全文获取类型
收费全文 | 399篇 |
免费 | 15篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 14篇 |
地球物理 | 91篇 |
地质学 | 127篇 |
海洋学 | 82篇 |
天文学 | 87篇 |
综合类 | 3篇 |
自然地理 | 15篇 |
出版年
2022年 | 2篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 13篇 |
2015年 | 10篇 |
2014年 | 17篇 |
2013年 | 14篇 |
2012年 | 11篇 |
2011年 | 15篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 16篇 |
2007年 | 19篇 |
2006年 | 24篇 |
2005年 | 22篇 |
2004年 | 22篇 |
2003年 | 29篇 |
2002年 | 9篇 |
2001年 | 25篇 |
2000年 | 20篇 |
1999年 | 15篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1971年 | 2篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1963年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有421条查询结果,搜索用时 15 毫秒
361.
Naoki Ikegaya Aya Hagishima Jun Tanimoto Yudai Tanaka Ken-ichi Narita Sheikh Ahmad Zaki 《Boundary-Layer Meteorology》2012,143(2):357-377
We performed a series of wind-tunnel experiments under neutral conditions in order to create a comprehensive database of scalar
transfer coefficients for street surfaces using regular block arrays representing an urban environment. The objective is to
clarify the geometric dependence of scalar transfer phenomena on rough surfaces. In addition, the datasets we have obtained
are necessary to improve the modelling of scalar transfer used for computational simulations of urban environments; further,
we can validate the results obtained by numerical simulations. We estimated the scalar transfer coefficients using the salinity
method. The various configurations of the block arrays were designed to be similar to those used in a previous experiment
to determine the total drag force acting on arrays. Our results are summarized as follows: first, the results for cubical
arrays showed that the transfer coefficients for staggered and square layouts varied with the roughness packing density. The
results for the staggered layout showed the possibility that the mixing effect of air can be enhanced for the mid-range values
of the packing density. Secondly, the transfer coefficients for arrays with blocks of non-uniform heights were smaller than
those for arrays with blocks of uniform height under conditions of low packing density; however, as the packing density increased,
the opposite tendency was observed. Thirdly, the randomness of rotation angles of the blocks in the array led to increasing
values of the transfer coefficients under sparse packing density conditions when compared with those for cubical arrays. 相似文献
362.
Seitaro Urakawa Shin-ichiro Okumura Tsuyoshi Sakamoto Shinsuke Abe Kohei Kitazato Sunao Hasegawa Nobuyuki Kawai Shogo Nagayama Michitoshi Yoshida 《Icarus》2011,215(1):17-26
We present lightcurve observations and multiband photometry for 107P/Wilson-Harrington using five small- and medium-sized telescopes. The lightcurve has shown a periodicity of 0.2979 day (7.15 h) and 0.0993 day (2.38 h), which has a commensurability of 3:1. The physical properties of the lightcurve indicate two models: (1) 107P/Wilson-Harrington is a tumbling object with a sidereal rotation period of 0.2979 day and a precession period of 0.0993 day. The shape has a long axis mode (LAM) of L1:L2:L3 = 1.0:1.0:1.6. The direction of the total rotational angular momentum is around λ = 310°, β = −10°, or λ = 132°, β = −17°. The nutation angle is approximately constant at 65°. (2) 107P/Wilson-Harrington is not a tumbler. The sidereal rotation period is 0.2979 day. The shape is nearly spherical but slightly hexagonal with a short axis mode (SAM) of L1:L2:L3 = 1.5:1.5:1.0. The pole orientation is around λ = 330°, β = −27°. In addition, the model includes the possibility of binary hosting. For both models, the sense of rotation is retrograde. Furthermore, multiband photometry indicates that the taxonomy class of 107P/Wilson-Harrington is C-type. No clear rotational color variations are confirmed on the surface. 相似文献
363.
Ji Yi Lee Yong Pyo Kim Naoki Kaneyasu Hidetoshi Kumata Chang-Hee Kang 《Atmospheric Research》2008,90(1):91-98
The levels of PM.25 PAHs at Mt. Halla site, Jeju Island, a background site in Korea were observed between March 1999 and March 2002. A seasonal variation was observed for the particulate PAHs concentrations with high levels during cold season similar to Gosan, a nearby coastal background site, due to the seasonal variations of fossil fuel usage in Asia. The total average concentration of ambient particulate PAHs was 404 ± 579 pg m− 3, about one order lower than the ambient level at Gosan. However, the ratios of the anthropogenic inorganic ion concentrations between Mt. Halla and Gosan were smaller, 1.5 for non sea-salt (nss) sulfate and 2.7 for nitrate. Two possible explanations for these characteristics are (1) two sites measured different air parcels and/or (2) the effect of local emissions were different at two sites. Based on the Bep/BaP ratio result, upper air wind direction data, backward trajectory analysis, and LIDAR measurement data at Gosan, it was found that the degree of the effects of local emissions to the sampling sites be the major reason for the different PAHs levels at two sites though, in some cases, the air parcels arriving at Mt. Halla were different from those arriving at Gosan. For secondary aerosol such as nss sulfate, the lower concentration difference indicates both site are affected by regional transport. It points that the measurement result for directly emitted species such as PAHs at Gosan might be significantly influenced by local emissions. 相似文献
364.
