全文获取类型
收费全文 | 567篇 |
免费 | 133篇 |
国内免费 | 150篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 85篇 |
地球物理 | 152篇 |
地质学 | 325篇 |
海洋学 | 146篇 |
天文学 | 10篇 |
综合类 | 42篇 |
自然地理 | 79篇 |
出版年
2024年 | 7篇 |
2023年 | 15篇 |
2022年 | 28篇 |
2021年 | 31篇 |
2020年 | 21篇 |
2019年 | 36篇 |
2018年 | 20篇 |
2017年 | 23篇 |
2016年 | 22篇 |
2015年 | 29篇 |
2014年 | 30篇 |
2013年 | 46篇 |
2012年 | 37篇 |
2011年 | 28篇 |
2010年 | 28篇 |
2009年 | 32篇 |
2008年 | 35篇 |
2007年 | 42篇 |
2006年 | 51篇 |
2005年 | 35篇 |
2004年 | 26篇 |
2003年 | 25篇 |
2002年 | 25篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 23篇 |
1998年 | 9篇 |
1997年 | 17篇 |
1996年 | 17篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1983年 | 2篇 |
排序方式: 共有850条查询结果,搜索用时 15 毫秒
41.
岩石变形所反映的地震作用过程--第13届国际变形机理、流变学和构造学学术会议概述 总被引:2,自引:0,他引:2
简要介绍了第13届国际变形机理、流变学和构造学学术会议的概况和特点,综述了地震变形作用的研究现状。 相似文献
42.
Evert Lagrou 《GeoJournal》2000,51(1-2):99-112
The paper describes the different capital city functions that are accomodated in Brussels. There are in fact five different capitals in Brussels in search of a place. Their locations are conditioned by Brussels' eventful history. The analysis subsequently focuses on the rather negative relation between the local public intellectuals and the city's European capital functions. The location of the European headquarters within the existing urban fabric – unlike Luxemburg and Strasbourg – has caused residential expulsion and further confrontations with the local community during all expansions.Brussels has the most politically decisive institutions. The competition with Luxemburg and Strasbourg has in the past given rise to dubious building processes and hidden agendas regarding the further construction of the necessary space for Europe.Unlike most other capitals Brussels has a low degree of esteem from its citizens. The After-May 68- Movement reacting initially against the CIAM-realisations during the 1970s, continues its activities up until today against two highly symbolic projects: the North Station area called the Manhattan Quarter and the European Headquarters. The movement launched the term Brusselization on the international forum and continues to promote the negative image of its city – notwithstanding the complete change of the official urban planning.The article is a plea for the integration of the actual one-sided advocacy planning within a more comprehensive urban planning approach where strong and soft functions are more in balance. This can also improve the quality of the new European campus now under consideration to accomodate the entry of the East European states in the Union. 相似文献
43.
Sarah Wright 《The Australian geographer》2014,45(1):1-18
For those interested in ethical research, quantitative methods are often dismissed as apolitical; as unreflective exercises in ‘mere counting’. If, however, in doing research, we bring into being the very worlds we purport to describe, the question begs: what kinds of worlds might quantitative methods bring into being? Is there space for a reflexive, quantitative research agenda? In this paper, I will discuss an action-based predominantly quantitative research project that aimed to investigate the diverse impacts of sustainable agriculture on small-scale farmers in the Philippines. The study, one of the largest ever undertaken on organic rice production, was consciously designed, not merely to describe, but to perform organic agriculture differently. While most quantitative, and indeed much qualitative, research ignores its performativity, this research was intended to enact a reality of sustainable agriculture as a viable and vital alternative to mainstream, capitalist agriculture. 相似文献
44.
冀中拗陷油气田87%的储量产于海相碳酸盐岩古潜山中,在油气生成、运移、集聚和散失的过程中地下水起了重要作用。本文根据50个试样的水化学分析资料,运用对应分析方法对冀中拗陷古潜山油田水进行了分类并初步探讨了水化学成分演化与油气藏形成的关系。 相似文献
45.
Cheryl E. Morse 《社会与自然资源》2019,32(2):150-166
The term “working landscape” (WL) is increasingly used by American planners and policy makers to describe the rural places and livelihoods they aim to shape. This paper draws from a mixed-methods study of WL language as a collective action frame in the state of Vermont, where WL has been formalized into policy. Natural resource leaders and professionals share a common definition of WL that is supported by four key beliefs. However, interviews conducted in two representative farming communities suggest that landuse practitioners have not adopted WL language, and in some cases are skeptical of its meaning. The analysis explores potential explanations for the failure of the WL collective action frame to resonate across scales. The paper argues for a bottom-up planning approach that produces working landscapes policies that allow for diverse forms of work and accommodate the specificities of place. 相似文献
46.
LI Benxia YU Xiping YU Yuxiu 《海洋学报(英文版)》2006,25(1):147-153
A three-dimensional numerical model based on the potential theory was developed to study the oblique wave action on vertical walls. A source term inside the domain was used to generate incident waves and outgoing waves were dissipated by sponge layers and transmitted by radiation boundaries. The finite difference method was used to solve the governing equations and boundary conditions in the regular transformed domain in σ-coordinate. Satisfactory agreements between the numerical predictions and experimental results of wave force were obtained. It is concluded that the maximum wave force acting on the vertical walls is induced by the obliquely incident waves rather than the normally incident waves. 相似文献
47.
