全文获取类型
收费全文 | 11999篇 |
免费 | 2148篇 |
国内免费 | 3113篇 |
专业分类
测绘学 | 742篇 |
大气科学 | 2852篇 |
地球物理 | 2949篇 |
地质学 | 6312篇 |
海洋学 | 1337篇 |
天文学 | 475篇 |
综合类 | 1110篇 |
自然地理 | 1483篇 |
出版年
2024年 | 71篇 |
2023年 | 264篇 |
2022年 | 580篇 |
2021年 | 641篇 |
2020年 | 550篇 |
2019年 | 551篇 |
2018年 | 688篇 |
2017年 | 616篇 |
2016年 | 704篇 |
2015年 | 595篇 |
2014年 | 721篇 |
2013年 | 722篇 |
2012年 | 610篇 |
2011年 | 645篇 |
2010年 | 689篇 |
2009年 | 640篇 |
2008年 | 610篇 |
2007年 | 550篇 |
2006年 | 498篇 |
2005年 | 454篇 |
2004年 | 362篇 |
2003年 | 422篇 |
2002年 | 521篇 |
2001年 | 438篇 |
2000年 | 439篇 |
1999年 | 537篇 |
1998年 | 447篇 |
1997年 | 458篇 |
1996年 | 398篇 |
1995年 | 344篇 |
1994年 | 307篇 |
1993年 | 230篇 |
1992年 | 194篇 |
1991年 | 150篇 |
1990年 | 99篇 |
1989年 | 113篇 |
1988年 | 96篇 |
1987年 | 62篇 |
1986年 | 44篇 |
1985年 | 46篇 |
1984年 | 25篇 |
1983年 | 31篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 24篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1958年 | 10篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
101.
Yang Wenbo Qian Zhihao Tu Jiulin Zhou Ziyang Yan Qixiang Fang Yong He Chuan 《地震工程与工程振动(英文版)》2022,(2):517-528
Increased attention has been given to ground-borne vibrations induced by railway vehicles and to the effects of these vibrations as they propagate through the ground into nearby buildings.Various studies,mainly based on numerical methods as well as physical modelling,have been carried out to investigate this problem.To study the dynamic response of tunnels and the surrounding soil due to train-induced vibration loads,a centrifuge te st was conducted with a small-scale model in 1 g and 50 g stres... 相似文献
102.
同源岩浆成因金矿成岩成矿时差的统计研究 总被引:2,自引:2,他引:2
同源岩浆成因金矿的成岩成矿时差是确定矿床与岩浆岩成因关系的重要基础。而中国同源岩浆成因金矿分布十分广泛,前人在成矿学和岩石学方面做了大量的研究,为此本文收集了国内一些典型金矿的成矿和相关同源岩浆岩的同位素测年数据,讨论并定量厘定了该类金矿床成岩成矿时差的分布特征及分布范围。数据统计分析及柯尔莫哥洛夫准则检验结果显示,成矿事件一般同步或略滞后于同源岩浆活动,成岩成矿时差在95%信度下服从正态分布,介于0~16.0Ma,均值约为7.0Ma。因此,若金矿成岩成矿存在着≤16.0Ma的时差,就应该重视二者之间的同源成因联系。同时,笔者也强调:准确的成岩成矿时差应加强对金矿成岩成矿地质背景的研究;重视时差研究与微量元素和同位素示踪相结合,从年代学和地球化学方面对矿床成因作出合理的解释。 相似文献
103.
西藏盐湖卤水蒸发速率的实验与计算 总被引:5,自引:0,他引:5
本文对国内外水面蒸发速率的研究进行了综述,总结了西藏扎布耶盐湖Φ20cm蒸发皿淡水蒸发量与气温、降水、日照的相关关系,提出了改进的扩展彭曼公式法,用于较为准确地计算盐湖卤水蒸发速率,并以西藏扎布耶盐湖为例计算了盐湖卤水蒸发。该方法可以应用于盐湖湖面蒸发与水量均衡计算,也可以应用于盐湖开发中的盐田工艺设计计算与实际生产应用。 相似文献
104.
本文扼要阐明四川省芦山-宝兴地区花岗石石材产出地质特征的基础上,重点讨论花岗石石材的品种、规模和质量。 相似文献
105.
Up to now, 17 Neptune Trojan asteroids have been detected with their orbits being well determined by continuous observations. This paper analyzes systematically their orbital dynamics. Our results show that except for two temporary members with relatively short lifespans on Trojan orbits, the vast majority of Neptune Trojans located within their orbital uncertainties may survive in the solar system age. The escaping probability of Neptune Trojans, through slow diffusion in the orbital element space in 4.5 billion years, is estimated to be ~50%. The asteroid 2012 UW177 classified as a Centaur asteroid by the IAU Minor Planet Center currently is in fact a Neptune Trojan. Numerical simulations indicate that it is librating on the tadpole-shaped orbit around the Neptune's L4 point. It was captured into the current orbit approximately 0.23 million years ago, and will stay there for at least another 1.3 million years in the future. Its high inclination of i ≈ 54° not only makes it the most inclined Neptune Trojan, but also makes it exhibit the complicated and interesting co-orbital transitions between the leading and trailing Trojans via the quasi-satellite orbit phase. 相似文献
106.
107.
WEN Lingjuan LU Huayu & QIANG Xiaoke State Key Laboratory of Loess Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi’an China 《中国科学D辑(英文版)》2005,48(9):1452-1462
In recent years, the Red Clay deposits underlying Quaternary loess on the Chinese Loess Plateau (north China) have attracted more attention because they show a direct and continuous record of past atmos- pheric circulation and palaeoclimatic change. Investiga- tions on Red Clay deposits through multidisciplinary methods have demonstrated an aeolian origin for the Red Clay, like the overlying Quaternary loess. The Red Clay formed during the Miocene and Pliocene[1―13]. However, the type o… 相似文献
108.
109.
通过岩芯及薄片的观察,结合扫描电镜、X衍射和阴极发光等资料分析,对直罗油田长8储层成岩作用及其对储层物性的影响做了研究。结果表明该研究区长8储层砂岩类型以中-细粒长石砂岩为主,碎屑颗粒以次棱角状为主,颗粒分选性好,胶结类型以孔隙-薄膜式胶结为主。研究区主要经历的成岩作用类型有压实作用、胶结作用、溶蚀作用等。整体处于晚成岩A期一晚成岩B期。压实作用、胶结作用使储集空间变小,对储层的破坏性较大,而溶蚀作用使储层物性得到一定的改善。 相似文献
110.
This paper investigates in detail the peak frequency of gyrosynchrotron radiation spectrum with self and gyroresonance absorption
for a model of nonuniform magnetic field. It is found that the peak frequency shifts from lower frequency to higher frequency
with increases in the low-energy cutoff, number density, input depth of energetic electrons, magnetic field strength and viewing
angle. When the number density and temperature of thermal electrons increase, the peak frequency also shifts to a slightly
higher frequency. However, the peak frequency is independent of the energy spectral index, high-energy cutoff of energetic
electrons and the height of the radio source’s upper boundary. It is also found for the first time that there is a good linear
correlation between the logarithms of the peak frequency and the low-energy cutoff, number density, input depth of energetic
electrons, magnetic field strength, and viewing angle, respectively. Their correlation coefficients are higher than 0.95 and
the standard errors are less than 0.06. 相似文献