首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   109篇
  免费   38篇
  国内免费   20篇
地球物理   24篇
地质学   83篇
海洋学   37篇
天文学   1篇
综合类   19篇
自然地理   3篇
  2024年   2篇
  2023年   1篇
  2022年   3篇
  2021年   2篇
  2020年   3篇
  2019年   5篇
  2018年   4篇
  2017年   5篇
  2016年   6篇
  2015年   6篇
  2014年   11篇
  2013年   6篇
  2012年   16篇
  2011年   12篇
  2010年   15篇
  2009年   16篇
  2008年   7篇
  2007年   8篇
  2006年   5篇
  2005年   8篇
  2004年   7篇
  2003年   7篇
  2002年   3篇
  2001年   2篇
  1998年   1篇
  1997年   2篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1991年   1篇
排序方式: 共有167条查询结果,搜索用时 15 毫秒
151.
适于高温高盐油藏的聚合物性能指标评价   总被引:3,自引:0,他引:3  
我国多数油田经过多年注水开发,综合含水已超过90%,而采出程度低于35%,如何提高油田采收率是高含水油田急需解决的难题。目前,聚合物驱油是工业化应用程度最高的一项提高采收率技术,但由于聚合物产品性能差异和油田现场对污水处理的需要,多数聚合物不适宜高温高盐油田的现场驱油试验。本文以胜坨高温高盐油藏的地质条件为依托,在对聚合物驱油效果影响因素分析的基础上,研究了适合于高温高盐油藏强化采油的聚合物性能指标,优选了具有梳形结构的KYPAM聚合物为胜坨油田的驱替剂。该性能指标的提出对国内外高温高盐油藏进行聚合物驱油具有重要的指导意义。  相似文献   
152.
This work presents at attempt to model brittle ruptures and slips in a continental plate and its spontaneous organization by repeated earthquakes in terms of coarse-grained properties of the mechanical plate. A statistical physics model, which simulates anti-plane shear deformation of a thin plate with inhomogeneous elastic properties, is thus analyzed theoretically and numerically in order to study the spatio-temporal evolution of rupture patterns in response to a constant applied strain rate at its borders, mimicking the effect of neighboring plates. Rupture occurs when the local stress reaches a threshold value. Broken elements are instantaneously healed and retain the original material properties, enabling the occurrence of recurrent earthquakes. Extending previous works (Cowie et al., 1993;Miltenberger et al., 1993), we present a study of the most startling feature of this model which is that ruptures become strongly correlated in space and time leading to the spontaneous development of multifractal structures and gradually accumulate large displacements. The formation of the structures and the temporal variation of rupture activity is due to a complex interplay between the random structure, long-range elastic interactions and the threshold nature of rupture physics. The spontaneous formation of fractal fault structures by repeated earthquakes is mirrored at short times by the spatio-temporal chaotic dynamics of earthquakes, well-described by a Gutenberg-Richter power law. We also show that the fault structures can be understood as pure geometrical objects, namely minimal manifolds, which in two dimensions correspond to the random directed polymer (RDP) problem. This mapping allows us to use the results of many studies on the RDP in the field of statistical physics, where it is an exact result that the minimal random manifolds in 2D systems are self-affine with a roughness exponent 2/3. We also present results pertaining to the influence of the degree of stress release per earthquake on the competition between faults. Our results provide a rigorous framework from which to initiate rationalization of many, reported fractal fault studies.  相似文献   
153.
聚合物/蒙脱石纳米复合材料是当前材料科学的研究热点之一。本文在简述了蒙脱石的结构特征和表面有机修饰的基础上,讨论了聚合物/蒙脱石纳米复合材料的形成机理,即改性后蒙脱石内表面性由亲水性转变为亲油性,其片层被聚合物单体插层或撑开,并均匀分散在聚合物基体中,使复合材料的界面结合增强。该复合材料的结构通常采用XRD,TEM结合DSC,TGA,FT-IR,NMR及STM,AFM等方法来表征。最后重点介绍了该类材料的研究现状及技术发展趋势。  相似文献   
154.
注聚三采期岩电参数的实验   总被引:1,自引:1,他引:0  
中国东部部分油田已进入三次采油期,储层注入聚合物溶液后,储层的物性、电性会发生相应的变化。为了查明储层内注入聚合物溶液后所发生的变化,模拟双河油田开发过程中设计的岩心注聚实验,通过观察注入聚合物的砂岩岩心的实验结果,得出了岩心驱替前后,岩心孔隙度和绝对渗透率变化不大、薄膜电位减小、阿尔奇公式中的孔隙度结构指数优增大,饱和度指数集中在1.4~1.7之间、电阻率变化呈“S"和斜躺“L”型减小等变化规律。注聚后孔隙度和渗透率的计算可以按常规测井评价方法进行,注聚前的薄膜电位明显大于注聚后的薄膜电位,因此注聚后在测井解释中要特别注意自然电位曲线的应用,在聚合物驱油过程中,岩心的电阻率变化规律与盐水驱油过程的电阻率相类似,故在测井评价中可直接使用水驱油田的饱和度的评价方法。  相似文献   
155.
