全文获取类型
收费全文 | 9961篇 |
免费 | 1082篇 |
国内免费 | 3579篇 |
专业分类
测绘学 | 512篇 |
大气科学 | 1687篇 |
地球物理 | 3473篇 |
地质学 | 5678篇 |
海洋学 | 1027篇 |
天文学 | 405篇 |
综合类 | 694篇 |
自然地理 | 1146篇 |
出版年
2024年 | 67篇 |
2023年 | 179篇 |
2022年 | 121篇 |
2021年 | 205篇 |
2020年 | 122篇 |
2019年 | 134篇 |
2018年 | 184篇 |
2017年 | 64篇 |
2016年 | 153篇 |
2015年 | 149篇 |
2014年 | 264篇 |
2013年 | 250篇 |
2012年 | 323篇 |
2011年 | 388篇 |
2010年 | 218篇 |
2009年 | 295篇 |
2008年 | 346篇 |
2007年 | 446篇 |
2006年 | 500篇 |
2005年 | 579篇 |
2004年 | 557篇 |
2003年 | 389篇 |
2002年 | 462篇 |
2001年 | 495篇 |
2000年 | 526篇 |
1999年 | 253篇 |
1998年 | 206篇 |
1997年 | 202篇 |
1996年 | 190篇 |
1995年 | 251篇 |
1994年 | 217篇 |
1993年 | 410篇 |
1992年 | 364篇 |
1991年 | 454篇 |
1990年 | 399篇 |
1989年 | 438篇 |
1988年 | 451篇 |
1987年 | 375篇 |
1986年 | 266篇 |
1985年 | 363篇 |
1984年 | 301篇 |
1983年 | 221篇 |
1982年 | 169篇 |
1981年 | 124篇 |
1980年 | 177篇 |
1964年 | 89篇 |
1960年 | 55篇 |
1959年 | 119篇 |
1958年 | 125篇 |
1957年 | 127篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
白垩纪温度较冷的估价 总被引:1,自引:0,他引:1
白垩纪温度较冷的估价B.w.Sellwood等有关白垩纪气候的概念部分基于详尽的地质证据,如不耐寒冷的古生物(如:珊瑚的分布比现在偏极地5-15℃)和特殊气候条件的沉积相的广泛分布。这些资料的解释反映21℃的等温线在纬度上至少向两极移动5°,全球的平... 相似文献
33.
34.
Jowett J 《Geography review》1989,3(2):26-31
The author presents a selection of cartograms designed to illustrate aspects of the demography of China. Topics covered include population growth, density, regional variations in fertility, and age distribution. A discussion of the advantages of using cartograms (maps drawn proportional to a given variable) as opposed to conventional, area-based maps, is included. 相似文献
35.
Trends in emigration from Ireland over time are reviewed. "During the eighteenth and nineteenth centuries overseas migration to the United States and seasonal harvest migration to Britain were the main types of movement, but over the past 100 years the Irish have developed a special affinity for settling in British towns. Although the outflow was halted for a time during the 1970s, when return migration took over, the 1980s have seen a renewal of the exodus. This time, however, the character of the flow has changed from predominantly low-skill construction and factory workers to embrace better-educated emigrants, including many graduates. This shift reflects Ireland's changing position in the international market for labour." 相似文献
36.
Connell J 《The Australian geographer》1992,23(1):44-50
The implications of the Gulf War are assessed for the countries in Asia that send labor migrants to the Middle East. "This paper seeks to examine the effects of...the loss of remittances (and related issues, including return migration), primarily in terms of the long-term implications of the War for the future of contract labour migration in the Asian region...." 相似文献
37.
The atmospheric circulation of Titan is investigated with a general circulation model. The representation of the large-scale dynamics is based on a grid point model developed and used at Laboratoire de Météorologie Dynamique for climate studies. The code also includes an accurate representation of radiative heating and cooling by molecular gases and haze as well as a parametrization of the vertical turbulent mixing of momentum and potential temperature. Long-term simulations of the atmospheric circulation are presented. Starting from a state of rest, the model spontaneously produces a strong superrotation with prograde equatorial winds (i.e., in the same sense as the assumed rotation of the solid body) increasing from the surface to reach 100 m sec-1 near the 1-mbar pressure level. Those equatorial winds are in very good agreement with some indirect observations, especially those of the 1989 occultation of Star 28-Sgr by Titan. On the other hand, the model simulates latitudinal temperature contrasts in the stratosphere that are significantly weaker than those observed by Voyager 1 which, we suggest, may be partly due to the nonrepresentation of the spatial and temporal variations of the abundances of molecular species and haze. We present diagnostics of the simulated atmospheric circulation underlying the importance of the seasonal cycle and a tentative explanation for the creation and maintenance of the atmospheric superrotation based on a careful angular momentum budget. 相似文献
38.
Herbin J Remmer J 《Revue de géographie alpine / publieé par l'Institute de géographie alpine (Université de Grenoble)》1984,72(1):21-40
Population trends in the German and Austrian Alps between 1971 and 1981 are described. The effects of commune size, tourism, and altitude on population dynamics are considered. 相似文献
39.
The authors attempt to provide a comprehensive review of urbanization in three Melanesian countries (Papua New Guinea, the Solomon Islands, and Vanuatu) and in Fiji. The focus of the paper is on the development and perpetuation of various forms of inequality exemplified by Melanesian urbanization and its colonial origins. 相似文献
40.
1.引言本文评述了当前有限区域中尺度模式提供中纬度强雷暴环境的准确预报以及风暴对环境可能的反馈作用的能力.这里的"中尺度模式"指的是用水平格距Δx=10~100公里作为在静力学原始方程中的有限差分近似.对平流波来说,要有满意的截断误差至少需4—6个格点(Pielke,1981),而要准确地计算非线性波的相互作用,则需近10个格点(Gerrity,1972).因此,这些模式适合模拟的天气现象尺度为Orlanski(1975)定义的中β尺度(25—250公里)上部到中α尺度 相似文献