全文获取类型
收费全文 | 2796篇 |
免费 | 520篇 |
国内免费 | 814篇 |
专业分类
测绘学 | 150篇 |
大气科学 | 713篇 |
地球物理 | 709篇 |
地质学 | 1439篇 |
海洋学 | 404篇 |
天文学 | 91篇 |
综合类 | 256篇 |
自然地理 | 368篇 |
出版年
2024年 | 8篇 |
2023年 | 42篇 |
2022年 | 101篇 |
2021年 | 134篇 |
2020年 | 126篇 |
2019年 | 130篇 |
2018年 | 164篇 |
2017年 | 139篇 |
2016年 | 171篇 |
2015年 | 136篇 |
2014年 | 152篇 |
2013年 | 184篇 |
2012年 | 174篇 |
2011年 | 188篇 |
2010年 | 189篇 |
2009年 | 147篇 |
2008年 | 172篇 |
2007年 | 154篇 |
2006年 | 141篇 |
2005年 | 119篇 |
2004年 | 98篇 |
2003年 | 105篇 |
2002年 | 96篇 |
2001年 | 77篇 |
2000年 | 95篇 |
1999年 | 150篇 |
1998年 | 96篇 |
1997年 | 112篇 |
1996年 | 90篇 |
1995年 | 75篇 |
1994年 | 75篇 |
1993年 | 47篇 |
1992年 | 41篇 |
1991年 | 36篇 |
1990年 | 28篇 |
1989年 | 22篇 |
1988年 | 21篇 |
1987年 | 13篇 |
1986年 | 17篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1966年 | 3篇 |
1958年 | 3篇 |
排序方式: 共有4130条查询结果,搜索用时 15 毫秒
991.
992.
The experimental investigation of unidirectional random wave slamming on the three-dimensional structure in the splash zone is presented. The experiment is conducted in the marine environment channel in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. The test wave is unidirectional irregular wave. The experiments are carried out with perpendicular random waves (β=0°) and oblique random waves (β=15°, 30°, 45°), the significant wave heights H1/3 ranging from 7.5 to 20 cm with 2.5 cm increment, the peak wave periods Tp ranging from 0.75 to 2.0 s with 0.25 s increment, and the clearance of the model with respect to the significant wave height s/H1/3 ranging from 0.0 to 0.5 with 0.1 increment. The statistical analysis results of different test cases are presented. The statistical distribution characteristics of the perpendicular irregular wave impact pressures are compared with that of the oblique irregular wave on the underside of the structure. The effect of the wave direction β on the wave impact forces on the underside of the structure is determined. The relation between the impact forces and the parameters such as the significant wave height, the relative structure width and the relative clearance of the structure is also discussed. 相似文献
993.
Based on China's observational data in 1951-1990,after minimizing the possible biasescaused by station relocation and urban heat island,the spatial and temporal distributions of trendsfor maximum and minimum temperatures are studied.The results show that increasing trends ofmaximum temperatures are in the areas west to 95°E,and north to the Huanghe(Yellow)River,while decreasing trends exist in eastern China south to the Yellow River.Minimum temperaturesare generally increasing throughout China,with dominant warming trends at the higher latitudes.This resulted in very obvious decreasing trends in diurnal temperature ranges.The periodic cycles are consistent between the maximum and minimum temperatures,butasymmetric trends are very obvious.The significant increase of minimum(nighttime)temperaturesreflects the evidence of enhancement of greenhouse effect.Further analysis shows that the changesof maximum and minimum temperatures are mainly related to sunshine duration and atmosphericwater vapor content. 相似文献
994.
995.