地震作用对琼州海峡海缆路由区海底稳定性影向的分析 总被引:1,自引:0,他引:1
以琼州海峡的北海—临高段海缆路由为例,利用计算对比的方法,分析了地震作用下,路由区3m以浅海底土液化或滑移的可能性,评价了路由区海底的稳定性。结果发现,在地震烈度为Ⅶ度的地震作用下,砂性土海底的地震剪应力平均值(0.86kPa,1.72kPa和2.57kPa)小于砂性土的液化剪应力(1.60kPa,3.20kPa和4.81kPa);粘性土海底的地震剪应力平均值(1.25kPa,2.49kPa和3.74kPa)小于粘性土的抗滑剪应力平均值(4.07kPa,4.61kPa和4.49kPa),路由区海底稳定性良好;在地震烈度为Ⅷ度的地震作用下,砂性土海底的地震剪应力平均值(1.73kPa,3.45kPa和5.12kPa)大于砂性土的液化剪应力;粘性土海底的地震剪应力平均值(2.49kPa,4.98kPa和7.47kPa)除表层外,大于粘性土的抗滑剪应力,路由区海底会发生失稳破坏。 相似文献
48.
为减轻海上风电单桩基础周围局部冲刷对其结构安全的影响,提出了一种新型旋转减冲装置。在波流水槽中开展物理模型试验,改变波流条件、装置安装高度、安装距离,记录桩周冲刷发展历时,运用激光地形仪扫描冲刷坑形态,分析各工况下冲刷坑形态差异,验证装置不同安装距离、安装高度下的冲刷防护效果,提出了不同安装位置下的防护效率公式。结果表明:新型旋转减冲装置具有较好的冲刷防护效果,本试验工况下,桩周最大冲刷深度可减小44%左右。装置安装距离对冲刷防护效果影响较小,波流作用下的冲刷防护效果受装置安装高度影响显著,冲刷防护效果随装置安装高度的增加而减弱。 相似文献
49.
长江三峡巴东复杂斜坡系统成因研究 总被引:9,自引:0,他引:9
三峡库区巴东县新城区所在的扇形大斜坡是一个复杂斜坡系统。斜坡后缘边界的挤压变形带是斜坡整体沿其底界面(T1j^3-T2b^1)之间岩层界面向长江发生重力蠕滑作用的结果,不存在“巴东断裂”问题。斜坡系统内部未发现成规模的褶皱,也不存在数量众多的内动力成因的断裂带。巴东斜坡区浅表生变形破坏类型可概括为侧向拉裂、“雪崩式”垮塌、表层风化、侧向滑移张剪破裂、岩层折断变位、软岩膝折剪破裂和压扭破裂又重胶结7种重力卸荷破坏力学模式。斜坡系统内部发育分期分区(块)滑动(滑坡)现象,但不存在构造地质意义上的“断层”形迹。在地貌形态上,巴东大斜坡被4条冲沟分割成5个斜坡单元。在斜坡地质结构、成因类型与空间分布上,巴东大斜坡可划分为3个层次,即表层崩塌滑坡成因为主的堆积层(第一层次),冲沟分割且浅表生地质形迹发育的层状顺倾的中间基岩层(第二层次)和整体连续顺倾的深层基岩层(第三层次)。分形几何计算证明,巴东大斜坡的地貌形态尚处于侵蚀发育的青(幼)年期。FLAC^3D数值模拟发现,在长江侵蚀下切的不同阶段,巴东斜坡体前缘和后缘接近底界面位置塑性变形区分布集中,但不具备沿深层界面发生整体滑动剪出的可能性。基本认识是,“巴东复杂斜坡系统”是在官渡口-东瀼口向斜南翼(单斜山)的地质背景下,持续经受长江快速侵蚀下切外动力作用,河谷岸坡快速临空导致其自身重力产生强烈的侧向卸荷与滑移等浅表生地质改造作用过程而形成的,可简单地概括为“重力成因论”。 相似文献
50.
How the Method of Minimization of Action Avoids Singularities 总被引:4,自引:0,他引:4
C. Marchal 《Celestial Mechanics and Dynamical Astronomy》2002,83(1-4):325-353
The method of minimization of action is a powerful technique of proving the existence of particular and interesting solutions of the n-body problem, but it suffers from the possible interference of singularities. The minimization of action is an optimization and, after a short presentation of a few optimization theories, our analysis of interference of singularities will show that:(A) An n-body solution minimizing the action between given boundary conditions has no discontinuity: all n-bodies have a continuous and bounded motion and thus all eventual singularities are collisions;(B) A beautiful extension of Lambert's theorem shows that, for these minimizing solutions, no double collision can occur at an intermediate time;(C) The proof can be extended to triple and to multiple collisions. Thus, the method of minimization of action leads to pure n-body motions without singularity at any intermediate time, even if one or several collisions are imposed at initial and/or final times.This method is suitable for non-infinitesimal masses only. Fortunately, a similar method, with the same general property with respect to the singularities, can be extended to n-body problems including infinitesimal masses. 相似文献