全文获取类型
收费全文 | 16805篇 |
免费 | 3545篇 |
国内免费 | 1894篇 |
专业分类
测绘学 | 1118篇 |
大气科学 | 676篇 |
地球物理 | 10482篇 |
地质学 | 5520篇 |
海洋学 | 1845篇 |
天文学 | 158篇 |
综合类 | 909篇 |
自然地理 | 1536篇 |
出版年
2024年 | 35篇 |
2023年 | 153篇 |
2022年 | 416篇 |
2021年 | 530篇 |
2020年 | 627篇 |
2019年 | 759篇 |
2018年 | 591篇 |
2017年 | 641篇 |
2016年 | 584篇 |
2015年 | 736篇 |
2014年 | 906篇 |
2013年 | 956篇 |
2012年 | 979篇 |
2011年 | 1084篇 |
2010年 | 884篇 |
2009年 | 1018篇 |
2008年 | 1014篇 |
2007年 | 1170篇 |
2006年 | 1155篇 |
2005年 | 969篇 |
2004年 | 943篇 |
2003年 | 812篇 |
2002年 | 675篇 |
2001年 | 540篇 |
2000年 | 569篇 |
1999年 | 502篇 |
1998年 | 463篇 |
1997年 | 421篇 |
1996年 | 432篇 |
1995年 | 347篇 |
1994年 | 323篇 |
1993年 | 269篇 |
1992年 | 191篇 |
1991年 | 127篇 |
1990年 | 92篇 |
1989年 | 93篇 |
1988年 | 70篇 |
1987年 | 43篇 |
1986年 | 41篇 |
1985年 | 21篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 19篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1954年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
91.
20世纪末,地震勘探技术在油气勘探、煤田勘探、工程勘探等多方面的应用都有了突飞猛进的发展。总结了近年来地震勘探在岩性、沉积相、构造体系等不同地质条件下的应用实例,用以说明地震勘探的多用性及其强大的生命力。 相似文献
92.
中国台湾地区地处欧亚板块与菲律宾海板块之间,地震活动频繁.本文报道了 我国台湾地区及其邻近海域1985~2002年间5.5级以上地震的条带内外频度比分 布,并着重研究了1999—2002年中发生的3次7.5级以上地震前的条带现象.其结 果表明:台湾地区近期发生的3次7.5级以上大地震前,5.5级以上地震呈条带分 布.这些条带符合条带内地震个数Nin≥6的条件,符合条带内、外频度比Nin/(Nin Nout)≥75%的条件,也符合条带长宽比大于5的要求,只是与板内地震条带相比,条 带的长度较短. 相似文献
93.
多维联合概率理论对三峡工程设计洪水的计算 总被引:1,自引:0,他引:1
首次将多维联合概率理论应用到三峡大坝设计洪水的风险分析,并用随机模拟方法(ISPUD)对四维联合概率分布进行了求解,得出在长江上游干流及主要支流来水量出现的不同组合和最不利组合情况下,相应三峡大坝不同联合重现期的设计洪水。可用于三峡工程的风险分析及防洪调度。 相似文献
94.
A finite element model is set up and experimental tests are performed to help understand the behavior of a concrete canoe and subsequently optimize its design. First, the performance criteria that must be satisfied to participate at the annual ASCE/Master Builders competition are described. Then, the finite element model and the different loading cases that were studied are presented. Results from these loading cases are discussed and used to optimize the material properties as well as the thickness of the hull and the dimensions of the gunwale and reinforcing ribs. Static and dynamic experimental tests were also conducted to validate the results of the finite element analyses. The results indicate that the main stresses and strains are caused by the static load cases. The additional stresses caused during races are small. 相似文献
95.
本文在对位于黄海南部陆架上的朝连岛站30年水温资料进行分析时发现,该站的表层水温有周期大于20个月的低频振动,其中以准两年周期和6年周期最显著。陆架水温的这种低频振动是对东亚季风异常的响应。这种低频振动在冬季与渤海冰情的变化同步;在夏季与黄海底层冷水团的强弱相关。同时,这种低频振动在对马暖流上也有一定的反映。 相似文献
96.
In this study, the impact of oceanic processes on the sensitivity of transient climate change is investigated using two sets of coupled experiments with and without tidal forcing, which are termed Exp_Tide and Exp_Control,respectively. After introducing tidal forcing, the transient climate response(TCR) decreases from 2.32 K to 1.90 K,and the surface air temperature warming at high latitudes decreases by 29%. Large ocean heat uptake efficiency and heat storage can explain the low TCR in Exp_Tide. Approximately 21% more heat is stored in the ocean in Exp_Tide(1.10×10~(24) J) than in Exp_Control(0.91×10~(24) J). Most of the large ocean warming occurs in the upper 1 000 m between 60°S and 60°N, primarily in the Atlantic and Southern Oceans. This ocean warming is closely related to the Atlantic Meridional Overturning Circulation(AMOC). The initial transport at mid-and high latitudes and the decline in the AMOC observed in Exp_Tide are both larger than those observed in Exp_Control. The spatial structures of AMOC are also different with and without tidal forcing in present experiments. The AMOC in Exp_Tide has a large northward extension. We also investigated the relationship between AMOC and TCR suggested by previous studies using the present experiments. 相似文献
97.
98.
The upper layer (above 140 m depth) temperature in the western Philippine Sea near Taiwan was sampled using a coastal monitoring
buoy (CMB) with 15 attached thermistors during July 28–August 7, 2005. The data were collected every 10 min at 1, 3, 5, 10,
15, and 20 m using the CMB sensors, and every 15 sec at 15 different depths between 25 m and 140 m. Internal waves and solitons
were identified from the time-depth plot of the temperature field. Without the internal waves and solitons, the power spectra,
structure functions, and singular measures (representing the intermittency) of temperature field satisfy the power law with
multi-scale characteristics at all depths. The internal waves do not change the basic characteristics of the multifractal
structure. However, the internal solitons change the power exponent of the power spectra drastically, especially in the low
wave number domain; they also break down the power law of the structure function and increase the intermittency parameter.
The physical mechanisms causing these different effects need to be explored further. 相似文献
99.
100.
The rain-flow counting method is widely used to compile the fatigue load spectrum. The second stage counting of the rain-flow method is a troublesome process. In order to overcome this drawback, the rain-flow and reverse rain-flow counting method is proposed in this paper. In this counting method, the rule for counting of the rain-flow method is modified, so that the sequence of load-time need not be adjusted. This is a valid and useful method to count cycles and compile the load spectrum and it can be widely used in ocean engineering. 相似文献