全文获取类型
收费全文 | 1646篇 |
免费 | 460篇 |
国内免费 | 175篇 |
专业分类
测绘学 | 225篇 |
大气科学 | 34篇 |
地球物理 | 1142篇 |
地质学 | 542篇 |
海洋学 | 176篇 |
天文学 | 37篇 |
综合类 | 83篇 |
自然地理 | 42篇 |
出版年
2024年 | 5篇 |
2023年 | 18篇 |
2022年 | 52篇 |
2021年 | 75篇 |
2020年 | 90篇 |
2019年 | 88篇 |
2018年 | 69篇 |
2017年 | 69篇 |
2016年 | 60篇 |
2015年 | 85篇 |
2014年 | 112篇 |
2013年 | 95篇 |
2012年 | 147篇 |
2011年 | 129篇 |
2010年 | 114篇 |
2009年 | 121篇 |
2008年 | 101篇 |
2007年 | 134篇 |
2006年 | 104篇 |
2005年 | 121篇 |
2004年 | 84篇 |
2003年 | 79篇 |
2002年 | 74篇 |
2001年 | 54篇 |
2000年 | 37篇 |
1999年 | 28篇 |
1998年 | 22篇 |
1997年 | 24篇 |
1996年 | 22篇 |
1995年 | 16篇 |
1994年 | 19篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1981年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2281条查询结果,搜索用时 31 毫秒
41.
探讨了45Mn2钻杆接头的各种热处理工艺降综合机械性能,应用断裂力学优选最佳热处理工艺,并已投入生产。 相似文献
42.
本文介绍了对钢板桩码头岸壁进行的原体观测试验,通过观测钢板桩的挠度、作用在钢板桩上的土压力以及拉杆轴向拉力,可以了解板桩岸壁在回填土的作用下,其结构各主要部分的受力及变形情况,为今后同类型结构的合理分析和设计以及港口工程技术规范有关条文的编制,提供了实测资料。 相似文献
43.
44.
45.
福建及台湾海峡地震预警工程架构探索 总被引:2,自引:0,他引:2
福建及台湾海峡是海陆板块碰撞到板内地震活动过渡带 ,东侧毗邻台湾板缘地震带 ,西侧为福建内陆板内地震活动区。这是得天独厚的观测研究大陆边缘地震构造带强震活动及板块动力学的良好地域。当前 ,我国进入全面建设小康社会历史时期 ,为防御地震造成社会灾害 ,实现以人为本 ,防患于未然 ,势必需要建构一个实用化的地震预警工程及其机制。本文即是在对福建及台湾海峡近 30多年以来观测研究的基础上 ,提出应用现代空间技术、数字地震、计算机网络等技术架构地震预警工程与机制的一种设想。 相似文献
46.
47.
结合某一工程实例 ,探讨钻孔灌注桩先成桩后插钢筋笼法的施工工艺以及配套装置的工作原理、性能特点、适用范围和施工方法 相似文献
48.
In this study the inelastic behavior of steel arch bridges subjected to strong ground motions from major earthquakes is investigated by dynamic analyses of a typical steel arch bridge using a three‐dimensional (3D) analytical model, since checking seismic performance against severe earthquakes is not usually performed when designing such kinds of bridge. The bridge considered is an upper‐deck steel arch bridge having a reinforced concrete (RC) deck, steel I‐section girders and steel arch ribs. The input ground motions are accelerograms which are modified ground motions based on the records from the 1995 Hyogoken‐Nanbu earthquake. Both the longitudinal and transverse dynamic characteristics of the bridge are studied by investigation of time‐history responses of the main parameters. It is found that seismic responses are small when subjected to the longitudinal excitation, but significantly large under the transverse ground motion due to plasticization formed in some segments such as arch rib ends and side pier bases where axial force levels are very high. Finally, a seismic performance evaluation method based on the response strain index is proposed for such steel bridge structures. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
49.
50.
Liza Tonkin 《The Australian geographer》2004,35(1):59-75
Place‐based action (PBA) features prominently in labour geographies, particularly in restructuring politics, and is consistently employed as an enduring union tactic, yet it remains relatively undervalued in steel restructuring accounts, with common approaches emphasising the class instability and limitations of such action. In contrast, and to redress the apparent imbalance, this paper argues the merit of recognising PBA as a distinct movement‐based politic with specific forms of representation and empowerment. Such an approach should lead to greater recognition and appreciation of the impact that PBA has had historically. To illustrate this, a case study is presented of how local groups used place‐based action in Wollongong to shape steel restructuring politics and industry policy during the 1980s. Although powerful, the influence of PBA diminished at the policy writing stage. Rather than devaluing all benefits from PBA due to such limitations, it is suggested that the constraints on PBA at this point suggests the need for other forms of intervention. It is concluded that the approach suggested here highlights when other tactics are required, strengthening real‐world tactical analysis. 相似文献