全文获取类型
| 收费全文 | 2812篇 |
| 免费 | 565篇 |
| 国内免费 | 653篇 |
专业分类
| 测绘学 | 110篇 |
| 大气科学 | 566篇 |
| 地球物理 | 804篇 |
| 地质学 | 1481篇 |
| 海洋学 | 305篇 |
| 天文学 | 186篇 |
| 综合类 | 253篇 |
| 自然地理 | 325篇 |
出版年
| 2024年 | 3篇 |
| 2023年 | 52篇 |
| 2022年 | 112篇 |
| 2021年 | 125篇 |
| 2020年 | 107篇 |
| 2019年 | 122篇 |
| 2018年 | 147篇 |
| 2017年 | 121篇 |
| 2016年 | 144篇 |
| 2015年 | 147篇 |
| 2014年 | 156篇 |
| 2013年 | 161篇 |
| 2012年 | 157篇 |
| 2011年 | 156篇 |
| 2010年 | 128篇 |
| 2009年 | 174篇 |
| 2008年 | 151篇 |
| 2007年 | 126篇 |
| 2006年 | 126篇 |
| 2005年 | 115篇 |
| 2004年 | 83篇 |
| 2003年 | 79篇 |
| 2002年 | 58篇 |
| 2001年 | 85篇 |
| 2000年 | 107篇 |
| 1999年 | 159篇 |
| 1998年 | 122篇 |
| 1997年 | 142篇 |
| 1996年 | 114篇 |
| 1995年 | 79篇 |
| 1994年 | 104篇 |
| 1993年 | 81篇 |
| 1992年 | 56篇 |
| 1991年 | 32篇 |
| 1990年 | 48篇 |
| 1989年 | 25篇 |
| 1988年 | 30篇 |
| 1987年 | 18篇 |
| 1986年 | 15篇 |
| 1985年 | 11篇 |
| 1984年 | 8篇 |
| 1983年 | 7篇 |
| 1982年 | 13篇 |
| 1981年 | 6篇 |
| 1980年 | 4篇 |
| 1979年 | 4篇 |
| 1976年 | 1篇 |
| 1965年 | 1篇 |
| 1958年 | 5篇 |
| 1954年 | 2篇 |
排序方式： 共有4030条查询结果，搜索用时 31 毫秒
81.
82.
Wei Xiao Yufei Qian Xuhui Lee Wei Wang Mi Zhang Xuefa Wen Shoudong Liu Yongbo Hu Chengyu Xie Zhen Zhang Xuesong Zhang Xiaoyan Zhao Fucun Zhang 《中国科学:地球科学(英文版)》2018,61(10):1523-1532
The kinetic fractionation of open-water evaporation against the stable water isotope H_2 ~(18)O is an important mechanism underlying many hydrologic studies that use ~(18)O as an isotopic tracer. A recent in-situ measurement of the isotopic water vapor flux over a lake indicates that the kinetic effect is much weaker(kinetic factor 6.2‰) than assumed previously(kinetic factor14.2‰) by lake isotopic budget studies. This study investigates the implications of the weak kinetic effect for studies of deuterium excess-humidity relationships, regional moisture recycling, and global evapotranspiration partitioning. The results indicate that the low kinetic factor is consistent with the deuterium excess-humidity relationships observed over open oceans.The moisture recycling rate in the Great Lakes region derived from the isotopic tracer method with the low kinetic factor is a much better agreement with those from atmospheric modeling studies than if the default kinetic factor of 14.2‰ is used. The ratio of transpiration to evapotranspiration at global scale decreases from 84±9%(with the default kinetic factor) to 76±19%(with the low kinetic factor), the latter of which is in slightly better agreement with other non-isotopic partitioning results. 相似文献
83.
Xue‐Bin Du Xi‐Nong Xie Yong‐Chao Lu Liang Zhang Wei Peng Yun‐Peng Li 《Geological Journal》2015,50(4):465-476
Pressure measurements using drill stem tests and estimates from log data calculation indicate that three vertically stacked regional pressure compartments exist in the Qikou Depression of Bohai Bay Basin, N. China. The compartments comprise hydrostatic, upper weak, and lower overpressure systems. Laterally, overpressure (pressure coefficient > 1.2) occurs in the deeper areas and weakens gradually from the centre to the margin of the depression. The accumulation of oil and gas exhibits the interesting characteristics of oil‐bearing layers above gas‐bearing layers in the Qikou Depression. The pattern can be accounted for by the evolution of overpressure system, the maturity process of the source rock and the main fault activity. In the late Dongying Formation (Ed, 30 Ma), the lower overpressure system began to form shape, and the hydrocarbon sources generated a large volume of oil. However, because there was no migration pathway, the oil only accumulated in the original strata. In the late Guantao Formation (Ng, 12 Ma), the gas was generated, the upper overpressure system formed gradually, and the activity of the main fault gradually increased. Then, the overpressure pushed the early gathered oil to flow from the lower overpressure system into the upper overpressure system. Afterwards, the activity of the main fault decreased again and remains weak until now. Thus, later generated natural gas cannot keep migrating along the main fault and can only accumulate in the lower overpressure system. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
84.
85.
Xianyu HuangPhilip A. Meyers Weichao WuChenglin Jia Shucheng Xie 《Organic Geochemistry》2011,42(2):156-165
The potential significance of the contributions of long chain iso and anteiso monomethyl alkanes (LC MMAs) from plants of the Lamiaceae, a family that includes many culinary and aromatic herbs of cultural value, to sediments and soil has been evaluated by analyzing 21 specimens from 16 species of Lamiaceae from different environmental settings in Hubei Province, central China, and comparing the results with those from tobacco plants, which are established to be rich in these compounds. Odd numbered iso-alkanes (i-C25 to i-C36) and even numbered anteiso-alkanes (a-C25 to a-C36) are abundant in the Lamiaceae (1.9-23.2% and 0.9-23.8% of total alkanes, respectively). The proportions of LC MMAs are relatively high and comparable to those in the tobacco plant. However, chain lengths in the Lamiaceae are longer than those in tobacco plants and compound-specific δ13C values are more negative than in the tobacco plants, potentially allowing distinction of their different origins. The results imply that Lamiaceae, in addition to some other land plants, can be important sources of LC iso- and anteiso-alkanes in sediments and soils. 相似文献
86.
87.
甘肃省境内新生代沉积中富含动物化石,以早渐新世晚期、晚渐新世、早中新世早期、中中新世晚期、晚中新世、早更新世和晚更新世的哺乳动物化石最为丰富.新生代青藏高原形成、快速隆升,改变了东亚的大气环流和中国的地理格局,使甘肃的气候和地理面貌发生了巨变.甘肃省境内的哺乳动物群在这些变化背景下发生了一次次的更替.本文通过对不同时代... 相似文献
88.
89.
90.