全文获取类型
收费全文 | 345篇 |
免费 | 19篇 |
国内免费 | 33篇 |
专业分类
大气科学 | 8篇 |
地球物理 | 71篇 |
地质学 | 246篇 |
海洋学 | 38篇 |
天文学 | 1篇 |
综合类 | 5篇 |
自然地理 | 28篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 11篇 |
2016年 | 2篇 |
2015年 | 7篇 |
2014年 | 25篇 |
2013年 | 7篇 |
2012年 | 23篇 |
2011年 | 40篇 |
2010年 | 29篇 |
2009年 | 29篇 |
2008年 | 43篇 |
2007年 | 14篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 13篇 |
2003年 | 11篇 |
2002年 | 12篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1985年 | 1篇 |
排序方式: 共有397条查询结果,搜索用时 15 毫秒
171.
172.
173.
174.
核桃坪铅锌铜多金属矿的靶区选择、评价及矿床发现中,由浅入深的物化探工作,在8个综合物化探异常区都找到多金属硫化物矿体,金厂河矿区实现隐伏深部找矿的重大突破。并总结出了一套合理的找矿勘查技术。 相似文献
175.
176.
177.
采用室内实验生态学方法研究近江牡蛎的耗氧率和排氨率。结果表明,在实验温度13~33℃范围内,近江牡蛎的耗氧率(RO)和排氨率(RN)与体重(W)均呈负相关,可用Y=aW-b表示。耗氧率和温度的关系可表示为RO=-c+b1t-b2 t2,耗氧率为0.626~2.354 mg.g-1.h-1;在温度13~28℃范围内,耗氧率随温度的升高而增加,28℃时,耗氧率达最大值,温度升高至33℃时,耗氧率反而下降。排氨率与温度的关系可表示为RN=c1e d1t,排氨率为0.075~0.318 mg.g-1.h-1,且随温度的升高,排氨率呈持续升高趋势。近江牡蛎呼吸和排泄Q10值范围分别为0.631~3.399和1.046~2.288。在28℃,不同规格近江牡蛎呼吸氧原子数与排出氨氮原子数的比值(nO/nN)均达到最大值。方差分析表明,体重、温度及二者的交互作用对近江牡蛎的耗氧率和排氨率均有极显著的影响(P<0.01)。近江牡蛎的日常代谢明显高于标准代谢,耗氧率和排氨率平均值分别提高46.8%和67.7%。 相似文献
178.
R.S. Hetem B.A. de WittL.G. Fick A. FullerS.K. Maloney L.C.R. MeyerD. Mitchell G.I.H. Kerley 《Journal of Arid Environments》2011,75(1):20-28
Globally, pastoral practices have transformed habitats, which often lead to desertification. With climate change predicted to exacerbate desertification, adaptation provides the best survival strategy for agriculturally important herbivores. We investigated body temperature, water turnover, physical activity and microclimate selection of Angora goats inhabiting transformed and intact sites in the Eastern Cape Province, South Africa. Although goats on both sites responded similarly under most environmental conditions, when goats were subjected to a thermal stress, imposed by shearing, those inhabiting the transformed site had a faster rate of rise in abdominal temperature (0.38 versus 0.31 °C h−1, P = 0.0009), displayed an increased 24-h abdominal temperature amplitude (1.8 versus 1.6 °C, P = 0.01) and were generally less active (3.9 versus 5.2 activity units) compared to goats inhabiting the intact site. Post-shearing, goats inhabiting the transformed site had higher water turnover rates (P < 0.0001) and selected more variable microclimates (P < 0.0001) than goats inhabiting the intact site, despite obtaining less water from their diet (P = 0.01). Goats inhabiting the transformed site were more water dependent and more susceptible to thermal stresses in their environment than were those inhabiting the intact site. Coping with thermal challenges will be essential for Angora goats if the mohair industry is to thrive under future climate change scenarios. 相似文献
179.
Nicholas R. Longrich 《Cretaceous Research》2011,32(3):264-276
At the end of the Cretaceous, 65.5 million years ago, the giant ceratopsids Triceratops and Torosaurus dominated North America’s dinosaur fauna. The origins of these giant ceratopsids, the Triceratopsini, are poorly understood. This paper describes Titanoceratops ouranos, a giant ceratopsid from the late Campanian (73-74 Ma) of New Mexico, and the earliest known triceratopsin. The holotype was previously interpreted as an aberrant and exceptionally large specimen of Pentaceratops sternbergi, but the animal does not show the diagnostic features of Pentaceratops. Instead, cladistic analysis shows that Titanoceratops is the sister taxon of a clade formed by Eotriceratops, Triceratops, and Torosaurus. With an estimated mass of 6.5 tons, Titanoceratops is among the largest dinosaurs known from the Campanian of North America, and rivaled Triceratops in size. The recognition of Titanoceratops suggests that giant chasmosaurines evolved once, among the Triceratopsini, and that the group evolved large size five million years earlier than previously thought. The giant horned dinosaurs probably originated in the southern part of the North American continent during the Campanian but only became widespread during the Maastrichtian. 相似文献
180.
波司甸铜矿床是云南易门铜矿区南段赋存于中元古界昆阳群落雪组中的典型喷流—热卤水沉积型铜矿床.矿床地质特征、成矿控制因素的研究,对云南易门铜矿区南段的找矿工作具有较好的指导意义. 相似文献