全文获取类型
收费全文 | 214篇 |
免费 | 33篇 |
国内免费 | 45篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 38篇 |
地球物理 | 67篇 |
地质学 | 75篇 |
海洋学 | 42篇 |
天文学 | 8篇 |
综合类 | 28篇 |
自然地理 | 29篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 8篇 |
2020年 | 14篇 |
2019年 | 8篇 |
2018年 | 11篇 |
2017年 | 12篇 |
2016年 | 6篇 |
2015年 | 12篇 |
2014年 | 10篇 |
2013年 | 3篇 |
2012年 | 10篇 |
2011年 | 2篇 |
2010年 | 7篇 |
2009年 | 12篇 |
2008年 | 13篇 |
2007年 | 14篇 |
2006年 | 9篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有292条查询结果,搜索用时 15 毫秒
251.
Yue Li Shijin Zhao Hongye Pei Shi Qian Jingjie Zang Xinyue Dang Huan Yang 《中国科学:地球科学(英文版)》2018,61(7):925-939
Glycerol Dialkyl Glycerol Tetraethers(GDGTs)serve as important tools for the quantitative reconstruction of paleoclimate and paleoecology in both continental and marine environments.Previous studies of GDGTs in the terrestrial environments focused primarily on the soils from the relatively warm-humid or cold-dry regions.However,it is still unclear how GDGTs respond to environmental variables in the cold-humid regions.Here,we collected soils along an altitudinal transect of Mountain(Mt.)Changbai,which has a typical cold-humid climate,to investigate the distribution of GDGTs and the response of GDGT-based proxies to changes in climate along the transect.The shift in the distribution of archaeal isoprenoidal GDGTs(iso GDGTs)revealed that the archaeal community varied significantly along the transect,which can affect the relationship between TEX_(86)and mean annual air temperature(MAT).In addition,the increased temperature seasonality at higher altitudes exerted a significant impact on TEX_(86).We proposed a global calibration of TEX_(86)for the growing season temperature reconstruction in the soil environments:T=85.19×TEX_(86)-46.30(R~2=0.84,p0.001).The methylation indices for 5-methyl branched GDGTs(br GDGTs)including MBT′_(5me)and MBT_(5/6),showed correlation with soil water content but no relationship with MAT,indicating that MBT′_(5me)and MBT_(5/6)from cold-humid environments may be not suitable for temperature and altitude reconstruction.In contrast,the recently developed p H proxies,including MBT′_(6me)(the methylation index for 6-methyl br GDGTs),CBT(Cyclisation index of Branched Tetraethers),IR_(IIa’)(Isomer ratio of IIa′)and IR_(IIIa′)(Isomer ratio of IIIa′)exhibited significant correlations with soil p H,suggesting these proxies can still be used for soil p H reconstruction in the coldhumid regions.The combination of MBT′_(5me)and MBT′_(6me)was strongly related to different types of climate(cold-dry,warmhumid,cold-humid,and warm-dry).For example,MBT′_(5me)0.65 and MBT′_(6me)0.55 are diagnostic for the cold-humid climate.Thus,the combination of MBT′_(5me)and MBT′_(6me)has the potential as a tool for the identification of different types of paleoclimate. 相似文献
252.
254.
255.
Hartmut Spetzler Guennadi Sobolev Anatoli Koltsov Arno Zang Ivan C. Getting 《Pure and Applied Geophysics》1991,137(1-2):95-112
In this paper we report results obtained from various friction experiments under direct and oblique shear loading conditions. We used four rock types of varying brittleness (quartzite, anhydrite, limestone, pyrophyllite) with different surface roughness. The observations concentrate on the time span several milliseconds before dynamic failure occurs. During this period a premonitory, unstable phase of slip (slip 2) occurs. This differs importantly from a premonitory, stable process (slip 1) with durations of hundreds of seconds. On smooth surfaces slip 2 is usually observed with ductile rocks and less reliably with brittle rocks. Slip 2 is mostly accompanied by acoustic emissions, which increase in rate of occurrence and in magnitude until the stick-slip event. Foreshocks are observed during approximately 50% of the slip 2 events on rough surfaces. Foreshocks far exceed the acoustic noise level, which is also prevalent before stick-slip events on rough surfaces. In the direct shear experiment, where two faults are being loaded simultaneously, in about 20% of the cases precursory slip 2 was observed on the opposite side on which the final stick-slip event occurred. 相似文献
256.
本文报道了用动态(dynamic)技术,经抽取、气相色谱法测定海水中溶存甲烷浓度的方法.详细论述了溶存甲烷经起泡、收集(吸附)、解吸和检测四步完成,并逐步讨论了起泡时间、起泡气体流速以及收集温度等有关因子对测定的影响。结果表明:该方法分析速度快、精密度好、灵敏度高,可广泛应用于海上现场测定海水中溶存的甲烷。 相似文献
257.
Zang Junling Liu Changqing Cheng Xianggai Zeng Jianhui Liang Yunxia Li Mingzhi Li Chao 《河南气象》2007,(3)
小麦吸浆虫的发生和温、湿度条件关系密切。平舆县3月中、下旬和4月份的地温适宜成虫活动,4月份降水较多时,很适宜吸浆虫发生。防治措施以麦播期和蛹期防治为主,穗期成虫补治为辅,严把麦播期、孕穗期(蛹期)和抽穗期(成虫期)"三关"防治。 相似文献
258.
259.
260.
The westerly anomalies over the tropical pacific and their dynamical effect on the enso cycles during 1980–1994 总被引:3,自引:0,他引:3
In this paper, the zonal wind anomalies in the lower troposphere over the tropical Pacific during 1980–1994 are analyzed by using the observed data. The results show that during the formation of the 1982/83, 1986/87 and 1991 / 92 ENSO events, there were the larger westerly anomalies in the lower troposphere over the equatorial Pacific. Moreover, it is explained by using the correlation analyses that the westerly anomalies over the equatorial Pacific could cause the warm episodes of the equatorial central and eastern Pacific. A simple air-sea coupled model is used to discuss theoretically the dynamical effect of the observed westerly anomalies of wind stress near the sea surface of the equatorial Pacific on the ENSO cycle occurred in the period of 1981–1983. It is shown by using the theoretical calculations of the equatorial oceanic Kelvin wave and Rossby waves responding to the forcing of the observed anomalies of zonal wind stress near the sea surface of the equatorial Pacific that the westerly anomalies of wind stress near the sea surface of the equatorial Pacific make significant dynamical effect on the ENSO cycles occurred in the period of 1982–1983. 相似文献