全文获取类型
收费全文 | 68350篇 |
免费 | 986篇 |
国内免费 | 458篇 |
专业分类
测绘学 | 1799篇 |
大气科学 | 4881篇 |
地球物理 | 12815篇 |
地质学 | 26633篇 |
海洋学 | 5670篇 |
天文学 | 14046篇 |
综合类 | 238篇 |
自然地理 | 3712篇 |
出版年
2021年 | 473篇 |
2020年 | 485篇 |
2019年 | 563篇 |
2018年 | 3888篇 |
2017年 | 3603篇 |
2016年 | 2783篇 |
2015年 | 879篇 |
2014年 | 1211篇 |
2013年 | 2461篇 |
2012年 | 2381篇 |
2011年 | 4436篇 |
2010年 | 4119篇 |
2009年 | 4732篇 |
2008年 | 3834篇 |
2007年 | 4466篇 |
2006年 | 1860篇 |
2005年 | 2012篇 |
2004年 | 1845篇 |
2003年 | 1837篇 |
2002年 | 1619篇 |
2001年 | 1181篇 |
2000年 | 1141篇 |
1999年 | 905篇 |
1998年 | 908篇 |
1997年 | 903篇 |
1996年 | 748篇 |
1995年 | 732篇 |
1994年 | 694篇 |
1993年 | 632篇 |
1992年 | 608篇 |
1991年 | 558篇 |
1990年 | 555篇 |
1989年 | 543篇 |
1988年 | 529篇 |
1987年 | 603篇 |
1986年 | 540篇 |
1985年 | 667篇 |
1984年 | 709篇 |
1983年 | 663篇 |
1982年 | 580篇 |
1981年 | 651篇 |
1980年 | 539篇 |
1979年 | 518篇 |
1978年 | 477篇 |
1977年 | 463篇 |
1976年 | 413篇 |
1975年 | 401篇 |
1974年 | 400篇 |
1973年 | 410篇 |
1971年 | 236篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
2.
Costijn Zwart Niels C. Munksgaard Alain Protat Naoyuki Kurita Dionisia Lambrinidis Michael I. Bird 《水文研究》2018,32(15):2296-2303
This work provides a comprehensive physically based framework for the interpretation of the north Australian rainfall stable isotope record (δ18O and δ2H). Until now, interpretations mainly relied on statistical relationships between rainfall amount and isotopic values on monthly timescales. Here, we use multiseason daily rainfall stable isotope and high resolution (10 min) ground‐based C‐band polarimetric radar data and show that the five weather types (monsoon regimes) that constitute the Australian wet season each have a characteristic isotope ratio. The data suggest that this is not only due to changes in regional rainfall amount during these regimes but, more importantly, is due to different rain and cloud types that are associated with the large scale circulation regimes. Negative (positive) isotope anomalies occurred when stratiform rainfall fractions were large (small) and the horizontal extent of raining areas were largest (smallest). Intense, yet isolated, convective conditions were associated with enriched isotope values whereas more depleted isotope values were observed when convection was widespread but less intense. This means that isotopic proxy records may record the frequency of which these typical wet season regimes occur. Positive anomalies in paleoclimatic records are most likely associated with periods where continental convection dominates and convection is sea‐breeze forced. Negative anomalies may be interpreted as periods when the monsoon trough is active, convection is of the oceanic type, less electric, and stratiform areas are wide spread. This connection between variability of rainfall isotope anomalies and the intrinsic properties of convection and its large‐scale environment has important implications for all fields of research that use rainfall stable isotopes. 相似文献
3.
4.
5.
Zsolt Sándor Bálint Érdi Carl D. Murray 《Celestial Mechanics and Dynamical Astronomy》2002,84(4):355-368
The dynamics of co-orbital motion in the restricted three-body problem are investigated by symplectic mappings. Analytical and semi-numerical mappings have been developed and studied in detail. The mappings have been tested by numerical integration of the equations of motion. These mappings have been proved to be useful for a quick determination of the phase space structure reflecting the main characteristics of the dynamics of the co-orbital problem. 相似文献
6.
7.
8.
Cygnus A was the first hyper-active galaxy discovered, and it
remains by far the closest of the ultra-luminous radio galaxies. As
such, Cygnus A has played a fundamental role in the study of virtually
all aspects of extreme activity in galaxies. We present a review of jet
theory for powering the double-lobed radio emitting structures in
powerful radio galaxies, followed by a review of observations of Cygnus
A in the radio, optical, and X-ray relevant to testing various aspects
of jet theory. Issues addressed include: jet structure from pc- to
kpc-scales, jet stability, confinement, composition, and velocity, the
double shock structure for the jet terminus and the origin of multiple
radio hotspots, the nature of the filamentary structure in the radio
lobes, and the hydrodynamic evolution of the radio lobes within a dense
cluster atmosphere, including an analysis of pressure balance between
the various gaseous components. Also discussed are relativistic
particle acceleration and loss mechanisms in Cygnus A, as well as
magnetic field strengths and geometries both within the radio source,
and in the intracluster medium. We subsequently review the
classification, cluster membership, and the emission components of the
Cygnus A galaxy. The origin of the activity is discussed.
Concentrating on the nuclear regions of the galaxy, we review the
evidence for an obscured QSO, also given the constraints on the
orientation of the radio source axis with respect to the sky plane. We
present an overview of models of central engines in AGN and observations
of Cygnus A which may be relevant to testing such models. We conclude
with a brief section concerning the question of whether Cygnus A is
representative of powerful high redshift radio galaxies.
Received October 10, 1995 相似文献
9.
We consider the particular solutions of the evolutionary system of equations in elements that correspond to planar and spatial circular orbits of the singly averaged Hill problem. We analyze the stability of planar and spatial circular orbits to inclination and eccentricity, respectively. We construct the instability regions of both particular solutions in the plane of parameters of the problem. 相似文献
10.