全文获取类型
收费全文 | 641篇 |
免费 | 104篇 |
国内免费 | 135篇 |
专业分类
测绘学 | 69篇 |
大气科学 | 140篇 |
地球物理 | 166篇 |
地质学 | 260篇 |
海洋学 | 112篇 |
天文学 | 54篇 |
综合类 | 53篇 |
自然地理 | 26篇 |
出版年
2024年 | 7篇 |
2023年 | 27篇 |
2022年 | 60篇 |
2021年 | 50篇 |
2020年 | 29篇 |
2019年 | 37篇 |
2018年 | 9篇 |
2017年 | 17篇 |
2016年 | 45篇 |
2015年 | 22篇 |
2014年 | 30篇 |
2013年 | 17篇 |
2012年 | 26篇 |
2011年 | 39篇 |
2010年 | 35篇 |
2009年 | 39篇 |
2008年 | 59篇 |
2007年 | 36篇 |
2006年 | 41篇 |
2005年 | 38篇 |
2004年 | 24篇 |
2003年 | 31篇 |
2002年 | 23篇 |
2001年 | 25篇 |
2000年 | 23篇 |
1999年 | 25篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有880条查询结果,搜索用时 31 毫秒
801.
果糖-1,6-二 磷酸酶(fructose-1,6-bisphosphatase,FBP, EC 3. 1.3.11)可催化果糖-1,6-二磷酸水解成果糖-6-磷酸和无机磷酸盐,是糖异生途径中的关键酶之一。本研究运用SMART RACE技术从鲈鱼Lateolabrax japonicus肝脏中分离克隆了FBP基因的全长cDNA序列,该基因全长1 357 bp,其中5’非翻译区和3’非翻译区分别为42 bp和301 bp,开放阅读框为1 014 bp,共编码337个氨基酸。蛋白质分子量约为36.7 kD,理论pI为6.90。氨基酸序列分析表明,鲈鱼FBP与其它动物的肝脏型FBP相似性很高,与裸盖鱼、彩虹胡瓜鱼、斑马鱼、异育银鲫和大西洋鲑的肝脏型FBP的同源性分别为94.3%,90. 8%,89.3%,88.1%和84.1%。系统发育分析显示,鲈鱼FBP与其它鱼类的肝脏型FBP成簇后再与哺乳动物的肝脏型FBP聚成一支,然后才与哺乳动物的肌肉型FBP汇成簇。同时用RT-PCR分析了FBP基因在鲈鱼肝脏、肌肉、心脏、眼、肠、肾脏、脂肪、脾脏、鳃和大脑等10个组织的表达,结果表明FBP仅在肝脏、肾脏和肠这3个组织中有较高的表达,与糖异生发生组织基本一致,因此推测该FBP属于肝脏型。 相似文献
802.
基于6S模型的MODIS影像逐像元大气校正及其应用 总被引:1,自引:0,他引:1
以获取地物真实反射率为目的,介绍了逐像元大气校正的方法。应用6S模型逐像元综合考虑太阳天顶角、传感器天顶角、相对方位角、大气气溶胶厚度、观测波段以及地表海拔这6个参数,生成查找表,统计分析各参数关于反射率的敏感度;并与以往单一参数校正的方法比较了校正的效果。结果表明,逐像元大气校正算法更加接近地物的真实反射率。利用MODIS地表反射率产品对大气校正的结果进行验证,单一参数、逐像元大气校正的相对误差分别控制在26.9%和12.7%以内;在以植被指数(NDVI)为例的后续遥感定量化反演过程中,逐像元比单一参数大气校正方法计算的NDVI平均高出14.4%。 相似文献
803.
Assessing the influence of the Merzbacher Lake outburst floods on discharge using the hydrological model SWIM in the Aksu headwaters,Kyrgyzstan/NW China 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《水文研究》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Glacial lake outburst floods (GLOF) often have a significant impact on downstream users. Including their effects in hydrological models, identifying past occurrences and assessing their potential impacts are challenges for hydrologists working in mountainous catchments. The regularly outbursting Merzbacher Lake is located in the headwaters of the Aksu River, the most important source of water discharge to the Tarim River, northwest China. Modelling its water resources and the evaluation of potential climate change impacts on river discharge are indispensable for projecting future water availability for the intensively cultivated river oases downstream of the Merzbacher Lake and along the Tarim River. The semi‐distributed hydrological model SWIM was calibrated to the outlet station Xiehela on the Kumarik River, by discharge the largest tributary to the Aksu River. The glacial lake outburst floods add to the difficulties of modelling this high‐mountain, heavily glaciated catchment with poor data coverage and quality. The aims of the study are to investigate the glacier lake outburst floods using a modelling tool. Results include a two‐step model calibration of the Kumarik catchment, an approach for the identification of the outburst floods using the measured gauge data and the modelling results and estimations of the outburst flood volumes. Results show that a catchment model can inform GLOF investigations by providing ‘normal’ (i.e. without the outburst floods) catchment discharge. The comparison of the simulated and observed discharge proves the occurrence of GLOFs and highlights the influences of the GLOFs on the downstream water balance. © 2013 The Authors. Hydrological Processes Published by John Wiley & Sons Ltd. 相似文献
804.
通过岩芯观察描述、铸体薄片鉴定、毛细管压力分析以及扫描电镜等分析测试手段,结合测井解释成果,分析了镇泾油田长6与长8油层组油井产能的差异及其影响因素。结果表明:沉积相带、储层微观特征、裂缝发育程度、封盖条件以及储层伤害等是决定镇泾油田油井产量的关键因素。因此,在镇泾油田长8和长6油层组开发过程中,应根据不同沉积相带及其储层特征的差异,从改进油井施工工艺等方面入手,调整开发方案,改善储层的渗流能力,从而提高油井的产能。 相似文献
805.
