全文获取类型
| 收费全文 | 11184篇 |
| 免费 | 1146篇 |
| 国内免费 | 1707篇 |
专业分类
| 测绘学 | 401篇 |
| 大气科学 | 500篇 |
| 地球物理 | 1052篇 |
| 地质学 | 4241篇 |
| 海洋学 | 1160篇 |
| 天文学 | 5134篇 |
| 综合类 | 440篇 |
| 自然地理 | 1109篇 |
出版年
| 2024年 | 34篇 |
| 2023年 | 85篇 |
| 2022年 | 255篇 |
| 2021年 | 289篇 |
| 2020年 | 334篇 |
| 2019年 | 373篇 |
| 2018年 | 306篇 |
| 2017年 | 282篇 |
| 2016年 | 311篇 |
| 2015年 | 348篇 |
| 2014年 | 574篇 |
| 2013年 | 626篇 |
| 2012年 | 636篇 |
| 2011年 | 763篇 |
| 2010年 | 812篇 |
| 2009年 | 1059篇 |
| 2008年 | 999篇 |
| 2007年 | 896篇 |
| 2006年 | 845篇 |
| 2005年 | 729篇 |
| 2004年 | 603篇 |
| 2003年 | 523篇 |
| 2002年 | 423篇 |
| 2001年 | 363篇 |
| 2000年 | 329篇 |
| 1999年 | 304篇 |
| 1998年 | 214篇 |
| 1997年 | 97篇 |
| 1996年 | 81篇 |
| 1995年 | 71篇 |
| 1994年 | 68篇 |
| 1993年 | 87篇 |
| 1992年 | 30篇 |
| 1991年 | 32篇 |
| 1990年 | 42篇 |
| 1989年 | 26篇 |
| 1988年 | 23篇 |
| 1987年 | 13篇 |
| 1986年 | 21篇 |
| 1985年 | 26篇 |
| 1984年 | 21篇 |
| 1983年 | 19篇 |
| 1982年 | 16篇 |
| 1981年 | 7篇 |
| 1980年 | 11篇 |
| 1979年 | 2篇 |
| 1978年 | 5篇 |
| 1977年 | 17篇 |
| 1877年 | 1篇 |
| 1875年 | 1篇 |
排序方式： 共有10000条查询结果，搜索用时 343 毫秒
81.
82.
We present a new Very Large Array (VLA) image of Saturn, made from data taken in October 1998 at a wavelength of λ3.6 cm. The moderate ring opening angle (B≈15°) allows us to explore direct transmission of microwave photons through the A and C rings. We find a strong asymmetry of photons transmitted through the A ring, but not in the C ring, a new diagnostic of wake structure in the ring particles. We also find a weak asymmetry between east and west for the far side of the ansae. To facilitate quantitative comparison between dynamic models of the A ring and radio observations, we extend our Monte Carlo radiative transfer code (described in Dunn et al., 2002, Icarus 160, 132-160) to include idealized wakes. We show the idealized model can reproduce the properties of dynamic simulations in directly transmitted light. We examine the model behavior in directly transmitted and scattered light over a range of physical and geometric wake parameters. Finally, we present a wake model with a plausible set of physical parameters that quantitatively reproduces the observed intensity and asymmetry of the A ring both across the planet and in the ansae. 相似文献
83.
84.
85.
86.
R. F. Griffin 《Journal of Astrophysics and Astronomy》1990,11(4):533-540
Photoelectric radial-velocity measurements show that HD 118670 is a double-lined spectroscopic binary in an orbit which is
not quite circular and whose period is about 48 days. Spectral types of K0 V and K7 V would satisfy the photometry and the
mass ratio; the mass function would then suggest the possibility of eclipses. However, actual spectral classification indicates
a luminosity somewhat above the main sequence 相似文献
87.
Randall D. Campbell 《Experimental Astronomy》2002,14(1):57-60
Keck's Long Wavelength Spectrometer (LWS), is the facility instrument used for imaging and spectroscopy in the wavelength
range of 3–28 μm at the Keck Observatory. LWS uses an 128 × 128 Si:As blocked impurity band (BIB) array manufactured by the
Boeing Corporation. This paper discusses the method used for optimizing the detector's operating parameters at a temperature
of 8.5 K and bias voltage of 1.2 V. A process for characterizing detective quantum efficiency of BIB detectors is also presented.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
88.
2D numerical modelling of impact cratering has been utilized to quantify an important depth-diameter relationship for different crater morphologies, simple and complex. It is generally accepted that the final crater shape is the result of a gravity-driven collapse of the transient crater, which is formed immediately after the impact. Numerical models allow a quantification of the formation of simple craters, which are bowl-shaped depressions with a lens of rock debris inside, and complex craters, which are characterized by a structural uplift. The computation of the cratering process starts with the first contact of the impactor and the planetary surface and ends with the morphology of the final crater. Using different rheological models for the sub-crater rocks, we quantify the influence on crater mechanics. To explain the formation of complex craters in accordance to the threshold diameter between simple and complex craters, we utilize the Acoustic Fluidization model. We carried out a series of simulations over a broad parameter range with the goal to fit the observed depth/diameter relationships as well as the observed threshold diameters on the Moon, Earth and Venus. 相似文献
89.
90.