全文获取类型
收费全文 | 159篇 |
免费 | 10篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 12篇 |
地球物理 | 42篇 |
地质学 | 47篇 |
海洋学 | 26篇 |
天文学 | 34篇 |
综合类 | 1篇 |
自然地理 | 10篇 |
出版年
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 7篇 |
2012年 | 6篇 |
2011年 | 11篇 |
2010年 | 12篇 |
2009年 | 9篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 9篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有174条查询结果,搜索用时 15 毫秒
61.
62.
N. Prithivikumaran M. Fernandez Gomez J.J. Lopez Gonzalez S.P. Bagare N. Rajamanickam 《Astrophysics and Space Science》2002,280(4):319-324
The Franck-Condon (FC) factors (transition probabilities) and r-centroids have been evaluated by the reliable numerical integration procedure for the bands of the A
3 φ4 →X
3 φ4 system of astrophysical molecule CoH, using a suitable potential. The dissociation energy D
0
0 = 2.5 ± 0.05 eV for the electronic ground state of CoH has been estimated by fitting Hulburt-Hirschfelder function to the
experimental potential energy curve, using the correlation coefficient.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
63.
Vieira L.E.A. Gonzalez W.D. Echer E. Guarnieri F.L. Prestes A. Gonzalez A.L.C. Santos J.C. Dal Lago A. Schuch N.J. 《Solar physics》2003,217(2):383-394
In this work we present a methodology to estimate the geomagnetic symmetric index (Sym) based on the wavelet analysis of the time series of the H component of the geomagnetic field measured at mid-latitude stations localized at Kakioka (KAK), Honolulu (HON), Hermanus (HER) and San Juan (SJG). A case study of the intense geomagnetic storm of 17–22 February 1999, caused by intense southward magnetic fields just behind an interplanetary shock driven by a magnetic cloud, is shown as an example of the procedure of derivation of the symmetric index and the capabilities of this analysis to improve the study of the coupling of the solar wind and the Earth's magnetosphere. Other examples are shown in order to demonstrate the applicability of the methodology to different magnetospheric conditions. It is shown that the long period variations of the symmetric index are linearly correlated to variations at the same periods of the H component of the geomagnetic field and that the contribution of short period variations to the symmetric index are biased by localized current systems such as the partial ring current and the field aligned currents. 相似文献
64.
An expression for the magnetopause reconnection power based on the dawn-dusk component of the reconnection electric field, that reduces to the substorm parameter ? for the limit that involves equal geomagnetic (BG) and magnetosheath (BM) magnetic field amplitudes at the magnetopause, is contrasted with the expression based on the whole reeonnection electric field vector (Gonzalez, 1973). The correlation examples of this report show that this (more general) expression for the reconnection power seems to correlate with the empirical dissipation parameter UT (Akasofu, 1981), with slightly better correlation coefficients than those obtained from similar correlations between the parameter ? and UT Thus, these (better) correlations show up for the more familiar values of the ratio BG/BM > 1. Nevertheless, the (expected) relatively small difference that seems to exist between these correlation coefficients suggests that, for practical purposes, the parameter ? could be used as well (instead of the more general expression) in similar correlation studies due to its simpler format. On the other hand, studies that refer mainly to the difference in the magnitudes of ? and of the more general expression are expected to give results with less negligible differences. 相似文献
65.
Dal Lago A. Vieira L.E.A. Echer E. Gonzalez W.D. de Gonzalez A.L.C. Guarnieri F.L. Schuch N.J. Schwenn R. 《Solar physics》2004,222(2):323-328
We have compared characteristics of 38 halo coronal mass ejections observed on the Sun by the Large Angle and Spectrometric Coronagraph onboard SOHO with their corresponding counterparts observed near Earth by the magnetic field and plasma instruments onboard the ACE, WIND and SOHO satellites, in the period from January 1997 to April 2001. We only have selected events that have some associated interplanetary ejecta structure at 1 AU and we have compared the lateral expansion speeds of these halo CMEs and the corresponding ejecta speeds near Earth. We found that there is a high correlation between these two speeds. The results are very similar to the study done by Lindsay et al. (1999) using observations made by Solwind and SMM coronagraphs, and Helios-1 and PVO plasma and interplanetary field data from the period of 1979 to 1988. Also, we reviewed the relation between the CME-related shock transit speed to Earth and the ejecta speeds near Earth. This kind of relation is very important to estimate ejecta speeds of events for which no interplanetary observations are available. 相似文献
66.
:Reactivation of metasomatized mantle lithosphere may occur during continental extension,which is an important component of plate tectonics.The lower most part of the metasomatized domains in the subcontinental mantle lithosphere can be locally enriched in CO2.Therefore,partial melting of these metasomatized domains may play a crucial role in the global carbon cycle.However,little is known about this process and up until now few numerical constraints are available.Here we address this knowledge gap and use a 2-D high resolution petrological-thermomechanical model to assess lithospheric rifting.CO2 degassing and melting.We test 4 lithospheric thicknesses:90,110,130 and 200 km with a 10 km thick metasomatized layer at the base using CO2 of 2 wt.%in the bulk composition.The carbonate enriched layer is stable below^3 GPa(>110 km)for a temperature of 1300℃;therefore,we only observe degassing patterns for lithospheric models that are 130 km and 200 km thick.The metasomatized layer for the 130 km thick lithosphere mostly comprises carbonatite melting,whereas in the 200 km thick scenario propagation of melt development from kimberlites to carbonatites occurs as the metasomatic mantle is exhumed during extension.The numerical models fit well into natural rifting zones of the European Cenozoic Rift System for young(shallow)and of the North Atlantic Rift for old(thick)lithosphere. 相似文献
67.
