全文获取类型
收费全文 | 11639篇 |
免费 | 2988篇 |
国内免费 | 2517篇 |
专业分类
测绘学 | 225篇 |
大气科学 | 303篇 |
地球物理 | 4730篇 |
地质学 | 8663篇 |
海洋学 | 1239篇 |
天文学 | 18篇 |
综合类 | 928篇 |
自然地理 | 1038篇 |
出版年
2024年 | 37篇 |
2023年 | 121篇 |
2022年 | 308篇 |
2021年 | 442篇 |
2020年 | 405篇 |
2019年 | 553篇 |
2018年 | 468篇 |
2017年 | 512篇 |
2016年 | 563篇 |
2015年 | 550篇 |
2014年 | 683篇 |
2013年 | 726篇 |
2012年 | 683篇 |
2011年 | 683篇 |
2010年 | 621篇 |
2009年 | 792篇 |
2008年 | 811篇 |
2007年 | 798篇 |
2006年 | 779篇 |
2005年 | 665篇 |
2004年 | 704篇 |
2003年 | 587篇 |
2002年 | 547篇 |
2001年 | 493篇 |
2000年 | 494篇 |
1999年 | 400篇 |
1998年 | 398篇 |
1997年 | 339篇 |
1996年 | 332篇 |
1995年 | 331篇 |
1994年 | 292篇 |
1993年 | 246篇 |
1992年 | 194篇 |
1991年 | 127篇 |
1990年 | 104篇 |
1989年 | 113篇 |
1988年 | 78篇 |
1987年 | 56篇 |
1986年 | 26篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 8篇 |
1980年 | 4篇 |
1979年 | 23篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1954年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
102.
基于EMD与神经网络的机械故障诊断技术 总被引:2,自引:0,他引:2
经验模式分解 (EMD)是分析非线性、非平稳信号的有力工具 ,它将信号分解为突出了原信号的不同时间尺度的局部特征信息的内在模函数 (IMF)分量。本文通过将各 IMF分量输入到 BP网络中进行训练学习和故障诊断 ,比直接输入原信号可以提高 BP网络对故障诊断的准确率 ,而且减少了训练时间。 相似文献
103.
东海陆架外缘隆起带地质构造特征 总被引:1,自引:0,他引:1
根据地质、地球物理及钻探资料,结合周边区域地质资料,论证东海外缘隆起带前中中新世基底岩系组成及地质构造特征。 相似文献
104.
以 CG2 0潜山为例 ,从建立地质模型入手 ,包括地层模型、构造模型、储集模型、储盖组合模型、速度模型等 ,认识到各套地层分布和储层物性的差异均与地震响应密切相关 ,因此可以利用地震波的信息 ,预测潜山储层的发育及分布情况。在对 CG2 0潜山进行精细全三维构造解释的基础上 ,探讨性地应用了测井约束反演、吸收系数、相干分析及三维模式识别等技术 ,对潜山储层进行了预测 ,从而提高了潜山勘探的效益 ,并为类似断阶型潜山带的勘探提供了成功的经验 ,具有一定的指导意义。 相似文献
105.
Robert P. Dziak Christopher G. Fox Robert W. Embley 《Marine Geophysical Researches》1991,13(3):203-208
Morphologic studies of an oceanic transform, the Blanco Transform Fault Zone (BTFZ), have shown it to consist of a series of extensional basins that offset the major strike-slip faults. The largest of the extensional basins, the Cascadia Depression, effectively divides the transform into a northwest segment, composed of several relatively short strike-slip faults, and a southeast segment dominated by fewer, longer faults. The regional seismicity distribution (m
b
4.0) and frequency-magnitude relationships (b-values) of the BTFZ show that the largest magnitude events are located on the southeast segment. Furthermore, estimates of the cumulative seismic moment release and seismic moment release rate along the southeast segment are significantly greater than that of the northwest segment. These observations suggest that slip along the southeast segment is accommodated by a greater number of large magnitude earthquakes. Comparison of the seismic moment rate, derived from empirical estimates, with the seismic moment rate determined from plate motion constraints suggests a difference in the seismic coupling strength between the segments. This difference in coupling may partially explain the disparity in earthquake size distribution. However, the results appear to confirm the relation between earthquake size and fault length, observed along continental strike-slip faults, for this oceanic transform. 相似文献
106.
