全文获取类型
收费全文 | 13142篇 |
免费 | 2375篇 |
国内免费 | 3148篇 |
专业分类
测绘学 | 951篇 |
大气科学 | 2854篇 |
地球物理 | 3214篇 |
地质学 | 6497篇 |
海洋学 | 1605篇 |
天文学 | 753篇 |
综合类 | 1247篇 |
自然地理 | 1544篇 |
出版年
2024年 | 89篇 |
2023年 | 283篇 |
2022年 | 633篇 |
2021年 | 727篇 |
2020年 | 580篇 |
2019年 | 713篇 |
2018年 | 676篇 |
2017年 | 669篇 |
2016年 | 765篇 |
2015年 | 631篇 |
2014年 | 793篇 |
2013年 | 749篇 |
2012年 | 709篇 |
2011年 | 682篇 |
2010年 | 775篇 |
2009年 | 669篇 |
2008年 | 634篇 |
2007年 | 613篇 |
2006年 | 499篇 |
2005年 | 476篇 |
2004年 | 358篇 |
2003年 | 377篇 |
2002年 | 368篇 |
2001年 | 391篇 |
2000年 | 393篇 |
1999年 | 598篇 |
1998年 | 501篇 |
1997年 | 453篇 |
1996年 | 472篇 |
1995年 | 399篇 |
1994年 | 346篇 |
1993年 | 321篇 |
1992年 | 264篇 |
1991年 | 204篇 |
1990年 | 169篇 |
1989年 | 136篇 |
1988年 | 135篇 |
1987年 | 70篇 |
1986年 | 61篇 |
1985年 | 48篇 |
1984年 | 36篇 |
1983年 | 25篇 |
1982年 | 37篇 |
1981年 | 32篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1978年 | 7篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1958年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
81.
近海工程环境应用中各种风资料的平均时间分析 总被引:5,自引:0,他引:5
本文从近海工程设计应用的需要出发,对于通常使用的不同来源的测风资料平均时间进行了分析,这些资料来源包括:岸边及近海探查与生产设施上的气象台站、天气观测船、浮标、商船气象报、从受灾情况估计出的极大风速以及动力诊断模型估计出的海面风速。 相似文献
82.
给定SS-Y型伸缩仪系统阶跃信号输入,分别记录该系统的输入输出数据,得到系统的输入输出对.应用最小二乘法辨识出该系统的传递函数,并通过Matlab仿真验证了该系统传递函数模型的有效性. 相似文献
83.
DISTRIBUTIONS OF TOTAL, INORGANIC AND ORGANIC PHOSPHORUS IN THE SEDIMENTS NEAR THE HUANGHE RIVER ESTUARY 总被引:1,自引:0,他引:1
For some hundred surface sediment samples from five cores taken in two cruises near the Huanghe River Estuary, total phosphorus (TP (.inorganic phosphorus (IP (and organic phosphorus (OP)were determined.On the average, 527×10-6, 455×10~6 and 72×10-6 were found for TP,IP and OP for the surface sediments taken in the two cruises. The distribution of OP and IP was controlled by the sample particle size: OP content increased with the decreasing of the sample particle size, while the maximal value of IP was found in the silt fraction due to the existence of apatite in our samples. Vertical distributions reflected well the channel change of the Huanghe River. Results from the multiple regressions between the three forms of phosphorus and the percentages of different particle size agreed well with the analytical data. 相似文献
84.
85.
Pang Yue Fan Dejiang Sun Xiaoxia Sun Xueshi Liu Ming Yang Zuosheng 《中国海洋大学学报(英文版)》2020,19(4):801-810
For a long time, most studies about pyrite have focused on sediments while only a few have focused on pyrite in water. In this study, a method that combines the scanning electron microscopy(SEM) and the energy dispersive X-ray spectrometry(EDS) was used to compare pyrite particles suspended in water to those in associated bottom sediments, both obtained from the mixing zone of the Yangtze Estuary. It was found that the pyrite particles in the two media have similar morphologies and size distributions. The particle morphology mainly includes two types, single crystal and aggregate, and the particle size mainly ranges from 0.5 to 2 μm. The pyrite particles in water exhibit an increase in relative content towards the sea, and their transport and deposit processes are mainly affected by hydrodynamic conditions. It is concluded that the pyrite particles in the suspended matter mainly derived from the resuspension of sediments, which are products of the early diagenesis. Precursor minerals may appear during the formation of pyrite, but are generally restricted by the diagenetic environment and local microenvironment. 相似文献
86.
