全文获取类型
收费全文 | 19819篇 |
免费 | 2427篇 |
国内免费 | 3801篇 |
专业分类
测绘学 | 1120篇 |
大气科学 | 2984篇 |
地球物理 | 4037篇 |
地质学 | 10040篇 |
海洋学 | 2728篇 |
天文学 | 2031篇 |
综合类 | 1206篇 |
自然地理 | 1901篇 |
出版年
2024年 | 134篇 |
2023年 | 383篇 |
2022年 | 898篇 |
2021年 | 1115篇 |
2020年 | 991篇 |
2019年 | 1078篇 |
2018年 | 1267篇 |
2017年 | 1177篇 |
2016年 | 1181篇 |
2015年 | 908篇 |
2014年 | 1148篇 |
2013年 | 1258篇 |
2012年 | 1190篇 |
2011年 | 1266篇 |
2010年 | 1152篇 |
2009年 | 1105篇 |
2008年 | 1016篇 |
2007年 | 1049篇 |
2006年 | 942篇 |
2005年 | 519篇 |
2004年 | 441篇 |
2003年 | 500篇 |
2002年 | 579篇 |
2001年 | 536篇 |
2000年 | 430篇 |
1999年 | 463篇 |
1998年 | 387篇 |
1997年 | 388篇 |
1996年 | 339篇 |
1995年 | 323篇 |
1994年 | 286篇 |
1993年 | 238篇 |
1992年 | 220篇 |
1991年 | 146篇 |
1990年 | 132篇 |
1989年 | 138篇 |
1988年 | 98篇 |
1987年 | 77篇 |
1986年 | 68篇 |
1985年 | 53篇 |
1984年 | 51篇 |
1983年 | 54篇 |
1982年 | 45篇 |
1981年 | 31篇 |
1980年 | 25篇 |
1979年 | 33篇 |
1978年 | 21篇 |
1977年 | 25篇 |
1975年 | 23篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
D. S. Drozdov F. M. Rivkin V. Rachold G. V. Ananjeva-Malkova N. V. Ivanova I. V. Chehina M. M. Koreisha Yu. V. Korostelev E. S. Melnikov 《Geo-Marine Letters》2005,25(2-3):81-88
A set of digital maps including geology, Quaternary sediments, landscapes, engineering-geological, vegetation, geocryological and the series of regional sources have been selected to characterize the Russian Arctic coast. Based on this data, new maps of engineering geocryological zoning and zoning of the coast with respect to the intensity of exogenous geological processes and risk of technogenic impacts have been generated at the scales of 1:4,000,000–1:8,000,000. These maps are a tool to assess the impact of industry on the Arctic coast of the country. 相似文献
22.
23.
Various measures including material experiments, centrifuge modeling tests and FEM numerical analyses were performed to study systematically the action mechanism of the geotextile-reinforced cushion under breakwater on soft ground and the effects of the strata characterization and the reinforcement condition on the stability of the breakwater-ground system. In the aspect of controlling the deformation, the geotextile-reinforced cushion under breakwater constrains the lateral displacement of both the embankment and the ground. From the viewpoint of stress, the reinforcement suppressed the range of high stress level in the system. In general, the weaker the ground is and the greater the modulus of the geotextile is, the more effective the reinforcement is. The tensile force in the geotextile is greater in the range of the main part of the embankment. 相似文献
24.
INTRODUCTIONTheDenglouCape ,inthesouthwestoftheLeizhouPeninsula ,isatthenorthmarginoftropicalzone .SeveralresearchesandcartographiesoftheregionalgeomorphologyandQuater narygeology ,whichwerecarriedoutinthepast,allincludethisarea (MGL ,SCSIO ,CAS ,1 978;GPCSGRCZT… 相似文献
25.
26.
Rapid economic developments in East Asian countries have inevitably resulted in environmental degradation in the surrounding seas, and concern for both the environment and protection from pollutants is increasing. Identification of sources of contaminants is essential to environmental pollution management. In this study, the provenance of anthropogenic lead (Pb), a major pollutant of Yellow Sea sediments, was determined for river mouth sediments, including those of the Changjiang, Huanghe, Han, and Geum Rivers, and for age-determined shelf core sediments through the measurement of Pb isotope ratios in the HCl-leached fraction using multi-collector inductively coupled plasma-mass spectrometry (MC ICP/MS). Anthropogenic Pb has accumulated in shelf core sediments since 1910, and its isotope ratios were estimated as 0.863–0.866 and 2.119–2.125 for 207Pb/206Pb and 208Pb/206Pb, respectively, from the mixing relationships of the two endmembers. River mouth sediments exhibited enough distinction in anthropogenic Pb isotope ratios to be discriminated: 0.874 (2.144) in the Huanghe, 0.856 (2.129) in the Han, 0.857 (2.122) in the Geum, and 0.854 (2.101) in the Changjiang for 207Pb/206Pb (208Pb/206Pb), respectively. Although isotope ratios of geogenic Pb in sediments dating before 1910 showed narrow ranges (0.842–0.845 and 2.088–2.100 for 207Pb/206Pb and 208Pb/206Pb, respectively), distinct isotope ratios in each core permitted source identification of sediments in the Yellow Sea based on geographic locations and the geogenic Pb of each river. By comparing the isotope ratios of the estimated anthropogenic Pb to source-related materials, the provenances of anthropogenic Pb in Chinese river sediments were presumed to be Chinese coal or ore, which is also a major source of atmospheric particulate Pb. The anthropogenic Pb in the shelf core sediments in the northern Yellow Sea originated from northern Chinese cities such as Beijing and Tianjin through atmospheric pathways. Pb isotope ratios indicated that Pb in Korean river sediments was characteristic of local Korean ores. 相似文献
27.
Yu. A. Rylov 《Astrophysics and Space Science》1989,158(2):297-333
The model of the pulsar magnetosphere filled with massless charged particles (rest massm=0) is considered. The gas of charged massless particles can be found in two different phases: (1) dynamical phase (DP), when the particles move with nonvanishing energy along some base line, determined by the electromagnetic field only, (2) statical phase (SP), when the particles have vanishing energy =0. The pulsar magnetosphere occurs to be divided into regions of different types: (a) the accelerating regions (DP-regions) containing only DP, (b) the capture regions, containing only SP, (3) leaky capture regions, where DP moves through SP. The leaky capture regions are the active regions, which are responsible for the pulsar radioemission. In the case of oblique magnetic moment the equation for the capture surface has been obtained. The capture region is formed around this surface. Expressions for jumps of the electromagnetic field, the current density and the charge density on the capture region boundary have been obtained. The problem of the pulsar magnetosphere is stated mathematically in the case of oblique magnetic moment and ejection of only electrons. 相似文献
28.
29.
30.