全文获取类型
收费全文 | 28638篇 |
免费 | 64篇 |
国内免费 | 125篇 |
专业分类
测绘学 | 813篇 |
大气科学 | 2030篇 |
地球物理 | 4647篇 |
地质学 | 13678篇 |
海洋学 | 1814篇 |
天文学 | 4816篇 |
综合类 | 162篇 |
自然地理 | 867篇 |
出版年
2023年 | 18篇 |
2022年 | 30篇 |
2021年 | 31篇 |
2020年 | 28篇 |
2019年 | 40篇 |
2018年 | 3384篇 |
2017年 | 3191篇 |
2016年 | 1878篇 |
2015年 | 208篇 |
2014年 | 205篇 |
2013年 | 220篇 |
2012年 | 1338篇 |
2011年 | 3100篇 |
2010年 | 2933篇 |
2009年 | 3000篇 |
2008年 | 2337篇 |
2007年 | 3053篇 |
2006年 | 247篇 |
2005年 | 643篇 |
2004年 | 519篇 |
2003年 | 591篇 |
2002年 | 356篇 |
2001年 | 106篇 |
2000年 | 113篇 |
1999年 | 80篇 |
1998年 | 77篇 |
1997年 | 87篇 |
1996年 | 75篇 |
1995年 | 46篇 |
1994年 | 31篇 |
1993年 | 57篇 |
1992年 | 34篇 |
1991年 | 42篇 |
1990年 | 27篇 |
1989年 | 34篇 |
1988年 | 36篇 |
1987年 | 42篇 |
1986年 | 52篇 |
1985年 | 41篇 |
1984年 | 45篇 |
1983年 | 43篇 |
1982年 | 46篇 |
1981年 | 48篇 |
1980年 | 52篇 |
1979年 | 35篇 |
1977年 | 20篇 |
1976年 | 25篇 |
1975年 | 23篇 |
1974年 | 20篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
132.
133.
Lars E. Sjöberg 《Journal of Geodesy》2008,82(9):565-567
Through each of two known points on the ellipsoid a geodesic is passing in a known azimuth. We solve the problem of intersection
of the two geodesics. The solution for the latitude is obtained as a closed formula for the sphere plus a small correction,
of the order of the eccentricity of the ellipsoid, which is determined by numerical integration. The solution is iterative.
Once the latitude is obtained, the longitude is determined without iteration. 相似文献
134.
Spin rate estimation of sounding rockets using GPS wind-up 总被引:2,自引:1,他引:1
Carrier phase wind-up is a well-known effect that arises from the relative rotation between a transmitting and receiving antenna.
In GPS measurements at L1 frequency, this effect translates into an error of 19.029 cm per full relative rotation of antennas.
Since this effect is independent of the satellite elevation for pure rotation about the antenna boresight axis, it is usually
absorbed by the clock estimation in navigation algorithms. Therefore, the impact of wind-up is usually neglected for applications
that do not require accuracies to the cm level like RTK. However, in receiving platforms with high rotation rate, the accumulated
wind-up value can be important and actually be larger than receiver noise or even ionospheric variations. Therefore, in such
scenarios, the wind-up contribution can be isolated and used as a source of information to compute the spin rate of such platforms
using an appropriate combination of GPS observables. This work shows some results of a coarse, yet simple, approach to monitor
the rotation angle and spin-rate of spin stabilized sounding rockets flown by DLR. 相似文献
135.
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
136.
This paper presents a continuous version of the model of distribution dynamics to analyse the transition dynamics and implied
long-run behaviour of the EU-27 NUTS-2 regions over the period 1995–2003. It departs from previous research in two respects:
first, by introducing kernel estimation and three-dimensional stacked conditional density plots as well as highest density regions
plots for the visualisation of the transition function, based on Hyndman et al. (J Comput Graph Stat 5(4):315–336, 1996), and second, by combining Getis’ spatial filtering view with kernel estimation to explicitly account for the spatial dimension of the
growth process. The results of the analysis indicate a very slow catching-up of the poorest regions with the richer ones,
a process of shifting away of a small group of very rich regions, and highlight the importance of geography in understanding
regional income distribution dynamics.
相似文献
Manfred M. FischerEmail: |
137.
138.
139.
140.