全文获取类型
收费全文 | 3205篇 |
免费 | 363篇 |
国内免费 | 345篇 |
专业分类
测绘学 | 79篇 |
大气科学 | 65篇 |
地球物理 | 873篇 |
地质学 | 936篇 |
海洋学 | 178篇 |
天文学 | 1558篇 |
综合类 | 111篇 |
自然地理 | 113篇 |
出版年
2024年 | 5篇 |
2023年 | 10篇 |
2022年 | 49篇 |
2021年 | 56篇 |
2020年 | 69篇 |
2019年 | 71篇 |
2018年 | 56篇 |
2017年 | 77篇 |
2016年 | 77篇 |
2015年 | 73篇 |
2014年 | 90篇 |
2013年 | 96篇 |
2012年 | 93篇 |
2011年 | 85篇 |
2010年 | 78篇 |
2009年 | 227篇 |
2008年 | 232篇 |
2007年 | 259篇 |
2006年 | 279篇 |
2005年 | 239篇 |
2004年 | 256篇 |
2003年 | 241篇 |
2002年 | 193篇 |
2001年 | 184篇 |
2000年 | 186篇 |
1999年 | 172篇 |
1998年 | 153篇 |
1997年 | 67篇 |
1996年 | 58篇 |
1995年 | 34篇 |
1994年 | 29篇 |
1993年 | 31篇 |
1992年 | 20篇 |
1991年 | 15篇 |
1990年 | 14篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1979年 | 6篇 |
排序方式: 共有3913条查询结果,搜索用时 15 毫秒
991.
Zhang Xiaoliang 《中国地震研究》2006,20(2):159-166
INTRODUCTIONThe constant accumulation of large-range ,high-accuracy GPS observation data makes it possibleto studythe crustal movement in a range as large as possible .The demarcation of crustal blocks withdifferent deformation trends in the studied area and the elimination of the abnormal deformationinformation withinthe blocks ,are prerequisites to gain a correct acquisition of all parameters of theblock movement .The methods of dividing active blocks mainlyinclude 2 classes :one is ba… 相似文献
992.
Effect of gas emissions from Tianchi volcano (NE China) on environment and its potential volcanic hazards 总被引:5,自引:0,他引:5
One of largest eruptions in the Tianchi volcano during the Holocene occurred in about 1000 years ago[1―3]. The volcanic ash erupted had been found in Japan, which is more than 1000 km from the Tianchi volcanic vent[4,5]. Moreover, this eruption has been recognized in the study of Greenland ice core (GISP2)[6,7]. There have been many studies about eruption products of the Tianchi volcano, which dominantly focused on petrological, geochemical and volcanic eruptive dynamic aspects[8―10]. On… 相似文献
993.
Deepankar Choudhury Sanjay S. Nimbalkar 《Geotechnical and Geological Engineering》2006,24(5):1103-1113
Knowledge of seismic active earth pressure behind rigid retaining wall is very important in the design of retaining wall in
earthquake prone region. Commonly used Mononobe-Okabe method considers pseudo-static approach, which gives the linear distribution
of seismic earth pressure in an approximate way. In this paper, the pseudo-dynamic method is used to compute the distribution
of seismic active earth pressure on a rigid retaining wall supporting cohesionless backfill in more realistic manner by considering
time and phase difference within the backfill. Planar rupture surface is considered in the analysis. Effects of a wide range
of parameters like wall friction angle, soil friction angle, shear wave velocity, primary wave velocity and horizontal and
vertical seismic accelerations on seismic active earth pressure have been studied. Results are provided in tabular and graphical
non-dimensional form with a comparison to pseudo-static method to highlight the realistic non-linearity of seismic active
earth pressures distribution. 相似文献
994.