据近年内阿尔金断裂研究的进展阐述了应深入解决的4个科学问题及其研究思路:1)阿尔金大型走滑断裂何时发生?变形年代学研究证明阿尔金断裂初始走滑的年龄在89~97 Ma,即从晚中生代-早新生代才开始出现;2)运动学研究包括隆升与走滑两个方面,需要进行大比例尺度的构造研究和变形组构研究,尤其是断裂两盘错距的确定,必须找准被断裂错移的同一构造-岩相带的界线;3)阿尔金断裂的划分意义,它的延伸和规模及对中国西部以及中亚大陆构造格架的影响;4)阿尔金断裂对两侧盆地沉积-构造演化的控制和影响.解决上述4个科学问题,对于重新认识中国西部大陆构造格架、中国西部成矿带的展布及对中国西部找油的战略评估都具有非常重要的意义. 相似文献
996.
997.
GONG Yiming Faculty of Earth Science China University of Geosciences Wuhan LI Baohua Laboratory of Marine Geology Tongji University Shanghai WU Yi Guangxi Institute of Geology Nanning 《《地质学报》英文版》2001,75(4):354-363
Four hierarchical cyclothems, superbundlesets, bundlesets, bundles and laminae, have been identified from the Devonian Frasnian-Famennian carbonate strata in Guangxi, South China. Their hierarchical structures, ratio relationships and sequence in conodont zones are continuous and stable and can be traced across different facies zones and sedimentary basins. Our data show that hierarchically organized superbundlesets, bundlesets, bundles and laminae correspond to the long eccentricity, eccentricity, obliquity or precession and sub-Milankovitch cycles respectively. Their periods were 400,000, 100,000, 33,333, 16,667 and 8,000-17,000 a, respectively. The ratios of long eccentricity to eccentricity, eccentricity to obliquity, and eccentricity to precession in the Devonian are 1:4, 1:3 and 1:6 respectively. Using these hierarchical Milankovitch cyclothems, chronostratigraphical division and correlation can be realized at a resolution of 100 ka or 10 ka at the Frasnian-Famennian transition. The time intervals 相似文献
998.
河西内陆河地表水与地下水转化及水资源利用率研究 总被引:16,自引:8,他引:16
河西内陆河水资源产生于祁连山区 ,河流出山以后依次穿越山前洪积扇、走廊南部盆地、北部盆地 ,最后进入尾闾湖 .由于山前洪积扇、南北盆地及河床具有良好的通透性和巨大的蓄水能力使地表水易于转化为地下水 ,出山水量的很大一部分渗入地下避免无效蒸散损耗 ;同时由于特殊的串珠状水文地质盆地构造 ,水资源具有同源性和多次转化特点 ,使水资源的利用率大大提高 .研究表明 ,1999年河西水资源总量为 6 3 79× 10 8m3 ,其中 ,地表水资源量为 5 8 36× 10 8m3 ,地下水资源量为 5 6 39× 10 5m3 ,地表水与地下水重复计算量高达 5 0 96× 10 5m3 .三个流域水资源利用率达到 6 1 4%~ 2 11% 相似文献
999.
To add to the growing mature research on the tropical 30-50 day oscillations from a new prospective,
the current work bases on dynamic analysis of baroclinic quasi-geostrophic models to discuss dynamic
mechanisms for the generation and propagation of CISK-Rossby waves, and to understand restraints and effects
of different wave structures and thermodynamic forcing on the 30-50 day oscillations in the tropical atmosphere.
Some important properties of the oscillation propagation have been explained and, in detail, with respect to its
meridional propagation and vertical “baroclinic” structure. The work has come up with some new opinions and
viewpoints. New opinions about the propagation and energy dispersion are to be proved by more observations
and study. 相似文献
1000.
Dynamic and numerical methods are used to discuss the atmospheric response to SST thermal
forcing. The results show that for planetary scale systems, the standing SST thermal forcing can quickly excite a
stable atmospheric equilibrium state response, which is characterized by obvious large-scale teleconnection
oscillation in east-west and south-north directions. For synoptic scale systems, the SST thermal forcing mainly
excites the atmospheric low-frequency oscillation. Some basic relation and dynamic processes between SST
thermal forcing and atmospheric response pattern are revealed and some new viewpoints are presented. 相似文献