全文获取类型
收费全文 | 9490篇 |
免费 | 1680篇 |
国内免费 | 2251篇 |
专业分类
测绘学 | 477篇 |
大气科学 | 1925篇 |
地球物理 | 2570篇 |
地质学 | 4827篇 |
海洋学 | 957篇 |
天文学 | 523篇 |
综合类 | 939篇 |
自然地理 | 1203篇 |
出版年
2024年 | 53篇 |
2023年 | 169篇 |
2022年 | 423篇 |
2021年 | 479篇 |
2020年 | 419篇 |
2019年 | 514篇 |
2018年 | 570篇 |
2017年 | 487篇 |
2016年 | 576篇 |
2015年 | 467篇 |
2014年 | 613篇 |
2013年 | 519篇 |
2012年 | 490篇 |
2011年 | 577篇 |
2010年 | 543篇 |
2009年 | 499篇 |
2008年 | 468篇 |
2007年 | 477篇 |
2006年 | 360篇 |
2005年 | 293篇 |
2004年 | 283篇 |
2003年 | 279篇 |
2002年 | 294篇 |
2001年 | 260篇 |
2000年 | 305篇 |
1999年 | 394篇 |
1998年 | 338篇 |
1997年 | 339篇 |
1996年 | 283篇 |
1995年 | 245篇 |
1994年 | 292篇 |
1993年 | 221篇 |
1992年 | 173篇 |
1991年 | 132篇 |
1990年 | 104篇 |
1989年 | 79篇 |
1988年 | 98篇 |
1987年 | 53篇 |
1986年 | 46篇 |
1985年 | 41篇 |
1984年 | 36篇 |
1983年 | 33篇 |
1982年 | 35篇 |
1981年 | 28篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1975年 | 2篇 |
1958年 | 7篇 |
1954年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
本文对1987~1988年在山东省部分海岛底栖生物调查时发现的异毛虫科5个种进行了详细的描述并配有插图,其中一种为新亚种,另有3个种在我国为首次记录。 相似文献
113.
0.7Ma以来的念青唐古拉山脉隆升过程——来自冰川剥蚀作用的证据 总被引:1,自引:0,他引:1
通过对念青唐古拉山冰碛地层划分及冰碛物同位素测年,发现最早一期冰碛物形成于0.7~0.6MaBP,指示自中更新世以来念青唐古拉山脉开始隆升,主峰地区发生了大规模的冰川剥蚀作用,形成了大面积分布的冰碛高平台;0.2~0.14MaBP念青唐古拉山又快速隆升,并堆积了刚刚伸出各大沟谷口的高侧碛;0.07~0.03MaBP念青唐古拉山再次小规模隆起,形成各大沟谷内的侧碛和终碛垄;0.01Ma BP还有小规模冰川活动。念青唐古拉山主峰地区的冰川剥蚀作用反映出的山脉隆升过程,可较好地与青藏高原的隆起过程相对比,它应是青藏高原隆升的响应。 相似文献
114.
115.
116.
PAH concentrations of 61 surface soil samples collected from the Yellow River Delta (YRD), China were measured to determine occurrence levels, sources, and potential toxicological significance of PAHs. The total concentrations of ∑PAHs ranged from 27 to 753 ng/g d.w., with a mean of 118 ± 132 ng/g. The highest concentrations was found in the mid-southern part of the YRD (753 ng/g), which was associated with the oil exploration. The ratios indicated that the PAHs throughout the YRD were mostly of pyrogenic origin; while various sites in mid-southern part in the region were derived mainly from the petrogenic sources. Multivariate statistical analyses supported that the PAHs in surface soils of the YRD were principally from the coal and biomass combustion, petroleum spills, and/or vehicular emissions. The toxic assessment suggested that the PAHs in soils were at low potential of ecotoxicological contamination level for the YRD. 相似文献
117.
118.
119.
Koji Kiyosugi C. B. Connor D. Zhao L. J. Connor K. Tanaka 《Bulletin of Volcanology》2010,72(3):331-340
Achieving an understanding of the nature of monogenetic volcanic fields depends on identification of the spatial and temporal
patterns of volcanism in these fields, and their relationships to structures mapped in the shallow crust and inferred in the
deep crust and mantle through interpretation of geophysical data. We investigate the spatial and temporal distributions of
volcanism in the Abu Monogenetic Volcano Group, Southwest Japan, and compare these distributions to fault and seismic data
in the brittle crust, and P-wave tomography of the crust and upper mantle. Essential characteristics of the volcano distribution
are extracted by a nonparametric kernel method using an algorithm to estimate anisotropic bandwidth. Overall, E-W elongate
smooth modes in spatial density are identified that are consistent with the spatial extent of P-wave velocity anomalies in
the lower crust and upper mantle, supporting the idea that the spatial density map of volcanic vents reflects the geometry
of a mantle diapir. While the number of basalt eruptions decreased after 0.2 Ma, andesite eruptions increased and overall
volume eruption rate is approximately steady-state. Estimated basalt supply to the lower crust is also constant. This observation
and the spatial distribution of volcanic vents suggest stability of magma productivity and essentially constant two-dimensional
size of the source mantle diapir since 0.46 Ma. 相似文献
120.
Microbial degradation technologies have been developed to restore ground water quality in aquifers polluted by organic contaminants effectively in recent years. However, in course of the degradation, the formation of biofilms in ground water remediation technology can be detrimental to the effectiveness of a ground water remediation project. Several alternatives are available to a remedial design engineer, such as Permeable Reactive Barriers (PRBs) and in -situ bioremediation, Hydrogen Releasing Compounds (HRCs) barrier, Oxygen Releasing Compounds (ORCs) barrier etc. which are efficient and cost- effective technologies. Excessive biomass formation renders a barrier ineffective in degrading the contaminants, Efforts are made to develop kinetics models which accurately determine bio - fouling and bio - filn formation and to control excessive biomass formation. 相似文献