365.
Haruo Yoshida 《Celestial Mechanics and Dynamical Astronomy》1984,32(1):73-86
It is shown that the characteristic exponents can be exactly expressed for a type of second order linear ordinary differential equations with periodic coefficients (Hill's equation) which appear as the variational equations of certain periodic solutions of dynamical systems. Key points are the transformation of the equation to the Gauss' hypergeometric differential equation, and evaluation of the trace of monodormy matrix in the complex plane of the independent variable. Two simple examples are given for which the stability of periodic solutions is rigorously analyzed. 相似文献
366.
367.
The equations of motion of the planar three-body problem split into two parts, called an external part and an internal part. When the third mass approaches zero, the first part tends to the equations of the Kepler motion of the primaries and the second part to the equations of motion of the restricted problem.We discuss the Hill stability from these equations of motion and the energy integral. In particular, the Jacobi integral for the circular restricted problem is seen as an infinitesimal-mass-order term of the Sundman function in this context. 相似文献
368.
Ryo Yamazaki Kazunori Kohri Aya Bamba Tatsuo Yoshida Toru Tsuribe Fumio Takahara 《Monthly notices of the Royal Astronomical Society》2006,371(4):1975-1982
We study the emission from an old supernova remnant (SNR) with an age of around 105 yr and that from a giant molecular cloud (GMC) encountered by the SNR. When the SNR age is around 105 yr, proton acceleration is efficient enough to emit TeV γ-rays both at the shock of the SNR and that in the GMC. The maximum energy of primarily accelerated electrons is so small that TeV γ-rays and X-rays are dominated by hadronic processes, π0 -decay and synchrotron radiation from secondary electrons, respectively. However, if the SNR is older than several 105 yr, there are few high-energy particles emitting TeV γ-rays because of the energy-loss effect and/or the wave-damping effect occurring at low-velocity isothermal shocks. For old SNRs or SNR–GMC interacting systems capable of generating TeV γ-ray emitting particles, we calculated the ratio of TeV γ-ray (1–10 TeV) to X-ray (2–10 keV) energy flux and found that it can be more than ∼102 . Such a source showing large flux ratio may be a possible origin of recently discovered unidentified TeV sources. 相似文献
369.
Examined here is a hypothetical idea of the splitting of the subtropical gyre in the western North Pacific on the basis of two independent sources of data,i.e., the long-term mean geopotential-anomaly data compiled by the Japanese Oceanographic Data Center and the synoptic hydrographic (STD) data taken by the Hakuho Maru in the source region of the Kuroshio and the Subtropical Countercurrent in the period February and March 1974. Both of the synoptic and the long-term mean dynamic-topographic maps reveal three major ridges, which indicate that the western subtropical gyre is split into three subgyres. Each subgyre is made up of the pair of currents, the Kuroshio and the Kuroshio Countercurrent, the Subtropical Countercurrent and a westward flow lying just south of the Countercurrent (18°N–21°N), and the northern part of the North Fquatorial Current and an eastward flow at around 18°N. The subgyres are more or less composed of a train of anticyclonic eddies with meridional scales of between 300 and 600 km, so that the volume transport of the subgyres varies by a factor of two or more from section to section. The upper-water characteristics also support the splitting of the subtropical gyre; the water characteristics are fairly uniform within each subgyre, but markedly different between them. The northern rim of each subgyre appears as a sharp density front accompanied by an eastward flow. The bifurcations of the sharp density fronts across the western boundary current indicate that the major part of the surface waters in the North Equatorial Countercurrent is not brought into the Kuroshio. The western boundary current appears as a continuous feature of high speed, but the waters transported change discontinuously at some places. 相似文献
370.
Kozo Yoshida 《Progress in Oceanography》1980,9(2):83-131
A simple three-dimensional model of a time-dependent coastal upwelling is discussed for time scales of several days to a week, with the linear, two-layer, flat-bottom and approximation. Emphasis is placed on the effects of longshore scales determined by the longshore variabilities in the wind stress distributions. The responses of the inshore motions are shown to depend critically on the longshore scales. For a certain wide range of the scales, the system reveals dominantly baroclinic responses and a full development of the poleward coastal undercurrent without β effect. Somewhat detailed discussions are given on the coastal upwelling, the coastal jet and the poleward undercurrent, which are interpreted simply as the orbital velocities of the forced Kelvin-type waves. 相似文献