全文获取类型
收费全文 | 8553篇 |
免费 | 1775篇 |
国内免费 | 2661篇 |
专业分类
测绘学 | 965篇 |
大气科学 | 2109篇 |
地球物理 | 2248篇 |
地质学 | 3892篇 |
海洋学 | 1744篇 |
天文学 | 359篇 |
综合类 | 531篇 |
自然地理 | 1141篇 |
出版年
2024年 | 60篇 |
2023年 | 164篇 |
2022年 | 311篇 |
2021年 | 444篇 |
2020年 | 436篇 |
2019年 | 504篇 |
2018年 | 450篇 |
2017年 | 449篇 |
2016年 | 449篇 |
2015年 | 475篇 |
2014年 | 579篇 |
2013年 | 684篇 |
2012年 | 583篇 |
2011年 | 586篇 |
2010年 | 538篇 |
2009年 | 664篇 |
2008年 | 607篇 |
2007年 | 659篇 |
2006年 | 593篇 |
2005年 | 513篇 |
2004年 | 477篇 |
2003年 | 389篇 |
2002年 | 364篇 |
2001年 | 297篇 |
2000年 | 256篇 |
1999年 | 238篇 |
1998年 | 196篇 |
1997年 | 182篇 |
1996年 | 179篇 |
1995年 | 120篇 |
1994年 | 106篇 |
1993年 | 99篇 |
1992年 | 87篇 |
1991年 | 59篇 |
1990年 | 53篇 |
1989年 | 31篇 |
1988年 | 26篇 |
1987年 | 22篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1954年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
23.
本文主要介绍了应用 X射线荧光方法在狮子山铜矿进行岩壁 X取样的技术和工作过程 ,提出了一些克服岩壁 X取样影响因素的方法。并对使用效果进行了评价 相似文献
24.
航空短波红外分光谱遥感技术直接寻找油气藏的有效性及应用实例 总被引:1,自引:0,他引:1
采用航空短波红外分光谱遥感技术,在新疆准噶尔盆地和塔里木盆地某些油气区,进行直接寻找油气资源的试验研究后发现,油气区含油岩系,油气藏上方盖层土壤的光谱在2300和2350nm波段具有双吸收特征。 相似文献
25.
The application of X-ray photoelectron spectroscopy (XPS) to coal surface characterisation for preparation research is described. Progress towards the acquisition of complementary surface chemical information by time-of-flight secondary ion mass spectrometry (ToF-SIMS) is also discussed. Surface-based beneficiation techniques such as flotation are assuming greater importance as the proportion of fines in raw coal increases due to the proliferation of high capacity mining methods. A necessary condition for the floatability of a coal particle is adequate hydrophobicity, and the degree of hydrophobicity of the flotation concentrate is one factor influencing the ease with which its dewatering can be affected. The hydrophobicity of a coal is very difficult to measure directly because of microporosity, and it is often necessary to deduce the degree of hydrophobicity from a knowledge of the surface chemistry. XPS is able to provide sufficient analytical data to allow relative levels of hydrophobicity to be estimated. In principle, ToF-SIMS should be able to supply additional information enabling refinement of such estimates; however, there are insufficient data at present to allow the ionic fragments detected to be related to specific functional groups at the coal surface. 相似文献
26.
液化土层对地表加速度反应谱的影响 总被引:4,自引:0,他引:4
采用一种改进的有效应力方法研究土层液化对地表加速度反应谱的影响,分析中考虑了砂层的厚度、埋深和输入地震波的幅值和波型等因素。分析结果表明,土层液化使地表加速度反应谱的特征周期至少延长0.1秒以上,使原Ⅱ类场地变为Ⅲ类场地,高烈度时易变成Ⅳ类场地,反应谱中周期0.8秒-1.0秒是液化砂层加震或减震的一个分界点,液化对反应谱短周期分量具有一定的减震作用,而对长周期分量有非常显著的放大作用。 相似文献
27.
Using data from the intensive observation period (May–June 2000) of the NWC-ALIEX (The Field Experiment on Interaction between Land and Atmosphere in Arid Region of North-west China), the characteristics and mechanisms of some key land-surface process over Gobi in a typical arid region of north-west China are analyzed and several parameters of land-surface processes are calculated. The weighted mean of the surface albedo over a typical arid region of the Dunhuang Gobi is calculated using the relative reflection as a weighting factor, and its value is 0.255 ± 0.021. After removing the influence of precipitation, the mean soil heat capacity over a typical arid region of the Dunhuang Gobi is 1.12 × 106 J m-3 K-1,which is smaller than that observed in the Heihe (China) River basin Field Experiment (HEIFE). The mean soil heat diffusivity and conductivity are about half of those observed in HEIFE. 相似文献
28.
遥感影像三维可视化研究 总被引:1,自引:0,他引:1
利用DEM高程资料实现遥感影像的三维显示可大大提高遥感监测产品的使用价值,而商用软件成本高操作繁琐普及困难。利用计算机图形学知识和Delphi编程语言,开发了一套遥感影像三维可视化软件。对在开发过程中遇到的有关DEM数据的裁剪与拼接、图像配准、地表模拟、透视变换、消隐处理、光照和阴影效果以及颜色变换等问题的解决方案和实现方法作了简要的介绍。 相似文献
29.
Structural and geotechnical impacts of surface rupture on highway structures during recent earthquakes in Turkey 总被引:4,自引:0,他引:4
The most significant damage on highway bridges during the recent earthquakes in Turkey (Kocaeli and Duzce earthquakes) and Taiwan (Chi–Chi earthquake) was the result of fault ruptures traversing transportation infrastructure. This phenomenon and its consequences accentuate the need to examine surface rupture hazards and to identify those areas at risk. This understanding can help to develop remedial measures for both structural and geotechnical engineering. For that purpose, damage to highway bridges during the recent events was reviewed. The total collapse of the highway overpass in Arifiye, during the Kocaeli earthquake, was investigated. The major problems under consideration (in Arifiye) were: (i) dislodging of the bridge spans, and consequently, the total separation of the reinforced concrete girders from the piers; and (ii) the stability of a mechanically stabilized earth wall (MSEW) system under extreme loading conditions. The results of the structural and geotechnical investigations presented herein can be taken in consideration to improve transportation infrastructure against surface rupture hazards. 相似文献
30.