全文获取类型
收费全文 | 273篇 |
免费 | 7篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 13篇 |
地球物理 | 73篇 |
地质学 | 82篇 |
海洋学 | 39篇 |
天文学 | 60篇 |
综合类 | 1篇 |
自然地理 | 14篇 |
出版年
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 3篇 |
2014年 | 9篇 |
2013年 | 5篇 |
2012年 | 12篇 |
2011年 | 5篇 |
2010年 | 12篇 |
2009年 | 15篇 |
2008年 | 18篇 |
2007年 | 14篇 |
2006年 | 16篇 |
2005年 | 14篇 |
2004年 | 12篇 |
2003年 | 12篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1972年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有285条查询结果,搜索用时 15 毫秒
121.
We propose a new approach to derive spatially-averaged momentum equations for an urban canopy model that resolves buildings
vertically and not horizontally. First, in order to mathematically describe the actual momentum field as a completely continuous
field, the underling concepts of the immersed boundary method are employed, where we assume that (i) the entire simulation
space, including that occupied by buildings, is filled with a fluid, and (ii) an external body force field exists that reduces
the wind speed to zero at all positions coinciding with the space occupied by the buildings. Then, in order to obtain the
required spatially-averaged momentum equations in a self-consistent manner, a spatial-averaging operation is applied to the
Navier–Stokes equations that include a term representing the external force field. The applied spatial-averaging operation
is equivalent to the conventional spatial filtering operation used in large-eddy simulations. To examine the significance
of the subgrid-scale (SGS) stresses of the spatially-averaged momentum equations, a numerical simulation is performed for
a flow around a regular array of cubical blocks with a grid resolution that is sufficient to resolve the blocks. By estimating
the individual terms in the spatially-averaged momentum equations using the simulation results, we show that the SGS stresses
contribute significantly to the spatially-averaged momentum budget, and therefore they should not be neglected in urban canopy
modelling. 相似文献
122.
123.
A. Skopal M. F. Bode M. Bryce J. Meaburn S. Tamura 《Astrophysics and Space Science》1995,224(1-2):559-560
We present optical high-resolution spectroscopy and UBV photometry of the symbiotic binary CH Cyg during the current outburst which began in 1992 February. 相似文献
124.
Takuo Tamura Akira Yoshiasa Kazuaki Iishi Setsuo Takeno Hironobu Maeda Shuichi Emura Kichiro Koto 《Physics and Chemistry of Minerals》1996,23(2):81-88
The local structure around Co, Zn and Sr atoms in incommensurately modulated, melilite-type X2T1 T 2 2 O7 (X=Ca and Sr, T1=Mg, Co and Zn, T2=Si) solid-solutions has been investigated by EXAFS analyses. The modulated structure was confirmed in Ca2-xSrxCoSi2O7 solid-solutions with X=0.0 to 0.6 and for both Ca2Mg1-YCoYSi2O7 and Ca2Mg1-YZnYSi2O7 solid-solutions over the whole compositional range at room temperature. The actual bond-distances determined by the EXAFS method for the T1 site (Co-, Zn-O) in the modulated structure are longer than the mean bond-distances obtained from the X-ray diffraction method. This is attributable to the libration of the T1 tetrahedra. In the Ca1-XSrXCoSi2O7 solid-solution both the Sr-O and Co-O distances by the EXAFS method for the X-site increase from Ca end-member to Sr end-member. These increases are respectively 0.8% and 0.6%. This means the local expansions of the tetrahedral sheets and of the XO polyhedra are well matched. In the modulated Ca2Co1-YMgYSi2O7 and Ca2Zn1-YMgYSi2O7 solid-solutions, the actual Co-O and Zn-O distances for the T1-sites are nearly constant in the whole compositional range. The compositional variations of the local structure around the cations in the solid-solution are different for the X and T1 sites. It is concluded that the local geometric restriction for the size of substituted cation in X site is larger than that in T1 site. The dimension of the tetrahedral sheet puts restriction on the size of the cations situated at the interlayer X sites. In other words, the different behavior of the local geometric restriction between the X and T1 sites is an important feature of the melilite structure and is also related to the modulated structure. 相似文献
125.