806.
807.
Active tectonics around the junction of Southwest Japan and Ryukyu arcs: Control by subducting plate geometry and pre‐Quaternary geologic structure
下载免费PDF全文
![点击此处可从《Island Arc》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yukinobu Okamura 《Island Arc》2016,25(4):287-297
The origin of active faults in the Inner zone of the western part of Southwest Japan was explained by a decrease of the minimum principal stress and reactivation of ancient geologic structures. Although the E–W maximum principal stress in Southwest Japan due to the collision of the Southwest and Northeast Japan arcs along the Itoigawa–Shizuoka Tectonic Line is assumed to decrease westward, the density of active strike‐slip faults increases in the western margin of the Southwest Japan Arc (western Chugoku and northern Kyushu) where the subducting Philippine Sea Plate dips steeply. The E–W maximum compressional stress is predominant throughout Southwest Japan, while the N–S minimum principal stress that is presumably caused by coupling between Southwest Japan arc and Philippine Sea Plate decreases due to the weak plate coupling as the plate inclination increases under the western margin of Southwest Japan. The increase of the fault density in the western margin of the arc is attributed to a decrease of the minimum principal stress and consequent increase of shear stress. Low slip rates of the active faults in this region support the view that the westward increase of fault density is not a response to increasing maximum stress. These faults of onshore and offshore lie in three distinct domains defined on the basis of fault strike. They are defined domains I, II, and III which are composed of active faults striking ENE–WSW, NW–SE, and NE–SW, respectively. Faulting in domains I, II, and III is related to Miocene rift basins, Eocene normal faults, and Mesozoic strike‐slip faults, respectively. Although these active faults are strike‐slip faults due to E–W maximum stress, it is unclear whether their fault planes are the same as those of pre‐Quaternary dip‐slip faults. 相似文献
808.
Variations in stress and driving pore fluid pressure ratio using vein orientations along megasplay faults : Example from the Nobeoka Thrust,Southwest Japan
下载免费PDF全文
![点击此处可从《Island Arc》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Makoto Otsubo Ayumu Miyakawa Ryoji Kawasaki Katsushi Sato Asuka Yamaguchi Gaku Kimura 《Island Arc》2016,25(6):421-432
The Nobeoka Thrust of Southwest Japan is an on‐land example of an ancient megasplay fault that provides an excellent record of deformation and fluid flow at seismogenic depths. The present study reports: (i) temporal stress changes for the seismogenic period of the Nobeoka Thrust; and (ii) spatial heterogeneities in driving pressure ratios P* obtained from mineral veins around the Nobeoka Thrust fault zone. Many quartz veins that filled mode I cracks can be observed in the hanging wall and footwall of the thrust. Inversion for stress orientation suggests that normal faulting dominated in both the hanging wall and footwall, with similar stress axis orientations in both. The orientation of σ3 for the estimated stress regime is parallel to the slip direction of the Nobeoka Thrust. The detected normal‐faulting‐type stress regimes likely resulted from post‐seismic stress buildup after megathrust earthquakes. The hanging wall of the Nobeoka Thrust has smaller P* values than the footwall. Two possible explanations are proposed for the observed spatial variations in the driving pore fluid pressure ratio, P*: spatial variations in pore fluid pressure Pf are directly responsible for P* variations, or P* variations are controlled by differences in mechanical properties between the hanging wall and footwall. 相似文献
809.
Large‐scale erosion and overbank deposition caused by the July 2013 flood of the Abu River,Yamaguchi City,Japan
下载免费PDF全文
![点击此处可从《Island Arc》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper reports on the erosion, transport, and deposition processes associated with an overbank deposit formed by the flooding of the Abu River on July 28, 2013, in Yamaguchi City, Japan. At the study site, river flows overtopped the levee revetment upstream of a meander bend cutting it off and flowing back into the main channel downstream. In this sequential process, it deposited large amounts of sediments, ranging from mud to cobbles, on the floodplain. The surface of paddy fields adjacent to a railway line, located at the center of the affected floodplain, was severely eroded by the flood flows. Overbank deposits composed of both upstream finer sediments and eroded coarser terrestrial sediments are laid down in the affected area. Large amounts of pebbles and cobbles originating from the eroded terrestrial area formed a gravelly pile on top of the sand and gravel sediments derived from the river. This finding indicates that sands and gravels were deposited prior to the formation of the gravelly pile, probably before and during peak flood flows. An inverse grading structure is evident in the lower to middle part of these comparatively thick deposits, most likely due to differences in transport pattern between entrained terrestrial gravels and upstream finer sediments. 相似文献
810.
Rapid societal change as a proxy for regional environmental forcing: Evidence and explanations for Pacific island societies in the 14–15th centuries
下载免费PDF全文
![点击此处可从《Island Arc》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Given the unquestioned impacts of recent/future environmental changes on human societies, it is reasonable to posit that past societal responses could be used as proxies of contemporaneous environmental forcing and might help identify the drivers of these, particularly where independent evidence of the effects of these events is inadequate. Such areas include Pacific oceanic islands for most of which there is evidence of a societal perturbation in the 14th and 15th centuries that saw the outbreak of region‐wide conflict, abandonment of coastal settlements and the abrupt end of long‐distance cross‐ocean voyaging networks. The contemporaneity of these effects across a vast region requires a driver that is external to particular island groups with the only possibility that of oceanic origin, most likely large waves (tsunamis or storm surges) or rapid sea‐level change. The explanation is less important than the principle that societal changes can be used as proxies for environmental activity. 相似文献