全文获取类型
收费全文 | 24500篇 |
免费 | 175篇 |
国内免费 | 917篇 |
专业分类
测绘学 | 1415篇 |
大气科学 | 1987篇 |
地球物理 | 4522篇 |
地质学 | 11616篇 |
海洋学 | 1025篇 |
天文学 | 1643篇 |
综合类 | 2163篇 |
自然地理 | 1221篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 7篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 4762篇 |
2017年 | 4042篇 |
2016年 | 2578篇 |
2015年 | 241篇 |
2014年 | 87篇 |
2013年 | 29篇 |
2012年 | 993篇 |
2011年 | 2732篇 |
2010年 | 2022篇 |
2009年 | 2324篇 |
2008年 | 1894篇 |
2007年 | 2364篇 |
2006年 | 55篇 |
2005年 | 199篇 |
2004年 | 406篇 |
2003年 | 411篇 |
2002年 | 250篇 |
2001年 | 50篇 |
2000年 | 53篇 |
1999年 | 14篇 |
1998年 | 21篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1991年 | 1篇 |
1981年 | 21篇 |
1980年 | 19篇 |
1976年 | 6篇 |
1941年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
Data Fusion in Distributed Multi-sensor System 总被引:5,自引:0,他引:5
GUOHang YUMin 《地球空间信息科学学报》2004,7(3):214-217
This paper presents a data fusion method in distributed multi-sensor system including GPS and INS sensors“ data processing. First, a residual X^2-test strategy with the corresponding algorithm is designed.Then a coefficient matrices calculation method of the information sharing principle is derived. Finally, the federated Kalman filter is used to combine these independent, parallel, real-time data. A pseudolite (PL) simulation example is given. 相似文献
242.
The present paper focuses on land cover dynamics pattern in Balkhila sub-watershed situated in Garhwal Himalayas. This study
contributes example from human shaped ecosystem in mountainous regions where fragmentation of natural resources is active.
The remote sensing and GIS has been used to understand the land cover dynamics along the topography. The results report that
the land cover dynamics is dependent on the aspect due to sun illumination. The altitude and slope are no more a barrier for
resource extraction and the human activity zone is shifting towards higher altitudes and slopes. The changes are also defined
along the road and settlements. 相似文献
243.
R. Ramakrishnan S. Manthira Moorthi N. Padmanabhan P. Gupta 《Journal of the Indian Society of Remote Sensing》2004,32(1):103-111
Panchromatic data of pixel resolution 5.8 m obtained from IRS-1C and IRS-1D satellites proved to be very useful for mapping
purposes. One of the popular data product is the 70 km swath mosaic which is covered by a combination of 3 CCD line sensors,
each with 4096 pixels. Each CCD-line sensor with different imaging times causes geometric problems of mosaicing three strips
data together. In this paper, we propose the details of the design elements of system that caters to the need for accurate
and automatic multi strip image registration without any second resampling of the data. The systematic geometric correction
grid mapping is improved to facilitate accurate mosaicing by automatic image registration task that makes use of the overlap
data within image strips and image registration is achieved up to sub-pixel level. 相似文献
244.
245.
Doug Hunt 《GPS Solutions》2000,4(1):74-76
The GPS Toolbox is dedicated to highlighting algorithms utilized by GPS engineers and scientists. If you have an interesting
algorithm you would like to share with our readers or if you have a topic you would like to see covered in a future column,
contact us at gps-toolbox@ngs.noaa.gov. To comment on the algorithms presented here, or to leave a request for an algorithm
you may be looking for, visit our Web site (http://www.ngs.noaa.gov/gps-toolbox). ? 2000 John Wiley & Sons, Inc. 相似文献
246.
DGPS and RTK Positioning Using the Internet 总被引:1,自引:0,他引:1
Hisakazu Hada Hideki Sunahara Keisuke Uehara Jun Murai Ivan Petrovski Hideyuki Torimoto Seiya Kawaguchi 《GPS Solutions》2000,4(1):34-44
The Internet as a basis for Real-Time Kinematic (RTK) and differential Global Positioning System (DGPS) service provides many
advantages for worldwide GPS users. Among these advantages are service unification, open architecture, bidirectional communication,
and scalability. The current development of this service allows users to use RTK and DGPS through the Internet with conventional
accuracy over the short and medium baselines. The perspective for this service lies in the field of wide-area augmentation
systems (WASS). At this stage of the Internet-based RTK and DGPS service project, the general concept, system components,
draft standards, and software are developed. ? 2000 John Wiley & Sons, Inc. 相似文献
247.
In this paper, we describe the computational framework of a novel method for solving the challenging problem of probabilistic
finite elements. The method is called Improved Dynamic Bounds (IDB) and was developed recently to improve the efficiency of
the dynamic bounds. The IDB is used in finite element numerical models to calculate time-dependent failure analyses of structures.
In applications, the IDB can speed up the overall simulation process by several orders of magnitude. In applications controlled
by two influential variables (e.g, two-dimensional problem), the computational efficiency is improved by a factor of 769 according
to Rajabalinejad (2009). Applications of IDB indicate the method is most efficient for problems where the number of influential variables are limited.
This is often the case for geotechnical and coastal flood defence systems. The IDB method is applied in this paper to the
17th Street Flood Wall, a component of the flood defence system (levee infra-structure) that failed during the Hurricane Katrina,
to calculate the failure probability of an I-wall. 相似文献
248.
Pitthaya Jamsawang Phermphorn Boathong Warakorn Mairaing Pornkasem Jongpradist 《Landslides》2016,13(5):939-955
This paper presents an analysis of the slope failure of a Suvarnabhumi drainage canal during construction. The Suvarnabhumi drainage canal project includes a large drainage canal with a road on both sides. The width of the bottom of the drainage canal is 48.0 m, the depth of the drainage canal is 3.0 m, and the length of the drainage canal is 10.5 km. Because the project was constructed on very soft Bangkok clay, deep cement mixing (DCM) columns were employed to increase the stability of the excavated canal. The failure of the drainage canal slope occurred 25 days after the end of excavation. The field monitoring data show that lateral movement of the canal slope continuously increased with time, which caused failure due to the instability of the canal slope. The time-dependent deformation and undrained creep behavior of very soft clay was suspected to be the cause of the canal failure. A laboratory investigation of undrained creep behavior and a finite element analysis (FEA) using the soft soil creep (SSC) model were performed to confirm the causes of the canal failure. The results indicate that very soft clay specimens that are subjected to deviator creep stress levels of 70 and 100 % of the peak strength failed by creep rupture within 60 days and 8 min, respectively. The factor of safety for the canal slope, which was obtained from the FEA, shows significant reduction from the initial value of 1.710 to 1.045 within 24 days after the end of excavation due to the effect of undrained creep. This paper also describes a solution method that is applied to a new section of the canal. Field monitoring and an FEA of the new trial section were performed to prove the effectiveness of the solution method. 相似文献
249.
250.