全文获取类型
收费全文 | 8704篇 |
免费 | 1719篇 |
国内免费 | 1317篇 |
专业分类
测绘学 | 910篇 |
大气科学 | 839篇 |
地球物理 | 4490篇 |
地质学 | 2200篇 |
海洋学 | 1182篇 |
天文学 | 445篇 |
综合类 | 605篇 |
自然地理 | 1069篇 |
出版年
2024年 | 22篇 |
2023年 | 92篇 |
2022年 | 236篇 |
2021年 | 284篇 |
2020年 | 364篇 |
2019年 | 429篇 |
2018年 | 337篇 |
2017年 | 387篇 |
2016年 | 372篇 |
2015年 | 437篇 |
2014年 | 533篇 |
2013年 | 506篇 |
2012年 | 533篇 |
2011年 | 578篇 |
2010年 | 485篇 |
2009年 | 572篇 |
2008年 | 517篇 |
2007年 | 613篇 |
2006年 | 564篇 |
2005年 | 479篇 |
2004年 | 448篇 |
2003年 | 409篇 |
2002年 | 343篇 |
2001年 | 294篇 |
2000年 | 263篇 |
1999年 | 250篇 |
1998年 | 265篇 |
1997年 | 187篇 |
1996年 | 177篇 |
1995年 | 152篇 |
1994年 | 135篇 |
1993年 | 128篇 |
1992年 | 84篇 |
1991年 | 53篇 |
1990年 | 41篇 |
1989年 | 57篇 |
1988年 | 29篇 |
1987年 | 24篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 1篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1954年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
Aproposeddirectionalfunctionandwind-wavedirectionalspectrum¥WenShengchang;WuKejian;GuanChanglong;SunShicaiandZhangDacuo(Recei... 相似文献
82.
本文给出了“包装产品的计量标准型一次抽检方案”,并通过一个实例说明本方案比一般《计量标准型一次抽检方案》更为优越。 相似文献
83.
A finite-difference scheme and a modified marker-and-cell (MAC) algorithm have been developed to investigate the interactions of fully nonlinear waves with two- or three-dimensional structures of arbitrary shape. The Navier–Stokes (NS) and continuity equations are solved in the computational domain and the boundary values are updated at each time step by the finite-difference time-marching scheme in the framework of a rectangular coordinate system. The fully nonlinear kinematic free-surface condition is implemented by the marker-density function (MDF) technique developed for two fluid layers.To demonstrate the capability and accuracy of the present method, the numerical simulation of backstep flows with free-surface, and the numerical tests of the MDF technique with limit functions are conducted. The 3D program was then applied to nonlinear wave interactions with conical gravity platforms of circular and octagonal cross-sections. The numerical prediction of maximum wave run-up on arctic structures is compared with the prediction of the Shore Protection Manual (SPM) method and those of linear and second-order diffraction analyses based on potential theory and boundary element method (BEM). Through this comparison, the effects of non-linearity and viscosity on wave loading and run-up are discussed. 相似文献
84.
Algorithm for HF radar vector current measurements 总被引:1,自引:0,他引:1
A new algorithm is proposed, called the stream function method (SFM) for producing vector current maps from radial data measured
by dual-site high frequency surface wave radar (HFSWR). In SFM, a scalar stream function is constructed under some oceanographic
assumptions. The function describes the two-dimensional (2-D) ocean surface water motion and is used to obtain the distribution
of vector currents. The performance of SFM is evaluated using simulated radial data, which demonstrates that SFM has advantages
over typical vectorial combination methods (VCM) both in error acceptance and robustness, and excels another method based
on least-squares fitting (LSF) in recovering the complicated current models. Furthermore, SFM is capable of providing the
total currents based on radials from single-site radar. We also test the assumptions of horizontal non-divergence in the simulation.
The new algorithm is applied to the field experiment data of Wuhan University’s ocean state measuring and analyzing radar
(OSMAR), collected in the coastal East China Sea during April 11–17, 2004. Quantitative comparisons are given between radar
results by three current algorithms and in-situ current meter measurements. Preliminary analysis of the vertical current shear is given based on the current meter measurements. 相似文献
85.
对冲绳海槽1984-1990年的实测热流值,利用数字滤波方法计算,得到反映该区深部地壳热状态的区域热流值为80-160mW/m^2,用B样条函数法对其作数值模拟,计算出海槽地温场模式,并以此研究冲绳海槽海底高热流的形成机制,得出冲绳海槽热流值的区域性变化与綦中地质构造格局呈正相关,高热流是该区现代构造活动所致,其明显特征是地壳减薄,地幔上拱等结论。 相似文献
86.
研究外荷载为长期非平稳随机过程。考虑长期荷载的特性 ,采用 1个概率谱密度函数来反映长期非平稳随机荷载及其特征 ;概率谱密度函数是基于大量的一般谱密度函数的统计特性获得。以延长结构的抗疲劳使用寿命为目标函数 ,提出了调谐质量减振阻尼器的优化设计方法 ,这在实际工程中有着极为广阔的应用前景。本文旨在从理论上发展长期非平稳随机荷载作用下调谐质量减振阻尼器的优化设计方法 ;文中采用长期波浪实测数据 ,给出了 1个数值算例说明整个设计过程。 相似文献
87.
88.
89.
The Effect of Internal Fluid on the Response of Vortex-Induced Vibration of Marine Risers 总被引:5,自引:1,他引:5
Based on Iwan‘s wake oseillator model developed with the classical van der Pol equalion, the differential equation for the response of the vortex-induced vihration (VIV) of the riser considering the effect of the internal flowing fluid and the external marine environmental condition is derived. The effect of the intermal flowing fluid on the response of VIV of the riser is studied by means of the Finite Element Method. The results show that the effect of the internal fluid velocity on the VIV of the riser is strong when the natural frequency of the riser is close to the vortex shedding frequency. In addition, the increase of the top tension can decrease the sensitivity of the riser to the internal fluid velocity. 相似文献
90.