泊松曲线是一种精度较高的沉降预测方法,但是它只能在等时距数据条件下方能使用,在工程实际中很难满足这一要求。本文采用插值法将非等时距数据转化成等时距数列,并结合高层建筑沉降监测工程实例分析,结果表明,用泊松曲线模型预测建筑物沉降量与实际沉降量比较接近,具有较高的应用价值。 相似文献
87.
长江三峡库区梯田稳定性分析与对策*──以鄂西秭归县为例 总被引:6,自引:0,他引:6
三峡库区历史上就是滑坡、崩塌作用强烈的地带,在调查分析秭归县滑坡、崩塌对梯田稳定性的影响的基础上,探讨了四种不稳定梯田培坎的特征、性质和现状,提出了利用优势植物固土护坎等相应的对策。 相似文献
88.
Fulong Wu 《Urban geography》2018,39(8):1177-1194
Housing privatization seems to suggest a process of state retreat. However, this is not always the case in China. This paper examines an estate that is mixed with work-unit housing and municipal public housing to understand its changing governance. It is intriguing to observe that the state has had to return to this neighborhood to strengthen its administration following housing privatization, because the attempt to transfer responsibility to commercial property management failed. The neighborhood governance, however, has transformed from one based on work-units to a government-funded administrative agency. The return of the state has been achieved through professional social workers, and it is struggling to operate, leading to the alienation and disempowerment of former state work-unit residents. The side effect of this approach to governance is that, through encouraging market provision and commercial operation which is not fully working, reciprocal activities are restrained. Since housing privatization, the neighborhood has deteriorated from a brand-new estate into an ‘old and dilapidated neighborhood’ in less than 25 years. 相似文献
89.
江南丘陵地区乡村聚落地域分异特征研究——以湖南省为例 总被引:1,自引:2,他引:1
以江南丘陵湖南地区为研究对象,通过对18个抽样村进行实地走访与问卷调查,从乡村聚落的居住条件、居住设施和乡村居民的生产生活形态等方面,探讨江南丘陵湖南地区乡村聚落空间地域分异特征与规律。研究表明:乡村聚落研究是江南丘陵地区乡村聚落空间布局优化与调控的基础。由于地域范围广泛,区域内的资源禀赋与地域组合、经济发展基础、文化传统等条件差异悬殊,因此江南丘陵湖南地区乡村聚落发展的地域分异规律较为明显,在聚落空间格局(规模、密度、形态)、居住条件(住房面积、住房结构、建筑特色)、居住设施(道路、饮水安全、网络电视开通率等基础与公共服务设施)和生产生活形态等方面呈现出较为显著的盆地-丘陵-低山区、发达-欠发达-落后、近郊-远郊-偏远等地貌、经济、区位梯度差异。 相似文献
90.
Renguang Wu 《Climate Dynamics》2010,34(5):629-642
Analysis of the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) data for the period 1998–2007 reveals large
subseasonal fluctuations in sea surface temperature (SST) of the South China Sea during the summer monsoon onset. These subseasonal
SST changes are closely related to surface heat flux anomalies induced by surface wind and cloud changes in association with
the summer monsoon onset. The SST changes feed back on the atmosphere by modifying the atmospheric instability. The results
suggest that the South China Sea summer monsoon onset involves ocean–atmosphere coupling on subseasonal timescales. While
the SST response to surface heat flux changes is quick and dramatic, the time lag between the SST anomalies and the atmospheric
convection response varies largely from year to year. The spatial–temporal evolution of subseasonal anomalies indicates that
the subseasonal variability affecting the South China Sea summer monsoon onset starts over the equatorial western Pacific,
propagates northward to the Philippine Sea, and then moves westward to the South China Sea. The propagation of these subseasonal
anomalies is related to the ocean–atmosphere interaction, involving the wind-evaporation and cloud-radiation effects on SST
as well as SST impacts on lower-level convergence over the equatorial western Pacific and atmospheric instability over the
Philippine Sea and the South China Sea. 相似文献