Bivalve population health: Multistress to identify hot spots 总被引:3,自引:0,他引:3
X. de Montaudouin I. Paul-Pont P. Gonzalez F. Jude M. Baudrimont F. Le Grand L. Bourasseau 《Marine pollution bulletin》2010,60(8):1307-118
This study investigated some stress (metals, parasites) and response (immunity, metallothionein) factors in two cockle and two Manila clam populations. Data from eight seasons were averaged to obtain global baseline values. Stress/response characteristics of each population were compared to population health status that was determined through population dynamics parameters. Four different scenarios were discussed: (1) a lightly stressed cockle population with correct population health but with a risk of deterioration (hot spot); (2) a lightly stressed introduced cockle population threatened of extinction. In this case ecological factors were suspected; (3) a moderately stressed clam population with moderate adaptative response. The population was sustainable but the level of stress should not increase (hotspot); and (4) a stressed clam population and unfavourable ecological conditions preventing clam settlement. This monitoring highlighted that the discrepancy between population health and stress levels could be due to insufficient response by bivalves and/or by unfavourable ecological factors. 相似文献
68.
铜陵狮子山地区中酸性侵入岩锆石SHRIMP U-Pb定年及岩浆作用的深部过程 总被引:13,自引:11,他引:13
铜陵狮子山地区中酸性侵入岩锆石SHRIMP U-Pb定年结果表明,白茫山辉石二长闪长岩、鸡冠山和大团山石英二长闪长岩以及胡村花岗闪长岩的年龄分别为:138.21 ±0.82Ma、139.9 ±1.1Ma、139.3 ±1.2Ma和140.9 ±1.2Ma.岩浆侵位顺序为花岗闪长岩→石英二长闪长岩→辉石二长闪长岩.根据锆石SHRIMP U-Pb年龄变化范围,推测该区岩浆活动持续的时间约为15Ma,且岩浆属脉动式多次侵位,后期岩浆侵位的热使早期岩体中已结晶的锆石发生熔解、重结晶,形成新的锆石.地下深部岩浆活动频繁,形成了多级岩浆房,使得本区的莫霍面界线不明显. 相似文献
69.
The effects of acute and chronic exposure to tributyltin (TBT) were examined in bioassays using horseshoe crab (Limulus polyphemus) embryos and “trilobite” larvae. Larvae had>95% survival after 24-h exposure to nominal concentrations of 1–500 μg l?1 TBT. Survival was also high following 48-h and 72-h exposure to ≤100 μg l?1 TBT; >50% mortality was seen only after 48-h and 72-h exposure to 500 μg l?1 TBT. Estimated median lethal concentrations (LC50) were >1000 μg l?1, 742 μg l?1, and 594 μg l?1 for 24-h, 48-h, and 72-h exposure, respectively. Much higher toxicity LC50=42 μg l?1) was seen following chronic exposure of larvae to TBT. Acute exposure to TBT significantly increased the time required by larvae to molt into the first-tailed stage. LC50 for horseshoe crab embryos exposed to TBT were 44 μg l?1, 20 μg l?1, and 14 μg l?1 for 24, 48, and 72 h acute exposure, indicating that this earlier developmental stage was about 30–40 fold more susceptible to TBT than larvae. Horseshoe crabs are highly tolerant of TBT in comparison to early developmental stages of other marine arthropods. The ability of horseshoe crab embryos and larvae to survive in the presence of organotin pollution suggests the possibility of bioaccumulation and movement into the estuarine food chain via shorebirds, gulls, and fish. 相似文献
70.
D. N. Thomas T. C. Rolph J. Shaw S. Gonzalez de Sherwood & Z. Zhuang 《Geophysical Journal International》1998,134(3):856-866
Palaeomagnetic results are presented from a volcanic sequence in Zhijin County, Guizhou Province, Southern China. The lavas and associated volcanic breccias comprising the sequence represent a southern extension of the Emeishan volcanic province. Biostratigraphic dating of interbedded limestone units and stratigraphic constraints indicate that the section formed during the late Permian (∼263–255 Ma), and is thus somewhat older than the Emei stratotype section in Sichuan Province, and close in age to reported estimates of the termination of the Permo-Carboniferous (Kiaman) reverse superchron. Rock magnetic analyses and reflected light microscopy indicate that the magnetic mineralogy of the lava units is dominated by fresh, primary magnetites containing a significant fraction of single-domain grains. Thermal demagnetization behaviour of the breccia units is poor, but most lava samples have one or two components of remanence above 250 °C. The normal polarity characteristic remanence held by the lavas implies a post-Kiaman age for this succession and suggests that the termination of the Kiaman occurred prior to 263 Ma, supporting recently published estimates. According to standard criteria, Thellier palaeointensity results from the lavas are of good quality and reveal that the dipole field strength was comparatively low shortly after the termination of the superchron. 80 per cent of samples record relative VDM values in the range 42–52 per cent of the present-day value, supporting recent studies of mid-Kiaman field intensity. This suggests that a low-energy dipole existed at least between 300 and 255 Ma and does not appear to have been confined to the stable reverse polarity interval. 相似文献