全文获取类型
收费全文 | 193篇 |
免费 | 3篇 |
国内免费 | 10篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 8篇 |
地球物理 | 46篇 |
地质学 | 68篇 |
海洋学 | 17篇 |
天文学 | 46篇 |
综合类 | 7篇 |
自然地理 | 11篇 |
出版年
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 5篇 |
2012年 | 8篇 |
2011年 | 13篇 |
2010年 | 13篇 |
2009年 | 21篇 |
2008年 | 11篇 |
2007年 | 13篇 |
2006年 | 10篇 |
2005年 | 11篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 12篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有206条查询结果,搜索用时 62 毫秒
171.
172.
Yuri Levin 《Monthly notices of the Royal Astronomical Society》2007,377(1):159-167
We examine the effect of inhomogeneous re-ionization on the galaxy power spectrum and the consequences for probing dark energy. To model feedback during re-ionization, we apply an ansatz setting the galaxy overdensity proportional to the underlying ionization field. Thus, inhomogeneous re-ionization may leave an imprint in the galaxy power spectrum. We evolve this imprint to low redshift and use the Fisher-matrix formalism to assess the effect on parameter estimation. We show that a combination of low-redshift ( z = 0.3) and high-redshift ( z = 3) galaxy surveys can constrain the size of cosmological H ii regions during re-ionization. This imprint can also cause confusion when using baryon oscillations or other features of the galaxy power spectrum to probe the dark energy. We show that when bubbles are large, and hence detectable, our ability to constrain w can be degraded by up to 50 per cent. When bubbles are small, the imprint has little or no effect on measuring dark energy parameters. 相似文献
173.
174.
This study concerns the unique physical mechanism of Ekman convergence at the marginal ice zone (ECMIZ) produced by the difference
between air-ice drag and air-water drag. A coupled ice-ocean model is used to show the strength and distribution of the ECMIZ
with respect to Antarctic Intermediate Water (AAIW) formation, which is important for the uptake of carbon dioxide. Strong
ECMIZ occurs in the Atlantic and Pacific sectors from July to October, matched in time and space with ice melting, while it
is significantly weaker due to strongly divergent background winds in the Indian sector. Transport analysis by artificial
tracer experiments reveals the interannual variability of the ECMIZ correlates well with the Southern Annular Mode (SAM).
The downward transport of surface water at the MIZ during a positive SAM (2001) is about 1.4 times as large as that during
a negative SAM (2000). In particular the transport in the Atlantic sector is twice that in the Pacific sector in both years.
Once the downward flux is analyzed in isolation, the contribution from synoptic scale variability is found to increase the
volume transport of surface water in the eastern region of the Pacific. Assuming strong isopycnal mixing, we suggest that
ECMIZ is an important mechanism supplying surface water to the formation of AAIW, and its zonal variability is responsible
for the interbasin differences in AAIW properties. In particular, the increased ECMIZ and surface melt water input in the
Atlantic sector would produce AAIW that is colder and fresher than in the Pacific. 相似文献
175.
Electrical triggering of earthquakes: results of laboratory experiments at spring-block models 下载免费PDF全文
Victor A. Novikov Vladimir I. Okunev Vadim N. Klyuchkin Jing Liu Yuri Ya. Ruzhin Xuhui Shen 《地震科学(英文版)》2017,30(4):167-172
Recently published results of field and laboratory experiments on the seismic/acoustic response to injection of direct current(DC) pulses into the Earth crust or stressed rock samples raised a question on a possibility of electrical earthquake triggering. A physical mechanism of the considered phenomenon is not clear yet in view of the very low current density(10~(-7)–10~(-8) A/m~2) generated by the pulsed power systems at the epicenter depth(5–10 km) of local earthquakes occurred just after the current injection. The paper describes results of laboratory‘‘earthquake' triggering by DC pulses under conditions of a spring-block model simulated the seismogenic fault. It is experimentally shown that the electric triggering of the laboratory ‘‘earthquake'(sharp slip of a movable block of the spring-block system) is possible only within a range of subcritical state of the system, when the shear stress between the movable and fixed blocks obtains 0.98–0.99 of its critical value. The threshold of electric triggering action is about 20 A/m~2 that is 7–8 orders of magnitude higher than estimated electric current density for Bishkek test site(Northern Tien Shan, Kirghizia) where the seismic response to the man-made electric action was observed. In this connection, the electric triggering phenomena may be explained by contraction of electric current in the narrow conductive areas of the faults and the corresponding increase in current density or by involving the secondary triggering mechanisms like electromagnetic stimulation of conductive fluid migration into the fault area resulted in decrease in the fault strength properties. 相似文献
176.
