全文获取类型
收费全文 | 525篇 |
免费 | 73篇 |
国内免费 | 121篇 |
专业分类
测绘学 | 33篇 |
大气科学 | 81篇 |
地球物理 | 167篇 |
地质学 | 206篇 |
海洋学 | 69篇 |
天文学 | 4篇 |
综合类 | 73篇 |
自然地理 | 86篇 |
出版年
2024年 | 5篇 |
2023年 | 15篇 |
2022年 | 36篇 |
2021年 | 42篇 |
2020年 | 43篇 |
2019年 | 32篇 |
2018年 | 63篇 |
2017年 | 54篇 |
2016年 | 51篇 |
2015年 | 39篇 |
2014年 | 38篇 |
2013年 | 37篇 |
2012年 | 39篇 |
2011年 | 49篇 |
2010年 | 14篇 |
2009年 | 45篇 |
2008年 | 19篇 |
2007年 | 25篇 |
2006年 | 18篇 |
2005年 | 16篇 |
2004年 | 5篇 |
2003年 | 14篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1983年 | 2篇 |
排序方式: 共有719条查询结果,搜索用时 15 毫秒
11.
New magnetostratigraphic and pedostratigraphic investigations of loess deposits in north‐east China and their implications for regional environmental change during the Mid‐Pleistocene climatic transition 下载免费PDF全文
12.
An analytical solution is developed in this paper to investigate the dynamic response of a large‐diameter end‐bearing pipe pile subjected to torsional loading in viscoelastic saturated soil. The wave propagation in saturated soil and pile are simulated by Biot's two‐phased linear theory and one‐dimensional elastic theory, respectively. The dynamic equilibrium equations of the outer soil, inner soil, and pile are established. The solutions for the outer and inner soils in frequency domain are obtained by Laplace transform technique and the separation of variables method. Then, the dynamic response of the pile is obtained on the basis of the perfect contacts between the pile and the outer soil as well as the inner soil. The results in this paper are compared with that of a solid pile in elastic saturated soil to verify the validity of the solution. Furthermore, the solution in this paper is compared with the classic plane strain solution to verify the solution further and check the accuracy of the plane strain solution. Numerical results are presented to analyze the vibration characteristics and illustrate the effect of the soil parameters and the geometry size of the pile on the complex impedance and velocity admittance of the pile head. Finally, the displacement of the soil at different depth and frequency is analyzed. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
13.
深弹发射装置安装在甲板部位,使用环境恶劣,过去均采用传统的试验方法进行环境适应性考核。最近几年,随着三维设计的广泛应用,仿真技术也开始发挥作用,以发射装置接线箱的冲击响应为例,介绍仿真技术在发射装置环境适应性分析中的应用。通过案例分析可知,仿真分析对于发现机械结构设计中的薄弱环节还是非常有效的,它突破了环境试验受限于试验样机和特定环境条件的限制,可以在较短的时间内得到仿真结果,对装备模型进行及时修正。 相似文献
14.
Watershed delineation is a required step when conducting any spatially distributed hydrological modelling. Automated approaches are often proposed to delineate a watershed based on a river network extracted from the digital elevation model (DEM) using the deterministic eight‐neighbour (D8) method. However, a realistic river network cannot be derived from conventional DEM processing methods for a large flat area with a complex network of rivers, lakes, reservoirs, and polders, referred to as a plain river network region (PRNR). In this study, a new approach, which uses both hydrographic features and DEM, has been developed to address the problems of watershed delineation in PRNR. It extracts the river nodes and determines the flow directions of the river network based on a vector‐based hydrographic feature data model. The river network, lakes, reservoirs, and polders are then used to modify the flow directions of grid cells determined by D8 approach. The watershed is eventually delineated into four types of catchments including lakes, reservoirs, polders, and overland catchments based on the flow direction matrix and the location of river nodes. Multiple flow directions of grid cells are represented using a multi‐direction encoding method, and multiple outflows of catchments are also reflected in the topology of catchments. The proposed approach is applied to the western Taihu watershed in China. Comparisons between the results obtained from the D8 approach, the ‘stream burning’ approach, and those from the proposed approach clearly demonstrate an improvement of the new approach over the conventional approaches. This approach will benefit the development of distributed hydrological models in PRNR for the consideration of different types and multiple inlets and outlets of catchments. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
15.
16.
对济南市2013年1—12月的能见度、相对湿度、PM10及PM2.5逐时监测数据分析,结果表明:能见度、相对湿度、PM10和PM2.5浓度有明显的月变化和日变化规律。在各项污染物中,能见度与颗粒物的相关性最高,与PM10的相关系数为-0.6718,与PM2.5的相关系数为-0.7422;在气象因子中,与相对湿度的相关性最高,相关系数为-0.6501。不同季节条件下,能见度与PM2.5的相关性明显优于PM10的,冬季能见度与颗粒物的相关性明显优于其他季节的。 相似文献
17.
西北太平洋浪流相互作用对有效波高的影响研究 总被引:1,自引:0,他引:1
西北太平洋强流区会对海浪的特征和分布产生显著的影响,尤其是研究台风过程中海流与海浪的相互作用具有重要的研究意义。本文以ROMS海洋模式和SWAN海浪模式为基础,构建了浪流耦合模式系统,对2013年10月6-17日间的台风“丹娜丝”、“百合”、“韦帕”过程中西北太平洋浪流相互作用中海流对有效波高的影响进行了研究。通过对比模式模拟有效波高与浮标观测资料,发现耦合后的有效波高比非耦合结果更接近观测值,耦合模式中海流的存在对有效波高的分布有明显的影响。研究表明,特别是在有效波高峰值处,海流引起的有效波高增大最大可达1 m。海浪浪向及流向的空间分布以及中国近海浮标处浪向与流向的时间序列表明,流向与浪向反向时,海流的影响造成有效波高增大;二者同向时,有效波高减小。海流对有效波高的调整会沿着海浪传播的方向传播相当一段距离。在西北太平洋的海浪场计算中,引入海流的耦合模式计算结果对改善强流区海浪预报具有重要意义,并且海流的模拟精度对于高精度的海浪预报非常重要。 相似文献
18.
WANG Jing LI Zhenxing PAVASE Ramesh Tushar LIN Hong ZOU Long WEN Jie LV Liangtao 《中国海洋大学学报(英文版)》2016,15(4):690-696
Advanced glycation endproducts(AGEs) have been recognized as hazards in processed foods that can induce chronic diseases such as cardiovascular disease, diabetes, and diabetic nephropathy. In this study, we investigated the AGEs contents of 35 types of industrial seafood products that are consumed frequently in eastern China. Total fluorescent AGEs level and Nε-carboxymethyl-lysine(CML) content were evaluated by fluorescence spectrophotometry and gas chromatography-mass spectrometry(GC-MS), respectively. The level of total fluorescent AGEs in seafood samples ranged from 39.37 to 1178.3 AU, and was higher in canned and packaged instant aquatic products that were processed at high temperatures. The CML content in seafood samples ranged from 44.8 to 439.1 mg per kg dried sample, and was higher in roasted seafood samples. The total fluorescent AGEs and CML content increased when seafood underwent high-temperature processing, but did not show an obvious correlation. The present study suggested that commonly consumed seafood contains different levels of AGEs, and the seafood processed at high temperatures always displays a high level of either AGEs or CML. 相似文献
19.
20.