全文获取类型
收费全文 | 173篇 |
免费 | 30篇 |
国内免费 | 31篇 |
专业分类
测绘学 | 53篇 |
大气科学 | 8篇 |
地球物理 | 32篇 |
地质学 | 83篇 |
海洋学 | 31篇 |
天文学 | 4篇 |
综合类 | 16篇 |
自然地理 | 7篇 |
出版年
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 3篇 |
2017年 | 9篇 |
2016年 | 7篇 |
2015年 | 8篇 |
2014年 | 15篇 |
2013年 | 19篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 13篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2005年 | 12篇 |
2004年 | 8篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1991年 | 4篇 |
1989年 | 3篇 |
1986年 | 1篇 |
排序方式: 共有234条查询结果,搜索用时 15 毫秒
21.
Numerous studies have been devoted to the performance of excavations and adjacent facilities. In contrast, few studies have focused on retaining wall deflections induced by pre-excavation dewatering. However, considerable inward cantilever deflections were observed for a diaphragm wall in a pre-excavation dewatering test based on a long and narrow metro excavation, and the maximum deflection reached 10 mm (37.6% of the allowable wall deflection for the project). Based on the test results, a three-dimensional soil–fluid coupled finite element model was established and used to study the mechanism of the dewatering-induced diaphragm wall deflections. Numerical results indicated that the diaphragm wall deflection results from three factors: (1) the seepage force around the dewatering well and the soil–wall interaction caused the inward horizontal displacement of the soil inside the excavation; (2) the reduced total earth pressure on the excavated side of the diaphragm wall above approximately 1/2 of the maximum dewatering depth disequilibrated the original earth pressure on both sides of the diaphragm wall; and (3) the different negative friction on the excavated and retained sides of the diaphragm wall led to the rotation of the diaphragm wall into the excavation. 相似文献
22.
张赤军 《大地测量与地球动力学》2002,22(4):31-34
介绍当今确定天文大地垂偏差的新仪器-CCD自动天体测量仪和确定两点间高程异常差的新方法,该方法用单极坐标代替繁琐的双极坐标进行计算,讨论了天文重力水准的误差及垂线偏差非线性影响等问题,估计在不久的将来,用这一手段施测山区似大地水准面的精度可望达到厘米级。 相似文献
23.
24.
The lateral deflection of a cylindrical diaphragm wall and the associated ground movement induced by deep excavation are analyzed by performing site instrumentations and numerical analyses in the coastal area of Korea. Wall lateral deflection, rebar stress, and pore water pressure were measured and analyzed in eight directions. Variations of soil properties with the decrease of confining pressure are compared by performing various in situ tests before ad after excavation. To calculate the wall lateral deflection accurately, the effects of small strain nonlinearity, confining pressure, and the hysteresis loading/unloading loop developed during excavation are considered in the proposed numerical analysis. By comparing numerical results with measured ones, the importances of considering small strain nonlinearity and confining pressure reduction in the nonlinear (FEM) are emphasized. Also, the effects of wall stiffness on the performance of cylindrical diaphragm walls are studied for future similar excavation in the coastal area. 相似文献
25.
26.
An embedded cylinder is a large-diameter cylinder embedded in a soil foundation. The state of failure of such an embedded cylindrical structure shows large deflection instead of slide and overturn of the traditional gravity type of structure placed on a rubble base or foundation base. The critical value of deflection of the embedded cylindrical structure, which is the maximum allowable deflection for stability calculation of the cylinder, is a vital control value. Through investigation on deflection and soil pressures on an embedded cylinder by model experiments, the variations of the angle of rotation θ of a cylinder with effective anti-overturning ratio η and moment MH of thrust are discussed. On the basis of experimental study, the critical value of deflection of the cylindrical structure is proposed in the paper. Meanwhile, the formulas for calculating deflection of cylinders are derived. 相似文献
27.
28.
中国近40年日平均气温的概率分布特征及年代际差异 总被引:1,自引:0,他引:1
利用全国129站日平均气温资料,从偏态系数、峰度系数入手分析了日平均气温的概率分布特征及年代际差异,结果表明:近40年中国各季日平均气温的均值分布大致呈南高北低,夏季日平均气温的日际变化最小,四季日平均气温不服从正态分布的地理差异明显。1961~1975年时段至1976~2000年时段,夏季、春季日平均气温不服从正态分布的范围明显加大,冬季不服从正态分布范围,北部加大,南部减小,秋季与冬季大致相反;在夏、春、秋季日平均气温方差的变化对日平均气温概率分布的影响是主要的,均值变化的影响次之,冬季在黄河中下游和长江下游流域均值的变化对概率分布影响是主要的,方差变化影响次之,其他地区相反。 相似文献
29.
30.
挠曲线复位的微分方程解法求梁的位移 总被引:5,自引:0,他引:5
喻晓今 《华东地质学院学报》2003,26(3):271-273
梁位移求解的方法主要有两种:积分法和叠加法。积分法的困难是当多个荷载同时作用时,要按控制面分段列弯矩方程,这样,两次积分时带来的积分常数较多,导致依边界条件、连续条件定这些常数时要解多个联立方程,计算繁杂。梁位移求解的叠加法是借用典型荷载下梁已知积分结果来进行对应位置位移的叠加,具体是查转角方程、挠曲线方程表格。从表中知,梁任一位置处的位移方程大多是多次多项式,很难记忆,故离开表格便无法采用。本文找到了一种新的方法求梁的位移,通过设置比拟梁,使比拟梁的挠曲线复位于原梁,从而建立了相应的微分方程,求解此方程后便可得梁的位移,避开了分段多次积分或查表的弱点。 相似文献