首次对浙北潮下带(0~-5m)水域生物学调查表明:共鉴定底栖生物222种,隶属103科170属;该区生物数量较高(生物量为80.88g/m2,栖息密度为655个/m2),以软体动物为主要类群;群落结构可划分为五个类型。底栖生物的分布与水域盐度、温度、底质性质、海湾屏蔽度有密切的关系。 相似文献
107.
Shigehisa Nakamura 《Marine Geodesy》2005,28(4):305-312
A note is presented on tsunami bore front. This tsunami bore front is an old dynamical problem but also a new problem to be understood. The tsunami event on 2004 December 26 has raised this is an urgent problem. The author introduces here a model in order to see a hydrodynamical specific property of the tsunami bore front. This modeling gives us a new understanding about what mechanics is for the interested tsunami bore front, especially, around a coastal zone. This work adds a new understanding about mechanics of water motions as the tsunamis generated by the earthquake undersea at a distant area from the coast. The model in this work points out a specific transitional pattern as a function of time and space of tsunami bore front. This modeling gives what is essential at considering tsunami bore front. 相似文献
108.
In the present study, a methodology for reliability assessment of slack and taut mooring systems against instability has been presented. For this purpose, first, stability analysis of slack and taut mooring systems has been carried out and instable regions are obtained using procedure available in the literature. Having known the instable region(s), methodology for reliability assessment has been proposed which is based on Monte Carlo Simulation technique. After using the proposed methodology, probabilities of failure and reliability indices has been obtained for the above systems. Some parametric studies, such as, effect of lower and upper limits of instability and effect of frequency range of generations are also included to obtain the results of practical interest. 相似文献
109.
Since the beginning of formation of Proto-Taiwan, the subducting Philippine (PH) Sea plate has moved continuously through
time in the N307° direction with respect to Eurasia (EU), tearing the EU plate. The subducting EU plate includes a continental
part in the north and an oceanic part in the south. The boundary B between these two domains corresponds to the eastern prolongation
of the northeastern South China Sea ocean-continent transition zone. In the Huatung Basin (east of Taiwan), the Taitung Canyon
is N065° oriented and is close and parallel to B. Seismic profiles show that the southern flank of the canyon corresponds
to a fault with a normal component of a few tens of meters in the sediments and possible dextral shearing. Several crustal
earthquakes of magnitude >%6 are located beneath the trend of the Taitung Canyon and focal mechanisms suggest that the motion
is right-lateral. Thus, faulting within the sedimentary sequence beneath the Taitung Canyon is a consequence of underlying
dextral strike-slip crustal motions. As the continental part of the EU slab located north of B has been recently detached,
some subsequent dextral strike-slip motion might be expected within the EU slab, along the ocean-continent transition zone,
which is a potential zone of weakness. We suggest that the dextral strike-slip motion along the ocean-continent boundary of
the EU slab might trigger the observed dextral strike-slip motion within the overlying PH Sea crust and the associated faulting
within the sediments of the Huatung Basin, beneath the Taitung Canyon.
An erratum to this article is available at . 相似文献
110.
Various offshore structures, especially large structures such as Tension Leg Platforms (TLP), are usually supported by concrete piles as the foundation elements. The stress distribution within such a large structure is a dominant factor in the design procedure of an offshore pile. To provide a more accurate and effective design for offshore foundation systems under axial and lateral wave loads, a finite element model is employed herein to determine the stresses and displacements in a concrete pile under similar loading conditions. A parametric study is also performed to examine the effects of the stress distribution due to the changing loading conditions. 相似文献