全文获取类型
收费全文 | 45385篇 |
免费 | 643篇 |
国内免费 | 428篇 |
专业分类
测绘学 | 1044篇 |
大气科学 | 2829篇 |
地球物理 | 8709篇 |
地质学 | 16665篇 |
海洋学 | 4263篇 |
天文学 | 10822篇 |
综合类 | 89篇 |
自然地理 | 2035篇 |
出版年
2022年 | 330篇 |
2021年 | 591篇 |
2020年 | 579篇 |
2019年 | 702篇 |
2018年 | 1436篇 |
2017年 | 1340篇 |
2016年 | 1503篇 |
2015年 | 740篇 |
2014年 | 1369篇 |
2013年 | 2437篇 |
2012年 | 1581篇 |
2011年 | 1961篇 |
2010年 | 1876篇 |
2009年 | 2306篇 |
2008年 | 2028篇 |
2007年 | 2188篇 |
2006年 | 2002篇 |
2005年 | 1313篇 |
2004年 | 1295篇 |
2003年 | 1224篇 |
2002年 | 1204篇 |
2001年 | 1066篇 |
2000年 | 996篇 |
1999年 | 842篇 |
1998年 | 835篇 |
1997年 | 804篇 |
1996年 | 620篇 |
1995年 | 629篇 |
1994年 | 613篇 |
1993年 | 476篇 |
1992年 | 497篇 |
1991年 | 418篇 |
1990年 | 490篇 |
1989年 | 437篇 |
1988年 | 396篇 |
1987年 | 444篇 |
1986年 | 378篇 |
1985年 | 503篇 |
1984年 | 518篇 |
1983年 | 518篇 |
1982年 | 484篇 |
1981年 | 412篇 |
1980年 | 416篇 |
1979年 | 386篇 |
1978年 | 351篇 |
1977年 | 344篇 |
1976年 | 302篇 |
1975年 | 311篇 |
1974年 | 293篇 |
1973年 | 323篇 |
排序方式: 共有10000条查询结果,搜索用时 558 毫秒
1.
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
2.
3.
4.
The magnetic-field distribution outside a flat, infinitely conductive unbounded disk in the field of a point magnetic dipole is determined. A relationship is established between the problem of magnetic-field determination and the problem of the flow of an ideal incompressible fluid around an infinitely thin disk. 相似文献
5.
6.
7.
8.
Subglacial and subaqueous sediments deposited near the margin of a Late-glacial ice-dammed lake near Achnasheen, northern Scotland, are described and interpreted. The subglacial sediments consist of deformation tills and glacitectonites derived from pre-existing glaciolacustrine deposits, and the subaqueous sediments consist of ice-proximal outwash and sediment flow deposits, and distal turbidites. Sediment was delivered from the glacier to the lake by two main processes: (1) subglacial till deformation, which fed debris flows at the grounding line; and (2) meltwater transport, which fed sediment-gravity flows on prograding outwash fans. Beyond the ice-marginal environment, deposition was from turbidity currents, ice-rafting and settling of suspended sediments. The exposures support the conclusion that the presence of a subglacial deforming layer can exert an important influence on sedimentation at the grounding lines of calving glaciers. 相似文献
9.
T.-C. Jim Yeh 《水文研究》1992,6(4):369-395
This paper presents an introductory overview of recently developed stochastic theories for tackling spatial variability problems in predicting groundwater flow and solute transport. Advantages and limitations of the theories are discussed. Lastly, strategies based on the stochastic approaches to predict solute transport in aquifers are recommended. 相似文献
10.
Mallory S. E. Roberts Crystal L. Brogan Bryan M. Gaensler Jason W. T. Hessels C.-Y. Ng Roger W. Romani 《Astrophysics and Space Science》2005,297(1-4):93-100
A remarkable number of pulsar wind nebulae (PWN) are coincident with EGRET γ-ray sources. X-ray and radio imaging studies of unidentified EGRET sources have resulted in the discovery of at least six new pulsar wind nebulae (PWN). Stationary PWN (SPWN) appear to be
associated with steady EGRET sources with hard spectra, typical for γ-ray pulsars. Their toroidal morphologies can help determine the geometry of the
pulsar which is useful for constraining models of pulsed γ-ray emission. Rapidly moving PWN (RPWN) with more cometary morphologies
seem to be associated with variable EGRET sources in regions where the ambient medium is dense compared to what is typical for the ISM. 相似文献