全文获取类型
收费全文 | 11519篇 |
免费 | 2522篇 |
国内免费 | 4520篇 |
专业分类
测绘学 | 2405篇 |
大气科学 | 1543篇 |
地球物理 | 1924篇 |
地质学 | 7816篇 |
海洋学 | 2123篇 |
天文学 | 133篇 |
综合类 | 935篇 |
自然地理 | 1682篇 |
出版年
2024年 | 155篇 |
2023年 | 395篇 |
2022年 | 731篇 |
2021年 | 926篇 |
2020年 | 661篇 |
2019年 | 841篇 |
2018年 | 697篇 |
2017年 | 656篇 |
2016年 | 685篇 |
2015年 | 831篇 |
2014年 | 766篇 |
2013年 | 983篇 |
2012年 | 1026篇 |
2011年 | 995篇 |
2010年 | 951篇 |
2009年 | 953篇 |
2008年 | 984篇 |
2007年 | 953篇 |
2006年 | 956篇 |
2005年 | 698篇 |
2004年 | 628篇 |
2003年 | 450篇 |
2002年 | 432篇 |
2001年 | 377篇 |
2000年 | 340篇 |
1999年 | 122篇 |
1998年 | 47篇 |
1997年 | 31篇 |
1996年 | 20篇 |
1995年 | 19篇 |
1994年 | 14篇 |
1993年 | 12篇 |
1992年 | 27篇 |
1991年 | 23篇 |
1990年 | 22篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 17篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1957年 | 8篇 |
1954年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Introduction An MS=6.0 earthquake occurred on February 23, 2001 in Yajiang county, Sichuan Province. The earthquake is located on the east of the southeast segment of the Litang-Dewu fault with strike of NW. Before the event, on February 14, an MS=5.0 earthquake took place nearly in the same place. In 1948 an MS=7.3 earthquake occurred on the northwestern segment of the Litang fault. The length of the surface rupture belt caused by the earthquake is 70 km, which extended from Litang to… 相似文献
13.
14.
通过分析、比较1996--2003年喀什地震台站记录到的新疆伽师及附近地区发生的多次6级地震的地磁前兆异常特征,发现在这几组地震活动过程中喀什地震台的地磁表现出不同的异常特征,说明与地震破裂特征有更深层次的相关性,且地磁响应比异常和总强度差值异常在一定程度上反映了台站周围小范围的震源区介质电性结构的变化。巴楚-伽师6.8级地震前地磁异常特征并不十分突出,有别于1996—1998年伽师强震群震前地磁异常量较丰富的特点。 相似文献
15.
16.
Although Eddy Covariance (EC) technique is one of the best methods for estimating the energy and mass exchanges between underlying surface and atmosphere in micrometeorology, errors and uncertainties still exist without necessary corrections. In this paper, we will focus on the effect of coordinate system on the eddy fluxes. Based on the data observed over four sites (one farmland site, one grassland site and two forest sites), the effects of three coordinate system transforming methods (Double Rotation-DR, Triple Rotation-TR and Planar Fit-PF)on the turbulent fluxes are analyzed. It shows that (i) the corrected fluxes are more or less than the uncorrected fluxes, which is related mainly to the sloping degree of surface, wind speed and wind direction; and (ii) pitch angle has a sinusoidal dependence on wind direction, especially in the regular sloping terrain; and (iii) PF method is something like the simplification of TR or DR,and there are not obvious distinctions in correction in sloping grassland and flat farmland, but PF method is not suitable for uneven and irregular forest sites. 相似文献
17.
High buildings or architectural complex in urban areas remarkably distort the urban surface wind fields. As the air flow approaches,local strong wind may appear around the buildings. The strong wind makes the pedestrians on sidewalks, entrances and terrace very uncomfortable and causes the pedestrian level wind environment problem. In this studies, hot-wire wind measurement, wind scouring in wind tunnel and numerical computation were carried out to evaluate the wind environment of tall buildings in the prevailing flow conditions in Beijing areas. The results obtained by three techniques were compared and mutually verified. The conclusions drawn from three approaches agree with each other. Also the advantages and limitations of each method were analyzed. It is suggested that the combination of different techniques may produce better assessment of wind environment around high buildings. 相似文献
18.
19.