全文获取类型
收费全文 | 17198篇 |
免费 | 5518篇 |
国内免费 | 3381篇 |
专业分类
测绘学 | 354篇 |
大气科学 | 1291篇 |
地球物理 | 3329篇 |
地质学 | 12591篇 |
海洋学 | 3403篇 |
天文学 | 22篇 |
综合类 | 989篇 |
自然地理 | 4118篇 |
出版年
2025年 | 4篇 |
2024年 | 432篇 |
2023年 | 538篇 |
2022年 | 821篇 |
2021年 | 861篇 |
2020年 | 854篇 |
2019年 | 866篇 |
2018年 | 797篇 |
2017年 | 855篇 |
2016年 | 903篇 |
2015年 | 884篇 |
2014年 | 1136篇 |
2013年 | 1279篇 |
2012年 | 1178篇 |
2011年 | 1250篇 |
2010年 | 1019篇 |
2009年 | 1176篇 |
2008年 | 1149篇 |
2007年 | 1210篇 |
2006年 | 1221篇 |
2005年 | 971篇 |
2004年 | 930篇 |
2003年 | 849篇 |
2002年 | 705篇 |
2001年 | 612篇 |
2000年 | 662篇 |
1999年 | 531篇 |
1998年 | 387篇 |
1997年 | 393篇 |
1996年 | 341篇 |
1995年 | 286篇 |
1994年 | 239篇 |
1993年 | 191篇 |
1992年 | 151篇 |
1991年 | 115篇 |
1990年 | 84篇 |
1989年 | 78篇 |
1988年 | 46篇 |
1987年 | 28篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 10篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Distribution of the trace elements Cr, Cu, Ni, Pb and Zn in surficial sediments of the river/sea environment in Danang –
Hoian area (Vietnam) was investigated to examine the degree of metal pollution caused by anthropogenic activities. Point sources
from domestic and industrial wastes are identified as dominant contributors of trace element accumulation. Surficial sediments
of Hoian River show extremely high total concentrations of Cu (Average Concentration 295 μg/g), Ni (AC 112 μg/g), Pb (AC 396 μg/g)
and Zn (AC 429 μg/g) that exceed assigned safety levels ER-M. Similarly, the sediments of Han River show high Pb (AC 188 μg/g)
and Zn (AC 282 μg/g) contents. In marine sediments of Thanhbinh beach Pb is also enriched (138 μg/g) above guideline levels.
In contrast the sediments of the Cude River are dominated by trace element concentrations close to background values.
Received: 17 December 1998 · Accepted: 6 May 1999 相似文献
4.
5.
Sally E. Sutton 《地球表面变化过程与地形》1987,12(5):567-570
The magnitude of groundwater resources is poorly correlated with surface catchment area in a group of wadi bottom alluvial aquifers in Northern Oman. It is suggested that this is due to progressive water gap captures across a limestone ridge. 相似文献
6.
Problem on development control of marine source bed hold in Chinese petroleum industry progression. The Hongshuizhuang Formation,Tieling Formation and Xiamaling Formation in the Middle and Upper Proterozoic are important hydrocarbon source beds in northern North China, and investigation of their sedimentary environments and the controls has great significance for petroleum exploration in North China. Based on sedimentology (sequence stratigraphy), palaeoecology, sedimentary geochemistry, and sedimentary palaeogeography, their development pattern is discussed. All these studies indicate that the development controls of the hydrocarbon source beds include a favorite palaeogeographic location, exceeding propagation of biomes in low and middle latitudes, anoxic environments, enrichment of phosphorus element and the adsorption of clay minerals during the preservation of organic matter in the marine carbonates. 相似文献
7.
DONG Yunpeng ZHANG Guowei ZHAO Xia YAO Anping & LIU Xiaoming The Key Laboratory of Continental Dynamics Ministry of Education Department of Geology Northwest University Xi抋n China 《中国科学D辑(英文版)》2004,(4)
Being a composite collisional orogen between North China and South China blocks, the Qinling orogenic belt is the key to understand the composite combination, prolonged evolutionary history and their continental dynamics. The main suture between north and south Qinling, called Shangdan suture zone (SDSZ), had been studied in detail for about twenty years. Recently, another suture zone, called Mianl黣 suture zone (MLSZ), has been identified in the Qinling Mountains. It is characterized b… 相似文献
8.
Paul T. Robinson Department of Earth Sciences Dalhousie University Canada 《Continental Dynamics》2000,(1)
1. Introduction to surface processesThe shape or morphology of Earth's surface is basically the result of the interplay between two competing forces - mountain building and erosion. Tectonic forces, driven by thermal energy from Earth's interior, cause the rocks of the crust to be folded, faulted and uplifted into high plateaus and mountain belts. As soon as uplift begins, the processes of erosion, driven by gravity, start to wear away the rocks. Masses of weathered rock move downhill under t… 相似文献
9.
遂川—热水走滑断裂带特征及其对丰州盆地铀成矿的控制作用 总被引:1,自引:2,他引:1
本文以322矿田为例,对穿越矿田的遂川-热水走滑断裂带的特征及其对铀成矿的控制予以讨论。论述了矿田内铀矿床的形成、分布与遂川-热水走滑断裂带的关系,揭示了丰州拉分盆地的形成与铀成矿的内在联系,认为遂川-热水走滑断裂系是322矿田的主控条件,走滑断裂的脉动性控制了铀成矿的多期多阶段性。最后简要地分析了322矿田的找矿前景和走滑断裂的找矿意义。 相似文献
10.
Natural gas pools with the high contents of CO2 were discovered during exploring the middle fault zone of the Hailar-Tamtsag Basin. So far this kind of gas reservoir with CO2 with characteristics of carbon isotope is spe-cial. The stable carbon isotope of CO2 in the study area is relatively light with δ13 CCO2 values ranging from -13.1‰ to -8.2‰. The 40Ar/36Ar values of associated argon gas range from 916 to 996, with R/Ra of 1.20-1.26. Based on comprehensive analysis, it is believed that the CO2 gas in this study area is of crust mantle source. 相似文献