全文获取类型
收费全文 | 3920篇 |
免费 | 593篇 |
国内免费 | 437篇 |
专业分类
测绘学 | 922篇 |
大气科学 | 212篇 |
地球物理 | 1172篇 |
地质学 | 1492篇 |
海洋学 | 491篇 |
天文学 | 122篇 |
综合类 | 232篇 |
自然地理 | 307篇 |
出版年
2024年 | 6篇 |
2023年 | 26篇 |
2022年 | 77篇 |
2021年 | 95篇 |
2020年 | 119篇 |
2019年 | 160篇 |
2018年 | 124篇 |
2017年 | 179篇 |
2016年 | 148篇 |
2015年 | 151篇 |
2014年 | 208篇 |
2013年 | 264篇 |
2012年 | 248篇 |
2011年 | 280篇 |
2010年 | 191篇 |
2009年 | 254篇 |
2008年 | 269篇 |
2007年 | 261篇 |
2006年 | 261篇 |
2005年 | 209篇 |
2004年 | 210篇 |
2003年 | 187篇 |
2002年 | 133篇 |
2001年 | 120篇 |
2000年 | 124篇 |
1999年 | 101篇 |
1998年 | 84篇 |
1997年 | 83篇 |
1996年 | 67篇 |
1995年 | 51篇 |
1994年 | 52篇 |
1993年 | 45篇 |
1992年 | 28篇 |
1991年 | 21篇 |
1990年 | 25篇 |
1989年 | 23篇 |
1988年 | 18篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有4950条查询结果,搜索用时 15 毫秒
1.
2.
应用给定换热器结构材料而使换热量最大的两侧换热表面的最佳匹配准则和使可用能损失率最小的最佳运行参数准则。利用两个准则间的关系 ,采用迭代的方式完成换热器的优化设计 ,使换热器的设计达到材料省、换热效果好及运行费用低的目的 ,且能在设计阶段实现。 相似文献
3.
The ordinary kriging method, a geostatistical interpolation technique, was applied for developing contour maps of design storm depth in northern Taiwan using intensity–duration–frequency (IDF) data. Results of variogram modelling on design storm depths indicate that the design storms can be categorized into two distinct storm types: (i) storms of short duration and high spatial variation and (ii) storms of long duration and less spatial variation. For storms of the first category, the influence range of rainfall depth decreases when the recurrence interval increases, owing to the increasing degree of their spatial independence. However, for storms of the second category, the influence range of rainfall depth does not change significantly and has an average of approximately 72 km. For very extreme events, such as events of short duration and long recurrence interval, we do not recommend usage of the established design storm contours, because most of the interstation distances exceed the influence ranges. Our study concludes that the influence range of the design storm depth is dependent on the design duration and recurrence interval and is a key factor in developing design storm contours. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
4.
5.
6.
We carried out a series of linear stability analyses of the radial and low-degree non-radial p modes for stellar models with initial masses of . The stellar models were computed by using convective overshoot distance , 0.25 and 0.40 H P . Our numerical results show that the β Cephei instability strip forms a horn-shaped region pointing upwards near the main sequence on the Hertzsprung–Russell diagram (HRD). The lower part of the instability strip for the radial modes join the zero-age main-sequence (ZAMS) at , while the top of the instability strip extends up to . The instability strip for the non-radial modes is even wider. The overall instability strip is dominated by the radial and non-radial fundamental modes. The first overtone (the radial-order index is also pulsationally unstable. We have shown that the β Cephei stability is almost independent of the overshoot parameter d over used for the stellar models, while it depends critically on the metal abundance. With decreasing metal abundance, the instability region shrinks and eventually disappears for . 相似文献
7.
8.
9.
Luigi R. Bedin † Santi Cassisi Fiorella Castelli Giampaolo Piotto Jay Anderson Maurizio Salaris Yazan Momany Adriano Pietrinferni 《Monthly notices of the Royal Astronomical Society》2005,357(3):1038-1048
We propose a zero-point photometric calibration of the data from the Advanced Camera for Surveys (ACS) Wide Field Channel (WFC) on board the Hubble Space Telescope , based on a spectrum of Vega and the most up-to-date in-flight transmission curves of the camera. This calibration is accurate at the level of a few hundredths of a magnitude. The main purpose of this effort is to transform the entire set of evolutionary models into a simple observational photometric system for ACS/WFC data, and to make them available to the astronomical community. We provide the zero-points for the most used ACS/WFC bands, and give basic recipes for calibrating both the observed data and the models. We also present the colour–magnitude diagram from ACS data of five Galactic globular clusters, spanning the metallicity range −2.2 <[Fe/H] < −0.04 , and we provide fiducial points representing their sequences from several magnitudes below the turn-off to the red giant branch tip. The observed sequences are compared with the models in the newly defined photometric system. 相似文献
10.