全文获取类型
收费全文 | 6673篇 |
免费 | 1247篇 |
国内免费 | 1588篇 |
专业分类
测绘学 | 283篇 |
大气科学 | 1400篇 |
地球物理 | 1759篇 |
地质学 | 3212篇 |
海洋学 | 1001篇 |
天文学 | 219篇 |
综合类 | 840篇 |
自然地理 | 794篇 |
出版年
2024年 | 25篇 |
2023年 | 108篇 |
2022年 | 313篇 |
2021年 | 345篇 |
2020年 | 321篇 |
2019年 | 294篇 |
2018年 | 359篇 |
2017年 | 352篇 |
2016年 | 412篇 |
2015年 | 299篇 |
2014年 | 391篇 |
2013年 | 361篇 |
2012年 | 340篇 |
2011年 | 362篇 |
2010年 | 409篇 |
2009年 | 364篇 |
2008年 | 302篇 |
2007年 | 309篇 |
2006年 | 265篇 |
2005年 | 202篇 |
2004年 | 189篇 |
2003年 | 206篇 |
2002年 | 199篇 |
2001年 | 184篇 |
2000年 | 205篇 |
1999年 | 311篇 |
1998年 | 292篇 |
1997年 | 277篇 |
1996年 | 230篇 |
1995年 | 241篇 |
1994年 | 212篇 |
1993年 | 170篇 |
1992年 | 151篇 |
1991年 | 92篇 |
1990年 | 91篇 |
1989年 | 75篇 |
1988年 | 50篇 |
1987年 | 37篇 |
1986年 | 23篇 |
1985年 | 25篇 |
1984年 | 25篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 17篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1958年 | 4篇 |
排序方式: 共有9508条查询结果,搜索用时 0 毫秒
41.
42.
Acta Geochimica - The Sandaowanzi gold deposit is an extremely Au-rich deposit in the Northern Great Hinggan Range in recent years. Zircon U–Pb geochronology, Hf isotope analysis, and the... 相似文献
43.
Bhavya P. S. Min Jun-Oh Kim Min-Seob Jang Hyo Keun Kim Kwanwoo Kang Jae Joong Lee Jae Hyung Lee Dabin Jo Naeun Kim Myung Joon Kim Yejin Lee Junbeom Lee Chang Hwa Bae Hyeonji Yoo Hyeju Park Sanghoon Yun Mi Sun Lee Sang Heon 《Ocean Science Journal》2019,54(4):515-528
Ocean Science Journal - Investigations on marine N2 fixation have gained momentum since 1960s with eventual establishments of relevant methodologies to identify species involved and quantify the... 相似文献
44.
Journal of Geographical Sciences - As information technology has been applied more broadly and transportation infrastructure has improved, persistent debate has existed as to the question of... 相似文献
45.
When travelling, people are accustomed to taking and uploading photos on social media websites, which has led to the accumulation of huge numbers of geotagged photos. Combined with multisource information (e.g. weather, transportation, or textual information), these geotagged photos could help us in constructing user preference profiles at a high level of detail. Therefore, using these geotagged photos, we built a personalised recommendation system to provide attraction recommendations that match a user's preferences. Specifically, we retrieved a geotagged photo collection from the public API for Flickr (Flickr.com) and fetched a large amount of other contextual information to rebuild a user's travel history. We then created a model-based recommendation method with a two-stage architecture that consists of candidate generation (the matching process) and candidate ranking. In the matching process, we used a support vector machine model that was modified for multiclass classification to generate the candidate list. In addition, we used a gradient boosting regression tree to score each candidate and rerank the list. Finally, we evaluated our recommendation results with respect to accuracy and ranking ability. Compared with widely used memory-based methods, our proposed method performs significantly better in the cold-start situation and when mining ‘long-tail’ data. 相似文献
46.
47.
Two photometric follow-up transit (primary eclipse) observations on WASP-43 b and four observations on TrES-3 b are performed using the Xuyi Near-Earth Object Survey Telescope. After differential photometry and light curve analysis, the physical parameters of the two systems are obtained and are in good match with the literature. Combining with transit data from a lot of literature, the residuals (O ? C) of transit observations of both systems are fitted with the linear and quadratic functions. With the linear fitting, the periods and transit timing variations (TTVs) of the planets are obtained, and no obvious periodic TTV signal is found in both systems after an analysis. The maximum mass of a perturbing planet located at the 1:2 mean motion resonance (MMR) for WASP-43 b and TrES-3 b is estimated to be 1.826 and 1.504 Earth mass, respectively. By quadratic fitting, it is confirmed that WASP-43 b may have a long-term TTV which means an orbital decay. The decay rate is shown to be P? = (?0.005248 ± 0.001714) s·yr?1, and compared with the previous results. Based on this, the lower limit of the stellar tidal quality parameter of WASP-43 is calculated to be , and the remaining lifetimes of the planets are presented for the different values of the two systems, correspondingly. 相似文献
48.
Journal of Oceanology and Limnology - Little is known about the roles of dynorphin and Kappa opioid receptor (KOR) in mollusks. In this study, we aim to determine the distribution of dynorphin A... 相似文献
49.
50.
This paper is a brief account of the essential points of geomechanics initited in China by Prof. J. S. Lee in the 1920's and some important results achieved by some Chinese petroleum geologists in recent years by applying geomechanics to the exploration and prospecting of oil and gas in eastern China. 相似文献