全文获取类型
| 收费全文 | 57162篇 |
| 免费 | 943篇 |
| 国内免费 | 562篇 |
专业分类
| 测绘学 | 1790篇 |
| 大气科学 | 4343篇 |
| 地球物理 | 11189篇 |
| 地质学 | 20597篇 |
| 海洋学 | 4729篇 |
| 天文学 | 12814篇 |
| 综合类 | 196篇 |
| 自然地理 | 3009篇 |
出版年
| 2021年 | 520篇 |
| 2020年 | 542篇 |
| 2019年 | 588篇 |
| 2018年 | 1434篇 |
| 2017年 | 1379篇 |
| 2016年 | 1709篇 |
| 2015年 | 986篇 |
| 2014年 | 1644篇 |
| 2013年 | 3013篇 |
| 2012年 | 1801篇 |
| 2011年 | 2300篇 |
| 2010年 | 1982篇 |
| 2009年 | 2548篇 |
| 2008年 | 2193篇 |
| 2007年 | 2168篇 |
| 2006年 | 2166篇 |
| 2005年 | 1671篇 |
| 2004年 | 1564篇 |
| 2003年 | 1535篇 |
| 2002年 | 1469篇 |
| 2001年 | 1360篇 |
| 2000年 | 1329篇 |
| 1999年 | 1121篇 |
| 1998年 | 1053篇 |
| 1997年 | 1132篇 |
| 1996年 | 949篇 |
| 1995年 | 932篇 |
| 1994年 | 889篇 |
| 1993年 | 756篇 |
| 1992年 | 726篇 |
| 1991年 | 723篇 |
| 1990年 | 740篇 |
| 1989年 | 691篇 |
| 1988年 | 666篇 |
| 1987年 | 748篇 |
| 1986年 | 637篇 |
| 1985年 | 819篇 |
| 1984年 | 845篇 |
| 1983年 | 856篇 |
| 1982年 | 808篇 |
| 1981年 | 679篇 |
| 1980年 | 724篇 |
| 1979年 | 610篇 |
| 1978年 | 573篇 |
| 1977年 | 550篇 |
| 1976年 | 497篇 |
| 1975年 | 488篇 |
| 1974年 | 526篇 |
| 1973年 | 523篇 |
| 1972年 | 342篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
991.
Ben K. H. Soon Steve Scheding Hyung-Kuen Lee Hung-Kyu Lee Hugh Durrant-Whyte 《GPS Solutions》2008,12(4):261-271
This paper presents a simple and effective approach that incorporates single-frequency, L1 time-differenced GPS carrier phase
(TDCP) measurements without the need of ambiguity resolution techniques and the complexity to accommodate the delayed-state
terms. Static trial results are included to illustrate the stochastic characteristics and effectiveness of the TDCP measurements
in controlling position error growth. The formulation of the TDCP observation model is also described in a 17-state tightly-coupled
GPS/INS iterative, extended Kalman filter (IEKF) approach. Preliminary land vehicle trial results are also presented to illustrate
the effectiveness of the TDCP which provides sub-meter positional accuracies when operating for more than 10 min. 相似文献
992.
Zhengzhao Luo Stephens G.L. Emanuel K.A. Vane D.G. Tourville N.D. Haynes J.M. 《Geoscience and Remote Sensing Letters, IEEE》2008,5(1):13-16
This letter presents preliminary results concerning the use of new observations from the A-Train Constellation for testing a new technique of remotely sensing hurricane intensity from space based on modeling a hurricane as a balanced, convectively neutral vortex. The key observational requirements are simultaneous, accurate measurements of cloud-top height, cloudtop temperature, and cloud profiling information across the center of the storm, although there are ways to bypass the need for cloud-top temperature. In this letter, the Moderate Resolution Imaging Spectroradiometer onboard Aqua provides an estimation of the cloud-top temperature, and the near-simultaneous CloudSat observations provide the essential cloud-top height and cloud profiling information. Initial results indicate that the new technique is a promising method for estimating storm intensity when compared post facto to the best track database. Potential uncertainties and room for further refinement of the technique are discussed. 相似文献
993.
Open source, spatial analysis, and activity-travel behaviour research: capabilities of the aspace package 总被引：2，自引：0，他引：2
This paper reports on recent experience with the development of aspace, an Open Source (OS) library for the geographic visualization and analysis of activity-travel behaviour. The paper begins
with an overview of recent progress with respect to the convergence of Open Source technology, spatial analysis, and travel
behaviour research. The remainder of the paper focuses on aspace; a collection of functions that, when combined with data describing the geographical location of daily activities, can be
used to visualize and describe spatial properties of individual and household activity spaces. These properties include: size,
orientation, shape, and the geographical dispersion of activity locations contained within the activity space. Several planar
geometries are used to transform measurable spatial properties into intuitive objects for visualizing spatial patterns of
activity participation. Experiments are conducted, using data from the first wave of the 2003 Toronto Travel Activity Panel
Survey, to demonstrate the potential application of aspace for basic and applied policy-based research into activity-travel behaviour. The toolkit is distributed as a downloadable
‘package’ from the Open Source R Project for Statistical Computing.
相似文献
994.
995.
996.
997.
998.
999.
1000.