全文获取类型
收费全文 | 8683篇 |
免费 | 340篇 |
国内免费 | 129篇 |
专业分类
测绘学 | 166篇 |
大气科学 | 720篇 |
地球物理 | 2056篇 |
地质学 | 3059篇 |
海洋学 | 806篇 |
天文学 | 1270篇 |
综合类 | 37篇 |
自然地理 | 1038篇 |
出版年
2021年 | 115篇 |
2020年 | 153篇 |
2019年 | 156篇 |
2018年 | 204篇 |
2017年 | 198篇 |
2016年 | 243篇 |
2015年 | 200篇 |
2014年 | 260篇 |
2013年 | 476篇 |
2012年 | 284篇 |
2011年 | 411篇 |
2010年 | 379篇 |
2009年 | 475篇 |
2008年 | 398篇 |
2007年 | 407篇 |
2006年 | 342篇 |
2005年 | 299篇 |
2004年 | 284篇 |
2003年 | 301篇 |
2002年 | 241篇 |
2001年 | 203篇 |
2000年 | 221篇 |
1999年 | 165篇 |
1998年 | 153篇 |
1997年 | 136篇 |
1996年 | 145篇 |
1995年 | 133篇 |
1994年 | 125篇 |
1993年 | 102篇 |
1992年 | 101篇 |
1991年 | 70篇 |
1990年 | 100篇 |
1989年 | 82篇 |
1988年 | 86篇 |
1987年 | 99篇 |
1986年 | 87篇 |
1985年 | 119篇 |
1984年 | 135篇 |
1983年 | 126篇 |
1982年 | 108篇 |
1981年 | 86篇 |
1980年 | 60篇 |
1979年 | 75篇 |
1978年 | 72篇 |
1977年 | 66篇 |
1976年 | 63篇 |
1975年 | 69篇 |
1974年 | 55篇 |
1973年 | 72篇 |
1972年 | 33篇 |
排序方式: 共有9152条查询结果,搜索用时 15 毫秒
501.
David H. Kaplan 《The Professional geographer》1995,47(2):115-125
This study utilizes linguistically disaggregated region-to-region migration data between 1981 and 1986 to demonstrate that French and English speaking Canadians react differently to place attributes. A series of log transformed linear regression models suggest that the two populations differ very little in their response to traditional labor market variables but that they diverge dramatically in their response to the linguistic composition of each region. Each group prefers regions with a greater percentage of their own co-linguists, but Francophones are less sensitive than Anglophones to linguistic composition. 相似文献
502.
Observations of the diurnal evolution of the planetary boundary layer over the Amazon rain forest, made at sites close to the confluence of the Solimões and Negro rivers (approximately at 3°S, 60°W) near Manaus, Amazonas, Brazil, show the existence of a diurnal rotation of the wind near the surface and the frequent presence of low-level nocturnal wind maxima. These circulations are shown to be plausibly explained as elements of a river and land breeze circulation induced by the thermal contrast between the rivers and the adjacent forest. 相似文献
503.
A climatology of Southern Hemisphere extratropical cyclones 总被引:4,自引:0,他引:4
A climatology of extratropical cyclones determined by an objective automatic scheme applied to 15 years (1975–89) of once-daily Australian Bureau of Meteorology hemispheric analyses is presented. Contour maps of the positions of formation (cyclogenesis), dissipation (cyclolysis) together with other cyclone statistics are presented. The distribution of cyclones through the hemisphere was found to be dominated by a permanent high latitude core coincident with the circumpolar trough. During the winter and intermediate seasons, two mid latitude branches are evident in the cyclone density originating in the Tasman Sea and South American sectors, both spiraling poleward and merging with the circumpolar core in the Southern Oceans. Systems were observed to move in an castsouth-east direction, away from their location of formation, exhibiting peak speeds of migration in the mid latitudes. Little seasonality was evident in the densitiy distribution of cyclones through the Southern Oceans, but a considerable amount was found in their central pressure.
Correspondence to: I Simmonds 相似文献
504.
505.
Robert S. Webb Jonathan T. Overpeck David M. Anderson Bruce A. Bauer Mildred K. England Wendy S. Gross E. Ann Meyers Michael M. Worobec 《Journal of Paleolimnology》1993,9(1):69-75
Conclusion The World Data Center-A for Paleoclimatology, located in the NOAA/NGDC Paleoclimatology Program, is committed to providing the scientific community with easy access to all paleoenvironmental data. Efforts to make archived data readily available include international coordination of data acquisition, management, and distribution, sponsoring workshops and data cooperatives to facilitate the compilation of important data sets, development of a browse and visualization software package (PaleoVu), and dispersal of archived data on magnetic media or over ANONYMOUS FTP/INTERNET. The program publishes a semi-annual newsletter that highlights latest developments and accomplishments in the area of paleoenvironmental data for global change research. Contributions to the newsletter are welcome from researchers describing their efforts to coordinate the free flow of paleoclimate data throughout the international scientific community.For information on the program or to be added to the mailing list contact Mrs Mildred England (phone: 303-497-6227; Fax: 303 497-6513; e-mail: MKE@mail.ngdc.noaa.gov), NOAA National Geophysical Data Center, Paleoclimatology Program/World Data Center-A for Paleoclimatology, 325 Broadway, E/GC Boulder, CO 80303 USA 相似文献
506.
A simple model of plate generation from mantle flow 总被引:2,自引:0,他引:2
David Bercovici 《Geophysical Journal International》1993,114(3):635-650
507.
Large-scale deformation associated with ridge subduction 总被引:1,自引:0,他引:1
Eric L. Geist Michael A. Fisher David W. Scholl 《Geophysical Journal International》1993,115(2):344-366
508.
509.
510.