A simple relationship has been developed between the wall coordinate y+ and Kolmogorov's length scale using direct numerical simulation (DNS) data for a steady boundary layer. This relationship is then utilized to modify two popular versions of low Reynolds number k–ε model. The modified models are used to analyse a transitional oscillatory boundary layer. A detailed comparison has been made by virtue of velocity profile, turbulent kinetic energy, Reynolds stress and wall shear stress with the available DNS data. It is observed that the low Reynolds number models used in the present study can predict the boundary layer properties in an excellent manner. 相似文献
126.
Minoru Fujii Shinichiro Murashige Yuka Ohnishi Atushi Yuzawa Hitoshi Miyasaka Yoshimi Suzuki Hiroshi Komiyama 《Journal of Oceanography》2002,58(3):438-443
Decomposition experiments were conducted on cultured phytoplankton (Skeletonema costatum) in seawater containing decomposer and consumer of size less than 500 μm. We determined the decomposition rates of bulk particulate
organic matter (POM), the ratio of labile to semi-refractory fractions in the POM, and the POM carbon/ nitrogen (C/N) ratio
during decomposition. To identify the kinetic mechanisms involved in the reactions of different order (e.g., first- and second-order),
we studied the sensitivity of reaction rates to the initial concentration of POM, ranging from 2.4 to 71 mg-C L−1. The results showed that decomposition consists of two first-order reactions: decomposition of labile and of semi-refractory
particulate organic carbon (POC). The decomposition rate constants found for labile (0.13 day−1 at 20°C), and semi-refractory POC (0.008 day−1 at 20°C), and the carbon weight ratio of semi-refractory POC (13% at 20°C), were insensitive to the initial organic matter
concentration. The time-dependence of the C/N ratio was also independent of this initial concentration. The decomposition
rate constants and the content of semi-refractory POC did not change, regardless of the absence or presence of 25–500 μm organisms
in natural seawater.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
127.
Importance of feeding on regenerable parts of prey for juvenile stone flounder Platichthys bicoloratus in estuarine habitats 总被引:3,自引:0,他引:3
Takeshi Tomiyama Satoshi Katayama Michio Omori Hitoshi Honda 《Journal of Sea Research》2005,53(4):297-308
Prey availability is one of the most important factors affecting the quality of nursery grounds. Estuaries play an important role as nursery grounds for juvenile stone flounder, but the mechanism behind the consistently high availability of prey has never been examined. This study investigates which prey is mainly selected by juvenile stone flounder (15–55 mm standard length) in the estuary of the Natori River, northern Japan. In a cage experiment, juveniles showed positive selection for the palps of the spionid polychaete Pseudopolydora kempi in March, and for the siphons of the bivalve Nuttallia olivacea in April, May and June in both sandy and muddy-sand habitats. This selective predation showed that sublethal predation on regenerable parts of invertebrates is important for stone flounder. Nuttallia olivacea, the dominant bivalve in the estuary, was more abundant and in better somatic condition in the sandy area in spite of the stronger siphon-cropping pressure by juvenile stone flounder. These results confirm that sublethal predation on highly abundant benthos plays an important role in forming estuarine habitats into areas of high prey availability for juvenile stone flounder, which leads to their high growth rate. 相似文献
128.
Shinya Kouketsu Hitoshi Kaneko Takeshi Okunishi Kosei Sasaoka Sachihiko Itoh Ryuichiro Inoue Hiromichi Ueno 《Journal of Oceanography》2016,72(3):439-451
We investigated the relationship between chlorophyll a (Chl-a) concentrations estimated from satellite observations and the activity of eddies in the Kuroshio Extension region. High (low) area-averaged Chl-a concentrations were frequently observed in the core of cyclonic (anticyclonic) eddies. Such relationships between Chl-a concentrations and eddy cores were not frequently observed in the southern part of the recirculation gyre, and advection of background meridional gradient of Chl-a by eddy-edge currents accounted for Chl-a spatial variability. Decadal-scale changes of Chl-a concentrations around the Kuroshio Extension were strongly affected by eddy activity and transport but not by large-scale near-surface isopycnal heaving. We also found that decadal changes of nutrient concentrations near the main stream could affect Chl-a concentrations in the southern part of the recirculation gyre via southward transport of eddies and mean flow. 相似文献
129.
130.