全文获取类型
收费全文 | 12427篇 |
免费 | 2958篇 |
国内免费 | 1318篇 |
专业分类
测绘学 | 512篇 |
大气科学 | 703篇 |
地球物理 | 8352篇 |
地质学 | 3792篇 |
海洋学 | 772篇 |
天文学 | 833篇 |
综合类 | 732篇 |
自然地理 | 1007篇 |
出版年
2024年 | 35篇 |
2023年 | 109篇 |
2022年 | 316篇 |
2021年 | 403篇 |
2020年 | 476篇 |
2019年 | 564篇 |
2018年 | 444篇 |
2017年 | 443篇 |
2016年 | 410篇 |
2015年 | 524篇 |
2014年 | 648篇 |
2013年 | 663篇 |
2012年 | 730篇 |
2011年 | 803篇 |
2010年 | 653篇 |
2009年 | 798篇 |
2008年 | 738篇 |
2007年 | 895篇 |
2006年 | 913篇 |
2005年 | 763篇 |
2004年 | 757篇 |
2003年 | 667篇 |
2002年 | 543篇 |
2001年 | 416篇 |
2000年 | 436篇 |
1999年 | 388篇 |
1998年 | 357篇 |
1997年 | 296篇 |
1996年 | 316篇 |
1995年 | 245篇 |
1994年 | 253篇 |
1993年 | 207篇 |
1992年 | 141篇 |
1991年 | 79篇 |
1990年 | 63篇 |
1989年 | 59篇 |
1988年 | 50篇 |
1987年 | 31篇 |
1986年 | 24篇 |
1985年 | 9篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 18篇 |
1978年 | 2篇 |
1954年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Analytical study of ground motion caused by seismic wave propagation across faulted rock masses
下载免费PDF全文
![点击此处可从《国际地质力学数值与分析法杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Studying seismic wave propagation across rock masses and the induced ground motion is an important topic, which receives considerable attention in design and construction of underground cavern/tunnel constructions and mining activities. The current study investigates wave propagation across a rock mass with one fault and the induced ground motion using a recursive approach. The rocks beside the fault are assumed as viscoelastic media with seismic quality factors, Qp and Qs. Two kinds of interactions between stress waves and a discontinuity and between stress waves and a free surface are analyzed, respectively. As the result of the wave superposition, the mathematical expressions for induced ground vibration are deduced. The proposed approach is then compared with the existing analysis for special cases. Finally, parametric studies are carried out, which includes the influences of fault stiffness, incident angle, and frequency of incident waves on the peak particle velocities of the ground motions. 相似文献
2.
3.
4.
5.
6.
在GPS数据处理中 ,存在着误差影响、影响波的干扰、周跳和数据量大等问题。误差影响和影响波的干扰实质是在接收卫星信号时受到其它因素的影响 ;周跳是由于卫星信号的失锁而造成信号的不连续 ;数据量大是因为GPS观测需要采样间隔小又连续观测所致。由于小波理论具有时频分析、波形分解、特征提取和快速小波变换等特性 ,应用小波变换和波形分解可以解决误差影响和影响波的干扰的问题 ;应用特征提取可以解决周跳检测问题 ;应用快速小波变换可进行数据压缩 相似文献
7.
8.
9.
小行星自转参数的资料不仅可以为小行星碰撞演化提供数据,还可以为太阳系的演化研究提供依据.利用云南天文台1米望远镜对主带碳类小行星(360)Carlova进行了新的CCD测光观测,结合前人的测光资料,利用Epoch-方法对(360)的自转参数进行了反演计算,得到该小行星自转的恒星周期为0.25780417±0.00000003天,自转轴的黄道坐标为(95°±3,°40°±1°).新的结果与前人的结果相比较为一致,其精度稍高于以前的估算结果. 相似文献
10.
Massimo Dotti Monica Colpi Francesco Haardt 《Monthly notices of the Royal Astronomical Society》2006,367(1):103-112
We study the inspiral of double black holes, with masses in the Laser Interferometer Space Antenna ( LISA ) window of detectability, orbiting inside a massive circumnuclear, rotationally supported gaseous disc. Using high-resolution smoothed particle hydrodynamics simulations, we follow the black hole dynamics in the early phase when gas-dynamical friction acts on the black holes individually, and continue our simulation until they form a close binary. We find that in the early sinking the black holes lose memory of their initial orbital eccentricity if they corotate with the gaseous disc. As a consequence, the massive black holes bind forming a binary with a low eccentricity, consistent with zero within our numerical resolution limit. The cause of circularization resides in the rotation present in the gaseous background where dynamical friction operates. Circularization may hinder gravitational waves from taking over and leading the binary to coalescence. In the case of counter-rotating orbits, the initial eccentricity (if present) does not decrease, and the black holes may bind forming an eccentric binary. When dynamical friction has subsided, for equal mass black holes and regardless their initial eccentricity, angular momentum loss, driven by the gravitational torque exerted on the binary by surrounding gas, is nevertheless observable down to the smallest scale probed (≃1 pc). In the case of unequal masses, dynamical friction remains efficient down to our resolution limit, and there is no sign of formation of any ellipsoidal gas distribution that may further harden the binary. During inspiral, gravitational capture of gas by the black holes occurs mainly along circular orbits; eccentric orbits imply high relative velocities and weak gravitational focusing. Thus, the active galactic nucleus activity may be excited during the black hole pairing process and double active nuclei may form when circularization is completed, on distance scales of tens of parsecs. 相似文献