Venanzio R. Greco 《Geotechnical and Geological Engineering》2006,24(3):615-636
The evaluation of the active earth thrust of backfill, on which a surcharge strip acts, is generally made using a hybrid approach
where a thrust increment due to the surcharge strip is calculated using elasticity theory and added to the thrust calculated
in absence of the surcharge strip and in failure condition of the thrust wedge. This paper gives a coherent solution to the
problem, based entirely on Coulomb’s approach. It presents the analytical solution of the active thrust and of the position
of the application point of the thrust. 相似文献
995.
Arsenic fixation on iron-hydroxide-rich and plant litter-containing sediments in natural environments 总被引:2,自引:0,他引:2
Iron-hydroxide-rich and plant litter-containing sediments from natural sites contaminated with uranium mine tailing leachates were examined for their ability to adsorb arsenic. The samples with high contents of iron hydroxides (Fetotal concentration, >300 g kg−1) exhibited remarkable fixation of arsenic (up to 40 g As kg−1). This value corresponded approximately to the supersaturation point for natural iron hydroxides under the present conditions, and it was significantly lower than the value found for synthetic iron hydroxides. There was a strong correlation (R=0.8999) between the concentration of iron and that of arsenic at low arsenic contents, indicating adsorption on strong binding sites. Although all the samples had noticeable contents of organic carbon (plant litter), calcium, and manganese, no obvious effect of these elements on arsenic fixation could be detected. The amount of iron hydroxides was found the only fixation-controlling parameter immediately below a leaching water source. 相似文献
996.
997.
998.
东昆仑断裂带东段玛曲断裂古地震初步研究 总被引:10,自引:0,他引:10
东昆仑活动断裂是青藏高原东北部一条重要的NWW向边界断裂。玛曲断裂位于东昆仑断裂带的最东段。本文通过3个古地震剖面揭示出东昆仑断裂东段玛曲断裂全新世共有4次古地震事件。最新一次古地震事件为距今(1730±50)~(1802±52)a,第二次古地震的时间为距今(3736±57)~(4641±60)a;第三次为距今(8590±70)a;第四次为距今(12200±1700)a。其中第一次和第二次古地震事件的时间较为可靠,两次古地震事件之间的复发间隔为2400a左右,由此认为东昆仑断裂带东段的古震事件之间的复发间隔为2400a左右,古地震的离逝时间为距今(1730±50)~(1802±52)a。 相似文献
999.
天然地震层析成像相对于传统的反射地震方法而言是一种新的经济的勘探方法。这是由于天然地震层析成像所需的观测值直接来自于研究区下方发生的天然微地震,而反射地震却需要在研究区表面进行人工放炮。因此本工作是将天然地震层析成像方法应用于柴达木盆地西部某油田约100km2地区的深层构造的尝试性研究。626个地震事件的3289个P波到时的初步结果与研究区已知的大的构造吻合较好。该模型中非常显著的特征就是观测到一个北西向的背斜。此外,微地震的分布也与研究区中活动断裂带的位置基本一致。 相似文献
1000.
长白山天池火山千年大喷发岩浆含水量研究——熔融包裹体含水量的红外光谱测试 总被引:1,自引:0,他引:1
长白山天池火山在公元一千年左右曾发生过大规模喷发,其产物为大面积分布的灰白色碱流质浮岩和碎屑流,在其斑晶矿物橄榄石、钙铁辉石和碱性长石中均可见到熔融包裹体。在最主要的斑晶矿物——碱性长石中含有数量众多且个体也较大的熔融包裹体,多数含有一个以上的气泡,其中部分含有子晶,根据形貌特征的不同可分为截然不同的两组包裹体。这些熔融包裹体带有大量喷发前地下岩浆的信息,成为研究地下深部的岩浆在复杂的溢流-爆炸喷发中所发生变化的最好媒介。也是本文的研究对象,通过其中挥发份尤其是水的含量,可以推知天池火山发生大喷发的原因。经Nicolet Magna-IR 550红外光谱仪测定,这些熔融包裹体的含水量较高,达1.6%-3.6%,为当时天池火山发生了巨大规模爆炸喷发的原因提供了强有力的证据。但目前红外光谱仪的应用范围还比较有限,有待今后拓宽其应用领域。 相似文献