.First, a cumulative distribution function matching procedure is performed to remove systemic bias over gauge-located land areas. Then, the overall biases in SEs and model predictions(MPs) over ocean areas are corrected using a rescaled strategy based on monthly precipitation. Third, an optimal interpolation(OI)–based merging scheme(referred as the HL-OI scheme)is used to combine unbiased gauge observations, SEs, and MPs to reduce random error from each source and to produce a gauge—satellite–model merged daily precipitation analysis, called BMEP-d(Beijing Climate Center Merged Estimation of Precipitation with daily resolution), with complete global coverage. The BMEP-d data from a four-year period(2011–14) demonstrate the ability of the merging strategy to provide global daily precipitation of substantially improved quality.Benefiting from the advantages of the HL-OI scheme for quantitative error estimates, the better source data can obtain more weights during the merging processes. The BMEP-d data exhibit higher consistency with satellite and gauge source data at middle and low latitudes, and with model source data at high latitudes. Overall, independent validations against GPCP-1DD(GPCP one-degree daily) show that the consistencies between BMEP-d and GPCP-1DD are higher than those of each source dataset in terms of spatial pattern, temporal variability, probability distribution, and statistical precipitation events. 相似文献
569.
570.
Juan?Nie Shihong?DuEmail author Yida?Fan Siquan?Yang Haixia?He Yan?Cui Wei?Zhang 《Journal of the Indian Society of Remote Sensing》2016,44(1):101-110
Accurately obtaining the structures and damage types of buildings in earthquake stricken areas is fundamental to supporting rescue forces and estimating economic losses and casualties. As the stricken areas are often much larger than the areas covered by very high resolution (VHR) images, the information obtained from VHR images cannot satisfy practical needs. This study developed a method for estimating the structures and types of damaged buildings by combining VHR images, statistics and ground survey data. First, the rates of damaged buildings with different structures and damage types were manually interpreted from VHR images covering a small part of the stricken area, and further corrected by ground survey data. Second, the corrected rates were reallocated to the seismic intensity zones. Third, the rates in the seismic intensity zones and the statistical data were combined to estimate the numbers and areas of damaged buildings in villages, towns and counties. The presented method was applied to estimate the damages caused by the Lushan earthquake in China. The results indicated that our method can efficiently estimate the amount of the damages and complement existing work on only automatic extracting damaged buildings from VHR images. 相似文献