ZHANG Zhaohui GAO Xin Tashiro Yuri Hiroo Ogawa 《中国海洋大学学报(英文版)》2005,4(3):252-256
A method for the analysis of selenium in marine aquatic products by HG-AFS has been investigated. The method is based on the reduction of inorganic selenium to volatile SeH2 which is bubbled out by carrier gas of pure argon, and then swept to Ar-H2 flame quarts atomizer to measure its fluorescence intensity. The hydride generation, transportation, atomization and some instrumental parameters were studied by a kind of orthogonal design. The optimum conditions selected are as follows: reactive acidity, 20% HC1; the amount of NaBH4, 4.9mL; gas flow of argon, 600mLmin^-1; atomizing temperature, 200 ℃ ; negative high voltage, - 300V; light current, 100 mA; integral time, 7s. The detection limit of the presented method is 0.072μgL^-1 for selenium. The calibration curve shows a satisfactory line inthe concentration range from 0.000 to 1.000μgL^-1 Se. The recovery is 95.8%-102.2%. 相似文献
177.
Acta Geotechnica - The classic trapdoor configuration has been useful to examine the changes in stresses expected on buried structures. However, the primary focus of previous studies has been on... 相似文献
178.
Klaus Hornung Yuri G. Malama Khaim S. Kestenboim 《Astrophysics and Space Science》2000,274(1-2):355-363
We report on theoretical efforts to understand the process of vaporization and ion formation upon hypervelocity impact of
small cosmic dust particles on a solid surface. Such collisions occur at the surface of solid bodies within the planetary
system, which do not have an atmosphere as well as in various actual and upcoming space missions for in-situ measurements
of interplanetary, interstellar and cometary dust. The investigation uses Godunov's method to simulate the impact. For the
very high velocitites investigated, the impacting dust particle as well as parts of the target vaporize and some of the vapor
cloud may change to partially ionized. Numerical results of the impact process are communicated for an 80 kms-1impact of a slightly porous SiO2 particle on a compact SiO2surface. Values of the amount of vapor and liquid excavated from the target are given. Ionization rates are calculated for
the example investigated and an estimate is given how this extrapolates to the highest conceivable velocities in the planetary
system (above 100 km s-1).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
179.
Yuri D. Zakharov Nataliya G. Boriskina Alexander V. Ignatyev Kazushige Tanabe Yasunari Shigeta Alexander M. Popov Tamara B. Afanasyeva Haruyoshi Maeda 《Cretaceous Research》1999,20(6):685
In the northwestern circum-Pacific, two main trends in Late Cretaceous temperatures can be recognized. (1) In general, a recurrent warming trend is thought to have begun in the Turonian–Campanian, reaching temperature maxima in the early Late Santonian and early Late Campanian, and temperature minima in the earliest Santonian and perhaps early Campanian. (2) During the Maastrichtian, temperatures dropped sharply, with only a slight warming in the early Late Maastrichtian. The existence of a thermal maximum at the Coniacian–Santonian transition has previously been expected, but is not confirmed by new isotopic results. 相似文献
180.
The problem of the plasma pressure limitations on the rapidity of flux pile-up magnetic reconnection is re-examined, following the claim made by Jardine and Allen (1998) that the limitations can be removed by relaxing the assumption of zero-vorticity two-dimensional plasma flows. It is shown that for a two-dimensional stagnation point flow with nonzero vorticity the magnetic merging rate cannot exceed the Sweet–Parker scaling in a low-beta plasma. The pressure limitation appears to be much less restrictive for weak three-dimensional flux pile-up, provided the perturbation length scale in the third dimension is much less than the global length scale. The actual reconnection rate in the latter case, however, is much lower than this upper estimate unless the current sheet width is also much less than the global scale. 相似文献