全文获取类型
收费全文 | 12342篇 |
免费 | 2646篇 |
国内免费 | 1063篇 |
专业分类
测绘学 | 918篇 |
大气科学 | 244篇 |
地球物理 | 8004篇 |
地质学 | 4113篇 |
海洋学 | 942篇 |
天文学 | 55篇 |
综合类 | 616篇 |
自然地理 | 1159篇 |
出版年
2024年 | 19篇 |
2023年 | 85篇 |
2022年 | 270篇 |
2021年 | 351篇 |
2020年 | 424篇 |
2019年 | 537篇 |
2018年 | 402篇 |
2017年 | 430篇 |
2016年 | 381篇 |
2015年 | 464篇 |
2014年 | 597篇 |
2013年 | 683篇 |
2012年 | 729篇 |
2011年 | 785篇 |
2010年 | 604篇 |
2009年 | 730篇 |
2008年 | 748篇 |
2007年 | 878篇 |
2006年 | 904篇 |
2005年 | 736篇 |
2004年 | 737篇 |
2003年 | 635篇 |
2002年 | 506篇 |
2001年 | 397篇 |
2000年 | 446篇 |
1999年 | 364篇 |
1998年 | 340篇 |
1997年 | 294篇 |
1996年 | 316篇 |
1995年 | 249篇 |
1994年 | 241篇 |
1993年 | 209篇 |
1992年 | 139篇 |
1991年 | 84篇 |
1990年 | 70篇 |
1989年 | 72篇 |
1988年 | 54篇 |
1987年 | 36篇 |
1986年 | 35篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 18篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1954年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Tan Jiahua Ma Wei Pan Bin Associate Professor Shanghai Jiao Tong University Shanghai Lecturer shanghai Jiao Tong University Shanghai 《中国海洋工程》1992,(1)
The basis, process and results of the demonstration of the main dimensions of a 75000t floating production and storage vessel are discussed in this paper. A simple but reliable orthogonal design method is applied in the main dimension optimization. The ideas of gradual approximation and feedback from various aspects are put into effect. During the demonstration, in order to make the model tally with the actual situation, the draft design is closely related to the computational analysis, so that the demonstration model can be verified at any time; the handling of the overall system is closely related to the research of each item, which is beneficial not only to the mastery of various regularities, but also to the balance of decisions. Finally, according to the computational results and the regularities obtained from analysis, the main dimensions are determined. 相似文献
32.
Yu Kuang-ming Zhang Jiachang Zhou Jiabao Professor Senior Engineer The River Harbour Department Nanjing Hydraulic Research Institute Nanjing Senior Engineer The River Harbour Department Nanjing Hydraulic Research Institute Nanjing 《中国海洋工程》1991,(4)
An empirical formula for estimating the overtopping discharge of wind-waves on a smooth-impermeable-simple slope dyke is derived through model tests in this paper, it can be adopted by related design departments in the determination of the crest elevation of the dyke. 相似文献
33.
东营城区高精度三维地震采集方法研究 总被引:3,自引:0,他引:3
根据东营城区内建筑物较多,环境干扰较大,地下构造复杂,断裂非常发育,目的层埋藏深,资料信噪比较低的特点,以地震老资料和钻井资料为基础,建立地震地质模型,利用射线追踪技术选取合适的观测系统参数。充分利用卫星数字地图,没计了灵活多变的观测系统,采用可控震源与炸药震源配合使用方法,及时对城区内地下面元的覆盖次数、方位角和炮检距的分布进行质量监控,利用现场处理系统对资料进行及时分析,提高了地震资料品质。所获得的东营城区高精度三维地震采集资料显示,其浅中层分辨率和中深层信噪比都有了明显改善,取得了良好的地质效果。 相似文献
34.
35.
本文将伴随法用于渤、黄、东海M2分潮的数值模拟,利用Topex/Poseidon高度计资料进行同化,优化海底摩擦系数。文中对底摩擦系数取常数时进行了优化,同时还对底摩擦系数的一种新的处理方法进行了研究,即在计算海区选取一些点给定底摩擦系数,海区中任意一点的底摩擦系数由这些点的底摩擦系数线性播值得到,优化后得到空间分布的底摩擦系数。针对两种不同的线性底摩擦假设分别进行了一系列的实际实验,结果表明由空间分布的底摩擦系数得到的模拟值比底摩擦系数取常数得到的模拟值更接近观测值,能有效地提高数值模拟的精度。 相似文献
36.
An optimization mathematical model of the pile forces for piled breasting dolphins in the open sea under various loading conditions is presented. The optimum layout with the well distributed pile forces and the least number of piles is achieved by the multiplier penalty function method. Several engineering cases have been calculated and compared with the result of the conventional design method. It is shown that the number of piles can be reduced at least by 10%—20% and the piles‘ bearing state is improved greatly. 相似文献
37.
简要阐述地震小区划在现代城市建设中的重要性以及在实施地震小区划的研究中浅层地震探测的重要作用及其方法原理,并给出应用浅层地震探测在城市地震小区划中的实例。 相似文献
38.
39.
Michael Riedel 《Marine Geophysical Researches》2007,28(4):355-371
Two single-channel seismic (SCS) data sets collected in 2000 and 2005 were used for a four-dimensional (4D) time-lapse analysis
of an active cold vent (Bullseye Vent). The data set acquired in 2000 serves as a reference in the applied processing sequence.
The 4D processing sequence utilizes time- and phase-matching, gain adjustments and shaping filters to transform the 2005 data
set so that it is most comparable to the conditions under which the 2000 data were acquired. The cold vent is characterized
by seismic blanking, which is a result of the presence of gas hydrate in the subsurface either within coarser-grained turbidite
sands or in fractures, as well as free gas trapped in these fracture systems. The area of blanking was defined using the seismic
attributes instantaneous amplitude and similarity. Several areas were identified where blanking was reduced in 2005 relative
to 2000. But most of the centre of Bullseye Vent and the area around it were seen to be characterized by intensified blanking
in 2005. Tracing these areas of intensified blanking through the three-dimensional (3D) seismic volume defined several apparent
new flow pathways that were not seen in the 2000 data, which are interpreted as newly generated fractures/faults for upward
fluid migration. Intensified blanking is interpreted as a result of new formation of gas hydrate in the subsurface along new
fracture pathways. Areas with reduced blanking may be zones where formerly plugged fractures that had trapped some free gas
may have been opened and free gas was liberated. 相似文献
40.
On the radiation and diffraction of linear water waves by an infinitely long rectangular structure submerged in oblique seas 总被引:1,自引:0,他引:1
The radiation and diffraction of linear water waves by an infinitely long rectangular structure submerged in oblique seas of finite depth is investigated. The analytical expressions for the radiated and diffracted potentials are derived as infinite series by use of the method of separation of variables. The unknown coefficients in the series are determined by the eigenfunction expansion matching method. The expressions for wave forces, hydrodynamic coefficients and reflection and transmission coefficients are given and verified by the boundary element method. Using the present analytical solution, the hydrodynamic influences of the angle of incidence, the submergence, the width and the thickness of the structure on the wave forces, hydrodynamic coefficients, and reflection and transmission coefficients are discussed in detail. 相似文献