全文获取类型
收费全文 | 25980篇 |
免费 | 4689篇 |
国内免费 | 7058篇 |
专业分类
测绘学 | 4303篇 |
大气科学 | 4594篇 |
地球物理 | 6307篇 |
地质学 | 12704篇 |
海洋学 | 3527篇 |
天文学 | 251篇 |
综合类 | 2030篇 |
自然地理 | 4011篇 |
出版年
2024年 | 105篇 |
2023年 | 314篇 |
2022年 | 871篇 |
2021年 | 1037篇 |
2020年 | 1214篇 |
2019年 | 1390篇 |
2018年 | 1154篇 |
2017年 | 1313篇 |
2016年 | 1385篇 |
2015年 | 1530篇 |
2014年 | 1612篇 |
2013年 | 1863篇 |
2012年 | 1781篇 |
2011年 | 1805篇 |
2010年 | 1411篇 |
2009年 | 1616篇 |
2008年 | 1684篇 |
2007年 | 1812篇 |
2006年 | 1730篇 |
2005年 | 1546篇 |
2004年 | 1392篇 |
2003年 | 1175篇 |
2002年 | 1078篇 |
2001年 | 915篇 |
2000年 | 858篇 |
1999年 | 790篇 |
1998年 | 716篇 |
1997年 | 640篇 |
1996年 | 564篇 |
1995年 | 500篇 |
1994年 | 450篇 |
1993年 | 395篇 |
1992年 | 231篇 |
1991年 | 215篇 |
1990年 | 151篇 |
1989年 | 107篇 |
1988年 | 122篇 |
1987年 | 83篇 |
1986年 | 46篇 |
1985年 | 36篇 |
1984年 | 16篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 16篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1972年 | 1篇 |
1954年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
972.
973.
974.
975.
976.
977.
1. IntroductionThe basic role of urban-rural boundary layer re-search is to study all kinds of physical process changesin the atmosphere boundary layer over urban and itssurrounding areas. Urban heat island (UHI) is a well-known feature of urban-rural climate. Attempts toincrease the understanding of the causes of the UHIand other urban-rural boundary layer phenomena haveused observational, theoretical and modelling methodssince long before. Seaman (1989) used a hydrostaticmodel, with real … 相似文献
978.
The contribution of areal precipitation of the catchment from Cuntan to Yichang (Three Gorges area) to eight flood peaks of the Upper Yangtze River (the upper reaches of the Yangtze River) is diagnosed for 1998 flood season. A rainfall-runoff model is employed to simulate runoffs of-this catchment. Comparison of observed and simulated runoffs shows that the rainfall-runoff model has a good capability to simulate the runoff over a large-scale river and the results describe the eight flood peaks very well. Forecast results are closely associated with the sensitivity of the model to rainfall and the calibration processes. Other reasons leading to simulation errors are further discussed. 相似文献
979.
The Application of ARGO Data to the Global Ocean Data Assimilation Operational System of NCC 总被引:11,自引:0,他引:11 下载免费PDF全文
1. Introduction It is well-known that the state of ocean plays very important role in the climate change. But there is a paucity of the ocean observation data. The data distri- bution in the space, time and different components is very inhomogeneous, even in some areas, there are no any observation data. Hence, it brings some diffcul- ties to the scientists to study many problems relevant to ocean. This situation has been being changed since ARGO (Array for Real-time Geostrophic Oceanogra-… 相似文献
980.
Abstract The major element and compatible trace element compositions of the northwest Kyushu basalts (NWKBs) collected from Saga-Futagoyama were analyzed to examine the petrogenesis of these basalts. Although nepheline-normative alkaline basalts are not found in the basalts from Saga-Futagoyama, the Saga-Futagoyama basalts almost cover the major element variations of NWKBs. The basalts can be chemically divided into two groups: an Fe-poor group (IPG) and an Fe-rich group (IRG). The compositional variation of IPG basalts is essentially controlled by the partial melting of the source as suggested by the following: (i) bulk rock MgO, FeO and NiO compositions indicate that some IPG samples were equilibrated with mantle olivine; and (ii) correlations between Al2 O3 , CaO and MgO are consistent with those of experimental partial melts of peridotites. The inconsistent behaviors of the elements compatible with clinopyroxene (Cpx), such as V (Sc and Cu), preclude the significant role of the fractional crystallization of Cpx and spinel in IPG variation. IPG basalts have low Al and high Fe concentrations compared to the products of melting experiments involving peridotites and pyroxenites, suggesting that the IPG source would have a lithology and bulk rock composition different from those of typical peridotites and pyroxenites. IRG basalts have negative correlations between Fe2 O3 * and MgO, and between V and Fe2 O3 */MgO, indicating that IRG basalts would have fractionated Cpx. However, the anomalously Fe-rich feature of IRG basalts compared with NWKBs collected from other areas suggests that the role of Cpx fractionation in NWKBs is minor. Relatively low melting temperatures would have principally caused the large chemical variation of NWKBs. 相似文献