全文获取类型
收费全文 | 1387篇 |
免费 | 227篇 |
国内免费 | 285篇 |
专业分类
测绘学 | 508篇 |
大气科学 | 229篇 |
地球物理 | 122篇 |
地质学 | 459篇 |
海洋学 | 231篇 |
天文学 | 27篇 |
综合类 | 187篇 |
自然地理 | 136篇 |
出版年
2024年 | 15篇 |
2023年 | 63篇 |
2022年 | 72篇 |
2021年 | 84篇 |
2020年 | 69篇 |
2019年 | 84篇 |
2018年 | 63篇 |
2017年 | 45篇 |
2016年 | 54篇 |
2015年 | 66篇 |
2014年 | 111篇 |
2013年 | 73篇 |
2012年 | 100篇 |
2011年 | 112篇 |
2010年 | 90篇 |
2009年 | 67篇 |
2008年 | 98篇 |
2007年 | 72篇 |
2006年 | 61篇 |
2005年 | 69篇 |
2004年 | 46篇 |
2003年 | 48篇 |
2002年 | 46篇 |
2001年 | 38篇 |
2000年 | 21篇 |
1999年 | 26篇 |
1998年 | 25篇 |
1997年 | 18篇 |
1996年 | 20篇 |
1995年 | 26篇 |
1994年 | 23篇 |
1993年 | 15篇 |
1992年 | 17篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1982年 | 4篇 |
1951年 | 1篇 |
1947年 | 1篇 |
1946年 | 1篇 |
1944年 | 2篇 |
1943年 | 1篇 |
1941年 | 2篇 |
1940年 | 2篇 |
1938年 | 1篇 |
1937年 | 1篇 |
1936年 | 1篇 |
1935年 | 1篇 |
1934年 | 1篇 |
1924年 | 2篇 |
排序方式: 共有1899条查询结果,搜索用时 31 毫秒
101.
1 INTRODUCTION Red algae C. ocellatus lives in temperate zone of coastal area, and inhabits at substrates from high tide to low tide regions. Its life history is composed of three phases: tetrasporophyte, gametophyte and carposporophyte. Chondrus is one o… 相似文献
102.
103.
104.
Impact of 4DVAR assimilation of rainfall data on the simulation of mesoscale precipitation systems in a mei-yu heavy rainfall event 总被引:1,自引:0,他引:1
The multi-scale weather systems associated with a mei-yu front and the corresponding heavy precipitation during a particular heavy rainfall event that occurred on 4 5 July 2003 in east China were successfully simulated through rainfall assimilation using the PSU/NCAR non-hydrostatic, mesoscale, numerical model (MM5) and its four-dimensional, variational, data assimilation (4DVAR) system. For this case, the improvement of the process via the 4DVAR rainfall assimilation into the simulation of mesoscale precipitation systems is investigated. With the rainfall assimilation, the convection is triggered at the right location and time, and the evolution and spatial distribution of the mesoscale convective systems (MCSs) are also more correctly simulated. Through the interactions between MCSs and the weather systems at different scales, including the low-level jet and mei-yu front, the simulation of the entire mei-yu weather system is significantly improved, both during the data assimilation window and the subsequent 12-h period. The results suggest that the rainfall assimilation first provides positive impact at the convective scale and the influences are then propagated upscale to the meso- and sub-synoptic scales.
Through a set of sensitive experiments designed to evaluate the impact of different initial variables on the simulation of mei-yu heavy rainfall, it was found that the moisture field and meridional wind had the strongest effect during the convection initialization stage, however, after the convection was fully triggered, all of the variables at the initial condition seemed to have comparable importance. 相似文献
Through a set of sensitive experiments designed to evaluate the impact of different initial variables on the simulation of mei-yu heavy rainfall, it was found that the moisture field and meridional wind had the strongest effect during the convection initialization stage, however, after the convection was fully triggered, all of the variables at the initial condition seemed to have comparable importance. 相似文献
105.
球面退化四叉树格网的剖分及变形分析 总被引:6,自引:5,他引:1
为有效解决经纬度格网与四元三角网(QTM)在全球空间数据管理与操作中存在的不足,提出一种新的全球离散格网剖分方法——球面退化四叉树格网(DQG),给出该格网的剖分原理与编码规则,并对其进行几何变形计算与分析。结果表明:DQG既具有经纬度格网结构简单的特征,又具有QTM几何变形稳定等优点。 相似文献
106.
The Regional Eta-coordinate Model(REM) has performed well in forecasting heavy rainfalls in China in recent years.A four-dimensional variational assimilation system(4DVar) is developed to improve the forecast skill of the REM.The tangent linear model and adjoint model codes are written according to thecode to coderule,and the establishment of the REM adjoint modeling system is introduced in detail in this paper.The tangent linear and adjoint models of the REM are validated against the observational data,... 相似文献
107.
108.
109.
110.