全文获取类型
收费全文 | 9394篇 |
免费 | 2198篇 |
国内免费 | 766篇 |
专业分类
测绘学 | 63篇 |
大气科学 | 4篇 |
地球物理 | 7389篇 |
地质学 | 3006篇 |
海洋学 | 557篇 |
天文学 | 9篇 |
综合类 | 418篇 |
自然地理 | 912篇 |
出版年
2024年 | 29篇 |
2023年 | 119篇 |
2022年 | 241篇 |
2021年 | 301篇 |
2020年 | 391篇 |
2019年 | 425篇 |
2018年 | 339篇 |
2017年 | 317篇 |
2016年 | 294篇 |
2015年 | 366篇 |
2014年 | 447篇 |
2013年 | 473篇 |
2012年 | 526篇 |
2011年 | 542篇 |
2010年 | 448篇 |
2009年 | 508篇 |
2008年 | 523篇 |
2007年 | 654篇 |
2006年 | 676篇 |
2005年 | 557篇 |
2004年 | 571篇 |
2003年 | 492篇 |
2002年 | 419篇 |
2001年 | 299篇 |
2000年 | 339篇 |
1999年 | 286篇 |
1998年 | 277篇 |
1997年 | 229篇 |
1996年 | 269篇 |
1995年 | 209篇 |
1994年 | 198篇 |
1993年 | 178篇 |
1992年 | 110篇 |
1991年 | 69篇 |
1990年 | 50篇 |
1989年 | 51篇 |
1988年 | 43篇 |
1987年 | 31篇 |
1986年 | 24篇 |
1985年 | 7篇 |
1984年 | 1篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 16篇 |
1954年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
David K. Keefer 《Surveys in Geophysics》2002,23(6):473-510
Post-earthquake field investigations of landslide occurrence have provided a basis for understanding, evaluating, and mapping the hazard and risk associated withearthquake-induced landslides. This paper traces thehistorical development of knowledge derived from these investigations. Before 1783, historical accounts of the occurrence of landslides in earthquakes are typically so incomplete and vague that conclusions based on these accounts are of limited usefulness. For example, the number of landslides triggered by a given event is almost always greatly underestimated. The first formal, scientific post-earthquake investigation that included systematic documentation of the landslides was undertaken in the Calabria region of Italy after the 1783 earthquake swarm. From then until the mid-twentieth century, the best information on earthquake-induced landslides came from a succession ofpost-earthquake investigations largely carried out by formal commissions that undertook extensive ground-based field studies. Beginning in the mid-twentieth century, when the use of aerial photography became widespread, comprehensive inventories of landslide occurrence have been made for several earthquakes in the United States, Peru, Guatemala, Italy, El Salvador, Japan, and Taiwan. Techniques have also been developed for performing ``retrospective' analyses years or decades after an earthquake that attempt to reconstruct the distribution of landslides triggered by the event. The additional use of Geographic Information System (GIS) processing and digital mapping since about 1989 has greatly facilitated the level of analysis that can applied to mapped distributions of landslides. Beginning in 1984, syntheses of worldwide and national data on earthquake-induced landslides have defined their general characteristics and relations between their occurrence and various geologic and seismic parameters. However, the number of comprehensive post-earthquake studies of landslides is still relatively small, and one of the most pressing needs in this area of research is for the complete documentation of landslides triggered by many more earthquakes in a wider variety of environments. 相似文献
82.
Nonlinear earthquake response analysis and energy calculation for seismic slit shear wall structures
Based on the concept of structural passive control, a new type of slit shear wall, with improved seismic performance when
compared to an ordinary solid shear wall, was proposed by the authors in 1996. The idea has been verified by a series of pseudo-static
and dynamic tests. In this paper a macro numerical model is developed for the wall element and the energy dissipation device.
Then, nonlinear time history analysis is carried out for a 10-story slit shear wall model tested on a shaking table. Furthermore,
the seismic input energy and the individual energy dissipated by the components are calculated by a method based on Newmark-β
assumptions for this shear wall model, and the advantages of this shear wall are further demonstrated by the calculation results
from the viewpoint of energy. Finally, according to the seismic damage criterion on the basis of plastic accumulative energy
and maximum response, the optimal analysis is carried out to select design parameters for the energy dissipation device. 相似文献
83.
上海地震台阵的地震定位方法 总被引:5,自引:0,他引:5
详细介绍了上海地震台阵数据处理软件系统中的地震定位方法,用台阵的聚束方法得到地震的方位角和视慢度,根据统计得到的视慢度-震中距表推算震中距。并结合了地震台网的定位方法,由单台记录的各类主要震相从J-B走时表得到震中距,然后进行地震定位。该定位方法可对近震、远震进行定位处理,并由深震相得到震源深度。 相似文献
84.
85.
Seismic structural control using semi-active tuned mass dampers 总被引:8,自引:1,他引:8
This paper focuses on how to determine the instantaneous damping of the semi-active tuned mass damper (SATMD) with continuously
variable damping. An off-and-towards-equilibrium (OTE) algorithm is employed to examine the control performance of the structure/SATMD
system by considering the damping as an assumptive control action. The damping modification of the SATMD is carried out according
to the proposed OTE algorithm, which is formulated based on analysis of the structural movement under external excitations,
and the measured responses of the structure at every time instant. As examples two numerical simulations of a five-storey
and a ten-storey shear structures with a SATMD on the roof are conducted. The effectiveness on vibration reduction of MDOF
systems subjected to seismic excitations is discussed. Analysis results show that the behavior of the structure with a SATMD
is significantly improved and the feasibility of applying the OTE algorithm to the structural control design of SATMD is also
verified. 相似文献
86.
87.
88.
89.
90.
Yan Y. Kagan 《Geophysical Journal International》2002,149(3):731-754