楚州盐穴储气库是中俄东线配套储气库,具有重要建设意义。在楚州地区钻井施工时,上部东台组、盐城组地层易渗漏,粘土易造浆,下部浦口组含盐地层易溶蚀扩径和坍塌。针对楚州地区地层特点和施工难点提出采用分段钻井液技术:一开采用聚合物钻井液,防止表层漏失和坍塌;二开上部采用盐水聚合物钻井液,防止缩径和石膏侵;盐层段采用饱和盐水聚合物钻井液防止盐岩溶解。通过现场3口资料井对上述钻井液技术进行了验证,3口井钻井过程顺利,井径规则,未发生任何井下复杂情况,井身质量较高,盐层段岩心采取率均在99%以上。所形成的钻井液技术对建库钻井具有很好的指导意义。  相似文献   
156.
聚合物驱作为油田开发晚期的一种重要的技术手段,得到了大规模的推广应用。但是目前聚合物驱主要用于中低温、中低盐油藏,而对于很多高温高盐的油田应用比较少,因此,开展适合于高温高盐油藏聚合物的室内实验研究,进而拓宽聚合物驱的应用领域,实现聚合物在高温高盐油藏的实际应用,为聚合物驱在高温高盐油藏的应用和推广提供了技术和实践依据有着非常重要的意义。  相似文献   
157.
地震物理模型材料研制与应用研究   总被引:1,自引:1,他引:0       下载免费PDF全文
地震物理模型试验的基础是地震物理模型的建造,其中设计适当的配方,调配出所需要的模型速度是模型建造的关键.本文根据互穿网络和共聚网络聚合物改性方法的原理,研究了环氧树脂、橡胶类等高分子材料的互穿网络和共聚网络过程,并按照地震物理模拟对模型材料的要求,实现了不同材料的共混,改善了固化后共聚物的交联度.讨论和分析了影响地震物理模型建造的各种因素,并从模型材料选择、配方调整等方面提出了相应的解决办法,降低了固化反应放热峰的温度、调整了固化放热的速度、降低了固化时的收缩率和线膨胀系数,使固化物具有较高的热稳定性和较好的力学性能.建立了比较完备的、从低到高的材料速度系列.通过实例验证了本文方法的有效性,模型材料的适用性.  相似文献   
158.
This paper presents a new type of structural bracing intended for seismic retrofitting use in framed structures. This special composite brace,termed glass-fiber-reinforced-polymer(GFRP)-tube-confined-concrete composite brace,is comprised of concrete confined by a GFRP tube and an inner steel core for energy dissipation.Together with a contribution from the GFRP-tube confined concrete,the composite brace shows a substantially increased stiffness to control story drift, which is often a preferred feature in seismic retrofitting.An analysis model is established and implemented in a general finite element analysis program-OpenSees,for simulating the load-displacement behavior of the composite brace.Using this model,a parametric study of the hysteretic behavior(energy dissipation,stiffness,ductility and strength)of the composite brace was conducted under static cyclic loading and it was found that the area ratio of steel core to concrete has the greatest influence among all the parameters considered.To demonstrate the application of the composite brace in seismic retrofitting, a three-story nonductile reinforced concrete(RC)frame structure was retrofitted with the composite braces.Pushover analysis and nonlinear time-history analyses of the retrofitted RC frame structure was performed by employing a suite of 20 strong ground motion earthquake records.The analysis results show that the composite braces can effectively reduce the peak seismic responses of the RC frame structure without significantly increasing the base shear demand.  相似文献   
159.
This paper presents the results of a parametric study that consists of real‐time hybrid simulation tests of electrical insulator posts on a smart shaking table. A companion paper presents the details of the development and validation of the real‐time hybrid simulation system used for conducting the tests of this parametric study. The purpose of the parametric study presented in this paper is to evaluate the effect of support structure damping and stiffness on the response of disconnect switches with two different insulator materials, namely porcelain and polymer insulator posts. Various global and local response parameters including accelerations, forces, displacements, and strains are considered in this evaluation. The data obtained from the conducted tests show that the maximum insulator response corresponds to the case where the support structure frequency is close to the insulator frequency. An incorporated evaluation of all the response parameters indicates that the stiff support structures constitute the most suitable configuration for both material types of the tested insulator posts. It is also observed that support structure damping has an effect on the response of both insulator types. However, this effect is secondary compared with the effect of support structure stiffness. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
160.
In light of recent earthquakes, structures damaged during an initial seismic event (mainshock) may be more vulnerable to severe damage and collapse during a subsequent event (aftershock). In this paper, a framework for the development of aftershock fragilities is presented; these aftershock fragilities define the likelihood that a bridge damaged during an initial event will exhibit a given damage state following one or more subsequent events. The framework is capable of (i) quantifying the cumulative damage of unrepaired bridges subjected to mainshock–aftershock sequences (effect of multiple earthquakes) and (ii) evaluating the effectiveness of column repair schemes such as steel and fiber‐reinforced‐polymer jackets (post‐repair effect of jackets). To achieve this aim, the numerical model of repaired columns is validated using existing experimental results. A non‐seismically designed bridge is chosen as a case study and is modeled for three numerical bridge models: a damaged (but unrepaired) bridge model, and two bridge models with columns repaired with steel and fiber‐reinforced polymer jackets. A series of back‐to‐back dynamic analyses under successive earthquakes are performed for each level of existing damage. Using simulated results, failure probabilities of components for multiple limit states are computed for each bridge model and then are used to evaluate the relative vulnerability of components associated with cumulative damage and column repair. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号