全文获取类型
收费全文 | 69158篇 |
免费 | 735篇 |
国内免费 | 345篇 |
专业分类
测绘学 | 1406篇 |
大气科学 | 4523篇 |
地球物理 | 13175篇 |
地质学 | 24728篇 |
海洋学 | 6347篇 |
天文学 | 16084篇 |
综合类 | 201篇 |
自然地理 | 3774篇 |
出版年
2022年 | 503篇 |
2021年 | 902篇 |
2020年 | 958篇 |
2019年 | 1047篇 |
2018年 | 2074篇 |
2017年 | 1884篇 |
2016年 | 2190篇 |
2015年 | 1107篇 |
2014年 | 2108篇 |
2013年 | 3628篇 |
2012年 | 2339篇 |
2011年 | 2968篇 |
2010年 | 2719篇 |
2009年 | 3439篇 |
2008年 | 2973篇 |
2007年 | 3052篇 |
2006年 | 2855篇 |
2005年 | 2012篇 |
2004年 | 1959篇 |
2003年 | 1836篇 |
2002年 | 1833篇 |
2001年 | 1604篇 |
2000年 | 1571篇 |
1999年 | 1258篇 |
1998年 | 1257篇 |
1997年 | 1162篇 |
1996年 | 986篇 |
1995年 | 1028篇 |
1994年 | 825篇 |
1993年 | 807篇 |
1992年 | 730篇 |
1991年 | 787篇 |
1990年 | 732篇 |
1989年 | 636篇 |
1988年 | 589篇 |
1987年 | 706篇 |
1986年 | 626篇 |
1985年 | 750篇 |
1984年 | 853篇 |
1983年 | 826篇 |
1982年 | 742篇 |
1981年 | 706篇 |
1980年 | 631篇 |
1979年 | 592篇 |
1978年 | 597篇 |
1977年 | 500篇 |
1976年 | 511篇 |
1975年 | 507篇 |
1974年 | 466篇 |
1973年 | 522篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
211.
212.
Stokes' formula from 1849 is still the basis for the gravimetric determination of the geoid. The modification of the formula,
originating with Molodensky, aims at reducing the truncation error outside a spherical cap of integration. This goal is still
prevalent among various modifications. In contrast to these approaches, some least-squares types of modification that aim
at reducing the truncation error, as well as the error stemming from the potential coefficients, are demonstrated. The least-squares
estimators are provided in the two cases that (1) Stokes' kernel is a priori modified (e.g. according to Molodensky's approach)
and (2) Stokes' kernel is optimally modified to minimize the global mean square error. Meissl-type modifications are also
studied. In addition, the use of a higher than second-degree reference field versus the original (Pizzetti-type) reference
field is discussed, and it is concluded that the former choice of reference field implies increased computer labour to achieve
the same result as with the original reference field.
Received: 14 December 1998 / Accepted: 4 October 1999 相似文献
213.
The Lower Cretaceous Fortress Mountain Formation occupies a spatial and temporal niche between syntectonic deposits at the Brooks Range orogenic front and post‐tectonic strata in the Colville foreland basin. The formation includes basin‐floor fan, marine‐slope and fan‐delta facies that define a clinoform depositional profile. Texture and composition of clasts in the formation suggest progressive burial of a tectonic wedge‐front that included older turbidites and mélange. These new interpretations, based entirely on outcrop study, suggest that the Fortress Mountain Formation spans the boundary between orogenic wedge and foredeep, with proximal strata onlapping the tectonic wedge‐front and distal strata downlapping the floor of the foreland basin. Our reconstruction suggests that clinoform amplitude reflects the structural relief generated by tectonic wedge development and load‐induced flexural subsidence of the foreland basin. 相似文献
214.
Doklady Earth Sciences - 相似文献
215.
H. Müderrisoglu A. Altanlar 《International Journal of Environmental Science and Technology》2011,8(1):159-168
The studies carried out throughout the world have indicated that there are differences between environmental attitudes and environmentally responsible behaviors of undergraduate students. In what ways the environmental attitudes and behaviors of the students who will protect and manage the resources of the country in the future have changed is an important issue? This study was aimed at determining the environmental attitudes and environmentally responsible behaviors of the undergraduate students of Abant Ýzzet Baysal University toward environmental issues. In addition, the effects of the faculty in which the students are enrolled, locality and gender on the determined environmental attitudes and environmentally responsible behaviors of the students were investigated. The data were gathered from 507 students in 2005. To explain the environmental attitudes and environmentally responsible behaviors of undergraduate students toward environmental issues, factor analysis was used with Varimax Rotation method. To determine the changes of the environmental attitudes and environmentally responsible behaviors of the students with regard to the faculty, locality and gender, one-way analysis of variance was used. According to the results, students highly support the environmental attitudes and highly participate only in consumerism behaviors. Finally, it was determined if faculty and gender had an effect on the environmental attitudes and behaviors of the students. 相似文献
216.
217.
Isotope composition of neodymium in neo-Archean banded iron formations of Karelia and Kola Peninsula
Studies of three deposits of neo-Archean banded iron formations from the West Karelian domain (the Kostomuksha deposit) and from the Central Kola block (the Olenegorsk and Kirovogorsk deposits) showed a pronounced difference in the isotope compositions of Nd from quartz and magnetite–hematite interlayers. The less radiogenic Nd of iron-containing layers compared to that of the quartz component may be considered as an indication of the formation mechanism of the treated banded iron formations. Thus, silicon-containing layers are related to submarine volcanism and iron was supplied to the sedimentation zone from other sources. 相似文献
218.
219.
Mara A Morel Victoria Braa Cecilia Martnez-Rosales Clica Cagide Susana Castro-Sowinski 《极地研究(英文版)》2015,(1)
Fildes Peninsula, in King George Island, Antarctica, has a great concentration of international facilities, and it has clearly been affected by human activities. The objective of this 5-year study was ... 相似文献
220.